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EASC2211
TO:
FROM:
RE:
Date:
UNIVERSITY OF NEW HAVEN
TAGLIATELA COLLEGE OF ENGINEERING
Introduction to Modeling of Engineering Systems
Spring 2017
EASC2211 Students - Section 02
Jinsong Yu, EASC Instructor
Project 1 – Consulting on the Operation of a Solids Separation Process
March 20th, 2017
You are working as a consulting engineer and have been hired by a small manufacturing plant. The plant
engineer asks your advice on a solids-separation process, requiring that you develop a model to predict
the behavior over time for a transient process. The process has an operating cycle that requires periodic
removal of accumulated solids. Your model will be used to advise the client about the timing of the solids
removal. The results of your work should be presented in a technical memo, with calculations attached,
written for the plant engineer. The memo should include data tables and plots (in the memo) to explain
and justify your recommendations. The delivery date for your work is Monday, April 10th 2017.
Preliminary results will be required about a week earlier to assure that progress is being made.
Solids Separation Process
A separation process is used to remove solids from a mixture using a settling tank. The feed stream flows
slowly through the settling tank allowing most of the solids to settle and remain in the tank. The liquid
stream leaving this tank, called the overflow, has a small residual amount of solids, which varies with the
fraction of solids currently in the settling tank. The overflow leaving the settling tank accumulates in a
storage tank. The process operates continuously until either of 2 conditions is met:
1. the mass fraction of solids in the storage tank reaches 0.70% (0.0070 kg solids/kg). Note that
this refers to the accumulated solution in the storage tank, NOT to the stream entering this tank
2. the mass fraction of solids in the separation tank reaches 25% (0.25 kg solids.kg)
When either condition is reached, the process is stopped so that the settling tank can be cleaned out and a
new storage tank is set in place.
Some preliminary laboratory work provides the following information:
• The fraction of solids (y kg solids/kg) in the overflow stream varies with the solids concentration
in the settling tank (x kg solids/kg) according to this equation: y=0.050 x
• The specific gravity of the solution can be estimated by the relationship 1.1/(1.1-x), where x is the
fraction of solids. This relationship applies to all mixtures in streams or vessels.
The stream to be processed contains 6.00 mass % solids and flows at a rate of 5.0 kg/min. Assume that
the total mass in the settling tank remains constant, but the concentration, density and volume change
with time. Initially the settling tank contains 200. liters of pure water, with no solids. The product
collection tank is empty at the start of the process.
Simulation Model
Complete the required work in four phases:
1. Develop the simulation model by drawing and labeling a process diagram and writing mass
balances (total mass and solids) for both the settling tank and the storage tank.
2. Set up an Excel sheet to integrate the transient balances to track the accumulation of solids in the
settling tank (total mass is constant) and the accumulation of solids and water in the storage tank.
EASC2211
UNIVERSITY OF NEW HAVEN
TAGLIATELA COLLEGE OF ENGINEERING
Introduction to Modeling of Engineering Systems
Spring 2017
3. Create a plot showing the solids concentration in each tank as a function of time. You should
show both tanks on a plot, but will need to use a secondary axis for one of the tanks since the
solids fractions differ significantly. Create a second plot showing volume of each tank as a
function of time.
4. Complete a technical memo that contains required information and data displays
Your model will be based on the transient mass balances for the settling tank and the collection tank. Set
up total mass and solids balances in rate form for the tanks. Since the total mass in the settling tank is
constant, the accumulation rate of total mass is zero, but the solids balance will have a positive
accumulation rate. Numerical integration will be needed for tracking the solids concentration in each tank.
As part of your work you must determine the appropriate time step to produce results that are accurate
to three significant figures. Accuracy of numerical integration can be controlled by comparing the
results at a specific time (e.g., mass fraction solids in settling tank at 30 minutes) for two runs made with
different step sizes. Pick a time step size and then re-run the integration with the time step reduced by a
factor of about 2. Repeat until you see no difference in the third significant figure (note: for the number
0.04321, neither zero is significant). You will need to explain your time step choice in your memo using
an appropriate table to justify the accuracy of your model to the client.
Recommend an operation time for the process to the plant engineer. Note that the recommendation should
balance practical considerations with the maximum solids fraction allowed in each tank. The operators
will use both the time and the tank volumes in determining when to stop the process for removing solids
from the settling tank and replacing the accumulation tank. Both actions will be done at the same time, so
your recommendation should be a single time, along with the expected volume in each tank. Avoid giving
a time with a ridiculous number of digits, the operators do not work at infinite speed.
Report Requirements
Report your results to Mr. Ian T. Graytor, Senior Plant Engineer, in a technical memo, no longer than 3
pages. Appropriate data tables and plots should appear in the memo along with your explanation of your
work and your recommendations. Briefly discuss the basis for your model (basic mass balance equations
used) and the mathematical techniques employed. A portion of your spreadsheet should be attached as an
appendix to the technical memo. Do not include the full table of numerical integration results (it will
likely be hundreds of lines), but do include a diagram of the process with variables, equations and enough
of the results to allow the client to understand and possibly reproduce your work.
Students may work in pairs to develop the models, but each student must write and submit his or her own
memo. A copy of your spreadsheet showing preliminary results (just a page or 2) should be submitted by
April 3rd 2017 to assure that progress is being made. This should be a single paper (can be double sided)
submitted in class. Identify both team members in the heading of the spreadsheet. The technical memo
with appendix is due Monday, April 10th, 2017. Note that this is a PITCH project in which technical
communications is a major focus. The project grade will depend on the quality of communications in the
memo and spreadsheet as well as the technical merit of the work. Refer to PITCH documents on memos
and data displays.
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