摘要
针对多段气化炉(上部快速床、下部鼓泡床),采用MP-PIC(Multi-Phase Particle In Cell)方法模拟了多粒径煤粉颗粒的三维全循环流化过程,考察了鼓泡床与快速床床径比及鼓泡床和快速床之间的过渡段高度对气化炉内流动特性的影响。结果表明,基本工况下,大颗粒主要存在于下部鼓泡床中,细颗粒主要存在于上部快速床内,但细颗粒会通过旋风分离器和回料管再次进入鼓泡床参与循环。进入旋风分离器的大部分为半径622mm以下的小颗粒,无1216 mm以上的大颗粒。旋风分离器对小颗粒的分离效率为99.75%,分离效率良好。增大床径比(即减小快速床直径),快速床中气速增大,整个气化床更快达到稳定状态,被夹带到快速床中的颗粒增多,所夹带的颗粒粒径增大。过渡段高度存在一个适当值(炉高0.6～1.0 m),升高或降低过渡段高度,快速床中颗粒浓度均增大,颗粒通量均升高,旋风分离效率降低。
The 3 D full-loop multi-stage gasifier(upper fast fluidized bed with lower bubbling fluidized bed)was simulated with MP-PIC(Multi-Phase Particle In Cell)method successfully.To study the effect of reactor structure on the gas-solid flow in the multi-stage gasifier,the effects of diameter ratio of bubbling fluidized bed to fast fluidized bed and transition section heights on the flow characteristics of gasifier were systematically studied by simulations with MP-PIC method.The results showed that the circulating fluidization process of pulverized coal was successfully simulated by the current method.For basic case,coarse particles mainly resided in the lower bubblingbed,and fine particles mainly resided in the upper fast bed.However,fine particles can return to the bubbling bed from cyclone and stand pipe.Only the small particles with diameters less than 622μm can enter the cyclone,where there were no particles with diameters larger than 1 216μm.The cyclone had a separation efficiency of 99.75%for small particles,which exhibits a good separation performance.Increasing the bed diameter ratio(ie,reducing the diameter of the fast bed)led to the increase of gas velocity in the fast fluidized bed.Under this condition the gasifier tended to reach steady state much faster.And more particles can be entrained into the fast fluidized bed.The entrained particle size range also increased.Compared to the basic condition,both increasing and decreasing the height of the transition section increased the particles concentration and solid flux in the fast fluidized bed.The efficiency of the cyclone was also higher than that of the basic condition.These implied that there existed an optimum value of the transition section height(between 0.6 and 1.0 m in this case).Increasing or decreasing this value will increase the solid flux in fast fluidized bed but will reduce the cyclone efficiency.These rules can be significant and helpful to the design and optimization of multi-stage gasifiers.
作者
冯美艳
李飞
Meiyan FENG;Fei LI(School of Mechanical&Automotive Engineering of Fujian University of Technology,Fuzhou,Fujian 350118,China;State Key Laboratory of Multiphase Complex Systems,Institute of Process Engineering,Chinese Academy of Sciences,Beijing 100190,China)
出处
《过程工程学报》
CAS
CSCD
北大核心
2019年第2期297-308,共12页
The Chinese Journal of Process Engineering
基金
国家重点研发计划资助项目(编号:2017YFB0602700)
国家自然科学基金资助项目(编号:51876212
21625605
91834302)
福建工程学院科研启动基金资助项目(编号:GY-Z18166)
关键词
多段气化炉
MP-PIC
颗粒分布
床径比
过渡段高度
multi-stage gasifier
MP-PIC
particle distribution
bed-diameter ratio
transition section height
作者简介
冯美艳(1984-),女,山西省忻州市人,博士研究生,讲师,流体力学专业,E-mail:happy_10236@126.com;通讯联系人:李飞,E-mail:lifei@ipe.ac.cn.
