A holistic life cycle evaluation of coking production covering coke oven gas purification process based on the subdivision method

Abstract

The accuracy of life cycle assessment (LCA) results largely depends on data quality. Coking production is a multi-functional system that generally consists of coke-making process and coke oven gas (COG) purification process. Previous LCA studies mainly investigated the overall impacts of coking production without identifying the specific contribution of sub-processes due to lack of enough data. The present study aims to provide a holistic “cradle to gate” LCA on coking production based on the subdivision method. The COG purification process was specially addressed from four sub-processes, including blowing cooler system, sulfur recovery, ammonia recovery and raw benzene recovery. LCA results referred to 1 ton of coke was analyzed by the subdivision method and compared with physical and economic allocation methods. LCA evaluation was performed by five mid-point categories from CML 2001 method combined with three human toxicity categories from IMPACT 2002 + method.The results indicated that COG purification process showed comparable or more significant contribution as coke-making process to the overall life cycle air emissions of coking production. In COG purification process, ammonia recovery and blowing cooler system units were the dominating contributors, mainly attributed to steam usage and electricity consumption in each unit. Compared to physical and economic allocation methods, using subdivision method is more reasonable and accuracy for all the products in coking production. The study helps to better identify the specific environmental hotspots and improvement opportunities for coking industry from a more holistic perspective.