Study On Comminution Dissociation Characteristics And Flotation Test Of Macerals In Low Rank Coal

Low rank coal is the main coal for coal liquefaction technology, whose characteristics are low ash, low sulfur, low phosphorus and good reactivity. Especially coal macerals have important effect on the oil extraction and conversion ratio in coal liquefaction technology. Among the macerals, the vitrinite and exinite are the active component of coal to oil, but the inertinite is the inert component. With the active component increasing, the oil extraction rate and conversion ratio are effectively improved and energy consumption is reduced.From the perspective of coal petrology, the coal macerals were fully dissociated through effective crushing and grinding, then were used to flotation test.Firstly the methods of hand sorting, screening and centrifuging were used to obtain high purity of vitrain and fusain. Then the composition structure, and rock properties of low rank coal, vitrain and fusain were studied, respectively. A series of modern analysis methods, such as coal maceral analysis, X-ray diffraction analysis and SEM analysis etc, were used, whose results suggested that the raw-coal, vitrain and fusain had different maceral content and some differences in the nature, especially in the flotability between vitrain and fusain.For the further dissociation of macerals the crushed raw coal was grinded by the planet type ball mill. The best grinding conditions suitable for the raw coal were as follows: rotate speed is 200r/min, the grinding time is 10 min and the weight ratio of ball to coal is 15:1. The grinded products under the grinding time of 10 min had better dissociation effect of mecerals and the hydrophobic than those under other grinding times, and met the requirements of macerals separation.Through the single factor tests the optimal conditions for the best grinding product are gradually explored, which were as following: pulp density is 60 g/L, the speed of flotation machine is 1800 r/min, inflating volume is 0.20 m3/h, the dosages of collector(diesel) is 0.30 g/L, the foaming agent is 0.10 g/L, the dosages of surfactant is 0.18 g/L. Then orthogonal experiment was implemented to find out the optimal flotation scheme. Comparison results of surfactants showed that the content of vitrinite and inertinite after adding surfactants increased 7.52% and 6.23% percents than under no surfacants, which indicated that the effect after adding surfactans is good.According to the results of in-depth study on separation process of low rank coal, the contents of vitrinite and inernite by the float sink—flotation combined process were 24.85% and 23.47% higher than that of raw coal, respectively; the contents of vitrinite and inernnite by the roughing—concentration combined floatation process were 23.81% and 23.71% higher than that of raw coal, respectively. Both separation process can enrich the macerals, showing good effect.