A unit for enriching / recovering lead (Pb) from a process stream containing 7.25 wt% lead (Pb) (balance water) has a maximum capacity feed rate of 4500kg/h. The enriching unit removes 92% of the Pb from the feed that enters the unit, and the enriched Pb "product" can be considered essentially pure. If the feed enters at a rate higher than 4500kg/h, the excess feed bypasses the enriching unit and combines with the liquid that has been processed by the unit. The liquid is then sent to a downstream process
Without assuming a basis of calculation, draw and label a flowchart of the process. (Labels should include stream composition, i.e. Pb and water, and units.)
b. If the feed stream enters the unit at 6300 kg/h. Calculate the following, and include units:
i. Flow rates of Pb in the two streams split at the bypass point (prior to the enriching unit) ii. Flow rate of Pb from the enriching unit “product” stream
iii. Flow rate of the liquid stream leaving the enriching unit, and mass fraction of Pb in this liquid stream
iv. Flow rate of the liquid stream sent to the downstream process (after combining with excess feed), and the mass fraction of Pb in this liquid stream
c. Calculate the flow rate of liquid to the downstream process and the mass fraction of Pb in this liquid for feed stream flow rates that vary from 1000 kg/h to 10,000 kg/h, in 1000 kg/h increments. Generate a plot of the mass fraction of Pb in the stream going to the downstream process versus the feed flow rate. Suggestion: Use and submit a spreadsheet for these calculations, e.g. use Excel.