准东煤掺烧高岭土对固钠率及灰熔融特性影响研究

Influence of kaolin on sodium retention and ash fusion characteristic during combustion of Zhundong coal

选择常见的黏土矿物高岭土作为准东煤添加剂掺烧,研究了不同掺混比例、不同燃烧温度下添加剂的固钠率和煤灰熔融特性的变化,结合XRD谱图和三元相图研究了灰中矿物在高温下的演变过程。结果表明,固钠率随高岭土掺混比例增加逐渐增大,在0～2%时增长较快,2%～5%增长较慢,随燃烧温度升高略微下降;掺混后煤灰熔点随掺混比例先缓慢减小,再快速减小,后快速增加,在3%时达到1 200℃左右;XRD和三元相图分析结果表明,煤灰熔融特性变化是由于灰中硅钙石、钙黄长石和钙长石矿物比例的变化引起,发生低温共熔现象是导致掺混比例为3%和4%时煤灰熔点最低的主要原因;当掺混比例为2%时,固钠率在60%以上且灰熔点在1 300℃左右,利于固态排渣,当掺混比例为3.0%～4.0%时,灰熔点在1 200℃左右,利于液体排渣。

The common clay mineral of kaolin was selected as an additive into Zhundong coal during combustion. Sodium retention rates and coal ash fusion temperatures were investigated at different blending ratios and temperatures. XRD and ternary phase diagram were used to identify mineral transformations at high temperatures. The results showthat the sodium retention rates increase rapidly with blending ratio from 0 ～ 2%,slowly from 2% ～ 5% and decrease slightly with increasing temperature. The ash fusion temperatures of coal blended with additive initially decrease slowly,then decrease rapidly and finally increase with increasing blending ratio,reaching about 1 200 ℃ at 3%. The results of XRD and ternary phase diagram analysis showthat the change of ash fusion temperature is due to the mineral content changes of rankinite,gehlenite and anorthite. The lowest ash fusion temperatures at the blending ratios of 3% and 4% are mainly caused by the lowtemperature eutectic phenomenon. The sodium retention rate reaches more than 60% and ash fusion temperature reaches about 1 300 ℃ at blending ratio of 2%,which is conductive to solid-state slag-tap boiler. The ash fusion temperature is about 1 200 ℃ at blending ratio of 3. 0 ～ 4. 0%,which is suitable for liquid-state slag-tap boiler.