Investigations on various characteristics of novel cyclone separator with helical square fins

ABSTRACT

Cyclone separators are very energy intensive devices primarily used in power and process industries to separate the particles from hot gases. Hence in the present study, the barrel wall of the cyclone separator was modified by fixing the helical square fins of sizes 5, 7.5, and 10 mm, with 30 and 50 mm pitch variations to improve its separation efficiency. Hence in the present study, various fluid dynamic characteristics which affect the separation efficiency such as axial and tangential velocities, axial pressure drops were investigated. Computational results were validated using the published experimental data for the non-finned cyclone separator and further CFD simulations were performed for novel finned cyclone separators. It was observed that for the particles’ sizes below 3 µm, finned cyclone separator with fin size 10 mm and pitch 50 mm was giving separation efficiency more than other 5 finned cyclone separators. Also 5 to 10% improvement in the separation efficiency was observed over the separation efficiency of the non-finned cyclone separator. Since main function of separating the particles from gas was unaffected rather it was improved using finned cyclone separator(s) which is important in a view of reducing serious fine particulate matter (PM2.5) emissions causing serious health issues.     

Theoretical aspects of conceptual multi-property mineral separator

ABSTRACT

The aim of the present study is to develop a theoretical concept of multi-property mineral separator (MPMS). In general, most of the conventional mineral separators exploit a single physical property difference for beneficiation. However, the idea behind MPMS is to utilize multiple physical properties of particles in a single separator for beneficiation. Mathematical formulations were developed for conceptual MPMS, where physical properties of particles such as density, magnetic susceptibility, and surface work function will be exploited in a single separator. Simulations were carried out for tracing particle trajectories in MPMS using MATLAB. Simulation results indicate that separation efficiency can be enhanced by exploiting multiple physical properties of particles simultaneously in a single separator. Based on the developed theoretical model of MPMS in the present paper, the fabrication of a prototype separator is under construction. Experimental results and validation using prototype MPMS will be reported in near future.     

Analysis of particle trajectories in a quick-contact cyclone reactor using a discrete phase model

The Eulerian–Lagrangian approach with a discrete phase model (DPM) is used to investigate the motion trajectories of the particles at the range of 1–50 μm in the quick-contact cyclone reactor, in which the cracking reactions and the separations of catalysts and products can occur respectively and simultaneously. The results show that the typical motion trajectories of the particles in the quick-contact cyclone reactor can be described as three types: trapping, escaping and dust ring. The first typical motion of particles corresponds to the particles successfully separated from the gas flow, while the other two types can lead to more coking and erosion in the reactor. Moreover, a pre-vortex flow is observed in the mixing-reaction chamber. Additionally, the grade separation efficiency of each particle size is also obtained by counting the numbers of escaping and capturing particles. The particles with diameter larger than 10 μm are separated completely from the gas. The reactor also has a strong capability to trap the particles of small diameters (5 μm <d_p<10 μm). Both results indicate that the separation efficiency of the reactor has met the requirement as a primary separator. Compared with the experimental results, the separation efficiency in the simulated method is higher than 98% with errors of no more than 1.31%. It is illustrated that separation efficiency of the reactor can be predicted by CFD simulation.     

Experimental investigations on a cyclone separator performance at an extremely low particle concentration

In order to evaluate the influence of extremely low particle concentration on separation performance of cyclone separator, the overall collection efficiencies and grade efficiencies of a cyclone separator with particle concentrations of 5-2000 mg/m³ and inlet velocities of 6-30 m/s have been investigated under ambient temperature and atmospheric pressure conditions. Aerosol spectrometer based on measuring particle number is used to measure the particle concentrations and particle size distributions of the inlet and outlet of the cyclone separator. The overall efficiency is equal to the ratio of the particle concentration difference between the inlet and outlet of the cyclone separator to the inlet particle concentration. The grade efficiency is obtained by comparing the particle size distributions of the inlet and outlet of the cyclone separator. The effects of particle concentration on separation performance are predicted by Smolik empirical model. Particle agglomeration, which has been found in the inlet and outlet of the cyclone separator, has a very important influence on the collection efficiencies and grade efficiencies of the cyclone separator at the particle concentration of 5-2000 mg/m³. The cut sizes for different inlet gas velocity with extremely low particle concentration can be quantitatively calculated by Barth model, Mothes and Loffer model and Muschelknautz model, respectively. Experimental results show that the overall collection efficiencies and grade efficiencies increased with the increasing particle concentrations and inlet velocities, and most of the particles with the diameter bigger than 10 μm can be removed by cyclone separator.     

环流预汽提组合旋流快分系统分离性能的实验研究

针对新型旋流快分器与密相环流预汽提器的优良特性,将两者耦合成一套完整的快分系统. 通过大型冷模实验,研究了该快分系统的分离特性,并考察了操作条件对系统快分效率及快分压降的影响规律. 结果表明,该系统能较好地实现气固高效分离,具有较大的操作弹性和优良的操作稳定性,冷态下分离效率在98.5%以上,最高可达99.93%,快分压降分布合理. 根据实验结果,得到该系统分离效率及压降的经验模型,计算值与实验值吻合较好.     

The downhole hydrocyclone separator for purifying natural gas hydrate:structure design,optimization, and performance

ABSTRACT

The exploitation efficiency of natural gas hydrate is highly affected by sand production. In this paper, hydrocyclone purification separator was designed. A combination of single factor with computational fluid dynamics (CFD) was used to optimize the structure parameters. The performance of optimized hydrocyclone was also investigated. It shows that the sand separation efficiency increases from 90.4% to 98.7%, and the natural gas hydrate separation efficiency increases from 89.5% to 97.8%. Furthermore, the cut size of sand and natural gas hydrate are as low as 3 and 2 µm, respectively, and separation efficiency remains above 80% under inlet parameters. It can provide some reference for the design and manufacture of the in situ purification separator for gas hydrate mixture slurry.     

Numerical and experimental study on the effect of solid particle sphericity on cyclone pressure drop

The continuous flow inside cyclone separator is usually simulated by solving the Reynolds averaged Navier–Stokes equations in Eulerian reference frame whereas the dispersed phase is modeled using Lagrangian approach. Although these methods have had a remarkable success, more advanced ideas are needed to model particulate phase in cyclones, especially the non-spherical shaped particles. Numerical simulation is verified with experimental results for the gas-solid flow in a cyclone separator. Reynolds Averaged Navier–Stokes equations (RANS) employing the RNG-based k–ε turbulence model are used to simulate the gas phase. 3-D particle tracking procedure is used for the solid phase. Three different equations for the drag coefficient are utilized in the numerical modeling to acquire more understanding of the behavior of non-spherical particles in cyclones. Computations resulted in the difference of pressure between the inlet and exit of the cyclone, and results are compared with experimental data. Experiments included measuring the separation efficiency of different shapes and sizes of particles. The results indicate that the CFD simulation can effectively reveal the pressure drop behavior as well as separation efficiency of gas-non-spherical particle flow in cyclone.     

Numerical simulation of effect of inlet configuration on square cyclone separator performance

This paper presents a numerical study of the gas-solid flow in square cyclone separators with three types of inlet configuration. Three-dimensional Reynolds Stress Model (RSM) was used to simulate the turbulent flow of gas phase and a Lagrangian equation was used to simulate the particle motion. The resulting velocity, separation efficiency and pressure drops were verified by comparison with measured data. The effect of inlet configurations on the turbulent dynamics in the cyclone and the separation efficiency and pressure drop was analyzed. Results showed that inlet configurations influenced the turbulent dynamics in the cyclone and led to different pressure drop and separation efficiency. The separator with double declining inlets (DDI) had the minimum pressure drop and similar efficiency to the separator with double normal inlets (DNI). The separator with single normal inlet (SNI) had the best separation efficiency and the maximum pressure drop. When a baffle was installed in the inlet of separator SNI, the pressure drop increased by about 191% and 34% for the separator with a straight (SNI-1) and curved (SNI-2) baffle respectively on the basis of the pressure drop of separator SNI. The cut and critical diameter of particles were 2 μm and 14 μm for separator SNI-1 and 4 μm and 14 μm for separator SNI-2, while they were 8 μm and 30 μm for separator SNI at the same inlet conditions.     

Performance Characteristics of a New Continuous-Flow Electrophoresis Instrument

Abstract

An instrument is described for the continuous separation of particles by means of electrophoresis. The effect of field strength, electrolyte flow rate, and sample flow rate on migration distance and particle band width were investigated. The interrelationships between the various operational parameters and particle band resolution are discussed.     

导叶式旋风管排尘口处颗粒返混夹带现象

通过数值模拟的方法,研究导叶式旋风管内颗粒返混夹带现象。研究表明,排尘口下方存在明显的灰斗返混现象,颗粒返混质量流率占入口颗粒质量流率的38%,排尘锥内部颗粒返混夹带量占入口颗粒流率的47%;排尘口上方1.1D(D为旋风管直径)范围是主要的二次分离空间,最终影响分离效率的返混颗粒仅占入口颗粒质量流率的2.5%;13 μm以下的返混颗粒会对分离器总效率产生影响,粒径越小,影响作用越明显。     

高效复合聚结板式油水分离器的开发

通过对聚结板式油水分离器传质过程机理的研究,开发出能够强化油水分离过程的新型高效复合聚结板。复合聚结板的两表面分别具有良好的亲水和亲油性能,迎合了油水分离过程要求,从而使聚结板式油水分离器的分离效率提高25%,处理能力增加40%。文中还对复合聚结板式油水分离器的主要结构参数和操作参数进行了优化,为工程设计提供可靠的理论依据。     

Effect of a Stick on the Flow Field in a Cyclone and the Pressure Drop Reduction Mechanism

Measurements of the flow field in a cyclone separator with and without a reducing pressure drop stick (Repds) showed that the Repds reduces the peak tangential velocity, the axial velocity gradient, and the radial gradients of static and total pressure and reverses the axial static pressure gradient. These changes reduce the energy consumed by the rotating kinetic energy, the internal friction, the turbulent kinetic energy, and the drag of the negative pressure difference. The results are used to discuss why the separation efficiency remains high while the pressure drop is reduced. The results also show that a 24% "short flow" occurs near the cyclone entrance. Analysis of the changes in the flow field and the pressure drop due to the thin stick shows that the Repds increases the pressure drop in the outer vortex zone and reduces the pressure drop in the inner vortex zone. Therefore the pressure drop reduction with the Repds is due to its wake vortex, which leads to the hypothesis that the pressure drop in turbulent flow can be reduced by adding vortexes.     

Numerical simulation and experimental study of gas cyclone–liquid jet separator for fine particle separation

To address the shortcomings of existing particulate matter trapping technology, especially the low separation efficiency of fine particles, herein, a novel gas cyclone–liquid jet separator was developed to research fine particle trapping. First, numerical simulation methods were used to investigate the flow field characteristics and dust removal efficiency of the separator under different working conditions,and to determined suitable experimental conditions for subsequent dust removal experiment...     

Effects of separation space diameter on the performance of a novel reverse flow cyclone

ABSTRACT

A numerical study was carried out to investigate the effect of separation space diameter on the performance of a novel reverse flow tangential inlet cyclone design by using the Eulerian-Lagrangian approach. The design of this cyclone is based on the idea of increasing vortex length and decreasing pressure drop compared with traditional cyclones. This novel cyclone differs from the traditional cyclones with separation space and vortex limiter instead of the conical part. A qualitative numerical study was performed to analyze the effect of separation space diameter on the cyclone performance at different flow rates by evaluating velocity profile, pressure drop, fractional and overall efficiencies. The results show that the collection efficiency of smaller particles increases while pressure drop decreases significantly with the increase in separation space diameter for D₁/D < 0.5.     

Reducing Pressure Drop in Cyclones by a Stick

It is found that a thin stick inserted into a cyclone separator can substantially reduce the pressure drop. The percentage reduction in pressure drop is dependent on the cross-section shape, size, and placed position of the stick. By using talcum powder (mass mean diameter is 10.14 mu m) as the test powder, the experiment results show that the stick can reduce the pressure drop of the cyclone by approximately 20% at the same total separation efficiency and flow rate. If the cyclone is used in a two-stage separation system and a reduction of the efficiency within 5% is permitted, the pressure drop can be reduced more than 50%.     

旋流气固分离器内气粒两相运动特性及分离效率

基于旋转气固多相流复杂的运动特征,结合旋流气固分离器的特点,同时考虑颗粒间的碰撞与并聚和喷水加湿对颗粒间并聚及碰撞、颗粒运动特性的影响,并考虑颗粒对气相的作用构建了描述旋流气固分离器内湍流气固多相流的三维时均方程组.模型封闭采用κ-ε/ RNG模型,数值模拟了旋流气固分离器内气固两相流场、固相运动特性及分离效率,提出了合理的旋流气固分离器分离效率计算关联式.     

Effect of Agglomerate Pore Structure on Efficiency of Solid-Liquid Separation by an Agglomeration Technique: Use of a Model System

Abstract

Solid-liquid separation is often difficult to achieve when the solids are finely divided. When the liquid involved is a hydrocarbon, the economics of any process involving such a separation will often depend on the ease and efficiency of liquid recovery. A process is described in which an enhanced solid-liquid separation is achieved by means of a size enlargement technique requiring agitation with a second immiscible liquid, which preferentially wets the solid surface. Potential applications for such a process include removal of ash particles in coal liquifaction and separation of solids from solvent extracted oil-sands. In this work a model system has been used in an attempt to better understand the process mechanics and the factors which affect the efficiency of liquid separation.     

Function and effect of the inner vortex on the performance of cyclone separators

The inner vortex plays a key role in the performance of cyclone separators. To explore the function and effect of the inner vortex in cyclone separators, a series of metal rods and metal blades are inserted in the typical Lapple cyclone separator to reduce the intensity of the inner vortex. First, the changes in general performance of cyclones are measured by experimental methods after insertion of the metal rods and metal blades. The flow field and particle motion are then simulated, respectively, by means of a Reynolds stress model (RSM) and a Lagrangian particle tracking (LPT) model. The results show that when the length of the metal blades is less than the boundary between the inner and outer vortexes, that is, the outer vortex remains unchanged and the inner vortex is destroyed partly, the separation efficiency remains constant and the pressure drop significantly decreases. When the length of the metal blades exceeds the boundary, the inner vortex is completely destroyed, and the outer vortex is significantly damaged, which results in sharp decrease of both the separation efficiency and pressure drop. The results indicate that the inner vortex has a notable effect on the pressure drop and virtually none on the separation efficiency. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4508–4518, 2017     

旋风分离器分离性能的数值模拟与分析

以XLPB-5.0和XCX-5.0两种旋风分离器为原型,采用CFD软件对这两种旋风分离器进行了流场与分离效率的数值模拟,初步探讨了入口蜗壳形式与芯管结构对分离效率的影响。模拟结果显示:旋风分离器内流场呈各向异性分布特点,切向速度是影响分离效率的首要因素,径向速度的存在会造成"流场短路"现象,使轴向速度呈不对称分布,导致分离效率的降低。轴向速度与径向速度的共同作用促使颗粒在旋风分离器内做螺旋运动;XLPB-5.0和XCX-5.0的分离效率分别为92.55%和94.96%,与实验结果基本吻合,且不同芯管参数下XCX型的分离效率比XLPB型高;螺旋式入口蜗壳(XCX-5.0型)对旋风分离器上部流场的影响相比直流式入口蜗壳(XLPB-5.0型)复杂;对于两种旋风分离器,随着芯管直径的增大,分离效率逐渐变小;随着芯管深度的增大,分离效率先增大后减小。     

The Effects of Vortex Finder Dimensions on the Natural Vortex Length in a New Cyclone Separator

The shape and structure of the vortex formed inside a cyclone separator are very important for the cyclone efficiency, because they mainly govern the separation process. There are many geometrical and operational parameters affecting the vortex. This paper presents experimental results on the effects of the vortex finder dimensions and the surface friction on the vortex length. The cyclone used in this investigation is cylindrical with no conical bottom. The cyclone pressure drop and the vortex length are recorded for each test performed using different flow rates. The results reveal that an increase of the cyclone height, i.e., of the frictional surface, leads to a decrease of the vortex length. It was also shown that the diameter and length of the vortex finder adversely affect the vortex length.