Study On The Process And Equipment Of Taixi Anthracite Purification

Systematic research and experiments have been done to reduce excessive ash in coal. Bottlenecks restricting the development of coal based materials have been studied using Taixi anthracite as the model coal. Preparation of super-clean coal by maceral separation was investigated. It was concluded that a new technique using two de-ash steps and a heavy media cyclone employing equal density separation could prepare purification coal. A density current model describing the density and velocity fields in the cyclone was developed. Equipment to perform high-precision separations was constructed. This is called the Refine-type Heavy Medium Cyclone. The formation and sympathetic absorption of the suspension pressure wave was modeled. A new method to adjust the density of the media that is based on a self-balancing principle is described. This allowed precise adjustment of the heavy medium. The feasibility of using flotation to purify Taixi anthracite was also explored.The results show that essence of coal purification is to clean vitrinite in the coal. Coal purification is the process of maceral separation. Equal density re-separation of the initially purified product helps improve the total precision of the separation and the purity of the cleaned coal. To achieve this end a two segment jigging technique for pre-separation, and two stage heavy medium cyclone for equal density concentration was designed.A combination of hydrodynamics and thermodynamics was adopted to analyze the radial diffusion and sedimentation in the medium. These appear to be the main cause of the graded density distribution that develops in the cyclone. The density and velocity fields are distributed in the cyclone in a way that satisfies the density current model. The inner area is the forced whirlpool zone where the radial density and the radius of gyration are linearly related isopycnic surface is truncated cone. An eddy free flow area exists in a thickening outer layer of screw flow. In this region the density and gyration radius follow an exponential function (ρ=ρl +a?Rk). In these regions the mixed fluids move in the axial direction along equal density lines. CFD software was adapted to allow simulation of the velocity and density fields in the cyclone. The velocity distribution in the flow field is consistent with density distribution of the suspension. This validates the density current model. Feed enters the cyclone, reaches and follows the corresponding equal density layer, where separation takes place.The flow field had been greatly influenced by the medium inlet form and the counterpressure of the heavy products, the separation precision and abrasion resistance of cyclone had been improved through the optimizing of the relative parameters. Two types of selected cylinder heavy medium cyclone with radiuses ofΦ500/400,Φ800/650 had been developed, E≤0.015.The model of suspension pressure wave and resonance absorption had been put forward through the force analysis of the fluid: the inlet pressure variety of heavy medium cyclone could be separated into two kinds of pressure waves: the low frequency wave which comes from the change of liquid level in the medium bucket, and the high frequency pressure wave which is from the fluid oscillation. When the self-oscillation frequencyof high frequency wave equaled to the frequency of self-oscillation of air spring, the resonance oscillation will be achieved. The new method of medium preparation based on decreasing medium integrity granularity formation was established, high efficient heavy medium separation density automatic control system based on self-balance was proposed, and the fluctuating range of the medium density could be controlled in±0.002 kg/L; and the pressure fluctuating range of the cyclone inlet was less than±0.001 MPa; and medium consumption is less than 0.60kg/tThe research results of this paper had been applied in Taixi coal preparation plant, and the purification coal product with ash Ad<2.00% had been produced, and satisfied technical and economic effects had been obtained.