Proposal and energy saving analysis of novel methanol-electricity polygeneration system based on staged coal gasification method

摘要

The coal gasification process is one of the main exergy destruction contributors in polygeneration systems and has considerable energy saving potential. In the present study, for improving the performance of the poly generation system, the coal-steam gasification method was employed to integrate a novel methanol-electricity polygeneration system. The results indicated that the energy efficiency of the novel system was 63.3% with a chemical-to-power output ratio of 8.4, while the energy efficiency of the traditional system is 51.3% at the optimal unreacted syngas recycling ratio. Exergy analysis results revealed that the system exergy destruction in the coal?steam gasification process is 7.5% smaller than that in the GE gasification process, and eliminating the air separation unit can reduce the exergy destruction of the system by 4.3%. Additionally, the energy saving contributions of gasification process improvement and system integration were quantitatively evaluated. When the chemical-to-power output ratio increased from 1.9 to 11.9, the energy saving contributions of the system integration and gasification process improvement ranged from 9.8% to 15.1% and 11.9% to 12.9%, respectively.