Fluidized Behavior And Drying Characteristics Of Oil Shale In Mobile Fluidized Bed Dryer

With the short of oil resource and the increasing requirement of energy source today, it attracts people's attention all over the word as a kind of replacement resource of oil that has huge reserves and great value in use. According to the reports, cataclasm phenomena is relevant of structure and moisture content of oil shale in carbonization process. In order to avoid it happening and increase yield of shale oil, dehydration process is used before carbonization in this paper. Therefore, a new drying equipment is invented to use in drying process of oil shale that has the wider particle size distribution and the higher moisture content, we call it mobile fluidized bed dryer.In mobile fluidized bed dryer, the effect of various factors and characteristic of fluidization and heat transfer is discussed. Drying curves and drying kinetic models are obtained respectively by drying kinetic experiments, the method of N2 adsorption and method of SEM are used based on fractal theory to research interior structure of oil shale and the moisture transfer mechanism, then the formula of drying rate constant is educed.Experiment results by the method of N2 adsorption and method of SEM show that oil shale is a typical porous material with opened capillary pore structure, the particle size distribution is in range of 0.4 and 40nm, its surface area is 1.201 m2/g, pore volume is 0.046cm3/g, pore curve fractal dimension is 1.121 and pore area fractal dimension is 2.464.Analysis indicates by hydrodynamics experiment in mobile fluidized bed dryer that export material speed changes with time periodically by mechanical force function, but average discharging rate equals feeding rate and export material composition almost equals import material composition in a period. In a word, detained phenomenon won't appear in mobile fluidized bed dryer when drying system is operated steadily. It's feasible measure that part gas circulation mobile fluidized bed dryer is used for drying of oil shale continuously, oxygen content of import smoke gas and export smoke gas are 6.4%and 9.0%respectively, the temperature of export smoke gas is controlled by feeding rate and mechanical force function.5%moisture content of oil shale can be reached when entry temperature of smoke gas is 350℃. The results of drying kinetics of oil shale show that modified PageⅠof thin layer drying model fits to simulate drying process of oil shale, the drying formula is drying rate formula is drying time exponent n is 1.0668 and drying rate constant is k=5.588×10-29.826T4.103d0-6.059 0≤d0≤6mm; k=1.905×10-23.621T3.578d0-5.283 6≤d0≤8mm. Drying process mechanism of oil shale belongs to interior diffusion control.