Emission Characteristics and Formation Pathways of PCDD/Fs from Cocombustion of Municipal Solid Waste in a Large-Scale Coal-Fired Power Plant

摘要

This study is based on a 300 MW coal-fired power plant cocombusting 2% of MSW, focusing on the emission characteristics and formation pathway of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Data from two scenarios, including the cocombustion test (CCT) and normal operation conditions (NOCs), are comprehensively analyzed, indicating that the TEQ concentration of PCDD/Fs increases by 12.69% during cocombustion but still satisfied the national emission limits. The purification efficiencies of toxic PCCD/Fs in CCT and NOC are 41.28 and 28.33%, respectively. Following this, major air pollutant emissions could also satisfy the national standard and even meet the zero-emission requirement. For flue gas in both CCT and NOC, 1,2,3,4,6,7,8-HpCDD, OCDD, 2,3,4,6,7,8-HxCDF, and 1,2,3,4,6,7,8-HpCDF are the main contributors to 2,3,7,8-PCDD/Fs on the mass concentration level, while OCDD and OCDF dominate in fly ash. The major difference is that the CCT condition has a higher fraction of 1,2,3,4,6,7,8-HpCDD, OCDD, and lower contents of 2,3,4,6,7,8-HxCDF to NOC. Furthermore, the distribution of integral 136 PCDD/F congeners also show infinite variation between CCT and NOC, but with a huge gap in the quantity of different isomers. However, cocombustion affects the potential formation routes, as PCDD/Fs from de novo synthesis and DD chlorination dominate the formation pathways in NOC. In contrast, PCDD/Fs from the CP-route of precursor synthesis are mostly occupied under NOCs, possibly due to the incineration deterioration caused by MSW that generates more precursors. Additionally, there is little correlation with a mutual Pearson correlation coefficient (R-2) of 0.2474 between HCl and PCDD/Fs in the flue gas, indicating the lessened influence of high-temperature gaseous synthesis by imported MSW.