Study on Greenhouse Gas Emission Characteristics of Fluidized Catalytic Cracking Flue Gas

The regeneration process of fluid catalytic cracking (FCC) units produces amounts of greenhouse gases (GHGs), including carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). However, the flue gas GHG emission characteristics of FCC units are not well understood in China. In our work, three typical FCC units are taken as stack tests for CO2, N2O, and CH4 emissions in the flue gas. The on-site monitoring results show that the regenerated form of the FCC unit has the greatest impact on CH4, and CO2 is the primary GHG, with total emissions of >99%. Meanwhile, the spent catalysts are collected for further characterization and regeneration experiments. Results show that the coke content and composition on the spent catalysts can directly affect GHG emissions. The regeneration experiments of spent catalysts at different oxygen contents show that the main emission temperature ranges of CO2, N2O, and CH4 are 200-600 degrees C, 400-600 degrees C, and 300-600 degrees C, respectively. The peaks of CO2 and N2O content in regenerated flue gas increase as the O2 content increases, while CH4 is generated under oxygen free conditions. The study of the GHG emission characteristics can provide theoretical support for the carbon peaking and carbon neutrality goals.