Theories And Technologies Of Gas-Solid Separation In Symmetrical Swirling Flow

Cyclone separators, as important gas-solid phase separation equipments, have been widely used in the field of gas-particle separation, product recovery, particulate size classifiers and pollution control. At present, cyclone separators have also demonstrated the irreplaceable use value. In order to adapt well to the extremely harsh operating conditions and special requirements including the high temperature and high pressure, fluidization, energy utilization and environmental protection, a novel cyclone separator with symmetrical spiral inlet channel (SSIC) is conceived and designed for engineering and processing application. The performance characteristics including collection efficiency and pressure drop for this cyclone separator is investigated by using the experimental, theoretical and numerical methods in this work.Firstly, on basis of the overview of current status on cyclone separator geometries, a new cyclone separator with symmetrical spiral inlet is presented in terms of the Stairmand high efficiency cyclone configuration. The separation characteristics and pressure drop characteristics for four kinds of cyclone separators with different inlet type are measured by using mass analysis method and differential pressure method, and are compared as functions of inlet type and flow rate. Moreover, the performances of cyclone separators are evaluated according to the grey correlation evaluation model. The results show the cyclone separator with symmetrical spiral inlet channel provides the optimized performance.Secondly, theoretical investigation on both the collection efficiency characteristics and pressure drop characteristics are carried out for symmetrical spiral inlet channel cyclone respectively. A new theoretical method for evaluating cyclone efficiency is developed based on the investigation of flow pattern, the critical particle size separation theory and the boundary layer separation theory. The radial particle concentration gradient, instead of the usually assumed uniform radial particle concentration within the cyclone, is considered in this mathematical model. The local particle concentration and the cyclone grade efficiency can be calculated on the base of a time-of-flight model in terms of the particle size distribution of the feed. The availability of the method is verified by comparison of the calculated grade efficiency with experimental data and theoretical counterparts in the literature. On the other hand, a new theoretical model was developed for prediction of pressure drop across cyclone separators. This model includes the effect of the geometrical dimensions and flow parameters, and assumes that total pressure drop consists of five main partial pressure drops due to gas expansion at the separator entrance, wall friction within the separator, swirling motion of gas, gas flow through the outlet pipe. The availability of themethod is verified by comparison of calculated value with experimental data as well as with the other models for different dimensions of cyclones. The both theoretical results indicate a good agreement with the experimental data.Thirdly, to analyze the separation mechanisms of symmetrical spiral inlet channel cyclone, A Computation Fluid Dynamics (CFD) simulation is performed for prediction of gas flow pattern and particle collection efficiency in this new type cyclone separator. The governing gas flow equations, along with the three-dimensional Reynolds Stress Model (RSM), are solved using the finite volume method and the SIMPLE pressure-velocity coupling algorithm in a body-fitted coordinate system. A particle tracking method (PTM) is employed to calculate the particle grade efficiency. The numerical flow simulations confirm the main characteristics of vortex structure and particle separation inside the main body of the cyclone. On this basis, a numerical method for calculating the collection efficiency and pressure drop is proposed. The comparisons between numerical and experimental results have to be regarded as a reasonable agreement, and also demonstrate CFD is a liab...