Knelson Concentrator Research Articles

Beneficiation of the Nechalacho rare earth deposit. Part 1: Gravity and magnetic separation

The beneficiation of rare earth element (REE) minerals may include many different beneficiation unit operations, but the final process choice typically depends on the inherent mineral characteristics. The Nechalacho REE deposit contains multiple low specific gravity, diamagnetic silicate gangue minerals (predominantly feldspars and quartz) and high specific gravity, iron oxide minerals (magnetite and hematite). The valuable REE minerals (REM) in the deposit consist of a variety of relatively high specific gravity, paramagnetic minerals. A process has been proposed to concentrate the value REM through a combination of gravity (rejecting silicate gangue) and magnetic (rejecting iron oxide gangue) separation steps prior to froth flotation.This work employed a laboratory-scale process including two different gravity separation steps (Knelson and Falcon centrifugal concentrators) followed by a series of varying intensity wet drum magnetic separation steps as well as dry induced roll magnetic separation and wet high intensity magnetic separation steps. The resultant fractions have been characterized by XRD, ICP-MS, and QEMSCAN to identify the optimum fraction for downstream flotation separation. The combination of a Knelson Concentrator with low intensity wet drum magnetic separation was found to efficiently concentrate REM while also rejecting high specific gravity iron oxide minerals. A novel finding from this study is the concentration of heavy REE-bearing zircon into coarse size fractions after grinding.

노트북 인쇄회로기판 전자부품으로부터 탄탈럼의 분리

The study to obtain tantalum concentration from electronic components (ECs) on Printed circuit board assembly (PCBA) of laptop was conducted. Electronic components on laptop PCBA were detached from boards by using self-developed experimental apparatus. The detached electronic components were sieved and 93.2 wt.% of tantalum capacitors were concentrated from the size interval from 2.80 mm to 6.35 mm. The tantalum capacitors were pulverized by hammer mill and electrodes (anode and cathode) were removed from the grinding products by using magnetic separators under the magnetic force of 300 Gauss. Finally, tantalum concentrate was concentrated from the magnetic separator products by using Knelson concentrator, and the maximum efficiency of 76.9% was achieved under the operating condition of bowl rotating speed of 200 rpm, and fluidizing water flowrate of 7 L/min. The grade and recovery of Ta concentrate under the condition were 81.1% and 78.8%, respectively.

Application of Full Factorial Experimental Design and Response Surface Methodology for Chromite Beneficiation by Knelson Concentrator

The present work is undertaken to determine the effect of operational variables, namely: feed rate, centrifugal force and fluidization water flow rate on the efficiency of Knelson concentrator for chromite ore beneficiation. A full factorial design with three factors at three levels and response surface methodology (RSM) were applied for this purpose. The quadratic models were developed to predict the concentrate Cr2O3 grade and recovery as the process responses. The results suggest that all the variables affect the grade and recovery of the Cr2O3 concentrate to some degree. However, the fluidization water rate was found as the most effective parameter.

Separation of Heavy Metals From Contaminated Sediments Using Knelson Concentrator

Separation of Heavy Metals From Contaminated Sediments Using Knelson Concentrator

Size-by-size analysis of dry gravity separation using a 3-in. Knelson Concentrator

Centrifugal concentrators have been widely used to recover fine gold over the past few decades, the main drawback being the large volume of water required during the operation. As water is an increasingly important commodity, investigating dry processing to reduce water usage is of great importance. This work investigated using a laboratory scale Knelson Concentrator with a dry feed, and air being used to replace water as the fluidising medium and size-by-size testing of material. A synthetic ore comprised of tungsten and quartz was used to mimic a gold ore. Response surface methodology and central composite design were used for modelling and optimisation with the experimental variables being the motor power (MP) (%), air fluidizing pressure (AFP) (psi) and solid feed rate (SFR) (g/min). The observed results of the three size classes indicated that amongst the three variables; the motor power had the greatest impact when comparing to the other two variables. Different optimum conditions had been found for −425+150μm, −150+53μm and −53μm size fractions and these are 30% MP, 200g/min SFR and 10 psi AFP, 50% MP, 160g/min SFR and 11psi AFP, 65% MP, 200g/min SFR and 11psi AFP, respectively.

Gold exploration using heavy minerals in till and weathered bedrock in Petäjäselkä, northern Finland

As a part of a gold exploration project in Petäjäselkä, northern Finland, carried out by the Geological Survey of Finland, heavy mineral studies and detailed till geochemical and stratigraphical studies were used for mineral exploration. These studies covered c . 22 km 2 in the Petäjäselkä area. The objective of this research was to find out how heavy minerals and till geochemistry can be used in gold exploration, and how they reflect the glacial dispersion in shallow till areas in Petäjäselkä. Furthermore, an automated mineralogical identification method (SEM-EDS) was tested in the indicator mineral research. Samples from till and underlying, pre-glacially weathered bedrock were collected from the test pits and trenches. A total of 381 heavy mineral and 713 geochemical samples were collected. The heavy mineral samples were concentrated with a spiral concentrator and a Knelson concentrator. The geochemical samples were analysed by ICP-AES and GF-AAS following aqua regia decomposition. The elevated gold contents and distinct anomalies found in till and weathered bedrock indicate the whole study area to have potential for gold mineralization. Based on microscopic and automated mineralogical studies, native gold was the only useful indicator mineral present in the heavy mineral samples for gold exploration in Petäjäselkä.The detailed till geochemical results show that the glacial transport distance in Petäjäselkä is short, only some tens of meters. Differences in the Au-Ag contents of the gold grains were noted between the three gold mineralized targets in Kerolaki, Selkä-Mäntypää and Ranta-Mäntypää. Arsenic, bismuth and tellurium proved to be pathfinder elements for gold mineralization both in till and weathered bedrock. The results of this study show that the heavy mineral studies, together with till geochemical studies, provide a useful method for identifying exploration targets in glaciated terrain. However, different methods of heavy mineral concentration affect the recovery of gold grains and thereby the final results of this study.

A design of experiments investigation into dry separation using a Knelson Concentrator

Enhanced gravity, or centrifugal, separators have revolutionised gold processing over the past decades, significantly increasing the recovery of fine (−100μm) free gold. One of the main drawbacks of centrifugal gravity concentrators is the large volume of water required (even if it is all recycled). With water becoming an ever increasingly important “commodity”, reducing this is of importance both from an environmental and a monetary point of view. This work investigated operating a laboratory scale Knelson Concentrator with a dry feed and using air as the fluidising medium. The feed used was a synthetic mixture of tungsten and quartz, used to mimic a gold ore. The response surface method and central composite design techniques were used to design the experiments and to model the results, with the experimental variables being the bowl speed (G-Level), air fluidising pressure and the feed rate. The models corresponded well to the experimental results, indicating that for this experimental setup, the optimal conditions were a bowl G-Level of 40G, a feed rate of 220g/min and an air fluidising pressure of 8psi.

Enrichment of low-grade colemanite concentrate by Knelson Concentrator

Enrichment of low-grade colemanite concentrate by Knelson Concentrator

Separation Development Studies on the Beneficiation of Fine Lignite Coal Tailings by the Knelson Concentrator

While disposing of fine coal without use was cheaper and more permissible previously, recovering some of the fine coal changes the mass balance of wastes and makes co-disposal or integrated dumps possible. The present study aims to investigate the processing of fine lignite coal tailings with 59.08% ash content from Soma tailings ponds in Turkey using a Knelson concentrator and to identify in both numerical and experimental methods the fundamentals of the reason why the Knelson concentrator must be operated in hindered settling conditions for high efficiency separation of high ash-bearing fine lignite coal tailings. The lignite coal tailings were treated by a two-stage concentration scheme for the recovery of fine clean coal. Pre-enrichment experiment parameters were determined by the Taguchi experimental design method, and the results were interpreted by the SPSS 17.0 program to evaluate the optimum parameter values. After the pre-enrichment process, a coal concentrate (42.60% ash, 0.71% total sulfur, an...

The potential for dry processing using a Knelson Concentrator

Centrifugal gravity concentrators currently operate on a wet basis, with slurry feed and fluidising water used to enhance the separation based upon density differences. This work investigated the potential for running a laboratory scale 3″ Knelson Concentrator on a dry basis. Air was used as the fluidising medium in order to separate tungsten from silica in a synthetic ore (1%w/w tungsten), and compared to an optimised wet process. The wet processing attained a mean tungsten recovery of 94.92% (tungsten grade: 30.96%). The dry processing at two different fluidising air pressures attained a recovery of 78.53% (tungsten grade: 6.32%) and 69.90% (tungsten grade: 15.57%) at 2psi and 3psi respectively. This preliminary work shows that it is feasible to separate minerals on a dry basis in a Knelson Concentrator.

Performance curve approach to optimising fluidising water for Knelson concentrators

Centrifugal concentrators such as Knelson concentrators (KCs) are commonly used in most gold processing plants to recover fine liberated gold particles. The decision to employ a gravity recovery circuit is primarily based on the amount of gravity recoverable gold (GRG) in the ore among other considerations. However, the conditions required to optimise the gold recovery in such devices used in plants cannot be determined by GRG test results as the separation of particles is based on the particle bed dynamics within the given unit which are different to those encountered in a three inch KC used for the GRG test. The significant operating variables that affect the performance of a KC are the size distributions of the gold and gangue, rotational speed of the bowl, fluidising water flowrate and the cycle time. Of these variables, the rotational speed is generally fixed, and the size distributions of the gold and gangue are determined by the comminution circuit employed. Thus, the fluidising water is the key variable that can be used to control the dilation of the particle bed to maximise the recovery of gold. This paper examines the validity of the GRG test for performance evaluation and discusses an alternative method based on performance curve of the device that can be used to evaluate the optimum fluidising water flowrate of an operating machine. The principles of determining the performance curve of the machine and its use are also discussed and illustrated with laboratory and plant data.

Desulphurization and deashing of oxidized fine coal by Knelson concentrator

In order to efficiently clean fine coals, enhanced gravity separators, such as Knelson concentrator, have been developed. Although the Knelson concentrator has not been applied yet in industrial scale for fine coal cleaning, different investigations have been conducted in recent years. In this study, an oxidized coal with high sulphur was subjected to cleaning process by Knelson concentrator after being classified into the size fractions of −106μm, −300+106μm and −500+300μm. Experimental variables were coal particle size, bowl speed and fluidizing water pressure. Maximum combustible matter recovery, pyritic sulphur rejection, and ash rejection were achieved to be 99.13%, 91.60%, and 60.94%, respectively. The highest separation efficiency for the pyritic sulphur and ash was determined to be 67.91% and 39.53%, respectively. These corresponded to the removal of 70.45% of pyritic sulphur with combustible matter recovery of 97.46% and removal of 45.96% of the ash with combustible matter recovery of 93.57%. Coal particle size, bowl speed and fluidizing water pressure were determined to affect the separation performance with a close interaction between them.

Beneficiation of the gold bearing ore by gravity and flotation

Gold concentration usually consists of gravity separation, flotation, cyanidation, or the combination of these processes. The choice among these processes depends on the mineralogical characterization and gold content of the ore. Recently, the recovery of gold using gravity methods has gained attention because of low cost and environmentally friendly operations. In this study, gold pre-concentrates were produced by the stepwise gravity separation and flotation techniques. The Knelson concentrator and conventional flotation were employed for the recovery of gold. Gold bearing ore samples were taken from Gumushane Region, northern east part of Turkey. As a result of stepwise Knelson concentration experiments, a gold concentrate assaying around 620 g/t is produced with 41.4wt% recovery. On the other hand, a gold concentrate about 82 g/t is obtained with 89.9wt% recovery from a gold ore assaying 6 g/t Au by direct flotation.

Overview of common processing methods for recovery of indicator minerals from sediment and bedrock in mineral exploration

ABSTRACT Over the past two decades, the application of indicator mineral methods to mineral exploration has expanded significantly such that they are now used to explore globally for a broad spectrum of commodities. Indicator mineral suites have been identified for a variety of ore deposit types including diamond, Au, Ni-Cu, PGE, metamorphosed volcanogenic massive sulphide, porphyry Cu, U, Sn and W. Indicator minerals, which include ore, accessory and alteration minerals, are sparse in unconsolidated sediments, thus sediment samples must be concentrated in order to recover and examine them. Because most indicator minerals have a moderate to high specific gravity, processing techniques involving density separation, in combination with sizing and magnetic separation, are used to recover them from sediment samples. This paper reviews the commonly used processing methods including panning, hydroseparation, tabling, Knelson concentrators, spiral concentrators, dense media separators, jigs and various types of magnetic separators, as well as mineral selection and mineral chemistry determinations. Monitoring of quality control is essential at each stage in these processing, picking and analytical procedures. When reporting indicator mineral results, processing methods, fraction weights and size ranges, and laboratory name should all be recorded, in addition to indicator mineral abundance data.

Altın Üretiminde Siyanür Tüketiminin Azaltılması İçin Farklı Bir Yöntem: Gravite Zenginleştirme ve Liç Kombinasyonu

Gold minerals are primarily recovered by cyanidation which accounts for 83% of the world gold production, cyanide consumption and concurrently the environmental concerns are expected to increase in the foreseeable future with the forecasted increase in gold production. In this study, an alternative gold treatment process is proposed to reduce the cyanide consumption. The process was applied to Izmir-Menderes gold ore and the results were compared with the conventional leach process. In conventional system, cyanidation is applied directly to the ore to extract the gold. In the alternative process, gold is pre-concentrated first with the gravity based Knelson concentrator, then, cyanidation is applied only to the pre-concentrate instead of the whole ore. In this study, a pre-concentrate containing 93 g/t of gold was produced from a gold ore with 6.7 g/t grade, using only water during processing. The cyanidation is only applied to this pre-concentrate. Thus, this alternative process saves about 70% cyanide.

Improvement and Modelling of the Knelson Concentrator

The Knelson concentrator is a centrifugal separator which was originally and successfully designed for extracting free gold particles. Despite of its wide range of applications, the exact concentration mechanism of the device is not fully understood. The purpose of this research was to determine the optimum parameters and improve the performance of knelson concentrator by investigating the effects of artificial porous beds and pulsed water jackets on the performance of the device. Artificial bed consists of glass beads of range 1.5-2 mm diameter have been used. It was found that two techniques can improve the performance of the batch Knelson concentrator. The experimental work showed that improvement ratio of concentrator was increased about 1.55 for flow rate 8 l/m compared with no bed for the same flow rate. In addition, the improvement ratio was increased about 1.25 when pulsed water was used. Another purpose of this work was to develop mathematical model approaches to understand the fundamental mechanism of the Knelson concentrator. In addition, two mathematical model of the Knelson concentrator have been developed. Key words: Kneslon Concentrator, Pulsation, Porous Bed, Mathematical Model

Understanding the discrepancy between prediction and plant GRG recovery for improving the gold gravity performance

Gravity recoverable gold (GRG) content in a sample is typically determined using the standard three-stage test developed at McGill University ( Laplante et al., 2000). A comparison of GRG recovery in laboratory with its actual recovery in plants shows that plants recover between one-third and two-thirds of the predicted GRG from laboratory test. Research conducted at COREM seeking the identification and the understanding of potential causes of this discrepancy reveals that particle shape transformation during grinding is a major contributor among other causes such as bleed percent processed, quality of cyclone classification and gravity concentrator operating conditions. To analyze the gold particle shapes and their deportment, samples were collected from different streams of a grinding–gravity (Knelson) circuit in a gold plant and compared to a concentrate sample from a laboratory Knelson concentrator (KC MD3). A particle characterization based on gold morphology was developed to diagnose typical shapes generated in the gold grinding–gravity circuit. The study revealed that the GRG particles reporting to the plant cyclone overflow are the most flattened particles among the samples analyzed and that on the other hand gold particles recovered in the laboratory Knelson concentrator are the least flattened, highlighting the potential cause of discrepancy between the two recoveries. In this paper, the GRG mapping in a conventional grinding–gravity circuit and the transformation of GRG to non-GRG, as mainly explained by gold particle reshaping will be discussed.

Gold recovery by KC from grinding circuit of Bergama CIP plant

Numerous research studies have been done to improve the gold recovery methods and to fi nd alternative processing techniques in the last decade. The main goal in this search has become to design an effi cient plant employing environmentally acceptable processes today. For this purpose, the application of environmentally friendly, no chemical included techniques like centrifugal gravity separators are preferably used in gold recovery plants prior to or in place of cyanidation. In this study, the recovery of the gold particles accumulated in the grinding circuit of a CIP plant was investigated by using Knelson centrifugal separator. A KC-MD7.5 Knelson concentrator was installed in the grinding circuit of Bergama/Ovacik CIP plant. The concentrator was operated while the Mastra gold ore cyanidation tests were running on the plant.

Evaluation of leaching parameters for a refractory gold ore containing aurostibite and antimony minerals: Part I – Central zone

A cyanidation study was conducted on a mild refractory gold ore sample from the Central zone of Clarence Stream Property, owned by Freewest Resources Canada, to develop a leaching strategy to extract gold. Gold, at a grade of 8.00 g/t, is present as native gold, electrum and aurostibite. The ore also contains 2.8% pyrrhotite, together with several antimony minerals (0.8% berthierite and gudmundite, 0.18% native antimony and stibnite). It also exhibits weak preg-robbing properties with 0.16% organic carbon. Aurostibite, a gold antimony compound, is particularly known to be insoluble in cyanide solution. The antimony dissolves in cyanide solution to form antimonates, which retards gold dissolution. Industrial practice of extracting gold from aurostibite generally consists of producing a flotation concentrate, which is leached in a pipe reactor at low alkalinity and high oxygen pressure with about 20 g/L cyanide. The proposed new approach is efficient and allows the extraction of gold directly from an ore at atmospheric pressure and a low cyanide concentration at pH 10.5. The effects of grinding, pre-treatment, lead nitrate, kerosene and cyanide concentrations have been investigated. The maximum gold extraction obtained on the ore was 87.9% using 800 ppm NaCN, 500 g/t lead nitrate, 30 g/t kerosene, DO (dissolved oxygen) 10 ppm and pH 10.5 in 168 h. The associated cyanide consumption was 1.3 kg/t. The additions of lead nitrate and kerosene increased gold extraction. In comparison to a P 80 of 74 μm, a P 80 of 30 μm significantly increased gold extraction. Gold in solid solution in gudmundite and arsenopyrite was believed to be responsible for the un-leached fraction until mineralogical analysis of hydroseparation concentrates of leach residues showed that most of the un-leached gold occurs as aurostibite, either as locked grains in sulphides/sulpharsenides or as grains with passivation rims of an Au–Sb–O phase. Coarse gold was also found. Gold extraction was not sensitive to cyanide concentration from 250 to 1200 ppm NaCN and high pH was detrimental. Decreasing the cyanide concentration reduced the cyanide consumption from 1.39 to 0.85 kg/t. The removal of coarse gold using a Knelson concentrator and a Mosley table prior to leaching increased the gold extraction to 90.4% (leach residue at 0.77 g/t).

Quantifying the content of gravity recoverable platinum group minerals in ore samples

A protocol for predicting recovery of platinum group minerals (GRPGM) is adapted from the protocol for gravity recoverable gold. This paper introduces the methodology to characterize the content of GRPGM in samples using the 3-in. (7.5 cm) laboratory Knelson concentrator. Results for two ore samples are presented, as well as some mineralogical analysis of the gravity concentrates. The methodology can also be used for sample preconcentration to aid mineralogical analysis.