Research on element migration and ash deposition characteristics of high-alkali coal in horizontal liquid slagging cyclone furnace

Abstract Hongshaquan coal (HSQ), a kind of high-alkali and rich-iron coal, is burned in a 20 MW liquid slagging cyclone furnace. The migration and transformation characteristics of elements are examined. The deposition probe and oil cooling circulation system are used to investigate the ash deposition characteristics of HSQ. In addition, the microscopic morphology, crystal structure and chemical composition of the slag are studied to explain the effect of element migration on ash deposition and slag. The results show that the growth process of deposition on probe 1 can be divided into four stages. The final stable relative heat flux of probe 1 and probe 2 is 0.585 and 0.85, respectively. The average concentration of Na2O in ash is 4.53%. Na, K, Ca, Mg and S are enriched in the low temperature area of the boiler to form sulfate which leads to the agglomeration of ash particles. The main mineral phases of the slag are silicates and iron-containing compounds. The average concentration of Fe2O3 in the slag sample is 36.73%. Iron will be enriched in the slag and form a low-temperature eutectic with the silicon-calcium-magnesium–aluminum system to reduce the melting point of the ash. The granulated slag has a lower degree of crystallinity and is closer to the characteristics of glassy slag, which is due to the low content of Na2O, CaO and high silicon-to-aluminum ratio in the ash.