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Global circulation and liquid back mixing adversely affect the continuous production of a multistage internal airlift loop reactor. A contraction-expansion guide vane (CEGV) is proposed and combined with a two-stage internal loop airlift reactor (TSILALR) to suppress the liquid back mixing between stages. A computational fluid dynamics (CFD) simulation is conducted to evaluate the performance of the CEGV in the TSILALR. The bubble size distribution and turbulent flow properties in the TSILALR are considered in the CFD simulation by using the population balance model and RNG k-ε turbulence model. The CFD model is validated against the experimental results. The deviations in the gas holdup and mean bubble diameter between the simulation and experimental results are less than 8% and 6%, respectively. The streamlines, flow pattern, bubble size distribution, and axial liquid velocity in the TSILALRs with and without the CEGV at superficial velocities of 0.04 and 0.08 m/s are obtained by CFD simulation. It has been shown that the CEGV generated local circulation flows at each stage instead of a global circulation flow in the TSILALR. The average global gas holdup in the TSILALR with a CEGV increased up to 1.98 times. The global gas holdup increased from 0.045 to 0.101 and the average axial velocity in the riser decreased from 0.314 to 0.241 m/s when the width of the CEGV increased from 50 to 75 mm at the superficial gas velocity of 0.08 m/s.

Intact parenchyma cells were successfully isolated from potato tuber and chemically cross-linked with 5–12 wt.% sodium trimetaphosphate/sodium tripolyphosphate for investigating the effect of cross-linking on the structural characteristics and enzyme susceptibility of starch encapsulated within the cell walls. The results indicated that both starch and cell wall polysaccharides were cross-linked, and the swelling power of starch was significantly decreased with increasing degree of cross-linking. The cross-linking reaction also significantly reduced the rate and extent of starch digestion in both intact and disrupted cells after cooking. In addition, the cell-wall barrier effect on starch digestion increased with the degree of cross-linking, due probably to that limited starch swelling and pectin solubilization during cooking process partially protected cell wall integrity and thus decreased cell wall permeability. Overall, the study suggests that chemically cross-linking of cell wall polysaccharides can slow down the in vitro starch digestion of cooked potato foods.

Anion polyacrylamide (APAM) fouling towards anion exchange membrane (AEM) during electrodialysis (ED) of industrial effluent draws recent attention. The fouling dynamics was herein investigated via different approaches in monitoring the variation of the solution and membrane properties. The results showed that conductivity and pH variation is less sensitive than electrochemical signals via transmembrane electric potential (TMEP) and electrochemical impedance spectroscopy (EIS) focusing on micro-scale variation occurred on/near the membrane interface. Initially, the deposition of APAM caused few current transfer limitations as supported by the plateau region for the TMEP profile. Further building-up of APAM fouling gradually hindered the current transfer, resulting into an increased TMEP due to the formation of gel layer on AEM and/or blockage of free volume. Later, the water splitting indicated by an obvious pH variation in dilute and concentrate occurred, which may further accelerate the fouling via modifying the particle size of APAM. EIS successfully distinguished the electrochemical property of membrane bulk and boundary layer, implying the internal fouling is largely responsible for the increased membrane resistance. Future work is suggested to further clarify the external and internal fouling on ion exchange membrane (IEM) and investigate effective fouling mitigation methods in ED.

A multiscale model for simulating the hydrodynamic behavior of catalytic bale packings has been proposed. This model combines computational fluid dynamics (CFD) and macroscopic calculation. At small scale calculation, the CFD model includes 3-D volume-of-fluid (VOF) simulation within representative elementary unit (REU) under unsteady-state conditions. The REU constitutes gauze and catalyst domain, and porous media model is applied. At large scale calculation, a new mechanistic model deduced from the unit network model is employed. Based on liquid split proportion from small scale calculation, liquid distribution of the entire bale packing can be predicted. To evaluate different packing design, three common bale arrangements, i.e. one-bale, nine-bales and seven-bales, are compared. The area-weighted Christiansen uniformity coefficient is introduced to assess the distribution performance. A comparison between simulation and experimental results is made to validate the multiscale model. The present methodology is proved to be effective to analysis and design of catalytic distillation columns.

The response technique was employed to investigate the axial and radial dispersion characteristics of the liquid phase in modular catalytic structured packing (MCSP) reaction elements. Residence time distribution (RTD) experiments were performed at ambient temperature and atmospheric pressure. A two-dimensional dispersion model was solved analytically to determine the axial and radial dispersion coefficients and the dynamic liquid holdup from the RTD curves. Three different reaction elements containing Winpak packing sheets, Mellapak packing sheets, or only catalytic particles were employed. The radial dispersion coefficient in these structures is approximately 1–2 orders of magnitude higher than the axial dispersion coefficient. The axial and radial dispersion coefficients in the Winpak elements are greater than those in the other structures. Thus, it can be concluded that the liquid dispersion characteristics in the Winpak elements are satisfactory. These measured dispersion coefficients enable the reli...