| Kerosene co-refining combines the two technologies of direct coal liquefaction and heavy oil processing,which not only reduces the operating difficulty of direct coal liquefaction,but also efficiently processes heavy oil and residual oil.The Yanchang petroleum-kerosene co-refining process adopts the technical route of suspended bed hydrocracking-fixed bed hydro-upgrading,in which the hydro-upgrading process is mainly carried out in a trickle bed reactor.The overall performance of the trickle bed reactor depends on the following factors: fluid mechanics,fluid phase mixing,heat transfer between interfaces and particles,mass transfer and reaction kinetics,etc.However,there are some specific problems,such as particle shape and size distribution,bed material characteristics,non-uniform flow,wetting the catalyst particles and its influence on the rate of heat and mass transfer is a key design industrial trickle bed reactor.The gas-liquid distributor is an important internal component of the gas-liquid-solid three-phase reactor,and its main function is to fully mix the gas-liquid two phases and spray them evenly on the solid bed.At present,the BL type gas-liquid distributor,which is widely used in the petrochemical industry,has problems such as small spray angle.For this reason,a broken flow plate structure was designed to seal the outlet of the downcomer by using an open hole plane and a cone surface.The computational fluid dynamics method was used to compare and analyze the fluid dynamics performance of the distributor before and after the improvement.The results show that in the original structure,the central flow directly passing through the broken flow plate accounts for 99.8% of the total flow,and this part of the liquid is difficult to disperse in the subsequent space.After adding a cone surface to the original structure to form a closed flow plate,the central flow rate is effectively reduced,the side flow rate is significantly increased,the liquid phase is more evenly distributed throughout the cross-section and the spray rate of the distributor is also significantly increased.Under the condition of constant opening area,the best number of openings on the bottom surface and side cone is 24,and the best side cone angle is 77 °.Among them,adjusting the structure of the side cone surface can better increase the spray amount,and the liquid phase distribution is more uniform.At the same time,according to the characteristics of the trickle bed reactor,three models are described—the porous media model,the random-packed particle model and the bed-particle multi-scale model,layer by layer,and the use conditions of the three models are carried out from shallow to deep.analysis.In the modeling process,different methods were used for different models,and the following conclusions were obtained: the void size of the porous media model is small,and the contact area between liquid and solid increases.This can increase the specific surface area and make the interface larger,which is beneficial to the reaction process.The porous media model can describe the overall bed layer and the overall law of the reaction bed layer.The random packing particle model reflects the specific information of each particle in the bed particle.Compared with the bed condition of the porous media model,the random packing particle model is more in line with the real situation.The random-packed particle model can be more sensitive to the reaction heat and temperature conditions between the beds,and can better reflect the changes between the beds than the porous media model.The bed-particle multi-scale model can effectively make up for the disadvantage that the porous media model can only describe the overall state of the bed,and it can also make up for the disadvantage that the random-packed particle model can only obtain the surface information of the catalyst particles,and has more research space and content.The bed-particle multi-scale model can describe the coking and clogging of particles. |
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