Study On Hydrodynamics And Structure Optimization Of Slurry Bubble Column Reactor For Fischer-tropsch Synthesis

The different properties of particles in a slurry bed can affect the hydrodynamic performance during operation,so it is necessary to study the influence of particles on the gas-liquid solid three-phase flow characteristics;The addition of vertical tubular internals also affects the hydrodynamic performance of the slurry bed,and it is necessary to study the impact of the internals on the gas-liquid solid three-phase flow in the reactor.Based on this,a visual quasi two-dimensional slurry bubbling bed experimental platform has been established in this paper,which can achieve the study of bubble dynamics and flow field changes in the bed;Under the condition of considering bubble breakage and coalescence,the phase holdup distribution in a slurry bed was obtained using a computational fluid dynamics(CFD-PBM)simulation method coupled with a group equilibrium model.According to the characteristics of the Fischer Tropsch synthesis reaction,three glass microspheres with different particle sizes were selected within the particle size range of the Fischer Tropsch synthesis catalyst.The effects of particle size and content on bubble dynamics and particle fluidization characteristics were studied through a combination of experimental and numerical simulation methods.The results show that the decrease in particle size and the increase in particle content exacerbate the bubble coalescence phenomenon in the column,resulting in an increase in the average Sauter diameter of the bubbles,and a decrease in the overall gas holdup.With the increase of solid content in the slurry bed,large-scale vortices basically disappear,and the flow field distribution becomes more disordered.Increasing the particle size at a specific solid content is conducive to generating regular vortices in the flow field.The distribution laws of gas and solid holdup in the radial and axial directions of a slurry bubble column were analyzed using numerical simulation.The simulation results showed that the gas holdup showed a trend of high center and low side in the radial direction,while the solid holdup showed a trend of high near wall area and low center area,with smaller fluctuations compared to the gas holdup.The fluid mechanics performance of slurry bubble column with different number of vertical tubes was studied by numerical simulation.The research results indicate that the addition of vertical tubes stabilizes the flow field in the slurry bubble column.The larger the cross-sectional area of vertical tubes,the stronger the large-scale liquid circulation in the central and near wall regions,and the more significant the decrease in gas holdup inside the column.However,increasing the number of vertical tubes can improve the axial distribution of solid particles in the reactor and suppress the lateral coalescence between bubbles.A vertical tube internal component structure with flaky fins is proposed to address the "chimney effect" caused by vertical tube internal components.The fluid mechanics performance of a new type of vertical tube column slurry bubble column was studied by combining experiment and numerical simulation.The installation of single layer fins and double layer fins reduced the average bubble diameter in the column by 9.2% and 11.7%,respectively.By destroying the central plume,the vertical tubes with flaky fins can improve the radial distribution function of solid phase and the mixing performance of slurry bed.The mass transfer experiment of chemical absorption of carbon dioxide by sodium hydroxide solution shows that installing flaky fins in vertical tubes can significantly reduce gas-liquid reaction time and improve mass transfer efficiency.Compared with not installing single layer fins and double layer fins,the reaction time was reduced by 12.5% and 33.3%,respectively.In this paper,the effects of particles and vertical tube internals on the hydrodynamic performance of slurry beds were studied,and structural optimization was carried out for the "chimney effect" brought about by vertical tube arrays,providing some guidance for the operation,design and development of reaction equipment.