Numerical Simulation Of The Impact Of Gas Jet On Gas-solid Flow And Reaction

Circulating fluidized bed boiler and coal gasifier are the important industrial equipmentsto realize clean coal utilization and conversion of our country, and to balance the problem thatthe energy structure of our country is dominated by coal. It seems particularly important tochange the past extensive energy utilization pattern, improve coal combustion efficiency ofthese devices and reduce the emission of pollutants in the present stage of development. Toachieve this goal, we must insight into the interaction of the coal particles and gas inside thereactor, make appropriate innovation and change the structure on the basis of the existingequipment to improve the gas-solid flow field inside the reactor, strengthen the interphasemixture and heat transmission, and improve the reaction efficiency. Jet actually do have awide range of engineering application. High speed gas injecting into the furnace can rapidlyenhance the turbulent kinetic energy and strengthen the local gas-solid mixture, the overallflow field will also be greatly affected. Therefore, this article simulated the overall gas-solidflow field of horizontal and vertical jet fluidized bed and analyzed the effect of the jet on thegas-solid flow field. In addition, the gas-solid flow inside a two-nozzle opposition gasifier issimulated. The difference is the velocity of the opposed jet entrance of gasifier changes withtime as sine rule. The phase difference between the two jet nozzle’s velocity is180degrees.This article calls it the opposed oscillatory jet. And the particle distribution, gas and solidvelocity and the other flow field details inside the furnace were analyzed under the twoopposed oscillatory jets. The simulation in this article used the Ansys Fluent commercialsoftware. Euler-Euler method is used to describe the gas-solid flow and the k-εturbulencemodel is adopted when the horizontal and vertical jet fluidized beds and the opposedoscillatory jet gasifier were simulated with three dimensional transient model. Than theirgas-solid flow fields were got. Furthermore, based on the results of horizontal jet fluidizedbed cold modeling, the reaction model is added to simulate the carbon particles reacting withthe air.According the simulation results, we know that, in the horizontal jet fluidized bed, thegas jet makes the solid particles flow as clockwise swirls. Besides, as the jet velocity rises, thenumber of particle flow swirls decreases and the swirls become bigger, and the particles in thefurnace become more concentrated. In the vertical fluidized bed, the vertical gas jet canenhance the particle fluidizing degree. In the middle of the fluidized bed, there forming a gasflow channel, its width increases as the jet velocity increases. In the opposed oscillatory jetgasifier, the opposed gas jets with180°phase difference makes the particle concentrate point and the gas flow impact point make concussions in certain amplitudes. The amplitude of thesolid point is larger than that of the gas impact point. The two amplitudes both decrease as thefrequency of the jet velocity increases.