Study On Gradation Influence On Flotation Concentrate Positive Pressure Dewatering Based On Fractal

In recent years, one of the puzzles in the industry of coal preparation is the high moisture content of the flotation concentrate. The main reason is seriously over standard of fine flotation concentrate. After referring to many literatures, summarizing the investigations of formers, the author proposed a new approach of particle size gradation to dewater, positive pressure dewatering system has been established according to the practical situation of coal preparation. A lot of experiments has been performed to investigate the dewatering effects containing different does of slime, different ash content of slime, different fineness of flotation concentrate, discontinuous and continuous particle size gradation. Gradation theory had also been investigated and the relationship between surface moisture and surface fractal dimension, interspace moisture and gap fractal dimension. The results are as follows:The surface area and gaps of flotation concentrate particle swarm have fractal feature, Therefore, fractal model between surface moisture and surface fractal dimension, gap moisture and gap fractal dimension has been established.The content of slime has great effect on the moisture of filter cake. The test result shows that as the content of slime increasing form 30% to 90%, the filter cake moisture content increase form 15.73% to 31.63%. At the same time, the ash content may also has effect on it, when the content of slime is 50%, the moisture may increase 1~2 point as ash content increase 5%.It is different that the variation of filter cake moisture as the mixing content of coarse particle changes. The filter cake moisture gradually reduce as mixing particle size of 1-0.5mm, the moisture reducing slower when mixing over 40% coarse particles. When mixing the particle size of 0.5-0.25 mm and 0.25-0.125 mm, the filter cake moisture reduced at first and then increased while it has the lowest points at 60% and 50% respectively, and the lowest moisture are 15.36% and 19.20%.The content of 1-0.5mm, 0.5-0.25 mm and 0.25-0.125 mm may not exceed 13.33%, 20%, 16.67%, or the dewatering effect will be deteriorated.It is closely related between surface moisture and surface fractal dimension and the relevant equation is Y1=10.615Ds-13.143, and the coefficient is R12=0.8845. While it is also closely related between gap moisture and gap fractal dimension and the relevant equation is Y2=-41.403Dk+76.449, and the coefficient is R22=0.9572.