磁力旋流器分离性能的试验研究

为了解决陶瓷、化工生产领域内浆液脱铁的工程问题,开发了一种可以自动排料的磁力旋流器,并通过试验研究和理论分析的方法,对比研究了入口流量、底流分率对磁力旋流器分离效率的影响。结果表明:磁力旋流器可以通过磁系吸附浆液中的铁化合物颗粒。对比试验结果,可以得出结论:磁力旋流器内铁化合物颗粒的径向沉降速度随进口流量的增大而减小。磁力旋流器的分离效率随进口流量的增大而减小,其分离效率与进口流量的关系与理论推论相符。对于单固相铁粉浆液,磁力旋流器的分离效率随底流分率的增大而减小;对于多固相铁粉浆液,磁力旋流器的分离效率随底流分率的增大先增大后减小,当底流分率为0.55时,分离效率最高。     

重介质微型旋流器内切向速度的数值模拟

重介质旋流器在选煤领域中已得到广泛应用。根据硅和碳化硅等不同密度微细颗粒易团聚且难用化学方法分离的特点,本文选用重介质微型旋流器对其进行分离。为探索重介质微型旋流器的流场特性,本文基于CFD软件Fluent对重介质微型旋流器的切向速度场进行了数值模拟研究,考察了介质的密度及黏度对旋流器内切向速度的影响。结果显示,密度不变,黏度增大,切向速度减小,且旋流器直径越小,切向速度减小越快,即旋流强度衰减得越快。虽然黏度不变时密度的增大会导致切向速度的增加,但当密度和黏度按实际重介质溶液同时增大时,黏度对切向速度的影响远大于密度的影响。     

旋流器的微米级颗粒分级性能分析

微型旋流器中的超重力场和剪切湍流场可以强化微米级颗粒的分级。为了分析旋流器的微米级颗粒分级性能,本文通过试验与数值模拟相结合的方法研究了入口速度和底流分率对旋流分级的影响。数值模拟方面使用雷诺应力模型模拟了微型旋流器内的流场,试验方面使用直径为20mm的微型旋流器来分级粒度分布为2~50μm的颗粒物料。结果表明,随着入口速度的增大,分割粒度x50减小,可达4.8μm,分级精度H提高,可达0.45;随着底流分率R_f的增大,不会显著改变切向和径向速度,颗粒在旋流器内的沉降速度变化不大,但轴向速度会减小,使得颗粒在旋流器内的停留时间增加,分级效率提高;当底流分率R_f0.6时,随着R_f的增大,分割粒度x_(50)减小,可达4.7μm,分级精度H提高,可达0.6;当底流分率R_f0.6时,分割粒度x50增大,分级精度H降低。     

压载水旋流器结构因素对分离性能影响分析

随着全球贸易和船舶运输的发展,压载水对环境的影响越来越大。水力旋流分离设备是压载水净化的重要固液分离设备。本文使用计算流体力学,建立数学模型模拟压载水旋流分离过程,模型包括多相湍流雷诺应力模型RSM、处理气液界面的自由表面多相流动模型VOF、处理固体颗粒运动规律的离散相模型DPM。通过数值模拟计算柱段长度、底流口直径和溢流口直径这几个关键因素对旋流器内部流场和分离效率的影响,获得了各个因素对分离效率的影响规律：柱段长度变化对旋流器分离效率的影响不大;底流口直径对旋流器压力降的影响不明显,但对分流比的作用比较大;溢流管直径的增大有助于降低能耗和增大溢流口流量,但随着溢流管直径的增大,分级粒度变大。这些规律为高效旋流分离净化压载水奠定了基础。     

石膏旋流器分离性能的试验研究

通过对影响水力旋流器分离性能的三个因素:底流管径、进料浓度和入口压力进行正交试验,得出影响旋流器分离效果的各因素主次顺序,并对各影响因素进行分析。通过分级实验得出,经分离后底流口颗粒粒径集中于20μm以上,溢流颗粒粒径则集中于20μm以下。随着颗粒粒径的增大,分离效率也在增大,当粒径达到30μm时,效率已经接近100%,旋流器起到明显的分级、增浓效果。     

矩形进料口旋流器长宽比对分离性能的影响

采用计算流体力学(CFD)方法对进料口长宽比为4:1、3:1、2:1、1.5:1、1:1的五种旋流器进行了模拟,研究进料口长宽比对旋流器内部的速度场、压降和颗粒运动轨迹的影响规律,并与实验结果进行了对比验证。结果表明:在相同的进口当量直径和进料速度条件下,增大进料口长宽比,流体的切向速度与径向速度明显增加,有利于提高分离精度,但当长宽比大于3时这一增加趋势变缓;随进料口长宽比的增大,压力降呈递增趋势,分离粒度变小;不同粒径颗粒的运动轨迹分布表明,增大进料口长宽比,可以有效减少底流夹细和溢流跑粗现象。从上述角度来看,当进料口长宽为3时,狭长型进料口更有利于分级。     

多进口旋流器流场特征及分离性能

为了改善单进口旋流器稳定性差、分级效率低等问题,本文提出了多进口旋流器结构。通过数值模拟方法,在恒定入料工况下,对比分析了单、二、三、四进口旋流器的流场特征和分离性能。研究结果表明：增加旋流器进口数量,会对旋流器流场和分离性能产生积极影响,有利于旋流流场径向压力的增大,且进口数量为偶数时,流场径向静压力增强效果更好;旋流器柱段区域流场切向速度增大,有利于强化旋流器分离能力。同时使用Mixture耦合RSM模型预测了离散相CaCO₃颗粒的分离效率,结果表明多进口旋流器可以在低速度入口条件下完成离散相的高精度分离。入料速度为3m/s的工况条件下,多进口旋流器分离50μm、57.5μm颗粒的底流分配率较单进口旋流器分别提升了10.60%、5.59%,对抑制旋流器溢流产品错配率和提高分级精度有积极的影响。因此,增加旋流器进口数量,可以有效提升旋流分级效率和分离精度。     

固相颗粒在旋流场形成过程中的运动分析

通过CFD-DEM耦合计算方法模拟不同粒径颗粒在FX-50水力旋流器内的运动行为,分析旋流器内旋流分离场的形成过程,连续相的运动采用求解平均化的Navier-Stokes方程得到,离散相的运动通过离散元法计算。采用欧拉-拉格朗日方法,通过Freestream曳力模型传递相间数据,分析了流体的速度场、压力场,颗粒群的速度、受力、颗粒-颗粒和颗粒-壁面的接触作用力。结果表明,当循环流与入口流汇合时,颗粒速度损失较大;当旋流场稳定后,60μm粒径颗粒群在旋流器锥段的堆积最严重,分离速度较70μm、80μm颗粒低;颗粒平均速度的变化为先减小再增大,直到以后的稳定变化。旋流场未稳定时颗粒在竖直方向的运移速度大于旋流场稳定后竖直方向的运移速度,80μm颗粒竖直方向平均速度始终大于60μm和70μm。颗粒-颗粒和颗粒-壁面的接触过程中,颗粒的受力以法向方向为主,当颗粒与壁面接触时,所受合力最大;由于流动前期颗粒在旋流器内运动轨迹不稳定,颗粒随机碰撞明显,导致颗粒平均接触力波动较大,当旋流场达到稳定状态以后,数值改变很小。     

旋流器操作和浮选性能影响因素的研究

设计并构建了气泡发生器、旋流浮选器的结构以及旋流浮选的流程.浮选性能包括两个方面:分离效率和气浮浓缩倍数.得出了压力降与处理量之间的关系;压降比与底流分率的关系;处理量与分离效率和气浮浓缩倍数的关系;底流分率与分离效率和气浮浓缩倍数的关系.     

旋流雾化塔盘水力学性能

对传统的垂直筛板进行改进,自主研发了旋流雾化塔盘。以空气-水为介质,对旋流雾化塔盘的水力学性能进行研究,考察孔动能因子、清液层高度、底隙高度和旋流器叶片数目对相对液相提升量和板压降的影响,并与现有垂直筛板进行对比。结果表明:旋流雾化塔板的相对液相提升量随孔动能因子增大而减小,随底隙高度增大先增大后减小,随清液层高度增大而增大,在旋流器叶片数目为5时,相对液相提升量最大。总板压降随孔动能因子、底隙高度、清液层高度增大而增大。旋流雾化塔盘的性能优于垂直筛板,满足设计要求。     

Effects of geometric and operating parameters and feed characters on the motion of solid particles in hydrocyclones

The effects of geometric and operating parameters and feed characters on the motion of solid particles in hydrocyclones were experimentally investigated by using a new type of laser surveying instrument named particle dynamics analyzer. The absolute radial velocity of solid particles decreases with increasing the positional radius, and the axial distribution curves of the particle radial velocity are parabolic. The particle radial velocity increases with increasing the inlet pressure or with increasing the diameter of the underflow pipe. When the particle density or the particle size increases, the absolute radial velocity of the solid particles decreases. The particle radial velocity also decreases with increasing the feed particle concentration. The axial distribution curves of the particle axial velocity are also parabolic. The axial velocity in the inner helical flow increases with the increase of the flow rate of overflow; while that in the lower positions in the outer helical flow increases with increasing the flow rate of underflow.     

旋流分离对天然气水合物除砂提纯的影响

针对固态流化开采方法开采海底天然气水合物含砂量大导致开采效率低的问题,提出原位分离工艺,设计了旋流分离装置,基于该装置利用CFD数值模拟方法研究了固相(砂和水合物颗粒)直径、入口浆体流量及浆体中砂浓度对装置分离性能的影响。结果表明,在研究范围内,砂和水合物分离效率大部分高于60%,最高达98.72%,压降大部分低于0.5 MPa,最低至0.03 MPa。砂粒分离效率随固相粒径增大先增大后趋于平稳,随浆体入口流量增大先增大后减小,随砂浓度增大而降低;水合物分离效率随固相粒径增大先增大后趋于平稳,随浆体入口流量增大先增大后减小,随砂浓度增大而降低。溢流口和底流口压降几乎不随固相粒径变化,随砂浓度和浆体入口流量增大而增大。固相粒径、入口流量、砂浓度对分离性能有较大影响,在砂粒径大于20 ?m、水合物粒径大于40 ?m、浆体入口流量约5 m3/h、入口砂浓度不超过25vol%的条件下分离性能良好。     

三产品重介质旋流器应用的探讨

阐述了三产品重介质旋流器采用有压与无压入料方式的优缺点以及无压工艺介耗高的原因,分析了脱泥入洗和粗煤泥分选设备同旋流器配合使用对分选效果的积极作用,总结出重介质旋流器用于分选重产物含量较多的原煤时,底流最大排放能力的计算式。     

A Comparative Study on the Separation of Different‐Shape Particles Using a Mini‐Hydrocyclone

The separation efficiency from water of different‐shape particles was studied experimentally using a mini‐hydrocyclone. Spherical and flaky (plate‐like) aluminum particles with the same particle size distributions were employed. Also, the effects of the feed flow rate and the temperature on the separation performance were studied. The results were investigated in terms of slurry recovery, total efficiency, and partition curves. The separation efficiency of the spherical particles increased with increasing particle size, temperature, and feed flow rate, as expected. The fishhook effect, as a noticeable phenomenon, was observed for the spherical particles. In case of the flaky particles, the separation showed an unusual behavior: The separation efficiency decreased with increasing particle size in the largest particle fraction, which has so far not been reported and addressed in this way.     

充气水力旋流器用于油水分离的试验研究

研究了充气量、进料量、分流比以及底流出口压力等主要操作参数对充气水力旋流器分离效率影响的规律 ,得出了较好的工况点 ;与相同结构参数的未充气旋流器的分离性能进行了对比 ,结果表明 ,充气旋流器能明显改善油水分离条件 ,具有较宽的操作弹性和较高的分离效率 ;同时用库尔特粒径分析仪分别测定了它们进口和底流口油滴的粒径分布 ,发现在旋流器中充入空气 ,强化了气浮 ,能够进一步分离更细粒径的油滴。     

Mechanism of Particle Separation in Small Hydrocyclone

The mechanism of particle separation in a small hydrocyclone is analyzed in this study. The separation efficiency of particles is affected by two major effects, the centrifugal and underflow effects. The fundamentals of these effects on the selectivity curve are derived from the theories of hydrodynamics. Three JIS particulate samples are separated in a 10-mm hydrocyclone. The proposed mechanism can be demonstrated by the available data. An increase in split ratio leads to an increase in the separation efficiency only for fine particles; consequently, a decrease in the separation sharpness results in a remarkable fishhook phenomenon. When the feed rate is increased by increasing the pressure drop through the hydrocyclone, the entire partial separation efficiency will be improved, but the separation sharpness and fishhook depth have no substantial varieties. The proposed mechanism can be used for explaining these phenomena, for the selection of optimum operating conditions, and for the hydrocyclone design.     

The characteristics of particle flow in the overflow and underflow standpipe of fluidized beds

Characteristics of particle flow in the standpipes of a 10 cm I.D.×120 cm high fluidized bed were investigated. The standpipes used in this experiment were vertical overflow and vertical underflow standpipes. Sand particles and polyethylene powders were employed as the bed materials. The effects of standpipe diameter, gas velocity and particle properties on the solid flow rate were determined. The experimental results showed that the flow behaviors of solids through the overflow and underflow standpipes are different with variations of operating conditions. For both standpipes, the mass flow rate of solids was strongly dependent on the standpipe diameter. For the overflow standpipe, the increase of gas velocity increased the solids flow rate. But for the underflow standpipe it decreased the solid flow rate. From the measured pressure drops, solid fractions in the standpipes were determined by the momentum balance. The obtained experimental data of solids mass flow rate were well correlated with the pertinent dimensionless groups for underflow as well as overflow standpipes.     

Effect of feed body geometry on separation performance of hydrocyclone

ABSTRACT

The misplacement of coarse particles in overflow and fine particles in underflow are problems in hydrocyclone separation. This paper proposes improved feed body design of a hydrocyclone and the effect of feed body geometry on the flow field and separation performance is investigated experimentally and theoretically using PIV and CFD, respectively. The air core formation and the velocity field are in good agreement using both approaches. Further simulated results indicate that the tapered feed body causes a reduction in fines entrainment by underflow, suitable for fine particles classification. In contrast, the conical feed body is advantageous for eliminating short circuiting.     

Experimental Study of a New Hydrocyclone for Multi-Density Particles Separation

Abstract

A new structure of hydrocyclone is designed to meet the demand of separating particles heavier or lighter than water simultaneously. Based on the conventional hydrocyclone, the structural modifications with a section in the middle and a volute chamber on the top of the hydrocyclone to accumulate the separated low density particles. Some factors that influence the separation efficiency of hydrocyclone were investigated in this paper. For the heavy phase, those influencing factors included the inlet flow rate and underflow split ratio. For the light one, different outlets for discharging the light phase were taken into account. The results show that there exists an optimum inlet flow rate for a series of underflow split ratios. The top outlet for separating light phase particles is better than the side outlet's.