Abstract:
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.