Study Of Fluidization Characteristics Of Loop Seal Of New Fluidized Bed

Under the background of the continuous improvement of national environmental protection requirements,the application of circulating fluidized bed is becoming more and more important.The traditional calculation method and numerical simulation method are not suitable for the study of new circulating fluidized bed.In this thesis,base on a new type of flow seal valve,the hydrodynamics and fluidization characteristics of gas-solid two-phase flow are studied from three aspects of cold experiment,theoretical calculation and numerical simulation.The mechanism model of flow seal valve is established and a new calculation method of solid particle circulation is explored;A two fluid drag correction model is built to predict the movement of gas-solid two-phase flow in the flow seal valve,which provides a basis for the design,scale-up,regulation and operation of circulating fluidized bed.There is a complex nonlinear interaction mechanism between different characteristic areas in the flow seal valve,which seriously affects the accuracy of the hydrodynamic model of gas-solid two-phase flow in CFB.Therefore,it is a scientific problem to study the mechanism and analyze its influence on the stability of circulating fluidized bed.In this thesis,the critical fluidization velocity of four kinds of silica sand particles with different sizes is measured by the method of experimental simulation and numerical simulation;Base on the original calculation method of solid particle circulation,a new calculation method is proposed,and a new theoretical model is constructed by combining with the new flow seal valve;The feasibility of the calculation formula is verified by comparing the experimental value with the calculated value;The model is used to analyze the influence of left and right blowing on layer height difference,resistance coefficient,dynamic head and other important coefficients;The correctness of the model is verified by experiments,which provides a reference for the improvement of the new flow seal valve.Considering the influence of drag coefficient and relative Reynolds number,a gas-solid drag model under the condition of low-speed air fluidization is established.In order to explore the mechanism of multiple complex disturbance factors on drag force,base on syamlal-o’brien drag model,combined with the relevant experimental data of the new flow seal valve,the model is modified to meet the numerical simulation research of the new flow seal valve.The complex drag model in the simulation of gas-solid two-phase flow is solved effectively,and it is applied to the numerical simulation of the new flow seal valve.Compared with the experimental results,the simulation results are in good agreement with the trend and numerical value.In this thesis,through experimental simulation and numerical simulation,the correctness and applicability of the calculation formula of solid particle circulation and the modified drag force model are verified,the fluidization characteristics of the new flow seal valve are determined,and the general law of gas-solid two-phase flow simulation of the new flow seal valve is revealed,which provides a new idea for the design and research of circulating fluidized bed return valve.