准东煤水分测量及其干燥过程释放特性

Measurement of moisture content in Zhundong coal and its release characteristics during drying process

高水分含量的准东煤不利于后续燃烧、热解和气化等热化学利用过程,干燥脱水是实现其高效利用的前提,因此对准东煤中水分进行研究。采用同步热分析法,考察准东煤中水分赋存形态及水分含量,通过DDTG(TG对时间的二阶导数)和DDSC(DSC对时间的一阶导数)特征识别出不同种类水分,获得了自由水和结合水含量分别为1.32%和3.78%。探索了初始质量、颗粒直径、升温速率和温度对准东煤水分释放过程的影响,结果表明随着初始质量增加,准东煤水分脱除量由5.63%提高至5.99%;0~2 mm失重速率随粒径增加而增大;2~4 mm失重速率随粒径增加而减小,粒径增加导致水分释放路径延长,减少水分扩散系数;由于升温速率增加从而强化了煤样内部传热过程,失重速率随升温速率(0.5~3 K/min)增加由0.0822%/min逐渐增至0.347%/min,同时伴随着准东煤中水分释放速率峰滞后现象。由于加热终温增大水分子释放能量,随着温度由50℃提高至105℃,水分脱除总量增加了25.6%。

High moisture content of Zhundong coal is not conducive to subsequent thermal and chemical utilization processes such as combustion,pyrolysis,and gasification.Drying and dehydration are the prerequisites for achieving its efficient utilization.Therefore,the moisture content of Zhundong coal was investigated.The synchronous thermal analysis method was used to investigate the forms and contents of water in Zhundong coal.Different types of water were identified through the characteristics of DDTG(second derivative of TG over time)and DDSC(first derivative of DSC over time).The free and bound water contents were found to be 1.32%and 3.78%,respectively.The effects of initial mass,particle diameter,heating rate and temperature on the moisture release process of Zhundong coal were investigated.The results show that with the increase of the initial mass,the moisture removal rate of Zhundong coal increases from 5.63%to 5.99%.The weight loss rate in the range of 0-2 mm increases with the increase of the particle size.The weight loss rate in the range of 2-4 mm decreases with the increase of the particle size,which leads to the extension of the water release path and the decrease of the water diffusion coefficient.Due to the increase of the heating rate,the internal heat transfer process of the coal sample is strengthened.The weight loss rate gradually increases from 0.0822%/min to 0.347%/min with the increase in heating rate(0.5-3.0 K/min),accompanied by a lag phenomenon in the peak of water release rate in Zhundong coal.Due to the increase in the final heating temperature,water molecules release energy.As the temperature increases from 50℃to 105℃,the total amount of water release increases by 25.6%.