Abstract: The transformation characteristics of chlorine and alkali metals, such as potassium and sodium, during combustion have been investigated by using thermodynamic equilibrium analysis (TEA) technique for five kinds of biomass residue samples, i.e. straw, bark, wood chips, waste wood and olive residue in the temperature range of 400~1600 K with excess air coefficient of 1.0, 1.2 and 1.4. The TEA results show that changing excess air coefficient can not obviously affect the released amount of chlorine and potassium or sodium. The major gaseous and solid existing species of chlorine, potassium and sodium are found to be KCl(s), HCl(g), KCl(g), (KCl)2(g) and NaCl(g) for five kinds of biomass residues samples studied during the combustion. A great amount of chlorine contained species can be released as gaseous species at the temperatures above 800~1000 K while alkali metals, potassium and sodium can be transformed into the following gaseous species KOH(g), KCl(g), (KCl)2(g), K2SO4(g), Na(g), NaOH(g), Na2SO4(g) and NaCl(g) at temperature above 850 K. Hence, the least release of chlorine, potassium and sodium as gaseous species can be realized at the temperatures less than 850 K in the viewpoint of TEA. As practical biomass combustion reactors are performed far from real thermodynamic equilibrium, the combustion operation temperature of practical reactor can be controlled a bit greater than the critical condition mentioned above.

Key words: thermodynamic equilibrium analysis, biomass, chlorine, alkali metals, combustion

摘要： 采用化学热力学平衡分析方法，研究了秸秆、树皮、木屑、废木和橄榄渣5种生物质在400~1600 K温度范围和空气过剩系数分别为1.0, 1.2和1.4的燃烧条件下Cl及碱金属K和Na的化学平衡组成及浓度，讨论了其排放特性. 结果表明，空气过剩系数对生物质燃烧过程中Cl及碱金属K和Na的逸出影响较小；燃烧过程中含Cl组元主要以KCl(s), HCl(g), KCl(g), (KCl)2(g)和NaCl(g) 5种物质在800~1000 K温度范围进行固-气态转换；当燃烧温度大于850 K时，K和Na碱金属则主要生成KOH(g), KCl(g), (KCl)2(g), K2SO4(g), Na(g), NaOH(g), Na2SO4(g)和NaCl(g). 最大程度减少5种生物质在燃烧过程中含Cl及碱金属K和Na组元的产生和逸出量的最佳反应温度为850 K以下；高于900 K时，Cl及碱金属等气态物质则会大量生成.

关键词: 化学热力学平衡计算, 生物质, Cl, 碱金属, 燃烧