Distillation Design Project:
A column to separate an acetone-methanol mixture, with the modifications indicated below. A spreadsheet model should be developed to do the analysis. A written report, in technical memorandum form, should be submitted including paper copies of your worksheet results. Results should be presented in brief summary form - do not simply attach multiple pages of Excel tables.
Optimize the design of a column to process a feed stream containing 35% acetone at 30oC, to produce a distillate product with an acetone mole fraction of 0.75 and a bottoms acetone fraction of 0.0010. For this case, determine the following:
a. Minimum number of ideal stages
b. Minimum reflux ratio (pinch point may occur close to xD)
c. Number of ideal stages for a reflux ratio of 2 times the minimum
d. Number of actual trays for a reflux ratio of 2 times minimum with a Murphree efficiency of 75%
e. Column diameter to operate at 80% of the flooding velocity, with 18 inch tray spacing
f. Reboiler and condenser duties and approximate heat transfer areas (list assumptions about available steam and cooling water conditions).
Prepare plots showing the effect of reflux ratio on the number of trays and on reboiler and condenser duties for a range of 1.2 to 2.0 times the minimum reflux ratio. Recommend a particular design from these results. Further enhancements to reduce energy consumption are encouraged.
For your spreadsheet analysis you will need to obtain an equilibrium model for the acetone-methanol. Using the data given in the text, you can correlate the relative volatility as a polynomial in x and in y to get a reasonably good fit. A linear model works well enough for relative volatility vs x, while a quadratic will be needed for relative volatility vs y. You will also need to deal with how to switch from the stripping to the enriching section material balance at the appropriate point. Again, the class example workbook should be a good starting point.