生物质混煤燃烧过程中钾的迁移转化规律

Migration and transformation law of potassium in the combustion of biomass blended coal

通过将稻秆和褐煤混燃,研究了燃烧温度以及生物质掺混比例对于混燃过程中K的释放、灰样中K的赋存形式以及矿物质变化的影响。研究表明,燃烧温度对于混合燃料中K的释放影响显著。在600-750℃时,随着温度升高,水溶性K和醋酸铵溶性K大量释放到气相,使得K的释放速率较快;而当温度在750-850℃时,水溶性K和醋酸铵溶性K开始大量地转化为其他形式的K而被固定在灰样中,使得K的释放速率变得缓慢;当温度高于850℃时,随着温度升高,盐酸溶性K的分解导致K释放速率重新增大。通过XRD分析发现,灰样中水溶性K主要以KCl的形式存在,K 2SO 4的生成同时受到原料中K的含量和S/Cl比值两个因素的共同影响,原料中K的含量越高,且S/Cl比值越大,越会促进K 2SO 4的生成。同时也发现生物质和煤混燃时存在协同作用,煤中Al、Si等元素会和生物质中的K反应生成碱性硅铝酸盐,从而导致更多K留在灰烬中。

The effects of combustion temperature and biomass blending ratio on the release of K,the occurrence form of K in the ash and the change of mineral matter were studied.It is found that combustion temperature has a significant effect on the release of K.At 600-750℃,with an increase in temperature,water-soluble K and NH 4Ac-soluble K are released to the gas phase,which makes the release ratio of K fast;while at 750-850℃,water-soluble K and NH 4Ac-soluble K begin to convert into other forms of K and are fixed in the ash sample,which makes the release rate of K slow;when the temperature is higher than 850℃,as the temperature increases,the decomposition of HCl-soluble K causes the release rate of K increase again.Through XRD analysis,it is found that the water-soluble K in ash mainly exists in the form of KCl.The production of K 2SO 4 is affected by both the K content in the raw material and the S/Cl ratio,the higher the content of K in raw materials,and the greater the ratio of S/Cl,the more it will promote the formation of K 2SO 4.At the same time,it is also found that there is a synergistic effect between biomass and coal combustion.The elements such as Al,Si in coal may react with K in biomass to generate alkaline aluminosilicate,resulting in more K remaining in the ash.