Study On Dewatering Process Of Oil Shale

Because of the huge reserves of oil shale as a kind of fossil fuels, it is widely used in chemical industry, pharmacy, agriculture, construction and so on. There are two most important aspects of the application of the oil shale. On the one hand, oil shale is used to produce shale oil, on the other hand, burning oil shale to provide energy for power generation. According to the report, bursting crack phenomena is related to porous structure and10%-30%high moisture content of oil shale in the carbonization process. Bursting crack will increase the resistance in carbonization process, influence the stability of the operating system, at the same time make less use of the energy. Therefore, it’s very important to dry oil shale lower moisture content before carbonization to prevent bursting crack happening.This research discusses the effects of drying medium temperature, particle diameter on the drying rate of the single oil shale particles in the superheated steam and hot air. And the drying rate in both drying drying medium under the same conditions are compared, the result indicates the quicker drying rate and shorter drying time, the smaller the particle diameter of oil shale and the higher the drying temperature of superheated steam or hot air. Based on the contrast of average drying rate in superheated steam and hot air under the same drying conditions, the inversion temperature of9mm,7mm,5mm oil shale in particle diameter can be obtained, is respectively154℃,179℃,177℃. Inversion temperature of9mm,7mm,5mm oil shale particles is respectively153℃,175℃,179℃based on the contrast of maximum drying rate in both drying mediums. The value of inversion temperature is variable, inversion temperature of9mm as the largest particle diameter is minimal, but smaller particle diameter appears to have no influence on the inversion temperature, such as7mm and5mm.By means of Yoshida T Inversion Temperature Model, the theoretical inversion temperature of9mm,7mm,5mm oil shale particles was derived, it is respectively169℃,176℃,180℃. Observed from the calculation, the theoretical value approximates experimental value. Drying kinetic experimental data were simulated by thin-layer drying model, result shows modified Page model(Ⅱ) is fit to describe the drying process of oil shale.Bursting crack experiments of oil shale were carried out under the condition of superheated steam and hot air, respectively. Analysis indicates the greater ratio of bursting crack of oil shale with higher medium temperature, larger particle diameter and higher initial dry basis moisture content.And under the same conditions, the ratio of bursting crack in superheated steam is always smaller than that in hot air.For example, the ratio of bursting crack in superheated steam and hot air is respectively0.8,0.9at250℃,9mm.This paper also discusses the effect of bursting crack on the crushing ratio,dust ratio,dust particle diameter at the fluidization of air.The result indicates bursting crack increases rapidly crushing ratio, dust ratio,but the dust diameter decreases.The investigation of oil shale pyrolysis shows that multi-rate method such as FWO and DAEW can be used to explain the mechanism of oil shale pyrolysis. Activation energy calculated through FWO and DAEW is respectively92712.9J/mol～248925.8J/mol,86710.9J/mol～249297.8J/mol.