Numerical Simulation On The Mixing Characteristics In Micro Fluidized Bed

The Micro Fluidized Bed Reaction Analyzer (MFBRA) developed by Institute ofProcess Engineering, Chinese Academy of Sciences has the isothermal differentialcharacteristics and is suitable for gas-solid fast reaction analysis including themeasurement of reaction rate and kinetic parameters. The instantaneously intensiveparticle mixing between trace sample in milligrams and high-temperature fluidizedmaterial is the essential condition to keep isothermal differential characteristics of themicro fluidized bed (MFB) reactor. Numerical simulation method can represent thecomplex multiphase mixing process which is difficult to describe through theexperiment accurately, so it is of great practical significance for the simulation on themixing characteristics in MFB. Therefore a study on numerical simulation was carriedout for the sample-in device as well as the flow and mixing of particulate materials inMFB, and the results provide theoretical direction to the design and optimization ofthe key components.Firstly, a research history of the MFB was summarized, and the feature andsimulation state-of-the-art which is widely used on the gas-solid flow were presentedat the same time. It was concluded that the simulation approach is necessary to beadopted to described the mixing characteristics in the fluidized bed. Then athree-dimensional numerical simulation based on Eulerian multiphase model wascarried out for the main reactor in MFBRA, and the results indicate that the pulsinginjected gas has a great effect on the gas-solid flow.On the basis of the research before, a further simulation study was taken on theMFB connected with different gas jet structures. The instantaneous flow structuresand quantitative mixing characterizations for different injector structures and locationswere obtained. Comparison revealed good qualitative coincidence betweenexperiment and simulation. The simulation results suggest that the injector shouldavoid the bending angle that confronts the injected gas with the fluidizing gas or leaves the trace sample in the injector. With the parameter research of the mixingquality, an optimal combination of pulsing gas velocity and sample size was obtained.Then a DEM-CFD coupling method based on two-fluid model for irregular gridwas proposed in this thesis, and a pilot study of gas-solid flow in MFB was conductedwith the mentioned DEM-CFD method. The simulation results show that thecharacteristics in flow field match the common fluidization phenomenon.Finally, the main conclusion of the present study and prospect on simulations inMFBRA were revealed.