【作者】 刘瑜；

【导师】 杜长龙；

【作者基本信息】 中国矿业大学 ， 机械设计及理论， 2011， 博士

【摘要】 矸石作为煤炭开采的伴生物,在地面堆积后形成矸石山,对矿区环境带来很多不利影响。要从根源上解决矸石排放和堆积造成的环境问题,就需要在井下实现煤和矸石分离,并将矸石就地进行填充。井下冲撞式煤矸分离技术是基于煤和矸石的物理机械特性差异提出的适用于井下的煤和矸石分离方法,它具有安全性高、处理量大、占用空间小、使用成本低等优点,不但可以减少矸石地面堆积造成的环境污染,还可以降低煤矿的运输成本,减轻过度开采导致的沉陷灾害,对实现煤矿绿色开采具有重要意义。为此,本论文采用理论分析、数值模拟和试验研究相结合的方式,对井下冲撞式煤矸分离的关键问题——颗粒动力学行为进行研究,为该技术的推广和应用奠定了理论基础。本论文基于Hertz理论和双线性强化弹塑性模型,以Drucker-Prager屈服准则为依据,建立了准脆性球形颗粒与反弹板碰撞接触的初始屈服模型和碰撞接触模型,得到了颗粒初始屈服响应、碰撞接触响应和反弹距离的主要影响因素,并研究了各因素对准脆性颗粒碰撞接触响应的影响规律。对煤和矸石颗粒与反弹板的碰撞反弹行为进行有限元模拟,得出了反弹速度和反弹距离差异随各影响因素的变化规律。以新汶矿业集团协庄矿工作面的煤和矸石为研究对象,通过单颗粒碰撞反弹试验对煤和矸石颗粒的反弹距离进行了研究。试验结果表明:当初始速度较小时,理论计算的反弹距离与试验结果较吻合;初始速度较大时,部分颗粒发生破碎,理论计算的反弹距离大于试验测量的反弹距离;协庄矿的煤和矸石颗粒在初始速度大于7.5 m/s时可以按照反弹距离差异分离出部分矸石。基于分形理论、最弱环模型和碰撞动力学理论,建立了颗粒冲击过程的断裂破碎概率模型和破碎粒度分布模型,得到断裂破碎概率与冲击速度的内在联系,确定了破碎粒度分选的粒度界线,并给出基于破碎粒度分选的矸石分离质量比计算公式。对三个矿区工作面的煤和矸石进行冲击破碎试验,结果表明,煤和矸石颗粒冲击破碎时的断裂破碎概率和破碎粒度都具有分形特征,同一矿区矸石颗粒断裂破碎概率和破碎粒度的分形维数都小于煤颗粒对应的分形维数,可以通过破碎粒度差异实现煤和矸石的初步分离。利用三维离散单元法对粒度为50～100 mm的颗粒群连续抛射和反弹行为进行了模拟分析,结果表明提高颗粒群反弹距离的主要途径是提高入料中间颗粒与反弹板的接触概率和减少入料中间颗粒的碰撞干扰。提出了平均触板概率(MCPP)、无干扰触板概率(NTCPP)、二次碰撞概率和二次碰撞频率四个指标,分别用以描述颗粒群的触板情况和颗粒群的二次碰撞行为,并分析了各指标随颗粒入料量、颗粒断裂破碎概率和颗粒抛射速度等因素的变化规律。对特定入料量和颗粒抛射速度下的颗粒群连续抛射过程进行模拟研究,确定了反弹板的尺寸和反弹距离分选界线,并提出了用反弹距离和破碎粒度相结合实现井下煤矸分离的技术方案,为井下冲撞式煤矸分离的工业应用奠定了基础。提出了矸石分离质量比、丢煤质量比和末煤质量比三个指标,用以评价井下冲撞式煤矸分离的效果,以经济效益为基础建立了分离效果综合评定指标的计算公式。使用三维离散元模拟和BP神经网络模型相结合的方法对分离效果进行了预测,为井下冲撞式煤矸分离的定性和定量评价提供依据。更多还原

【Abstract】 Gangue, the accompanying mineral of coal mining, is always transported to the ground and accumulated as hillock. The gangue hillock causes many adverse effects on the surrounding environment. Achieving separation for coal and gangue underground and backfilling gangue in situ is the method that can radically solve the environmental problems produced by discharge and accumulation of gangue. With regard to this, impact separation technique for coal and gangue underground is presented depending on the differences of physical and mechanical properties for coal and gangue. With the advantages of high security, great treating capacity, small volume and low cost, this technique can reduce the environmental pollutions and bring down the transportation cost of coal mine as well as solve the subsidence caused by over-extraction partially. Therefore, the impact separation for coal and gangue underground has the significance for realizing the green mining. To provide theoretical basis for popularization and application of the technique, the theoretical analysis, numerical simulation and experiments are combined to investigate the particle dynamics behavior during the impact separation process in this dissertation.According to the Drucker-Prager yield criterion and based on the Hertz theory and the bilinear hardening elastio-plastic model, the initial yield model and impact contact model for impact between quasi-brittle spherical particle and rebound plate are built. The main influence factors and the influence law for initial yield response, impact contact response and the rebound distance are developed. Simultaneously, the impact rebound behaviors of coal and gangue particles are simulated by using finite element method and the variance rules of the differences for rebound velocities and rebound distances are developed.Taking coal and gangue particles from working face in Xiezhuang mining of Xinwen Mining Group as study objects, rebound distance experiments are carried out. The results indicate that the theoretical distance quite agree with the experimental result when the initial velocity is low, but is larger than the experimental result when the initial velocity is high because of the particle crushing. For coal and gangue in Xiezhuang mining, partial gangue can be separated by the difference of rebound distance when the initial velocity is higher than 7.5 m/s.Based on fractal theory, weakest link model and impact dynamics theory, the fracture crushing probability model and the crushing granularity distribution model are built as well as the inherence relation between the fracture crushing probability and the impact velocity is developed. The granularity boundary of separation by crushing granularity is determined, while the calculation formula for the mass ratio of separated gangue is put forward. The impact crushing expriments are completed for coal and gangue from three working faces. The results show that the fracture crushing probability and the crushing granularity of coal and gangue particles in impact crushing process both have fractal feature. Furthermore, the analysis indicates that the fractal dimensions of the fracture crushing probability and the crushing granularity for gangue particles are both smaller than ones of coal particles from the same working face, which demonstrates that the primary separation for coal and gangue can be achieved using separation by the crushing granularity.The simulation analysis on continuously projecting and rebound behaviors of particle group with granularity between 50 mm and 100 mm are carried out using three-dimension discrete element method. The study shows that main approaches to increase the rebound distances of particle group are to raise the contact probability between feeding middle particles and rebound plate and to decrease the impact interference among feeding middle particles. Four indexes are proposed to describe status of contacts between particle and rebound plate and secondary impact behaviors of particle group, including mean contact plate probability, non-trouble contact plate probability, secondary impact probability and secondary impact frequency. The indexes variance rules with particle feeding amount, fracture crushing probability and projecting velocity are thoroughly discussed.For certain particle feeding amount and projecting velocity, the continuously projecting and rebound behaviors of particle group are simulated to determine the dimensions of the rebound plate and the boundary of separation by the rebound distance. The technical scheme of combining the rebound distance and the crushing granularity to realize separation for coal and gangue underground is put forward, which lays a foundation for the industry application of this technique.Three indexes including the mass ratio of separated gangue, the mass ratio of waste coal and the mass ratio of slack coal are proposed to evaluate the effect of impact separation for coal and gangue. Based on economic benefits, the calculation formula of comprehensive evaluation index for separation effect is obtained. Combining with three- dimension discrete element method and BP neural network model, the effect of impact separation for coal and gangue is predicted. All above provide foundation for qualitative and quantitative evaluation of impact separation for coal and gangue underground.更多还原