Mineral Processing Plants Research Articles

Proactive Control Models for Gold Processing Plant Input Reagents Consumption Management. Case Study: Goldfields Ghana Limited, Tarkwa

Authentically, this case study shows that, proactive approach to resolve reagent input supply problems at the Process Plant of Goldfields Ghana Limited-Tarkwa Mine is the key to ensuring higher productive and competitive advantage in today’s business environment. Pragmatically, the cases studied revealed the existent to which reagent control models used at Goldfields Ghana Limited-Tarkwa Mine and pointed out the lack of advance warnings with regard to reagent inventory control chart, quality control model and lime consumption control method. Additionally, the minimum and maximum model application has limited control over inventory to meet abrupt changes in rate of usage. Clearly, the paper identifies lack of proactive measures in the area of limits set for taking corrective actions of the various models. Notably, the future warning signal of slope analysis depends on the focus of the given reference variables. Consequently, convergence of opposing focus variables depicts a deteriorating future while’s divergence point to a better future. Conversely, convergence of similar focus variables point to better future while as divergence indicates deteriorating future. The paper recommended applicable slope analysis approach as complementary methods to enhance proactive assessment of all the reagent control models to ensure the achievement of competitive advantage in the company’s endeavour. Cost and consumption variances analysis model was the further research work recommended by this paper as another method that will go a long way to enhance proactive reagent control at the Goldfields Ghana Limited-Tarkwa Mine Mineral Processing Plant operations.

Instituting a filtration/pressurization system to reduce dust concentrations in a control room at a mineral processing plant.

The National Institute for Occupational Safety and Health has observed that many control rooms and operator compartments in the U.S. mining industry do not have filtration systems capable of maintaining low dust concentrations in these areas. In this study at a mineral processing plant, to reduce respirable dust concentrations in a control room that had no cleaning system for intake air, a filtration and pressurization system originally designed for enclosed cabs was modified and installed. This system was composed of two filtering units: one to filter outside air and one to filter and recirculate the air inside the control room. Eighty-seven percent of submicrometer particles were reduced by the system under static conditions. This means that greater than 87 percent of respirable dust particles should be reduced as the particle-size distribution of respirable dust particles is greater than that of submicrometer particles, and filtration systems usually are more efficient in capturing the larger particles. A positive pressure near 0.02 inches of water gauge was produced, which is an important component of an effective system and minimizes the entry of particles, such as dust, into the room. The intake airflow was around 118 cfm, greater than the airflow suggested by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) for acceptable indoor air quality. After one year, the loading of the filter caused the airflow to decrease to 80 cfm, which still produces acceptable indoor air quality. Due to the loading of the filters, the reduction efficiency for submicrometer particles under static conditions increased to 94 percent from 87 percent.

Dissimilar Welding of SS 409 and Mild Steel by Gas Tungsten Arc Welding (TIG) Method by ER 309 L Electrodes

The dissimilar material welding at lower expensive is one of the popular techniques which are used in power generation services such as mining, petro chemical refineries and mineral processing plant as well as recuperator in furnace system. For these applications, the insulation plays an important role for effective result. Fluid flow from one medium to another medium is carried out through insulation materials to prevent the transmission of excessive heat. If it gets wet, it loses all its insulation properties. It is easily crushed if the pipe gets stepped on. The materials serves important role to save the heat energy in operating and constructing the power plant. In this research work, mild steel and stainless steel SS 409 are welded together by ER 309 L electrode by TIG welding process to achieve these applications. Service temperature is sensible; inside temperature is maintained low because of rapid cooling. This research concludes that, insulation material is not necessary for dealing out the material (below 700°C). Stainless steel SS 409 tends to contract and expand more and serves as good corrosion resistant material at the service temperature. Mild steel is a good heat conductor; it cools quickly and contract earlier as the joint cools and the heat is removed from the metal surface.

Concurrent reconciliation of chemical and mineral assays for mineral processing circuits

The steady-state data reconciliation of mineral processing plants has traditionally depended on chemical assays of samples collected from various streams in the plant. In some cases, additional information in the form of size assays and size-wise chemical assays have been employed to improve the reconciliation problem. Reconciliation algorithms, in addition to making the measured data consistent with the basic conservation principles, also help in predicting the material flow rates in different streams. This information helps the process engineer to identify and troubleshoot problem areas, and further use it to optimize the plant's performance. If all the minerals present in the ore system are known (established through X-Ray Diffraction), the chemical formulae of the minerals provide the relationship between the chemical assays and mineral composition. In this communication, first we propose an approach to estimate the mineral composition from the measured chemical assays for a given sample or stream. It is then extended to a plant-wide concurrent data reconciliation methodology, involving both the chemical assays and mineral composition. This concurrent data reconciliation procedure provides estimates of mineral composition around the plant even when mineral composition measurements are not available. This additional information will help the plant engineers to track and improve their plant's behavior more intuitively. When mineral compositions are measured (for example, through QEMSCAN) they can be reconciled along with chemical assays. The methodology is demonstrated with data from batch and semi-batch laboratory studies on selective dispersion-flocculation of iron ore slimes.

Improved dewatering of iron ore fines by the use of surfactants

The role of chemical reagents to reduce moisture in iron ore fines is explored in the present work which includes ionic and non-ionic surfactants. The washing of iron ore in mineral processing plants result in moisture of about 11–14% in the fines and about 4% in the sized ore. The moisture level goes up to 16% in the fines during the monsoon season. Dewatering of fines is a major problem in all mineral processing industries. As the ores deteriorate in their quality, generation of fines and ultra-fines is increased proportionally. The ultra-fines adsorb much moisture due to their extremely large surface area and these tend to adhere to the relatively coarser fines, thus increasing the percentage of moisture in the fines. This paper reports an experimental investigation on the effect of anionic, cationic and non-ionic surfactant on the dewatering behaviour of iron ore fines (−6mm) and also plant trials with the selected surfactant. The surfactants taken up for studies are sodium dodecyl sulphate (SDS), poly ethylene oxide 4000 (PEG), cetyl trimethyl ammonium bromide (CTAB). All the surfactants were found to give good results w.r.t. moisture reduction. From the laboratory experiments it was observed that there was reduction in gangue (mainly aluminosilicates) level as well by the application of the surfactant. The promising results of the laboratory scale tests led to plant trials with SDS which gave 2 to 4% (absolute) moisture reduction in the fines.

Sulfide-rich mine tailings usage for short-term support purposes: An experimental study on paste backfill barricades

Barricade failures generally occur at the early times of paste backfill when it is fresh in the stopes. The backfill strength increases and need for barricading pressure decreases as a result of the hydration reactions. In this study, paste backfill barricades of Cayeli copper mine were investigated to design cemented mineral processing plant tailings as barricade body concrete. Paste backfill in sub-level caving stopes of the mine needs to be barricaded for only four or five days. Therefore, short term strength and workability tests were applied on several cemented tailings material designs. Barricade failure mechanisms, important points of barricade designing and details of the new concrete material are explained in this work. According to the results obtained with this experimental study, the tailings were assessed to be used in concrete applied as temporary supports such as cemented paste backfill barricades.

Development of a techno-economic simulation tool for an improved mineral processing plant design

Simulation is widely used in design and optimization of mineral processing circuits to answer “what if” questions regarding the employment of different equipment and configurations. The questions could be answered better if the long-term economic impacts of different circuits are readily estimated within the designing stage, considering both economic and technical constraints and criteria. This paper introduces a new open source user-friendly techno-economic simulator developed in Matlab/Simulink that joins multivariate capital and operating cost models to technical models of equipment and estimates some economic analytical indicators of the circuits such as Net Present Value simultaneously when the circuit is being designed. The proposed approach enables the designer to easily consider the technical and economic interactions and tradeoffs. As a case study, the long-term economic impact of selecting different numbers of leaching tanks is investigated and it is shown that even the optimum number of tanks could be a function of discount rate of the project.

Failure analysis of jaw crusher and its components using ANOVA

In this present scenario, with the subsequent rise in the ever increasing demand of production from mines, the role of mineral processing plant has grown leaps and bounds with time. So, the need of the hour is to have sophisticated and handy equipments which can be operated with ease and can help in enhancing the productivity from mines. In this regard, Crusher is one of the primary and essential equipment which is employed for comminuting the mineral in processing plants. Hence, any kind of failure of its components will accordingly hinder the performance of the plant. Therefore, to minimize sudden failures, proper brainstorming needs to be done to improve performance and operational reliability of jaw crushers and its components. Though traditional maintenance practices exist in mineral processing plants, a methodical approach to analyse the failure rates of components is imperative for improving operational reliability of equipment by implementing effective maintenance strategies. This paper considers the methods for analysing failures of jaw crusher and its critical components in a mineral processing plant using statistical tools namely life data analysis (LDA) and analysis of variance (ANOVA). The shape and scale parameters using LDA method have been also examined. Further by implementing ANOVA, parameters such as the shape, scale and time are evaluated to examine the failure rates of crusher and its components. The data for these three parameters have been generated through Monte-Carlo Simulation method. A 23 factorial design is used for the failure rate analysis.

Identification and stochastic modelling of sources in copper ore crusher vibrations

A problem of rolling element bearings diagnostics for different machines is widely discussed in the literature. Most of the methods are based on the vibration signal analysis. However for some real signals the classical methods of damage detection are insufficient because of the specific nature of examined data. This specific nature is very often manifested through overlapping, mixing or interleaving of processes with different statistical properties and may be the result of different sources that have influence on the analysed signal. The problem of different sources identification and parametrisation of processes which are related to them is very challenging and requires advanced techniques. There are many methods which can be useful in this context however each signal should be analysed separately and there is no universal technique adequate to all possible time series. In this paper we propose a method of sources identification for vibration signal from the heavy duty crusher used in mineral processing plant. A crusher is a kind of machine which use a metal surface to crumble materials into small fractional pieces. During this process, as well as during entering material stream into the crusher, a lot of impacts appear. They are present in vibration signal acquired from bearings housing. Moreover, for some cases we also observe cyclic impulses which may be related to damage of rolling element bearings in the machine. The proposed sources identification method, especially useful for crushers vibrations, is based on the statistical analysis of examined data. Moreover by using advanced techniques of time series theory we propose a stochastic model that exhibits similar statistical properties as analysed signals. The introduced technique can be a starting point to damage detection of rolling element bearings of copper ore crushers.

Closure of Artisanal Small Scale Gold Mining Processing Plants in Ecuador

Political tension over the discharge of artisanal mine tailings into the Puyango-Tumbes River in Ecuador, which flows into northern Peru, has prompted the closure of the responsible artisanal small gold processing plants and the construction of central processing and communal tailings facility. A coordinated effort on behalf of the federal government, miners, and the local community to develop and fund the project and bring it to completion is underway with the goal of eliminating riverine tailings disposal in the area and reclaiming the current artisanal gold processing plants. The authors propose that any approach to closure planning of ASGM must be: (1) economic and feasible to the community and miners, (2) reasonable for individuals in the community to implement on their own, and (3) expedient, as the process may not follow conventional closure techniques but instead be adapted to function within the ASGM context. The goal of this paper is to reflect on the closure process developed for the artisanal gold processing plants, their dismantlement and reclamation.

Assessing the blue-water footprint of an opencast platinum mine in South Africa

South Africa's extensive mineral resources have resulted in mining activities dispersed across the country, playing a critical role in its socio-economic development. In contrast to this abundance of mineral wealth, water resources are generally limited, and vulnerable to environmental impacts from the mining industry. These circumstances make tailored management of water resources in the mining sector essential. To achieve this, detailed information on water use throughout a mine operation as well as an accurate water balance account is required. Blue-water footprints have the potential to contribute to this task as they allow for quantification of direct and indirect water use across the supply chain of a process, while incorporating both spatial extension and temporal duration. As defined by the Water Footprint Network's (WFN) globally acknowledged water footprint assessment methodology, a blue-water footprint is determined by calculating the net consumptive use of water by an operation. According to the WFN, this includes water which is evaporated, incorporated into a product, or lost to outflows which do not return to the same catchment area in the same period.The applicability of this tool in the mining sector has not been fully explored. Therefore, it was decided to investigate the bluewater footprint of a South African platinum mining operation. The results showed that the largest consumption of water in the production of platinum was due to evaporation from the mineral processing plants (36.8%) and the tailings storage facilities (19.4%). To improve its water-use efficiency, measures should be taken by the operation to mitigate evaporative losses. Floating covers can assist in this effort as they reflect a proportion of the incoming solar radiation and act as a physical barrier to the passage of water vapour, both vertically and horizontally.

Underground Lead-Zinc Mine Production Planning Using Fuzzy Stochastic Inventory Policy / Planowanie Wydobycia Cynku I Ołowiu W Kopalniach Podziemnych Z Wykorzystaniem Podejścia Stochastycznego Z Elementami Logiki Rozmytej Do Określania Niezbędnego Poziomu Zapasów

Abstract Methodology for long-term underground lead-zinc mine planning based on fuzzy inventory theory is presented in this paper. We developed a fuzzy stochastic model of inventory control problem for planning lead-zinc ore production under uncertainty. The final purpose of this article is to find the optimal quantity of mined ore that should be stockpiled, in order to enable “feeding” of mineral processing plant in cases when the production in underground mine is interrupted, by using Possibilistic mean value of fuzzy number for defuzzing the fuzzy total annual inventory costs, and by using Extension of the Lagrangean method for solving inequality constrain problem. The different types of costs involved in mined ore inventory problems affect the efficiency of production scheduling. Dynamic nature of lead and zinc metal price is described by Ornstein-Uhlenbeck stochastic mean reverting process. The model is illustrated with a numerical example.

Integrated approach to assess the environmental impact of mining activities: estimation of the spatial distribution of soil contamination (Panasqueira mining area, Central Portugal).

Through the years, mining and beneficiation processes in Panasqueira Sn-W mine (Central Portugal) produced large amounts of As-rich mine wastes laid up in huge tailings and open-air impoundments (Barroca Grande and Rio tailings) that are the main source of pollution in the surrounding area once they are exposed to the weathering conditions leading to the formation of acid mine drainage (AMD) and consequently to the contamination of the surrounding environments, particularly soils. The active mine started the exploration during the nineteenth century. This study aims to look at the extension of the soil pollution due to mining activities and tailing erosion by combining data on the degree of soil contamination that allows a better understanding of the dynamics inherent to leaching, transport, and accumulation of some potential toxic elements in soil and their environmental relevance. Soil samples were collected in the surrounding soils of the mine, were digested in aqua regia, and were analyzed for 36 elements by inductively coupled plasma mass spectrometry (ICP-MS). Selected results are that (a) an association of elements like Ag, As, Bi, Cd, Cu, W, and Zn strongly correlated and controlled by the local sulfide mineralization geochemical signature was revealed; (b) the global area discloses significant concentrations of As, Bi, Cd, and W linked to the exchangeable and acid-soluble bearing phases; and (c) wind promotes the mechanical dispersion of the rejected materials, from the milled waste rocks and the mineral processing plant, with subsequent deposition on soils and waters. Arsenic- and sulfide-related heavy metals (such as Cu and Cd) are associated to the fine materials that are transported in suspension by surface waters or associated to the acidic waters, draining these sites and contaminating the local soils. Part of this fraction, especially for As, Cd, and Cu, is temporally retained in solid phases by precipitation of soluble secondary minerals (through the precipitation of hydrated metal sulfates) in warm, dry periods, but such minerals are easily dissolved during rainy periods. Climate is an important instability factor, and the hot and dry summers and cold, rainy, and windy winters in this region are physical phenomena that enhance the good receptivity of these soils to retain some of the metals present in the primary and also the secondary mineralogy. Considering the obtained results from both the sequential chemical extraction and the environmental risk assessment according to the risk assessment code, Ag, Cd, Cu, and Zn are classified with very high risk while As is classified with medium risk.

Study of acid mine drainage production potential in flotation tailings of Sarcheshmeh porphyry copper mine

Acid mine drainage (AMD) is one of the most significant environmental challenges facing the mining industry worldwide. Water infiltrating through the metal sulfide minerals, effluents of mineral processing plants, and seepage from tailing dams becomes acidic, and this acidic nature of the solution allows the metals to be transported in their most soluble form. To predict, prevention and treatment of AMD, wastes, and tailing are subjected to series of evaluations that more include the following: mineralogical and textural evaluation studies, static tests that evaluate the balance between acid generation potential and acid neutralizing capacity and kinetic testing that involve site or laboratory tests which describe the weathering, relative potentials for acid production neutralization, sulfide mineral oxidation rates, potential for metal release, and the effectiveness of control techniques. Sarcheshmeh copper mine in Kerman, Iran, has the most important copper concentration plants in Iran. The plant processes more than 40,000 t of copper feeds and rejects about 39,000 t of tailings containing sulfide minerals such as pyrite. AMD is formed by the oxidation of metal sulfides, mainly pyrite and marcasite, which have been exposed to air and water during and following mining operations. With regard to AMD generation possibility, studies related to the AMD problem were carried out. These evaluations were included site geology study, mineralogical studies, paste pH and modified acid-base accounting (ABA) static tests, and modified humidity cell tests. According to the results, it was demonstrated that long dryness cycles in Kerman result to pyrite weathering and production of AMD.

Geochemical anomalies in two sulfide-bearing waste disposal areas: Fe, Cu, Zn, Cd, Pb, and As in contaminated waters and snow, Kemerovo and Chelyabinsk regions, Russia

Sulfide-bearing mill wastes are sources of high concentrations of acid, soluble metals, Sb, and As. Contents of Cu, Zn, Fe, Pb, Cd, As, and Sb in wastes of the Belovo Zn-processing and the Karabash mineral-processing plants (Russia) exceed the average content in the upper continental crust and background soils. High-dissolved metal and As concentrations are found in acid drainages, which form as a result of interaction between sulfide wastes and water. Monitoring research using geochemical and geophysical methods was performed to evaluate the contamination of the surrounding area (water and bottom sediments in the contaminated rivers and snow cover). Zones of geochemical anomalies were identified where the concentrations of Fe, Cu, Zn, Cd, Pb, and As are 2–3 orders of magnitude higher than in drinking water standards (for rivers) and background levels (for snow). The use of geophysical methods allowed us to prove penetration of drainage solutions into the groundwaters. The total environmental damage caused by the pollution of water and land resources in the Belovo Zn-processing plant waste disposal area amounted to $156 million at the time of 2011, and could reach $480 million by 2030, if steps are not taken in recycling and remediation of disturbed areas.

Rock Characteristics and Ball Mill Energy Requirements at Goldfields Ghana Limited, Tarkwa Gold Mine (TGM)*

Mineral processing plants often experience changes in throughput; blending patterns, and rock properties. These changes can have great impact on milling operations. As mining progresses, new deposits are discovered, which may have different characteristics from the designed plant parameters, a situation requiring re-assessment of the plant operating parameters. Goldfields Ghana Limited, Tarkwa Gold Mine (TGM), processes ores which occur in conglomerate reefs. The competence of the ore was observed to increase with increasing mining depth. Other rock properties such as porosity, micro-cracks and gold dissolution were also observed to change with depth. It therefore became necessary to conduct a study to ascertain the effect of changes in rock characteristics on the performance of the existing ball mill. The study characterized the mineralogy and rock characteristics of the ores being mined from three pits and the results were compared with design parameters. The parameters examined had deviated from the design; Work Index (WI) for example was lower than design and required simulation and adjustment. Samples taken at the same depth from each of the pits showed that Akontasi Pit has the most competent ores, followed by Kottraverchi Pit and then Teberebie Pit. Furthermore, throughput was the most sensitive variable and easiest to manipulate to achieve the energy draw required. Simulations showed that a plant throughput of about 1665 t/hr, instead of the current value of 1500 t/hr would be most suitable as an energy draw solution.

Optimization of an Iron Ore Washing Plant

The sustainable viability of a mineral enterprise depends on improving the concentrate quality, generating readily salable by-products, improving recovery, throughput, and reduction of unit cost rate and maximize the unit income rate and thereby unit profit rate. Closing down of iron ore mines due to environmental constraints spurred the captive iron ore washing plants to workon a custom plant mode and also recover the values from their slimy tails. This paper enumerates the difficulties faced by a captive iron ore fine washing plant [treating iron ore fines assaying Fe∼58% yielding sands assaying Fe>60%] due to raw material change yielding unsalable sands and discuss the importance of process plant audit for improving the mineral processing plant performance. Based on the base line study, laboratory tests on typical samples followed by short term modifications, retrofitting of downstream slime concentrating wet high intensity magnetic separators and dewatering of products could produce readily salable sinter grade [Fe>60%] and pellet grade[Fe>62.5%] with an overall increase of concentrate yield by 11.5%. Even the previous wash plant tails [which assayed Fe > 45%] may be reprocessed in the retrofitted slime processing VPWHIMS plant. The final tails assayed 38.60% Fe at weight % yield of 28.5. Efforts are on for utilizing the above tails in bricks- tiles manufacture. Also, R&D efforts to concentrate Fe values from above 38.60% Fe tails by Magnetizing roast followed by magnetic separations in bench scale has given encouraging results. Thus auditing not only improved the quality, quantity and rate of production of concentrate but mitigated the problem of tailing disposal. The investments were repaid within a year of operation and unit operating costs reduced by 20% with reference to base line data.

Effects of free cyanide and cuprous cyanide on the flotation of gold and silver bearing pyrite

At gold and silver mineral processing plants, cyanide species are always present in the process water recycled to flotation circuits, despite the cyanide destruction process. The effect of cyanide, in particular, cuprous cyanide on gold and silver flotation has not been well understood. In the present study, free cyanide and cuprous cyanide species were isolated and their effects on the flotation of a pyritic ore were evaluated. It was found that free cyanide depressed gold and silver flotation through their carrier, pyrite. Cuprous cyanide mainly in the form of Cu(CN)32− depressed pyrite flotation similarly as free cyanide. Electrochemical studies including open circuit potential (OCP), cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques were carried out to understand the underpinning depression mechanism of cyanide species on pyrite flotation using xanthate as collector. It was found that all surface electrochemical reactions were inhibited by either free cyanide or cuprous cyanide. The surface layer as a result of xanthate adsorption on pyrite was completely removed in the presence of these cyanide species, which was suggested to contribute to the hydrophilic pyrite surface.

Physicochemical modeling of galena flotation system

Quantitative physico-chemical models of minimum necessary xanthenes concentration of lead sulphide complete flotation can be derived by a perfect studying of pulp ionic structure, adjusting the sulphuric ores flotation parameters and modelling of minerals selectivity variables, using thermodynamic method of analysis for defining the behaviour of lead xanthenes surface state in solution, and finally these models should be proved by experimental investigations. The optimal pH values ensuring a complete flotation of galena are agree with the potential of zero or minimum charge of its surface, and the optimal composition of the collector sorption layer consisting both of chemisorbed xanthenes and physically adsorbed dixanthenes. In additional, it was obtained quantitative models for the necessary xanthenes concentration of lead sulphide complete flotation in the case of different oxidation products of galena surface in pH values from 7.0 up to 12.0. The models derived can be used as the criteria for functional units of automation systems to control and regulate the flotation process in mineral processing plants. All these should conduct to increasing of metals extraction degree with minimum chemical reagents consumption and providing good environmental protection.

Physico-chemical models of galena flotation system

Main idea to prevent the ground contamination by heavy metals is to extract them maximally with minimum consumption of chemical reagents. So, a perfect studying of pulp ionic structure, an adjustment of the sulphuric ores flotation parameters and modelling of minerals selectivity variables, by using the thermodynamic method of analysis, the behavior of lead xanthenes surface state in solution and experimental investigation results, allow obtaining quantitative physico-chemical models of minimum necessary xanthenes concentration of lead sulphide complete flotation.The optimal pH values, ensuring a complete flotation of galena agree with the potential of zero or minimum charge of its surface, and the optimal composition of the collector sorption layer consisting both of chemisorbed xanthenes and physically adsorbed dixanthenes.In additional, it was obtained quantitative models for the necessary xanthenes concentration of lead sulphide complete flotation in the case of different oxidation products from the galena surface in pH values from 7,0 up to 12,0.The models derived can be used as the criteria for functional units of automation systems to control and regulate the flotation process in mineral processing plants. All these should conduct to increasing of metals extraction degree with minimum chemical reagents consumption and providing good environmental protection.