Simulation Study On The Force Characteristics Of The Baffles Immersed In Gas-Solid Fluidized Beds

Fluidized bed reactors are widely used in various fields of modern industries.Reasonable arrangement of internal components can effectively improve reaction efficiency and reactor performance.Due to the irregular flow of the gas-solid two-phase in the fluidized bed,the internal components that play the role of improving the flow structure inside the bed are subjected to non-uniform loads,and the instantaneous or continuous effect of this load may cause direct fracture of the internal components or Fatigue damage seriously affects the safety and long-term reliability of the reactor.Therefore,mastering the force characteristics and mechanism of internal components in the fluidized bed is helpful for rationally setting internal components and ensuring long-term safe operation of the fluidized bed reactor.Previous experiments have been carried out to study the effects of various factors on the mechanical properties of the baffles immersed in the dense bed under the conditions of free accumulation,start-up and stable fluidization.Then,based on the CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)simulation,a statistical and calculation method of the load intensity on the surface of the horizontal baffle was constructed,and the flow process of the fluidized bed of B-type quartz sand was simulated.The force characteristics of a single horizontal baffle and the effect of the horizontal baffle on the gas-solid flow are studied.On the basis of the previous experimental and simulation research work,this study further explored the influence of factors such as bed operating parameters,particle size,number,spacing and distribution of baffles on the mechanical characteristics of baffle internals through numerical simulation.At the same time,by intercepting the typical solid fraction distribution in the fluidized bed,the inherent relationship between the gas-solid flow in the fluidized bed and the force characteristics of the baffle plate is analyzed.The research results show that for a fluidized bed with a single baffle installed,the influence of the horizontal baffle and the vertical baffle on the flow state is very different in the start-up stage,and the horizontal baffle will be subjected to a larger peak load;In the fluidization stage,the load on the horizontal baffle is significantly larger than that on the vertical baffle,which is related to the force mechanism of the baffle,especially the effect of air bubbles.The superficial gas velocity has an important influence on the flow state of the bed and the force characteristics of the baffles.With the increase of the superficial gas velocity,the loads on the horizontal and vertical baffles increase greatly.As the static bed height increases,the flow of the bed becomes more intense,and the load on the baffle plate during the stable fluidization stage also increases gradually.The installation height of the baffle has a great influence on the load of the baffle,especially in the stable fluidization stage,as the installation height of the baffle increases,the load on the baffle also increases significantly.For B-type quartz sand particles,as the particle size increases,the size of the bubbles in the bed decreases,the gas-solid fluidization is more stable,and the load on the baffle decreases.For the fluidized bed with multiple baffles installed,the test baffles of the fluidized bed with horizontal multi-baffles are subjected to higher loads than the fluidized bed with vertical multi-baffles.At the same time,compared with the single-baffle bed,the multi-baffle bed has better bed fluidization quality,and the gas-solid contact is better.The installation spacing of baffles has a great influence on the vertical multi-baffle bed.With the increase of baffle spacing,the load on the test baffle will increase.The distribution of the baffles in the multi-baffle bed has an important influence on the force characteristics of the test baffle and the flow characteristics of the bed.When more vertical baffles are installed at the same height,the crushing effect on bubbles is strengthened,the gas-solid contact is strengthened,and the load on the test baffle is significantly reduced.When the number of vertical baffles increases,the load amplitude is relatively stable.There will be no large fluctuations,which is beneficial to improve the stability of the fluidized bed.