Showing papers in "Journal of Chemical Engineering of Japan in 2017"

Immersed Boundary Method with Artificial Density in Pressure Equation for Modeling Flows Confined by Wall Boundaries

Abstract: The immersed boundary (IB) method is a promising technique for the numerical simulation of complex microchannel ows. However, numerical tests revealed a loss of wall impermeability for certain ow cases leading to unphysical results when using a standard IB method. To solve this problem, we propose a novel arti cial density technique incorporated in the pressure solution for IB methods. The pressure equation is modi ed by scaled density coe cients in IB domains, which re ects the e ect the boundary screening. The proposed model is as simple and e cient as the original IB method, and it can eliminate the spurious velocity penetration. Numerical results are shown to justify this method. Its application to a branched microchannel is also presented in the last part of this study.

Iterative Learning Control Integrated with Model Predictive Control for Real-Time Disturbance Rejection of Batch Processes

Abstract: In the present paper, iterative learning control (ILC) is integrated with a model predictive control (MPC) technique to reject real-time disturbances. The proposed scheme is called iterative learning model predictive control (ILMPC). ILC is an e ective control technique for batch processes, but it is not a real-time feedback controller. Thus, it should be combined with MPC for real-time disturbance rejection. The existing ILMPC techniques make the error converge to zero. However, if the error converges to zero, an impractical input trajectory may be calculated. We use a generalized objective function to independently tune weighting factors of manipulated variable change with respect to both the time index and batch horizons. If the generalized objective function is used, output error converges to non-zero values. We provide convergence analysis for both cases of zero convergence and non-zero convergence.

Modeling and Scaling Up of Industrial Spray Dryers: A Review

Abstract: The paper presents a review of research works, experiments and simulations on spray drying in the industrial scale. The research area in the industrial spray drying process covers control of powder properties (bulk density, morphology), particles agglomeration ( nal PSD), residence time, wall deposition and safety of the process and the product. Limited number of literature references on spray drying in the industrial scale is due to high costs of running experiments and validation of theoretical models. Recent works on hydrodynamics in spray towers showed transient, oscillating, 3D ow of dispersed and gas phase which results from construction of inlet and exhaust ducts and swirl decay due to wall roughness (deposits). Applications of the most advanced and accurate empirical methods to calculate spray drying kinetics in industrial scale; the Characteristic Drying Curves (CDC) and the Reaction Engineering Approach (REA) were presented. The main obstacles denying con dent scaling up of the spray drying process; lack of dynamic similarity between small and large units, gas turbulence modelling, determination of drying kinetics and neglecting of agglomeration process are highlighted. Methods of modelling of the agglomeration process in spray drying (transition functions, full scale agglomeration) are described. Examples of modelling and measurements of hydrodynamics, wall deposition, agglomeration process and drying kinetics in the industrial towers are presented and discussed.

Classification Characteristics of a Cyclone Type Classifier with Improved Collection Boxes for Separating Particles near the Wall Surface

Abstract: Cyclone separators are used in many processes to remove powders for collection in a wide range of diameters. When the cyclone separator is used as a classi cation device that requires high e ectiveness, the 50% cut-o size (Dp50) is restricted to less than several microns owing to the strong centrifugal force. We developed a cyclone-type classi er to e ectively classify coarse particles collected by the normal cyclone, as discussed in our previous study. The classi er comprises inner and outer collection boxes with a sloping channel region between the upper sections. The sloping channel could derive the additional air, called blow-up ow, from the tangent nozzle established in the outer box. The blow-up ow becomes con uent with the main swirling ow of the cyclone. In the channel, the ne particles a ected by the drag of the blowup ow were collected in the inner box. Additionally, the coarse particles a ected by the centrifugal force induced by the swirling ow were collected in the outer box. The previous study, regarding a classi er with a channel length of 6 mm, demonstrated that Dp50 and the e ectiveness of the classi cation κ, which is the ratio of the 25% cut-o size to the 75% cut-o size (Dp25/Dp75), increase linearly with the increase in blow-up ow rate (Δq). In this study, we increased the channel length from 6 to 23 mm. This resulted in the following bene cial characteristics for separating acrylic particles having a size distribution of 15–35 μm. Unlike the previous study, Dp50 depended on the main ow rate at the entrance regardless of Δq since the increase in Δq increases the centrifugal force, which acts simultaneously on the Dp50 particles, and the drag force. Meanwhile, κ increased signi cantly with the increase in Δq. The classi er classi ed the particles with high e ectiveness (κ ranging from 0.75 to 0.92).