Hydrocyclone Operation Research Articles

Prediction of operating state of hydrocyclones using vibrometry and 1D convolutional neural networks

Due to high processing capacity requirements and constraints on industrial water utilization, operation of hydrocyclones at higher feed solid concentration is often unavoidable. Hydrocyclone operation at such higher feed solid concentrations is accompanied by the risk of onset of rope discharge, adversely affecting both the size separation and thickening performance of the hydrocyclone. Numerous condition monitoring efforts have been reported in the literature regarding the development of online techniques for detection of roping in hydrocyclones. However, detection of roping, post its commencement, only ever allows for corrective maintenance in the form of measures taken for shifting the discharge back to the desired spray profile. This study focuses on the characterization and online detection of a transition discharge state which precedes the onset of roping, thereby making the prevention of onset of roping, possible. The transition discharge state was delineated from the conventional spray and rope discharge types based upon the observed differences in the decay rates of underflow discharge spray angles with increasing feed solid concentrations. A binary classification model (spray – rope) and a ternary classification model (spray – transition – rope) were developed with a 1D Convolutional neural network architecture capable of taking 5 secs of tri-axial (3-channel) vibration signal data as input, and outputting the predicted discharge type labels with an accuracy of 97.31 % and 94.94 %, respectively.

Cut-Size Diameter Calculation of Salt Crystals From A Hydrocyclone

A hydrocyclone is physical separation equipment employed in solid-liquid processing. An important parameter in hydrocyclone design is the so-called cut-size diameter (D50), which determines the minimum size of the separated solids when the equipment performs at 50% separation efficiency. This paper discusses the calculation of the cut-size diameter (D50) of a hydrocyclone operating in a salt purification pilot plant in Manyar, East Java, Indonesia. The cut-size D50 is calculated based on the residence time approach and compared with the collection efficiency from the mass balance. D50 was found to be 69.73 microns. Moreover, by using Zanker’s nomograph, it was found that at the solid separation efficiency of 80.48%, the minimum diameter of salt crystal (Dmin) is 85 microns. Because the D50 of HC-1 is smaller than Zanker’s design, it can be concluded that the hydrocyclone will work efficiently in separating the expected products.

Separation of asbestos concentrates in a hydrocyclone

Relevance. Issues related to the operation of hydrocyclones in the asbestos industry for the separation of finely split asbestos fibers from rock impurities and non-fluffed asbestos needles used in the wet enrichment of brittle chrysotile asbestos, as well as some types of amphibole asbestos and in the purification of commercial grades of chrysotile asbestos of normal strength from magnetite are considered. Purpose. The purpose and objectives of the research is to study the operating modes of a hydrocyclone for the separation and desliming of asbestos products. Particular attention is paid to the behavior of particles inside the hydrocyclone. Methodology. The formulas presented in the literature for calculating the volumetric delivery of hydro-cyclones are analyzed. As a result, it was determined that the volumetric delivery of the hydrocyclone does not depend on the size of the sand nozzle and that the influence of the latter affects mainly the specific distribution of water between the discharge and sand products. Results. In the course of processing the obtained experimental data, the calculation results showed that, at different nozzles and feed heads, the movement of grains of separation mesh in the internal flow of hydrocyclones of the tested design occurs within 1 < Re < 20. Therefore, the accepted dependences of Ψ on Re when deriving the calculated formulas are correct. Conclusions. The volumetric delivery of hydrocyclones D = 75 mm and D = 200 mm of the tested design for feeding and draining depends on the feed head and the diameter of the framework nozzle. The established regularities in the behavior of particles of asbestos concentrates in hydrocyclones are of practical importance and can be used when choosing the technological parameters of their operation to achieve the specified conditions for the size of particle separation mesh.

Effect of back pressure on the separation performance of a hydrocyclone

In industrial process applications, to shorten the process flow and use the residual energy of hydrocyclone overflow, the overflow outlet is often directly connected to the subsequent equipment, and the back pressure of the subsequent equipment inevitably affects the normal operation of the front-end hydrocyclone. Therefore, this paper uses numerical simulation to study the effect of overflow back pressure on the internal flow field and separation performance of hydrocyclones. The results show that increasing the overflow back pressure increases the total pressure drop of the hydrocyclone, has no significant effect on the internal radial pressure gradient, and only increases the energy consumption of the hydrocyclone. With the increase in the overflow back pressure, the solid phase yield of the underflow increases, the content of fine particles gradually increases, the content of coarse particles decreases, and the separation accuracy of the hydrocyclone decreases. • The effects of back pressure on the flow field were investigated. • The influences of back pressure on the separation performance were studied. • The particle size distribution of the products were analysed.

Long-term effects of hydrocyclone operation on activated sludge morphology and full-scale secondary settling tank wet-weather operation in long sludge age WWTP

This paper presents the study concerning long-term effects of a full scale hydrocyclone unit implemented in a continuous flow long sludge age system, on sedimentation, treatment efficiency and sludge morphology. The research concentrates on identifying the mechanisms of sludge behaviour within the system. The gravimetric selection of activated sludge via a hydrocyclone is a recent development for enhancing sludge separation, where heavier flocs are retained in the system, and lighter ones are discarded as waste sludge. The effects of implementing hydroclyclones were analysed with the use of SEM imagining and fractal dimensioning through the frequent assessment of sludge settling capabilities, effluent quality, and floc properties. Over the course of 60 weeks of hydrocyclone operation, sedimentation efficiency varied significantly. Sludge volume index values of 40 mL/g, achieved during the warm season, were not sustained when the temperature decreased and an overgrowth of filamentous bacteria occurred. Good settling efficiency was also observed in batch tests, where settling velocity of experimental sludge was app. 1 m/h higher than for the reference train at the same concentrations. This was confirmed during wet weather, as the experimental train sustained safe sludge blanket height in secondary clarifiers. SEM imaging and fractal dimension analysis revealed that the underflow that returned to the system had a more compact and spherical shape, which led to an increased content of granule-like particles in the reactor. The presence of flocs with a diameter exceeding 900 μm in the underflow, which is not observed in the feed, indicated agglomeration within the hydrocyclone. This is contradictory to most of the literature data coming from laboratory experiments. This phenomenon was attributed to differences in the size and geometry of the used hydrocyclones, and the potential process mechanism was presented.

Microbial response on the first full-scale DEMON® biomass transfer for mainstream deammonification

Sidestream partial nitritation and deammonification (pN/A) of high-strength ammonia wastewater is a well-established technology. Its expansion to the mainstream is, however mainly impeded by poor retention of anaerobic ammonia oxidizing bacteria (AnAOB), insufficient repression of nitrite oxidizing bacteria (NOB) and difficult control of soluble chemical oxygen demand and nitrite levels.At the municipal wastewater treatment plant in Strass (Austria) the microbial consortium was exhaustively monitored at full-scale over one and a half year with regular transfer of sidestream DEMON® biomass and further retention and enrichment of granular anammox biomass via hydrocyclone operation.Routine process parameters were surveyed and the response and evolution of the microbiota was followed by molecular tools, ex-situ activity tests and further, AnAOB quantification through particle tracking and heme measurement.After eight months of operation, the first anaerobic, simultaneous depletion of ammonia and nitrite was observed ex-situ, together with a direction to higher nitrite generation (68% of total NOx-N) as compared to nitrate under aerobic conditions. Our dissolved oxygen (DO) scheme allowed for transient anoxic conditions and had a strong influence on nitrite levels and the NOB community, where Nitrobacter eventually dominated Nitrospira. The establishment of a minor but stable AnAOB biomass was accompanied by the rise of Chloroflexi and distinct emergence of Chlorobi, a trend not seen in the sidestream system. Interestingly, the most pronounced switch in the microbial community and noticeable NOB repression occurred during unfavorable conditions, i.e. the cold winter season and high organic load. Further abatement of NOB was achieved through bioaugmentation of aerobic ammonia oxidizing bacteria (AerAOB) from the sidestream-DEMON® tank. Performance of the sidestream pN/A was not impaired by this operational scheme and the average volumetric nitrogen removal rate of the mainstream even doubled in the second half of the monitoring campaign. We conclude that a combination of both, regular sidestream-DEMON® biomass transfer and granular SRT increase via hydrocyclone operation was crucial for AnAOB establishment within the mainstream.

Iron ore slimes beneficiation using optimised hydrocyclone operation

With increasing steel production, an exponential increase in demand for steel is rapidly depleting the high-grade iron ore deposits. Hence, in search of an alternative source of iron ores, the steel industries are forced to use low-grade ores. The large amount of iron ore slimes accumulated in slime ponds at mine sites also poses a challenge for the environment. Iron ore slimes typically consist of iron, alumina, and silica at a wide range of sizes and densities. The marginally varying density components (iron oxide and alumina particles) of iron ore slimes can be separated by hydrocyclones based on size and density. Therefore, this work is aimed to experimentally study the iron ore slime beneficiation using a novel 100 mm hydrocyclone (with small cone angle, tapered vortex finder and optimum cylindrical length) design developed by computation fluid dynamics (CFD) simulation studies. As the design is developed using numerical studies, the initial experiments are conducted with mono density silica particles to test and validate the performance. Further, the experiments are continued with iron ore slimes. The novel hydrocyclone is able to provide desired cut size and sharpness of separation required to separate iron from alumina and silica. It also enhances the classification by reducing coarse and fine particle misplacement compared to the conventional hydrocyclone design. The product obtained from the underflow of the optimised hydrocyclone operation is suitable for direct pellet grade feed with iron and alumina as ∼61% and 2.77%.

Effect of rheology and solids concentration on hydrocyclones performance: A study involving the design variables of an optimized hydrocyclone

Despite several advances in the field of separations in hydrocyclones, achieving high separation efficiency in these devices when operating with concentrated non-Newtonian suspensions is still a challenge, and any improvement in this aspect can be a significant contribution. Thus, the objective of this study was to evaluate the behavior of a hydrocyclone operating with concentrated pseudoplastic suspensions. The device used in this study was the Maximum Overall Efficiency Hydrocyclone (MOEH), which is the result of a geometric optimization study developed by our research group whose objective was to obtain a hydrocyclone geometry that led to high separation efficiencies. The polymer carboxymethyl cellulose (CMC) was used as a rheological modulator at different concentrations. Changing the concentration of CMC in the suspension from 0.2 wt% to 1.0 wt%, it was observed reductions of 27% and 23% for the Euler number and overall efficiency of the MOEH hydrocyclone, respectively. When operating with dilute pseudoplastic suspensions (CCMC < 0.6 wt%), the drop in the separation performance could be mitigated with appropriate increments in the dimensions of the underflow diameter and reductions in the vortex finder length. Above a concentration of 0.8 wt% CMC the hydrocyclone operated as a stream splitter, with reduced efficiency of less than 2%, and the modifications in the design variables were not sufficient to reverse the detrimental effect of the increased slurry viscosity. The results obtained in this study show the relevant effect of non-Newtonian fluids in the functioning of hydrocyclones and the importance of the correct choice of geometric configurations and operating conditions to reduce the impact of the rheology in the separation performance.

Air column of pressure hydrocyclone with pneumatic regulator

A reliable non-contact pneumatic pressure regulator of a pressure hydrocyclone is offered. The regulator is installed in the area of ​​the sand nozzle. The pneumatic regulator of the standard pressure cylindrical-conical hydrocyclone provides non-contact thickening of the product in the area of ​​the sand nozzle. In the process of controlling the operation of the hydrocyclone along its axis, an air column is formed. Features of the regulator affect the formation of the air column of the hydrocyclone. The pressure in the air column is manometric.&#x0D; The task is to investigate the effect of pulp pressure at the inlet of the hydrocyclone, pulp thickening and air column pressure. Experimental studies were performed in the laboratory on a model of a standard industrial cylindrical-conical hydrocyclone HC360. The connection between the technological parameters of the hydrocyclone operation and the pressure in the air column has been studied. to establish possibilities of control of work of a hydrocyclone on pressure in an air column. The planning of the experiment in the laboratory on a hydrocyclone model was performed in the program Statgraphics Centurion XV.&#x0D; Experimental studies were performed for the optimal parameters of the angle and slit of the pneumatic regulator. The optimization criterion is chosen – the maximum effect of pulp thickening while minimizing local energy losses in the nozzle. In laboratory conditions, the change in pulp pressure and density at the inlet of the hydrocyclone over the entire operating range is simulated. The laboratory model of the hydrocyclone was made on a scale of M1:10. Flotation waste was used as pulp. Modeling of hydrocyclone operation as a part of water-sludge system at the concentrator is carried out. The density of the solid phase is 1500 kg/m3.&#x0D; The solids content at the inlet is 10 g/l. Samples were taken by volumetric measurement with a measuring vessel. A statistically significant relationship between the pressure in the air column of the hydrocyclone and the effect of pulp thickening in a standard cylindrical-conical hydrocyclone was established. The presence of the linear character of the dependence of the coefficient of thickening and pressure in the air column of the hydrocyclone with the pneumatic regulator is checked. The absence of a statistically significant effect of hydrocyclone supply pressure on the dependence of other selected factors was established.&#x0D; Experimental studies were carried out at the optimal design parameters of the pneumatic regulator according to the criteria of minimizing the loss of energy of air current in the nozzle and minimizing the volumetric flow of air.

Considering hydrocyclone operation for tailings dewatering purpose and its effects on product specifications of paste backfill operations

Tailings management is challenging and important task especially for the plants that are considering to utilize them. Cemented paste backfill (CPB) can be counted as one of them where the opportunities regarding to economy improvement exist. Within the CPB application, dewatering of the product is of crucial importance where thickeners are mostly preferred. However, alternative solutions should also be considered to improve the solid concentration, throughput and maybe the product specifications. The aim of this study was to improve the knowledge regarding to the use of dewatering cyclone in copper concentration plant. In this operation, the tailings are initially sent to thickener and then mixed with cement-water mixture prior to its use in the underground mining. Data collection aimed at testing of varied cyclone geometries to define the limits of the laboratory unit. Afterwards, the modelling studies were performed for a given geometry and scaling up was completed to suggest pilot scale unit. Initial studies were followed by the pilot scale trials where the product properties such as strength and viscosity were considered. As a result of the study, cyclone application was found to improve the strength of CPB material with reduced cement consumption and reduced viscosity in comparison to that of the thickening process.

Effects of Wall Roughness on the Separation Performance of Hydrocyclones under Different Inlet Conditions

Wall roughness is a crucial parameter in the manufacture and operation of hydrocyclones but has been underestimated. This study assesses the effects of wall roughness on the separation performance under different inlet conditions using a two-fluid model and an empirical wall roughness model that modify the logarithmic law of the wall. These models are proven to give good predictions for the in-house experiments on a ⌀150 mm hydrocyclone. The results indicate that small roughness is acceptable in use, whereas large roughness can significantly deteriorate the separation performance. The wall roughness mainly affects the pressure–kinetic energy conversion in the boundary layer by decreasing the tangential velocity and increasing the axial and radial velocities. All these changes further affect the air core diameter, the spatial distribution of particles, and finally, the separation results. The equal pressure condition can provide superior separation results with higher capacity than the equal flow rate condition but still cannot eliminate the adverse effects of wall roughness.

Linking separation sharpness with the characteristics of axial velocity wave zone in a hydrocyclone

Maximizing separation sharpness is critical for the design and operation of hydrocyclones but remains difficult to achieve. This work presents a numerical study on the relationship between separation performance and the characteristics of axial velocity wave zone to understand the reasons for the limited separation sharpness. The results showed that this zone is featured as an inherent transition region, with extensive secondary vortices formed between inner and outer spiral flows. The presence of this zone adversely affects the fluid-solid momentum transfer, causing prolonged residence time and accumulation of intermediate-sized particles. The separation sharpness shows a strong dependence on the characteristics of axial velocity wave zone, which are further controlled by geometric parameters. Increasing the symmetry of flow field and optimizing the spatial distribution of this zone can help increase the separation sharpness while its size shows little effect.

Efficient separation of precious metals from computer waste printed circuit boards by hydrocyclone and dilution-gravity methods

To fulfill the different aspects of green chemistry and to achieve full use of the secondary resources (waste printed circuit boards (WPCB)), the necessity of developing green methods for recovery of precious metals (Au, Pd, and Ag) is highly demanded. In this study, a novel environment-friendly physical separation approach; the combination of crushing, grinding, sieving as pretreatment steps alongside hydrocyclone and the dilution-gravity method (DGM) as the main final steps; is proposed. Inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (EDS) characterization methods were utilized to understand the effects of different separation steps applied in this research. The size and shape of grinded materials and the ones produced after hydrocyclone and DGM were evaluated using scanning electron microscopy. The results showed that the sieving step separated the highest gold fraction in the finer classification (<75 μm) while placed the copper (70 wt.%) into the coarser contents. The overflow to underflow outlet diameter ratio and inlet pressure was evaluated to determine the separation efficiency of a hydrocyclone effect of parameters. In the best-case scenario at 3 bar hydrocyclone operation pressure where the overflow to underflow outlet diameter (Do/Du) was 6.5, the highest metal fraction (87 wt.%) was achieved in the sink of the DGM. In this case, the total separation efficiency of gold, palladium, silver, and copper was 75%, 78%, 64%, 72%, respectively. Thus, this study demonstrates the feasibility of utilizing the sieving as mentioned above classification pretreatment steps followed by hydrocyclone and DGM methods as promising approaches for recovering precious metals from WPCBs that contain annually almost 50 million tons of e-waste.

Experimental investigation for R&D in sediment laden pico hydraulic francis turbine

The researches previously accomplished have been focused on design analysis, performance comparison and improvement of hydrocyclones for general applications and comprehensive results have been achieved. For the present research, an open loop experiment setup has been developed to study the feasibility of hydrocyclone separator as a pre-filtering device for sediment laden hydraulic turbine. The experimental setup for this study is designed primarily to investigate the effectiveness of hydrocyclone for high sediment period of turbine operation and consequent effect on turbine efficiency. The experimental analysis is designed to develop a general concept for operation of hydrocyclone in RoR hydro power projects. The results of the analysis showed that hydro cyclone separator is efficient in separating sediment particles of sizes as low as 45 μm. The analysis of separator at different position downstream from the intake has shown minimal effect on pressure drop but loss in discharge is comparatively visible with increased inlet head. The technical challenges like loss in efficiency and power output, turbine repair cost, turbine overhaul period can be mitigated. The future works for this study can be financial comparison of loss in power due to sediment erosion to use of hydrocyclone separator in hydraulic turbine working model.

УСТАНОВЛЕНИЕ ТЕХНОЛОГИЧЕСКИХ ЗАВИСИМОСТЕЙ РАБОТЫ КОНЦЕНТРАТОРА KC-CVD6 С ПОМОЩЬЮ МЕТОДА ГРУППОВОГО УЧЕТА АРГУМЕНТОВ

Актуальность исследования обусловлена получением новых знаний об оптимизации технологических параметров работы центробежных концентраторов, эксплуатируемых по технологии Knelson CVD, а именно: настройка частоты открытия клапанов и время, в течение которого клапаны остаются открытыми. Цель: статистический анализ результатов полупромышленных исследований применимости технологии Knelson CVD на различных продуктах фабрики с помощью метода группового учета аргументов для получения зависимостей между выходом концентра и настраиваемыми параметрами, позволяющими проводить предварительные расчеты по эффективности внедрения данной технологии на обогатительных предприятиях. Объекты: продукты, полученные в результате работы гидроциклонов, а также технологические параметры работы центробежных концентраторов. Методы: общие методы математической статистики, в частности методы регрессионного анализа, направленные на построение статистически значимых моделей, описывающих зависимость какой-либо переменной от множества регрессоров. Также, наряду с классическим аппаратом регрессионного анализа, применяется метод группового учета аргументов, основная идея которого заключается в построении множества моделей заданного класса и выборе среди них оптимальной. Результаты. Разработана эффективная методика обработки результатов тестов, проведенных на обогатительном оборудовании, базирующаяся на методе группового учета аргументов. На основании полученных данных построены статистически значимые модели, описывающие зависимость содержания в хвостах и концентратах по ценным компонентам от различных настраиваемых параметров оборудования, обоснована их эффективность, позволяющая применять данные модели в дальнейших исследованиях по применению CVD технологии. Продемонстрировано применение метода группового учета аргументов на примере построения полиномиальных регрессионных моделей, содержащих нелинейные комбинации регрессоров.

Classification performance of semi-inverted hydrocyclones

Researchers have reported in the past that inclined hydrocyclone operation can provide a lower water split to underflow and much coarser cut sizes. However, semi-inverted hydrocyclones (inclined higher than the horizontal position) have not been investigated in detail. This paper presents the results of a comprehensive study that was carried out at the Julius Kruttschnitt Mineral Research Centre (JKMRC) using a semi-inverted (SIV) hydrocyclone. A 250 mm hydrocyclone was tested with a modified cone. The modified cone extended the operational range of the hydrocyclone. The SIV hydrocyclone was tested at different inclinations and operating feed pressure using three different slurry feeds. A significant reduction in the water split (WS) to coarse was achieved at semi-inverted positions. WS values of 3–5% at 135° inclination were achieved. The change in WS did not influence the sharpness of separation (α). Stable operation and sharpness of separation were achieved, despite the appearance of roping-like underflow discharge in semi-inverted operation.

Prevention of Hydrocyclone Choking Through Detection of Sub-Hz Frequency Shift of Vibration Signal

Hydrocyclones are extensively used in mineral processing and other industries to separate heavy and coarse particles from light and fine particles, respectively. Due to variation in the density of feed which contains water and particles, the hydrocyclone gets choked during continuous operation. Clearing the choking is a time-consuming and expensive affair which requires shutdown of the hydrocyclone. To prevent this, the hydrocyclone operation needs to be monitored continuously to alarm well before choking happens. A vibration sensing and analysis-based method is proposed in this paper to predict the choking condition well in advance. Vibration signals were collected by varying the solid percentage in the feed input to create choking condition. Vibration signal was processed using Fourier transform to observe the variations under different feed concentrations. It was observed that higher slurry density in the feed input leads to choking of hydrocyclone. Vibration signal which is captured at the apex of the hydrocyclone is recommended here to be used to monitor the operational conditions of the hydrocyclone. After analysis of the captured vibration signals in frequency domain, it was found that there is shift of specific frequencies due to an increase in slurry density. By monitoring the shift in peak frequencies in those frequency ranges, the choking can be detected and cleared well in advance to avoid a shutdown of hydrocyclone.

A sustainability performance assessment framework for palm oil mills

The palm oil industry has had to undergo rapid development in order to cope with the increasing demand from consumers year by year. The palm oil industry is receiving criticism from various parties on the issue of sustainability. This paper presents the development of a Palm Oil Mill Sustainability Index that enables millers to assess the sustainability performance of palm oil mills against benchmarks, and to differentiate between the performance of each mill. The assessment was performed via the adoption of a Proximity-to-Target approach that measures the current sustainability performance of the industry relative to policy targets. The industry's comparable performance was observed in terms of sustainability and indicators through a graphical method. The resulting Palm Oil Mill Sustainability Index scores were translated into a five-point rating system to describe the sustainability performance levels for different mills i.e. excellent, good, fair, poor, and very poor. Based on the Palm Oil Mill Sustainability Index scores and rating system, weak performance indicators were identified, for example, excessive use of water consumption due to inappropriate operation of hydrocyclones. By identifying the weak performance indicators, practical recommendations and measures for improvement can be proposed and the Palm Oil Mill Sustainability Index scores recalculated to evaluate the effectiveness of the proposed sustainability performance strategy. Selected palm oil mills in Malaysia were used as a case study to demonstrate the applicability of the framework. The results provide empirical evidence to support a decision-support-system for enhancing palm oil mill sustainability performance, so as to achieve a balance between environmental, economic, and social aspects in the palm oil mill sector.

Assessment of hydrocyclone operation in gravity induced stirred mill circuits

The performance data of hydrocyclones in circuits containing a gravity induced mill (hereafter referred to as a stirred mill) were evaluated to understand their performance in the circuits and the current operational practices. There are many studies conducted to understand and evaluate the hydrocyclone performances in the semi-autogenous mill (SAG) and ball mill circuits. The literature on hydrocyclone operation in stirred milling circuits is still limited. A database consisting of various hydrocyclone sizes, operating conditions, classification duties, and commodities was developed based on extensive circuit surveys. The database was used to evaluate the hydrocyclone performance. Among the key operational issues observed were poor circuit control strategies, improper hydrocyclone sizing and operation in the roping condition. Analysis of long-term operational data indicated that hydrocyclone feed solid density is an essential operating variable that needs to be controlled to maintain the cut size. An increase in hydrocyclone feed density leads to an increase in cut size. Almost 50% of the hydrocyclones (in the database) were operating in the roping condition. Besides the hydrocyclone feed solid density, high amounts of fine particles (−25μm) in the hydrocyclone feed also caused the roping condition. Further research is required to operate the hydrocyclone in a spraying condition when the feed has high solid-density and a high content of fines. Plitt’s cut size model was fitted to the data set to evaluate its capability to be used in the stirred mill’s hydrocyclone. The analysis shows the Plitt’s model can predict the cut size when the hydrocyclone is in spraying mode. This result indicates that Plitt’s model can be used for the regrind duty hydrocyclones. An empirical model was developed relating the hydrocyclone feed density and the Plitt onset roping hydrocyclone underflow density. This model can be used to predict the roping condition. Finally, the impact of hydrocyclone performance on circuit performance was compared through the size specific energy of the mill. High size specific energy values were observed when the hydrocyclone is operating in the roping condition. These findings are based on the real operating condition, and it shows the importance of operating the hydrocyclone optimally to achieve overall circuit efficiency.

Sensitivity of DynaWhirlpool hydrocyclone operation to applied back-pressure

The two-phase, air–water flow pattern in a DynaWhirlpool centrifugal separator is investigated using time-dependent, three-dimensional numerical simulation. The air–water interface is captured by the Volume-Of-Fluid approach, while the unresolved turbulence fluctuations are modeled via a second-order differential-stress turbulence model. Among the different operating variables, the back-pressure at the sink outlet affects significantly the flow within the cyclone. The modifications experienced by the flow field as the back-pressure is increased are documented and interpreted. The variation of relevant operating variables is also reported, as the split ratio and the Euler number characterizing the device. It is verified that for large values of the back-pressure the water flow through the sink is hindered and the air core disappears. The flow pattern is moderately altered when the cyclone is fed with a non-Newtonian fluid with the same viscosity as a real water/magnetite dense medium.