Numerical Simulation Of Heat And Mass Transfer Of Biaxial Paddle Dryer

Due to the advantages of compact structure, small occupied area, large heat transfer area per unit volume, the biaxial paddle dryer is widely used in metallurgy, chemical industry, food processing and other fields. However, as a kind of indirect heating dryers,its heat and mass transfer mechanism is very complicated, the design parameters of the dryer mainly empirically selected, and the operating parameters mainly rely on the experience and repeated experiments to determine. At present, the lack of theoretical system can effectively guide the practice, leading to the dryer drying effect is not ideal, even it is difficult to meet the requirements of drying. Therefore, the effects of heat and mass transfer mechanism and operating parameters of biaxial paddle dryer for drying quality is a subject worthy of further study.Because there are many factors affecting the heat and transfer of biaxial paddle dryer,many factors often require a large number of experiments, and even some factors can not effectively carry out research,even though establish a testing system. In order to save a lot of manpower, material resources and cost. Therefore, in this paper applying the sulfur tailings as the drying object, according to the theories of heat transfer and fluid mechanics, analysis and study of the heat and mass transfer mechanism of the biaxial paddle dryer have been carried out deeply,including that establishment of the CFD model, and simulation of the heat and mass transfer of the biaxial paddle dryer based on the FLUENT to explore the motion law of gas and sulfur tailings, and reveal of the gas-solid two-phase flow field and temperature field in the dryer and the different blade speed and different steam temperature on the effects of outlet material moisture content. The main works in this thesis can be concluded as followings:1) The drying process of sulfur tailings in biaxial paddle dryer have been theoretically analyzed. The particle heat transfer model based on the movable heating was used to analyze drying process of sulfur tailings in biaxial paddle dryer in theory, and to lay the foundation for the subsequent numerical simulation of heat and mass transfer in the dryer.2) The flow field, temperature field of gas phase in the biaxial paddle dryer and the flow field of single blade have been numerically simulated. The three-dimensional model of the biaxial paddle dryer has been established by using UG8.0 software. Starting from the heat and mass transfer mechanism analysis, CFD model of biaxial paddle dryer has been established.By using FLUENT, the flow field, temperature field of gas phase in the biaxial paddle dryer and the flow field of single blade have been numerically simulated.3) The gas-solid two-phase flow in the biaxial paddle dryer have been numerically simulated. Based on the CFD model established in the step 2), and by using FLUENT, the gas-solid two-phase flow in the biaxial paddle dryer have been numerically simulated, in order to reveal the different blade speed and different steam temperature on the effects of the outlet material moisture content.In summary, the researches in this paper provide a scientific basis for the structure optimization and reasonable selection of operation parameters of the biaxial paddle dryer and the improvement of the drying quality.