Numercial Investigation Of Flow Characteristics In ALR

The Airlift Loop Reactor (ALR) is developed based on the conventional bubble column.It is widely used in the gas-liquid and gas-liquid-solid reaction system of chemicalengineering, bio-engineering, metallurgical industry etc. due to its high liquid circulationvelocity, uniform distribution of gas holdup and good gas-liquid mass transfer characteristics.Especially in the Slurry bed hydrocracking process, ALR as the main equipment in the entireprocess, its internal fluid flow behavior has directly effect on the device coking, reactionproceeds etc., thereby affects the plant operation safety and production efficiency.Detailed characteristics of ALR internal fluid (water-air) flow was investigated using themethod of Computational Fluid Dynamic Simulation (CFD), various numerical models andsimulation methods were used to explore the relationship between the characteristics of ALRand its structure parameters, operation conditions etc., which laid the foundation for designand scale up the ALR.First, Φ230mm ALR gas-liquid flow was simulated using the commercial softwareFluent. The gas-liquid flow numerical model was built base on the Euler-Euler two-fluidapproach to study the overall gas holdup and liquid circulation velocity under differentsuperficial gas velocity. The simulation results were tested and verified by comparing with thedata form cold state simulation. Then the relationship between the overall gas holdup andliquid circulation velocity and draft tube diameter, installation height, segmentation and staticliquid level factors etc.Then the open-source CFD simulation software OpenFOAM was used to simulate theALR internal fluid flow behavior. Its source code was fully interpretated to deeply understandthe realization of two-fluid model in the numerical simulationFinally Fushun ALR with production of50,000tons/year was simulated using thecommercial software Fluent. The three-phase numerical model was built based on theEuler-Euler-Euler method to study the distribution of coke in the reactor and the changes ofthe overall gas holdup with different solid content for different superficial gas velocity was studied at the same time.The overall gas holdup and liquid circulation velocity simulation results which based onthe two-fluid approach were reliable, and the local region gas fraction simulation result wasacceptable too. So the numerical model can be directly used as analytical tools to study thegas-liquid flow field for design and scale up the reactor. The OpenFOAM simulation exploresthe process of the realization of the two-fluid model, which not only provides a theoreticalbasis to study gas-liquid flow field by CFD tools, but also laid a theoretical foundation todevelop a more suitable solver to simulate the ALR flow field. For the simulation of thegas-liquid-solid three-phase flow field, the three-phase numerical model with a relatively lowsolid holdup can be directly predict three-phase distribution and scale-up studies of reactor.