生物质燃烧过程中K元素的迁移特性

Transformation Characteristics of Potassium During Biomass Combustion

在生物质热转化过程中,一部分K元素会进入到气相,造成锅炉高温对流受热面上的积灰结渣和高温腐蚀问题,严重威胁锅炉的安全运行.以自行设计的固定床实验系统研究了典型生物质燃料燃烧过程中K元素的迁移特性,考察了温度、时间和掺混燃烧的影响.结果表明,随着温度的升高,燃料中水溶性K会减少,难溶性K和气相析出K会增加.当温度为700～900,℃时,随着反应时间的增加,小麦秸秆中K元素的析出率逐渐升高,且有一部分醋酸铵溶K和盐酸溶K转化为难溶K,另一部分水溶性K转化为气相K析出.掺混了稻壳后玉米秸秆的灰产率会增大,且在燃烧温度较高时掺混高硅燃料对玉米秸秆中K元素的释放会产生一定影响.

During the thermal conversion process of biomass, a portion of potassium can be released into gas phase, causing serious problems such as fouling, slagging and high-temperature corrosion on convective heating surfaces. These problems are harmful to the safety of biomass boilers. In this paper, the potassium transformation during the combustion of biomass is studied in a fixed-bed experimental system. The effects of combustion temperature, reaction time and cofiring are discussed. The results indicate that as the temperature increases, the watersoluble K in the biomass decreases, whereas the insoluble and gas phase K increase. Within the temperature range of 700-900 °C, a longer reaction time facilitates the potassium release of corn stalk. Besides, part of the ammonium acetate dissolved K and hydrochloric acid dissolved K transform into insoluble K, and part of the water-soluble K transforms into gas phase K. And under high combustion temperature, the mixed husk will increase the ash yield and significantly reduce the gas phase precipitation of K in corn stalk.