Numerical simulation of influence of multi-baffles on particle residence time distribution in cross-flow bubbling beds
The particle residence time distribution(RTD)in a cross-flow bubbling fluidized bed needs to be strictly controlled due to its significant influence on the gas-solid mixing behavior and the reaction process.Based on the Eulerian-Eulerian two fluid model combined with species transport equation,the influence of different internal baffle designs and its numbers on the gas-solid flow behavior and particle RTD characteristics in a cross-flow bubbling bed was investigated.The three vertical baffle designs such as overflow baffles,underflow baffles,and side flow baffles were adopted,and the number of baffles 1～13 was selected.Besides,particle transport behavior between chambers in the fluidized bed was analyzed using the particle recirculation coefficient.The simulation results showed that all the three baffle designs can obtain narrow RTD and limit the back-mixing of particles.For the three baffle designs,the side flow baffles led to the lateral solids concentration gradient in the bed,while the underflow baffles resulted in the local lateral solids concentration gradient in each chamber,indicating the designs of baffles had obvious effect on the driving force of particle transport.It had also been observed that both the side flow baffles and the underflow baffles can reduce the transport resistance,but the overflow baffles caused the severe backflow of particles.In addition,increasing the number of baffles can make the particle flow tended to the plug flow,resulting the rise of average residence particle time.The decreasing trend of the particle recirculation coefficient can also be observed with the increase of baffles number,which meant the particle back-mixing could be suppressed.In this study,the side flow baffles were the best design for the present cross-flow bubbling bed.
cross-flow bubbling bedvertical bafflesresidence time distributionparticle transportnumerical simulation
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