生物质热解和气化过程Cl及碱金属逸出行为的化学热力学平衡分析

减少生物质在热转化反应器中Cl与碱金属K和Na以气态组元逸出可有效遏制积灰、腐蚀等现象和减少污染气体排放。采用化学热力学平衡分析方法，在400K~1600K研究了秸秆、树皮、木屑、废木和橄榄渣五种生物质在过剩空气系数分别为0、0.4、0.8的热解和气化过程中Cl与碱金属K和Na的赋存形态变化及逸出特性。结果表明，Cl在热解和气化过程中主要是以KCl(s)、HCl(g)、KCl(g)、(KCl)2(g)和NaCl(g)化合物赋存并相互转化；在800K~1000K时，含Cl固态组元逐渐转化为气态组元；K和Na在900K时开始以气态组元逸出，且热解过程有少量KCN(g)和NaCN(g)逸出，而气化过程，温度大于1000K随过剩空气系数的增加，KCl(g)、K(g)和Na(g)等气态组元量逐渐减少，逐渐转化为NaCl(g)、KOH(g)和NaOH(g)；减少Cl和碱金属K和Na逸出的理论最佳热解和气化温度分别为800K和900K。

Release characteristics of chlorine and alkali metals during pyrolysis and gasification of biomass by thermodynamical equilibrium analysis

Reducing formation of gaseous species, which contain chlorine, potassium and sodium, can effectively abate deposit formation, slagging, corrosion and harmful pollutant emission during thermal conversion of biomass fuels. The occurrence modes, transformation routines and release characteristics of those species, especial gaseous species have been investigated by thermodynamical equilibrium analysis technique for 5 biomass fuels, such as straw, bark, woodchips, waste wood and olive residues from 400K~1600K during pyrolysis and gasification with excess air coefficient as 0.4 and 0.8. The calculation results show that chlorine element exists as species of KCl(s), HCl(g), KCl(g), (KCl)2(g) and NaCl(g) for 5 biomass fuels during pyrolysis and gasification. The solid chlorine contained species will be gradually transformed into gaseous when reaction temperature is higher than 800K~1000K. Alkali metal elements, potassium and sodiumin biomass fuels will be released as gaseous species above 900K. A little KCN(g) and NaCN(g) are transformed during pyrolysis. The amount of gaseous species KCl(g), K(g) and Na(g) will decrease and transform into NaCl(g), KOH(g) and NaOH(g) above 1000K during gasification. The optimum gasification temperatures for the lowest gaseous release of species containing chlorine and alkali metal elements are 800K and 900K, respectively. Hence, developing mild temperature gasification technology is an alternative to abate the common problems occurred in biomass gasification reactors.