(202r) Optimal Design and Analysis of the MTBE Reactive Distillation System

Abstract for AIChE 2013 Annual Meeting

Optimal Design and Analysis of the MTBE Reactive Distillation System

Jen-Jung Lee and Gow-Bin Wang^*

Department of Chemical and Materials Engineering, Chang Gung University, Tao-Yuan 33302 Taiwan

Email: gbwang@mail.cgu.edu.tw Phone: 886-3-2118800ext.5757  Fax: 886-3-2118668

It is known distillation is the most widely used method of separation in the chemical process industry. Reactive distillation (RD) is an attractive and important process that combines reaction and separation in a single unit. Recently RD has drawn considerable attention due to its potential advantages over traditional processes. Methyl tertiary-butyl ether (MTBE) RD system is one of the main industrial applications.

A reactive distillation column used for production of MTBE from methanol and isobutene is considered in this study. The hydrocarbon feed for the MTBE RD column comes from an fluidized catalytic cracking (FCC) unit containing 36 mol% isobutene and 64 mol% inert n-butene. Wang et al. (2003) and Lee (2012)  have proposed the basic process flowsheet of the MTBE unit and presented the base case design parameters and operating conditions. This RD column operates at a reflux ratio of 7 and the required heat duty is about 49.03 MJ/s under the specifications set as 99.2 mol% MTBE purity and 92 % isobutene conversion.

The purpose of this work is to study the optimal design and analysis of the MTBE RD system. The UNIQUAC property set is used to model the liquid and gas-liquid interactions. The UNIQUAC binary interaction parameters shown in Table 1 and the reaction kinetics reported by Rehfinger and Hoffmann (1990) are used in all the simulations. The optimal operating condition is then determined by minimizing the total annual cost (TAC). Finally, different control structures are used to perform the dynamic simulations and to evaluate the control performance under the disturbances of feed flow rates and isobutylene feed composition. The primary simulation results show that, under the two-point temperature control structure, better disturbance rejection performance can be obtained. Further dynamic simulation studies are set to demonstrate its control effectiveness for the MTBE RD column.

Keywords: Reactive distillation, MTBE process, Optimal design, Process control, Process simulation

                                                          Table1 UNIQUAC binary interaction parameters (Rehfinger and Hoffmann, 1990)