气化炉与辐射锅炉接口的传热流动数值模拟

Numerical Study of Flow and Heat Transfer in the Transition Section Combining the Gasifier with the Radiant Syngas Cooler

针对气化炉底部、辐射锅炉拱顶及两者接口组成的系统,应用标准k-ε湍流模型、流体体积(VOF)流模型和多种辐射模型进行了非稳态计算,辐射模型包括离散坐标法(DOM)、P-1模型和离散传播辐射模型(DTRM),运用文献数据和实验值对DOM模型计算结果进行了检验。计算结果表明:辐射传热在整体传热中占主导地位,且残渣或飞灰对热辐射的影响不可忽略;DOM法计算得到气固两相流在直段最大温降为31.5℃,因此控制合适的气化炉出口物流温度可避免熔渣凝固而引起堵渣;直段末端平均流速为13.7m·s-1,锅炉内颗粒在湍流区域富集,少部分回流至拱顶区。

The standard κ-ε turbulent model, volume of fluid （VOF） multiphase model and the radiation model were used to carry out the unsteady state simulation calculation of the system composed of the bottom of gasifier, the dome of radiant syngas cooler （RSC） and the transition section combining the gasifier with the RSC The simulating calculation results were validated by lab-scale gasifier hot-model experiments and their results agree well each other. Several radiation models, the Discrete Ordinates model （DOM）, the P-1 model and the Discrete Transfer model （DTRM）, were used respectively for the simulation of the radiation heat transfer. The results show that the radiation heat transfer is dominant in the whole heat transfer process; especially the radiation of the hot soot and incompletely burned coal particles falling in the transition section cannot be ignored. Using the DOM model, the predicted maximal temperature decrease in the transition section is about 31.5℃, it indicates that the slag plugging inside the transition section can be avoided by controlling the entering temperature of gas and slag outflow from the gasifier in a appropriate range. The calculated mean flow velocity at the bottom of the transition section is 13.7 m·s^-1, while the solid particles in the RSC are enriched in its turbulence area, and a few of them reflux to the recirculation area at the dome of RSC.