Download Worksheet: DoF Analysis Dr. Lamm

Worksheet: DoF Analysis
Dr. Lamm
Supplemental Instruction
Iowa State University
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Course:
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Shawn V.
CH E 210
Dr. Lamm
1-31-2016
Practice Problems
A liquid mixture containing 30 mol% benzene (B), 25 mol% toluene (T), and the
balance xylene is fed into a distillation column. The bottoms product contains 98
mol% X and no B, and 96% of the X in the feed is recovered in this stream. The
overhead product is fed into a second column. The overhead product of the second
column contains 97% of the B in the feed to this column. The composition of this
steam is 94 mol% B and the balance T. Calculate the percentage of benzene in the
process feed that emerges in the overhead product from the second column.
Calculate the percentage of toluene in the process feed that emerges in the bottom
product from the second column.
Seawater containing 3.5 wt% salts passes through a series of ten evaporators.
Roughly equal quantities of water are vaporized in each of the ten units and then
condensed and combined to obtain a product stream of fresh water. The brine
leaving each evaporator is fed to the next one (except the tenth). The brine leaving
the tenth evaporator contains 5.00 wt% salt.
Draw a flow chart of the process that shows the first, fourth, and tenth evaporators.
Determine the amount of fresh water that can be obtained from the process (kg
fresh water/ kg feed). Determine the weight percentage of the salt in the solution
leaving the fourth evaporator.
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Methanol is synthesized from carbon monoxide and hydrogen in a catalytic
reactor. The fresh feed to the process contains 32 mol% CO, 64 mol% H2, and the
balance nitrogen. This stream is mixed with a recycle steam in a ratio 5 mol
recycle / 1 mol fresh feed to produce the feed to the reactor, which contains 13
mol% nitrogen. A low single-pass conversion is obtained in the reactor. The
reactor effluent goes to a condenser from which two streams emerge: a liquid
product stream containing essentially all the methanol formed in the reactor, and a
gas stream that contains all the CO, H2, and N2 leaving the reactor. The gas stream
is split into two fractions: one is removed from the process as a purge stream, and
the other is the recycle steam that combines with the fresh feed to the reactor.
For a methanol production rate of 100 kmol/h, calculate the fresh feed rate
(kmol/h), the molar flow rate and composition of the purge gas, and the overall and
single-pass conversions.