This paper describes a dynamic membrane filtration system that combines crossflow filtration and centrifugal separation in a rotating tubular membrane. Because of the noslip boundary condition, membrane rotation leads to higher centripetal force near the lumen wall than introduction of a rotating flow. In this fundamental exploratory study, hollow glass microspheres (5 to 35 µm diameters) serve as model low-density, separate-phase foulants during filtration of aqueous suspensions through a tubular ceramic membrane (nominal 0.14 µm pore size). At low crossflow rates, membrane rotation at 1725 rpm decreases fouling and shifts the microsphere size distribution in the membrane cake towards smaller diameters. Force balance calculations suggest that centripetal force should move particles with diameters >~17 μm away from the lumen surface. Moreover, azimuthal and longitudinal shear stresses will also selectively remove larger particles from the membrane cake. Computational fluid dynamics (CFD) simulations show that the rotational flow does not fully develop in the membrane lumen and the fluid radial velocity peaks before the membrane wall. Both of these factors will decrease movement of low-density particles away from the lumen wall. Nevertheless, consistent with experimental data, CFD simulations show greatly decreasing encounters of particles with the membrane wall as particle size increases.
In this paper, the new separation structure (VDWDWC) for separation of a quaternary system is proposed for the first time, which has lower energy consumption and higher separation efficiency than the traditional three‐column and Kaibel column. Sensitivity analysis and response surface optimization (RSM) are applied to the structural design and parameter optimization of VDWDWC. In addition, the dynamic control of VDWDWC is also investigated. Specifically, the performances of temperature‐composition cascade control (TC‐CC) with and without feed‐forward ratio control are compared and analyzed. The results suggested that the TC‐CC structure can achieve outstanding controllability for VDWDWC, when the feed flow rate and feed composition is disturbed. In particular, TC‐CC with feed‐forward ratio control has better dynamic response: the maximum deviation was reduced by 53.7%, and the settling times are significantly shortened, while the steady state deviation of product purity was slightly reduced.
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