生物质燃烧过程中碱金属的结晶行为

摘要

首先对生物质燃烧过程中钾/氯/硫元素的迁移规律进行了实验研究,然后探索了纯氯化钾蒸气及生物质挥发相在不同壁温表面的结晶行为.结果表明,生物质燃烧过程中钾元素的释放量最大可达总量的 93%,,,氯元素在815,℃可完全挥发,而硫元素在 1,100,℃下可基本实现脱除;纯氯化钾高温蒸气,在不同壁温(400,℃、520,℃、600,℃)表面主要以冷凝沉积与熔融两种机制粘附,当壁温为 520,℃时,壁面还会生成枝晶状氯化钾晶体,其结晶速率为 7.2×10-5,g/min,高于壁温为 400,℃时的结晶速率 4.97×10-5,g/min;而生物质在低温(≤500,℃)燃烧过程中,冷却壁面均未发现含钾类物质,但当燃烧温度升至 800,℃时,壁面明显检测到氯化钾晶体,其在不同壁温表面的粘附机制与纯氯化钾蒸气相同.%Based on the release characteristics of potassium,chlorine and sulfur during biomass combustion,the condensing behavior of pure potassium chloride vapors and alkali salt vapors from biomass under different wall tem-perature was studied in laboratory.The results showed that the total release of potassium could reach 93%,while chlorine and sulfur were almost completely removed from biomass when the temperature exceeded 815,℃ and 1,100,℃,respectively.The pure potassium chloride vapors adhered to the substrate surface of different temperature(400,℃,520,℃ and 600,℃)through two mechanisms,including condensation to deposition and fusion to adhesion.The depositing rate of pure potassium chloride vapors on the substrate surface of 520,℃ was 7.2×10-5,g/min,with the appearance of elongate crystals like dendrites,significantly higher than that of 4.97×10-5,g/min of pure potassium chlorine vapors on the substrate surface of 400,℃.The matter containing potassium was not found on the surface dur-ing low temperature combustion.But the potassium chloride crystals could be found when the combustion temperature exceeded 800,℃,whose sticking mechanism is the same as that of pure potassium chloride vapors.