作为焦化生产中丰富的富H2副产物,焦炉煤气(COG)是生产氨的有利原料。最近,已经应用了三种基于COG的氨工艺,包括单个过程,氨与甲醇联产,氨与液化天然气(LNG)联产。为了系统地评估三条COG路线的环境影响,使用工业数据进行了比较生命周期评估。此外,讨论了氨合成压力和电源对总LCA结果的影响。结果表明,基于COG的单一氨路线对环境的影响主要来自氨生产阶段,占总体归一化结果的69.63%,其中电力和COG是主要贡献者。因此,利用风能等可再生能源的电力,太阳能,水电和核能可以大大减轻对环境的影响,大多数环境指标减少36.3%-70.7%。情景分析证明,将合成压力从31.4MPa降低到15MPa并没有显示出预期的显着环境效益,因为较高的压力更有利于氨合成。与煤基和天然气基氨路线相比,COG航线具有明显的节能效益。在三种基于COG的氨路线中,由于资源和能源的高效利用,这两条联合生产路线占单一生产能源消耗的49.1%和78.6%。与甲醇路线共同生产氨的环境性能优于与LNG路线共同生产氨的环境性能。因此,在COG制氨工艺中,用甲醇路线联产氨更有利。本研究旨在通过生命周期方面为COG利用和氨生产选择提供有价值的参考。
As an abundant H2-rich byproduct from coking production, coke oven gas (COG) is a favorable feedstock for ammonia production. Recently, three COG-based ammonia processes have been applied, including single process,
coproduction of ammonia with methanol, and
coproduction of ammonia with liquefied natural gas (LNG). To systematically evaluate the environmental impacts of three COG routes, a comparative life cycle assessment was conducted with industrial data. Besides, the effects of ammonia synthesis pressure and electricity sources to the total LCA result were discussed. The results indicate that the environmental impacts of COG-based single ammonia route are mainly generated from ammonia production stage, accounting for 69.63 % of the overall normalized results, in which electricity and COG are the dominated contributors. Therefore, employing electricity from renewables like wind, solar, hydro and nuclear could dramatically mitigate the environmental impacts with a reduction of 36.3 %-70.7 % in most environmental indicators. Scenario analysis proves that reducing synthesis pressure from 31.4 MPa to 15 MPa does not show remarkable environmental benefits as expected since higher pressure is more conducive to ammonia synthesis. In comparison with coal based and natural gas-based ammonia routes, COG routes have obvious energy-saving benefit. In three COG-based ammonia routes, the two
coproduction routes accounted for 49.1 % and 78.6 % of the energy depletion as single production due to highly efficient utilization of resources and energy.
Coproduction of ammonia with methanol route exhibits better environmental performance than these in
coproduction of ammonia with LNG route. Therefore,
coproduction of ammonia with methanol route is more favorable in COG to ammonia processes. This study intends to provide a valuable reference for COG utilization and ammonia production options through the life cycle aspect.