煤直接液化浆态反应器内气-浆流动与反应的CFD模拟

以褐煤直接液化小试反应器为研究对象，将反应器内气-液-固三相流动简化为气-浆两相流动，使用Fluent 14.0及双流体模型，模拟预测高温、高压条件下气-浆两相流动及反应的耦合过程。对反应器内等温流场进行了三维瞬态模拟，结果表明：反应器内总体气含率较低，约为0.016 5；气-浆流速较低，且壁面附近浆液回流和返混显著；浆液在反应器内平均停留时间约为70 min，与液化反应所需时间匹配。使用Matlab最小二乘曲线拟合方法，获得褐煤在430℃、10 MPa下的液化反应速率常数，通过用户自定义函数（UDF）将动力学参数导入Fluent求解器，对反应器内流动和反应过程耦合求解。结果显示：反应器出口处煤的转化率约为89.25%，沥青质（PAA）和油气（OG）产率分别为26.33%和61.81%，与测量值吻合。此数学模型及数值方法有望应用于中试及工业装置，指导液化工艺优化和反应器的设计放大。

A CFD Simulation of Gas-Slurry Fluid Dynamics and Chemical Reactions in a Direct Coal Liquefaction Reactor

A bench-scale direct coal liquefaction (DCL) reactor was studied numerically.With the assumption of a gas-slurry Euler-Euler two-fluid model,the multiphase flow and the chemical reactions in the DCL reactor operated under the conditions of elevated pressure and high temperature were simulated by Fluent 14.0.Three-dimentional time-dependent simulation of gas-slurry flow was conducted,and the results showed that the overall gas holdup in the reactor was very low at a level of about 0.016 5.The axial velocities of the gas and slurry phases were also very low,and an obvious liquid back-flow was observed near the reactor wall.The mean residence time of the slurry phase was about 70 min,which matched the reaction time required for a complete coal conversion.A coal liquefaction model was proposed and a set of kinetic parameters were obtained using the Matlab toolbox of the least-square parameter regression method.Via user defined function (UDF),the reaction model was coupled with fluid dynamics solver of the fluent.The simulation results indicated that the coal conversion at the outlet was about 89.25%,and the predicted yields of preasphaltene and asphaltene (PAA) and oil and gas (OG) were 26.33% and 61.81%,respectively,which were in agreement with the experimental data.The mathematic models and numerical methods developed in this paper can be used to simulate DCL process in pilot and industrial reactors,and serves as an effective tool for the design and scale-up of industrial DCL reactors.