Abstract: Based on the Eulerian?Lagrangian method, a 3D computational fluid dynamics (CFD) model of a two-stage dry coal powder entrained flow gasifier was established and the coal gasification process in the entrained flow bed was simulated and analyzed using the homogeneous and heterogeneous multistep chemical reaction kinetics to define the coal gasification reaction, the k?? model was used to describe the gas phase turbulent flow, and stochastic tracking method (STM) was used to indicate motion track of char particles. At the oxygen/coal mass ratio of 0.9, 1.0 and 1.1, respectively, different reaction mechanisms were simulated to determine the optimal reaction mechanism according to the published experimental conditions. Further, the effect of coal/oxygen ratios in the upper and lower stages on the coal gasification characteristics were studied at the oxygen/coal ratio of 1.0. The results showed that the reaction mechanism adopted a complete combustion reaction of coke and volatiles and neglected the participation of CO in the gas phase combustion reaction (Case E), the simulation results was in good agreement with the experimental data with an error of less than 2%. In the case of total oxygen/coal ratio of 1.0, the reaction mechanism of Case E was selected to examine the effect of coal/oxidant between the various stages on the overall performance of the gasifier. When the primary feed (A?A) coal and oxidant reached and exceed 50wt% of the total feed, the overall performances of the gasifier such as syngas composition, carbon conversion and active ingredients were optimized. The carbon conversion rate reached 99.6% when 70wt% coal and 60wt% oxygen were injected at the first nozzle (A?A level), and the maximum synthesis gas yield was 78.24mol% when the first nozzle injected 50wt% coal and 50wt% oxygen.

Key words: two-stage entrained flow gasifier, coal gasification, numerical simulation, oxygen/coal ratio distribution

摘要： 基于Eulerian?Lagrangian方法建立了两段式干煤粉气流床的三维CFD计算流体动力学模型，利用均相与非均相多步化学反应动力学确定煤气化反应，用k??模型描述气相湍流流动，用随机轨道模型追踪煤粉颗粒的运动轨迹，模拟了气流床内的煤气化过程。在氧/煤质量比为0.9, 1.0和1.1时，基于文献实验条件对不同反应机理进行数值模拟，通过结果对比获得最佳反应机理。考察了氧煤比为1.0时上下两阶段煤/氧比对煤气化特性的影响。结果表明，选用焦炭和挥发物完全燃烧反应、忽略CO参与气相燃烧反应的反应机理(Case E)的模拟结果与实验数据非常吻合，误差小于2%。当一级喷嘴(A?A水平)煤和氧化剂喷入量达到并超过给煤量和进气量的50wt%时，合成气组分、碳转化率和有效成分等气化炉总体性能指标较好。在一级喷嘴喷入70wt%煤和60wt%氧气时碳转化率最大，为99.6%，一级喷嘴喷入50wt%煤和50wt%氧气时合成气组分最佳，最大合成气产率为78.24mol%。

关键词: 两段式气流床, 煤气化, 数值模拟, 氧煤比分配