气化温度对型煤加压固定床气化反应特性的影响

Effect of Temperature on the Reactivity Characteristics of Briquette During High Pressure Fixed-bed Gasification

基于小型加压固定床气化炉考察一定压力下温度对型煤气化特性的影响。研究了不同温度下气化产物演变规律并计算气化反应活化能;利用X射线荧光光谱仪、扫描电镜和X射线衍射仪对型煤以及原煤中矿物质含量、气化后灰渣形貌以及矿物质组成进行分析。结果表明:气化压力3MPa下,气化温度由1223 K提高到1473 K后,气相中CO体积浓度由14.71%增至41.36%,H2含量维持55%左右,有效气体(CO+H2)含量增加了25.88%。可见气化温度对型煤气化的产气特性有显著影响。随气化温度升高,受扩散效应与灰渣熔融双重影响,气化温度高于1323 K后碳转化率与反应速率增幅趋缓。采用未反应缩核模型(GM)与随机孔模型(RPM)计算得到的气化反应活化能分别为44.00 kJ/mol和48.56 kJ/mol,说明型煤的反应活性较高而易于气化。此外,由于生成低熔点物相钠钙长石,当气化温度高于1323 K后灰渣局部熔融,结渣性大于80%;而气化温度较低时,灰渣主要由石英和莫来石等非易熔物相构成,呈松散状,结渣性较低(20%)。

The effect of gasification temperature on briquette gasification was studied using a lab scale fixed-bed gasifier. The reactivity characteristics of briquette during gasification were investigated and the activation energy(Ea) was evaluated accordingly. The properties and morphologies of raw sample and slag after gasification were analyzed using X-ray fluorescence spectrometer(XRF), scanning electron microscope(SEM) and X-ray diffraction(XRD). Experimental results show that, the concentration of carbon monoxide and effective gas(CO+H2) in the gaseous products are increased from 14.71% to 41.36% and 69.23% to 95.11%, respectively, when the gasification temperature increases from 1323 K to 1473 K at a constant pressure of 3 MPa. It indicates that temperature has a significant effect on gaseous characteristics. Moreover, the carbon conversion and reaction rate increase slowly when the temperature at above 1323 K due to the synergistic effects of diffusion controlling and ash agglomeration. Activation energy of briquette during pressured gasification are 44.00 kJ/mol and 48.56 kJ/mol calculated by using grain model and random pore model, respectively, and they have high consistency revealing the high reactivity. The slag clinkering is above 80% due to the formation of(Na,Ca)- anorthite at above 1323 K; however, at below 1323 K the ash clinkering is less because of the high content of quartz and mullite.