高碱煤燃烧过程中结渣机理研究进展

Research Progress on Slagging Mechanism During High Alkali Coal Combustion Process

总结了高碱煤燃烧过程中结渣机理的研究现状,概述了高碱煤中碱金属的赋存形式及其在燃烧过程中的演变规律与高碱煤燃烧过程中的结渣机理.煤中赋存的碱金属化合物在燃烧过程中与烟气中的其他化合物反应生成气态的碱金属原子、碱金属硫酸盐、碱金属碳酸盐、碱金属氯化物、碱金属氢氧化物及固态或熔融态的含碱金属矿物质.硫酸钠及硫酸钙在受热面表面形成内白层并捕获烟气中灰颗粒,与之反应生成低熔点化合物,促进渣层的生长.硫酸钠及硫酸钙亦可在固态或熔融态的灰颗粒表面形成液态黏性的涂层.这种带有涂层的颗粒与烟气中含铁矿物质的颗粒加剧了结渣的形成.结合高碱煤结渣的特点,概述了高碱煤的结渣防治技术.

A review of the previous research on the mechanism for slagging during the high alkali coal combustion was presented.The occurrence modes of the sodium contained in the high alkali coal and the conversion rule of the sodium during the high alkali coal combustion was summarized as follows:during coal combustion process,alkali metals are released and transported either in the form of solid particles or vapor species in the combustion gas.The main occurrence modes of alkali metals in solid particles is,A-silicates and A-aluminosilicates(A represents K and Na),and the main occurrence modes of alkali vapor species is A(g),ACl(g),A_2CO_3(g),A_2SO_4(g),and AOH(g).The slagging mechanism caused during the high alkali coal combustion process can be illustrated as follows:the vaporized Na_2SO_4 and CaSO_4 at high temperature will condense on heating surface and form an initial sticky slagging layer as an adhesive that bonds the subsequent deposits and heating surfaces together and the condensed Na_2SO_4 and CaSO_4 react with the subsequent deposits from low melting point chemical compounds to promote growth of slagging.Furthermore,coating particles due to the condensation of the vaporized Na_2SO_4 and CaSO_4 at high temperature on grain boundary and iron-bearing minerals promote growth of slagging.The mode of boiler slagging prediction and the current control technologies for the high sodium coal slagging were briefly introduced and some potentially promising research topics on the slagging mechanism of the high alkali coal were discussed.