C3

MeOH Recycle = D3

Figure 8.24 The TAME process with extractive distillation methanol recovery.

Block C1: Liquid Composition Profiles

Block C1: Liquid Composition Profiles

Stage

Figure 8.25 Composition profiles in reactive column.

Stage

Figure 8.25 Composition profiles in reactive column.

Block C1 Temperature Prcrte

Block C1 Temperature Prcrte

Temperature Profile For Reboiler

Stage

Figure 8.26 Temperature profile in reactive column.

Stage

Figure 8.26 Temperature profile in reactive column.

Reboiler heat input and condenser heat removal are 38.2 and 39 MW, respectively. The operating pressure is 4 bar, and the column diameter is 5.5 m. The overall conversion of 2M1B and 2M2B in the C5 fresh feed is 92.4%.

Distillate D1 has a composition of methanol (28 mol% methanol) that is near the azeo-trope at 4 bar. It is fed at a rate of 1122 kmol/h to the methanol recovery columns section. Table 8.2 gives information about important streams associated with the prereactor and reactive distillation column.

8.3.2 Effect of Design Parameters on Reactive Column

It is interesting to explore reactive columns that are different from the one recommended by Subawalla and Fair.1 In this section several design parameters are changed, and their impacts on the steady-state performance of the reactive column are determined.

The reactive column is simulated in Aspen Plus using RadFrac with reactive trays. The convergence of this very nonlinear, highly nonideal column can be quite difficult. Using the Estimates feature in the column block helps the convergence problem (see Figs. 8.27 and 8.28). These estimates are copied from temperatures and compositions found in the Profile list under the C1 column block once a converged case is attained. The Azeotropic convergence method is selected on the Setup page tab of the column block for reactive column C1, as shown in Figure 8.29.

In order to obtain the same basic operation while design parameters are changed, two "design spec/vary" functions are set up in column block C1.

Setup

RateSep Setup Design Specs Vary

Heaters Coolers

Pumparounds

Decanters

Efficiencies

Reactions

Condenser Hcurves Reboiler Hcurves MQ Curves Tray Sizing Tray Rating Pack Sizing Pack Rating Properties Estimates Convergence Analysis Report

RateSep Report User Subroutines RateSep User Subrout Dynamic

Dynamic Equipment HT Block Options Results Summary Profiles

Interface Profiles Efficiencies and HETP Transfer Coefficients Dimenslonless Number: EO Variables EO Input

■/Temperature | Flows -/Liquid CompositionVapor Composition | (-Liquid mole fraction estimates (optional)-

Stage ics

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