Emissions of NOx, PM, SO2, and VOCs from Coal-fired Boilers Related to Coal Washing, Iron-steel Production, and Lime and Gypsum Making in Shanxi, China

The accurate pollutant inventories are important for the development of pollution control policies, which further rely on detailed emission factors (EFs) to some extent. However, detailed air pollutant EFs for coal-fired boilers (CFBs) associated with coal washing (CW), iron-steel production (IS), and lime and gypsum manufacturing (LG) are lacking in China at present. CFBs of 91 enterprises involving CW, IS, and LG were investigated to obtain their pollutant EFs associated with coal consumption (EFI, kg t(-1)), outputs (EFII, kg MY-1), and product yields (EFIII, kg t(-1)) through field investigation and sampling. The weak correlation between EFs of 4 air pollutants vs. corresponding removal efficiencies (REs), and EFs vs. coal compositions among three industries implied the impact of actual combustion conditions and operating status of removal facilities (RFs). EFs of VOCs from small-scale CW enterprises (SSEs) were much higher than those of large- and medium-scale enterprises (LSEs and MSEs) owning to the incomplete combustion of coal. Also the SO2 and NOx EFs of CW increased with decreasing enterprise scale, while the maximum PM occurred at MSEs. The mean EFI values of LG for the 4 air pollutants was PM > NOx > VOCs > SO2, differed from PM > SO2 > NOx for the IS, VOCs > PM > NOx > SO2 for the CW LSEs and MSEs, and VOCs > NOx > PM > SO2 for the CW SSEs, which suggested the influence of combined factors including coal composition, production processes, combustion conditions, and pollutant removal technologies and removal efficiencies. EFI values for the 8 IS factories followed the order PM > SO2 > NOx, while they were PM > NOx > SO2 for EFII values due to their output fluctuation. For the EFII and EFIII values of SO2, NOx, and PM, LG dominated within the 3 industries, while the corresponding maximum VOCs occurred at the CW industry.