Process Simulation of Syngas Purification by Gas Permeation Application

Nowadays, syngas production from renewable energy sources particularly by methanation process has taken great interest. The aim of the process is energy saving by converting surplus produced energy into a truthful chemical product. Methanation reactor outlet stream contains a gas mixture which is not feasible to be used directly in distributing grids, where a higher purity of methane is necessary to obtain the highest power density. To reach the different grades of methane (for heat, electricity and vehicle fuels applications), various purification levels should be provided for syngas. For use as a fuel, elimination of carbon dioxide and water is needed, because water affects negatively on the mechanical components within the vehicles’ engine equipment. Moreover, CO2 removal should be carried out to enhance heat quality of methane and cause less pollution in the atmosphere. In the current study, the performance of a combination of flash separator and hollow fiber membranes for syngas purification was studied. For this purpose, a flash separator model was implemented to condense water from the wet feed. Then for the elimination of CO2 from methane, a hollow fiber membrane system was considered. Therefore, a unit operation user model in FORTRAN was developed to incorporate into Aspen Plus® V8.6. Different designs and arrangements of membrane modules were compared, and the best result was to purify methane up to 98 %vol. obtained using a two-stage gas permeation system with recycle streams. The model scheme can be beneficial in the design and performance analysis of a complex methanation plant system prior to practical realization.