Hydrocyclone Underflow Research Articles

Study on classification separation of low-rank coal macerals using hydrocyclone and enhanced gravity separator

ABSTRACT Efficient enrichment of macerals improves the liquefaction efficiency of low-rank coal. The paper studied the characteristics of Shendong low-rank coal, including proximate and ultimate analyses, size and density compositions, and petrographic analysis, as well as the migration regularity of narrow particle size of low-rank coal macerals in the enhanced gravity field. On this basis, a novel classification separation process for low-rank coal macerals using Krebs hydrocyclone and enhanced gravity separator was proposed. The classification size was determined to be 0.074 mm and Krebs hydrocyclone achieved a satisfactory classification effect with a classification efficiency of 84.72%. Based on the enhanced gravity separation results of macerals from hydrocyclone underflow and overflow, the optimal sorting solutions for underflow and overflow were obtained through response surface analysis, respectively. Through the novel classification separation process, the vitrinite content of clean coal has been increased from 46.60% to 61.33% with an outstanding recovery of 77.40%. The novel classification separation process using hydrocyclone and enhanced gravity separator develops an excellent enrichment effect for low-rank coal macerals, which also provides a prospective approach for the cleaner utilization of low-rank coal.

The effect of grinding circuit efficiency on the grade and recovery of copper and molybdenum concentrates

ABSTRACT The efficiency of grinding and flotation process in copper-molybdenum processing circuit, largely affected by performance of thickeners and hydrocyclones devices. The goal of this paper is to investigate the effect of the rate-limiting factors on the performance of these devices and consequently on grinding and separation efficiency of the molybdenum processing circuit. So, a full process mineralogical study have been carried out on outputs of thickeners and hydrocyclone of the molybdenite flotation circuit. According to the results, coarse-grained fractions (>50 μm) of the planar molybdenite will not necessarily be recovered by thickener and hydrocyclones. This is especially true for hydrocyclones when the inlet-load rate is high, i.e., the erroneous discharge of planar molybdenite particles from the overflow of hydrocyclone, as well as their floatability in the thickener overflow, can be attributed to the effect of particle shape and size. This issue harms the grade and recovery of flotation due to the increase in the amount of circulating load (regrinding) and consequently the generation of fine particles (<10 μm) in the hydrocyclone-milling circuit. On the other hand, the almost spherical particles of copper minerals, as well as the nonplanar molybdenite fine-grained particles, are easily removed from the hydrocyclone underflow or settled in thickeners. The introduction of copper mineral particles into molybdenum concentrate and vice versa has reduced the quality of the produced concentrate and undesirable flotation performance.

Energy balance formation of sub-eutectoide fayalita at high pressures in particle separators

This article presents an approach to the problem of ceramic types adhesion, applying energy and matter balance to the established control volume (cyclone) with the use of mathematical formulas that are interrelated to develop mathematical calculations and establish a new mathematical model The first results are obtained by operating the energy balance considering the collision of particles, using the principle of conservation of energy, the first law of thermodynamics, in order to obtain information that allows describing the phenomena of thermoplasticity and creep, in the formation of adhesions, from a physicochemical and kinetic point of view, which will serve as the basis for understanding their effect. As a result, an energy value of 660 kJ / mol was obtained, sufficient energy to start the transformation of the solid particles to a state of thermo-flow that allows the adhesion phenomenon to be started.&#x0D; Keywords: Adhesion, energy balance, cyclones, elutriation, eutectoid, fayalite, thermoplasticity.&#x0D; References&#x0D; [1]O. Bustamante. “Dissipation of mechanical energy in the discharge of a hydrocyclone”. (Dyna, Ed.) The network of Scientific Journals of Latin America, the Caribbean, Spain, and Portugal, vol. 80 (181), Pages 136-143, 2013.&#x0D; [2]K.Petersen, P.Aldrich, and D.Van.,”Hydrocyclone underflow monitoring using image processing methods. Minerals Engineering”, pp. 301-315,1996.&#x0D; [3]M. Farghaly,” Controlled Wash Water Injection to the hydrocyclone underflow” [Ph.D. Thesis]. Erlangen, FAU, 2009.&#x0D; [4]M, Schneider, and T. Neesse. “Overflow-control system for a hydrocyclone battery. Int. J. Miner. Process". 74, pp. 339 – 343, 2004.&#x0D; [5]J.Bergström., “Flow field and fiber fractionation studies in hydro cyclones” [Ph.D. Thesis] Stockholm, Sweden, Royal Institute of Technology, 2006.&#x0D; [6]C, Liu, L. Wang, and Q. Lui., “Investigation of energy loss mechanisms in cyclone separators”. Chemical Engineering Technology 28, pp. 1182-1190, 2005.&#x0D; [7]O.Dam. &amp; E.Jeffes.,.”Model for detailed assessment of chemical composition of reduced iron ores from single measurement”. Ironmaking and Steelmaking, 1987.&#x0D; [8]E. Ringdalen., “Softening and melting of SiO2 an important parameter for reactions with quartz in Si production” pp 43-44, 2016.

Operational state detection in hydrocyclones with convolutional neural networks and transfer learning

In the mineral processing industries, the performance of hydrocyclones used in solids classification tasks influences the efficiency of downstream processing. Typical operation involves a fan shaped underflow profile, while undesirable roping and underflow blockage conditions result in excessive coarse particles in the overflow and have visually different underflow characteristics. Different approaches were investigated previously as potential sensing options for undesirable state detection, and while some have been commercialised, they currently have not found widespread implementation in the industry. Analysis of hydrocyclone underflow by use of image analysis has been one method investigated, in which it has been shown that meaningful features can be extracted for operational state detection.Deep convolutional neural networks have recently led to significant advances in computer vision tasks. In addition, the use of transfer learning making it possible to leverage this improved performance on smaller datasets. Video frames of the underflow of a laboratory hydrocyclone were used to produce a three-state (fan/rope/blocked) classifier, via transfer learning with a pretrained convolutional neural network feature extractor, which was able to produce meaningful state detection with the ability to handle considerable noise in the images.A dual state (fan/rope) classifier was also developed using largely industrial hydrocyclone underflow video frames, again via transfer learning with a pretrained convolutional neural network with both support vector machine and neural network based classification investigated. This study demonstrates the robust ability of deep convolutional neural networks to extract meaningful features from hydrocyclone underflow images without requiring significant image preprocessing. This is a major advantage over previous methods that rely on engineered features, and which may be more susceptible to changing environmental conditions during operation.

On the Conditions of Clogging in a Hydrocyclone

Experimental data on the flow boundaries of a barite suspension depending on its concentration and volume flow rate for a 10 mm high-pressure hydrocyclone were presented. Computer simulation of phase separation in the high-pressure hydrocyclone was performed for a concentrated suspension. Qualitative agreement between the results of numerical modeling and experiment on the conditions of clogging of the hydrocyclone underflow was obtained.

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.

An experimental investigation on hydrocyclone underflow pumping

The efficiency of a hydrocyclone is highly affected by the inlet flow conditions. Any fluctuation in the feed flow rate or feed solid concentration directly changes the separation performance. The underflow is typically adjusted to overcome the variable conditions of the feed flow, thereby delivering desired performance. A pump in the underflow allows active control of the hydrocyclone separation performance through either providing back pressure or by pump suction.The effects of underflow pumping at different inlet conditions are investigated experimentally. The ratio of the absolute underflow pressure to the overflow pressure is defined as pressure ratio P* and is used to compare the results. The pressure ratio resulting from underflow pumping has a similar effect in hydrocyclones as changing the underflow pipe size. For instance, increasing the pressure ratio (less pumping in the underflow) is similar to decreasing the underflow pipe diameter. The operating parameters of flow ratio Rf and inlet solid volume concentration c are found to have significant effect on pressure ratio. A nonlinear model for predicting pressure ratio is found to be P*=Rf−0.2689exp(−0.0267c) and has a maximum uncertainty of ±13% for the conditions tested. This prediction could be useful for controlling the underflow to maintain the desired hydrocyclone performance under varying inlet conditions.

Recovery of Iron Values from Iron Ore Slimes of Donimalai Tailing Dam

During production of calibrated (sized) ore, more than 50 % of the generated fines and rejects (Slimes) cannot be directly utilised in iron making due to its unfavourable granulometry, low iron content, high alumina and silica content. Approximately 10–20 % of the process plant input is discarded as slimes into slime ponds/tailing dams. Tailing dams are now considered as a threat due to hazardous nature and acute shortage of land for storing. More over these slimes also pose threat to the environment. Recovery of iron values from slimes results in economic benefit by utilisation of waste as a resource and minimizes the land requirement, surface degradation, ground water pollution, destruction of forests. These slimes after beneficiation are agglomerated (Pelletisation) and can be used as burden for the blast furnace. This research work presents the route for beneficiation of slimes by removing gangue in the slimes to an acceptable level to produce hot metal through blast furnace route. Research has been carried out effectively and efficiently to utilise the iron ore slimes from the slime ponds of Donimalai iron ore mine. The slime sample from tailing pond of Donimalai iron ore mine was collected and transported to R&D Centre, NMDC Limited, Hyderabad. The ‘as received’ slime sample assayed 49.40 % Fe, 13.51 % SiO2, 8.44 % Al2O3, 5.16 % loss on ignition and all other trace elements were within the critical limits. The ‘as received’ sample contains around 7 % moisture. It has a bulk density of 1.74 t/m3 and specific gravity of 3.7. Screen assay analysis was carried out with the ‘as received’ sample. Optimisation studies were carried out for desliming by using hydro-cyclone. Hydro-cyclone underflow was subjected to magnetic separation. It is possible to produce a concentrate which assayed 65.93 % Fe, 1.45 % SiO2, 1.94 % Al2O3 and 1.56 % loss on ignition with a yield of 45.18 % with a recovery of 60 % iron values.

Preconcentration strategies in the processing of nickel laterite ores part 3: Flotation testing

The preconcentration of nickel (Ni) laterite ores ahead of Ni recovery by hydrometallurgical processing makes good economic sense. Since Ni-bearing minerals are often finely disseminated through laterite ores, liberation of minerals either high and/or low in Ni content is a prerequisite prior to any form of separation process. It is the purpose of this paper to investigate the use of flotation to generate products either high or low in Ni-bearing minerals from a sample of Ni laterite with the generic description of “siliceous goethitic”. Previous attempts showed that upgrading of Ni laterites has only been conducted in laboratory or pilot plant scale, not adopted commercially. A number of feed preparation techniques ahead of flotation were attempted at laboratory scale on a sample of Ni laterite containing predominantly goethite and quartz. Flotation tests even on closely sized particles (38–75μm) failed to yield significant Ni upgrades using the reagents tested in this study, based on those used commercially for processing iron oxide ores. The best result was an increase in Ni content from 1.0% to 1.4% at a Ni recovery of 43%. This was obtained using 400g/t of an amine collector and 300g/t of starch at pH 10 on a sample of hydrocyclone underflow. This paper was designed to provide some lessons learnt for future researchers from laboratory flotation testing of a complex Ni laterite ore.

The use of continuous centrifugal gravity concentration in grinding circuit. Modified approach for improved metallurgical performance and reduced grinding requirements

The use of centrifugal gravity concentration in the closed-grinding circuit of a gold-containing massive sulphide ore was tested on classifier underflow and overflow. A continuous Knelson CVD6 was retrofitted to the hydrocyclone underflow for recovery of Au and Pb at a coarser feed size. The objective of treatment of overflow was recovering unliberated Au prior to flotation. The tests were performed in actual operating conditions at Nyrstar's Myra Falls Mine. The results of the tests on the cyclone underflow revealed that both liberated and unliberated Au and Pb were recovered by the Centrifugal Variable Discharge (CVD) concentrator. Concentrate grades <60g/Mg Au were attainable at a more than 20% recovery. This application also allowed early and increased Pb recovery before it became gravity unrecoverable by over-grinding. Other benefits included capturing middlings for regrinding as well as potential coarser grinding and increase in mill throughput. A coarse grind also corresponds to a reduction in deformation of Au-particles, and is beneficial for increased Au recovery in downstream processing. Treatment of cyclone overflow by the CVD also provided favourable results. The outcomes included capturing unliberated gold prior to flotation and potentially reducing pumping requirements and reagent consumption. A comparison of the metallurgical performances showed that CVD application on classifier underflow was more effective. The CVD was capable of recovering unliberated gold in sulphides and performed better at a coarser particle size. Therefore, when used with the grinding circuit, a coarser grind can be applied and the CVD could be used to reject gangue at a coarser size.

Scenario-Based Multi-Objective Genetic Algorithm Optimization of Closed Ball-Milling Circuit of Esfordi Phosphate Plant

The main goal of this article is to demonstrate an approach based on integration of process simulation and Multi-Objective Genetic Algorithm (MOGA) concepts to solve a real grinding circuit optimization problem by finding the best operating condition under which process objectives can be achieved. Esfordi phosphate plant is located near city of Bafgh at Yazd province of Iran and produces 5 Mt of phosphate annually. The fine particles (nearly −20 µm) in hydrocyclone underflow which contain a high grade of iron are subjected to over grinding. In addition to electrical energy loss, this causes problems in the downstream process, i.e., flotation stage. The main goals of this study were to solve this problem by adjusting operating condition so that (a) hydrocyclone overflow particle size can be increased from 94.2 µm to 100 µm and (b) increase hydrocyclone underflow particle size from 205 to 500 µm. The second process objective will decrease fine particles in hydrocyclone underflow stream. First, plant sampling campaigns were carried out to calibrate ball mill and hydrocyclone models to be used for performing simulation trials. Then, full circuit simulations were done and optimized by MOGA search process to find the best operating condition that produces hydrocyclone overflow and underflow streams with predefined particle sizes simultaneously. The results indicate that there are various solutions that can be recommended for plant testing and performance improvements. The results of plant implementation of one solution for scenario No. 4 showed improved circuit performance and also validated simulator predictions.

Estimation of particle size in hydrocyclone underflow streams by use of Multivariate Image Analysis

Photographic images were collected of the underflow slurry stream of a laboratory-scale hydrocyclone classifying Merensky, UG2 and Platreef platinum group metal ores. Textural descriptors of the images derived by means of a steerable pyramid algorithm could be used to predict the mean particle size of the underflow slurry streams. The model consisted of a linear discriminant classifier that first identified the underflow as comprising coarse, intermediate or fine particle flow. Use of the centroids or mean particle sizes of these three classes could explain on average approximately 81% of the variance in the mean particle sizes of the underflow streams. These measurements can be performed online, and could form the basis for more advanced control of hydrocyclones and mineral processing circuits in general.

Impact of flocculation on flotation tailing's hydro-cycloning properties

Research results of hydro-cycloning of flocculated and non-flocculated flotation tailing from the lead and zinc open pit mine 'Suplja stijena', Sula - Montenegro have been shown in this paper. Reason for this research was finding conditions in order to separate fraction that is suitable for embankment erection. Flotation tailings has been tested in the very state that it goes out from the flotation process and tailings which is flocculated by anionic flocculant. The object was to determine the impact of flocculation on properties of hydro-cycloning products and disposal process. In hydro-cycloning process greater underflow mass is being separated with non-flocculated tailing. Values of geomechanical parameters are significantly different, especially hydro-cyclone's underflow. All geomechanical parameters of hydro-cyclone's underflow are suitable for erecting embankment which shall be made from non-flocculated tailing. Underflow drainage of non-flocculated tailing is faster while overflow drainage is slower and problematic with both tailings.

A study on the characteristics of spray angle formation in a 2 inch hydrocyclone using water only

It has been understood that the nature of slurry discharge through a hydrocyclone underflow provides an indication of its performance. Although a few attempts have already been made to correlate the discharge profile with hydrocyclone performance in quantifiable terms, a user friendly, robust tool is yet to be developed. In this article an attempt has been made to measure the spray angle at various operating conditions using a simple photographic technique. The study is restricted to water only. The measured data thus generated has been correlated well with inlet Reynolds number and with two exit diameters. Good reproducibility of the measured data over a prolonged duration of time and the developed correlation reaffirms that the spray angle could possibly be used as a useful tool to monitor hydrocyclone performance.

A study of flotation kinetics of the hydrocyclone overflow and underflow in the processing of high-grade copper ore

The results of flotation kinetics the hydrocyclone underflow and overflow in high-grade copper ore processing from the Copper Mine Bor (RB Bor), suggest the possibility of improving the current technological flotation process. This is confirmed by the following results: the distribution of copper in classification product in ration 80:20 % in favor of hydrocyclone underflow as well as higher copper content in the sample and individual class of hydrocyclone underflow compared to the same parameters of hydrocyclone overflow. Participation of optimal size class - 0.075 mm in hydrocyclone underflow is 32.47 %, with copper content of 4.38 %, resulting that about 65 % of total copper in this class to the feed of hydrocyclone is distributed in hydrocyclone underflow and 35 % in the same class in hydrocyclone overflow. Copper recoveries, obtained in laboratory batch flotation tests from hydrocyclone overflow and underflow, are 90.77% and 7.94 %, respectively. Calculated in relation to total copper in the feed of hydrocyclone, 17.30 % Cu can be valorized from hydrocyclone overflow by flotation process, with the same process, 59.58 % Cu is valorized from hydrocyclone underflow, what is 3.44 times more. The results indicate higher copper recovery and slightly better flotation kinetics of hydrocyclone overflow. However, due to better liberation of solid phase and optimization the pulp density in the flotation process, each class of hydrocyclone underflow gives higher contribution to the copper recovery compared to the relevant class of hydrocyclone overflow, calculated on copper, contained in the same class of hydrocyclone feed. Parallel flotation of hydrocyclone overflow and underflow can improve the existing technological process of high-grade copper ore processing in the Copper Mine Bor.

The effect of the design of a secondary grinding circuit on platinum flotation from a UG-2 ore

Platinum concentrator plants experience significant losses in their overall Platinum Group Elements (PGE) recoveries due to the inefficiencies of their secondary grinding circuits. This study involves an investigation of selective grinding of the platinum-bearing silicate particles present in UG-2 platinum ores found in the Bushveld Igneous Complex (BIC). Batch-scale laboratory test work was done to investigate the effect of a secondary milling circuit configuration, using a hydrocyclone underflow sample from a UG-2 concentrator plant as feed material. The envisaged secondary milling circuit consists of a conventional hydrocyclone to de-slime the feed followed by density separation with a spiral concentrator to separate the ore into lights (silicates-rich) and heavies (chromite-rich) fractions, followed by separate milling of the two fractions in parallel ball mills, and combined rougher flotation. A full-scale spiral was run in batch mode, followed by separate milling of samples in a 200 mm diameter mill and combined flotation in a 4.2 l cell. The milling energy inputs were re-distributed between the lights and heavies mills to determine the effect on the platinum mineral rougher flotation recovery and the Cr entrainment. The most promising results were found with 88% of the energy input to the lights mill and 12% to the heavies mill. The results indicated that under batch conditions, the secondary rougher flotation recovery (69% 4E) was similar to the conventional mill-float circuit (70%) however the Cr entrainment was significantly reduced by approximately 40% (2.3–1.4% Cr). This test work has confirmed the benefit of separate milling in the secondary milling circuit for a UG-2 ore. Spiral concentrators have shown potential as an effective density separating device to produce a silicate-rich and chromite-rich fraction for milling; further test work will be conducted to confirm its viability on an industrial scale.

Controlled wash water injection to the hydrocyclone underflow

In hydrocyclones, the classification efficiency is limited by the fines, which are discharged together with the water in the underflow. It is well known that the injection of water in the conical portion of the cyclone reduces the fines in the underflow. This paper presents an improved technique, which is done via an injection at the upper end of the apex or the conical end. This results in a greater washing effect and reduced consumption of wash water. The process is stabilized by controlled water injection specific to the underflow shape. This controlled wash water injection is applied to kaolin processing for the reduction of kaolin losses in the cyclone underflow. A series of tests using 50-mm cyclones was conducted in this work, which demonstrates the marked improvement of the partition curves using controlled water injection.

Grinding capacity enhancement by solid concentration control of hydrocyclone underflow

A control strategy to increase the mineral feed tonnage in grinding operations was developed and evaluated in an industrial mill. The control strategy maximizes the solid concentration at the hydrocyclone underflow discharge while keeping the particle size constant. The manipulated variables are the set-points of the fresh solids rate controller and the sump water flowrate controller. The system was tested in two grinding circuits at El Teniente Division, Codelco-Chile. Results showed a 5–12.5% increase in treatment capacity while the product size at the hydrocyclone overflow was kept under control (25%+150 μm). Alternatively, the extra capacity generated by the optimizing control strategy can be used to shutdown some of the grinding circuits without losing the actual plant capacity. Also, the dynamic response of the grinding circuit was characterized for open loop step changes in fresh mineral rate and sump water flowrate.

Hydrocyclone underflow monitoring using image processing methods

Until a few years ago there has been little development of image processing systems in the minerals industry, mainly owing to the computational demands of image recognition and interpretation. Due to rapid progress in computer technology at present however, image processing systems are increasingly being investigated in order to solve complex process engineering problems. In this investigation videographic analysis of the hydrocyclone underflow discharge is applied primarily as a diagnostic tool to assess the performance of the classifier. The discharge spray angle is a visual parameter which immediately identifies normal (umbrella profile discharge) or anomalous (roping discharge) operation, and can be directly interpreted to characterise internal flow properties such as pressure drop. Also, this information can be applied to estimate the feed stream particle concentration and ultimately the hydrocyclone's cut size and can serve as a basis for considerable improvement in the on-line control of mineral processing circuits as a whole.

5308448 Process for the flotation of fillers from deinked waste paper in the presence of surfactants containing sulfonate groups: Ansga Behler, Raine Hoefer, Klaus Hornfeck, Wolfgang von Rybinski, Bottrop, Federal Republic Of Germany assigned to Henkel Kommanditgesellschaft auf Aktien

Thickeners have traditionally been used to dewater tailings streams containing fine coal from washeries. When British Coal built a new Baum Jig washery at Deep Navigation Colliery in Wales, UK, instead of a thickener they installed high performance hydrocyclones and horizontal belt filters to do the same job. Advantages included lower capital cost, easier operation and maintenance and considerably reduced space requirement. The hydrocyclones dewater and thicken underlows from dewatering screens and centrates from centrifuges. The filtered hydrocyclone underflow forms a fine coal product. Hydrocyclone overflow is returned to the jig as make up water. The paper describes in detail the design and operation of the washery circuit, highlighting the benefits gained from the use of hydrocyclones.