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4
B3
6
3
B2
FLASH
1
5
2
Figure 13.6
Workshop 13.2a process.
TABLE 13.1 Process Feed
Component
Flow Rate (lbmol/hr)
Propane, C3
10
n
-Butane, NC4
20
n
-Pentane, NC5
20
n
-Hexane, NC6
10
Cyclohexane, CC6
40
reflux ratio is 1.0 and the distillate/feed ratio is 0.5. The overhead product is saturated
vapor at a pressure of 50 psi, and the column bottoms pressure is 51 psi. This model
should not incorporate optimization. The feed to the process is a saturated liquid at
250 psi and its composition is given in Table 13.1.
Workshop 13.2b
Develop an optimization, maximizing profitability, of the flow-
sheet above by varying the flash pressure between 150 and 250 psi. The objective
function needs to be coded in Fortran and will incorporate the following terms:
Stream 5
n
-hexane value: $0.1/lbmole
Stream 5 cyclohexane value: $0.20/mole
Coolant cost: $1
.
0
×
10
−
6
/Btu
Heating media cost: $1
.
0
×
10
−
7
/Btu
Net work cost: $0.020/hp
Workshop 13.2c
Develop an optimization of the flowsheet in three dependent vari-
ables. In addition to flash pressure, the column distillate/feed ratio varies between 0.4
and 0.7. The internal reflux ratio varies between 0.4 and 0.7 using the same objective
function as above.
