Life cycle environmental analysis of coke oven gas to liquefied natural gas based on decarburization and methanation processes
As a by-product in coking production,coke oven gas(COG)has been widely utilized for liquefied natural gas(LNG)production due to rich in H2 and CH4.To systematically evaluate the energy depletion and environmental impacts,as well as the carbon emission,life cycle assessment(LCA)method was applied to compare two COG-based LNG processes(decarbonization process and methanation process).The results show that LNG production is the crucial phase in the overall environmental impacts for both COG-based LNG processes.In decarbonization process,medium-pressure steam is the main contributing substance of life cycle environmental impacts.Recovering the waste heat of red coke by coke dry quenching system and supplementing LNG production consumption with by-product steam can largely reduce environmental loading.In methanation process,electricity is the key substance,accounting for 41.09%in carbon emission index.The environmental impact can be reduced by using renewable electricity(solar,hydroelectric and wind).Methanation process shows favorable environmental performance in comparison with decarbonization process because methanation process largely enhances the CH4 productivity.This work intends to provide theoretical support for the comprehensive utilization of COG in the coking industry from the life cycle perspective.