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

Tao Yue,Yali Tong,Kun Wang,Jiajia Gao,Xiaoxi Zhang,Penglai Zuo,Quanming Liang,Chenlong Wang,Li Tong

doi:10.4209/aaqr.2019.10.0531

Abstract

ABSTRACT 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 × 10–1 kg t–1 and 4.9 × 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.

Highlights

Coal-fired industrial boilers are the general power equipment in China and the important consumers of coal, consuming about 700 million tons of coal, which accounted for 13.5% of the total coal consumption in China in 2015 (NBS, 2016)
Environmental statistics showed that only 19% and 1.4% of coal-fired industrial boilers were equipped with denitrification devices and flue gas desulfurization (FGD) devices by the end of 2015 in China (NEMC, 2016)
By 2015, GF boilers and circulating fluidized-bed (CFB) boilers accounted for 69% and 21% of the capacity in coal-fired industrial boilers, respectively (NEMC, 2016), where CFB boilers had been rapidly developed since the 1960s in China as a clean boiler type for SO2 and NOx emission control (Duan et al, 2012)

Summary

Introduction

Coal-fired industrial boilers are the general power equipment in China and the important consumers of coal, consuming about 700 million tons of coal, which accounted for 13.5% of the total coal consumption in China in 2015 (NBS, 2016). The emission of PM, SO2 and NOx from coal-fired industrial boilers were 1.6 million tons, 7.2 million tons and 2.7 million tons in 2011, respectively, which is responsible for releasing large quantities of primary air pollutants and trace elements into the atmosphere (MEP, 2011, 2013; Zhao et al, 2010; Tian et al, 2015, 2018). By 2015, GF boilers (chain grate-fired boilers, stokerfired boilers and other grate-fired boilers) and CFB boilers accounted for 69% and 21% of the capacity in coal-fired industrial boilers, respectively (NEMC, 2016), where CFB boilers had been rapidly developed since the 1960s in China as a clean boiler type for SO2 and NOx emission control (Duan et al, 2012)

Methods

Results

Conclusion