【作者】 沙杰；

【导师】 谢广元；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2013， 博士

【摘要】 液固流化床分选机作为目前对粗煤泥分选最有效的方法之一，被广泛应用于国内外选煤厂。对于固体颗粒在液固流化床中的分选行为和运动特性的研究对液固流化床分选技术的进一步发展和创新具有十分重要的理论意义。本论文建立了改进后的新型液固流化床分选系统，研究了液固流化床分选理论，对颗粒流态化特性以及粗煤泥分选特性进行了试验研究和数值模拟，并利用高速动态分析系统研究了固体颗粒在分选过程中的运动特性，得出了以下结论：不同密度、不同粒度的颗粒具有不同的初始流态化速度，数值上与颗粒的沉降速度相等，并随着颗粒密度和粒度的增加而增加；颗粒在不同上升水速时具有不同的床层膨胀特性，初始流态化速度越低，其床层膨胀程度越高。当较窄粒度级的不同密度颗粒混合流态化时，主要体现为按密度分层，当混合颗粒的粒度级逐渐变宽时，按密度分层越来越不明显，甚至会出现按粒度分层；根据试验研究进行总结，提出当分选流化床颗粒入料下限为0.25mm时，应当避免>1mm的颗粒进入分选机，以能保证良好的分选精度。在液固流化床分选粗煤泥的过程中，分析了不同高度处的瞬时液相速度，并推导得出其与表观水速和颗粒松散程度的关系式：Vdh=Qu/dhθS·=VS/θdh=VS/1-λdh并指出在分选机下部的瞬时水流速度高于分选机上部。通过试验研究得出颗粒相的浓度在整体上呈现下高上低的分布，在给料口附近的颗粒浓度稍高于附近区域，柱体高度越高，高密度颗粒的含量越来越少，而低密度颗粒的含量逐渐增加，使得由颗粒和流体共同组成的混合床层的密度在整体上随着高度的升高而降低，呈现床层密度的梯度变化，仅在给料口处的床层密度稍高于附近区域，随后会继续降低。在分选过程中，粗煤泥的灰分也在床层高度上呈现下高上低的梯级分布规律。推导出床层密度与颗粒松散程度和颗粒组分性质的函数表达式：ρdh(v,h)=λdh(v,h)(Σi(v,h)δi(v,h)-1)+1通过示踪颗粒测速方法，对颗粒在分选过程中的运动进行了研究，得出颗粒在液固流化床中分选时的运动特性因颗粒密度的不同而不同，总体趋势上低密度颗粒向上运动、高密度颗粒向下运动，中等密度颗粒向床层中部运动。通过研究指出单个颗粒运动的瞬时速度是不断改变的，会在某一范围内波动，速度的波动符合正态分布规律，变化均值与同类颗粒群在相同区域内运动的平均速度接近。对临沂矿物局古城选煤厂的粗煤泥进行了分选，并对结果进行了整体优化，最优的操作参数组合下可以得到产品的精煤产率为71.52%，精煤灰分为6.87%，可燃体回收率为82.26%，数量效率为91.77%。通过试验结果与目前现场实际生产相结合，创新性地提出了“液固流化床分选机+旋流微泡浮选柱”配套组合进行重介中煤再选的新工艺，为选煤厂提高精煤回收率提出了新的构思。更多还原

【Abstract】 Liquid-solid fluidized bed separator, as one of the most effective coarse coal slimeseparation, has been widely used in many coal preparation plants at home and abroad. It is ofgreat theoretical significance for further development and innovation of the liquid-solid fluidizedbed separation technology to study separation behavior and movement characteristics of solidparticles in liquid-solid fluidized bed. In this thesis, based on setting up the improved liquid-solidfluidized bed separation system and studying the liquid-solid fluidized bed separation theory,experimental study and numerical simulation is carried out for particulate fluidizationcharacteristics and coarse coal slime separation characteristics and high speed dynamic analysissystem is used to study kinetic characteristic of solid particle in the process of sorting. Theconclusions are drawn as following.The particles of different density and size have different initial fluidization velocity which isequal to settling velocity on numerical. The initial fluidization velocity increase with the increaseof the density and particle size. Different bed expansion characteristics come out when the risingwater velocity is different. The lower the initial fluidization velocity, the higher bed expansiondegree. When different density particles are fluidized, the particles layer by the density innarrow grain size, but blend or layer by the size in more and more wide grain size. It is proposedby tests that when the lower limit of0.25mm in fluidized bed separation, particles of>1mmshould be avoided into the separator to ensure the sorting accuracy.The velocity of transient liquid phase at different heights is analyzed in the process ofliquid-solid fluidized bed of coarse coal slime separation. And the relationship of the velocity oftransient liquid phase and apparent water velocity and particle loose is derived as follows:Vdh=Qu/dhθS·=VS/θdh=VS/1-λdhThe paper indicate that Instantaneous flow rate at the bottom of the cylinder is higher thanthat at the upper of the cylinder. The study concludes that the concentration of the particle phasedistribution at the bottom is in high concentration and the upper is in low concentration on thewhole, and particle concentration at material inlet is higher than that at the near area. The contentof high density particles is lower and lower as column height increase, while the content of lowdensity particles is gradually higher. Eventually it leads to the reducing bed density constitutedby particles and fluid with the increase of height. The density presents gradient variation and itincrease slightly at material inlet and will continue to reduce latterly. In the process of separating, the ash of coarse slime presents cascade distribution of high bottom and low upper in bed height.The paper elicits the function expression regarding with bed density, particles loose degree andParticle composition properties.ρdh(v,h)=λdh(v,h)(Σi(v,h)δi(v,h)-1)+1When particle density is different, the kinetic characteristics of particle in the liquid-solidfluidized bed is different. On the whole, low density particles move up while high densityparticles down, and middle density particles stay in the middle of the bed. The study concludesthat instantaneous velocity of single particle is constantly changing and fluctuates in a certainrange. The fluctuating of velocity conform to the law of normal distribution. The averagefluctuating is close to the average velocity of similar particle group in the same area.The result of separating of coarse slime of Gu Cheng coal preparation plant in Lin YiMineral bureau has been integrative optimized. Clean coal yield of product is71.52%, clean coalash is6.87%, combustible material recovery is82.26%and recovery efficiency is91.77%at theoptimum operating parameters combination. The thesis proposes an innovative technique on thecombination of liquid solid fluidized bed separator and micro-bubble flotation column is used tore-separate middlings resulting in a new idea in improving clean coal yield in coal preparationplant.更多还原