Search Results (34)

In this article, the results of full-scale experiments on the addition of a sodium sulfide to the ${\mathrm{CaCO}}_3$ slurry circuit in a wet flue gas desulfurization (WFGD) plant are presented. Tests are performed on two comparable WFGD installations (spray tower, 4 spraying levels and two stage gypsum de-watering by hydrocyclones and vacuum belt filter) which allows the investigation of the influence of lignite composition (lignite mined in Poland and the Czech Republic are compared) on the reduction in mercury emission. Additionally, the efficiency of precipitation of metals from the slurry (Hg, Zn, Pb, Cd, Cr, Cu, Ni, Fe, Se, and Mn) is investigated as the result of sulfide addition. For both objects, mercury re-emission from absorber occurs (the concentration of mercury in the chimney is higher than that before the WFGD absorber) and the sulfide addition to WFGD slurry stops this phenomenon. The addition of sulfide works effectively (mercury removal efficiency from flue gas reaches up to 88% for Polish tests and up to 87% for Czech Republic tests). For the tests in the Poland power plant, all of measured metals are precipitated from the slurry (precipitation of metals efficiency varied from 2% for zinc to 88% for mercury), but in the case of the test in the power plant in the Czech Republic, there is no effect on manganese, iron, and lead (precipitation of metals efficiency varied from 6.5% for copper to 86% for mercury). The addition of sulfide works effectively for lignite mined in Polish and Czech power plants under the conditions of similar WFGD installations. Full article

Plastic pollution has been a global concern. Microplastics are often referred to as plastic particulates whose sizes are within the range of 1 μm to 5 mm. To cost-effectively capture these tiny microplastics from open environments, such as from the air or aquatic/marine systems, is far from trivial. Not only is some innovative capturing technology demanded, but some online monitoring solutions are often requested as well to assess the capturing effectiveness and efficiency, as well as provide some feedback information to the control system to adapt to varying operating conditions. Inspired by the de-oiling treatment of the produced water in offshore oil & gas production, this paper explores the potential to apply the hydrocyclone technology to cost-effectively handle the water-borne microplastics, and its effectiveness is demonstrated based on reliably calibrated online microscopy measurements subject to artificial polyethylene particulates added to the water stream. The experimental work is carried out using a commercial de-oiling hydrocyclone system and a set of commercial optical microscopy sensors. A statistic-based calibration method is firstly proposed for the deployed microscopy sensors to select the best calibration parameters. Afterwards these sensors are installed at the inlet and water-outlet of the hydrocyclone system via a side-stream sampling mechanism to assess this system’s (microplastics) separation efficiency subject to dynamical operating conditions, which are mimicked by manipulating its underflow and overflow control valves via PI-controlled loops. The separation efficiencies are calculated based on these volume concentration measurements and compared between the case with (statistically) optimal calibration parameters and the case with a set of non-optimal parameters. The best separation efficiency of 87.76% under the optimal calibration parameters is observed under a specific operating condition. The obtained result shows a promising potential to use these separation and sensing systems to cost-effectively handle aquatic microplastics collection, though it also indicates that a further higher efficiency could be achieved by some (microplastics) dedicated cyclone design combined with a dedicated process control system, and this is one part of our ongoing research work. Full article

Roping is a hydrocyclone failure mode that reduces separation efficiency, negatively impacting both the comminution circuit and downstream flotation processes. Therefore, detection of roping as early as possible is crucial in maintaining the normal performance of physical separation and linked processes. Most importantly, instead of detecting roping after it happens, could roping be predicted even before it arises? This review examines various detection methods, including mechanical, tomography, vibration, acoustic, and image processing, highlighting their cost and ability to monitor parameters like air core size, spray angle, and solid concentration. While most current methods detect roping only after it happens, predictive approaches could save time and costs. A promising solution combines pressure and vibration sensing with advanced signal processing, showing early potential to transform roping prediction and improve operational efficiency. This review highlights research gaps across various methods, underscores the importance of developing predictive capabilities for hydrocyclone operations, and outlines the essential conditions and future priorities for achieving roping prediction. Full article

A conventional hydrocyclones is a versatile equipment with a high processing capacity and low maintenance cost. Currently, several studies aim to alter the typical structure of the conventional hydrocyclone in order to modify its performance and purpose. For this, filtering hydrocyclones have emerged, where a porous membrane replaces the conic or cylindrical wall. During the operation of this equipment, in addition to the traditionally observed streams (feed, underflow, and overflow), there is a liquid stream resulting from the filtration process, commonly referred to as filtrate. This work proposes to numerically investigate the solid particle/liquid water separation process in a filtering hydrocyclone using the commercial software Ansys CFX^® 15.0. The proposed mathematical model for the study considers three-dimensional, steady state and turbulent flow, using the Eulerian–Eulerian approach and the Shear Stress Transport (SST) turbulence model. This study presents and analyzes the volume fraction, velocity, and pressure fields, along with flowlines and velocity profiles. The results indicate that the proposed model effectively captures the fluid dynamic behavior within the filtering hydrocyclone, highlighting higher pressures near the porous membrane and a higher concentration of solid particles in the conical region, with water being more concentrated in the cylindrical part of the hydrocyclone. Additionally, the findings show that the volumetric flow rate of the filtrate significantly influences the internal flow dynamics, with conventional hydrocyclones demonstrating higher pressure gradients compared to the proposed filtering hydrocyclone. Full article

The treatment of produced water is a major challenge faced by oil and gas industries worldwide. As a result of the increase in industrial activities, the generation of produced water has increased significantly. The most commonly used method for produced water oil–water separation is de-oiling hydrocyclone technology due to its simple construction, compact design, easy maintenance, and high efficiency. A wide breadth of scientific research studies has been carried out on performance evaluation, design optimisation, geometric parametrisation, external interventions, etc., to enhance the performance of hydrocyclones. These studies mostly rely on either experimental data obtained from the field, in laboratories under a controlled environment, or the application of numerical techniques for oil-in-water separation. Considering the extensive research studies published on hydrocyclone technology, this study aims to provide a comprehensive review of recent technological advancements in hydrocyclone technology in order to identify key areas where scientific research efforts should be concentrated. This will help make well-informed decisions for strategic investments in this wide area of research. Furthermore, it will widen the scope of applicability of hydrocyclones in the industrial sector. Full article

This article presents the results of cyanide leaching of gold-containing concentrate using the trichlorocyanuric acid (TCCA) oxidizer. Gold-containing concentrate was obtained from a gold tailings sample from a gold recovery factory (GRF) in one of the deposits of Kazakhstan that have not previously been studied for concentrability. According to X-ray phase analysis and energy dispersive spectrometry (DSM) data, the main compounds in the tailings sample under study are pyrite FeS₂, quartz SiO₂, calcite CaCO₃, albite NaAlSi₃O₈, muscovite KAl₂Si₃AlO₁₀(OH)₈, dolomite CaMg(CO₃)₂, and oxidized iron compounds. Microscopic studies of the concentrate have established the presence of ultrafine gold with sizes from Au 0.9 to 10.2 μm in pyrite. Obtaining the gold-containing concentrate with a gold content of 15.95 g/t is possible according to the enrichment scheme, which includes centrifugal separation, classification according to the fineness class −0.05 mm, additional grinding of hydrocyclone sands to a fineness of 90.0–95.0% of the class finer than 0.050 mm, and control centrifugal separation. Since pyrite in technogenic raw materials is the main gold-containing mineral, this paper presents studies on the oxidizability of pyrite with the TCCA oxidizer. The results of studies on the oxidation of pyrite using the TCCA oxidizer show the products of its hydrolysis oxidize pyrite with the formation of various iron compounds on its surface. Pretreatment of gold-containing concentrate with oxidizer TCCA for 3 h before the cyanidation process (20 h) allows for an increase in the recovery of gold in the solution by 5.8%. Full article

Hydrocyclones can be used to concentrate the entrained sands in sewage and alleviate the clogging and erosion of the drainage network, but in practical application, there are problems such as low concentrations of underflow and a high content of fine particles, which cause a significant load on the subsequent sand dewatering and recycling. This paper designs five spigot structures of hydrocyclones and investigates the separation performance by numerical simulation, aiming to improve the applicability of hydrocyclones in the sewage treatment process by optimizing the spigot structure. The research results show that a large cone spigot delays the external downward swirling flow and reduces fine particle content in the underflow, but its effective separation space is reduced, and the turbulence in the cone section area is more intensive, which influences the separation accuracy. An elongated spigot has a reduced underflow water distribution; fine particles are more enriched in the internal swirling flow, and the underflow recoveries of 1 μm and 5 μm particles drop by 2.34% and 2.31%. The spigot structure affects the downward fluid and air intake states; complicated spigot structures contribute to increasing the resistance of particle discharge through underflow, alleviating fine particle misplacement. Full article

A semi-industrial scale hydrocyclone with a 250 mm internal diameter was used to concentrate medium-grade celestine ore (75%–85% celestine) from the Montevive deposit of Granada (Spain) using a dense ferrosilicon (FeSi) medium. For this purpose, a Box–Behnken factorial design (BBD) was carried out, with the response variable being the Sr concentration measured by X-ray fluorescence (XRF), as well as the concentration of celestine measured by X-ray diffraction (XRD) of the mineral collected from the under (sunk) stream of the hydrocyclone. The experimental factors to be optimised were the density of the medium in the mixing tank (water, FeSi, and feed mineral) varying from 2.7 to 2.9 kg/L, the hydrocyclone inlet pressure from 0.8 to 1.2 bar, and the hydrocyclone inclination (from 15° to 25° from the horizontal). The range of densities of the dense medium to be tested was determined from previous sink–float experiments using medium-grade ore, in which the distribution of mineral phases with different particle size fractions was determined. To evaluate the separation behaviour, the following parameters were considered: the enrichment ratio (E), the tailings discarding ratio (R), and the mineral processing recovery (ε). From the factorial design and the response surface, the optimum parameters maximising celestine concentration in the under stream (78%), were determined. These optimised parameters were: a density of 2.75 kg/L for the dense medium, an inlet pressure of 1.05 bar, and a hydrocyclone inclination varying from 18° to 20°. Under these conditions, a 94% recovery of celestine (68% Sr) can be achieved. These results show that medium-grade celestine ore, accumulated in mine tailings dumps, can be effectively concentrated using DMS hydrocyclones and that the operating parameters can be optimised using a factorial experiment design. This study can contribute to reducing overexploitation of strategic mineral resources, avoiding blasting and environmentally damaging clearing, by applying a simple and sustainable technique. Full article

Weathered granite contains a high concentration of feldspar, quartz, and kaolin. However, while it becomes rich in clay due to strong physical weathering, the granite minerals that are not fully weathered are still very hard, which makes the grinding process more difficult and limits its use. This study proposes a multi-step process involving grinding, desliming, and flotation to address this issue. The study determines the appropriate grinding time and power index for the original ore, as well as the optimal desliming method using a hydrocyclone. To remove iron-containing impurities like mica, a combination of NaOL/BHA/A CO collectors is used for the reverse rough flotation of quartz. Additionally, a combination of DDA/SDS collectors is employed to separate quartz and feldspar through flotation, resulting in a quartz product with a silicon dioxide content of 99.51%. The objective of efficiently recycling feldspar, quartz, and kaolin from weathered granite is accomplished. Additionally, the inclusion of intermediate mineral components as by-products of feldspar and raw materials for aerated bricks is introduced, resulting in the complete utilization of all components. This innovative approach ensures a clean and environmentally friendly process, eliminating the need for solid waste disposal. Full article

The tubular dynamic hydrocyclone (TDH) holds great potential for the pre-deoiling of offshore oil platforms. However, the shear and turbulence in the flow field can cause the oil droplets, the dispersed phase in water, to break up when the swirling flow is produced by the swirler. A design method is proposed for the low-shear rotary swirler (LSRS) of TDH, the aim of which is to reduce the shear force and local turbulence during the fluid forming swirling flow. The blade setting angle of the LSRS is calculated based on the relative velocity vector between the fluid and the swirler. The distribution characteristics of the tangential velocity and turbulence in the TDH with LSRS are simulated by Computational Fluid Dynamics (CFD). The maximum stable droplet diameter is analyzed. The results show that the shear stress and turbulence energy dissipation rates are reduced by 74.6% and 68.5%, respectively, and that the stable droplet diameter is increased by more than 60%, compared to the conventional rotating swirler. In addition, a TDH prototype with LSRS was tested in an offshore oil field by continuous operation for more than 36 h. The average separation efficiency was 83%, and the average underflow oil concentration was 27 mg/L. The research also found that the drastic changes in the tangential velocity along the axial direction were critical to shear. Moreover, the results make up for the deficiency of the spatial variation of the tangential velocity in the dynamic cyclone separator. Full article

To reduce the environmental impact of offshore oil and gas, the hydrocarbon discharge regulations tend to become more stringent. One way to reduce the oil discharge is to improve the control systems by introducing new oil-in-water (OiW) sensing technologies and advanced control. De-oiling hydrocyclones are commonly used in offshore facilities for produced water treatment (PWT), but obtaining valid control-oriented models of hydrocyclones has proven challenging. Existing control-oriented models are often based on droplet trajectory analysis. While it has been demonstrated that these models can fit steady-state separation efficiency data, the dynamics of these models have either not been validated experimentally or only describe part of the dynamics. In addition to the inlet OiW concentration, they require the droplet size distribution to be measured, which complicates model validation as well as implementation. This work presents an approach to obtain validated nonlinear models of the discharge concentration, separation efficiency, and discharge rate, which do not require the droplet size distribution to be measured. An exhaustive search approach is used to identify control-oriented polynomial-type Hammerstein–Wiener (HW) models of de-oiling hydrocyclones based on concentration measurements from online OiW monitors. To demonstrate the effectiveness of this modeling approach, a PI controller is designed using the Skogestad internal model control (SIMC) tuning rules to control the discharge OiW concentration directly. The identification experiment emulates an offshore PWT system with installed OiW monitors, which is realistic with the legislative incentive to include online OiW discharge measurements. The proposed approach could enable the application of OiW-based control on existing offshore PWT facilities, resulting in improved de-oiling performance and reduced oil discharge. Full article

The particle classification in the enhanced gravity field generated by the Knelson concentrator was studied in this paper. Three main test parameters, namely rotation speed, backwash water pressure, and solid mass percentage, that affected the classification performance of the Knelson concentrator for the classification tests of quartz and synthetic ore, which consisted of quartz and magnetite, were investigated. The yield of quartz concentrate increased with the rotation speed and decreased with the solid mass percentage and backwash water pressure. A lower backwash water pressure and solid mass percentage could improve the classification efficiency. The classification performance of the Knelson concentrator was comparable to that of the traditional hydrocyclone, with a classification efficiency of 76.84% and cut size of 49 μm when the solid mass percentage was 16.67%, the backwash water pressure was 50 kPa, and the rotation speed was 3600 rpm. The classification performance of quartz in synthetic ore tests was inferior to the single quartz tests, and the magnetite showed a better classification efficiency than the quartz with the same combination of test parameters. This study revealed the classification performance in the separation process of the Knelson concentrator in detail, which was beneficial for clarifying the migration rule of fine-grained minerals in the enhanced gravity field. Full article

The separation methods of palygorskite can be divided into dry separation and wet separation. For wet separation, which is more efficient, the centrifuge is the commonly used method but is characterized as having a high cost. It remains a challenge to separate ultra-fine palygorskite with an economical method. This work tried to separate palygorskite using a hydrocyclone with two separation stages. Orthogonal experiments are designed to investigate the influence of feed concentration, feeding pressure, and underflow port diameter on separation performance. The element content, mineral composition, and particle size distribution of the separation products are analyzed, respectively, by XRD, XRF, and laser particle sizers. The apparent viscosity of palygorskite pulp is characterized by a rotational rheometer. The purity of the feed and palygorskite concentrate is measured using an internal standard method. The results show that the purity of palygorskite increased from 45.1% to 64.2%, with a recovery of 95.9%. Full article

A pilot hydrocyclone plant was used to concentrate medium-grade celestine ore (67% celestine) from the Montevive deposit in Granada (Spain) by using a dense media concentration (DMS) process. To optimize the concentration process, several types of heavy minerals (coarse, fine C40 ferrosilicon and/or magnetite) were used to prepare a dense media with a constant density of 3.0 kg/L. Then, the dense media (loaded with run-of-mine celestine mineral) was fed into the hydrocyclone system. The mineral was then separated into two streams, the first containing the mineral fractions that float (over stream) and the second containing fractions that sink (under stream) in the dense media. Next, the heavy minerals (ferrosilicon and/or magnetite) were recovered from the dense media using magnetic separation. The celestine mineral recovered from each stream was divided into two fractions with particles size above or below 250 μm to study the effect of the mineral particle size on the separation process. Their mineral composition was quantified by X-ray diffraction (XRD) using the Rietveld method. The celestine is preferentially concentrated in the under stream in the mineral fraction with particles larger than 250 μm (up to 90% celestine). The optimum results (highest % of celestine) were obtained after desliming and using the ferrosilicon C40 medium, which has the smallest particle size (<40 μm) of all media used. The results of this study show that medium-grade celestine mineral accumulated in the mine tailings can be efficiently concentrated using a DMS process, which could help in making mine operations more sustainable and eco-friendlier. Full article

The current centrifugal concentrators do not continuously concentrate heavy minerals of large mass weight—for example, in the processing of iron oxides. A cyclone centrifugal separator is a new type of beneficiation equipment that has been developed on the basis of the principles of centrifugal separation and hydrocyclones. In this study, a cyclone centrifugal separator was used for the beneficiation of a hematite–quartz mixture, and the separation effect under different operating conditions was analyzed. The results showed that various factors, such as the feeding concentration, the feeding pressure, and the number of fluidization holes in the separation cone, had a significant influence on the separation performance of the cyclone centrifugal separator. The single-factor separation test results showed that the appropriate operating conditions were a feeding concentration of 10%, a feeding pressure of 120 kPa, a 40-hole separation cone, a settling port pressure of 70 kPa, and an overflow port pressure of 50 kPa. The results of the open circuit separation test that was designed on the basis of the single-factor experiment showed that the concentrate grade of Fe in the hematite–quartz mixture, with 44.12% Fe, was 54.42% after beneficiation, indicating better beneficiation separation effects. This study provides a new approach for the beneficiation of a large number of difficult-to-select hematite ores in China, and can provide a reference for the further expansion and application of the cyclone centrifugal separator in the field of mineral processing. Full article