Side-Reactor Configuration for Acetic Acid Esterification
Date Issued
2007
Date
2007
Author(s)
Tsai, Ruei-Chiang
DOI
zh-TW
Abstract
Reactive distillation (RD) combines reaction and separation in a single unit to reduce energy consumption and capital investment. Despite of potential advantages, the reactive distillation may suffer from maintenance/design problems such as catalyst deactivation/replacement and hardware design (for catalyst packing), especially for heterogeneous catalyst such as ion exchange resin. In this work, an alternative design, side reactor configuration, is sought and the processes of interest are the production of the ethyl acetate (EtAc) and the butyl acetate (BuAc) via esterification. The reactive distillation study in (Tang, et al., 2005) reveals that almost 90% conversion takes place in the column base of the RD and the rest of the 10% conversion occurs in the 10 reactive trays. This naturally leads to a coupled reactor/distillation configuration where all of the catalyst is packed in the bottoms base, denoted as Single Reactive Tray reactive distillation (SRT) hereafter. This mitigates the maintenance problem associated with conventional RD. However, simulation results show that, with the same amount catalyst loading (Wcat,RD), the SRT configuration cannot achieve the same performance as the RD (~93% conversion). Another alternative is adding external reactors to the Single Reactive Tray distillation column and this is termed as the Side Reactor Configuration (SRC). Unlike conventional reactive distillation design, the SRC design is less clear and design variables include: catalyst loading in the column base (Wcat,bot), % of equilibrium conversion for side reactor (% Xeq), sidestream withdrawn and return trays (Nss,r), sidestream flow rate (Fss). A systematic design procedure is devised for the SRC design and the objective function to be minimized is the total annual cost (TAC). The results show that the TAC of the SRC only increases by a factor of 5% as compared to that of the RD. The butyl acetate (BuAc) system is considered next. It differs from the EtAc system in (1) relatively even reaction distribution across reactive zone and (2) boiling point distribution where both reactants are intermediate keys. Two possible SRC configurations are explored. One is the pre-reactor (only one inlet stream to the column) plus side reactors and the other is complete side reactor scheme where all reactors coupled with the column. The results show that the complete side reactor scheme performs much better as compared to the pre-reactor plus side reactor scheme. As the total number of reactor increases to four, the TAC only increases by a factor of 25% as compared to that of the RD. For the two cases studied, the TACs of the SRC is slightly larger than that of the RD, however, considering the ease of catalyst replacement, the Side Reactor Configuration offers attractive alternative to conventional reactive distillation.
Subjects
反應蒸餾
側流反應器
乙酸乙酯
乙酸丁酯
reactive distillation
side reactor
ethyl acetate
butyl acetate
SDGs
Type
thesis
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