关键词: 化学热力学平衡计算, 生物质, Cl, 碱金属, 燃烧

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