燃煤锅炉颗粒物化学组成排放特征

本研究收集了兰州市不同吨位燃煤锅炉颗粒物排放样品,分析并评估了锅炉烟气中水溶性无机离子、碳质组分、水溶性有机物(WSOC)以及多环芳烃(PAHs)的排放水平、排放特征及其影响因素.结果表明,SO_4~(2-)、Cl~-和Ca~(2+)是燃煤锅炉样品中最主要的水溶性离子,分别占水溶性离子总和的35. 13%、23. 16%和22. 20%.不同吨位燃煤锅炉样品的OCEC及其热解成分谱较为相似,OC1、OC2、OC3、OC4、EC1、EC2和EC3分别占TC的1. 04%、8. 26%、20. 09%、6. 78%、51. 08%、7. 09%和5. 66%,其中EC1的含量最高,是最主要的碳质组分. WSOC/TC和WSOC/OC分别为0. 09±0. 07和0. 23±0. 12,且不同吨位锅炉之间差异较大.菲(Phe)、芘(Pyr)和苯并(k)荧蒽(Bk F)是PAHs的3个主要成分,分别占PAHs总和的16. 69%、11. 93%和10. 66%.不同吨位燃煤锅炉所排放颗粒物中水溶性离子、OCEC以及WSOC均与锅炉吨位大小无明显线性相关,随着吨位的增加PAHs轻组分含量减小.

Emission Characteristics of Chemical Composition of Particulate Matter from Coal-fired Boilers

Samples of particulate matter from coal-fired boilers of different tons were collected in Lanzhou city, and the water-soluble inorganic ions, carbonaceous species, water-soluble organic compounds (WSOC) and polycyclic aromatic hydrocarbons (PAHs) were analyzed. The results showed that SO₄^2-, Cl^-, and Ca²⁺ were the most important water-soluble ions in the coal-fired boiler samples, accounting for 35.13%, 23.16%, and 22.20% of the total mass of water-soluble ions, respectively. The pyrolysis composition spectra of the carbonaceous species were similar among the coal-fired boilers, and organic carbon fraction (OC1, OC2, OC3, and OC4),and elemental carbon fraction (EC1, EC2, and EC3) accounted for 1.04%, 8.26%, 20.09%, 6.78%, 51.08%, 7.09%, and 5.66% of the total carbon (TC), respectively. EC1 had the highest content and was the most important carbonaceous species. The average ratios of WSOC/TC and WSOC/OC were 0.09±0.07 and 0.23±0.12, respectively, and the difference among the boilers of different tons was large. Phenanthrene (Phe), pyrene (Pyr), and benzene(k)anthracene (BkF) were the three main components of the PAHs, accounting for 16.69%, 11.93%, and 10.66% of the total PAHs, respectively. The particulate water-soluble ions, organic/elemental carbon aerosol (OCEC) and WSOC emitted from different tons coal-fired boilers were not significantly linearly related to the tonnage of the steam boiler, and low molecular weight PAHs decreased with the increase of tonnage of the steam boiler.