Study And Numerical Simulation Of Catalyst Attrition In The Riser Reactor

The Fluid Catalytic Cracking(FCC)technology is the important secondary process for oil refining.As a typical process of gas solid fluidization,the problem of the catalysts attrition in the Fluid Catalytic Cracking unit,has a significant impact on the nature of the unithas attracted people's attention and concern for a long time..But because the particle attrition is a long-term gradual process,it is difficult to implement high precision precision measuring method in the field.So researches and study on the attrition of internal of riser are insufficient.In this investigation,we combined experiment with Computational Fluid Dynamics(CFD)method in conducting the research,firstly,we use model device,determine the particle attrition model on the basis of experiment,and aimed at specific catalyst the regression parameters of attrition model,using the software of Computational Fluid Dynamics establish the Euler-Euler Two Fluid Method(TFM),and then,the particle attrition model coupling in the simulation process,import the regression parameter(mainly determined by the nature of the particles)obtained by the result of the experiment,numerical simulation method can be used to analyze the process of particle attrition in fluidized bed.Finally,a numerical simulation of the riser with four nozzles and analysis of the attrition condition of riser reactor was carried out.Using the gooseneck attrition tester to determine the change regularities of the particle attrition with the variation of attrition time,the gas velocity and the particle size.According to the result,we found that the attrition mechanism of catalyst particle attrition is erosion mechanism,and the degree of the particle attrition in the initial stage is greater than the follow stages,the degree of particle attrition increase with the increase of gas velocity,the larger the initial particle size the more serious the attrition.Using the computational fluid dynamics method for numerical simulation of a simple riser reactor,and to validate the accuracy of the hydrodynamics and attrition coupling model.Through simulation calculation,in the simple riser reactor,the catalyst particle badly attrition area concentrated near the pipe wall.The particle's erosion near the center area is relatively minor.After comparing the experimental results to determine the value of the key parameter,it examines the effect of inlet gas velocity,solid fraction,particle diameter,operating pressure on catalyst particles attrition of the inner riser in detail.The results show that the increase of inlet velocity of the particles increases the degree of attrition,but the growth rate decrease.The solid phase fraction proportionate to the degree of attrition.The effect of particle diameter on particle attrition is the maximum.With the increase of the particle diameter,attrition of the catalyst particles is gradually increased,and the rate of increase enhance.Last the riser with four nozzles is simulated.By analyzing the conditions of gas phase flow and solid phase flow and the solid fraction in the riser reactor,we discovering that flow field near the nozzle outlet changes complexly.In the cross-section near the nozzle of riser,the gradient of velocity and the gradient of solid phase fraction are great.Then analysis the condition of the particle attrition of each area,and influence of solid phase fraction is greater than the impact of attrition rate.