Reverse Flow Cyclone Research Articles

Particle Cut Diameter Prediction of Uniflow Cyclone Systems with Fuzzy System Analysis

Cyclones are devices used in various industries to remove particulate matter from gases and liquids. Commonly used in the power generation, cement, and mining industries, cyclones improve the efficiency and longevity of equipment by removing dust and other small particles that can cause wear and damage. Among centrifugal separation, reverse-flow cyclones are primarily used for particle separation, which can reach heights of several meters on an industrial scale and therefore, are difficult to access for maintenance. A uniflow centrifugal segregation system avoids these drawbacks of reverse-flow cyclones since their accessibility is good and their height usually does not exceed their diameter. The efficiency is a critical aspect of separating systems. This study systematically examines the collection efficiency for particles ranging from 1 µm to 29 µm in diameter based on varying vane angles of the swirl inducer at flow rates ranging from 130 L/s−1 to 236 L/s−1.

Calculation of the Flow Hydrodynamics in Reverse-Flow Cyclones Using the Flow Vision Software Package

Calculation of the Flow Hydrodynamics in Reverse-Flow Cyclones Using the Flow Vision Software Package

Comparing Efficiency per Volume of Uniflow Cyclones and Standard Cyclones

AbstractA competitive alternative to the standard reverse flow cyclone for gas‐solids separation is the uniflow cyclone. Gas and particles passing through it in only one direction, allowing a cost‐effective usage in space limited applications. Comprehensive studies of uniflow cyclones have strongly improved their understanding and led to approved design criteria and calculation methods. Here it is shown that uniflow cyclones can achieve higher efficiencies per volume with a low pressure drop than standard cyclones.

Design criteria for multicyclones in a limited space

Multicyclones for gas-solids separation consist of many parallel cyclone cells within a common housing having a common solids hopper. They are preferably used for high-efficiency separation of a gas-solids flow. Principally increasing the number of cyclone cells and decreasing their size improves the efficiency of a multicyclone without changing the flow cross-section of the device and its pressure drop. The prerequisite for that is however that gas and solids can be equally distributed among all cyclone cells and bypass flows through the solids discharge openings from one cyclone cell to the other can be avoided.In many cases, multicyclones use standard reverse flow cyclone cells with an axial inlet, also called swirl tubes. Alternatively, multicyclones can be made from uniflow cyclone cells. Deviating from swirl tubes uniflow cyclones have gas and particles passing through them in only one direction exiting at the same end of the device which makes them much more compact than swirl tubes. In recent years comprehensive experimental and theoretical studies of uniflow cyclones have strongly improved their understanding and led to approved design criteria and calculation methods similar to those which have already been achieved for standard reverse flow cyclones. In the present investigation well-proven calculation programs have been applied to compare multiclones based on swirl tube cells with those based on uniflow cyclone cells regarding their efficiency to separate a specified gas-solids feed at a given pressure drop. The investigation has been performed by varying the available space for the dedusting device, the number of cyclone cells, the cyclone pressure drop, the particle size distribution of the feed and the particle density. The results indicate that, under the considered operation conditions, a uniflow multiclone is more efficient than its swirl tube counterpart if space is limited onto about the volume needed by the uniflow multiclone for its optimum performance and the available pressure drop is low. Furthermore, the results show, that regardless of any limitation on volume or pressure drop the efficiencies of both multiclone types approach each other with increasing cell number, pressure drop and particle size, as well as particle density of the solids feed.

Performance analysis of axial and reverse flow cyclone separators

Performance characteristics of a novel cyclone with tangential inlet were presented in axial and reverse flow operation modes. 3-D and unsteady governing equations were used for the numerical solution of the two-phase turbulent flow in the cyclone separator. The Eulerian approach was used to solve the flow field, and the Reynolds Stress Model (RSM) with the scalable wall function was employed for the numerical study. The Lagrangian approach with the Discrete Phase Model was used to calculate the discrete phase by releasing particles from the inlet surface. CFD calculations were run for different geometric configurations to analyze the performance of the cyclones regarding pressure drop, cut-off diameter, and fractional efficiency. Axial and tangential velocity profiles are presented at the defined sections. The computational results of pressure drop, velocity field, and separation efficiency were also compared for the axial and reverse flow cyclones at the same flow rate. The results show that pressure drop and collection efficiency in reverse flow mode are higher than that of the axial flow operation. However, axial flow cyclones seem to be more efficient for small particles comparing to reverse flow cyclones.

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

ABSTRACTA 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.

Numerical prediction of short-cut flows in gas-solid reverse flow cyclone separators

The effect of operational and geometrical parameters on the short-cut flow in cyclone separators has been investigated computationally using the Reynolds stress model (RSM). The motion of solid particles in the flow field was simulated using the Eulerian-Lagrangian approach with one way discrete phase method (DPM). Eleven cyclones with different cone tip diameters, vortex finder lengths and diameters were studied and the simulation results were analyzed in terms of velocity fields, pressure drops, cut-off diameters and short-cut flows. The numerical simulation was verified with the published experimental results. The results obtained demonstrate that all three parameters, particularly, vortex finder diameter, have significant effects on the cut-off diameter (collection efficiency), the short-cut flow and the pressure drop.

The rapid development of small scale cyclones — numerical modelling versus empirical models

Taking an alternative approach to correlation-based methods of performance prediction, this study focuses on the use of computational fluid dynamics (CFD) as a rapid development tool for small scale cyclones for use in vacuum cleaners. Operating with high flow rates the highly swirling, dust laden flows within these cyclones provide a substantial challenge to current numerical models. Using empirical data gathered from previous investigations on four small scale reverse-flow cyclones, with body diametres ranging from 29 to 52mm and operating with flow rates of 60 to 540lmin−1, the performance of the CutCell assembly mesh and a standardised approach to particle modelling is assessed. The performance of the numerical method to accurately predict pressure drop and separation efficiency is also compared against nine established cyclone performance prediction models, with the capability of the CFD being demonstrated to be superior to or comparable with traditional models.

Similitude in cyclone separators

Criteria for similitude in reverse flow cyclone separators are developed in this paper explicitly including the inlet particulate probability distribution. The application of these criteria is demonstrated by example using data from the literature. Some practical points to consider when using cyclone similarity relations are presented in the Conclusion.

Vortex cleaning of fuel tank pressurant gas

One of the problems of space launch vehicle fuel tanks using gas pressure accumulators is dealt with in the article. Helium mixed with gas generator gases is used as a pressure gas accumulator, which makes it possible to increase the specific volume of pressurant gas and decrease the mass of the system. Gas generator gas comprises carbon particles that cause fast clogging of the filter, which leads to a contingency and charge pressure drop. The use of soot-cleaning vortex apparatus was suggested for efficient fail-safe operation of the tank pressurization system. Different types of vortex soot- cleaning devices were considered. A reverse-flow cyclone was chosen as the most appropriate type of vortex soot cleaner for a fuel tank pressurization system. The required soot cleaner was designed and its flow part was modeled. A finite element mesh was obtained and boundary conditions were set. Numerical modeling of the soot cleaning process was carried out in a reverse-flow cyclone with the help of ANSYS Fluent. Fields of soot particle distribution and the character of their motion in the reverse-flow cyclone were plotted.

An empirical investigation into the influence of pressure drop on particle behaviour in small scale reverse-flow cyclones

The operation of small scale reverse-flow cyclones under high flow rates and light solid loadings is poorly understood. This empirical study extends previous investigations into the relationship between particle behaviour and cyclone operating conditions. Previous work concluded that particle agglomeration and attrition occurring in a small scale Stairmand cyclone were heavily dependent on inlet velocity. We report on the performance of two cyclones with similar geometries, but with a 66.2% difference in their vortex finder diameters. Despite inlet velocities that differ by less than 5.7%, the relative pressure drops vary between 96.5 and 105.7% from each other, which contributes to a significant difference in the separation efficiency curves of the two cyclones. The smaller vortex finder diameter produces superior separation efficiency and increased particle attrition. This implies that pressure drop across the cyclone and not inlet velocity is the critical parameter when considering particle behaviour in cyclones of different designs. The study also demonstrates the non-linear relationship between particle cut-size diameter and pressure drop, implying that the cut-size diameter may approach an optimum size. Further to these investigations the study reports near identical separation efficiency curves produced by two geometrically dissimilar cyclones. Although the inlet and vortex finder velocities of the two cyclones differ by 41.0% and 65.3% respectively, there is only a 2.1% difference in pressure drop. This observation prompts the suggestion that the influence of pressure drop on separation efficiency is greater than considerations of cyclone geometry and scale.

Cyclone optimization including particle clustering

In this work, a new family of geometries of reverse-flow cyclones was obtained through numerical optimization, using a stochastic random search global optimizer coupled with the PACyc model. The objective was to optimize the geometry of a reverse-flow cyclone taking into account inter-particle agglomeration (clustering), since this phenomenon usually occurs to some degree in industrial cyclone operation, increasing the collection of fine particles.Experimental results for three kinds of particles and particle size distributions are shown using a pilot-scale unit. An industrial implementation of the new optimized cyclone is described and the results concerning the performance of the system are shown and compared with predictions from the PACyc model.The results show a highly improved global efficiency when compared to that of a cyclone geometry obtained by a similar optimization methodology while neglecting the agglomeration/clustering effect. This opens the possibility of using reverse-flow cyclones to capture very fine particles, complying with strict emission limits, such as those from biomass boiler exhausts.

Welding Spark Parameters Determination for Cyclone Removal Calculation

Many factors have an essential impact on the air purification efficiency. Very important for a lot of industries is to choose right air purification system. Especially important is to take into account manufacturing including generation of combustible and explosive dust. One of the way to prevent possibilities of fire and explosion is using reverse flow cyclone as a pre-cleaning system. In the article the efficiency of such precleaner is showed and experimentally proved.

Potential of a Cyclone Prototype Spacer to Improve In Vitro Dry Powder Delivery

PurposeLow inspiratory force in patients with lung disease is associated with poor deagglomeration and high throat deposition when using dry powder inhalers (DPIs). The potential of two reverse flow cyclone prototypes as spacers for commercial carrier-based DPIs was investigated.MethodsCyclohaler®, Accuhaler® and Easyhaler® were tested with and without the spacers between 30 and 60 Lmin−1. Deposition of particles in the next generation impactor and within the devices was determined by high performance liquid chromatography.ResultsReduced induction port deposition of the emitted particles from the cyclones was observed due to the high retention of the drug within the spacers (e.g. salbutamol sulphate (SS): 67.89 ± 6.51% at 30 Lmin−1 in Cheng 1). Fine particle fractions of aerosol as emitted from the cyclones were substantially higher than the DPIs alone. Moreover, the aerodynamic diameters of particles emitted from the cyclones were halved compared to the DPIs alone (e.g. SS from the Cyclohaler® at 4 kPa: 1.08 ± 0.05 μm vs. 3.00 ± 0.12 μm, with and without Cheng 2, respectively) and unaltered with increased flow rates.ConclusionThis work has shown the potential of employing a cyclone spacer for commercial carrier-based DPIs to improve inhaled drug delivery.

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 γ-Al2O3. An 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.

Comparative Pulmonary Function and Pharmacokinetics of Fluticasone Propionate and Salmeterol Xinafoate Delivered by Two Dry Powder Inhalers to Patients with Asthma

This report presents results of the first human study of a new dry powder inhaler (DPI-C). DPI-C uses reverse flow cyclone technology to retain larger particles in the device and to increase efficiency of respirable drug release. The study was conducted to determine comparative pharmacokinetics (not bioequivalence) of DPI-C and DPI-A (Advair Diskus®, GlaxoSmithKline) and to establish preliminary efficacy and safety of DPI-C. Nineteen patients with mild-moderate asthma received two treatments (randomized crossover design). Treatments were one inhalation from DPI-A labeled to deliver 100 μg fluticasone propionate and 50 μg salmeterol, or one inhalation from DPI-C which contained ∼10% less of each drug per metered dose. Prior to dosing, 10 g of charcoal was administered. FEV1 increase over baseline (measured over 12 h), plasma concentrations of fluticasone and salmeterol (measured over 12.5 h), and occurrence of adverse events were the primary measures of device performance and safety. Seventeen patients were evaluable. Response profiles of percent increase in FEV1 over baseline showed no statistically significant differences between devices. Peak plasma concentrations of both fluticasone (p=0.003) and salmeterol (p=0.084) were higher from DPI-C. Mean extent of absorption [area under the curve (AUC)] of fluticasone was approximately 30% greater with DPI-C, whereas AUC of salmeterol was approximately 40% greater with DPI-A. DPI-C provided similar improvement in pulmonary function compared with DPI-A. Pharmacokinetic results showed a greater initial absorption of salmeterol with DPI-C but greater continued absorption and a 40% greater AUC with DPI-A, which we attribute to slower but more extensive oral absorption because of the greater mass of swallowed large particles of salmeterol generated by DPI-A. No patient reported any treatment-related adverse event or use of rescue medication during this study. Determination of the significance of the observed differences in pharmacokinetics from this single-dose study requires further exploration in studies using clinically relevant dosing regimens.

Skaičiuojamosios fluidų dinamikos modeliavimo taikymas kūginiam grįžtamojo srauto ciklonui tirti

Nagrinėjama ciklonų, skirtų kietosioms dalelėms atskirti iš oro srauto, efektyvumo problema. Apžvelgti eksperimentiniai ir teoriniai darbai. Pateiktos trimatės pernašos diferencialinės lygtys su Reinoldso įtempių turbulencijos ir kitais modeliais. Atliktas skaitinis oro srauto judėjimo modeliavimas kūginiame grįžtamojo srauto (KGS) ciklone, kurio aukštis – 0,50 m, cilindrinės dalies aukštis - 0,29 m, kūginės - 0,133 m, skersmuo - 0,20 m. Modeliuojant aprašytas oro srauto judėjimas ciklone taikant Navjė ir Stokso trimačių diferencialinių lygčių sistemą, diskretizuotą baigtiniais tūriais. Modeliavimo rezultatai, kai įtekėjimo greitis – 4,64 m/s ir debitas – 0,28 m3/s, neblogai sutapo su kitų autorių vykdytų eksperimentų rezultatais. Gauta vidutinė santykinė paklaida - ±5 proc.

Simulation study of production of fine ceramic powders in a cyclone reactor

A numerical simulation study of production of fine ceramic powders in an innovative vapor-phase aerosol reactor is described. Arrangement is typical of reverse-flow cyclone equipment; no similar device is present in current scientific literature and industrial technology. The cyclone reactor has a potential technological application as it realizes process intensification by two simultaneous operating advantages: (i) curly flow reduces recirculation of as-synthesized particles towards flame region, and (ii) cyclone arrangement segregates large particles. As a result, ceramic powders with narrower particle size distribution can be produced with regard to traditional equipment. The study is based on the re-modeling of an existing industrial reactor for production of fine TiO 2 according to a cyclone configuration; particle size distributions from simulation and plant are compared.

A Review of Rapid Gas-Solid Separation Techniques

Rapid, effective separation of phases is an essential step in many hydrocarbon conversion gas-solid processes. In heavy oil upgrading, fluid catalytic cracking (FCC) and biomass pyrolysis, for example, very fast separation of reacting gases from catalytic or heat-bearing solids is required to inhibit further reaction. The primary functions of a rapid separator in the context of a gas-solid flow are, first, to terminate contact between the reacting gases and the catalytic or hot solid particles and, second, to recover the isolated product vapors. Uninterrupted vapor-solid contact results in degraded, overcracked and generally less valuable products. Increasing interest in rapid separation has led in the past 25 years to a wide variety of proposed separator designs in the literature.Centrifugal separation is the fundamental principle underlying cyclone operation and most rapid gas-solid separation processes. Traditional cyclones rely on centrifugal separation and are very widely applicable. They are used for the removal of solid particulate matter from gas or liquid streams, for gas demisting, and in hydrocyclones. Most FCC processes employ traditional cyclone configurations for secondary and tertiary separation. The review briefly summarizes important topics studied in reverse flow cyclone operation. For initial separation, however, most fast gas-solid separators in the literature feature only partial cyclone layouts. Separation typically occurs more quickly in these devices relative to traditional cyclones, likely at the expense of separation efficiency.The current review places emphasis on experimental results and novel separation techniques in the context of fast gas-solid separation. Several recent methods of rapid gas-solid separation employ co-current or "uniflow" centrifugal arrangements. Hence, particular attention is directed to co-current centrifugal separators. These devices have been studied much less intensively than their reverse flow counterparts. Fast co-current separators, with their novel, partial cyclone layouts, are interesting for their performance characteristics in relation to popular commercial designs.

Studies of the flow in and around gas dedusters and demisters using neutrally buoyant tracer

Tracer studies of the flow in gas dedusting or demisting equipment is a problem area, since such equipment is designed to cause the paths of solid or liquid particles to deviate from the gas streamlines, conflicting with the purpose of tracer particles. This paper summarizes a number of studies of the flow in centrifugal gas cleaning equipment using neutrally buoyant tracer particles, which are helium-filled soap bubbles about 1 mm in size. The studies show vortex precession in the body of reverse-flow cyclones, vortex breakdown in the vortex finder of reverse-flow cyclones and after the outlet of once-through cyclones. They also show other features of the flow in gas cleaning equipment not visualized before. Most of the results shown a qualitative, illustrating the potential of this visualization technique.