Innovative dimethyl ether synthesis in a reactive dividing-wall column

Dimethyl ether (DME) is of great industrial interest due to its use as clean fuel for diesel engines or in combustion cells, as a precursor to other organic compounds, as well as a green aerosol propellant that can effectively replace chloro-fluoro-carbons. Conventionally, high purity DME is synthesized by dehydration of methanol produced from syngas, in a process involving a catalytic fixed-bed reactor and a direct sequence of two distillation columns. The key problem of this classic process is the high investment costs for several units that require a large overall plant footprint, as well as the associated high energy requirements. To solve these problems, we propose in this work an innovative DME process based on a reactive dividing-wall column (R-DWC) that effectively integrates in one shell a reactive distillation (RD) unit with the DWC technology. The double integrated system allows the production of high-purity DME in only one unit, with minimal footprint and significantly lower costs. This study also makes a fair comparison between the reported conventional DME process and the optimally designed process alternatives based on RD and R-DWC, respectively. All processes are optimized in terms of minimal energy requirements, using the state of the art sequential quadratic programming (SQP) method implemented in AspenTech Aspen Plus. The results clearly demonstrate that the R-DWC process has superior performances as compared to the conventional or RD process: significant energy savings of 12-58%, up to 60% reduced CO2 emissions, as well as up to 30% lower capital investment costs. (C) 2011 Elsevier Ltd. All rights reserved.