Synthesis of the Toluene Hydrodealkylation Process

In this section, process simulators are utilized to assist in carrying out the steps introduced io i Sections 3.4 and 3.5 for the synthesis of a process to hydrodealkylate toluene. This process was used actively following World War II, when it became favorable to convert large quanfi-  

As mentioned during the discussion of the synthesis steps, process simulators are very use fill. They are used to calculate heats of reaction, heat added to or removed from a stream power requirements for pumps and compressors, performance of a flash separator at variou temperatures and pressures, and bubble- and dew-point temperatures associated with distillates and bottoms products, among many other quantities. 

An objective is to examine the two separation sequences shown. In the direct sequence, valves A and D are open, B and C are closed, and product 1 (H2 and CH4) is recovered in the distillate of the first tower. Alternatively, in the indirect sequence, valves B and C arc open, and product 3 (C7H8 and C12H10) is recovered in the bottoms product of the first tower. 

Using the flowsheet simulators, design calculations are needed to estimate the reflux ratio and the theoretical tray requirements for the two towers in each of the sequences. In ASPEN PLUS, this is accomplished with the DSTWU subroutine, which is described in the module ASPEN — Separators Distillation FUG Shortcut Design on the multimedia CD-ROM. 

In HYSYS.Plant, the Shortcut Column model is used, which is described in the modules under HYSYS Separations — Distillation — Shortcut Distillation Column on the CD-ROM. 

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