Research on High-Efficiency Cyclone Separators and Their Optimum Design

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Cyclone dimensionless pressure drop,cut size,and separation slope:One dimensionless number(Reynolds)to rule them all

The flow field and performance characteristics of the high-efficiency Stairmand cyclone have been computationally investigated at a wide range of Reynolds numbers Reout=84−252876 by varying the cyclone diameter,inlet velocity,operating temperature and pressure using the LES simulations.The effects of these parameters on the dimensionless cyclone performance characteristics(Euler number,square root of Stokes number and slope of the transformed grade efficiency curve)and dimensionless lip flow and lip velocity have been revealed.Five critical Reynolds numbers which correspond to the transition between different regimes and sub-regimes have been determined.All three dimensionless cyclone performance characteristics and two lip flow characteristics are ruled by the Reynolds number.

Pressure Drop in Cyclone Separator at High Pressure

For the design of pressurized circulating fluidized beds, experiments were conducted in a small cyclone with 120 mm in diameter and 300 mm in height at high pressures and at atmospheric temperatures. Influence of air leakage from the stand pipe into the cyclone was specially focused. A semi-empirical model was developed for the prediction of the pressure drop of the cyclone separator at different operate pressures with the effect of air leakage and inlet solid loading. The operate pressure, air leakage and inlet solid loading act as significant roles in cyclone pressure drop. The pressure drop increases with the increasing of pressure and decreases with the increasing of the flow rate of air leakage from the standpipe and with the increasing of the inlet solid loading.

Modeling and Experimental Validation on Pressure Drop in a Reverse-flow Cyclone Separator at High Inlet Solid Loading

High inlet solid loading is one of the most important features of cyclone separators in high density circulating fluidized beds （CFB）. In this work, the effect of high solid loading on pressure drop in a reverse-flow cyclone was experimentally studied. The particles used were sand and 2zAl203. Art extended range of inlet solid loadings （M）, up to 30 kg of solids/kg of air was tested at different inlet air velocities （Vin=16~24 m/s）, well beyond the solid loading range reported before. The experiments showed that, in the tested range of solid loadings, the cyclone pressure drop decreased dramatically with increasing solid loading when M〈7.5 kg/kg and then almost remained constant. A new semi-empirical model for predicting cyclone pressure drop was also developed. The calculated and experimental results showed good agreement for particle free flow and particle laden flow.

Effect of inlet area on the performance of a two-stage cyclone separator

The cyclone separator is an important separation device.This paper presents a new type of embedded two-stage cyclone,which includes a 2 nd-stage cyclone(internal traditional cyclone)with multiple inlets and a 1 st-stage cyclone(outer cylinder)that unifies the 2 nd-stage cyclone inlets into one inlet.The Taguchi experimental method was used to study the two-stage cyclone separator’s inlet area on its performance.Studies have shown that the increase of the 1 st-stage cyclone inlet area and the increase in the number of 2 nd-stage cyclone inlets(N)positively affect reducing the pressure drop and a negative effect on efficiency.It is recommended to use 2 S(the original 1 st-stage cyclone inlet area)of the 1 st-stage cyclone inlet area and 2 N of the 2 nd-stage cyclone inlets when separating fine particles.Compared with a traditional cyclone,the pressure drop is reduced by 1303 Pa,the mass separation efficiency(Eq)is increased by 0.56%,and the number separation efficiency(En)is increased by 2.05%.When separating larger particles,it is recommended to use 2 S of the 1 st-stage cyclone inlet area and 4 N of the 2 nd-stage cyclone inlets.Compared with a traditional cyclone,although Endecreases slightly,the pressure drop is reduced by 3055 Pa,and the Eqis increased by 0.56%.The research results provide new insight into the design of the cyclone.

Control of Collection Efficiency for Axial Flow Cyclone Dust Collectors with Fixed Guide Vanes and with Funnel Shaped Exit Pipes

The experimental result of the collection efficiency of the axial flow cyclone with the fixed guide vanes is lower than that with the tangential inlet pipe to the cyclone body due to the weak angular momentum transfer given by flowing through the guide vanes. However, one of the interesting points is the control of the collection efficiency depended on the funnel shaped exit pipes. The collection efficiencies for these funnel shaped exit pipes are depended on the Froude number. Then, in this paper, the experimental results of the pressure drop and also the collection efficiency using the fly-ash particles and also the comparison of the calculated results of the collection efficiency with the experimental results are described i~ detail.

Collection Efficiency of Cylindrical and Elliptic Cyclone Dust Collectors with Vortex Breaker

The cyclone dust collector is applied to many kinds of industries and also there are many types of cyclones which are selected for the application and the placement of the establishment. However the cross section of these cyclones is the circular cylindrical section for the optimum condition of the turbulent rotational flow. However from the energy consumption and the collection efficiency points of view, the circular cross section of the cyclone is not always recommended but the elliptic cross section is recommended. Therefore in this paper, the detailed experimental results of the collection efficiency for the circular cross section and for the elliptic cross sections of the eccentricity =0.5,0.6and 0.7 are reported. The test dust for these experiments is fly-ash of the mean diameter Xpm=18.0 μm and 18.3 μm. The feed particle concentration is Co=1.0-50 g/m3.

Characterization of multiphase gas–solid flow and accuracy of turbulence models for lower stage cyclones used in suspension preheaters

This study involved the analysis and characterization of the multiphase flow phenomenon inside the lower stage cyclone separator used in the clinker burning process.The analysis was performed using both CFD and experimental research methods.Very few studies are devoted to such types of cyclone separators,which in addition to their basic functions are also responsible for the technological process.Due to the atypical working conditions of these cyclone separators,they are characterized with a complex geometry,which significantly differs from that of the traditional separators.Furthermore,the evaluation of the accuracy and level of reliability of the two models of turbulence closure—k-e RNG and RSM(RANS),and the LES.The results obtained led to the conclusion that for the lower stage cyclone separators,the LES model proved to be the most accurate(both in the case of forecasting the separation efficiency and pressure drop).The performance parameter(in particular the separation efficiency)values obtained for the RSM model were also characterized by high accuracy.The k-e RNG model was characterized by significantly larger deviations.

Effect of inlet volute wrap angle on the flow field and performance of double inlet gas cyclones

In response to the divergent understanding of double inlet cyclone performance in the literature,the effect of inlet volute wrap angle on the performance and flow field of double inlet cyclone separator was studied by Computational Fluid Dynamic(CFD)method.The results showed that the inlet volute wrap angle can affect the comparison results of the single and double inlet gas cyclones with the same total inlet cross-sectional area and velocity.0°and 90°volute double inlet improved the efficiency mainly by separating particles below 10μm,while 180°volute double inlet had no separation advantage for any particles,so the symmetrical double inlet does not always improve the efficiency,and the appropriate inlet volute wrap angle should be selected according to the actual situation,otherwise,the expected performance requirements of the symmetrical double inlet cyclone cannot be achieved.Compared with the flow field,it is found that the inlet volute wrap angle changed the tangential velocity of the sym-metrical double inlet cyclone separator,thus changing the performance.

Experimental and numerical study of a gas cyclone with a central filter

This paper studies a novel gas cyclone with a cylindrical fiter face installed in the center from the vortex finder to the bottom hopper.The experimental results show that this composite cyclone has a higher collection fficiency and a lower pressure drop than the original cyclone.The mechanisms for the improvement are analyzed by both physical experiments and numerical simulations.By measuring dust samples collected at different places it is revealed that the center filter can prevent fine particles from entering the inner vortex and escaping,which accounts for the increase of the collection eficiency.In addition,the flow field of the composite cyclone is simulated by computational fluid dynamics and compared with that of the original cyclone.The analysis shows that with the filter layer installed,the swirling flow disappears in the vortex finder,which decreases the kinetic energy dissipation and hence lowers the pressure drop.

OPTIMIZATION AND APPLICATIONS OF REVERSE-FLOW CYCLONES

An optimum design approach to reverse-flow cyclones based on the concept of optimizing cyclone dimensions is introduced in this paper. This approach involves optimizing cyclone dimensions by categories, calculating cyclone performance by correlating similitude numbers and optimizing the combination of four cyclone parameters, D, KA, dr and vi, which has been proven to be applicable not only for single-stage cyclone, but also for multistage cyclone separators. Applications of the designed cyclones in FCC units and acrylonitrile reactors are also presented.

旋风滤布除尘器的除尘性能研究

为了解决传统旋风除尘器对颗粒捕集效率差、袋式除尘器使用寿命短等问题,将传统旋风除尘与滤布除尘有效结合,形成一种优势互补的一体式旋风滤布除尘装置。采用数值模拟和试验相结合的方法,探究在不同出口压力的条件下,旋风滤布除尘器的除尘效率及压力损失情况。利用Fluent软件对旋风滤布除尘器的除尘性能进行模拟,模拟采用雷诺应力模型(Reynolds Stress Model, RSM)和多相流模型(Discrete Phase Model, DPM)。通过搭建试验平台,测试除尘装置的除尘性能,验证数值模拟的可靠性与正确性。结果表明:旋风滤布除尘器的除尘效率相对于旋风除尘有明显的提高,旋风滤布除尘器的除尘效率与出口负压呈正相关,旋风滤布除尘总效率随出口负压的增加而逐渐增加,且旋风滤布除尘器除尘效率的最小值都高于旋风除尘部分除尘效率的最大值;旋风滤布除尘器的压力损失随出口负压的增加而线性增大,压力损失增大使得除尘器损耗的功率也增多,且压力损失的上升速度快于除尘效率的提升速度;在旋风滤布除尘器中,负压增大后,旋风除尘捕获大粒径颗粒,逃逸到滤布部分的颗粒粒径都较小,降低了滤布被大颗粒划破的风险,提高了滤袋的使用寿命。

旋风洗涤除尘器压降及流体动力学特性

旋风洗涤除尘器结构相对简单且除尘效率高,是对煤炭地下气化产出的粗煤气进行净化处理的可靠设备。通过室内实验和CFD数值模拟相结合的方法,研究旋风洗涤除尘器压降规律和相应的流体动力学特性。实验测量单气相和气液两相流动条件下旋风洗涤除尘器的压降,考察气体流量、液气比(体积比)和喷淋位置对设备压降的影响规律,并基于验证的数值模型确定旋风洗涤除尘器内的流体动力学特性。结果表明:旋风洗涤除尘器压降随气流量增加而显著增加,且在当前的液气比以及改变喷淋位置对设备压降的影响较小。当前确定的设备结构可以有效实现旋风除尘和喷淋除尘,但除雾滴用起旋板上方的流场可以进一步优化,以便实现气流夹带液滴的有效去除。

新型双筒体旋风分离器的分离性能和流场

为降低普通逆流式旋风分离器的阻力,设计了一种双筒体旋风分离器(简称双筒体分离器),即在筒体内部增加一个同心内筒、进口移至筒体下端、升气管插入内筒一段长度。通过冷模对比实验和数值模拟研究了该双筒体分离器的分离性能和流场。结果表明:双筒体分离器的效率在低入口气速区低于PV型高效旋风分离器(简称PV型分离器),但当入口气速高于28 m/s时则高于PV型分离器;双筒体分离器的效率总是高于环流式除尘器;压降与环流式除尘器相近但比PV型分离器低约50%。双筒体分离器耦合了常规逆流和直流旋风分离器中的2种旋涡流动,克服了逆流式分离器气体流路长和顶灰环的缺陷,同时还增加了部分细颗粒循环再分离的机会,效率高于直流式旋风分离器,是一种具有较低阻力和较高分离效率的新型旋风分离器,对于入口颗粒稍粗的分离应用具有显著的节能优势。

Structural Optimization of a Novel Up-run Gas-solid Separator

A new gas-solid separator dedicated to heavy-oil fast pyrolysis process incorporating inertial and centrifugal separation was designed. Gas and typical fluid catalytic cracking （FCC） catalyst particles （with a density of 1500 kg/m3, and a mean diameter of 45.81 p.m） were used in the study. The inlet gas velocity was kept constant at 13.36 m/s, while the solid loading at the inlet ranged from 0 to 700 g/m3. When the exhaust pipe opening was provided with two narrow-width slots near the inlet without baffles, the solid collection efficiency increased with an increasing solid loading at the inlet and was close to 95% along with a decreasing pressure drop. After increasing the secondary separation structure, the separation efficiency greatly improved. By adjusting the diameter of the secondary exhaust pipe, the separation efficiency and pressure drop could be balanced. Under the experimental conditions, when the diameter of the second exhaust pipe was equal to d=100 mm, the pressure drop was lower than 1400 Pa while the separation efficiency could exceed 99.50%; and when the diameter was equal to d=120 mm, the pressure drop was less than 700 Pa, with the separation efficiency reaching over 99.00%.

流化床气化旋流—过滤复合除尘设备的功能耦合研究

流化床气化出炉合成气中含尘量高,通常采用多级旋风分离器+颗粒床过滤的方式进行气固分离,工艺流程较长。本文提出一种耦合旋流分离与过滤分离功能的新型旋流-过滤复合除尘设备,可缩短除尘工序工艺流程。通过冷模实验考察了复合除尘设备的分离性能,采用正交实验方法确定了各因素的影响程度,采用单因素实验获得了除尘器性能的变化规律。研究结果表明,旋流分离可去除大部分粒径>1μm的粉尘颗粒,颗粒床过滤几乎可以捕集<1μm的大部分微细粉尘,复合除尘设备的整体分离效率稳定在99.9%以上。

循环流率对循环流化床回路压降影响的实验研究

对于布置有流动密封阀的循环流化床反应器,其系统压力满足自平衡的特性,固体颗粒循环流率Gs和循环回路的压力平衡具有直接的联系。该文在冷态循环流化床实验台上研究了循环流率对系统各部件压降的影响:在流化风速一定时,随着流动密封阀回料风量升高,回料阀流动阻力下降,循环流率升高;提升管内床压降较高时,炉膛内物料体积份额增大。当Gs超过一定值时,提升管内进入"S"型分布的快速流态化,顶部达到饱和携带状态;分离器压降随着颗粒携带浓度Cs的增加先降低后升高,其转捩点约为3.2kg/m3;立管内负压差移动床的流动状态可以通过改变孔隙率和压差梯度,利用较低的料封实现较高的压头,自动吸收其他部件的压降波动,维持系统平衡。

PDC型高效旋风管的流场分析及结构改进

在ＰＤＣ型旋风管流场测试研究的基础上，开发了ＰＳＣ型旋风管，对比研究和分析结果表明，ＰＳＣ型旋风管结构简单，对细粉有较高的分离效率，使用性能指标优于ＰＤＣ型旋风管。

针对矿山细粉尘的新型微雾旋风除尘系统

设计、研发一个高效、经济的新型微雾旋风除尘系统,以解决煤矿细颗粒粉尘难以捕集这一难题。采用离散相模型的粒子跟踪技术,对雾滴场与粉尘场进行耦合研究。并从粉尘质量浓度、分离效率和压降等指标对微雾旋风除尘系统和旋风分离器进行对比分析。结果表明:微雾旋风除尘系统的雾化场能够完全捕捉旋风分离器排气口逃逸的细颗粒粉尘,分离效率显著提高;同时,被捕捉沉降至灰斗的粉尘颗粒表面形成一层水膜,使细颗粒粉尘平均粒径增大,避免被气流再次卷起带走,可有效抑制二次扬尘。

天然气净化用多管旋风分离器的分离性能

为了系统评价天然气净化用多管旋风分离器的分离性能,在线测量了入口气速6～24m/s、入口颗粒浓度30～2000mg/m3范围内多管旋风分离器的分离效率和分级效率.结果表明,多管旋风分离器的分离效率和分级效率都随入口气速和入口颗粒浓度增大而提高.与单管旋风分离器相比,在相同实验条件下,多管旋风分离器的分离效率下降2%～15%;单管旋风分离器基本能除净粒径大于10μm的颗粒,而多管旋风分离器只能去除15μm以上的颗粒.多管旋风分离器的压降主要是内部单管旋风分离器的压降,占整个压降的80%～90%.