循环流化床锅炉粉煤灰中硫的赋存状态研究

高铝粉煤灰是重要的提取氧化铝的原料,而硫是氧化铝生产中主要有害杂质。以山西朔州地区循环流化床锅炉产生的高铝粉煤灰为研究对象,采用XRF、XRD和SEM-EDS并结合炉前煤分析结果研究了其中硫的赋存状态。研究结果表明,炉前煤中硫含量达到3.77%,以黄铁矿形式存在的无机硫约占总量的50.71%。这种煤经循环流化床锅炉燃烧后,粉煤灰中主要含硫矿物转化为硫酸钙和钙矾石,这与铝土矿中硫的赋存状态显著不同。对比粉煤灰和950℃焙烧后粉煤灰XRD结果表明,钙矾石是在粉煤灰堆存过程中硫酸钙与粉煤灰中的氧化铝、水等进一步水化生成的产物。

Study on Occurrence of Sulfur in Fly Ash from Circulating Fluidized Bed Boiler

The high-alumina fly ash is an important extraction material for alumina and the sulfur is the main harmful impurity during the production course of alumina.Taking high-alumina fly ash producing from the circulation fluidized bed boiler as the research subject,the occurrence of the sulfur in fly ash was studied by XRF,XRD,SEM-EDS together with the feed coal analysis.The results showed that the sulfur content of the feed coal reached 3.77% and the inorganic sulfur approximately accounted for 50.71% of the total in the form of pyrite.After burning in the circulating fluidized bed boiler,the sulfur minerals in fly ash were converted into anhydrite and ettringite,which is remarkably different from the occurrence in the bauxite.According to XRD results of fly ash and the one roasted at the temperature of 950℃,ettringite is deduced to be a kind of product formed by the reaction of anhydrite and active alumina in fly ash during stocking.