Study On Heat Transfer Performance And Design Method Of A New External Catalyst Cooler Based On Heat Pipe

Regenerator external catalyst cooler is an important equipment for the catalytic cracking unit of the refinery.At present,the external catalyst cooler with multiple vertical heat tube bundles and heat transfer in dense bed widely used in refining industry.But there are some issues such as abnormal fluidization,uneven temperature,erosion wear and explosion tube,etc.With the improvement of reliability of refinery equipment and safety in production,developing a new external catalyst cooler with higher heat transfer efficiency and higher reliability has a significant industrial value.In the early stage,our group proposed a new type of external catalyst cooler based on heat pipe.It replaces traditional water supply pipe bundles with heat pipe tubes and has higher heat transfer efficiency and higher reliability.Based on the previous research,this paper studies the heat transfer performance and design method of the new external catalyst cooler by experiments.Based on the operating conditions of the industrial external catalyst cooler,this paper studies mainly the heat transfer characteristics of dense bed and freeboard of the bubble fluidized bed,the heat transfer and thermal characteristics of heat pipe under different operating conditions,such as,gas velocity,bed temperature,static bed height and cooling methods in a set of fluidized bed experimental device design for heat transfer.The design method of the new type of catalyst cooler is given,and the design results of the two types are compared.The results show that the operating conditions will affect the dense wall heat transfer.The increase of gas velocity will significantly enhance the heat transfer performance;the effect that bed temperature can strengthen enhance the heat transfer performance is obvious under higher gas velocity;Under low gas velocity,the deeper bed layer has higher heat transfer coefficient,and the shallower bed heat transfer performance is better under high gas velocity.Heat transfer occurring in dense bed is more important than freeboard space in the heat transfer of gas-solid fluidized bed.The heat transfer performance of the heat pipe performs better under high heat flux.Boiling heat transfer cooling methods can improve the heat transfer performance of the catalyst cooler and make the isothermal performance better.The experimental results of thermal characteristics show that at the initial stage of the start-up process,the wall temperature of evaporation section often occurs oscillation,then disappearing as increasing heat flux.When the heat transfer limits occur,the wall temperature in dense bed is abnormally increased,then approaching the particle temperature.It will be better under boiling heat exchange condition.The design of the new type of external catalyst cooler is based on heat transfer limits and total heat transfer coefficient.The design results of the two types show that the new external catalyst cooler allows smaller diameter tube,so the diameter of device is chunkier.The overall heat transfer performance of the new catalyst cooler is superior to that of a commercial external catalyst cooler.Combined with the advantages of new structure,it can be used as an alternative option to the commercial external catalyst cooler.