准东煤燃烧过程中碱金属迁移规律

Migration law of alkali metals during Zhundong coal combustion

由于准东矿区地域宽阔,不同地区的准东煤性质存在一定差异。为了探求某准东煤的结渣沾污机理,在卧式管式炉及一维沉降炉中进行不同工况的准东煤燃烧试验,并通过电感耦合等离子体发射光谱仪对煤灰中碱及碱土金属含量进行表征,研究了准东煤在不同反应环境中碱及碱土金属的迁移和沉积规律。结果表明:随燃烧温度的升高,煤样中钠金属逃逸量升高,当温度超过1 100℃时,钠金属逃逸量为2 760μg/g,超过85%。不同温度下煤灰中相同种类的其他氧化物含量较接近,CaO与MgO在灰中占比较大。O2体积分数对钠逃逸量的影响不明显,对相同种类氧化物占比影响较小,最大相差仅为0. 52%。在沉降炉试验中,随温度的升高,沉积灰灰样颜色由浅变深,灰沉积逐渐加重并难以清除,表明温度升高对结渣有促进作用。温度超过1 000℃时,Na挥发基本完成,含量稳定在11%左右。高温下,灰沉积管表面产生氧化皮脱落现象。在过量空气系数较大时,沉积灰灰样中的团聚烧结物较其他2种气氛少,但减弱幅度较小。炉膛中的煤粉燃烧均匀性随煤粉细度的增大而变差,导致部分煤粉剧烈燃烧使炉膛内局部温度偏高,灰沉积加重。此外,灰中的大颗粒数量也随粒径的增大而增多,黏结在结渣棒上的大颗粒增多。

Due to the wide range of Zhundong mining area,the properties of Zhundong coal are different in different areas.In order to explore the slagging mechanism of Zhundong coal,the combustion tests of Zhundong coal under different conditions were carried out in a horizontal tube furnace and one-dimensional drop furnace,and the alkali and alkali earth metals(AAEM)contents of Zhundong coal were measured by ICP-OES.The migration and deposition of AAEM in different reaction environments of Zhundong coal were investigated.The results show that with the increase of temperature,the amount of escaping sodium metal from coal samples increases and when the temperature exceeds 1 000℃,that comes to 2 760μg/g,over 85%.The contents of the other same oxides of the same kind in coal ash are close at different temperatures,the proportion of Ca O and MgO in ash account for a lot.The O2 fraction has little effect on sodium metal escape and the proportion of the same oxides,and the biggest difference is only 0.52%.The result of experiments of drop furnace shows that the color of ash deposit changing from light to deep and the deposition of gray gradually increases and ash deposit is difficult to be removed,which indicates that the increase of temperature promotes slagging.When the temperature exceeds 1 000℃,the volatilization of sodium metal finishes and the content of Na in ash remains at about 11%.What’s more,at high temperature,oxide scales on ash deposit tubes fall off.When the excess air coefficient is large,the agglomeration in ash deposition is less than that in the other two atmospheres,but the difference is not obvious.The uniformity of pulverized coal becomes worse with the increase of pulverized coal fineness during combustion,resulting in the severe combustion in some location in the furnace,and that makes the local temperature higher than other conditions and aggravates the ash deposition.In addition,the number of large particles in ash increases with the increase of particle size,and the number of large particles adhering to slagging rods increases.