Space-constrained purification of dimethyl ether through process intensification using semicontinuous dividing wall columns

Abstract

This pre-print has been archived on the author's personal website (macc.mcmaster.ca) and/or the author's institutional repository (macsphere.mcmaster.ca) in compliance with the National Sciences and Engineering Research Council (NSERC) policy on open access and in compliance with Elsevier's academic sharing policies. ABSTRACTIn this work, a distillation system that purifies dimethyl ether (DME) from its reaction by-products is designed to aid in the conversion of natural gas, flare gas, or solution gas into a useful energy product in remote locations. The distillation equipment must fit inside of a 40-foot shipping container to be easily transported.Given the size constraint of the system, process intensification is the best strategy to efficiently separate the mixture. Several process intensification distillation techniques are explored, including the dividing wall column (DWC) and a novel semicontinuous dividing wall column (S-DWC). The traditional DWC and the S-DWC both purify DME to fuel grade purity along with producing high purity waste streams. The S-DWC purifies the reaction intermediate methanol to a higher grade than the DWC and is pure enough to recycle back to the reactor. An economic comparison is made between the three systems. While the DWC is a cheaper method of producing DME, the trade-off is the purity of the methanol produced.Overall, this research shows that it is possible to purify DME and its reaction byproducts in a 40-foot distillation column at a cost that is competitive with Diesel.

Computer‐aided process intensification: Challenges, trends and opportunities

“…For example, the integration of heating and cooling tasks leads to a heat exchanger with two process streams, while integration of reaction and separation leads to a reactive‐flash or reactive distillation column. The tasks performed in the equipment is not changed by PI but rather the process space within the equipment is altered . For example, a micro heat exchanger improves the heat addition and/or removal by offering a better surface area to volume ratio.…”

Finding Better Limit Cycles in Semicontinuous Distillation. 2. Extended Back-Stepping Design Methodology

“…In the Larson et al process, the bottoms product is further separated into DME, MeOH, and H 2 O streams using continuous distillation in a sequence of two distillation columns. Intensified distillation systems like dividing wall distillation and semicontinuous distillation (including semicontinuous dividing wall distillation) were proposed in the literature for separating this ternary mixture as an alternative to conventional distillation technology because they use less energy and are smaller in size . In this paper, the concentration is on semicontinuous distillation (with middle vessel) proposed by Pascall and Adams as a potential process intensification approach for the separation of DME, MeOH, and H 2 O, replacing the two continuous columns in the Larson et al The Pascall and Adams simulation-based study demonstrated that semicontinuous distillation has a lower total annualized cost for production rates lower than 5700 tonne/year compared to the continuous counterpart .…”