Specifications

2 LTI Models
2-46
Figure 2-3: Distillation Column
Schematically, the distillation process functions as follows:
•Steam flows into the reboiler and vaporizes the bottom liquid. This vapor is
reinjected into the column and mixes with the feed
•Methanol, being more volatile than water, tends to concentrate in the vapor
moving upward. Meanwhile, water tends to flow downward and accumulate
as the bottom liquid
•The vapor exiting at the top of the column is condensed by a flow of cooling
water. Part of this condensed vapor is extracted as the distillate, and the rest
ofthecondensate(thereflux) is sent back to the column.
•Part of the bottom liquid is collected from the reboiler as bottom products
(waste).
The regulated output variables are:
•Percentage of methanol in the distillate
•Percentage of methanol in the bottom products.
Feed
Enriched vapor
Cooling water
Condensate
Reflux
Distillate
Vapor
Steam flow
Reboiler
Bottom liquid
Bottom products
X
D
X
B