Emission Factors of NO_x, SO₂, and PM for Bathing, Heating, Power Generation, Coking, and Cement Industries in Shanxi, China: Based on Field Measurement

摘要

Despite rapid development in China, small-scale boilers (SCBs) still occupy a prominent place in industry. Due to the lack of pollutant removal devices (RDs), SCBs emit large quantities of pollutants, which merit increased attention. In this study, various SCBs (operating on coal, gangue, coke oven gas, coal gas, and natural gas) used in bathing, heating, power generation, and coke and cement making were investigated for their SO_(2), NO_(x), and PM emission factors (EFs). The EFs were expressed as the emitted pollutant mass associated with fuel consumption (EFI), product yield (EFII), industrial output (EFIII), and power generation (EFIV). Of 17 civil SCBs, 4, 14, and 10 were not equipped with PM, NO_(x), and SO_(2) RDs, respectively. Generally, the EFI values for all of the SCBs decreased with increasing coal consumption. The averaged NO_(x) EFI value for the 3 SCBs with installed NO_(x) RDs was 2.00 kg t~(–1) versus 3.16 kg t~(–1) for the 17 SCBs. The sulfur content of the coal and the SO_(2) removal rate were highly influential factors for the SO_(2) EFI values. The 4 SCBs without PM RDs possessed an average EFI value of 23.9 kg t~(–1), which was higher than the corresponding 5.41 kg t~(–1) for the 13 boilers equipped with PM RDs. The EFI, EFII, and EFIV values for 9 coal-fired power plants (PPs) exhibited the same trends, decreasing as the capacity of the PPs increased from 6 to 330 MW, although slightly higher EFs were found for 600 MW plants compared to 330 MW plants. The gas-fired PPs possessed higher NO_(x) EFs than both the coal- and gangue-fired plants, and the gangue-fired PPs displayed significantly higher EFs than coal-fired PPs with the same individual block power capacity. Because flue gas produced in the coking factories was not fully emitted during the combustion process, no correlation existed between the EFs (expressed as EFII and EFIII) and coke production or industrial output. Moreover, due to the lack of NO_(x) RDs, the EFs of NO_(x) were higher than those of SO_(2) and PM in the coking industry. Among 6 small- and medium-sized cement companies, the factories with lower cement production possessed higher EFI values for PM. A reverse trend was exhibited by the NO_(x) EFI, however, with high combustion temperatures at factories with high production being the possible explanation.