Highly efficient gas-steam cogeneration method and system based on biomass gasification and methanation

摘要

The present invention provides a gas-steam efficient cogeneration process and system based on biomass gasification and methanation, comprising a biomass gasification unit, a transformation unit, a purification unit, a methanation unit, and a methane concentration unit. The gasification unit utilizes a locally-external constant high-temperature heat source airflow bed which can remarkably improve effective gas compositions of CO and H2 and improve biomass gasification efficiency. The gasification unit can greatly reduce the quantity of tar produced at a high temperature, improves the carbon conversion rate, and removes investment on a tar removing device. In the process of methanation, the conversion efficiency of CO reaches 100%, and the conversion efficiency of H2 reaches 99%. Also, a large amount of by-product intermediate pressure superheated steam is produced, and power consumption of a circulation compressor in the traditional methanation reaction is reduced. The present invention has the advantages that biomass energy can be converted into clean, high-calorific-value, and convenient-for-use natural gas, and a large amount of heat released in the biomass gasification and methanation reaction can be efficiently recycled through a mode of producing high-quality superheated steam.