摘要
煤炭地下气化是一种将地下难以开采的煤炭资源在原位进行气化的新型煤炭利用技术,煤层空腔演化过程中产生大颗粒煤的热解和气化是煤炭地下气化重要组成部分。为探究煤炭地下气化过程中大颗粒煤的热解动力学特性,采用Netzsch STA 449 F3同步热分析仪研究了不同升温速率和煤粒径对内蒙古烟煤热解特性的影响。在试验气氛N_(2)、流量100 mL/min条件下采用非等温热重分析法,热解终温为1200℃,通过分析TG/DTG曲线,确定在不同升温速率和煤粒径下煤热解的反应特征温度和特征指数,并利用n级反应机理函数和Coats-Redfern积分法进行动力学分析,获得反应级数、活化能和指前因子。结果表明:大颗粒煤热解起始温度T_(i)和最大失重速率温度T_(max)随升温速率的增加而增大,其中T_(i)由升温速率5℃/min时的401℃增加至10℃/min时的425℃,T_(max)由升温速率5℃/min时的442℃增加至10℃/min的469℃,且最大失重速率和热解特征指数随升温速率的增大而增加,促进挥发分释放。煤粒径的增加使T_(i)升高,但对T_(max)没有明显影响,最大失重速率和热解特征指数均随煤粒径的增加而增大,其中最大失重速率由粒径小于0.1 mm时的1.58%/min缓慢升高至粒径为0.7~0.8 mm时的1.85%/min,热解特征指数则由粒径小于0.1 mm时的0.54×10^(-6)%^(3)/(min^(2)·℃^(3))增加至粒径0.7~0.8 mm时的0.84×10^(-6)%^(3)/(min^(2)·℃^(3))。动力学分析结果表明,不同条件下大颗粒煤热解的表观活化能的计算可以划分为2个温度区间,且高温区段的活化能明显低于低温区段的活化能,反应级数均为1.5。升温速率的增加使煤热解平均活化能由5℃/min时的59.46 kJ/mol降低至20℃/min时的47.71 kJ/mol,而粒径的增加则使平均活化能升高。
Underground Coal Gasification(UCG)is a new mining technology about in-situ gasification of deep coal seams.The pyrolysis and gasification of coal particles with large sizes during the evolution of coal seam cavities is an important part of underground coal gasification.In order to explore the pyrolysis kinetics characteristics of large coal particles,the thermal analyzer(Netzsch STA 449 F3)was used to investigate the effect of heating rates and particle sizes on the pyrolysis characteristics of Inner Mongolia bituminous coal.Under the conditions of test atmosphere N_(2),flow rate 100 mL/min and the final temperature is 1200℃,the non-isothermal thermogravimetric analysis was adopted.The characteristic temperatures and the devolatilization index were obtained from the TG/DTG curves at different heating rates and coal particle size.The n-order reaction mechanism function and the Coats-Redfern integration method were adopted for the kinetic analysis to obtain the reaction order,activation energy,and pre-exponential factor.The results show that the initial devolatilization temperature T_(i) and the maximum mass loss temperature T_(max) of coal particles with large sizes both increase with the increase of the heating rate.T_(i) increases from 401℃at 5℃/min to 425℃at 20℃/min,while T_(max) increases from 442℃at 5℃/min to 469℃at 20℃/min.Besides,the maximum mass loss rate and the devolatilization index increase with the increasing heating rate,enhancing the release of volatiles.The increase of particle size shifts T_(i) towards higher temperatures,but it has no significant effect on T_(max).The maximum weight loss rate and pyrolysis characteristic index both increase with the increase of coal particle size.The maximum mass loss rate increases slowly from 1.58%/min for the pyrolysis of coal with particle size less than 0.1 mm to 1.85%/min for that with particle size of 0.7-0.8 mm.The devolatilization index increases from 0.54×10^(-6)%^(3)/(min^(2)·℃^(3))for the pyrolysis of coal with particle size less than 0.1 mm to 0.84×10^(-6)%^(3)/(min^(2)·℃^(3))for that with particle size of 0.7-0.8 mm.The results of kinetic analysis show that the apparent activation energy for the pyrolysis of coal with large sizes under different cases can be divided into two stages.The apparent activation energy at high temperature zone is much lower than that at low temperature zone,and the reaction orders are both 1.5.The average activation energy decreases from 59.46 kJ/mol at 5℃/min to 47.71 kJ/mol at 20℃/min,while it increases with the increase of particle size.
作者
彭扬凡
陈姗姗
孙粉锦
胡中发
周月桂
PENG Yangfan;CHEN Shanshan;SUN Fenjin;HU Zhongfa;ZHOU Yuegui(China-UK Low Carbon College,Shanghai Jiao Tong University,Shanghai 201306,China;Institute of Thermal Energy Engineering,School of Mechanical and Power Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Research Institute of Petroleum Exploration and Development,Beijing 100083,China)
出处
《洁净煤技术》
CAS
北大核心
2021年第6期128-133,共6页
Clean Coal Technology
基金
中国石油天然气股份有限公司重大科技攻关资助项目(2019E-25)。
关键词
大颗粒煤
升温速率
热重分析法
反应动力学
热解
large coal particles
heating rate
thermogravimetric analysis
reaction kinetics
pyrolysis
