Numerical Simulation Of Internal Component Enhanced Stripping Process

The stripper is the main part of the catalytic cracking-regeneration system because it can increase the yield of light oil and reduce the burner load of the regenerator by connecting the riser and the regenerator.In recent years,due to the raw materials became heavier,it is necessary to strengthen the stripping process,and adding internal components in the stripper is the most efficient way.In this paper,numerical simulations are used to study the gas-solid flow,bubble distribution,and gas-solid back-mixing in non-hole disc-donut,perforated disc-donut,and crosser strippers.And essentially analyze the strengthening mechanism of different types of internal components to the stripping process.Based on the research on the stripper in this laboratory,the stripping performance of different types of internal components on the catalyst particle gaps and the oil and gas carried in the inner holes was investigated to provide theoretical guidance for the application of internal components of strippers in industry.In this paper,the Euler-Euler two fluid method combined with kinetics theory of granular flow(KTGF)is used to simulate the gas-solid two-phase flow in non-hole disc-donut,perforated disc-donut,and crosser strippers.And the perforated disc-donut baffle is optimized.The effects of different operating conditions on gas-solid flow in different types of strippers were investigated,and the characteristics of bubbles and back-mixing in different types of strippers were quantitatively compared and analyzed to provide theoretical guidance for industrial production.The research results show that there is a clear gas-dominant "cavity" zone under the disc-donut baffle,and there is a more serious phenomenon of particle fluidization above the disc-donut baffle.With the operation of opening hole on the disc-donut baffle,the gas-phase “cavity” region under the baffle is largely eliminated,and the particles accumulating on the baffle are well fluidized.In the process of optimizing the perforated disc-donut baffle,it was found that the 6 mm perforated disc-donut baffle did not effectively eliminate the "cavity" region of the gas phase.It turns out that,for the 18 mm and 24 mm perforated disc-donut strippers,the phenomenon of particle back-mixing is severe.Moreover,the number of bubbles is not as large as in the 9 mm and 12 mm perforated disc-donut strippers,and the bubble size becomes larger than in the 9 mm and 12 mm perforated disc-donut strippers,so 9 ? 12 mm is a suitable size range of the hole.In the crosser stripper,the gas phase exists as small bubbles in the baffle area,and the gas-solid two-phase distribution is relatively uniform.It shows that the crosser baffle has a good function of inhibiting the generation and coalescence of air bubbles,and strengthening the breaking of bubbles.And it can correct the flow direction of the gas layer by layer,which shows that the grid baffle has good gas and particle redistribution ability.Based on the research on the flow characteristics in different types of strippers,the mass transfer and stripping characteristics in different types of strippers were compared and studied.The research results show that the non-hole disc-donut stripper has a certain stripping capacity,but the stripping efficiency is low.The gas-solid contact area is increased because the small hole can break bubbles,which makes the stripping efficiency significantly improved in the perforated disc-donut stripper.The volume of oil and gas in the crosser stripper is larger than that of the perforated disc-donut stripper,which shows that the crosser baffle is better in respect of improving gas-solid flow,and increasing the catalyst particle gap and the oil and gas yield entrained in the inner hole.