不同地质成熟度家用燃煤燃烧颗粒物及多环芳烃的排放特征

Emission characteristics of particulate matter and polycyclic aromatic hydrocarbons (PAHs) from residential coal combustion with different geological maturity

选取了7种不同成熟度的原煤,模拟煤炭家用取暖燃烧过程,基于稀释通道采样方法,测定了PM_(2.5)、有机碳(OC)、元素碳(EC)和多环芳烃(PAHs)的排放因子(Emission factors,EFs),分析了原煤自身特征参数与污染物排放因子的关系,并计算了原煤排放PAHs的特征比值.结果表明,地质成熟度高的无烟煤燃烧PM_(2.5)、OC、EC和PAHs的排放因子最低,分别为(0.28±0.07)、(0.07±0.04)、(0.003±0)g·kg^(-1)和(1.15±0.84)mg·kg^(-1).随着地质成熟度的降低,PM_(2.5)、OC、EC和PAHs的排放因子呈波动上升的趋势,具有中等地质成熟度(挥发分为28.08%)的烟煤PM_(2.5)、OC和PAHs的排放因子最高,分别为(5.17±0.33)、(2.50±0.93)g·kg^(-1)、(240.39±180.55)mg·kg^(-1),比地质成熟度高的无烟煤高出1~2个数量级.相关关系分析表明,燃煤的挥发分含量与PM_(2.5)、TC、OC、EC的排放因子呈正相关.燃煤排放PAHs特征比值中,7种燃煤的anthracene/(anthracene+phenanthrene)[Ant/(Ant+Phe)]、benzo[a]anthracene/(benzo[a]anthracene+chrysene)[BaA/(BaA+Chr)]、indeno[1,2,3-cd]pyrene/(indeno[1,2,3-cd]pyrene+benzo[ghi]perylene)[IncdP/(IncdP+BghiP)]的比值分布离散度较大,在进行燃煤源解析时应该谨慎使用.而fluoranthene/(fluoranthene+pyrene)[Fla/(Fla+Pyr)]、benzo[b]fluoranthene/(benzo[b]fluoranthene+benzo[k]fluoranthene)[BbF/(BbF+BkF)]的数值分布较为集中,相对稳定,可以作为燃煤源识别特征,且Fla/(Fla+Pyr)、BbF/(BbF+BkF)随煤地质成熟度降低呈现递减的趋势,与挥发分具有显著的负相关关系,相关系数分别为-0.78(p<0.05)、-0.94(p<0.01).本研究揭示煤的地质成熟度会影响燃烧源PAHs中同分异构体的生成,且成熟度高(挥发分低)的煤在燃烧中更倾向于生成Fla和BbF;这一现象为区分烟煤和无烟煤排放提供了更为有力的证据.

In this study,emission factors(EFs)of PM_(2.5),organic carbon(OC),elemental carbon(EC)and polycyclic aromatic hydrocarbons(PAHs)were determined from simulated combustion of 7 different raw coals with different geological maturity in a combustion chamber equipped with a dilution sampling system.The relationship between raw coal properties and EFs were analyzed,and the diagnostic ratios of PAHs from raw coals were calculated.The results showed that the EFs of PM_(2.5),OC,EC and PAHs from anthracite(the highest geological maturity)were the lowest,which were(0.28±0.07),(0.07±0.04),(0.003±0)g·kg^(-1) and(1.15±0.84)mg·kg^(-1),respectively.With the decrease of geological maturity,the EFs showed a fluctuating upward trend.In detail,the EFs of PM_(2.5),OC and PAHs of bituminous coal with medium geological maturity(28.08%volatile matter)were the highest,with EFs of(5.17±0.33),(2.50±0.93)g·kg^(-1),and(240.39±180.55)mg·kg^(-1),respectively,which were 1 to 2 orders of magnitude higher than those from anthracite.Correlation analysis showed that the volatile content of coal was strongly positive correlated with the EFs of PM_(2.5),TC,OC and EC.Among the diagnostic ratios of PAHs emitted from coal combustion,the ratios of Ant/(Ant+Phe),BaA/(BaA+Chr)and IncdP/(IncdP+BghiP)were discrete,which should be cautiously used in source apportionment.In comparison,the values of Fla/(Fla+Pyr)and BbF/(BbF+BkF)were relatively concentrated and stable,which can be used as the tracers to distinguishing different coal combustion emissions.Fla/(Fla+Pyr)and BbF/(BbF+BkF)showed a downward trend with the decrease of coal geological maturity,and had a significant negative correlation with volatile matter,with correlation coefficients of-0.78(p<0.05)and-0.94(p<0.01),respectively.This study revealed that the geological maturity of coal strongly affects the formation of isomers in PAHs,and the coals with high maturity(low volatiles)tend to form Fla and BbF during combustion.This phenomenon provides more powerful evidence to distinguish emissions between bituminous coal and anthracite coal combustion.