煤催化加氢气化是极具发展潜力的煤制天然气技术,包括煤催化加氢热解和煤焦催化加氢气化2个步骤,其中煤焦催化加氢气化的反应速率远小于煤催化加氢热解的反应速率,是整个气化过程的速率控制步骤,因此建立适宜的煤焦催化加氢气化反应动力学对该技术的应用具有重要的意义。在小型加压流化床中,研究了Co-Ca催化煤焦加氢气化过程中煤焦颗粒密度和孔隙结构随碳转化率的变化规律,发现随反应进行煤焦颗粒密度减小,孔隙总比表面积与反应速率线性相关,表明Co-Ca催化煤焦加氢气化反应符合随机孔模型的特征。通过调控反应温度、氢分压和Co负载量,获得了煤焦中碳转化率的变化规律。结果表明:650~850℃反应仍处于动力学控制阶段;反应温度超过750℃后,反应速率显著提升,进一步提升温度至850℃时,碳转化率由650℃时的16.32%增至95.32%。随氢分压升高,碳转化率增大,氢气分压由0.6MPa增至2.5MPa时,碳转化率由19.49%提高至94.11%。随Co催化剂负载量由1%提高至3%,碳转化率持续提升,继续增加Co负载量至5%,碳转化率变化较小。采用扩展随机孔模型,引入经验参数c和p对试验数据进行分析,得到煤焦催化加氢气化反应的活化能为122.7kJ/mol,反应级数为1.54。模型预测的反应速率值与试验值之间的平均偏差为4.81%。

The coal catalytic hydrogasification is a highly promising technology for converting coal to natural gas. It consists of coal catalytichydropyrolysis and char catalytic hydrogasification. The char catalytic hydrogasification is the rate-controlling step of the whole process because its rate is much less than that of coal catalytic hydropyrolysis. Therefore, it is critical to establish a reasonable kinetic model of Co-Ca catalyzed char hydrogasification in pressurized fluidized bed for the technology′s future development. The variations of particle densityand pore characteristics with carbon conversion were investigated during Co-Ca catalyzed char hydrogasification in a lab-scale pressurizedfluidized bed. The results show that the char particle density decrease as the carbon conversion, and there is linear correlation between thetotal pores specific surface area and reaction rate. These phenomena confirm that the conversion of char should follow the randompore model during Co-Ca catalyzed char hydrogasification. The effects of reaction temperature, hydrogen pressure, and Co loading onthe carbon conversion were researched. It is found that the reaction is controlled by dynamics in the range of 650-850 ℃ . The reaction rateis dramatically increased when the temperature is over 750 ℃ , and the carbon conversion increase from 16.32% to 95.32% when reactiontemperature is elevated from 650 ℃ to 850 ℃ . The carbon conversion is elevated to 94.11% with increasing the hydrogen partial pressurefrom 0.6 MPa to 2.5 MPa. Raising the Co loading from 1% to 3% resultes in the continous increase in carbon conversion, but it has little change when the Co loading is furtherly increased to 5%. The experiment data was analyzed adopting an extended random pore modelwith the introduction of empirical parameters c and p. The results indicate that the activation energy of coal char catalytic hydrogasificationis 122.7 kJ/ mol, and the reaction order is 1.54. The average deviation between the predicted and experimental reaction rate is 4.81%.

0 引言

1 试验

   1.1 焦样制备

   1.2 试验与装置

   1.3 产物分析

2 结果与分析

   2.1 煤焦颗粒密度和孔结构的演变

   2.2 工艺参数对煤焦加氢气化反应的影响

   2.3 反应动力学模型的建立

3 结论