Using the results from Problem 13.7 and Tables 1.5 and 1.7, compare the results for the simulation

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Using the results from Problem 13.7 and Tables 1.5 and 1.7, compare the results for the simulation of the benzene recovery column, T-101, using a shortcut method and a rigorous method. One way to do this comparison is to use the number of theoretical plates from the shortcut method as an input to the rigorous method. The rigorous method is used to simulate the same separation as the shortcut method, that is, the same overhead purity and recovery. The difference in the methods is then reflected by the difference between the reflux required for both methods. Comment on the difference for this nearly ideal system. Remember that there is no need to simulate the whole flowsheet for this problem; just use the input to the column from Table 1.5.


Problem 13.7

For the toluene HDA process, using the data given in Tables 13.1 and 13.2, simulate the process and compare the results with those given in Chapter 1, Table 1.5. Remember that the number of actual plates is given in Table 1.7, and an efficiency of 0.6 was assumed.Table 13.1 Commonly Observed Simulation Errors

Physical Situation Incorrect use of flash unit simulation Error Observed Including flash unit with heat load,

Mixing points Mixing streams at different pressures, outlet stream at lowest pressure (simulator default) Add

Zoned analysis required LMTD correction factor required but ignored For phase change operations, only one

Inappropriate reactor size Real vs. actual trays Desired product rate approaches constant value or starts to

Column pressure drop Column assumed to be at constant pressure or pressure Include pressure drop and make

drop chosen does not correspond to reality spacing; or assume weir height (typically 4-6 in and less than

Equipment Simulator Simulator Input Streams Number Equipment Equip. No. Table 13.2 Required Input Data for a

H-101 R-101 E-102 Heater Stoic react Flash h-1 r-1 f-1 4 93 9 - | 6 9 8 94 Outlet temperature = 600C

V-101 V-103 E-103 Flash Flash Hexch f-1 f-2 e-2 9 94 18 T - 8 17 10 94 18 No input required because vessel is

T-101 Shortcut tower t-1 10 - 19 11 = 90C Recovery of benzene in top product = 0.99 Recovery of toluene in

E-104 E-106 V-102 P-102 Shortcut tower Shortcut tower Shortcut tower Shortcut tower t-1 t-1 t-1 t-1 10 10 10

E-105 C-101 Hexch Compr Mixer Mixer Mixer e-3 C-1 m-2 m-3 m-4 95 97 3 2 6 | - 5 91 7 15 98 91 92 93 T Outlet

Mixer Mixer Splitter m-5 m-6 S-1 17 99 8 96 100 99 16 97 96 Pressure drop = o bar Pressure drop = o bar

Splitter Splitter S-2 S-3 98 19 - 5 100 7 95 drop = o bar Pressure drop = o bar Pressure drop = o bar

Table 1.5 Flow Summary Table for the Benzene Process Shown in Figure 1.3 (and Figure 1.5) Stream Number

Hydrogen 0.0 Methane Benzene Toluene 0.0 0.0 108.7 0.0 0.0 1.0 286.0 15.0 0.0 143.2 0.0 735.4 317.3 7.6 144.0

Table 1.7 Equipment Summary for Toluene Hydrodealkylation PFD Heat Exchangers E-101 E-103 FLH. MDP 36 11

Key: MOC 316SS CS Materials of construction Stainless steel type Par F.H. FI.H. 316 Carbon steel Partial

Vap Cond Recipr. Centrf. Stream being vaporized Stream being condensed Reciprocating Centrifugal Rbl s.p. 1

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Analysis Synthesis And Design Of Chemical Processes

ISBN: 9780134177403

5th Edition

Authors: Richard Turton, Joseph Shaeiwitz, Debangsu Bhattacharyya, Wallace Whiting

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