The γ-CT Measurement And CFD Simulation Of Dispersed State Of Gas-liquid Two-phase Flow In Rushton Stirred Tank

Rushton gas-liquid stirred tank reactors are widely used in chemical industry,pharmaceutical industry, energy, environment, food industry and biochemical, etc. Itsinternal flow characteristics and dispersed state of each phase both have an importantinfluence on industrial production process. It is very necessary to study the mixingparameters of gas-liquid flow, so as to guarantee the smooth chemical process. But becauseof the strong randomicity and complexity of multiphase flow, the multiphase flow dispersedstates are still difficult and hot spots in investigation, needing to be further studied.Based on the Poisson distribution models of emitting signals from radioactive sourceand received signals by the fan-beam detectors, and the binomial distribution model of thesignals that absorbed and attenuated by gas-liquid flows, the two dimensional spaceparameter of the absorbed and attenuated γ-ray signals of the horizontal cross section ofgas-liquid flows in the Rushton stirred tank reactor were estimated by using the estimationmaximization likelihood method, based on the received γ-ray signals of experimentalsample space. The model of the digital image formation for gas holdup distribution in theRushton stirred tank by using137Cs γ-ray CT was derived and established.In the current work, three flow regimes of flooding, loading and complete recirculationin a Rushton gas-liquid stirred tank were chosen to study. Compared the experimental datawith the classic flow regime map, and achieved good agreement. CT scan measurement ofthe Rushton stirred tank was carried out by the use of137Cs γ-ray CT scan system. Both thequantitative digital distribution curves of gas holdup and their qualitative colour CT imageof the above regimes were obtained through data processing and image reconstruction, withan emphasis on the detailed information of gas holdup distribution near the impeller ofregion of “3-3” regimes.The dispersed state of gas-liquid flow in the Rushton stirred tank was simulated byusing the euler-euler double fluid model, combined with the Schiller&Naumann draggingcoefficient model, the k turbulence model, the break-up model and coalescence model.Compared the numerical simulation ones with the experimental ones, the resultsanastomosed preferably in the impeller region, and have some guidance on the mixingprocess of multiphase flow.