基于CFD-DEM方法与多孔介质模型的管式固定床反应器柱状颗粒床层特性研究

STUDY ON THE CHARACTERISTICS OF COLUMNAR GRANULAR BED IN TUBULAR FIXED BED REACTOR BASED ON CFD-DEM METHOD AND POROUS MEDIUM MODEL

使用计算流体力学与离散元法(CFD-DEM)和多孔介质模型分别对管式固定床反应器进行数值模拟,讨论在不同装填方式与管径比条件下,柱状颗粒床层的堆积特性与单位压降变化规律,并对比两种数值模拟方法计算结果的一致性和计算效率。计算结果表明,混合装填方式比单一装填方式更容易使柱状颗粒床层达到稳定状态。在采用单一装填方式且管径比一定时,床层压降会随入口气速增大而增大,在实际应用中应选择合适的入口气速,以防止设备损坏。当采用混合装填方式时,床层截面压力波动显著减小20.63%,床层颗粒堆积更均匀。对比CFD-DEM与多孔介质模型的计算结果与效率,发现当颗粒雷诺数(Re_(p))小于229时,多孔介质模型与耦合算法得到的床层压降最大偏差为6.3%;当Re_(p)从229增大到458时,床层压降的偏差随Re_(p)增大而增大,最大偏差为13.4%,满足工程误差要求。在计算效率方面,使用多孔介质模型计算所需要的时间是CFD-DEM耦合算法的1320。因此,当管径比大于16.58、Re_(p)小于458时,多孔介质模型对于柱状颗粒床层计算的适用性和可靠性更高。

The computational fluid dynamics and discrete element method(CFD-DEM)and the porous medium model were used to numerically simulate a tubular fixed-bed reactor,and the packing characteristics and unit pressure drop of the column particle bed were compared.The consistency and efficiency of the two numerical simulation methods were compared.The calculation results showed that the column bed was more stable with mixed loading than with single loading.In the single loading and a certain tube diameter ratio,the pressure drop of bed increased with the increase of the inlet gas velocity when a single filling was used and the pipe diameter ratio was fixed.Therefore suitable inlet gas velocity should be selected in practical applications to prevent equipment damage.When the hybrid loading method was used,the bed cross-section pressure fluctuation was significantly reduced by 20.63%,and the bed particle accumulation was more uniform.Comparing the calculation results and efficiency of CFD-DEM with that of porous media model,it was found that when the particle Reyno number(Re_(p))was less than 229,the maximum deviation of bed pressure drop between the porous media model and the coupling algorithm was 6.3%;when the Re_(p) increased from 229 to 458,the deviation of bed pressure drop increased with the increase of Re_(p),and the maximum deviation was 13.4%,which met the requirement of engineering accuracy.In terms of computational efficiency,the calculation time of porous media model is 1320 of that of CFD-DEM coupling algorithm.Therefore,the porous media model has better applicability and reliability for the calculation of columnar granular beds when the pipe diameter ratio is greater than 16.58 and Re_(p) is less than 458.