Page 138 - Process simulation and control using Aspen

ASPEN PLUS SIMULATION OF DISTILLATION MODELS 127

BTU/LB - 1381.4403 605.3231 -431.8608
BTU/HR -4 9921+06 1 .3553+06 -2 .5275+06
.
ENTROPY:
BTU/T.RMOL-R -58.6713 -30.5758 -28.8269
BTU/LB-R -1 . 9515 -1 .0898 -0 .9851
DENSITY:
LBMOiyCUFT 0 . 8564 0 . 9725 2 .6329-03
LB/CUFT 25.7482 27.2844 7 . 7046-02
AVGMW 30.0643 28.0568 29.2633

ASPEN PLUS PLAT: WIN32 VER: 11.1 07/12/2007 PAGE 6
SIMULATION OF A SHORTCUT DISTILLATION COLUMN
PROBLEM STATUS SECTION

BLOCK STATUS

* *
*
Calculations were completed normally *
*
All Unit Operation blocks were completed normally *
« *
*
All streams were flashed normally *
« #

3 .2 .2 Simulation of a RadFrac Model

Problem statement
We will continue the above problem with few modifications. A hydrocarbon stream,
consisting of 60 mole% ethane and 40 mole% ethylene, enters a RadFrac column having
a flow rate of 200 Ibmol/hr at 750F and 15 psia. The distillation process that has total
68 theoretical stages (including condenser and reboiler) and a total condenser operates
f
at 300 psia with zero pressure drop throughout. The distillate rate, relux ratio and
feed tray location are given as 79.8 Ibmol/hr, 8.75 (mole basis) and 41 (above-stage),
respectively. Consider the RK-Soave property method.

(a) Simulate the column and compute the compositions of top as well as bottom
products.
(b) Is there any discrepancy in product compositions obtained from RadFrac and
DSTWU columns? If yes, what is the main reason?

Note: In the comparative study (for part b), consider total 68 theoretical stages (including
condenser and reboiler) keeping other entered data unchanged for the DSTWU column
(see Subsection 3.2.1).

Simulation approach
(a) Start with the General with English Units Template, as shown in Figures 3.25(a)
and 3.25(b).