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• A promising slurry reactor integrating mixing and separation was investigated. • A flow pattern with multiple vortexes relay in the riser was first proposed. • Some empirical models for critical parameters were proposed. • Solid concentration was uneven but with the same particle size distribution. • No bubble existed in the downcomer of this kind of slurry reactor. Based on newly invented internal loop airlift slurry reactor integrating mixing and separation, hydrodynamics and mass transfer under different solid loadings and superficial gas velocities were systematically investigated, and mixing and mass transfer characteristics were studied. Additionally, some empirical models for these critical parameters are proposed. A phenomenon of internal fluid relay circulations in the riser of the internal loop airlift reactor at the high superficial gas velocity was firstly discovered by visual observation and was then verified both by the picture sequences and theoretical analysis, and some new thoughts for structural optimization were also proposed. It was found that the axial solid concentration deviation can be more than 30% and the solid particles were inclined to exist near the wall. Surprisingly, the particle size distributions were found to be the same in the whole reactor. This slurry reactor will be popular in industry with a further structural optimization. [ABSTRACT FROM AUTHOR]

• External airlift loop reactor integrating mixing and separation is first proposed. • Directional flow in external airlift loop reactor and hydrocyclones are integrated. • Mixing, mass transfer, and liquid-solid separation can be simultaneously realized. • Parametric studies of hydrodynamics and mass transfer are performed. • Axial inhomogeneity of solid content and size distribution are investigated. A pilot external airlift loop reactor (EALR) integrating mixing and separation was first proposed by combining directional flow in the EALR and liquid-solid separation in two parallel hydrocyclones. In this developed reactor, mixing, mass transfer, and liquid-solid separation can be simultaneously realized without extra energy input. Technical feasibility was firstly verified, and then hydrodynamics and mass transfer were measured. It was found that the minimum diameter of solid particles retained for circulation was 6.82 μm, and the treatment capacity of clean liquid was up to 3.0 m3/h. Additionally, global gas holdup, liquid circulating velocity, and volumetric mass transfer coefficient increased monotonously with increasing the superficial gas velocity while declined with the increase of solid concentration. Axial inhomogeneity of solid particles was decayed with increasing the superficial gas velocity and solid concentration. This new type of slurry EALR is promising to be applied in the gas-liquid-solid catalytic industries. [ABSTRACT FROM AUTHOR]

In this work the influences of solid viscosity and the way to scale-down traditional drag models on the predicted hydrodynamics of Geldart A particles in a lab-scale gas-solid bubbling fluidized bed are investigated. To evaluate the effects of drag models, the modified Gibilaro et al. drag model (constant correction factor) and the EMMS drag model (non-constant correction factor) are tested. And the influences of solid viscosity are assessed by considering the empirical model proposed by Gidaspow et al. (1997, Turbulence, Viscosity and Numerical Simulation of FCC Particles in CFB. Fluidization and Fluid-particle Systems, AIChE Annual Meeting, Los Angeles, 58–62) and the models based on kinetic theory of granular flow (KTGF) with or without frictional stress. The resulting hydrodynamics by incorporating the different combinations of the drag model and solid viscosity model into two-fluid model (TFM) simulations are compared with the experimental data of Zhu et al. (2008, Detailed Measurements of Flow Structure inside a Dense Gas-Solids Fluidized Bed.” Powder Technological 180:339–349). The simulation results show that the predicted hydrodynamics closely depends on the setting of solid viscosity. When solid viscosity is calculated from the empirical model of Gidaspow et al., both drag models can reasonably predict the radial solid concentration profiles and particle velocity profiles. When the KTGF viscosity model without frictional stress is adopted, the EMMS drag model significantly over-estimates the bed expansion, whereas the modified Gibilaro et al. drag model can still give acceptable radial solid concentration profiles but over-estimate particle upwards and downwards velocity. When KTGF viscosity model with frictional stress is chosen, both drag models predict the occurrence of slugging. At this time, the particle velocity profiles predicted by EMMS drag model are still in well agreement with the experimental data, but the bed expansion is under-estimated. [ABSTRACT FROM AUTHOR]