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

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 NH₄Ac-soluble K are released to the gas phase, which makes the release ratio of K fast; while at 750-850℃, water-soluble K and NH₄Ac-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 K₂SO₄ 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 K₂SO₄. 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.