Research on collaborative control of heavy metals discharge from coal comb- ustion by hybrid particulate collector and wet flue gas desulphurization

Taking a 320 MW unit equipped with hybrid particulate collector ( HPC) and wet flue gas desulfurization (WFGD) as an example,the content of Hg,As,Pb,Cr in flue gas after WFGD was measured by applying the US En- vironment Protection Agency (EPA) method 29,coal and other combustion products were also sampled. The heavy metals enrichment characteristics and removal efficiency of HPC and WFGD were analyzed,and the collaborative con- trol of HPC and WFGD on heavy metals emission under different boiler loads were also compared. The results show that As,Pb,Cr are obviously enriched in fabric filtration ash,but distributed more in electrostatic precipitation ash. Fabric filtration can effectively capture the gaseous mercury in flue gas,the relative enrichment factor of Hg is 1. 01. Hg,As,Pb,Cr in WFGD system all migrate to gypsum in a large scale. The average removal efficiency of As,Pb,Cr by HPC and WFGD are 85% and 82% respectively. The total Hg removal efficiency of HPC is 50% ,while that of WFGD is 91% . Under the load of 75% and 100% ,over 90% of Hg,As,Pb,Cr can be removed by HPC+WFGD. HPC plays a major role in heavy metals emission control,especially under low boiler load.