Design And Fluidization Experimental Study Of Circulating Fluidized Bed Cold Model Apparatus

The circulating fluidized bed reactor has wide application in the fields of petrochemical,environmental protection and biomass processing due to its advantage of large processing capacity,convenient operation and continuous production.As the core device of catalytic cracking,the structural form of the riser and the internal gas-solid flow pattern have an important influence on the distribution and yield of the main product.In order to further study the law of gas-solid flow in the circulating fluidized bed,this project first built a large-scale multi-functional circulating fluidized bed cold model experimental platform in the special experimental building according to the experimental and teaching needs.The structure size of each part of the device is designed mainly by gas volume calculation and pressure balance calculation.Then,according to the process requirements and experimental conditions,the required rotameter,compressors,blowers and other apparatus are selected,and the corresponding pipelines are laid and connected.The experimental platform includes two independent operating systems.On the one hand,it can be used for the study of fluidization experiments of different structure risers such as equal diameter riser and diameter-enlarged riser.On the other hand,the experimental study on the turbulent circulating fluidized bed can be realized.And by changing the operating gas velocity,the gas-solids fluidization experiments of various bed-types can be realized,such as bubbling beds and turbulent beds.In this paper,the traditional equal-diameter riser is first studied on the newly built cold model experimental platform,and the axial-radial non-uniform flow behavior inside the riser is further clarified.In order to strengthen gas-solid contact and optimize flow behavior,a new type of diameter-enlarged riser reactor was proposed in this chapter.The results show that the particle concentration of the novel diameter-enlarged riser reactor still expressed as a low particles concentration in the upper region and a high particles concentration in the bottom region,and the particle concentration in the bottom region is significantly improved.At the same time,the diameter-enlarged structure can redistribute the regenerated catalyst from the inclined tube,strengthen the contact mixing of the gas-solid two phases,and make the radial distribution of the particle concentration more uniform.In addition,a large particle circulation rate and the large catalyst to oil ratio required for the reaction can be realized due to this special structure.As a new type of fluidized bed,the circulating turbulent fluidized bed is based on the circulating fluidized bed and the turbulent fluidized bed.It has a very broad application prospect.In this paper,a preliminary experimental study on the internal gas-solid flow behavior of a newly designed novel circulating turbulent fluidized bed reactor was carried out.The results show that the circulating turbulent fluidized bed can effectively increase the particle concentration of the bed,weaken the radial non-uniform "ring-nuclear" flow of the bed and reduce the gas-solid separation phenomenon while maintaining high particle flux.Through the instantaneous signal distribution of particle concentration and probability density,it can be found that the bed particle concentration fluctuation signal is always maintained at a high level,the bed gas-solids turbulence is severe,and the gas-solid contact is further strengthened due to the local internal circulation existing in the bed,which can effectively improve mass transfer and heat transfer efficiency of the bed.