CFD simulation and experiment of residence time distribution in short-contact cyclone reactors

Hydraulic Characteristics, Residence Time Distribution, and Flow Field of Electrochemical Descaling Reactor Using CFD

This paper uses computational fluid dynamics (CFD) to simulate flow field distribution inside an electrochemical descaling reactor in three dimensions. First, the reactor flow field was obtained by steady-state simulation, and the grid independence was verified. Then, the steady state of the flow field was judged to ensure the accuracy of the simulation results. Transient simulations were performed on the basis of steady-state simulations, and residence time distribution (RTD) curves were obtained by a pulse-tracing method. The effects of plate height and plate spacing on reactor hydraulic characteristics (flow state and backmixing) were investigated using RTD curves, and the results showed that increasing the plate height and decreasing the plate spacing could make the flow more similar to the plug flow and reduce the degree of backmixing in the reactor. The flow field details provided by CFD were used to analyze the reactor flow field and were further verified to obtain the distribution patterns of dead and short circuit zones. Meanwhile, information regarding pressure drops was extracted for different working conditions (490, 560, and 630 mm for pole plate height and 172.6, 129.45, and 103.56 mm for pole plate spacing), and the results showed that increasing the pole plate height and decreasing the pole plate spacing led to an increased drop in pressure. In this case, a larger pressure drop means higher energy consumption. However, increasing the pole plate height had a smaller effect on energy consumption than decreasing the pole plate spacing.

Numerical simulation and experiment on catalytic upgrading of biomass pyrolysis vapors in V-shaped downer reactors

Catalytic upgrading of biomass pyrolysis vapors is an effective utilization technology of biomass energy. Based on the disadvantages of commonly used reactors, the V-shaped downer reactors were designed to increase gas-solid two-phase turbulent intensity, contact frequency and then increase the catalytic efficiency in short residence time. The catalytic upgrading of pyrolysis vapors in V-shaped downer reactors in terms of hydrodynamics, chemical reaction and residence time distribution were analyzed by CFD simulation and experiment. The results indicate that the solid concentration gradient decreases while flowing down. The overall mass fraction of the bio-oil vapors is around 50%. The mean residence time of catalysts in the V-shaped reactor is 2.0 s-3.0 s. The effects on product yield and residence time distribution were investigated for optimizing product selectivity and the performance of catalysts. In this paper the optimal flow rates of gas and catalysts are v_g = 1.2 m s^-1, v_s = 0.4 m s^-1.