Investigation On Fluidization Characteristics Of Globules Of Raw Material By Experimentation And Numerical Simulation

Based on analyzing two chief methods to calcinations technology of clinker (rotary kiln andvertical kiln) in present, this paper dealt with a new calcinations technology of clinker--fluidization calcinations kiln. Before researching the technology, it is necessary to understand the fluidization characteristics of globules of raw material completely. The fluidization characteristics were investigated by experimentation and numerical simulation.The research of the fluidization calcinations of clinker has been investigated several decades, but the technology is not used up to now. The latest successful research was done by Japanese scientists, now the large scale experimentations were doing. But the basic research of large particles fluidized bed is not perfect in present, only a little of reference could be obtained.In the paper, the equipment of fluidized bed in experimentation was designed by the experimental formulas for small particles fluidized bed. The results calculated were compared and verified with the results of experimentations, it was an effective method to design the large particles fluidized bed in present. The minimum fluidized velocity which was calculated by the formulas rooted from Ergun equation in calculating is according to the experimentation result well. The large particles fluidized bed was investigated by both experimentation and observation In the experimentation, a complete fluidization curve could be divided into five parts by the superficial gas velocity; they are the part of fixed bed, particle position adjustability, some particles moving, slugging fluctuation and complete fluidization. The characteristics and the phenomena of every part were described, analyzed and concluded. The phenomena were caused by the characteristics of the large particles themselves. In every part, the height of the bed is measured, and the changing of bed height with superficial gas velocity is different in every part. By comparing the beginning fluidized velocity, minimum fluidized velocity and complete fluidized velocity with the beginning velocity of every part, some relationships between each other were found. The beginning fluidized velocity and complete fluidized velocity were defined again according to the characteristics of large particle fluidized bed.In this paper, the fluctuation of the bed height was used to describe the stability. Theconclusion shows that the smaller the particles are in fluidized bed, the better the stability of bed is under one initial bed height, and there is a optimum height to one type of particles in the fluidized bed. It is one of the methods for selecting initial bed height. Of cause, the initial bed height selection must be connected with the complete velocity and the pressure drop of fluidized system yet.In numerical simulation, the simple one-dimension fluid model and direct element method to particle were used. The investigation on the dynamics of particles collision was based on assuming the collision between particles is an instantaneous process. The time step of simulation is stable. Good results were obtained, and the movement of every particle could be known, it is very useful to research the large particle fluidized bed. The fluctuation of pressure drop of bed was calculated, it shows that the larger particles bed is instability, and accords with experimentation results. The result of the simulation also pictured growing-up and crashing of the bubble in the bed yet, that is said it is difficult to make the large particle fluidized bed very stability.