CPFD simulation on effects of louver baffles in a two-dimensional fluidized bed of Geldart A particles

Effect of louver baffles installation on hydrodynamics of bubbling fluidization in biomass gasifier

Biomass gasification by a bubbling bed gasifier has been a promising process to produce fuels from biomass. However, the performance is limited by gas aggregation in the gasifier. In this study, CFD simulations were used to investigate hydrodynamics in bubbling bed gasifiers installed with multilayer louver baffles to understand the roles of baffles on different aspects including gas aggregation, biomass-bed mixing, gas-biomass contact, and pressure drop. The designed baffles could reduce the gas aggregation particularly when the biomass is fed at the middle of the baffle zone. The baffles could enhance the biomass-bed mixing and the gas-biomass contact throughout the bed except near the biomass inlet. The installation of baffles would not significantly affect the overall pressure drop but slightly affect at the mid-level of the bed. For the system in this study, the baffled gasifier with biomass feeding at the middle of the baffled zone and the gas inlet velocity of 0.7 m/s could provide the best performance in term of hydrodynamics.

State-of-the-Art Review of Fluid Catalytic Cracking (FCC) Catalyst Regeneration Intensification Technologies

Fluid catalytic cracking (FCC) is the workhorse of modern crude oil refinery. Its regenerator plays a critical role in optimizing the overall profitability by efficiently restoring the catalyst activity and enhancing the heat balance in the riser reactor. Improvement in the device metallurgy and process operations have enabled industrial regenerators to operate at high temperatures with a better coke burning rate and longer operating cycle. Today, the carbon content of regenerated catalyst has drastically reduced to less than 0.1 wt.%. However, the unit is still plagued with operational complexities and insufficient understanding of the underlying dynamic, multiscale intricacies. Recent process-intensification strategies provide insights into regenerator performance improvement potentials. In this review, the importance of the uniform distribution of spent catalysts through structural modification and operational manipulations of the catalyst distributor is discussed. The knowledge of the role of baffles in enhancing excellent gas–solid interaction has been increasing, but skepticism due to its complex hydrodynamic effects on gas–solid flows fends off operators from its application, a critical evaluation of its implication in the regenerators is covered. The understanding of the contribution of air/steam distributor design and feed gas injection techniques for even contact with spent catalyst leading to the improvement in FCC performance is also investigated. The reliability of FCC components is equally a big concern, as unplanned shutdown and enormous economic losses are being witnessed due to device failure. To this end, mitigation approaches to damaging afterburn and high-temperature erosion problems with respect to process control and geometric adjustment in the bed, freeboard, cyclone separators and collection ducts are explored. Emission limits for fluid catalytic cracking unit (FCCU) and products are consistently ratcheting downward; the commingled turnkey solutions to reducing pollutants generation are also reviewed.

Effect of a Baffle on Bubble Distribution in a Bubbling Fluidized Bed

In this study, the multi-phase Eulerian–Eulerian two-fluid method (TFM) coupled with the kinetic theory of granular flow (KTGF) was used to investigate the hydrodynamics of particle flows (Geldart Group B) in a lab-scale bubbling fluidized bed. The goal was to improve the bubble flow behavior inside the fluidized bed to improve the distribution of an injected liquid, by increasing the flow of bubbles entering the spray jet cavity and, thus, reduce the formation of wet agglomerates. The effects of a baffle on both the injection level and the whole fluidized bed were studied. Different baffle geometries were also investigated. Adding a fluxtube to a baffle can improve the bubble flows and a long fluxtube works best at redirecting gas bubbles. Baffles tend to smooth out variations in the gas distribution caused by the non-uniform inlet gas distribution. A gas pocket appears under all the baffles.