Influence Of Break Up And Coalescence Models In A Bubbly Flow

Three-dimensional gas-liquid simulations in a cylindrical bubble reactor with an external loop were performed. The effects of average bubble size, bubble size distribution and gas inlet plate geometry were evaluated. The population balance models of Luo and Svendsen [6] and Prince and Blanch [9] were used in order to simulate the breakup and coalescence effects, respectively. The drag force was modeled using the Ishii-Zuber model, which takes into account bubble deformation effects. The k-epsilon turbulence model was applied only for the continuous phase and the dispersed one was considered laminar. Lift, Magnus and added mass forces were neglected. Simulations at different superficial gas velocities were performed using two different inlets: a uniform and a perforated plate entrance. Breakup and coalescence effects were studied only for the uniform gas inlet geometry and the particle size distribution was obtained using a probability density function. Results show that the approach used in this work provided physically consistent results with transient effects in the column. Good agreement of the time-averaged gas holdup with experimental data on gas holdup available in the literature was obtained. It was found that the simulation approach used in this work was able to capture the complex transient fluid dynamics in bubbly flows.Cassanello, M., Larachi, F., Kemoun, A., Al-Dahhan, M.H., Dudukovic, M.P., Inferring liquid chaotic dynamics in bubble columns (2001) Chemical Engineering Science, 56 (21-22), pp. 6125-6134. , DOI 10.1016/S0009-2509(01)00218-4, PII S0009250901002184, Fifth International Conference on Gas-Liquid nd Gas-Liquid-Solid Reactor EngineeringChen, P., Sanyal, J., Dudukovic, M.P., Numerical simulation of bubble columns flows: Effect of different breakup and coalescence closures (2005) Chemical Engineering Science, 60 (4), pp. 1085-1101. , DOI 10.1016/j.ces.2004.09.070, PII S000925090400733XKrishna, R., Van Baten, J.M., Urseanu, M.I., Ellenberger, J., A scale up strategy for bubble column slurry reactors (2001) Catalysis Today, 66, pp. 199-207Krishna, R., Van Baten, J.M., Urseanu, M.I., Three-phase Eulerian simulations of bubble columns reactors operating in the churn-turbulent regime: A scale up strategy (2004) Chemical Engineering Science, 55, pp. 4483-4493Luo, H., Svendsen, H.F., Theoretical Model for Drop and Bubble Breakup in Turbulent Dispersions (1996) AIChE Journal, 42 (5), pp. 1225-1233Maretto, C., Krishna, R., Modelling of a bubble column slurry reactor for Fischer-Tropsch synthesis (1999) Catalysis Today, 52 (2-3), pp. 279-289. , PII S0920586199000826, Kinetics and Modelling of Catalytic Reactions: from Laboratory to Industrial ReactorMatonis, D., Gidaspow, D., Bahary, M., CFD simulation of flow and turbulence in a slurry bubble column (2002) AIChE Journal, 48 (7), pp. 1413-1429. , DOI 10.1002/aic.690480706Prince, M.J., Blanch, H.W., Bubble coalescence and break-up in air-sparged bubble columns. (1990) AICHE J., 36, pp. 1485-1499. , 10 OctSantos, C.M., Dionísio, R.P., Cerqueira, H.S., Sousa-Aguiar, E.F., Mori, M., D́Avila, M.A., Three-dimensional gas-liquid CFD simulations in cylindrical bubble columns (2007) The International Journal of Chemical Reactor Engineering, 5, pp. A90Van Baten, J.M., Krishna, R., CFD modeling of a bubble column reactor carrying out a consecutive A -> B -> C reaction (2004) Chemical Engineering and Technology, 27 (4), pp. 398-406. , DOI 10.1002/ceat.200401968Lin, J., Han, M., Wang, T., Zhang, T., Wang, J., Jin, Y., Influence of the gas distributor on the local hydrodynamic behavior of an external loop airlift reactor (2004) Chemical Engineering Journal, 102 (1), pp. 51-59. , DOI 10.1016/j.cej.2004.01.023, PII S1385894704000804Wiemann, D., Mewes, D., Prediction of backmixing and mass transfer in bubble columns using a multifluid model (2005) Industrial and Engineering Chemistry Research, 44 (14), pp. 4959-4967. , DOI 10.1021/ie049163