Abstract:

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.

Key words: coke oven gas (COG), liquefied natural gas (LNG), life cycle assessment (LCA), environmental impacts, carbon emission

摘要：

作为焦化副产品，焦炉煤气富含氢气和甲烷，采用焦炉煤气制液化天然气（LNG）已成为当前焦炉煤气利用的主要途径之一。为系统评估焦炉煤气制LNG工艺的能源消耗和环境影响，尤其是碳排放，本文采用生命周期评价方法对脱碳法和甲烷化法两种焦炉煤气制LNG工艺进行系统评价。结果表明，无论采用哪种方法，LNG生产阶段均为焦炉煤气制LNG工艺生命周期环境负荷的控制阶段；在脱碳法工艺中，中压蒸汽是环境影响贡献的关键物质，可通过干熄焦回收红焦余热副产蒸汽补充LNG生产消耗来降低环境负荷；在甲烷化工艺中，电力为主要贡献物质，在碳排放中占比41.09%，若采用可再生能源电力（太阳能发电、风电、水电）替代后环境影响显著降低；相比于脱碳法，采用甲烷化工艺环境性能更优，主要源于甲烷增产优势。本文研究结果可从生命周期角度为焦化行业焦炉煤气的综合利用提供理论支持。

关键词: 焦炉煤气, 液化天然气, 生命周期评价, 环境影响, 碳排放