水洗对准东煤煤质特性影响的实验研究

Experimental Investigation for Effect of Water Washing on Zhundong Coal Properties

针对准东煤由于灰中Na含量过高,燃用中会出现严重的积灰问题,在对准东煤中碱金属赋存形态进行研究的基础上,着重研究了水洗温度和时间对准东煤Na脱除量及热解燃烧特性的影响。研究表明,3种典型的准东煤中Na主要以水溶形式存在,水洗可以有效脱除Na,且脱除量与水洗温度和时间密切相关。水洗后煤热解特性指数减小,20、40℃水洗使热解提前,焦炭产量增加,挥发分产量减少,而60℃水洗则相反。水洗使燃烧TG、DTG(热质量损失、热质量损失率)曲线向高温区偏移,燃尽温度和最大燃烧温度升高,最大燃烧速率减小,燃尽时间延长,燃烧特性变差。动力学分析表明,水洗使煤热解第一、三阶段表观活化能减小,第二阶段表观活化能增大,使燃烧表观活化能、指前因子和燃烧反应速率常数减小。Na对煤样热解燃烧存在催化作用,且存在最佳Na含量使催化作用最强。

The effects of water washing temperature and time on coal properties are investigated according to the occurrence mode of alkali metals in Zhundong coal. The experimental results show that Na mainly exists in water soluble form in three typical types of Zhundong coal. Harmful element Na can be effectively removed by water washing, and the removal amount is closely related to washing temperature and time, and the pyrolysis characteristic index number of washed coals reduces. When the temperature gets below 40 ℃, the pyrolysis process of washed coals can be brought forward with more volatile yielded, and coals washed in 60 ℃ water vary oppositely. The combustion TG and DTG curves of water washed coals move towards higher temperature zone, while the burnout temperature and the maximum temperature increase, the maximum combustion rate decreases, the burnout time is prolonged, and the combustion performance is deteriorated. The kinetic analysis indicates that water washing facilitates decreasing the pyrolysis apparent activation energy during the first and third stages and increasing it during the second stage. The presence of Na exerts catalytic effect on coal pyrolysis and combustion behaviors. Moreover, there exists an optimal Na content for the strongest catalytic effect.