The Study Of Flotation On Liushuhe Oil Shale

Oil shale is an abundant fossil energy. Once converting it into shale oil, its reserves will be much richer than oil resources. The properties of oil shale are similar to coal, but oil shale’s mineral content is higher than coal’s. It can produce shale oil through pyrolytic process, which properties are similar to crude oil. Thus oil shale is widely seen as a promising alternative energy. China and some other countries already have extracted shale oil from oil shale through the pyrolytic process, and achieved good economic benefits. However, due to oil shale contains a lot of minerals, which will be transferred into the char after carbonising, so that the ash content of char is particularly high. Char with a high content ash has relatively low calorific value, which limits its utilization ways, and reduces its economic value. Therefore we try to use the method of flotation to study Liushuhe oil shale, which is a simple and efficient method of reducing the mineral content.Kerosene was selected as the collector, and octanol was chosen as the foaming agent. Firstly we researched the influences of pulp concentration, collector dosage, frother dosage, agitating speed, and air velocity on flotation. And found the best conditions are pulp concentration50g/L, collector dosage1.4kg/t, frother dosage400g/t, agitating speed1500r/min, and air velocity240L/h. Under these conditions, the yield of fine shale was61.38%, combustible matter recovery was65.92%, ash rejection was32.16%, and the perfect index of flotation was24.28%. We also explored the influence of ultrasonic on flotation, and did not find significant effect.Flotation is to improve the yield of fine shale as much as possible under the condition of reducing the ash content. Orthogonal experiments were carried out to explore the influences of pulp concentration, collector dosage, frother dosage, and agitating speed on ash rejection. The means of analysis of variance statistical method was used to explore the rate of contribution of each controllable factor on the ash rejection. It was found that the sequence of the rate of contribution was agitating speed, pulp concentration, frother dosage, collector and dosage. The contribution percentages of each factor were56.01%,24.27%,10.56%and1.30%respectively.Some researchers improved the floatability of lignite by adopting the method of thermal treatment. We attempted to use this method to improve floatability of Liushuhe oil shale. Firstly, the floation study on oil shale was carried out. The oil shale of this study was already through500℃thermal treatment. Then found the best conditions, they were pulp concentration 40g/L, collector dosage5kg/t, frother dosage1800g/t, agitating speed2600r/min, and air velocity250L/h. Under these conditions, the yield of fine oil shale was83.45%, and the combustible recovery was89.48%. We also did experiments of flotation with the original oil shale, and the oil shale was handled at100℃,300℃,700℃under the same conditions and compared with oil shale that was handled at500℃. We found that with the improvement of pyrolytic temperature, the yield of fine oil shale and combustible matter recovery improved on the whole. Through experiments, it was found that the thermal treatment decreased the density of the oil shale. Relatively low density is in favour of flotation. It is the change of density that led to the improvement of floatability, rather than hydrophobicity.We also explored the influences of particle size on flotation and found that too big or too small particle size is adverse for flotation, while moderate granularity is good for floation.