振动重介质流化床细粒焦渣混合物的分选

在间歇振动流化床中研究了细粒焦渣混合物的分离．通过考察细粒焦、细粒渣及细粒焦渣混合物的入选体积量对床层密度和分选效率的影响，得出适宜的操作条件．在此条件下对细粒焦渣混合物进行了分选实验，得到了较佳的分离效率。     

内置倾斜板变径流化床粗煤泥连续分选试验研究

为强化粗煤泥的分选效果,设计了一套内置倾斜板变径流化床粗煤泥连续分选系统,考察了主要操作参数对分选效果的影响规律。研究结果表明:精煤相关指标与床层密度和上升水速均呈正相关关系;E_p值在不同上升水速条件下的变化趋势存在差异,适宜分选密度范围内,较低水速匹配较高床层密度分选效果良好;变径和倾斜板结构强化了颗粒按密度分离,相比传统分选机,内置倾斜板变径液固流化床分选精度可提高0.02～0.03 g/cm~3。自生介质床层强化了颗粒按密度分离,连续条件下液固流化床分选精度显著提高,相比间断分选条件,E_p值可降低0.07～0.10 g/cm~3。     

干法重介质流化床煤炭颗粒受力特性与分选研究

近年来,干法重介质流化床分选技术的快速发展为世界干旱缺水地区的煤炭洁净分选提质提供了一条有效途径。在干法重介质流化床中,上升气流驱动加重质颗粒流化形成具有似流体性质的气固两相流床层,营造了适合煤炭分选的均匀稳定的流态化环境。入选煤炭颗粒在床层中迁移、浮沉,受到自身重力、气流曳力、介质阻力、床层浮力等综合作用按密度进行分选。煤颗粒物性特征、床层密度分布、流化床操作参数等是影响煤颗粒受力特征、沉降特性及分选效果的关键因素。重点研究了加重质颗粒在流化过程中的迁移过程和床层密度空间分布规律,定量评估了床层密度的均匀稳定性;研究了颗粒粒度、密度、浸没深度与流化气速对入选煤炭颗粒受力特性的影响规律,采用响应面分析方法对比了不同影响因素的扰动规律与影响程度,建立了表征各影响因素与煤炭颗粒综合受力关系的关联式;确定了入选煤颗粒各密度组分的迁移路径与稳定分布区域。研究结果表明,以磁铁矿粉(0.300～0.074 mm, 2.36 g/cm~3)与玻璃微粉(0.300～0.074 mm, 1.14 g/cm~3)组成二元加重质作为流化介质颗粒,可形成密度均匀的气固流化床层,二元加重质颗粒混合均匀稳定,床层密度波动控制在±0.01 g/cm~3以内;各主要影响因素对入选颗粒受力影响显著性程度依次为粒径、浸没深度、流化气速;入选煤颗粒给入床层后,各密度组分快速松散、沉降、分层,分选时间≤8 s,高于床层密度的煤颗粒快速下沉,沉降于床高40 mm以下区域;低于床层密度的煤颗粒沿床层表面附近区域松散、横向迁移,分布在床高160 mm以上区域;中间密度颗粒松散、沉降并行,整体分布于45 mm床高以上的床层区域。     

振动流化床内双组分颗粒的混合与分离特性

在300 mm′300 mm′20 mm的二维振动流化床中,装入平均粒径2和4 mm的分子筛颗粒,在低于流化速度(u相似文献   

用落球法研究气固浓相流化床表观粘度

用落球法对不同参数条件下的气固浓相流化床床层表观粘度进行测量和线性拟合,得到了流化床的床层屈服应力和塑性粘度与各因素的关系;研究了粘度对分选时间的影响,建立了振动流化床分选时间与表观粘度和物料密度之间的数学模型. 结果表明,在同一气速下,随石英砂颗粒粒级及床层高度增大,床层表观粘度整体增大. 在一定的流化气速范围内,石英砂介质粒级为0.25~0.125 mm、床高190 mm时,床层粘度稳定在0.39~0.51 Pa×s. 加入振动后,床层粘度明显下降,频率15 Hz、振幅1 mm时流化效果较好,床层粘度稳定在0.69~0.95 Pa×s.     

多孔板干扰床中细粒煤分离特性研究

为提高干扰床对细粒煤的分选效果,将一种多孔板应用于干扰床,采用实验与数值模拟相结合的方法,研究了多孔板对细粒煤分选密度、颗粒分布的影响及多孔板干扰床的流化特性。结果表明:多孔板使各粒级分选密度更加均匀,粒度-分选密度曲线斜率由-0.518增至-0.448,强化了颗粒的密度分离,提高了分选效果。高密度颗粒(1.70、1.90 g/cm3)主要集中在床层底部,低密度颗粒(1.40、1.50 g/cm3)主要集中在床层上部,其体积分数分别为29.79%、32.86%、48.90%、20.81%,错配颗粒比较少,实现了煤粒的有效分选。干扰床床层悬浮区密度不是煤粒分选密度,其平均值为1.23 g/cm3,且在高度方向上并不均匀。多孔板干扰床中形成了多孔板分级—板间流化区—多孔板与边壁间流化区的多级分选模式,能在一定程度上抑制高低密度颗粒错配,实现细粒煤的高效分选。     

混合颗粒在内置水平管振动流化床中流体力学研究

在内置水平管的二维振动流化床中研究了玉米粒与塑料珠颗粒混合物的流化特性,考察了颗粒质量分数、振动频率、振幅、内置水平管和振动强度对床层压降及临界流化压降的影响。实验结果表明,在混合颗粒的振动流化床中,固定床阶段,相同条件下床层压降随着玉米粒质量分数的增大而增大,流化床阶段随玉米粒质量分数增大而减小;内置管的引入增大了床层压降;振动的引入增大了固体床阶段的床层压降,降低了流化床阶段的临界流化压降;振动对大粒径的影响小于小粒径;由实验数据拟合出的用于预测带内置水平管的混合颗粒振动流化床临界流化压降的经验公式,经验公式与实验数据基本吻合。     

生物质惰性颗粒混合物的混合分离特性

在D99mm×1000mm的圆柱流化床中,选用不同粒径的沙子／锯末、沙子／菜籽双组分混合物,研究了不同沉积组分含量,尤其是富沉积组分情形下床层表观气速、静床高度对流化床二组分混合物的混合与分离的影响．实验结果表明：静床高度对生物质惰性颗粒混合物分离指数无影响,沉积组分适宜的粒度及床层高和表观气速有利于生物质惰性颗粒混合物的混合．     

不同参数对振动流化床分选细粒褐煤的影响

阐述了振动流化床的结构及作用机理。对6～3,3～1 mm褐煤分别进行了浮沉实验,说明当分选密度为1.7 kg/L时,褐煤属中等可选煤。在振动强度大于1的情况下,利用振动流化床模型机对6～3 mm和3～1 mm褐煤分别进行分选实验,研究流化气速、振动强度、床层高度、煤炭水分等对褐煤分选效果的影响。结果表明:当流化数N为0.3,振动强度为1.5时,褐煤分选效果最好。从上至下将床层按体积分数7∶3的比例分为精煤和矸石时,可能偏差E值分别为0.202(6～3 mm)和0.225(3～1 mm)。随着外水含量的增加,褐煤分选效果逐渐变差,当外水含量分别小于4.5%(6～3 mm)和2.0%(3～1 mm)时对褐煤分选几乎没有影响。当床层高度低于70 mm时,床层高度对褐煤分选影响甚微,当床层高度高于70 mm时,褐煤分选效果急剧变差,床层高度的选择应考虑分选效果与处理量2个因素。     

带内置水平管的大颗粒振动流化床流体力学研究

以大颗粒MAP（磷酸-铵）为试验物料对带内置水平管的大颗粒振动流化床流体力学进行了试验研究,结果表明,振动的引入对床层临界压降有明显的降低作用;同样床层条件下振动频率越大床层临界压降越低,振幅的改变对床层压降影响不大;低气速下振动使床层孔隙率降低而导致压降高于普通流化床;在带内置水平管的大颗粒振动流化床中,振动对大粒径颗粒的影响小于小粒径颗粒;由试验拟合出经验公式,与试验数据吻合良好。     

Effect of Volume Fraction of Material on Separation by Density Difference in a Liquid‐Fluidized Bed of Inert Particles

A liquid‐fluidized bed was used to separate a pure material from a mixture. A quantity of relatively large sized material was immersed in an inert‐particle fluidized bed and the behavior of materials was examined for different liquid velocities. In particular, the volume fraction of the material was varied and its effect on the separation characteristics was examined. The material floats on the inert‐particle fluidized bed when the density of the material is lower than the apparent density of the bed, regardless of the volume fraction of the material. The apparent density of the bed can be adjusted by changing the liquid velocity. The materials in the upper portion of the bed affect the properties of the bed below them, i.e., the void fraction decreases and the apparent density increases in the inert‐particle suspension when materials are present in the upper portion of the bed. Therefore, the materials float on the bed although the apparent density of the inert‐particle suspension obtained from the case without material is less than the density of the material at a relatively high volume fraction of material. This phenomenon occurs more easily for lighter and smaller materials. This means that small inert particles and low liquid velocities are the optimum operating conditions for the separation.     

Pyrite enrichment in vibrated fluidized bed based on density segregation

It is of significance for the environmental protection, the shortage of water, and the economic benefits to recovering the pyrite from the gangue with high sulphur content (GHSC) by the vibrated fluidized bed. In this study, characteristics such as the sulphur form of pyrite, size distribution, and dissociation degree of sample were analysed. Based on the above analysis, a vibrated fluidized bed was first used for the pyrite enrichment from GHSC. The effect of air velocity, vibration intensity, and bed height on the separation performance was analysed by separation experiments. The results show that the separation efficiency increased firstly and then decreased with increasing gas velocity, vibration intensity, and bed height. The total sulphur contents (TSCs) of ?6 + 3, ?3 + 1, and ?1 + 0.5 mm size fraction materials were up to 37.94%, 35.43%, and 30.61%, respectively, and the enrichment grades were 1.72, 1.90, and 2.29 times, respectively, under the optimal conditions, indicating that using a vibrated fluidized bed was efficient for the pyrite enrichment.     

Effect of vibration energy on fluidization and 1–6 mm coal separation in a vibrated dense medium fluidized bed

In this study, a uniform and stable vibrated dense medium fluidized bed (VDMFB) with Geldart B magnetite powder was formed, where it was considered suitable for 1–6 mm coal separation. The formation mechanisms of the best separation environment including the fluidization phenomena under different vibration parameters, the transfer process of the vibration energy, the pressure drop fluctuation and particle oscillation velocity distribution at different bed heights, as well as the corresponding effect on the uniformity and stability of the bed density were investigated. Furthermore, the separation experiment was carried out, and the results exhibited an efficient dry separation performance in the VDMFB.     

Numerical simulation of particle motion in vibrated fluidized bed

The particle motion in vibrated fluidized bed was examined by using numerical simulation. A two-dimensional fluidized bed was used, and discrete element method (DEM) was used as for calculating the particle motion in vibrated fluidized bed. Geldart group B particle, which is regarded to have no effect of agglomerate, was used as the fluidizing particle. The vibration directions (vertical and horizontal) and vibration parameters (frequency and amplitude of vibration) were changed.In the case with vertical vibration, large bubbles caused by vibration gap (defined as the gap between particle bed and wall caused by vibration) appear in bed. When the vibration strength is high and the vibration frequency is low, it is difficult to fludize the particle bed in the case with horizontal vibration because the vibration gap acts like the channel. When the vibration frequency increases at the same vibration strength, the effect of vibration on the particle motion becomes small. The effect of vibration on the pressure loss in particle bed is large in the case with horizontal vibration.     

振动波在流化床中的传播行为

在试验基础上,阐述了振动床及振动流化床中振动能的输入方式.对于振动床,振动能输入方式是振动床体对粉体床层的碰撞.对于振动流化床,振动能输入方式是振动波在流化床悬浮体中的连续传播,床层特性影响波的传播特性.通过压力波动的频谱分析,可以考察床层中的气泡行为.     

Density-dependent separation of dry fine coal in a vibrated fluidized bed

The main purpose of coal separation is to reduce ash, sulfur, mercury and other mineral contaminants in the coal to increase the calorific value and benefit the environment. Dry coal beneficiation has obvious advantages over the wet process although the latter is currently the predominant method in use throughout the world. A vibrated fluidized bed was constructed for separating dry fine coal particles from unwanted gangue particles. An experimental investigation of vibrational energy transmission, and the interaction between vibration and gas flow, was performed. The motivation for these experiments was a theoretical development of the principles involved in forming a dense-media vibrated fluidized bed (DMVFB). The mechanism of bubble breaking by vibration is discussed. A formula for calculating the critical vibration frequency at which bubbles can be efficiently broken and bubble formation restrained is proposed. The experimental results demonstrate that the density of a dense-media vibrated fluidized bed is uniform, with a maximum relative error of 1.68% under optimal technological and operating conditions. The < 6 mm fine coal was efficiently separated with a probable error E value of 0.07 t/m³. A lower limit of separation of 0.5 mm was achieved. The DMVFB separation efficiency is higher than wet jig with E value of 0.11 t/m³.     

单组分颗粒振动流化床的流体力学研究（2）──床层膨胀和起始流化速度

本文在振动流化床中研究床层膨胀和颗粒的起始流化速度,分别研究颗粒物性、振动特性（频率、振幅）和静止床层高度对它们的影响,根据不同的振动条件下Ｇｅｌｄａｒｔ’Ａ、Ｂ、Ｄ类１３种物料起始流化速度的实验结果,关联了实验条件下起始流化速度的计算式,此计算式对振动流化床的设计具有指导意义。     

Prediction of the Behavior of a Liquid‐Fluidized Bed of Inert Particles Used for Separation by Density

A liquid‐fluidized bed of inert particles was used to separate a pure object from a mixture. One (binary solid‐liquid‐fluidized bed) or two (tertiary solid‐liquid‐fluidized bed) types of objects with relatively large‐sized particles were immersed in an inert‐particle bed, and the bed behavior was observed for different liquid velocities. The void fraction and apparent density of the inert‐particle suspension were predicted by considering the effect of the change in object position for different liquid velocities. The prediction method, which considers the change in the minimum fluidization velocity, accurately expressed the changes in the void fraction and the apparent density of the bed with the position of the objects in the bed. Using this method, the liquid velocity required to separate a certain kind of object from a mixture can be predicted.     

振动流化床与浸没水平管平均传热特性理论分析与实验研究

在二维流化床(240mm×80mm)中,以平均粒径dp为1.83mm的玻璃珠为物料,研究了振动流化床与浸没水平管间传热规律;考察了流化数、振动频率、床高、水平管管径等因素对平均传热系数的影响。采用自制探头对浸没加热管束和振动流化床层间平均传热系数进行实验测定,利用颗粒团模型,建立了振动流化床层与浸没水平管间平均传热模型,并对平均传热系数的理论预测值与实验测定值进行了比较。结果表明:计算值与实验值吻合较好,误差在±15%范围内。在较高流化数、低振动频率时,实验值处于理论值上方;随着振动频率、管径增大,平均传热系数实验值逐渐趋于理论预测值甚至低于理论预测值。结果可为带浸没水平管的振动流化床设计和研究提供参考。