摘要
热天平标准配置的坩埚为四周及底部密封的敞口容器 ,气流不能穿过物料层从坩埚底部流出 ,从而影响煤焦气化反应的动力学行为 .研究了坩埚尺寸、物料床层厚度对杯状坩埚内煤焦 CO2 气化 (气固相反应 )影响 .采用PHOENICS软件模拟分析了杯状坩埚附近及内部流体运动、浓度分布 ,同时建立了杯状坩埚内煤焦 CO2 反应 扩散模型 ,两者能很好地吻合 .杯状坩埚中进行的煤焦 CO2 反应模型参数和Da 反映了气体质量传递对反应的影响 .
During the thermogravimetric measurement of reaction rates involving mass change in a solid, such as coal char gasification reactivity, the sample is contained in a cup-like crucible, and CO2 has to access through the top surface of the particle bed. CO2 mass transfer limitations control their reaction in such situations. Different types of crucibles and coal char initial mass loadings were employed to study the effect of gas mass transfer on coal char gasification rate. The reaction temperature was 1140°C, which was in the chemical controlled reaction regime for the coal char gasification. The conclusion indicated that the coal char gasification rate strongly dependent on the crucible type and char initial mass loading. However, the gas mass transfer around and inside a crucible could be simulated by the computational fluid dynamics PHOENICS package. By simulating the space above the bed, it was confirmed that diffusion could supply most of the CO2 to the bed surface and molecular diffusion governed the mass transfer. Also, a mono-dimensional model was developed. Two parameters were used to indicate whether mass transfer was constraining the reaction either inside or to the bed according to the model. And, the CO2 concentration calculated by PHOENICS software was in good agreement with what was predicted by the model developed in this work so that the mono-dimensional model could play an important role on studying the gas-solid reaction kinetics when a cup-like crucible was employed during the thermogravimetric measurement.
出处
《化工学报》
EI
CAS
CSCD
北大核心
2005年第1期35-40,共6页
CIESC Journal
基金
国家重点基础研究发展规划项目 (G19990 2 2 10 3 )~~
关键词
煤焦气化
扩散
模型
PHOENICS软件
Carbon dioxide
Computational fluid dynamics
Computer software
Diffusion
Mass transfer
