summarize chemical design report

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timer Asked: Mar 24th, 2019

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I want to summarize this research, especially the second part ,

i want about 30-40 paper ?

PROCESS DESIGN PRACTICE 1 CHEM4007A Report 2 Acrylic acid By Student’s Name 1: Ahmed Said Al-Balushi SID: 151847 Student’s Name 2: Haitham Jumma Al Mashaikhi SID: 151865 Student’s Name 3: Mazin Ahmed Al mamari SID: 161054 A design project submitted to the faculty of engineering In partial fulfillment of the requirements for The process design course CHEM4007A&B Faculty of Engineering Department of Chemical Engineering Sohar University 2018-2019 PROCESS DESIGN PRACTICE CHEM4007A 2 Acknowledgment We would like to thank and appreciate the help and contribution of everyone who helped us to finish this project successfully. We would like to specially thank Dr. Youssef for his continuous help and gaudiness throughout the semester. PROCESS DESIGN PRACTICE CHEM4007A 3 Executive summary This report is going to discuss the process of producing acrylic acid through designing a detailed simulation of each equipment of the process. The process contains various equipment‟s starting from a gas compressor and going through a reactor, absorption columns, a distillation column, heat exchangers and pumps. Each equipment detailed design will be performed individually a long with the short cut design of the equipment. Besides that, a survey of each equipment is written showing how the equipment works and a discussion on its classifications. Finally, a comparison of the calculated data will be provided to show the percentage of error through comparing the simulation calculated data and the data obtained from references. PROCESS DESIGN PRACTICE CHEM4007A 4 Table of Contents Acknowledgment ............................................................................................................................ 2 Executive summary......................................................................................................................... 3 Table of Figures: ............................................................................................................................. 8 Chapter 1 ....................................................................................................................................... 11 1.1 Reactor: ................................................................................................................................... 11 1.1.1 Batch reactors: .................................................................................................................. 11 1.1.2 Continuous reactor: .......................................................................................................... 12 1.1.3 Types of continuous reactors: .......................................................................................... 13 1.1.4 Tubular reactors................................................................................................................ 13 1.1.5 Fixed bed reactor: ............................................................................................................. 14 1.1.6 Fluid bed reactors: ............................................................................................................ 15 1.1.7 Stirred tank reactor (CSTR): ............................................................................................ 16 1.1.8 Real application: ............................................................................................................... 18 1.2 Distillation column: ................................................................................................................ 19 1.2.1 Definition & process description: .................................................................................... 19 1.2.2 Uses of Distillation:.......................................................................................................... 20 Distillation of crude oil ............................................................................................................. 21 1.2.3 Flash distillation: .............................................................................................................. 26 1.2.4 Rectification: .................................................................................................................... 27 1.3 Heat Exchangers: .................................................................................................................... 31 1.3.1 Double pipe heat exchangers: .......................................................................................... 31 1.3.2 Shell and tube heat exchangers: ....................................................................................... 32 1.2.3 Plate type heat exchangers. .............................................................................................. 33 1.2.4 Air-cooled heat exchangers. ............................................................................................. 34 1.2.5 Theory of heat exchangers: .............................................................................................. 34 1.2.6 Reasons for using heat exchanger: ................................................................................... 36 1.2.7 Applications of heat exchanger: ....................................................................................... 36 1.2.8 Types of applications: ...................................................................................................... 36 1.4 Extraction ................................................................................................................................ 37 1.4.1 Definition: ........................................................................................................................ 37 1.4.2 Choice of solvent .............................................................................................................. 39 ............................................................................................................................................... 39 PROCESS DESIGN PRACTICE CHEM4007A 5 Phase Equilibria ..................................................................................................................... 41 1.4.3 Contactors: ....................................................................................................................... 41 1.4.4 Factors for contactors design: .......................................................................................... 44 Industrial extraction operations ............................................................................................. 49 1.5 Absorber:................................................................................................................................. 50 1.5.1: Definition: ....................................................................................................................... 50 1.5.2 TYPES OF ABSORPTION ............................................................................................. 51 Physical absorption: .................................................................................................................. 51 Chemical absorption:................................................................................................................. 51 1.6 flash ......................................................................................................................................... 54 1.7 Pumps:..................................................................................................................................... 55 1.7.1 Definition: ........................................................................................................................ 55 1.7.2 Positive displacement pumps ........................................................................................... 57 1.7.3 Kinetic pump: ................................................................................................................... 60 1.7.4 Centrifugal pump.............................................................................................................. 61 1.7.5 ENTRIFUGAL PUMPS................................................................................................... 61 1.7.6 CENTRIFUGAL FORCE ................................................................................................ 62 1.7.7 Regenerative pumps ......................................................................................................... 65 1.7.8 Electromagnetic pumps .................................................................................................... 66 1.8 Compressors:........................................................................................................................... 68 1.8.1 Definition: ........................................................................................................................ 68 1.8.2 Types of Compressors ...................................................................................................... 68 1.8.3 Principle of Compressors ................................................................................................. 70 1.8.4 Applications of Compressors ........................................................................................... 71 Chapter 2 ....................................................................................................................................... 72 2.1 Reactor design. ........................................................................................................................ 72 2.1.1 Reaction and reaction kinetic: .......................................................................................... 72 2.1.2 HYSYS simulation of reactor .......................................................................................... 73 2.1.3 Simulation and results from shortcut: .............................................................................. 75 2.1.4 Reactor graphs. ................................................................................................................. 77 2.1.4.1 Molar flow vs Reactor length. ....................................................................................... 77 2.1.4.2 Temperature effects vs conversion (Rxn1 and Rxn2) ................................................... 78 2.1.4.3 Temperature VS total conversion:................................................................................. 79 2.1.4.4 PFR volume VS conversion: ......................................................................................... 80 PROCESS DESIGN PRACTICE CHEM4007A 6 2.1.4.5 PFR volume VS conversion (Rxn1 and Rxn2): ............................................................ 81 2.1.4.6 PFR volume VS conversion (Rxn1):............................................................................. 82 2.2 Distillation: ............................................................................................................................. 83 2.2.1 (T-303) simulation: .......................................................................................................... 83 2.2.2 Comparison: ..................................................................................................................... 84 2.2.3 Distillation graphs: ........................................................................................................... 86 2.2.3.1 Temperature vs Tray Position from top. ....................................................................... 86 2.2.3.2 Pressure vs Tray position from top. .............................................................................. 87 2.2.3.3 Pressure vs Tray position from top. .............................................................................. 88 2.2.3.4 Pressure vs Tray position from top. .............................................................................. 89 Design for distillation tower (T-303): ....................................................................................... 90 2.3 absorption tower...................................................................................................................... 91 2.3.1 Absorption tower (T-301). ............................................................................................... 91 2.3.1.1 Simulation results for absorber (T-301): ....................................................................... 91 2.3.1.2 Comparison for (T-301) results. .................................................................................... 92 2.3.1.3 T-301 graphs: ............................................................................................................... 94 2.3.1.3.1 Temperature vs tray position from top T-301. ........................................................... 94 2.3.1.3.2 Pressure vs tray position from top T-301. .................................................................. 95 2.3.1.3.3 Flow vs tray position from top T-301. ....................................................................... 96 2.3.1.3.4 Column properties vs tray position from top T-301. .................................................. 97 2.3.1.3.5 Composition vs tray position from top. ...................................................................... 98 2.3.1.3.6 K-values vs tray position from top. ............................................................................ 99 2.3.2 Absorption tower (T-302): ............................................................................................. 101 2.3.2.2 Simulation results comparison (T-301): ...................................................................... 102 Discussion for tower T-302:.................................................................................................... 103 2.3.2.3 T-301 Graphs: ............................................................................................................. 104 2.3.2.3.1 Temperature vs Tray position from top (T-301): ..................................................... 104 2.3.2.3.2 Pressure vs Tray position from top (T-301): ............................................................ 105 2.3.2.3.3 Composition vs Tray position from top (T-301): ..................................................... 106 2.4 Pumps simulations: ............................................................................................................... 107 2.4.1 Simulation for pump (P-301 A/B) molten salt: .............................................................. 107 2.4.1.1 Electric motor vs S for pump (P-304 A/B) molten salt:.............................................. 108 2.4.2 Simulation for pump (P-302 A/B):................................................................................. 109 2.4.3 Simulation for pump (P-303 A/B):................................................................................. 110 PROCESS DESIGN PRACTICE CHEM4007A 7 2.4.4 Simulation for pump (P-304 A/B):................................................................................. 111 2.5 Compressor: .......................................................................................................................... 112 2.6 Heat exchangers: ................................................................................................................... 113 2.6.2 E-302 .............................................................................................................................. 116 2.6.3 E-303 .............................................................................................................................. 118 2.6.3.1 Heat Exchanger (E-303) specification sheet: .............................................................. 120 2.6.3.2 Layout parameters ( Pitch , passes) ............................................................................. 122 2.6.3.3 Discussion E-303 results: ............................................................................................ 122 2.6.3.3 Cold and hot stream temperatures: .............................................................................. 123 2.6.3.4 Heat flow vs Temperature E-303. ............................................................................... 124 2.6.3.5 Temperature vs pressure for tube side E-303 .............................................................. 125 2.6.3.6 Temperature vs pressure for shell side E-303: ............................................................ 126 2.6.4 E-304 .............................................................................................................................. 128 2.6.5 E-305 .............................................................................................................................. 130 Chapter 3 ..................................................................................................................................... 132 Conclusion .................................................................................................................................. 132 References: .................................................................................................................................. 133 PROCESS DESIGN PRACTICE CHEM4007A 8 Table of Figures: Figure 1 Batch ............................................................................................................................... 11 Figure 2 Continuous reactor.......................................................................................................... 12 Figure 3 Fixed bed reactor ............................................................................................................ 14 Figure 4 Fluid bed reactors ........................................................................................................... 15 Figure 5 Stirred tank reactor (CSTR): .......................................................................................... 16 Figure 6 Stirred tank reactor (CSTR) 2......................................................................................... 17 Figure 7 Chemical engineering schematic of a continuous fractionating column ........................ 20 Figure 8 Trays in a fractionating column. ..................................................................................... 22 Figure 9 Valve trays ...................................................................................................................... 23 Figure 10 Vapor-liquid equilibrium conditions (VLE) ................................................................. 24 Figure 11 Flash distillation ........................................................................................................... 26 Figure 12: Rectification ................................................................................................................ 28 Figure 13 : Double pipe heat exchangers ...................................................................................... 31 Figure 14: Shell and tube heat exchangers ................................................................................... 32 Figure 15: Plate type heat exchangers .......................................................................................... 33 Figure 16: Air-cooled heat exchangers ......................................................................................... 34 Figure 17: parallel flow, counter flow and cross flow .................................................................. 35 Figure 18: Extraction .................................................................................................................... 37 Figure 19: Extraction 2 ................................................................................................................. 39 Figure 20: Extraction of solute C from A using solvents B and B' .............................................. 40 Figure 21: Contactor arrangements ............................................................................................... 42 Figure 22: absorber ....................................................................................................................... 50 Figure 23: diffusivity .................................................................................................................... 52 Figure 24: Flash ............................................................................................................................ 54 Figure 25: Pump ............................................................................................................................ 56 Figure 26: Positive displacement pumps ...................................................................................... 57 Figure 27: ROTARY pumps ......................................................................................................... 58 Figure 28: Kinetic pump ............................................................................................................... 60 Figure 29: Centrifugal pump ......................................................................................................... 61 Figure 30: Regenerative pumps .................................................................................................... 65 Figure 31: Electromagnetic pumps ............................................................................................... 66 Figure 32: (Piston Compressor) .................................................................................................... 69 Figure 33: Centrifugal Compressor .............................................................................................. 69 Figure 34: Rotary Screw Compressor-Positive Displacement...................................................... 70 Figure 35: Kinetics ........................................................................................................................ 72 Figure 36: Plug flow reactor ......................................................................................................... 73 Figure 37: Molar flow vs Reactor length ...................................................................................... 77 Figure 38: Temperature effects vs conversion (Rxn1 and Rxn2) ................................................. 78 Figure 39: Temperature VS total conversion ................................................................................ 79 Figure 40: PFR volume VS conversion ........................................................................................ 80 Figure 41: PFR volume VS conversion (Rxn1 and Rxn2) ........................................................... 81 Figure 42: PFR volume VS conversion (Rxn1) ............................................................................ 82 Figure 43: (T-303) simulation ....................................................................................................... 83 Figure 44: Temperature vs Tray Position from top ...................................................................... 86 Figure 45: Pressure vs Tray position from top.............................................................................. 87 PROCESS DESIGN PRACTICE CHEM4007A 9 Figure 46: Pressure vs Tray position from top.............................................................................. 88 Figure 47: Pressure vs Tray position from top.............................................................................. 89 Figure 48: Design for distillation tower (T-303) .......................................................................... 90 Figure 49: Simulation results for absorber (T-301) ...................................................................... 91 Figure 50: Temperature vs tray position from top T-301. ............................................................ 94 Figure 51: Pressure vs tray position from top T-301. ................................................................... 95 Figure 52: Flow vs tray position from top T-301. ........................................................................ 96 Figure 53: Column properties vs tray position from top T-301 .................................................... 97 Figure 54:Composition vs tray position from top ......................................................................... 98 Figure 55:K-values vs tray position from top ............................................................................... 99 Figure 56:Component Ratio vs tray position from top ............................................................... 100 Figure 57: SIMULATION results for absorber (T-301) ............................................................. 101 Figure 58:Temperature vs Tray position from top (T-301) ........................................................ 104 Figure 59:Pressure vs Tray position from top (T-301) ............................................................... 105 Figure 60: Composition vs Tray position from top (T-301) ....................................................... 106 Figure 61:Simulation for pump (P-301 A/B) molten salt ........................................................... 107 Figure 62:Electric motor vs S for pump (P-304 A/B) molten salt .............................................. 108 Figure 63:Simulation for pump (P-302 A/B) .............................................................................. 109 Figure 64:Simulation for pump (P-303 A/B) .............................................................................. 110 Figure 65:Simulation for pump (P-304 A/B) .............................................................................. 111 Figure 66: COMPRESSOR......................................................................................................... 112 Figure 67:E-301 simulation ........................................................................................................ 113 Figure 68:E-302 SIMULATION ................................................................................................ 116 Figure 69:E-303 simulation ........................................................................................................ 118 Figure 70: Heat exchanger specification sheet ........................................................................... 120 Figure 71: layout parameters ...................................................................................................... 122 Figure 72: cold and hot stream temperature profile E-303 ......................................................... 123 Figure 73: Heat flow vs Temperature E-303 .............................................................................. 124 Figure 74: Temperature vs pressure for tube side E-303 ............................................................ 125 Figure 75: Temperature vs pressure for shell side ...................................................................... 126 Figure 76:E-304 simulation ........................................................................................................ 128 Figure 77:E-305 simulation ........................................................................................................ 130 Figure 78:E-305 design information ........................................................................................... 131 PROCESS DESIGN PRACTICE CHEM4007A 10 Table of tables: Table 1 PFR Dimensions .............................................................................................................. 74 Table 2: Comparison for the effluent from the reactor ................................................................. 74 Table 3: Simulation and results from shortcut .............................................................................. 75 Table 4: Comparison for shortcut Reactor .................................................................................... 76 Table 5: Parameters comparisons for distillation.......................................................................... 84 Table 6: Stream table comparison for distillation ......................................................................... 84 Table 7: Stream number 18 FOR distillation ................................................................................ 85 Table 8: Comparison for (T-301) results stream 9........................................................................ 92 Table 9: Comparison for (T-301) results stream 9A ..................................................................... 93 Table 10: SIMULATION results comparison (T-301) ............................................................... 102 Table 11: STREAM number (11) ............................................................................................... 102 Table 12:Stream number 7 .......................................................................................................... 103 Table 13: COMPRRESOR stream information .......................................................................... 112 Table 14: E-301 design information ........................................................................................... 115 Table 15:E-302 design information ............................................................................................ 117 Table 16:E-303 design information ............................................................................................ 119 Table 17 Discussion E-303 results .............................................................................................. 122 Table 18:E-304 design information ............................................................................................ 129 PROCESS DESIGN PRACTICE CHEM4007A 11 Chapter 1 1.1 Reactor: A chemical reactor is an enclosed volume in which a chemical reaction takes place. In chemical engineering, it is generally understood to be a process vessel used to carry out a chemical reaction, which is one of the classic unit operations in chemical process analysis. The design of a chemical reactor deals with multiple aspects of chemical engineering. Chemical engineers design reactors to maximize net present value for the given reaction. Designers ensure that the reaction proceeds with the highest efficiency towards the desired output product, producing the highest yield of product while requiring the least amount of money to purchase and operate. Normal operating expenses include energy input, energy removal, raw material costs, labor, etc. Energy changes can come in the form of heating or cooling, pumping to increase pressure, frictional pressure loss or agitation. Chemical reaction engineering is the branch of chemical engineering, which deals with chemical reactors and their design, especially by application of chemical kinetics to industrial systems. 1.1.1 Batch reactors: Batch reactor: are used for most of the reactions carried out in a laboratory. The reactants are placed in a test-tube, flask or beaker. They are mixed together, often heated for the reaction to take place and are then cooled. The products are poured out and, if necessary, purified. This procedure is also carried out in industry, the key difference being one of size of reactor and the quantities of reactants. The following figure shows the system of the batch reactor. (2) FIGURE 1 BATCH PROCESS DESIGN PRACTICE CHEM4007A 12 1.1.2 Continuous reactor: An alternative to a batch process is to feed the reactants continuously into the reactor at one point, allow the reaction to take place and withdraw the products at another point. There must be an equal flow rate of reactants and products. While continuous reactors are rarely used in the laboratory, a water softener can beregarded as an example of a continuous process. Hard water from the mains is passed through a tube containing an ion-exchange resin. Reaction occurs down the tube and soft water pours out at the exit. Moreover, ontinuous reactors are normally installed when large quantities of a chemical are being produced. It is important that the reactor can operate for several months without a shutdown. The following shows the continues reactor. FIGURE 2 CONTINUOUS REACTOR The residence time in the reactor is controlled by the feed rate of reactants to the reactor. For example, if a reactor has a volume of 20 m3 and the feed rate of reactants is 40 m3 h-1 the residence time is 20 m3 /40 m3 h-1 = 0.5 h. It is simple to control accurately the flow rate of reactants. The volume is fixed and therefore the residence time in the reactor is well controlled. The product tends to be of a more consistent quality from a continuous reactor because the reaction parameters (e.g. residence time, temperature and pressure) are better controlled than in batch operations. They also produce less waste and require much lower storage of both raw materials and products resulting in a more efficient operation. Capital costs per tonne of product produced are consequently lower. The main disadvantage is their lack of flexibility as once the reactor has been built it is only in rare cases that it can be used to perform a different chemical reaction. PROCESS DESIGN PRACTICE CHEM4007A 13 1.1.3 Types of continuous reactors: 1.1.4 Tubular reactors In a tubular reactor, fluids (gases and/or liquids) flow through it at high velocities. As the reactants flow, for example along a heated pipe, they are converted to products (Figure 4). At these high velocities, the products are unable to diffuse back and there is little or no back mixing. The conditions are referred to as plug flow. This reduces the occurrence of side reactions and increases the yield of the desired product. With a constant flow rate, the conditions at any one point remain constant with time and changes in time of the reaction are measured in terms of the position along the length of the tube. The reaction rate is faster at the pipe inlet because the concentration of reactants is at its highest and the reaction rate reduces as the reactants flow through the pipe due to the decrease in concentration of the reactant. Tubular reactors are used, for example, in the steam cracking of ethane, propane and butane and naphtha to produce alkenes. PROCESS DESIGN PRACTICE CHEM4007A 14 1.1.5 Fixed bed reactor: A heterogeneous catalyst is used frequently in industry where gases flow through a solid catalyst (which is often in the form of small pellets to increase the surface area). It is often described as a fixed bed of catalyst as shown in the reactor. Among the examples of their use are the manufacture of sulfuric acid (the Contact Process, with vanadium(V) oxide as catalyst), the manufacture of nitric acid and the manufacture of ammonia (the Haber Process, with iron as the catalyst). A further example of a fixed bed reactor is in catalytic reforming of naphtha to produce branched chain alkanes, cycloalkanes and aromatic hydrocarbons using usually platinum or a platinumrhenium alloy on an alumina support. FIGURE 3 FIXED BED REACTOR PROCESS DESIGN PRACTICE CHEM4007A 15 1.1.6 Fluid bed reactors: A fluid bed reactor is sometimes used whereby the catalyst particles, which are very fine, sit on a distributor plate. When the gaseous reactants pass through the distributor plate, the particles are carried with the gases forming a fluid. This ensures very good mixing of the reactants with the catalyst, with very high contact between the gaseous molecules and the catalyst and a good heat transfer. This results in a rapid reaction and a uniform mixture, reducing the variability of the process conditions. One example of the use of fluid bed reactors is in the oxychlorination of ethene to chloroethene (vinyl chloride), the feedstock for the polymer poly(chloromethane) (PVC). The catalyst is copper(II) chloride and potassium chloride deposited on the surface of alumina. This support is so fine, it acts as a fluid when gases pass through it. The following scheme shows the fluid bed reactor. On the left hand side, the particles are at rest. On the right hand side, the particles are now acting as a fluid, as the gaseous reactants pass through the solid. FIGURE 4 FLUID BED REACTORS PROCESS DESIGN PRACTICE CHEM4007A 16 1.1.7 Stirred tank reactor (CSTR): In a CSTR, one or more reactants, for example in solution or as a slurry, are introduced into a reactor equipped with an impeller (stirrer) and the products are removed continuously. The impeller stirs the reagents vigorously to ensure good mixing so that there is a uniform composition throughout. The composition at the outlet is the same as in the bulk in the reactor. These are exactly the opposite conditions to those in a tubular flow reactor where there is virtually no mixing of the reactants and the products. A steady state must be reached where the flow rate into the reactor equals the flow rate out, for otherwise the tank would empty or overflow. The residence time is calculated by dividing the volume of the tank by the average volumetric flow rate. For example, if the flow of reactants is 10 m3 h-1 and the tank volume is 1 m3, the residence time is 1/10 h, i.e. 6 minutes. FIGURE 5 STIRRED TANK REACTOR (CSTR): PROCESS DESIGN PRACTICE CHEM4007A 17 A CSTR reactor is used, for example in the production of the amide intermediate formed in the process to produce methyl 2-methylpropenoate. Sulfuric acid and 2-hydroxy-2methylpropanonitrile are fed into the tank at a temperature of 400 K. The heat generated by the reaction is removed by cooling water fed through coils and the residence time is about 15 minutes. A variation of the CSTR is the loop reactor, which is relatively simple and cheap to construct (Figure 11). In the diagram only one loop is shown. However, the residence time in the reactor is adjusted by altering the length or number of the loops in the reactor. oop reactors are used, for example, in the manufacture of poly(ethene) and the manufacture of poly(propene). Ethene (or propene) and the catalyst are mixed, under pressure, with a diluent, usually a hydrocarbon. A slurry is produced which is heated and circulated around the loops. Particles of the polymer gather at the bottom of one of the loop legs and, with some hydrocarbon diluent, are continuously released from the system. The diluent evaporates, leaving the solid polymer, and is then cooled to reform a liquid and passed back into the loop system, thus recirculating the hydrocarbon. FIGURE 6 STIRRED TANK REACTOR (CSTR) 2 PROCESS DESIGN PRACTICE CHEM4007A 18 1.1.8 Real application: Batch reactors are often used in the process industry. Batch reactors also have many laboratory applications, such as small scale production and inducing fermentation for beverage products. They also have many uses in medical production. Batch reactors are generally considered expensive to run, as well as variable product reliability. They are also used for experiments of reaction kinetics, volatiles and thermodynamics. Batch reactors are also highly used in waste water treatment. They are effective in reducing BOD (biological oxygen demand) of influent untreated water. (5) . However, Continuous stirred-tank reactors are most commonly used in industrial processing, primarily in homogeneous liquid-phase flow reactions, where constant agitation is required. They may be used by themselves, in series, or in a battery. CSTRs are also used in the pharmaceutical industry as a loop reactor. Fermenters are also an application of CSTR s that involve the use of a biological catalyst to generate products. In a fermenter, microbes catalyze a reaction that breaks down much larger molecules into smaller molecules such as ethanol, methanol, or other hydrocarbons. Vapor product can be removed from the top of a unit without separation, or liquid product can be removed from the bottom, filtering out and recycling the microbial media. (6). Plug flow reactors have a wide variety of applications in either gas or liquid phase systems. Common industrial uses of tubular reactors are in gasoline production, oil cracking, synthesis of ammonia from its elements, and the oxidation of sulfur dioxide to sulfur trioxide. Pictured below is a tubular reactor used in research on the oxidation of nitrogen compounds. It reaches temperatures of 800 - 1100°C. Tubular reactors can also be used as bioreactors or for small scale production. The tubular bioreactor shown below is used for the production of algae. The algae are then compressed and dried and can be used as feed for a biodiesel reactor. In acrylic acid production, the plug flow reactor used for the oxidation of propylene. The flowing sections shows the design for the reactor in this process. For the shortcut, a conversion reactor is used and for the full design, the plug flow reactor is used. PROCESS DESIGN PRACTICE CHEM4007A 19 1.2 Distillation column: 1.2.1 Definition & process description: Distillation is a widely used method for separating mixtures based on differences in the conditions required to change the phase of components of the mixture. To separate a mixture of liquids, the liquid can be heated to force components, which have different boiling points, into the gas phase. It is the most popular and important separation method in the petroleum industries for purification of final products. Distillation columns are made up of several components, each of which is used either to transfer heat energy or to enhance mass transfer. Distillation is a process of separating various components of a liquid solution by heating the liquid to forms its vapors and then condensing the vapors to form the liquid. A typical distillation column contains a vertical column where trays or plates are used to enhance the component separations, a reboiler to provide heat for the necessary vaporization from the bottom of the column, a condenser to cool and condense the vapor from the top of the column, and a reflux drum to hold the condensed vapor so that liquid reflux can be recycled back from the top of the column. Distillation is done by vaporizing a definite fraction of a liquid mixture in such way that the evolved vapor is in equilibrium with the residual liquid. The equilibrium vapor is then separated from the equilibrium residual liquid by condensing the vapor. PROCESS DESIGN PRACTICE CHEM4007A 20 FIGURE 7 CHEMICAL ENGINEERING SCHEMATIC OF A CONTINUOUS FRACTIONATING COLUMN 1.2.2 Uses of Distillation: Distillation is used for many commercial processes, such as the production of gasoline, distilled water, xylene, alcohol, paraffin, kerosene, and many other liquids. Gas may be liquefied and separate. For example: nitrogen, oxygen, and argon are distilled from air. Scientific Uses One practical use of distillation is in the laboratory. While the results of this type of distillation may not find their way directly into our homes, the process is used regularly in chemical and pharmaceutical research, quality assurance testing for many consumer products and law enforcement forensics. Water Purification Water from natural sources contains a variety of minerals and other impurities, many of which can be removed by distillation. Distilled water is commonly used in situations where the presence of minerals might reduce the effectiveness of certain equipment, such as in steam irons or cigar humidors. Some people drink distilled water because they like the taste or want to avoid the minerals found in tap water. Parents will often use distilled water when preparing baby formula for their infants. Desalination plants also use distillation to turn seawater into drinking water PROCESS DESIGN PRACTICE CHEM4007A 21 Alcoholic Beverages Distillation is used to produce a variety of alcoholic beverages, such as whiskey, rum and brandy. When fruit and plant materials ferment, a dilute version of ethyl alcohol is produced. Distilling the fermented material purifies and concentrates the ethanol. A variety of other components, such as water, esters and other types of alcohol, are also collected during the distillation process, which accounts for the unique flavor of each alcoholic spirit. Petroleum Products A number of products can be produced from crude oil. Because each of these products has a unique boiling point, a process known as fractional distillation is used to refine oil into separate materials. These include gasoline, diesel fuel, lubricating oil, fuel oil, paraffin wax and petrochemicals. Perfume One of the earliest uses of distilling was to make perfume, which began around 3500 B.C. The aroma from various plants and herbs is contained in what are known as essential oils, which can be extracted through distillation. However, many aromatic plants tend to decompose at high temperatures so separation by normal distillation isn‟t practical. In those instances, steam is passed through the plant material to draw out the essential oils without burning the mixture. The steam is then captured and condensed just as in normal distillation. Food Flavorings Steam distillation is also used to create natural food flavorings. The most common are citrus oils and liquid extracts of various herbs and spices. Distillation of crude oil Crude oil is a mixture of many hundreds of liquid hydrocarbons. Dissolved in it are many other hydrocarbons some of which are solids and some gases (the lower members of the alkane family, predominantly methane and ethane but often with some propane and butane). There may also be some hydrocarbon gases trapped above the oil, as for example in some of the oil fields in the North Sea. PROCESS DESIGN PRACTICE CHEM4007A 22 In the refineries the oil is distilled into liquid fractions with different boiling point ranges which are then further processed. FIGURE 8 TRAYS IN A FRACTIONATING COLUMN. The crude oil is heated in a furnace (ca 650 K) and the resulting mixture fed as a vapour into a fractionating tower which can have a height of 25-100 m, handling volumes of over 40 000 m3 a day. The column may contain 40-50 steel „sieve trays‟ which fit horizontally across the column and are designed to ensure there is intimate mixing between the descending liquid, formed by condensation, and the rising vapour. To effect this close contact, the trays have holes in them („the sieve‟) through which the vapour flows up into the liquid collecting on the trays (Figure 2). PROCESS DESIGN PRACTICE CHEM4007A FIGURE 9 VALVE TRAYS Vapor-liquid equilibrium conditions (VLE) Basic notions and rules: 1. Pure component vapor pressure (p0) The Antoine equation describes the relation between vapor pressure and temperature for pure components. It is derived from the Clausius-Clapeyron equation. 23 PROCESS DESIGN PRACTICE CHEM4007A FIGURE 10 VAPOR-LIQUID EQUILIBRIUM CONDITIONS (VLE) Numerical example a) Calculate the vapour pressure of water at 25⁰ C. b) Determine the boiling point of water for a pressure of 994 mbar Antoine constants:A = 8.07131 B = 1730.63 C = 233.426 1 atm = 760 mmHg = 1013 mbar = 1.013·105 Pa 1 mmHg = 133.28 Pa 24 PROCESS DESIGN PRACTICE CHEM4007A Dalton‟s Law It is valid for ideal vapour phase (mixture of ideal (perfect) gases). Ideal mixture: interactions between the same molecules (e.g. i and i) are equal with those between the different (e. g. i and j) molecules. The mixture of the members of the same homologous series (e.g. n – hexane – n – heptane, benzene – toluene) can be considered ideal even in the liquid phase. At atmospheric distillations the vapour phase is usually ideal (if there is no association in it) since the molecules are far from each other. 3- Raoult‟s Law For ideal liquid phase. 25 PROCESS DESIGN PRACTICE CHEM4007A 26 where xi mole fraction of component i in the liquid phase The liquid phase is ideal less frequently than the vapour phase since the molecules are much closer to each other therefore the interactions (attraction, repulsion (repelling)) are much stronger. Distillation Methods 1. Flash Distillation 2. Rectification 3. Batch Distillation 1.2.3 Flash distillation: Flash distillation is a special operation within distillation, where a liquid mixture is heated up and fed – with constant flowrate – into a distillation equipment. The resulting vapor and liquid phases enter a phase separator – an equilibrium chamber – and are drained separately. During the operation, the total pressure and temperature of the system, as well as the compositions of the two phases in equilibrium remain constant over time. For binary mixture (NC = 2) FIGURE 11 FLASH DISTILLATION a: pump b:heater c:valve d:separator PROCESS DESIGN PRACTICE CHEM4007A F, V, L : molar flow rates (mol/s) xF, y, x : mole fraction of the more volatile component in the feed, vapour and liquid respectively The vapour and liquid leaving the drum are in equilibrium y = f(x) Total material Balance (TMB) “ in = out “ F=V+L Component Material balance (CMB) FXF =Vy+Lx Y= - 1.2.4 Rectification: 27 PROCESS DESIGN PRACTICE CHEM4007A 28 Rectification is an application of distillation and its uses include fractionation of crude oil. If the distillate obtained during distillation is distilled again, a new distillate is obtained with an even higher concentration of volatile components. As the procedure is repeated, the concentration of volatile components in the distillate increases on each occasion. In practice, this multi-stage distillation process is carried out in the form of countercurrent distillation (rectification) in a column. The liquid mixture to be separated (feed) is fed to the bottom of the column, where it is brought to boiling point. The vapour produced moves upwards inside the column, exits it at the top and is condensed. Part of the condensate is carried away as top product. The remainder flows back into the column and moves downwards as liquid opposite phase. FIGURE 12: RECTIFICATION 3 main parts: - Column with plates - Total Condenser - Partial Reboiler Total Condenser: The top vapour is totally condensed, the condensate is divided into distillate (product withdrawn) and reflux sent back to the top of the column. The condenser is usually cooled with cooling water. Partial Reboiler: The liquid arriving from the bottom of the column is partially vaporized in the reboiler, the vapour is sent back to the column, the liquid is withdrawn as product (bottoms). The reboiler is heated usually with (water) steam. Additional parts: Accumulator (for storing the condensate, optional), reflux pump (optional), product coolers (for cooling the top (overhead) and bottoms products with cooling water and the cold feed), trap (for retaining that part of the water steam which has not been condensed and ensuring the overpressure of the steam), two product tanks Total Material Balance (TMB): V=L+D Component Material Balance (CMB): PROCESS DESIGN PRACTICE CHEM4007A This is the operating line equation for the RS straight line in the y – x diagram 29 PROCESS DESIGN PRACTICE CHEM4007A The operating lines gives the relation between the composition of the vapour and liquid streams meeting between two neighbour stages. yn is in equilibrium with xn (the streams leaving the same stages are in Equilibrium). 30 PROCESS DESIGN PRACTICE CHEM4007A 31 1.3 Heat Exchangers: A heat exchanger is a heat transfer device which exchanges heat energy between two process streams. However, generally the term also includes coolers, condensers, and heaters that utilize a utility stream to cool or heat a process stream. Double pipe, shell and tube, plate type, compact (plate-fin), and spiral heat exchangers are the common types of heat exchangers. The followings are the important types of heat exchangers: 1.3.1 Double pipe heat exchangers: In its simplest design, a double pipe heat exchanger consists of two concentric pipes. One fluid flows in the inner pipe while the other fluid flows outside the inner pipe, in the annular space between the two pipes. The two fluids usually flow in a countercurrent manner and true countercurrent flow advantages may be obtained. Double pipe heat exchangers are usually formed in a hairpin fashion and in this form they are called as hairpin heat exchangers. Double pipe heat exchangers are easy to clean and easy to manufacture and they are generally of low cost especially when surface area requirements are low. They offer low surface area density and there are many leakage points. When relatively large surface area is required, banks of these hairpins are required. A series-parallel arrangement may be suggested to avoid the excessive pressure drop. FIGURE 13 : DOUBLE PIPE HEAT EXCHANGERS PROCESS DESIGN PRACTICE CHEM4007A 32 1.3.2 Shell and tube heat exchangers: The most kind of the heat exchangers used in chemical and petrochemical industry is the shell and tube heat exchanger. It consists of a cylindrical shell contained within which a stack of tubes called as tube bundle. One of the fluids flows in the body of the shell and 0exchanges heat with the fluid flowing inside the tubes. In most designs, segmental baffles are used to increase the turbulence in the shell side fluid and therefore increase the shell side heat transfer coefficient. One or more tube side passes or shell side passes can be arranged and U-shaped tubes may also be employed. A differential expansion between the shell and tube bundle may be accommodated by designing a floating head heat exchanger or incorporating an expansion joint in the body of the shell. A variety of shell and tube heat exchanger designs may be observed in the TEMA classification. For the minimum cost, standard components are used in the design. If the fluid is corrosive, fouling, hot, or at high pressure it should be placed on the tube side. It contains Ushaped tubes so is the name. Such an exchanger consists only of one tube sheet. The U-bend tubes are difficult to clean and replace and therefore the exchanger is employed for clean fluids. As one end of the U-tube bundle is not fixed and free to move in the shell, this exchanger has no expansion problems and the tube bundle is easy to drag out (pull through assembly) of the shell. FIGURE 14: SHELL AND TUBE HEAT EXCHANGERS PROCESS DESIGN PRACTICE CHEM4007A 33 1.2.3 Plate type heat exchangers. A type of indirect heat exchanger that consists a series of thin welded or gasketted plates. The hot and cold fluids flow in alternate plate passages and heat is transferred through the wall of the metal plates. The metal plates are corrugated in order to enhance the heat transfer coefficient and the heat transfer surface. Also, corrugations can provide mechanical strength to the plate geometry. The exchanger has high heat transfer coefficients and high heat transfer surface to volume ratio. FIGURE 15: PLATE TYPE HEAT EXCHANGERS PROCESS DESIGN PRACTICE CHEM4007A 34 1.2.4 Air-cooled heat exchangers. Called as fin-fan air cooler or simply air cooler. In an air cooled heat exchanger, ambient air is passed over a bank of tubes while the hot process fluid flows inside the horizontal tubes in cross flow to the flow of the air. A forced draft or induced draft fan is required to drive the coolant air and to increase the air velocity over the tube which increases the air side heat transfer coefficient. Due to low heat transfer coefficient associated with air side, traverse fins are used on the outside surface (air side) of the tubes to enhance the heat transfer area. FIGURE 16: AIR-COOLED HEAT EXCHANGERS 1.2.5 Theory of heat exchangers: PROCESS DESIGN PRACTICE CHEM4007A 35 To reach equilibrium heat always flow from points of higher temperature to points of lower temperature as the natural laws of physics state. Heat exchangers are used to decrease or increase the temperature of a substance by using another substance which have a higher or lower temperature. There are two main types of heat exchangers which are direct heat exchanger and indirect heat exchangers where they differ from each other in the type of contact surface between the two fluids. Indirect heat exchangers uses a plate or barrier between the two substances in order to keep them from mixing. On the other hand, direct heat exchangers both substances are brought together with no barrier between them. Substances in direct heat exchangers should be insoluble in each other to avoid them mixing or the used fluid must undergo a phase change. Heat exchangers are typically classified according to flow arrangement (parallel flow, counter flow and cross flow) and type of construction. FIGURE 17: PARALLEL FLOW, COUNTER FLOW AND CROSS FLOW PROCESS DESIGN PRACTICE CHEM4007A 36 1.2.6 Reasons for using heat exchanger: A basic of heat exchanger is a component that allows the transfer of heat from one fluid (liquid org as) to another fluid. The question now is why heat exchanger is important and the reason to use it. Actually the reasons for heat exchanger are directly related to heat transfer Reasons .so there are so many reasons for heat transfer and there are some of them: 1) 2) 3) 4) 5) To heat a cooler fluid by means of a hotter fluid. To reduce the temperature of a hot fluid by means of a cooler fluid. To boil a liquid by using a hotter fluid. To condense a gaseous fluid by means of a cooler fluid. To boil a liquid while condensing a hotter gaseous fluid Heat exchangers can have different size and shape depending on the application. 1.2.7 Applications of heat exchanger: It‟s been notice that the heat exchanger is one of the most common pieces in industry. Therefore it takes the most engineering attentions. Heat exchanger exist in most chemical, mechanical and electrical system. Also some of the more common applications founding in chemical plant, power stations, chemical and petrochemical processing plants .Also building heating and air conditioning, refrigeration systems, automotive industry, marine and space vehicles and electronic systems. 1.2.8 Types of applications: There are so many types of applications of heat exchanger and there are some of them: Evaporator: it‟s an operation happen when Fluid approaches evaporator as a high pressure liquid near room temperature since the Heat exchanger made from a long metal pipe A constriction so it will reduces the fluid‟s pressure then the Fluid enters evaporator as a low pressure liquid near room temperature the Working fluid evaporates in the evaporator the fluid will become much so the gas will Break bonds takes energy so the Thermal energy Heat flows from room air into colder fluid the fluid will leave the evaporator as a low pressure gas near room temperature Heat has left the room. Condenser Heat exchanger: Condenser Heat exchanger made from long metal pipe. Fluid will enter the condenser as a hot and high pressure gas .then the Heat will flow from fluid to outside air the working Fluid will condense in the condenser so the Fluid becomes hotter liquid More heat will flow from fluid to outside air the fluid leaving the condenser in high pressure liquid near room temperature Heat has reached the outside air. PROCESS DESIGN PRACTICE CHEM4007A 37 1.4 Extraction 1.4.1 Definition: Liquid-liquid (or solvent) extraction is a countercurrent separation process for isolating the constituents of a liquid mixture. In its simplest form, this involves the extraction of a solute from a binary solution by bringing it into contact with a second immiscible solvent in which the solute is soluble. In practical terms, however, many solutes may be present in the initial solution and die extracting ‘solvent’ may be a mixture of solvents designed to be selective for one or more solutes, depending upon their chemical type. FIGURE 18: EXTRACTION Solvent extraction is an old, established process and together with distillation constitute the two most important industrial separation procedures. The first commercially-successful liquid-liquid extraction operation was developed for the petroleum industry in 1909 when Edeleanu’s process was employed for the removal of aromatic hydrocarbons from kerosene, using liquid sulfur dioxide as solvent. Since then many other processes have been developed by the petroleum, chemical, metallurgical, nuclear, pharmaceutical and food processing industries. Whereas distillation affects a separation by utilizing the differing volatilities of the components of a mixture, liquid-liquid extraction makes use of the different extent to which the components can partition into a second immiscible solvent. This property is frequently characteristic of the chemical type so that entire classes of compounds may be extracted if desired. The petroleum PROCESS DESIGN PRACTICE CHEM4007A 38 industry takes advantage of this characteristic of the process and has used extraction to separate, for example, aromatic hydrocarbons from paraffin hydrocarbons of the same boiling range using solvents such as liquified sulfur dioxide, furfural and diethylene glycol. In general, extraction is applied when the materials to be extracted are heat-sensitive or nonvolatile and when distillation would be inappropriate because components are close-boiling, have poor relative volatilities or form azeotropes. The simplest extraction operation is single-contact batch extraction in which the initial feed solution is agitated with a suitable solvent, allowed to separate into two phases after which the solvent containing the extracted solute is decanted. This is analogous to the laboratory procedure employing a separating funnel. On an industrial scale, the extraction operation more usually involves more than one extraction stage and is normally carried out on a continuous basis. The equipment may be comprised of either discrete mixers and settlers or some form of column contactor in which the feed and solvent phases flow countercurrently by virtue of the density difference between the phases. Final settling or phase separation is achieved under gravity at one end of the column by allowing an adequate settling volume for complete phase disengagement. Any one extraction operation gives rise to two product streams: the extracted feed solution, more usually termed the raffinate phase, and the solvent containing extracted solute termed the extract phase. This nomenclature is unique to liquid-liquid extraction processes and will be used from hereon. PROCESS DESIGN PRACTICE CHEM4007A 39 1.4.2 Choice of solvent: FIGURE 19: EXTRACTION 2 No single criterion can be used to assess the suitability of a solvent for a particular application and the final choice is invariably a compromise between competing requirements. Thus not only should the solvent be selective for the solute being extracted but it should also possess other desirable features such as low cost, low solubility in the feed-phase and good recoverability as well as being noncorrosive and noninflammable. Furthermore, interfacial tension between the two phases should not be so low that subsequent phase disengagement becomes difficult and the density difference between the phases should be large enough to maintain countercurrent flow of the phases under the influence of gravity. Of these factors, the first to be considered is the selectivity of the solvent, or the ease with which it extracts the desired solute from the feed stream. This is most readily understood by considering a simple ternary system consisting of a solution of solute C in a solvent A (the feed solution) and an extracting solvent B, which is designed to extract C from A. A simple single-stage extraction is shown on conventional triangular coordinates in Figure 1a. Here, a mixture of A and C of composition F is mixed with a pure solvent B in such proportions as to give an overall PROCESS DESIGN PRACTICE CHEM4007A 40 composition M. This lies inside the miscibility curve and so the mixture will separate into two separate phases, R and E, joined by an equilibrium tie line RE. If the solvent B is now stripped from each phase, the solvent-free composition of R is given by D and the solvent-free composition of E by the point G. Both solvent-free compositions lie, of course, on the side of the triangle AC and it will be seen that the initial feed solution of composition F has been separated into two solutions D and G, which have low and high concentrations of C, respectively. FIGURE 20: EXTRACTION OF SOLUTE C FROM A USING SOLVENTS B AND B' If this operation is now repeated using another solvent B' , the corresponding concentrations may be as shown in Figure 1b. In this instance, the solvent-free concentrations D and G are closer to the initial feed concentration F, and the separation of C is not as good as in the first case. It will be noted that the two solvents B and B' are associated with equilibrium tie lines of very different slopes, and effects of this nature may be quantified by defining a solvent selectivity βCA, analogous to relative volatility in distillation, such that: Since X/XCA is the partition coefficient of the system, m, (1) In most instances, β varies widely with concentrations; and for practical purposes, a solvent should be selected that gives high values of β in excess of unity and satisfies the other criteria listed above. PROCESS DESIGN PRACTICE CHEM4007A 41 The extraction of aqueous solutions is usually carried out using organic solvents or mixtures thereof. In recent years, interest has developed in the possibilities of using a second aqueous phase loaded with a suitable polymer so the extracted solute does not come into contact with organic solvents. This is of particular interest to the pharmaceutical and foodstuffs industries [see Verrall (1992) and Hamm (1992) for details of such aqueous-aqueous systems]. Phase Equilibria The first step in the design of any extraction process is the determination of the equilibrium relationships between the feed solution and the proposed solvent. This enables the suitability of the solvent to be assessed in terms of its selectivity, as well as the calculation of the numbers of extraction stages required for any set of flow conditions and degree of separation. Equilibrium data are usually determined directly in the laboratory since such measurements are more accurate than values calculated from predictive equations. Equilibria may be represented graphically on either triangular or rectangular coordinates, and a full discussion of the determination and representation of liquid-liquid equilibria has been presented by Treybal (1963). The correlation of equilibrium data is best achieved in terms of activity coefficients calculated from laboratory equilibrium measurements. A large number of semi-empirical equations are available for this purpose, but two models have found wide acceptance: the NRTL and the UNIQUAC equations for nonelectrolytes. In the absence of experimental data, it is not possible to determine the parameters of these equations and one must turn to purely predictive models, such as the regular solution and the UNIFAC models. All these procedures, as well as correlations for electrolyte solutions, have been discussed in detail by Newsham (1992) and this source should be consulted for further information. 1.4.3 Contactors: Contactors or extractors are specialized items of equipment designed to bring the feed and solvent phases together in such a manner that rapid transfer of the solute takes place from one phase to the other, followed by subsequent phase separation. In practice, efficient extraction involves four separate requirements: a. The initial dispersion of one phase into the other in the form of droplets. b. The maintenance of a fine dispersion in order to provide a large interfacial area for diffusion from one phase to the other. PROCESS DESIGN PRACTICE CHEM4007A 42 c. The provision of an adequate holding or retention time for an acceptable level of diffusion to take place. d. Final separation of the dispersion into raffinate and extract phases. Numerous contactors have been described in the literature and the characteristics of the principal types have been summarized by Pratt and Stevens (1992). These authors also discussed the selection, design and scale-up of industrially-relevant contactors. In its simplest form, a contactor merely consists of a stirred tank in series with a settling chamber through which the two phases flow (Figure 2a). Such arrangements are termed mixer-settlers and a number of units may be assembled in cascade to give the required degree of extraction. A typical assembly with countercurrent phase flows is shown in Figure 2b. Such devices can become uneconomical when a high level of extraction is called for because of the multiplicity of units employed. Each calls for separate stirrers and instrumentation for interface control in each settler, and it is more usual to employ some form of ‘column’ contactor in which only one settling chamber is involved, irrespective of the degree of extraction required. FIGURE 21: CONTACTOR ARRANGEMENTS (a) Single-stage mixer-settler. (b) Countercurrent multiple contact using mixer-settlers. (c) Spray column. (d) Packed column. (e) Rotating disc column. (f) Air-pulsed plate column. (g) Electrostatic column. (F = feedstream; S = solvent; R = raffinate; E = extract. The feedstream is assumed to be the heavier phase throughout.) The simplest column contactor is the spray tower (Figure 2c) in which one phase is dispersed into the other and overall flows are countercurrent through the column. Such units are inefficient and are of little interest outside the laboratory. If however some form of ordered or random packing, such as raschig rings, is introduced into the tower, extraction efficiency is increased several-fold. Such packed columns (Figure 2d) are an important item of industrial equipment. The packing not only reduces the gross back-mixing evident in the spray tower but also serves to PROCESS DESIGN PRACTICE CHEM4007A 43 establish a controllable droplet size distribution, as well as inducing additional turbulence inside and outside the droplets so diffusion from one phase into the other proceeds more rapidly [Batey and Thornton (1989)]. In column contactors described so far, energy available for droplet dispersion (and hence, the interfacial area available for solute transfer) is derived solely from the density difference between the phases; so the physical properties of the system set a limit to achievable extraction efficiency. This limitation may be overcome by supplying additional energy to the contactor and this concept has given rise to a large variety of so-called mechanical columns. Columns with coaxial rotating members of various designs have been described in the literature and the socalled rotating disc contactor illustrated in Figure 2e is a good example. This is basically a spray column with a central rotating shaft bearing a series of flat discs that rotate between fixed annular baffles. The shear forces set up produce very small droplets of dispersed phase and a correspondingly large interfacial area for mass transfer. Whilst such a unit gives good extraction efficiencies, the rotating shaft involves seals or bearings within the column and is therefore unsuitable for processing toxic or corrosive liquids. This limitation relative to corrosive liquids may be overcome if mechanical energy is introduced in the form of reciprocatory, rather than rotary, motion. Such contactors are known as pulsed columns, and the reciprocatory motion may be applied either to the plates in the column or to the process fluids themselves. The latter procedure is now virtually universal. A typical pulsed column is illustrated in Figure 2f and consists, in essence, of a column shell fitted with a number of fixed perforated plates or sieve trays. The pulse may be imparted to the process fluids by attaching a cylinder closed by a reciprocating piston to the base of the column, or more usually by applying a sinusoidally-varying air pressure to a vertical standpipe connected to the base of the column (Figure 2f). Such a device is known as an air-pulsed column [Thornton (1954)] and has the advantage that the process fluids are isolated from the pulsing mechanism by a pocket of air or inert gas. Such contactors have found wide application in the nuclear reprocessing industries. Column contents are usually pulsed sinusoidally at a frequency within the range 1–3 cycles per second and with an amplitude, measured in the column, of 12 mm or less. The perforated plates typically have a free area of 25% and are drilled with 3 mm diameter holes on a triangular pitch; the spacing between successive plates is 50 mm. Such a plate geometry does not allow the dispersed phase droplets to pass through readily except under the influence of the PROCESS DESIGN PRACTICE CHEM4007A 44 pulse, and very small droplets giving rise to large interfacial areas are readily obtained by varying the pulse frequency and/or amplitude. The extraction efficiency of the unit is therefore easily varied by changing the pulse characteristics and very high rates of extraction may be obtained with these columns. From an industrial viewpoint, mixer-settlers, rotating disc and pulsed columns have been employed successfully in a wide range of situations and extensive performance data are available in published literature. Mechanical energy is not the only method of producing small droplets and thereby large interfacial areas for solute transfer. On the laboratory scale, both sonic and electrical energy have been employed successfully. Thus a sonic generator in contact with process fluids in a spray-type column gives rise to good droplet dispersions and high extraction rates [Thornton (1953)]. A promising procedure developed in recent years is electrostatic extraction, wherein electrical energy is employed to effect dispersion of one phase into the other by charging the dispersed phase entry nozzle to a high potential relative to a secondary electrode downstream in the column [Thornton and Brown (1966); Stewart and Thornton (1967)]. The droplets formed at the entry nozzle are now very small and carry an electrical charge so that they are accelerated at high velocity towards the secondary electrode. Furthermore, since the droplets carry a charge they oscillate rapidly due to the lowered interfacial tension, and contactors can be designed with very small contact times coupled with high extraction rates comparable with those usually associated with pulsed-plate columns. Rapid extraction coupled with low retention times in the contactor are particularly appropriate to processes in which the solute is of biological origin, or is otherwise unstable during extraction operation. In practice, such electrostatic contactors comprise a column equipped with a number of insulated nozzle trays with a potential gradient between successive trays (Figure 2g). Designs for large-scale units have not yet been investigated in any detail, but the use of radial nozzle trays for larger diameter columns has been proposed [Thornton (1989)]. For a general discussion of electrostatic extraction, see Thornton (1976) and Weatherley (1992). 1.4.4 Factors for contactors design: The design of a column-type contactor basically involves the calculation of two geometrical parameters, viz., the height of column necessary to give the required degree of extraction and the diameter to handle the necessary flow rates under prescribed operating conditions. In the design of stage-wise units, such as mixer-settlers, the corresponding parameters are power input and PROCESS DESIGN PRACTICE 45 CHEM4007A residence time of the mixing chamber and the residence time of the settler necessary for satisfactory phase setting. The fundamental quantities usually employed to describe the hydrodynamic behavior of columntype contactors are the phase flow rates, fractional holdup of the dispersed phase and the characteristic mean velocity of the droplets. If the fractional voidage of the column is denoted by ε, the quantities are related by the holdup equation: (1) The term ( ) on the right hand side of Equation (1) takes into account the reduction in mean velocity of a multiplicity of droplets by comparison with the velocity of a single droplet in infinite media. This so-called hindered rising term can frequently be represented by a function of holdup (1 – x) so long as the droplet size is small and is independent of the phase flow rates—conditions frequently met in mechanical contactors. On this basis, the holdup equation takes the form: (2) A plot of [Vd + (x/1 – x)Vc] versus x(1 – x) is linear with a slope of and enables characteristic velocity to be determined from flow rate and holdup measurements. Progressive increases in either or both phase flow rates finally result in flooding of the contactor, which is manifested by the appearance of a second interface at the opposite end of the column to the main interface. This condition corresponds to maximum values of the flow rates beyond which holdup remains constant, and can be found by differentiating Equation (2) [Thornton and Pratt (1953)]. (3) (4) PROCESS DESIGN PRACTICE 46 CHEM4007A Eliminating εVo between Equations (3) and (4) and solving for xf yields (5) where L represents the ratio Vdf/Vcf and subscript f denotes values at the flood point. Thus the phase superficial velocities at the flood point, together with the associated dispersed phase holdup, may be determined from Equations (3)– (5) once the value of the droplet characteristic velocity is known; the latter is readily obtained by plotting experimental holdup measurements in accordance with Equation (2) and measuring the slope of the linear plot. By this means flood point data may be obtained from holdup measurements and vice versa [Thornton and Pratt (1953); Thornton (1956)]. It is important to note that Equations (2)–(5) are only appropriate for situations where mean droplet size is small and is constant up to the flood point. Furthermore the assumption is made that the effective buoyancy force between the phases is proportional to the difference in densities of the mixture and the dispersed phase (ρm – ρd). By the mixture law, this is equal to (ρc – ρd)(1 – x), thus accounting for the (1 – x) term on the right hand side of Equation (2). At higher Reynolds numbers, it is possible, in principle, to derive equations analogous to Equations (2)–(5) provided that satisfactory equations can be formulated to describe droplet motion in the column. This is not always possible at present and numerous semi-empirical expressions have been proposed in lieu of Equation (2) [Pratt and Stevens (1992)]. It should be noted that Equations (3)–(5) cannot be used to predict flooding rates in packed columns since droplet coalescence sets in prior to the flooding point. Relationships can be established between the Sauter mean droplet size, dvs, and the characteristic velocity by introducing the concept of column impedance, I. Thus in the case of a spray tower of height H, let the time taken for a droplet to move through this distance be t. The terminal velocity of the droplet, U, is then equal to H/t. In a contactor such as a perforated platecolumn, the same size droplets will take longer than time t to pass through a height H because they will suffer a small but finite delay, Δt, at each plate. In a column of N plates, the total delay will amount to NΔt and the velocity of the droplets relative to the continuous phase will be given PROCESS DESIGN PRACTICE 47 CHEM4007A by H/(t + NΔt). In the limit as holdup tends to zero, this velocity approaches the characteristic velocity , and taking the ratio of spray and plate column velocities yields the expression (6) where I is the column impedance and is defined as the fractional increase in time of passage of a single droplet with respect to an empty spray column. The terminal velocity U can be written in terms of mean droplet size and the physical properties of the systems using published drag coefficient data, thereby establishing the link between droplet size and for a known value of I via Equation (6). Values of I range from zero to some finite value, depending upon the characteristics of the contactor and the properties of the system. For the application of this concept to pulsed plate-columns and the use of laboratory holdup measurements to characterize the behavior of such contactors, see Batey et al. (1987). Diffusion of a solute from one liquid phase to another is a complex process governed by molecular and/or eddy diffusional mechanisms. Mass transfer flux is proportional to the instantaneous concentration driving force, and the ratio of these quantities is called the mass transfer coefficient and may be defined in terms of either the continuous or the dispersed phase driving force. Thus if solute A is transferring from phase c to phase d, the flux NA is given by: (7) In practice, it is not feasible to measure the two interfacial concentrations c ci and cdi in a practical extraction system and so, since the interfacial concentrations are assumed to be in equilibrium, diffusion from phase c to d can be considered to be diffusion of solute through two phases or resistances in series. No resistance will be offered by the interface itself because the chemical potentials in each phase will be equal. On this basis, the so-called overall coefficients Ko can be defined: (8) PROCESS DESIGN PRACTICE CHEM4007A 48 where all the concentrations are now known. For a linear equilibrium curve, the relationships between the individual phase or film coefficients and the overall coefficients are readily shown to be [Treybal (1963)] (9) (10) Numerous mathematical models have been proposed for calculating values of the individual phase coefficients k, but these make assumptions regarding the hydrodynamic characteristics of the phase in question [Skelland (1992); Javed (1992)]. Knowledge of turbulence levels and flow patterns in the vicinity of the interface is still far from complete and this limits the use of models for predicting k values. Contactor design is therefore based upon experimental measurements of the mass transfer coefficients, using the actual type of contactor and extraction system in question. For a detailed consideration of design procedures for column contactors and mixer-settler devices, see the comprehensive account by Pratt and Stevens (1992). Reference must be made, however, to the complications arising when the Marangoni Effect or spontaneous interfacial turbulence is present. Many solutes promote intense turbulence at the interface as they diffuse from one phase to the other [Perez de Ortiz (1992)]. The level of turbulence cannot be predicted from first principles and the consequences can only be assessed from extensive pilot plant studies. Thus, for example, extraction efficiency of countercurrent column contactors is usually expressed in terms of the height of a transfer unit or HTU [Treybal (1963)]. The overall HTU based upon the continuous phase driving force is defined as: (11) where the specific surface area a is equal to 6 εx/dvs, so that (12) PROCESS DESIGN PRACTICE 49 CHEM4007A Marangoni effects can influence mean droplet size, dvs, through enhanced interdroplet coalescence of rates; the holdup x, by virtue of a correspondingly increased value in Equation (2) and the overall mass transfer coefficient Koc through enhanced turbulence at the droplet interface [Thornton et al. (1985); Javed et al. (1989)]. Moreover, values of Koc become time-dependent and decrease as the droplet interface ages. (See Thornton (1987) for a further discussion of this problem.) The terms in square brackets with subscript M in Equation (12) are therefore all dependent upon the level of interfacial turbulence induced by the solute. The extent to which these quantities are modified by Marangoni phenomena is not yet quantifiable. It is therefore always desirable to study the characteristics of any proposed extraction system in the laboratory before proceeding to the design stage. Industrial extraction operations Details of relevant process chemistry and extraction operations in the hydrometallurgical, nuclear, pharmaceutical and food industries are provided by Thornton (1992). PROCESS DESIGN PRACTICE CHEM4007A 50 1.5 Absorber: FIGURE 22: ABSORBER 1.5.1: Definition: The removal of one or more component from the mixture of gases by using a suitable solvent is second major operation of Chemical Engineering that based on mass transfer. In gas absorption a soluble vapor is more or less absorbed in the solvent from its mixture with inert gas. The purpose of such gas scrubbing operations may be any of the following; a) For Separation of component having the economic value. b) As a stage in the preparation of some compound. c) For removing of undesired component (pollution). PROCESS DESIGN PRACTICE CHEM4007A 51 1.5.2 TYPES OF ABSORPTION 1) Physical absorption, 2) Chemical Absorption. Physical absorption: In physical absorption mass transfer take place purely by diffusion and physical absorption is governed by the physical equilibria. Chemical absorption: In this type of absorption as soon as a particular component comes in contact with the absorbing liquid a chemical reaction take place. Then by reducing the concentration of component in the liquid phase, which enhances the rate of diffusion.8.3 TYPES OF ABSORBER There are two major types of absorbers which are used for absorption purposes: Packed column Plate column COMPARISON BETWEEN PACKED AND PLATE COLUMN 1) The packed column provides continuous contact between vapor and liquid phases while the plate column brings the two phases into contact on stage wise basis. 2) SCALE: For column diameter of less than approximately 6 ft. It is more usual to employ packed towers because of high fabrication cost of small trays. But if the column is very large then the liquid distribution is problem and large volume of packing and its weight is problem. 3) PRESSURE DROP: Pressure drop in packed column is less than the plate column. In plate column there is additional friction generated as the vapor passes through the liquid on each tray. If there are large No. of Plates in the tower, this pressure drop may be quite high and the use of packed column could affect considerable saving. 4) LIQUID HOLD UP: Because of the liquid on each plate there may be a Urge quantity of the liquid in plate column, whereas in a packed tower the liquid flows as a thin film over the packing. 5) SIZE AND COST: For diameters of less than 6 ft, packed tower require lower fabrication and material costs than plate tower with regard to height, a packed column is usually shorter than the equivalent plate column. PROCESS DESIGN PRACTICE CHEM4007A 52 From the above consideration packed column is selected as the absorber, because in our case the diameter of the column is less than 6 ft. As the solubility is infinity so the liquid will absorb as much gases as it remains in contact with gases so packed tower provide more contact. It is easy to operate. FIGURE 23: DIFFUSIVITY PROCESS DESIGN PRACTICE CHEM4007A 53 Packing: The packing is the most important component of the system. The packing provides sufficient area for intimate contact between phases. The efficiency of the packing with respect to both HTU and flow capacity determines to a significance extent the overall size of the tower. The economics of the installation is therefore tied up with packing choice. The packings are divided into those types which are dumped at random into the tower and these which must be stacked by hand. Dumped packing consists of unit 1/4 lo 3 inches in major dimension and are used roost in the smaller columns. The units in stacked packing are 2 to about 8 inches in size, they are used only in the larger towers. The Principal Requirement of a Tower packing are: 1) It must be chemically inert to the fluids in the tower. 2) It must be strong without excessive weight. 3) It must contain adequate passages for both streams without excessive liquid hold up or pressure drop. 4) It must provide good contact between liquid and gas. 5) It must be reasonable in cost. Thus, most packing is made of cheap, inert, fairly light materials such as clay, porcelain, or graphite. Thin-walled metal rings of steel or aluminum are some limes used. Common Packings are: a) Berl Saddle. b) Intalox Saddle. c) Rasching rings. d) Lessing rings. e) Cross-partition rings. f) Single spiral ring. g) Double - Spiral ring. h) Triple - Spiral ring. PROCESS DESIGN PRACTICE 54 CHEM4007A 1.6 flash Flash evaporation is one of the simplest separation processes. A liquid stream containing several components is partially vaporized in a” flash drum” at a certain pressure and temperature. This results in two phases: a vapor phase, enriched in the more volatile components, and a liquid phase, enriched in the less volatile components. The fluid is pressurized and heated and is then passed through a throttling valve or nozzle into the flash drum. Because of the large drop in pressure, part of the fluid vaporizes. The vapor is taken off overhead, while the liquid drains to the bottom of the drum, where it is withdrawn. The system is called” flash” distillation because the vaporization is extremely rapid after the feed enters the drum. Because of the intimate contact between liquid and vapor, the system in the flash chamber is very close to an equilibrium stage. Figure 1 shows a schematic drawing of flash unit. (18) a FIGURE 24: FLASH PROCESS DESIGN PRACTICE CHEM4007A 55 1.7 Pumps: 1.7.1 Definition: Pump, a device that expends energy in order to raise, transport, or compress fluids. The earliest pumps were devices for raising water, such as the Persian and Roman waterwheels and the more sophisticated Archimedes screw. Pumps are classified according to the way in which energy is imparted to the fluid. The basic methods are (1) volumetric displacement, (2) addition of kinetic energy, and (3) use of electromagnetic force. A fluid can be displaced either mechanically or by the use of another fluid. Kinetic energy may be added to a fluid either by rotating it at high speed or by providing an impulse in the direction of flow. In order to use electromagnetic force, the fluid being pumped must be a good electrical conductor. Pumps used to transport or pressurize gases are called compressors, blowers, or fans. Pumps in which displacement is accomplished mechanically are called positive displacement pumps. Kinetic pumps impart kinetic energy to the fluid by means of a rapidly rotating impeller. Broadly speaking, positive displacement pumps move relatively low volumes of fluid at high pressure, and kinetic pumps impel high volumes at low pressure. PROCESS DESIGN PRACTICE CHEM4007A 56 FIGURE 25: PUMP A certain amount of pressure is required to get the fluid to flow into the pump before additional pressure or velocity can be added. If the inlet pressure is too small, cavitation (the formation of a vacuous space in the pump, which is normally occupied by liquid) will occur. Vaporization of liquid in the suction line is a common cause of cavitation. Vapor bubbles carried into the pump with the liquid collapse when they enter a region of higher pressure, resulting in excessive noise, vibration, corrosion, and erosion. The important characteristics of a pump are the required inlet pressure, the capacity against a given total head (energy per pound due to pressure, velocity, or elevation), and the percentage efficiency for pumping a particular fluid. Pumping efficiency is much higher for mobile liquids such as water than for viscous fluids such as molasses. Since the viscosity of a liquid normally decreases as the temperature is increased, it is common industrial practice to heat very viscous liquids in order to pump them more efficiently. PROCESS DESIGN PRACTICE CHEM4007A 57 1.7.2 Positive displacement pumps FIGURE 26: POSITIVE DISPLACEMENT PUMPS The positive displacement pump provides an approximate constant flow at fixed speed, despite changes in the counter pressure. Two main types of positive displacement pumps exist:  Rotary pumps  Reciprocating pumps PROCESS DESIGN PRACTICE CHEM4007A FIGURE 27: ROTARY PUMPS This is further broken up into sub-groups:  Rotary  Helical rotor or progressive cavity pumps  Peristaltic or hose pumps  Rotary Lobe or gear pumps Reciprocating  Diaphragm pumps  Piston pumps  Bucket pumps (windmills) The difference in performance of a centrifugal pump (non-positive displacement), compared to a rotary pump and a reciprocating pump. Depending on which of these pumps you are dealing with, a small change in the pump’s counter pressure results in differences in the flow. The flow from a centrifugal pump will change considerably. The flow of a rotary pump will change a little, while the flow of a reciprocating pump will hardly change at all. 58 PROCESS DESIGN PRACTICE CHEM4007A 59 The actual seal face surface is larger for rotary pumps than for reciprocating pumps. Even though the two pumps are designed with the same tolerances, the gap loss (fluid slippage) of the rotary pump is larger. These pumps are typically designed to the finest tolerances to obtain the highest possible efficiency and suction capability. However, in some cases, it is necessary to increase the tolerances, for example when the pumps have to handle highly viscous liquids, liquids containing particles or liquids of high temperature. Positive displacement pumps all pulsate, meaning that their volume flow within a cycle is not constant. The variation in flow and speed leads to pressure fluctuations due to resistance in the pipe system and in valves. A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity decreases. The volume is constant through each cycle of operation. Positive displacement pumps, unlike centrifugal or roto-dynamic pumps, theoretically can produce the same flow at a given speed (RPM) no matter what the discharge pressure. Thus, positive displacement pumps are constant flow machines. However, a slight increase in internal leakage as the pressure increases prevents a truly constant or linear flow rate. A positive displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head like centrifugal pumps. A positive displacement pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until the line bursts, the pump is severely damaged, or both. A pressure relief or safety valve on the discharge side of the positive displacement pump is therefore necessary. The relief valve can be internal or external. The pump manufacturer normally has the option to supply internal relief or safety valves. The internal valve is usually only used as a safety precaution. An external relief valve in thedischarge line, with a return line back to the suction line or supply tank provides increased safety.Grundfos utilize two types of positive displacement pumps in our equipment range.  Helical rotor in our SQ range of bore hole pumps  Diaphragm in our DDA, DMX, DMH, etc. chemical dosing range of pumps PROCESS DESIGN PRACTICE CHEM4007A 60 1.7.3 Kinetic pump: FIGURE 28: KINETIC PUMP Kinetic pumps can be divided into two classes, centrifugal and regenerative. In kinetic pumps a velocity is imparted to the fluid. Most of this velocity head is then converted to pressure head. Even though the first centrifugal pump was introduced about 1680, kinetic pumps were little used until the 20th century. Centrifugal pumps include radial, axial, and mixed flow units. A radial flow pump is commonly referred to as a straight centrifugal pump; the most common type is the volute pump. Fluid enters the pump near the axis of an impeller rotating at high speed. The fluid is thrown radially outward into the pump casing. A partial vacuum is created that continuously draws more fluid into the pump. PROCESS DESIGN PRACTICE CHEM4007A 61 1.7.4 Centrifugal pump FIGURE 29: CENTRIFUGAL PUMP A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure of a fluid. Centrifugal pumps are commonly used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from where it exits into the downstream piping system. Centrifugal pumps are used for large discharge through smaller heads. 1.7.5 ENTRIFUGAL PUMPS Modern process plants use powerful centrifugal pumps, primarily because of the following factors: 1. The low initial cost. 2. Low maintenance costs. PROCESS DESIGN PRACTICE CHEM4007A 62 3. Simple in operation. 4. Ability to operate under a wide variety of conditions. 5. Give a smooth, continuous flow, free from pulsation. 1.7.6 CENTRIFUGAL FORCE The word, ' centrifugal ' is derived from the Latin language and is formed from two words 'centri' meaning 'center' and 'fugal' meaning 'to fly away from'. Centrifugal - 'to fly away from the center'. This is the force developed due to the rotation of a body - solid, liquid or gas. The force of rotation causes a body, or a fluid, to move away from the center of rotation. Parts of a Centrifugal Pump A centrifugal pump is built up of two main parts: 1. THE ROTOR (or Rotating Element). 2. THE CASING (or Housing or Body). The Rotor One of the greatest advantages of a centrifugal pump is that it has very few moving parts which minimizes mechanical problems and energy losses due to friction. Other than the bearings, (and of course the driver), the only moving part in a centrifugal pump is the Rotor. The Rotor (Rotating Element), is made up of the following main components: 1. THE IMPELLER(S) -Often called the 'Wheel(s)'. (In the center of an impeller, is the 'EYE' which receives the inlet flow of liquid into the 'Vanes' of the impeller). 2. THE SHAFT -The impeller(s) is/are mounted on the shaft and enclosed by a casing. PROCESS DESIGN PRACTICE CHEM4007A 63 The Impellers These consist of wheel shaped elements containing 'Curved Vanes' at the center of which is the liquid inlet called the 'EYE' of the impeller. The wheel(s) is/are mounted on the shaft, (together called 'the Rotating Element' which is rotated at high speed. The liquid is thrown off the outer edge of the vanes, and more liquid flows into the eye to take its place. The speed of rotation of the wheel imparts kinetic energy to the liquid in the form of velocity which will be converted to pressure (potential) energy. There are various types of impeller depending on the duty to be performed by the pump. 1. The Open Impeller: This type consists of vanes attached to a central hub with no side wall or 'shroud'. It is used for pumping highly contaminated slurry type liquids. 2. Semi-Open Impeller: This type has the vanes attached to a wall or shroud on one side. It is used mainly for lightly contaminated and abrasive liquids and slurries. 3. Closed Impeller: This impeller has the vanes enclosed on both sides by a shroud and is the most efficient impeller used for clean or very slightly contaminated liquids. Impellers can also be classified according to the vane curvature - i.e. 'Backward' curve used for high flow rate. 'Forward' curve for high liquid head and 'Straight' for either service. PROCESS DESIGN PRACTICE CHEM4007A 64 Types of Impeller High power, high volume pumps are fitted with more than one impeller. This type is called a 'Multi- stage' pump and is actually a series of pumps mounted on the shaft within a single casing. The liquid leaving each impeller rim, is fed into the eye of the next wheel. In this way, the pressure is built up in stages through the pump. The more stages, the higher the discharge pressure. As liquids cannot be compressed and therefore no change in volume takes place, the impellers of a multi-stage pump are all the same size – (unlike those of a compressor). How the liquid is passed from stage to stage is discussed later in the notes on the casing. The Shaft The Impeller(s) are mounted on this part of the pump which is then referred to as the 'Rotor' or rotating element which is coupled (connected) to the pump driver. The driver imparts the rotation to the rotor that is housed in the casing, supported by the bearings. The shaft, due to the high speed of rotation, will tend to move: Radially -movement across the shaft (Vibration) and, Axially -movement along the shaft (Thrust). In order to minimize and control these movements, bearings are fitted (as discussed earlier). PROCESS DESIGN PRACTICE CHEM4007A 65 1.7.7 Regenerative pumps FIGURE 30: REGENERATIVE PUMPS The primary difference between a centrifugal and a regenerative turbine pump is that fluid only travels through a centrifugal impeller once, while in a turbine, it takes many trips through the vanes. Referring to the cross-section diagram, the impeller vanes move within the flow-through area of the water channel passageway. Once the liquid enters the pump, it is directed into the vanes, which push the fluid forward and impart a centrifugal force outward to the impeller periphery. An orderly circulatory flow is therefore imposed by the impeller vane, which creates fluid velocity. Fluid velocity (or kinetic energy) is then available for conversion to flow and pressure depending on the external system’s flow resistance as diagrammed by a system curve. It is useful to note at this point, that in order to prevent the internal loss of the pressure building capability of an MTH regenerative turbine, close internal clearances are required. In many cases, depending on the size of the pump, impeller to casing clearances may be as little as onethousandth of an inch on each side. Therefore, these pumps are suitable for use only on applications with clean fluids and systems. In some cases, a suction strainer can be used successfully to protect the pump. PROCESS DESIGN PRACTICE CHEM4007A 66 Next, as the circulatory flow is imposed on the fluid and it reaches the fluid channel periphery, it is then redirected by the specially shaped fluid channels, around the side of the impeller, and back into the I.D. of the turbine impeller vanes, where the process begins again. This cycle occurs many times as the fluid passes through the pump. Each trip through the vanes generates more fluid velocity, which can then be converted into more pressure. The multiple cycles through the turbine vanes are called regeneration, hence the name regenerative turbine. The overall result of this process is a pump with pressure building capability ten or more times that of a centrifugal pump with the same impeller diameter and speed. In some competitive designs, you will find that only a single-sided impeller is used. That design suffers from a thrust load in the direction of the motor that must be carried by the motor bearings. MTH turbines use a two-sided floating impeller design that builds pressure equally on both sides. This has the advantage of allowing the pump pressure to hydraulically self-center the impeller in the close clearance impeller cavity, while not burdening the motor bearings with excessive thrust loads. 1.7.8 Electromagnetic pumps FIGURE 31: ELECTROMAGNETIC PUMPS PROCESS DESIGN PRACTICE CHEM4007A 67 Electromagnetic pump is used for driving liquid metals in various industrial and research set ups. Liquid metals are invariable toxic and are mostly operated at high temperatures. Loops used for the study of corrosion and MHD studies need to maintain liquid metal purity within tight limits. Electromagnetic pumps provide non- intrusive method for driving liquid metals in loops. Mechanical seals are not required in these pumps; hence their chances of failures due to high temperatures and wear/tear get eliminated. Electromagnetic pumps for liquid sodium loops are designed using electromagnets and flow is maintained in pipes. Electromagnetic pumps can also be designed using MHD phenomenon. Both these EMP are similar to conventional linear pumps. The EMP presented in this paper is similar to conventional centrifugal pump. Its key components are rare earth permanent magnets, rotor, DC motor, semi-circular duct and CRNGO backing iron. Permanent magnets bars are fitted on the periphery of rotor and magnetized alternately along the radially in and radially out directions. High strength NdFeB magnets are used as they have large remnant flux density. A DC motor is used to rotate the rotor at various speeds. Rectangular channels provide passage for liquid metal flow. CRNGO laminated magnetic steel has been used to provide low reluctance path return path for the flux. This paper provides theoretical, analytical and practical aspects of electromagnetic pump. One such pump had been successfully designed and is operating at our lab at BARC. PROCESS DESIGN PRACTICE CHEM4007A 68 1.8 Compressors: 1.8.1 Definition: To decrease the size of gasses, you will need to increase the pressure to have a smaller volume by using a compressor. Compressor are commonly used in industries for different purposes. For example, compressor used to compress air, natural gas, and nitrogen. The most common gas used to be compressed by a compressor is air. The compressor aim is to convert the low-pressure air to a high-pressure air with minimum volume. It is very important to comprehend types of compressors, principles of compressors, and applications of compressors to distinguish between compressors. 1.8.2 Types of Compressors There are several types of compressors that used to compress gases to get high pressure and low volume. The first one is piston compressor and it works by using positive displacement system. The piston compressor is not very expensive and it is available in market permanently. Also, the way the piston compressor runs is simple and not complicated to consumers. The second type of compressor is centrifugal compressor which works by dynamic system. Moreover, it considered to be radial compressor because of the radial flow. The centrifugal compressor depends on the external circumstances such as alteration in inlet temperature. The third type of compressor is rotary screw compressor and it has high productivity. Similarly, the rotary screw compressor works by positive displacement system as the piston compressor. There lots of rotary screw compressor categories, so users will pick up the one that suits their specifications or requirements. In addition, it has low disturbance comparing to the piston compressor which has high disturbance. PROCESS DESIGN PRACTICE CHEM4007A FIGURE 32: (PISTON COMPRESSOR) FIGURE 33: CENTRIFUGAL COMPRESSOR 69 PROCESS DESIGN PRACTICE CHEM4007A 70 FIGURE 34: ROTARY SCREW COMPRESSOR-POSITIVE DISPLACEMENT 1.8.3 Principle of Compressors Positive displacement and dynamic compression are the two principles that compressors work. For instance, piston compressor and rotary screw compressor work as positive displacement system. The positive displacement idea is to draw an air in closed space, so the volume of the air in closed space will decrease by compressing the air. After pressure reaches the target point, the outlet will be open by using valves to let the air to pass. An easy example of positive displacement system is the pump used for bike, where an air will be drawn into a chamber and compressed by a piston upward and downward. On the other side, Centrifugal compressors work by dynamic compression principle which is different from positive displacement, where an air is drawn into blades in a very fast spinning impeller with a high speed. After that, the air is released, and kinetic energy is converted to static pressure. The dynamic compressor has a high efficiency and produces a high horsepower, so it considered an excellent choice for industries. PROCESS DESIGN PRACTICE CHEM4007A 71 1.8.4 Applications of Compressors Oil refineries and natural gas processing are example of piston compressor applications that works by positive displacement. Piston compressor is used in oil refineries because it is not expensive, and it has great competence. It increases the pressure ratio which makes it perfect for oil and gas industries. In addition, piston compressors are used in natural gas processing to move natural gas to industries. On the other hand, there are various applications for centrifugal compressors. For example, it used in gas turbines, automotive engines, air conditioning, and oil fields. Centrifugal compressors used in air conditioning to source compression in water series. For oil fields, centrifugal compressors used to advance oil improvement by using high pressure. Finally, larger productions need screw rotary screw compressor because it has constant air production which delivers compressed air. For instance, vessels and automated industrials are examples of rotary screw compressor applications. PROCESS DESIGN PRACTICE CHEM4007A Chapter 2 2.1 Reactor design. 2.1.1 Reaction and reaction kinetic: The reactions for acrylic acid production from propylene as follows: (1) (2) (3) The reaction kinetics are of the form: − = Where P is in , T is in K, R = 1.987 cal/mol K Where i is the reaction number above, and i 1 15000 2 20000 3 25000 FIGURE 35: KINETICS 72 PROCESS DESIGN PRACTICE CHEM4007A 2.1.2 HYSYS simulation of reactor: FIGURE 36: PLUG FLOW REACTOR 73 PROCESS DESIGN PRACTICE 74 CHEM4007A For Plug Flow Reactor (PFR): R-301 Volume of reactor (m^3) 1.963 Length of tube (m) 2.000 Diameter of tube (m) 0.100 Number of tubes 125 TABLE 1 PFR DIMENSIONS The effulent from the reactor (PFR) straem (6): Temperature(c) Pressure(bar) Vapor fraction Mass flow(ton/h) Mole flow(kmol/h) Propylene Nitrogen Oxygen Caron dioxide Water Acetic acid Acrylic acid From simulation 310 3.5 1 From reference 310 3.5 1 62.27 Error% 0 0 0 2444 2444 0 14.39 1056.7 51.6376 60.3488 1166.0798 6.544 88.135 14.7 1056.7 51.9 60.5 1165.9 6.54 87.79 2.154273801 0 0.508156847 0.250543507 0.015419185 0.061124694 0.391444942 TABLE 2: COMPARISON FOR THE EFFLUENT FROM THE REACTOR PROCESS DESIGN PRACTICE CHEM4007A 2.1.3 Simulation and results from shortcut: TABLE 3: SIMULATION AND RESULTS FROM SHORTCUT 75 PROCESS DESIGN PRACTICE 76 CHEM4007A The effluent from reactor (shortcut): Temperature(c) Pressure(bar) Vapor fraction Mass flow(ton/h) Mole flow(kmol/h) Propylene Nitrogen Oxygen Caron dioxide Water Acetic acid Acrylic acid From simulation 310 4.3 1 62.279 2444 From reference 310 3.5 1 2444 Error% 0 18.60465116 0 100 0 14.7006 1056.7 51.9825 60.4774 1165.8598 6.5278 87.7824 14.7 1056.7 51.9 60.5 1165.9 6.54 87.79 0.004081466 0 0.158707257 0.037369331 0.003448099 0.186892981 0.008657772 TABLE 4: COMPARISON FOR SHORTCUT REACTOR PROCESS DESIGN PRACTICE CHEM4007A 2.1.4 Reactor graphs. 2.1.4.1 Molar flow vs Reactor length. FIGURE 37: MOLAR FLOW VS REACTOR LENGTH 77 PROCESS DESIGN PRACTICE CHEM4007A 2.1.4.2 Temperature effects vs conversion (Rxn1 and Rxn2) FIGURE 38: TEMPERATURE EFFECTS VS CONVERSION (RXN1 AND RXN2) 78 PROCESS DESIGN PRACTICE CHEM4007A 2.1.4.3 Temperature VS total conversion: FIGURE 39: TEMPERATURE VS TOTAL CONVERSION 79 PROCESS DESIGN PRACTICE CHEM4007A 2.1.4.4 PFR volume VS conversion: FIGURE 40: PFR VOLUME VS CONVERSION 80 PROCESS DESIGN PRACTICE CHEM4007A 2.1.4.5 PFR volume VS conversion (Rxn1 and Rxn2): FIGURE 41: PFR VOLUME VS CONVERSION (RXN1 AND RXN2) 81 PROCESS DESIGN PRACTICE CHEM4007A 2.1.4.6 PFR volume VS conversion (Rxn1): FIGURE 42: PFR VOLUME VS CONVERSION (RXN1) 82 PROCESS DESIGN PRACTICE CHEM4007A 2.2 Distillation: 2.2.1 (T-303) simulation: FIGURE 43: (T-303) SIMULATION 83 PROCESS DESIGN PRACTICE 84 CHEM4007A 2.2.2 Comparison: Parameters comparisons From simulation From reference error Diameter (m) 2 2 0 Length (m) 58.34 - - Number of stages 31 31 0 Feed entering stage 22 22 0 Purity of acetic acid in top purity of acrylic acid in bottom 95.11 95 0.1157 99.999 99.9 0 TABLE 5: PARAMETERS COMPARISONS FOR DISTILLATION Stream table comparison Stream number (17) Temperature(c) Pressure(bar) Vapor fraction Mass flow(ton/h) Mole flow(kmol/h) Propylene Nitrogen Oxygen Caron dioxide Water Acetic acid Acrylic acid From simulation From reference Error% 46.63 47 0.78723 0.07 1.1 0.936 0.0 0.0 0 0.409 0.37 10.54 6.388 6.34 0.757 0 0 0 0 0 0 0 0 0 0 0 0 0.30 0.30 0 6.0780 6.03 0.796 0.0101 1.01 99 TABLE 6: STREAM TABLE COMPARISON FOR DISTILLATION PROCESS DESIGN PRACTICE 85 CHEM4007A Stream number 18 From simulation From reference error Temperature(c) 89.41 89 0.46 Pressure(bar) 0.16 0.16 0 Vapor fraction 0.0 0.0 0 Mass flow(ton/h) 6.89 6.25 10.24 Mole flow(kmol/h) 86.80 86.85 0.057 Propylene 0 0 0 Nitrogen 0 0 0 Oxygen 0 0 0 Caron dioxide 0 0 0 Water 0 0 0 Acetic acid 0.0020 0.05 96 Acrylic acid 86,7999 86.80 0.0001152 TABLE 7: STREAM NUMBER 18 FOR DISTILLATION The tables above show the difference between the calculated values of the steams and the reference obtained variables. The error percentage shown is considered to be relatively small except the difference in mass flow which is due to the change in composition of the total moles which resulted from the change in conditions of the unit operation. The conditions change in the unit operations are calculated automatically by Aspen hysys and it may be due to choice of the fluid package. While the empty dashed boxes show that the values are not available from the available reference. The calculated purity of acrylic acid in stream is very high which (99.9) is good and the separation process is considered successful. The purity of the byproduct is also good and can be used for different processes or can be sold. PROCESS DESIGN PRACTICE CHEM4007A 2.2.3 Distillation graphs: 2.2.3.1 Temperature vs Tray Position from top. FIGURE 44: TEMPERATURE VS TRAY POSITION FROM TOP 86 PROCESS DESIGN PRACTICE CHEM4007A 2.2.3.2 Pressure vs Tray position from top. FIGURE 45: PRESSURE VS TRAY POSITION FROM TOP 87 PROCESS DESIGN PRACTICE CHEM4007A 2.2.3.3 Pressure vs Tray position from top. FIGURE 46: PRESSURE VS TRAY POSITION FROM TOP 88 PROCESS DESIGN PRACTICE CHEM4007A 2.2.3.4 Pressure vs Tray position from top. FIGURE 47: PRESSURE VS TRAY POSITION FROM TOP 89 PROCESS DESIGN PRACTICE CHEM4007A Design for distillation tower (T-303): FIGURE 48: DESIGN FOR DISTILLATION TOWER (T-303) 90 PROCESS DESIGN PRACTICE CHEM4007A 2.3 absorption tower. 2.3.1 Absorption tower (T-301). 2.3.1.1 Simulation results for absorber (T-301): FIGURE 49: SIMULATION RESULTS FOR ABSORBER (T-301) 91 PROCESS DESIGN PRACTICE 92 CHEM4007A 2.3.1.2 Comparison for (T-301) results. From simulation From reference Error% 1 1 0 40.04957808 40 0.12395 60 100 40 Molar Flow [kgmole/h] 1348.967526 1342.9 0.45182 Mass Flow [kg/h] 41.80752802 37.89 10.3392 propylene 14.61707058 14.7 0.56735 co2 58.93803414 60.5 2.65018 o2 51.87421691 51.9 0.0497 h2o 158.6245071 150.1 5.37402 acrylic acid 7.552368666 7.97 5.52981 acetic acid 1.138793176 1.11 2.52839 1056.222536 1056.7 0.0452 Vapor Fraction Temperature [C] Pressure [kPa] nitrogen Stream 9: TABLE 8: COMPARISON FOR (T-301) RESULTS STREAM 9 PROCESS DESIGN PRACTICE 93 CHEM4007A Stream 9A: From Reference error 8.29E-02 0 100 co2 1.561965859 0 100 o2 2.58E-02 0 100 h2o 79877.27549 79885.8 0.01067 acrylic acid 5995.237631 5994.81 0.00713 acetic acid 420.4012068 420.45 0.01161 0.477464319 0 100 propylene nitrogen TABLE 9: COMPARISON FOR (T-301) RESULTS STREAM 9A The stream coming from the reactor contains many gases that need to be removed. So, first quench tower is used to cool the gases then the off gases go to absorption column that will absorb the liquid that the off gases took with it. The above data shows the comparisons of the results are obtained from aspen hysys of the distillation column and the data obtained from the reference. The percentage error in stream number 9 is duly noticeable which expected to be because the absence of the design information from the reference where the column is designed through using hysys default designs. Stream number 9A composition data have a low difference from the reference data which is good since the purpose is to increase the fraction of acrylic and acetic acids in the bottom products. The tower has 10 stages with a length of 5 meters and 1.5 meters diameter. PROCESS DESIGN PRACTICE CHEM4007A 2.3.1.3 T-301 graphs: 2.3.1.3.1 Temperature vs tray position from top T-301. FIGURE 50: TEMPERATURE VS TRAY POSITION FROM TOP T-301. 94 PROCESS DESIGN PRACTICE CHEM4007A 2.3.1.3.2 Pressure vs tray position from top T-301. FIGURE 51: PRESSURE VS TRAY POSITION FROM TOP T-301. 95 PROCESS DESIGN PRACTICE CHEM4007A 2.3.1.3.3 Flow vs tray position from top T-301. FIGURE 52: FLOW VS TRAY POSITION FROM TOP T-301. 96 PROCESS DESIGN PRACTICE CHEM4007A 2.3.1.3.4 Column properties vs tray position from top T-301. FIGURE 53: COLUMN PROPERTIES VS TRAY POSITION FROM TOP T-301 97 PROCESS DESIGN PRACTICE CHEM4007A 2.3.1.3.5 Composition vs tray position from top. FIGURE 54:COMPOSITION VS TRAY POSITION FROM TOP 98 PROCESS DESIGN PRACTICE CHEM4007A 2.3.1.3.6 K-values vs tray position from top. FIGURE 55:K-VALUES VS TRAY POSITION FROM TOP 99 PROCESS DESIGN PRACTICE CHEM4007A 2.3.1.3.1 Component Ratio vs tray position from top. FIGURE 56:COMPONENT RATIO VS TRAY POSITION FROM TOP 100 PROCESS DESIGN PRACTICE CHEM4007A 2.3.2 Absorption tower (T-302): 2.3.2.1 Simulation results for absorber (T-301): FIGURE 57: SIMULATION RESULTS FOR ABSORBER (T-301) 101 PROCESS DESIGN PRACTICE 102 CHEM4007A 2.3.2.2 Simulation results comparison (T-301): From simulation From reference error 1.5 - - Length (m) 5 - - Number of stages 10 - - Feed entering stage 10 - - Diameter (m) TABLE 10: SIMULATION RESULTS COMPARISON (T-301) Stream table comparison Stream number (11) From simulation From reference Error% 38.68 48 23.58 Pressure(bar) 1 1 0 Vapor fraction 1 1 0 Mass flow(ton/h) 39.83 37.35 6.6 Mole flow(kmol/h) 1272 1335.4 4.74 Propylene 14.6995 14.7 0.068 Nitrogen 1056.696 1056.7 0.0009 Oxygen 51.8998 51.9 0.019 Caron dioxide 60.4894 60.5 0.033 Water 87.9752 150.2 41.4 Acetic acid 0.0885 0.46 80.7 Acrylic acid 0.0462 0.98 52.85 Temperature(c) TABLE 11: STREAM NUMBER (11) PROCESS DESIGN PRACTICE 103 CHEM4007A Stream number 7: From simulation From reference 51.07 63 Pressure(bar) 2 2 18.93650794 0 Vapor fraction Mass flow(ton/h) 0 0 0 4.73 3.08 0.535714286 Mole flow(kmol/h) 212.1 148.5 Propylene Nitrogen 0.0005 0 0.428282828 0 0.004 0 0 Oxygen 0.002 0 Caron dioxide Water 0.0106 0 0 0 203.1248 140.9 Acetic acid Acrylic acid 1.0215 0.65 0.441623847 0.571538462 8 6.99 0.133590844 Temperature(c) error TABLE 12:STREAM NUMBER 7 Discussion for tower T-302: The above data shows the comparison of the results they are obtained from aspen hysys of the distillation column and the data obtained from the reference. The percentage error in stream number 11 is duly noticeable which expected to be because the absence of the design information from the reference where the column is designed through using hysys default designs. Stream number 7 composition data have a low difference from the reference data which is good since the purpose is to increase the fraction of acrylic and acetic acids in the bottom products. The tower has 10 stages with a length of 5 meters and 1.5 meters diameter. PROCESS DESIGN PRACTICE CHEM4007A 2.3.2.3 T-301 Graphs: 2.3.2.3.1 Temperature vs Tray position from top (T-301): FIGURE 58:TEMPERATURE VS TRAY POSITION FROM TOP (T-301) 104 PROCESS DESIGN PRACTICE CHEM4007A 2.3.2.3.2 Pressure vs Tray position from top (T-301): FIGURE 59:PRESSURE VS TRAY POSITION FROM TOP (T-301) 105 PROCESS DESIGN PRACTICE CHEM4007A 2.3.2.3.3 Composition vs Tray position from top (T-301): FIGURE 60: COMPOSITION VS TRAY POSITION FROM TOP (T-301) 106 PROCESS DESIGN PRACTICE CHEM4007A 2.4 Pumps simulations: 2.4.1 Simulation for pump (P-301 A/B) molten salt: FIGURE 61:SIMULATION FOR PUMP (P-301 A/B) MOLTEN SALT 107 PROCESS DESIGN PRACTICE CHEM4007A 2.4.1.1 Electric motor vs S for pump (P-304 A/B) molten salt: FIGURE 62:ELECTRIC MOTOR VS S FOR PUMP (P-304 A/B) MOLTEN SALT 108 PROCESS DESIGN PRACTICE CHEM4007A 2.4.2 Simulation for pump (P-302 A/B): FIGURE 63:SIMULATION FOR PUMP (P-302 A/B) 109 PROCESS DESIGN PRACTICE CHEM4007A 2.4.3 Simulation for pump (P-303 A/B): FIGURE 64:SIMULATION FOR PUMP (P-303 A/B) 110 PROCESS DESIGN PRACTICE CHEM4007A 2.4.4 Simulation for pump (P-304 A/B): FIGURE 65:SIMULATION FOR PUMP (P-304 A/B) 111 PROCESS DESIGN PRACTICE 112 CHEM4007A 2.5 Compressor: FIGURE 66: COMPRESSOR Name 1 a Vapour 1 1 Temperature [C] 25 224.7457642 Pressure [kPa] Molar Flow [kgmole/h] 100 430 1362 1362 39017.11966 39017.11966 Mass Flow [kg/h] TABLE 13: COMPRRESOR STREAM INFORMATION PROCESS DESIGN PRACTICE 113 CHEM4007A 2.6 Heat exchangers: FIGURE 67:E-301 SIMULATION 2.6.1 E-301 PROCESS DESIGN PRACTICE CHEM4007A 114 PROCESS DESIGN PRACTICE CHEM4007A E-301 Diameter of shell (mm) Internal:650 Outter:670 Number of tube and shell passes Tubes:6 Shells: - Series:1 - Parallel:4 Number of tubes 376 Tube pitch and arrangement Pitch(mm):23.81 Arrangement:30-trangular Number of shell-side baffles and their Number:2 arrangement Arrangement: single segmental Diameter, thickness and length of Diameter:19.05 tubes(mm) Thickness:2.108 Length:2850 Calculation of both shell and tubes sides Shell:6477 film heat transfer coefficient ( Tube:527.1 ) Heat transfer area of the exchanger(m2) 248.5 Shell side and tube side pressure drop (kpa) Shell: 4.875 Tube: 3.996 Materials of construction Carbon steal Approximate cost of exchanger 124296 $ TABLE 14: E-301 DESIGN INFORMATION 115 PROCESS DESIGN PRACTICE 116 CHEM4007A 2.6.2 E-302 FIGURE 68:E-302 SIMULATION PROCESS DESIGN PRACTICE CHEM4007A E-302 Diameter of shell (mm) Internal:750 Outter:774 Number of tube and shell passes Tubes:1 Shells: - Series:1 - Parallel:4 Number of tubes per pass 720 Tube pitch and arrangement Pitch(mm):23.81 Arrangement:30-trangular Number of shell-side baffles and their Number:8 arrangement Arrangement: single segmental Diameter, thickness and length of tubes(mm) Diameter:19.05 Thickness:2.108 Length:5850 Calculation of both shell and tubes sides film +4 Shell:3.701e heat transfer coefficient ( +4 Tube:1.439 e ) Heat transfer area of the exchanger(m2) 991.9 Shell side and tube side pressure drop (kpa) Shell: 40.56 Tube: 8.8 Materials of construction Carbon steal Approximate cost of exchanger 211680 $ TABLE 15:E-302 DESIGN INFORMATION 117 PROCESS DESIGN PRACTICE 118 CHEM4007A 2.6.3 E-303 FIGURE 69:E-303 SIMULATION PROCESS DESIGN PRACTICE CHEM4007A E-303 Diameter of shell (mm) Internal:650 Outter:670 Number of tube and shell passes Tubes:1 Shells: - Series:1 - Parallel:1 Number of tubes per pass 608 Tube pitch and arrangement Pitch(mm):23.81 Arrangement:30-trangular Number of shell-side baffles and their Number:6 arrangement Arrangement: single segmental Diameter, thickness and length of Diameter:19.05 tubes(mm) Thickness:2.108 Length:1300 Calculation of both shell and tubes sides Shell:2911 film heat transfer coefficient ( Tube:201.7 ) Heat transfer area of the exchanger(m2) 44.06 Shell side and tube side pressure drop (kpa) Shell: 0.1799 Tube: 2.710 Materials of construction Carbon steal Approximate cost of exchanger 33513 $ TABLE 16:E-303 DESIGN INFORMATION 119 PROCESS DESIGN PRACTICE CHEM4007A 2.6.3.1 Heat Exchanger (E-303) specification sheet: FIGURE 70: HEAT EXCHANGER SPECIFICATION SHEET 120 PROCESS DESIGN PRACTICE CHEM4007A Continue Heat Exchanger (E-303) specification sheet : 121 PROCESS DESIGN PRACTICE 122 CHEM4007A 2.6.3.2 Layout parameters ( Pitch , passes) FIGURE 71: LAYOUT PARAMETERS 2.6.3.3 Discussion E-303 results: Specification Refrence Sumulation Area (m^2) 43 44.06 Duty MJ/h 4870 303.3 Condensing steam temperature C 116 128 TABLE 17 DISCUSSION E-303 RESULTS PROCESS DESIGN PRACTICE CHEM4007A 2.6.3.3 Cold and hot stream temperatures: FIGURE 72: COLD AND HOT STREAM TEMPERATURE PROFILE E-303 123 PROCESS DESIGN PRACTICE CHEM4007A 2.6.3.4 Heat flow vs Temperature E-303. FIGURE 73: HEAT FLOW VS TEMPERATURE E-303 124 PROCESS DESIGN PRACTICE CHEM4007A 2.6.3.5 Temperature vs pressure for tube side E-303: FIGURE 74: TEMPERATURE VS PRESSURE FOR TUBE SIDE E-303 125 PROCESS DESIGN PRACTICE CHEM4007A 2.6.3.6 Temperature vs pressure for shell side E-303: FIGURE 75: TEMPERATURE VS PRESSURE FOR SHELL SIDE 126 PROCESS DESIGN PRACTICE CHEM4007A 127 PROCESS DESIGN PRACTICE 128 CHEM4007A 2.6.4 E-304 FIGURE 76:E-304 SIMULATION PROCESS DESIGN PRACTICE CHEM4007A E-304 Diameter of shell (mm) Internal:750 Outter:774 Number of tube and shell passes Tubes:1 Shells: - Series:1 - Parallel:4 Number of tubes per pass 723 Tube pitch and arrangement Pitch(mm):23.81 Arrangement:30-trangular Number of shell-side baffles and their Number:2 arrangement Arrangement: single segmental Diameter, thickness and length of Diameter:19.05 tubes(mm) Thickness:2.108 Length:2100 Calculation of both shell and tubes sides Shell:2.556e+4 film heat transfer coefficient ( Tube:5679 ) Heat transfer area of the exchanger(m2) 86.75 Shell side and tube side pressure drop (kpa) Shell: 9.615 Tube: 0.9020 Materials of construction Carbon steal Approximate cost of exchanger 41791 $ TABLE 18:E-304 DESIGN INFORMATION 129 PROCESS DESIGN PRACTICE CHEM4007A 2.6.5 E-305 FIGURE 77:E-305 SIMULATION 130 PROCESS DESIGN PRACTICE CHEM4007A E-305 Diameter of shell (mm) Internal:205 Outter:219.08 Number of tube and shell passes Tubes:1 Shells: - Series:1 - Parallel:1 Number of tubes per pass 16 Tube pitch and arrangement Pitch(mm):23.81 Arrangement:30-trangular Number of shell-side baffles and their Number:2 arrangement Arrangement: single segmental Diameter, thickness and length of Diameter:19.05 tubes(mm) Thickness:2.108 Length:3900 Calculation of both shell and tubes sides Shell:2677 film heat transfer coefficient ( Tube:9497 ) Heat transfer area of the exchanger(m2) 10.75 Shell side and tube side pressure drop (kpa) Shell: 0.9561 Tube: 2.203 Materials of construction Carbon steal Approximate cost of exchanger 11091 $ FIGURE 78:E-305 DESIGN INFORMATION 131 PROCESS DESIGN PRACTICE CHEM4007A 132 Chapter 3 Conclusion: In conclusion, the report discussed the detailed design of the production of acrylic acid plant and the information of each equipment along with providing a small comparison with showing the error percentage of the simulation data. The towers and reactor designs gave a good result with a small error percentage which shows the efficiency of the design and the accuracy of values obtained from the simulation. Besides that, the design of the heat exchangers, compressor and pumps was carried out successfully even though the numerical values of the outputs of heat exchangers are not provided in the reference, the designs obtained gave logical numerical values. Finally, the low accuracy of the results highly depends on the accuracy of the designs details and it should be handled carefully. PROCESS DESIGN PRACTICE CHEM4007A 133 References: (1) Unknown,2017.Chemicalreactor.Wikipedia.org. https://en.wikipedia.org/wiki/Chemical_reactor (2) unknown,n.d,Continuous Stirred Tank Reactors, http://encyclopedia.che.engin.umich.edu/Pages/Reactors/CSTR/CSTR.html (3) Unknown, 15 July 2017, Batch reactor, Wikipedia, https://en.wikipedia.org/wiki/Batch_reactor. (4) [1]unknown,n.d, A plug flow reactor. https://www.scribd.com/document/221505500/PlugFlow-Reactor-Lab-Report (5) Unknown, (3/12/2017). Batch reactor. wikipedia.org .https://en.wikipedia.org/wiki/Batch_reactor#Applications (6) Unknown, (2/12/2017). Continuous steer tank reactor. Visual Encyclopedia of Chemical Engineering. http://encyclopedia.che.engin.umich.edu/Pages/Reactors/CSTR/CSTR.html (7) Unknown, (2/12/2017). Plug Flow Reactors. Visual Encyclopedia of Chemical Engineering. http://encyclopedia.che.engin.umich.edu/Pages/Reactors/PFR/PFR.html (8) unknown, n.d. Distillation Columns. Visual encyclopedia of chemical engineering. http://encyclopedia.che.engin.umich.edu/Pages/SeparationsChemical/DistillationColumns/Distill ationColumns.html (9) M.T. Tham, 2016. TYPES OF DISTILLATION COLUMNS. rccostello.com. http://www.rccostello.com/distil/distiltyp.htm (10) Norrie, 2010. THE TRAY TYPE TOWER. compressionjobs.com http://articles.compressionjobs.com/articles/oilfield-101/2710-distillation-columns-towerscolumn-control-?start=1 (11) Unknow, 13 December 2017, Heat_exchanger, wikipedia. https://en.wikipedia.org/wiki/Heat_exchanger (12) Unknow,n.d, hx, scribd https://ar.scribd.com/document/366205064/hx (13) Unknow, 22 November 2017, what-is-a-heat-exchanger-how-does-it-work, clap4clap (14) https://clap4clap.com/2017/11/22/what-is-a-heat-exchanger-how-does-it-work/ (15) https://data.epo.org/publication-server/htmldocument?PN=EP0002382%20EP%200002382&iDocId=7343007 (16) https://www.dedietrich.com/en/recovery-acetic-acid-means-liquid-liquid-extraction (17) unknown, n.d. Absorption and Stripping.https://www.cpp.edu/~tknguyen/che313/pdf/chap51.pdf (18) https://en.wikipedia.org/wiki/Flash_evaporation#/media/File:Vap-Liq_Separator.png

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