液固流化床内颗粒自由沉降末速的试验研究

对液固流化床内粗煤泥的自由沉降速度进行了研究,建立了液固流化床试验系统,通过对流化床内雷诺数和自由沉降末速等参数的测试计算,得出如下结论:在物理模型中,阿连公式是粗煤泥颗粒沉降末速的合适公式,而在经验模型中,斯万森公式与实测值最接近;粒度和密度是影响颗粒沉降最主要的两个因素,随着粒度和密度的增大,自由沉降的不规律性越强,物理模型及经验模型所得出的自由沉降计算值与实测值的差距也增大。     

干扰床分选机工作原理及分选理论基础研究

文章介绍了干扰床分选机的工作原理,并在比较了各种粗煤泥自由沉降速度计算方法的基础上,提出了适用于粗煤泥自由沉降速度计算的公式,同时计算了不同粒度、密度级别颗粒的干扰沉降速度,为干扰床分选机分选粗煤泥奠定了理论基础。     

TBS干扰床分选机内颗粒的受力分析及沉降规律研究

通过对颗粒在TBS干扰床分选机内的自由沉降末速和干扰沉降末速进行了理论分析及试验研究,得出密度较高、粒度较大的颗粒自由沉降末速与其他颗粒差值较大,易于通过速度差来实现分选,颗粒的密度对分选效果的影响大于粒度的影响,有益于按密度差异进行分选;密度相同时,颗粒的粒度在干扰沉降中对沉降末速的影响较大,粒度相同时,颗粒的密度对沉降末速的影响不大,这对颗粒在实际分选中按密度差异进行分选十分不利,也是改善粗煤泥分选效果的核心问题。     

新型粗煤泥干扰床分选技术的研究

粗煤泥干扰床由于可控参数少、要求入料粒度范围窄等缺点极大地限制了传统干扰床分选技术的应用,论文提出采用脉动水流以强化密度对干扰沉降的主导作用,同时在分选机内部添加阻尼块以改善上升水流流态.采用隔膜配合变频器构建了实验室分选系统,并采用九里山矿选煤厂较宽粒级的粗煤泥(3～0.25mm)同传统的干扰床分选机进行了对比试验.试验结果表明:增加阻尼块和脉动水流的新型干扰床分选机的分选效果优于传统的干扰床分选机.     

干扰床分选机颗粒自由沉降末速数学模型探索

为了解决颗粒自由沉降末速计算式不能直接应用的问题,基于颗粒的沉降速度计算式和试验数据,探索性的建立颗粒的自由沉降末速数学模型,并对其可靠性进行验证。研究表明:通过沉降试验和数学模型得到的颗粒自由沉降末速很接近,在允许的误差范围内;在其基础上推导出的颗粒干扰沉降速度数学模型,可以指导干扰床分选机相关参数的设计与选择。     

螺旋分选机动力学分析及参数优化探讨

为了探索螺旋分选机主要结构参数对颗粒运动规律的影响,基于螺旋线的形成特性,利用微元的思想将颗粒在螺旋槽上复杂的受力进行简化,推导出集物料性质、螺旋分选机结构参数为一体的数学模型;以1.0~0.5 mm粒度级的不同密度级粗煤泥为入料,探究了不同密度级颗粒在螺旋分选机出料端沿径向的分布情况,与数学模型分析出的结果进行对比验证,并分析了螺距、流量、螺旋槽内径和槽深等参数对颗粒达运动平衡后径向距离的影响;结果表明:提出的数学模型可以定性分析颗粒在螺旋分选机中的运动行为,颗粒密度越大,其平衡半径越靠近螺旋槽内缘;颗粒达平衡状态后的径向距离随螺距、流量以及内径的减小而减小,随槽深的减小而增加;较小的螺距、较小的内径和较大的槽深有利于粗煤泥的分选。     

介质密度对液固流化床粗煤泥分选效果的影响

针对工业上液固流化床粗煤泥分选机有效分选粒级窄,对难选煤分选效率低的缺点,开展了介质密度对液固流化床分选效果的影响研究,提出将液固流化床上升清水流改为重介质流。分别在2种上升流流量条件下对3~0.25 mm粗煤泥进行不同上升流流速的液固流化床粗煤泥分选试验。结果表明,液固流化床分选机采用重介质流分选时可将粗煤泥有效分选粒度范围拓宽至3~0.25mm,可能偏差控制在0.05~0.10 g/cm3,在较高上升流流速下精煤灰分可降至9.85%,当要求精煤灰分不大于11%时,精煤产率提高10.21%。     

脉动液固流化床分选机流场的计算流体力学模拟

介绍了一种新型的粗煤泥分选设备及其工作原理,并在试验研究的基础上,应用Fluent软件对脉动液固流化床分选机内部流场进行了三维数值模拟,结果表明:颗粒的运动行为与其密度、粘度、粒度大小等有关,在上升水流作用下,颗粒群进入分选区后迅速实现分层、分选,表明该分选机分选粗煤泥是可行的。但该机也存在溢流短路几率较大、分选机底部返混等问题,因此应当改进入料管和布水板的结构,以达到优化分选机的目的。     

干扰床分选机分选粗煤泥的规律研究

介绍了干扰床分选机的工作原理,在比较了各种粗煤泥自由沉降速度计算方法的基础上,提出了适用于粗煤泥自由沉降速度的计算公式。筹建了试验室干扰床分选机试验系统,并对新汶矿业集团汶南煤矿不同粒度级别的粗煤泥进行了干扰床分选试验,探讨了干扰床分选机分选粗煤泥的一般规律。     

脉动液固流化床粗煤泥分选试验研究

为探索脉动液固流化床分选粗煤泥的分选效果,寻求最佳的脉动水流波形,设计了恒定水流和不同振幅频率的脉动水流条件试验,分析了引入脉动前后的液固流化床的分选效果和产品特性,结合颗粒动力学方程对脉动水流分选机理进行了分析。结果表明:小振幅高频率的脉动水流可以获得灰分含量为15.55%,产率为77.47%的最佳分选指标;与相同上升水量的恒定水流TBS分选机相比,精煤产率可提高2.09%,灰分下降0.09%;脉动水流使不同密度物料产生不同程度的加减速效应,按密度分层作用随之强化;针对TBS入料粒度小、范围窄的特点,分选机只需要小振幅的水流,过高的振幅会严重破坏床层的稳定性,恶化分选效果。     

基于颗粒简化动力学方程的液固分选流化床数学模型

利用四阶Runge-Kutta法求解了液固分选流化床内颗粒的简化动力学方程,得到了颗粒速度和位移等随时间变化关系,并搭建了流化试验系统,验证了颗粒简化动力学方程的准确性,其预测的颗粒干扰沉降末速相对偏差基本可控制在5%以内。建立了基于该简化动力学方程的液固分选流化床数学模型,与试验分选结果相比,各密度级颗粒分配率的均方根误差为5.05。利用该模型探究了入料速率对颗粒分离结果的影响,发现入料速率增大导致的床层有效密度与实际分选密度比值减小是该过程中液固流化床分选效率降低的原因。     

基于准流体法的颗粒干扰沉降末速模型

试验研究了颗粒体积分数对液固流化床颗粒干扰沉降末速的影响，以准流体有效密度和表观黏度概念刻画床层内颗粒间相互作用，提出了新的干扰沉降末速模型，相对误差基本控制在10%以内，预测准确度比现有干扰沉降末速模型明显提高。利用提出的干扰沉降末速模型探究了等沉比随液固流化床层颗粒体积分数变化关系，发现等沉比随床层颗粒体积分数增大而增大，表明入料粒度范围变宽、粒度效应对重选的影响受到一定程度抑制。     

Numerical study of centrifugal fluidized bed separation

This paper examines the modelling of hindered settling separation in a centrifugal fluidized bed. A mathematical model based upon the macroscopic continuum conservation law and dynamic discrete particle velocity equation has been developed to simulate polydisperse particle separation in a centrifugal hindered-setting bed. An explicit finite difference method was used to discretise the partial difference equation and combined hindered settling velocity to solve the equation. A c++ program was developed to carry out iterative computations with special shock front interface treatment for initialization and boundary conditions.The simulated values from this dynamic model showed good agreement with the results of a centrifugal fluidized bed separator at different fluidization water flow rates and centrifugal forces.     

PCC桩Q-S曲线Bolztmann模型拟合及承载力计算

基于3个场地共13根桩的现场试验资料,对现浇混凝土薄壁筒桩进行了桩顶荷载-桩顶沉降曲线的数学拟合和承载力计算.结果表明,和抛物线模型、指数模型相比,本文建议的玻耳兹曼模型是描述薄壁筒桩桩顶荷载-桩顶沉降曲线的较好模型,它对直线型、缓变型、陡变型曲线都能进行较好的拟合;用玻耳兹曼模型拟合13根薄壁筒桩的桩顶荷载-桩顶沉降曲线的效果很好,相关系数都达到0.980 6以上,平均0.992 6;对桩顶沉降已超过30 mm的8根桩,Q₃₀ 计算值与实测值误差百分比的绝对值在0.110 0%~8.440 0%,平均值为2.897 5%, 对桩顶沉降未达到30 mm的5根桩,利用拟合方程式可对桩顶荷载Q₃₀进行预测.     

Mechanism of hydrocyclone separation with water injection

In hydrocyclones, the particle separation efficiency is limited by the suspended fine particles, which are discharged with the coarse product in the underflow. It is well known that injecting water in the conical part of the cyclone reduces the fine particle fraction in the underflow.This paper presents a mathematical model that simulates the water injection in the conical component. The model accounts for the fluid flow and the particle motion. The stationary concentration distributions result from superpositioning the turbulent particle diffusion and particle settling. Particle interaction, due to hindered settling caused by increased density and viscosity of the suspension, and fine particle entrainment by settling coarse particles are included in the model. Water injection in the conical part of the hydrocyclone is performed to reduce fine particle discharge in the underflow. This added water transports the fine particles of the sediment to the center, where they are directed to the overflow. The model demonstrates the impact of the injection rate, injection velocity, and injection location on the shape of the partition curve. Under optimal conditions, the so-called “fish hook” of the curve is reduced without changing the cut size. The simulations are compared with experimental data of a 50-mm cyclone.     

石墨尾矿沉降特性研究

研究了石墨尾矿浆在不同条件下的沉降特性,研究表明:石墨尾矿的沉降与颗粒细度、矿浆的浓度和外加剂有关:颗粒越细,沉降速度越慢;浓度越低,沉降速度越快,但颗粒的偏析和分级越明显。在矿浆中掺加促沉剂CBC-S时,在低掺量条件下具有加速微细颗粒沉降和改善水质的作用,在高掺量时有促使尾矿固化作用。     

砂矿颗粒沉降运动规律试验研究

在滨海砂矿开采中, 为给管道输送工业设计提供必要的试验数据和优化输送参数, 从沉降机理出发对不同颗粒级配的砂矿进行了单颗粒及群体颗粒沉降试验研究, 分析了粒径及浓度对颗粒沉降规律的影响, 得出了沉降速度计算公式。结果表明, 浓度和颗粒直径是影响群体沉降速度的主要因素; 所得沉降速度计算公式的计算值与实测值误差较小, 可为砂矿管道输送参数计算提供参考。     

Enhanced separation of mineral sands using the Reflux Classifier

The Reflux Classifier consists of a conventional fluidized bed, with a set of parallel inclined plates immediately above. The fluidized suspension passes into the inclined channels where relatively fast settling particles segregate, slide down the plates and return to the fluidized bed. The slower settling particles pass up through the inclined channels and into the overflow. By increasing the aspect ratio of the inclined channels, the effective sedimentation area of the vessel increases, in turn increasing the hydraulic capacity of the device. Laskovski et al. [Laskovski, D., Duncan, P., Stevenson, P., Zhou, J., Galvin, K.P., 2006. Segregation of hydraulically suspended particles in inclined channels. Chem. Eng. Sci., doi:10.1016/j.ces.2006.08.024], however, have shown that there exists an asymptotic limit to this hydraulic capacity, due to an increased tendency for particle re-suspension within the inclined channels as the aspect ratio increases. Laskovski et al. (2006) showed that the re-suspension facilitates the separation of the particles on the basis of density, reducing the dependence on the particle size. A conventional fluidized bed does not offer the benefits of the mechanism identified by Laskovski et al. (2006). In this study, the Reflux Classifier was used to recover and concentrate the heavy minerals presented in a low grade feed of mineral sands. Enhanced separation was achieved using inclined channels having a large aspect ratio of about 200, thus promoting the particle segregation of the denser particles while also promoting the re-suspension and hence hydraulic conveying of the lower density silica sand. With the aspect ratio of approximately 200, recoveries of heavy minerals in excess of 90% were achieved at solids throughputs of up to 40 t/m² h. A heavy mineral recovery of 97% was achieved at a solids throughput of 21 t/m² h. The separations resulted in heavy mineral grades approaching 100% in the size range of 90–180 μm.     

宽粒级煤炭颗粒在三相流化床中的分选实验研究

拓宽浮选粒度上限是浮选领域挑战的难题之一。应用三相流化床技术,在上升水流中引入气泡流,对比有无气泡对煤炭颗粒床层膨胀度的影响,得出气泡流的引入能够加强低密度颗粒的流化。并在单独上升水流、上升水流+气泡流和上升水流+气泡流+捕收剂(煤油)3种水流条件下,进行煤炭分选实验。结果表明,气泡流的引入,能够大幅减少低密度级颗粒悬浮所需的上升水流速度,气泡流对低密度级颗粒的影响强于高密度级,气泡的存在强化了颗粒密度、弱化了粒度对分选的影响;在上升气泡流中添加捕收剂后,低密度级颗粒与气泡形成颗粒-气泡结合体,低密度级颗粒便能够在较低的上升水流速度下进行分选,低速上升水流稳流度较低,保证了大颗粒与气泡的稳定性。添加捕收剂后,各粒级颗粒分选所需上升水流速度较为接近,各粒级精煤灰分在10%左右。