Emission pathways and reduction strategies of greenhouse gases in coal chemical industry: A review

Anthropogenic greenhouse gases (GHGs) emission, an important role for chemical industrial sources, contributes to the global warming. Coal chemical industry (CCI), one of the mainstays of the chemical industry, is one of major sources of GHGs emission. However, GHGs emission pathways and reduction strategies from CCI remains uncertain, owing to the complexity of their production process. This review comprehensively investigated the generation processes and control measures for GHGs emission in CCI process. According to the different ways of primary conversion processes, CCI divided into three major processes, i.e., coal coking, coal gasification, and coal liquefaction. The coking industry accounts for 60 %-70 % of carbon dioxide (CO2) emissions in the CCI, with fuel combustion accounting for 80 %-90 % of its largest contribution. In the coal gasification (i.e., coal to methanol) and liquefaction (i.e., coal to oil) sectors, the water gas shift, air separation, and coal gasification units represent the main contribution pathways for CO2, accounting for 53 %, 25 %, and 22 % in the whole process, respectively. In addition, the adjustment of the H/C in the syngas produced CO2 in water gas shift unit, and the incomplete combustion of fuel leads to CO2 emissions from air separation and coal gasification units. Furthermore, investigation of various reduction technologies shows that capture or sequestration alone could not provide economic benefits. Therefore, future reduction strategies of CCI CO2 need to focus on resource utilization in the production process. This review provides references for addressing the abatement of GHGs, contributing to mitigate its contribution to global warming.