煤粉粒径对HNCERI气化炉碳转化率与固/液渣层分布的影响

Numerical simulation on the effect of coal size on slag distribution and carbon conversion efficiency of HNCERI gasifier

以中国华能集团清洁能源技术研究院(Huaneng Clean Energy Research Institute,HNCERI)两段干粉加压气化炉为研究对象,采用考虑了焦炭颗粒表面气体组分扩散效应的随机孔模型计算焦炭气化反应速率以评估碳转化率。同时,耦合熔渣子模型计算气化炉一段壁面固液渣层分布特性和热损失,研究了煤粉粒径对HNCERI气化炉碳转化率和固液渣层分布特性的影响。结果表明所构建的模型可以准确预测气化炉出口主要气体组分组成、碳转化率和气化炉一段壁面热损失;气化炉一段碳转化率受固有气化速率和停留时间控制,二段主要受颗粒停留时间控制;因此,通过减小煤粉粒径可以减小气体在颗粒表面扩散阻力,有利于提高气化炉一段碳转化率,而适量增加煤粉粒径可以增加煤粉颗粒在气化炉二段的停留时间,有利于提高二段碳转化率。模拟结果显示煤粉颗粒粒径从20μm增加到200μm,一段碳转化率从99.68%降低到了95.06%,二段碳转化率从69.03%增加到了89%。煤粉粒径对气化炉上缩口和直段壁面液态渣层分布影响很小,但显著影响固态渣层厚度的发展。

HNCERI(Huaneng Clean Energy Research Institute)two-stage dry powder pressurized gasifier was used was the research object.A random pore model that considers the effect of gas diffusion on the surface of char particle was used to calculate the char gasification reactions rate to evaluate carbon conversion efficiency.The slag sub-model was used to calculate the slag distribution characteristics and the wall heat loss of the first stage.The effect of coal size on carbon conversion efficiency and the slag distribution characteristics in HNCERI gasifier were studied.The results showed that the model can accurately predict the main gas components at the outlet of the gasifier,the carbon conversion efficiency and the wall heat loss.The carbon conversion efficiency of the first stage was mainly controlled by the intrinsic gasification reaction rate and the particle residence time,while the second stage carbon conversion efficiency was mainly controlled by particle residence time.Therefore,the decrease of coal size which significantly reduces the gas diffusion resistance on the surface of char particles was beneficial to increase carbon conversion efficiency of the first stage,while the appropriate increase of coal size which is conducive to increase the particle residence time was beneficial to increase the carbon conversion efficiency of the second stage.The simulation results showed that when the particle size increased from 20μm to 200μm,the first-stage carbon conversion efficiency decreased from 99.68%to 95.06%,while the second-stage carbon conversion rate increases from 69.03%to 89%.The coal size had little effect on the liquid slag distribution on the neck and straight wall of the gasifier,but had significantly effect on the development of solid slag layer.