The flow behavior of gas and solid was investigated in FCC simulator of φ710×4000/φ870×11000mm.The axial and radial distributions were detected with matrix fiber-opticprobes.It was found that the distribut...The flow behavior of gas and solid was investigated in FCC simulator of φ710×4000/φ870×11000mm.The axial and radial distributions were detected with matrix fiber-opticprobes.It was found that the distribution of bubble diameter in the turbulent region of the fluidizedbed of fine particles was different from the results reported for lab-scale experiments.Radially therewere three areas,i.e.,the central(r/R=0-0.4),the intermittent or stable(r/R=0.4-0.8)and thenear wall(r/R=0.8-1.0)areas respectively.It was noticed that bubbles were almost non-existing atthe near wall area.Hence,according to the coalescence and splitting theory of bubbles,a two-areamodel of bubble diameter distribution was proposed and a dimensionless parameter(γ_M)regarded asan index for’quality’of fluidization was deduced.展开更多
This paper examines the suitability of various drag models for predicting the hydrodynamics of the turbulent fluidization of FCC particles on the Fluent V6.2 platform. The drag models included those of Syamlal-O＇Brie...This paper examines the suitability of various drag models for predicting the hydrodynamics of the turbulent fluidization of FCC particles on the Fluent V6.2 platform. The drag models included those of Syamlal-O＇Brien, Gidaspow, modified Syamlal-O＇Brien, and McKeen. Comparison between experimental data and simulated results showed that the Syamlal-O＇Brien, Gidaspow, and modified Syamlal-O＇Brien drag models highly overestimated gas-solid momentum exchange and could not predict the formation of dense phase in the fiuidized bed, while the McKeen drag model could not capture the dilute charac- teristics due to underestimation of drag force. The standard Gidaspow drag model was then modified by adopting the effective particle cluster diameter to account for particle clusters, which was, however, proved inapplicable for FCC particle turbulent fluidization. A four-zone drag model （dense phase, sub- dense phase, sub-dilute phase and dilute phase） was finally proposed to calculate the gas-solid exchange coefficient in the turbulent fluidization of FCC particles, and was validated by satisfactory agreement between prediction and experiment.展开更多
The bed expansion in the dense region of FCC turbulent fluidized bed has been studied in a cold fluidized bed made of plexiglass with 710×4000/870×ll000mm and a RFCC regenerator(800,000T／a）.By using dimens...The bed expansion in the dense region of FCC turbulent fluidized bed has been studied in a cold fluidized bed made of plexiglass with 710×4000/870×ll000mm and a RFCC regenerator(800,000T／a）.By using dimensional analysis,a calculation equation of dense phase density correlated by dimensionless groups is obtained.The equation may be use ful for process engineering design of commercial units.展开更多
In our present work, a post-riser regeneration technology （PRRT） for fluid catalytic cracking （FCC） units was developed to deal with increasingly heavier feedstock and hereby the larger amount of coke deposited on...In our present work, a post-riser regeneration technology （PRRT） for fluid catalytic cracking （FCC） units was developed to deal with increasingly heavier feedstock and hereby the larger amount of coke deposited on the catalyst particles during reaction. This technology can make full use of the advantages of riser regenerator, such as high cokeburning efficiency and low residual carbon, and at the same time overcome its disadvantages, such as difficulty in starting combustion. The average particles concentration on the cross section of the system was studied on a large scale cold model experimental set-up. Also a necessary software was developed by combining the hydrodynamics research results in our work with the coke-burning kinetics model and the heat and mass transfer model developed by previous researchers. The simulation results showed that the PRRT could increase regeneration capability by 16.28%-26.24% over the conventional turbulent fluidized bed regenerator under the similar operation conditions, and that the residual carbon could be kept below 0.1 wt %.展开更多
Based on the calculation of flow parameters in a fluidized bed and modeling study, a mathematical model for the industrial turbulent fluidized bed reactor was developed, and was verified by commercial data and proved ...Based on the calculation of flow parameters in a fluidized bed and modeling study, a mathematical model for the industrial turbulent fluidized bed reactor was developed, and was verified by commercial data and proved to be suitable for describing the characteristics of industrial turbulent fluidized bed reactor in different展开更多
文摘The flow behavior of gas and solid was investigated in FCC simulator of φ710×4000/φ870×11000mm.The axial and radial distributions were detected with matrix fiber-opticprobes.It was found that the distribution of bubble diameter in the turbulent region of the fluidizedbed of fine particles was different from the results reported for lab-scale experiments.Radially therewere three areas,i.e.,the central(r/R=0-0.4),the intermittent or stable(r/R=0.4-0.8)and thenear wall(r/R=0.8-1.0)areas respectively.It was noticed that bubbles were almost non-existing atthe near wall area.Hence,according to the coalescence and splitting theory of bubbles,a two-areamodel of bubble diameter distribution was proposed and a dimensionless parameter(γ_M)regarded asan index for’quality’of fluidization was deduced.
基金supports by the National Natural Science Foundation of China through the programs for Distinguished Young Scholars of China(Grant No.20725620 and Grant No.20525621)the programs"Multiple Scale Analysis and Scalingup of Direct Coupled Dual Gas-Solid Fluidized Reaction Systems"(Grant No.20490202)
文摘This paper examines the suitability of various drag models for predicting the hydrodynamics of the turbulent fluidization of FCC particles on the Fluent V6.2 platform. The drag models included those of Syamlal-O＇Brien, Gidaspow, modified Syamlal-O＇Brien, and McKeen. Comparison between experimental data and simulated results showed that the Syamlal-O＇Brien, Gidaspow, and modified Syamlal-O＇Brien drag models highly overestimated gas-solid momentum exchange and could not predict the formation of dense phase in the fiuidized bed, while the McKeen drag model could not capture the dilute charac- teristics due to underestimation of drag force. The standard Gidaspow drag model was then modified by adopting the effective particle cluster diameter to account for particle clusters, which was, however, proved inapplicable for FCC particle turbulent fluidization. A four-zone drag model （dense phase, sub- dense phase, sub-dilute phase and dilute phase） was finally proposed to calculate the gas-solid exchange coefficient in the turbulent fluidization of FCC particles, and was validated by satisfactory agreement between prediction and experiment.
文摘The bed expansion in the dense region of FCC turbulent fluidized bed has been studied in a cold fluidized bed made of plexiglass with 710×4000/870×ll000mm and a RFCC regenerator(800,000T／a）.By using dimensional analysis,a calculation equation of dense phase density correlated by dimensionless groups is obtained.The equation may be use ful for process engineering design of commercial units.
文摘In our present work, a post-riser regeneration technology （PRRT） for fluid catalytic cracking （FCC） units was developed to deal with increasingly heavier feedstock and hereby the larger amount of coke deposited on the catalyst particles during reaction. This technology can make full use of the advantages of riser regenerator, such as high cokeburning efficiency and low residual carbon, and at the same time overcome its disadvantages, such as difficulty in starting combustion. The average particles concentration on the cross section of the system was studied on a large scale cold model experimental set-up. Also a necessary software was developed by combining the hydrodynamics research results in our work with the coke-burning kinetics model and the heat and mass transfer model developed by previous researchers. The simulation results showed that the PRRT could increase regeneration capability by 16.28%-26.24% over the conventional turbulent fluidized bed regenerator under the similar operation conditions, and that the residual carbon could be kept below 0.1 wt %.
文摘Based on the calculation of flow parameters in a fluidized bed and modeling study, a mathematical model for the industrial turbulent fluidized bed reactor was developed, and was verified by commercial data and proved to be suitable for describing the characteristics of industrial turbulent fluidized bed reactor in different
