Mathematical modeling and optimization of DME synthesis in two spherical reactors connected in series

Due to some disadvantages of conventional tubular reactors, spherical reactors attract more attentions. In the present study, dimethyl ether (DME) synthesis by dehydration of methanol is considered in two-stage axial flow, spherical packed bed reactors connected in series. The catalyst volume in the conventional reactor (CR) is divided into two sections to pack spherical reactors. In this novel configuration, the unreacted methanol from the first reactor passes through a heat exchanger to reach to a desire temperature and then enters top of the second reactor as the inlet feed. In fact in this study, the unused catalyst in the conventional reactor is used efficiently in the second spherical reactor of the proposed configuration to produce more DME by dehydration of unreacted methanol from the first reactor. The inlet temperatures as well as the catalyst distributions for each reactor in this configuration are optimized using differential evolution (DE) method to maximize the outlet DME production rate. Then the optimization results are compared with the conventional one. The results show that, 3153 ton/day DME is produced, which is a gain of 16.3% over a conventional reactor, using the same catalyst loading and duty.