Life cycle assessment of ammonia synthesis based on pulverized coal entrained flow gasification technology in China

The ammonia-synthesis industry has become a research hotspot, because its high energy consumption and CO2 emission exacerbate the current resource shortages and environmental pressures. However, the current research on life cycle assessment (LCA) of synthetic ammonia in China is limited. To fill gaps, this study analyzed the environmental performance of mainstream ammonia synthesis in China, i.e., pulverized coal entrained flow gasification (PEF) technology, based on LCA method. Results showed that the potential environmental impact on fossil depletion category was the main contributor to the overall environmental burden, which was primarily from coal mining and coal washing (85.3%). Global warming also had an indispensable impact on the overall environmental burden, and electricity was a dominant contributor with a proportion of 36.3%. Compared with anthracite fixed bed gasification (AFB) technology, PEF technology showed superiority in reducing the environmental burden, especially in the categories of global warming, freshwater ecotoxicity, and water depletion. Ammonia-synthesis routes based on the “green hydrogen” and “blue hydrogen” can greatly reduce carbon emission compared with the “grey hydrogen” route, with reduction ratios of 90.9% and 42.9%, respectively. Results further indicated that “green hydrogen” and “blue hydrogen” routes had huge prospects for environmental optimization in China's synthetic ammonia market. Green mining, underground coal washing technology, and renewable electricity substitution can effectively reduce the environmental burden throughout the entire life cycle of ammonia synthesis.