| In this paper, the micro fluidized bed reactor analyzer (MFBRA) was as the platform and the phases of gas and solid flow were as the object. The pyrolysis experiments with variable temperature and gas velocity for typical solid materials tar model compound (anthracene) and industrial hazardous waste (fungus residues) were conducted in micro-fluidized bed, the pressure change was tested when the solid materials injected to the reactor in pulse. According to the law of the pyrolysis characteristics of the gas components product and the reliability of bearing temperature, basically determined that the optimal pyrolysis temperature was about 750℃, the optimum air velocity was about 400ml/min, providing necessary basis for numerical simulation and parameter settings.Force analysis was carried out for gas and solid flow in micro fluidized bed, according to the analysis, the possible basic mechanics model was established, and the custom program for different drag models was written independently, numerical simulation for gas and solid flow in micro fluidized bed was conduct by using FLUENT software. First of all, according to the structure and size of the micro-fluidized bed reactor in experiments, the grid file for numerical simulation was established with real way of air distribution. After meshing and achieving independence for mesh, the gas and solid porosity was selected of 0.5, the step size and number of numerical simulation was calculated in micro fluidized bed. Secondly, according to the existing theoretical and experimental research experience for the fluidized bed, three parameter models of Syamlal and Gidaspow model were established. According to the height of the fluidized medium, distribution symmetry and uniformly of solid particles, syamlal drag model was determined that it was applicable to the numerical simulation of the micro fluidized bed with gas and solid, and the second parameter model of that can be as the optimal drag force model to characterize great fluidization for the micro fluidized bed, while fluidization was poor in the Gidaspow model. Finally, on the basis of the existing structure for micro fluidized bed, the flow field characteristics with the drag force model chosen were studied in micro-fluidized bed, finding that problems of the existing reactor, providing an important reference for optimizing reactor configuration.On the basics of the simulation for the existing structure of the micro fluidized bed, the optimal design was conduct for the shape, media placement and built structure. Firstly, the multi-rib structure enhanced the heat transfer effect around micro fluidized bed for the shape optimization structure to improve the original concentration distribution. According to the distribution of the speed vector, polycyclic-nuclear structure has been improved and the number of this structure reduced significantly, closing to the experimental condition. Secondly, the bi-level media arrangement was used, the distribution of velocity vectors characterize that the typical fluidization has been formed. Finally, in the optimization structure of the built-in, the height of flow was improved effectively, the concentration distribution of solid phase was more uniform and dilute phase was the basics. Two optimization model were formed:the multi-rib with bi-level media arrangement model and the multi-rib with built-in structure model.At the same time, it was found that 0.3mm diameter of the materials still fit to the improved micro fluidized bed by simulating, verifying the rationality and scientific of selecting media size in experiment. According to the pyrolysis characteristics (duplication degree of x-t curve) and the value of the activation energy calculated, it can be found that the two optimization models of micro fluidized bed showed high accuracy in the dynamics calculation, verifying the results of the numerical simulation and the optimization model. |
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