A membrane‐assisted stirred slurry reactor is developed by equipping a membrane tube into a stirred tank. Liquid‐solid flow is simulated by the Euler‐Lagrange method with filtration and particle deposition models. Acceptable predictions on the cake mass and particle deposition patterns are achieved by comparing with experimental data. The introduction of the membrane tube generates an asymmetric flow field. Shear stress on the membrane surface has a direct influence on the particle deposition. Increasing the impeller rotating speed leads to larger shear stress and mitigates the particle deposition. The cake mass is reduced by placing the membrane tube close to the impeller. The upward liquid flow pumped by the pitched‐blade impeller results in low shear stress and the vertical‐blade impeller is preferable.
BACKGROUND: The interaction between particles and bubbles commonly occurs in catalysis, flotation and medical processes. Compared with the overwhelming amount of research dedicated to particle adhesion on gas bubbles, there is less on the rebound behaviors of hydrophilic particles on bubbles. Carrying out studies in order to understand the effect of particle size and liquid properties on rebound behaviors becomes an essential task. RESULTS:The rebound velocity and angle of a particle are small when a collision takes place near the top surface of a bubble. At the bubble top, gravity counteracts the upward rebound. Smaller rebound velocity is found for small particles due to inertia. The contact time between particle and bubble increases with an increase in particle size. The surface tension almost has no effect on the rebound velocity and angle of particles. By increasing liquid viscosity, the rebound velocity of the particles decreases and the contact time increases. CONCLUSIONS: A hydrophilic particle cannot adhere on a gas bubble in pure water. However, at very large viscosity, adhesion takes places. In processes where longer contact time between hydrophilic particle and gas bubble is desirable, increasing liquid viscosity and particle size should be the choice, while efforts to change the surface tension are found to be unnecessary. Hydrophilic activated carbon particles have better dispersion in water and shorter contact time on bubble surfaces than hydrophobic N-doped carbon particles.
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