Emission Characteristics of Hazardous Atmospheric Pollutants from Ultra-low Emission Coal-fired Industrial Boilers in China

This study comprehensively investigated the emission characteristics of primary air pollutants (PM, SO2 and NOx) and trace elements (As, Cd, Cr, Hg and Pb) from twelve coal-fired industrial boilers, nine of which were ultra-low emission (ULE) and three of which were non-ULE, based on field measurements. The concentrations, release ratios and relative enrichment factors (REFs) of the trace elements in both the coal and the bottom ash were obtained. Furthermore, the influence of atmospheric pollutant control devices (APCDs) on the emission concentrations and emission factors (EFs) of these pollutants and elements, as well as on their removal efficiencies, was analyzed. The average release ratios for Hg, Cr, Pb and As from the coal were 96.28%, 59.95%, 65.34% and 84.85%, respectively, whereas the average overall removal efficiencies for PM, SO2, NOx, Hg, Cr, Pb and As with the APCD configurations of the ULE coal-fired industrial boilers were 99.5%, 95.9%, 81.0%, 95.6%, 95.6%, 99.3% and 96.0%, respectively. Using selective non-catalytic reduction (SNCR), and a hybrid of selective non-catalytic reduction and selective catalytic reduction (SNCR-SCR) in the ULE boilers, the EFs of the NOx were 5.5 x 10(-1) kg t(-1) and 4.9 x 10(-1) kg t(-1), respectively. Overall, the removal efficiencies for NOx and Hg were 2.1 and 2.8 times higher, respectively, with the ULE than the non-ULE coal-fired industrial boilers, which was mainly attributable to the higher denitrification efficiency, higher dedusting efficiency and higher liquid/gas (L/G) desulfurization ratio of the ULE boilers.