Abstract
Abstract Two new processes for synthetic natural gas (SNG) production based on the sorption enhanced steam hydrogasification (SE-SHR) are proposed. Experimental work was conducted on the gasification of coal and biomass feedstocks with a fixed quantity of quicklime as the sorbent. Results showed that SE-SHR can significantly increase H 2 yield beyond the initial H 2 input and minimize CO 2 production. The SE-SHR parametric study was carried out by using lignite as a typical feedstock. By varying hydrogen to carbon molar ratio (H 2 /C) and steam to carbon molar ratio (Steam/C), the product gas composition and yield during SE-SHR and conventional steam hydrogasification (SHR) were obtained. The increase of H 2 /C enhanced the productions of H 2 and CH 4 and decreased the productions of CO and CO 2 . On the other hand, due to the domination of steam gasification reaction, the yields of H 2 , CO and CO 2 were increased with the increase of Steam/C. The new SNG processes include SE-SHR coupled with water gas shift (WGS) and SE-SHR coupled with methanation. The simulation of individual WGS or methanation unit based on the preliminary bench-scale data was conducted using Aspen Plus software to obtain the final SNG composition. Results showed that the SE-SHR-Methanation process results in high CH 4 production with self-sustained H 2 supply and near zero CO 2 emissions. The optimum gasification conditions for this process using lignite were H 2 /C of 1.08 and Steam/C of 2.22. Finally, a preliminary pilot-scale simulation of SE-SHR-Methanation process was conducted based on the predetermined optimum condition to evaluate the overall material and energy balance. It showed that carbon conversion efficiency to CH 4 was as high as 39.8%.
Published Version
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