大型反应器内管式气体分布器的研究进展

Research progress on pipe-type gas distributors in large-scale reactors

管式气体分布器广泛应用于煤化工、生物制药、废水处理及石油化工等领域。目前分布器的研究报道较为分散,新工艺的开发和反应器的放大研究对分布器提出了新的要求和挑战。因此,从分布器对反应器性能的影响、分布器内变质量流流动行为、分布器的研究方法、设计需求和未来研发建议5个方面对管式气体分布器研究进展进行了系统性分析和综述。均匀的分布器布气行为有利于增加反应器的气含率,减小压降和死区,提升相间传递及反应过程,尤其是对于具有较低高径比的示范及工业规模反应器。管式气体分布器的布气行为是摩擦压降和压力回升协调竞争的综合结果。一维理论模型是预测管式分布器内气体分布行为的方法之一,模型预测结果与选用的管道摩擦系数、压力回升系数和孔板阻力系数的表达式有关。压力回升系数本质上与分布孔前后的速度或动能变化率相关,孔板阻力系数与单位动量穿孔流体的压降相关。通过改变分布器的几何结构来调节3个特征参量是提升分布器的布气均匀性的有效途径。研究多环和多级大型复杂分布器的布气规律和考虑分布器布气规律与反应器模拟中进口条件的耦合是反应器放大过程中亟需解决的问题。CFD模拟可以揭示分布器内的局部流动细节,但目前仍难以支撑模拟具有复杂几何结构的大型分布器,未来需要与超级并行计算技术相结合。综合使用理论模型、实验测量和CFD模拟3种方法可以为工业上大型复杂多级分布器的设计优化和保障反应器的高效运行提供科学指导。

Pipe-type gas distributors are widely used in coal chemical,bio-pharmaceutical,wastewater treatment and petroleum chemical industries.However,reported researches about distributors are scarce and scattered,and developments of new process and scale-up,process investigations have led to new requirements and challenges on distributors A state-of-the-art review on the research progress of distributors is given in this paper,including the distributor effects on reactor performance,non-uniform fluid distribution,models and experiments,design requirements and suggestions for future research and development.Uniform gas distribution can increase gas holdup and mass transfer rate,decrease pressure drop and back-mixing,and avoid dead-zones,especially in the pilot-or industrial-scale reactors of low height-to-diameter ratio.Pressure distribution in distributors is jointly dominated by friction dissipation and pressure recovery.The fluid distribution behavior is determined by friction coefficient,pressure recovery coefficient and resistance coefficients.The pressure rise is positively correlated to pressure recovery coefficient and resistance efficient,and the pressure drop is positively correlated to friction coefficient.Pressure recovery coefficient is essentially relevant to the rate of velocity change or kinetic energy change,and the resistance coefficient is releted to the pressure drop of per-unit momentum fluid.The three coefficients are the key to the optimal design of a distributor.Flow distribution in complex multi-ring or multi-stage distributors and coupling of the flow distribution and the inlet boundary condition in CFD simulations are the crucial questions to be addressed in scale-up process of reactors.Direct CFD simulation of distributors of complex geometry still faces several challenges in geometry meshing and computational cost.One-dimensional modeling can reasonably predict the fluid distribution with suitable parameters correlated from experiments,and CFD could be used to reveal the local flow details at each hole.Combination of the three methods may be an effective way for the study and optimization of large-scale complex multi-ring pipe-type gas distributors.