【作者】 王羽玲；

【导师】 赵跃民；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2009， 博士

【摘要】 为深度降低煤的灰分,解决制约煤基材料发展的瓶颈问题。论文以太西无烟煤为研究对象,进行了相关的试验研究,得出了通过煤岩组分分离制备超纯煤的方法;制定了分步脱灰与重介两段等密度精选相结合的超纯制备工艺。通过对加重质在旋流器内的沉降与扩散过程分析,建立了重介旋流器内密度场和速度场分布的异重流模型;研制出高精度分选设备——精选型圆筒重介旋流器。提出了悬浮液压力波形成与共振吸收模型,以及基于工艺自衡的介质密度调控新方法,开发了高精度重介调控技术。探索了破碎后用浮选法进行超纯制备的技术可行性。煤炭超纯制备的实质就是要提纯煤中纯净的均质镜质体,煤炭的超纯制备过程也就是煤岩组分的分离过程。研究结果表明,对粗选轻产物进行等密度精选,有利于提高综合分选精度和轻产物的纯度。由此,制定了两段跳汰初选——轻产物两段等密度重介精选的工艺流程。采用流体力学与热力学相结合的分析方法,提出了重介质在径向的沉积和扩散运动是旋流器内梯度密度分布的主要成因的观点,得出了重介旋流器内密度场分布满足异重流模型:在旋流器的内层为强迫涡区,径向密度与回转半径线性相关等密度面为均匀的圆台面;螺旋流的外层,存在轴向逐渐增厚的自由涡流动区域,该区域各点的密度与回转半径成指数函数关系(ρ=ρl +a?Rk),混合流体在轴向沿等密度线运动。被选物料进入旋流器后,迅速到达其等密度层附近并随之运动,得到分选。利用计算流体力学(CFD)软件(Fluent)对旋流器内密度场和速度场的分布进行了数值模拟,结果表明,悬浮液流场速度分布与密度分布形态一致,这进一步验证了异重流模型。介质入口流道形式和重产物口反压力大小等都对流场的分布有着显著的影响,通过对相关参数的优化,提高了旋流器的分选精度和抗磨性能。开发出Φ500/400、Φ800/650两种型号精选型圆筒重介旋流器,可能偏差E值≤0.015。通过流体受力分析,提出了悬浮液压力波形成与共振吸收模型:重介旋流器入口压力的变化可以分解为:来源于介质桶液位变化的低频压力波和来源于流体振荡的高频压力波。当高频压力波自振频率与空气弹簧自振频率相等时即可实现谐振吸收。提出了以降低工作介质整体粒度组成为特征的介质制备新方法,构建了基于工艺自衡的高精度重介分选密度自动控制系统,介质密度波动范围可控制在±0.002 kg/L;旋流器入口压力波动范围小于±0.001 MPa;介质消耗0.60 kg/t以下。论文的研究结果已应用于太西洗煤厂实际生产中,已生产出灰分Ad<2.00%超纯煤产品,取得了良好的技术经济效果。更多还原

【Abstract】 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.更多还原