The objective of this work is to separate a binary mixture and to cool down the bottom product for storage. (Check table below to see which mixture you are asked to study).
100 kmol of feed containing 10 mol percent of the lighter component enters a continuous distillation column at the mixture bubble point and the vapour leaving the column is condensed but not cooled and provides reflux and product.
The separation required is 90% of the maximum achievable separation in terms of top product molar composition. It is required to find the number of plates required and the feed plate position.
Part 1:
1.1. Determine an appropriate thermodynamic model for your binary system using the experimental data given Perry's Chemical Engineers' Handbook . (You may want to try more than one option)
Part 2:
2.1. Simulate the column in HYSYS using a short cut distillation approach.
2.2. Simulate the column in HYSYS using a stage-to-stage model.
For each case you are required to state the number of stages and the position of the feed as well as the top and bottom compositions.
You will need to discuss the differences between the two approaches as well as the differences between the results produced by the two approaches. You will also be required to discuss the effect of varying different parameters of your choice.
Part 3:
For storage purposes, the bottom product of the stage to stage column needs to be cooled to 30oC using a shell and tube heat exchanger. Cooling water is available at 15oC.
3.1. Simulate the heat exchanger in HYSYS.
3.2. Simulate the heat exchanger in EXCEL.
Your Excel spreadsheet should be understandable and user friendly. Make use of the comment boxes and/or text to comment on the construction, calculations and use of your spreadsheet.
Your HYSYS simulation should allow you to check the effect of varying:
? LMTD through the inclusion and exclusion of the correction factor.
? Varying the Tube Bundle in sensible ways and drawing sensible conclusions.
? Do some simulations on the appropriate shell sizes.
? Vary any other parameter that you can sensibly and meaningfully simulate
As per the exercise done in class, your spreadsheet should be capable of
? Doing the ENERGY BALANCE
? Calculating a LMTD
? Inserting an external correction factor for the LMTD
? Calculating a value of UA for the exchanger.
? Calculating a surface area for a stated size of Tube Bundle
? Making adjustments as required to the values of A and hence U.
Both your EXCEL Spreadsheet and the HYSYS simulation should allow you to make recommendations as to which heat exchanger conditions to use.
You will need to discuss any differences between the two sets of results.
Your report
You are asked to produce a report addressing all the points outlined above and support your report with the EXCEL and HYSYS files as appropriate.
Although this is an open ended exercise, your report should be kept concise and not more than 15 pages.
If necessary and appropriate, use tables, graphs and diagrams to illustrate your answer. Include any detailed calculations in appendices.
It is not necessary to show your general knowledge of distillation, heat exchangers or process simulation - please keep it specific to solving this particular problem. However, you need to include a brief explanation of how the models have been developed making sure to address all the key points.
Ethanol-benzene