Species distribution of As, Se and Pb in coal-fired flue gas and influence of elements S and Cl on them
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摘要: 基于化学热力学平衡分析方法,计算分析了燃煤烟气中重金属As、Se、Pb的形态分布规律,研究了S、Cl等元素对As、Se、Pb的形态分布规律的影响。结果表明,氧化性气氛下,As以As2O5、As4O6、AsO等氧化物的形式存在;Se主要以SeO2形式存在;Pb在1000 K以下主要是固态PbSO4,1200 K以上为气态PbO。还原性气氛下,As在较低温度时为固态As2S2,900-1400 K以As2、AsS、AsN气体共存,2000 K以上全部转化为气态AsO。Se在1100 K以下主要以气态H2Se存在,1100 K开始生成SeS和Se2气体,1800 K时主要是气态Se和少量气态SeO;Pb在中低温时主要是PbS,1800 K以上气态Pb为主要存在形态。S在还原性气氛下增大了AsS(g)、PbS(g)、SeS(g)的比例,氧化性气氛下对As、Se、Pb形态分布基本无影响;Cl无论在氧化还是还原气氛下对As、Se影响均较小,但对Pb的形态分布影响较大。Abstract: Based on chemical thermodynamics equilibrium analysis, species distribution of As, Se and Pb in coal-fired flue gas was calculated and analyzed, and effect of S, Cl on them was studied. The results show that As exists in the form of As2O5, As4O6 and AsO in oxidizing atmosphere, Se mainly exists in the form of SeO2, and Pb is mainly solid PbSO4 below 1000 K and gaseous PbO above 1200 K. In reducing atmosphere, As is solid As2S2 at lower temperature; As2, AsS and AsN coexist at 900-1400 K, and all of As is changed into gas AsO above 2000 K. Se exists mainly as gaseous H2Se below 1100 K, SeS and Se2 are generated at 1100 K, gaseous Se and a small amount of gaseous SeO at 1800 K. Pb mainly exists as PbS and gaseous Pb above 1800 K at middle and low temperature. The ratio of AsS(g), PbS(g) and SeS(g) increases in the reducing atmosphere, but the distribution of As, Se and Pb is not affected in the oxidizing atmosphere. Cl has little effect on As and Se in both oxidizing and reducing atmosphere, but has a great influence on species distribution of Pb.
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Key words:
- coal-fired flue gas /
- chemical thermodynamic equilibrium calculation /
- As /
- Se /
- Pb /
- speciation distribution
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表 1 输入煤初始条件
Table 1 Initial condition of coal input
Element C H O N S Cl As Se Pb Quantity/mol 64.04 37.5 176.35 659.2 0.178 0.845×10-3 3.19×10-3 7.06×10-3 5.22×10-3 Content 76.85% 3.75% 2.20% 1.37% 0.57% 30 μg/g 2.39 μg/g 5.58 μg/g 10.81 μg/g -
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