Measure-specific environmental benefits of air pollution control for coal-fired industrial boilers in China from 2015 to 2017

From 2015 to 2017, China took strong air pollution control measures (APCMs) for coal-fired industrial boilers (CFIBs), including eliminating CFIBs, promoting clean fuels, and updating air pollution control devices (APCDs). Based on the industrial boiler’s emission inventory of air pollutants, measure-specific emission reductions from 2015 to 2017 was estimated in this study. Besides, the measure-specific environmental benefits of unit emission reduction on concentration and deposition flux were systematically evaluated by WRF-CMAQ model. The total emission reductions for CFIBs of PM₁₀, PM₂.₅, SO₂, NOx, Hg, As, Cd, Cr and Pb from 2015 to 2017 were 1.2 Tg, 0.53 Tg, 2.06 Tg, 0.65 Tg, 37.6 tons, 179.5 tons, 17.9 tons, 1029.3 tons and 676.0 tons, respectively. Based on meteorological fields in 2017, their corresponding national population-weighted mitigated concentration was 1.8 μg m⁻³, 1.3 μg m⁻³, 3.6 μg m⁻³, 0.6 μg m⁻³ (NO₂), 0.076 ng m⁻³, 0.37 ng m⁻³, 0.04 ng m⁻³, 1.83 ng m⁻³ and 2.3 ng m⁻³, respectively. Updating APCDs was identified as the major measure to reduce air pollutants (except NOₓ), accounting for more than 35% of emission reductions and mitigated concentration. Moreover, elimination was the major NOx reduction method, contributing to 55% of NOx emission reductions. The promoting of fuels, including replacement of CFIBs with gas-fired and biomass-fired industrial boilers, had higher environmental benefits for unit emission reductions. Furthermore, there were still more than 43,000 CFIBs with the capacity <10 t h⁻¹, accounting for 14%, 21%, and 11% of total PM₂.₅, SO₂, and NOX emissions for CFIBs in 2017; meanwhile, 20% and 59% of CFIBs did not install flue gas desulfurization and denitrification devices, respectively. Therefore, it is recommended to give priority to phase out CFIBs with capacity <10 t h⁻¹ and APCDs updating for larger capacity CFIBs in the future.