Recovering the lost gold of the developing world : bibliographic database

This report contains a library of 181 references, including abstracts, prepared for Project R 7120 "Recovering the lost gold of the developing world" funded by the UK' s Department for International Development (DFID) under the Knowledge and Research (KAR) programme. As part of an initial desk study, a literature review of gold processing methods used by small-scale miners was carried out using the following sources; the lSI Science Citation Index accessed via Bath Information and Data Services (BIDS), a licensed GEOREF CD-ROM database held at the BGS's Library in Keyworth and IMMage a CD-ROM database produced by the Institution of Mining and Metallurgy held by the Minerals group ofBGS. Information on the search terms used is available from the author

Modelling, simulation and optimization of the comminution and flotation circuits of platinum for sustainable mineral processing

Abstract: The quantum of minerals extracted from ore is critical for the success of mineral processing, hence the necessity to optimize the process flows in order to recover as much minerals as possible. The aim of this research was to identify bottlenecks and recovery-hampering factors within the comminution and flotation circuits of the concentrator plant at a platinum processing company in Zimbabwe. Modelling and simulation of the circuits were carried using Arena and Limn simulation software to optimize the process flows for improved throughput, maximum mineral recovery and enhanced efficiency and productivity. Alternative configurations of the layout of equipment were experimented on and compared with the original setup. The recommended reconfiguration of the circuits achieved increases of 2.97% in mineral recovery and 4 grams/ton in productivity resulting in a maximized output for the sustainable processing of platinum ore

The characterisation of a two stage flotation circuit treating a complex platinum and chromite ore

Bibliography: pages [144]-152.The methodology was developed to characterise the complex MF2 circuit at Impala Platinum Ltd. The circuit was divided into individual units and each unit was evaluated over a period of time. The performance of each unit in terms of platinum, palladium, rhodium and chromite recoveries was determined by sampling around the unit. The changes in ore floatability characteristics were monitored by carrying out batch flotation tests on samples taken from the feed to each unit. The mixing in the units was characterised by performing residence time distribution studies on the units. The batch flotation results were modelled using a distributed rate approach. The model yielded parameters which were associated with three floatability classes, viz. a fast floating, a medium floating and, a slow floating class and a class for valuable minerals which did not float. The model was not able to discriminate between mineralogical and particle size effects on flotation rates. This would be an important prospect of a future investigation. The rate constants associated with each floatability fraction obtained from the batch flotation together with residence time distribution results were used in association with the actual recoveries from each unit. These factors were used to simulate the performance of the circuit. The same model was used for all the units and the differences in cell design as indicated by hydrodynamics, aeration rate, etc. were accounted for in the· mixing parameters and flotation rates. This procedure to simulate plant performance was successfully applied to three different circuits thus confirming its validity. The difference in the three simulated circuits was in the cleaning stages. Among other things, the simulation shows that the best ·platinum, palladium and rhodium recoveries could be obtained if the greatest cleaning capacity was situated in the secondary stage of the circuit. Although the changes in the circuit configuration could be simulated to establish the effect on the platinum, palladium and rhodium recoveries, the chromite recovery could not be simulated. This is due to the fact that chromite is mainly floated by entrainment which is not incorporated into the model. Since the chromite recovery is crucial for the design of optimum cleaning circuits in the flotation of UG-2 ore, research needs to be done to quantify the entrainment phenomenon

Computer aided Design and Optimization of Mineral Processing Plants by a State of the Art Simulator

Tata Research Development and Design Centre (TRDDC) has developed a state of the art mineral processing simulator called SimL8. It performs modelling, simulation and optimisation functions and provides viable strategies for enhancement of the performance of mineral processing plants. A number of case studies on plant diagnostics, grinding,classification, flotation and pressure filtration are taken up to demonstrate the utility of modelling and simulation on SimL8 platform

Assessment of reagent and regrinding in a flotation circuit

Laboratory flotation tests using a bottom driven cell are reproduced with a high level of confidence. These types of laboratory data are used to investigate the effect of reagent and regrinding of coarse particles in an industrial flotation circuit. The addition of collector (BX) has a significant effect on the flotation response of chalcopyrite in the scavenger bank. The reconstructed recovery-time curve (combine products) is greater than that of the rougher tailings (scavenger feed) prior to reagent addition. By adding collector (BX) in the scavenger feed, the ultimate recovery of chalcopyrite increases 20% which means an increase of 1.7% of chalcopyrite recovery in the scavenger feed. Meanwhile, the reagrinding of coarse particles shows a detrimental effect on the collectorless flotation of an initially hydrophobic chalcopyrite sample. Cyclone underflow, 80% recovery at pH 7.7, was decreased to 40% after regrinding at the same range of pH. The chalcopyrite flotation response immediately after regrinding is severely retarded. It is assumed that the centrifugal action of the cyclone is another important factor restoring the chalcopyrite hydrophobic flotation due to the oxygenation of the slurry. Therefore, additional preconditioning time after a regrinding stage should have a positive change in the recovery of chalcopyrite. The overall flotation response before and after the regrinding stage showed that the cyclone underflow response is slightly slower compared with the combine feed in the first four minutes of flotation. This behavior is related to changes on surface chemistry because of the regrinding of coarse particles

UPRAVLJANJE POTROŠNJOM ENERGIJE I SIMULACIJA OPTIMIZIRANIH RADNIH UVJETA KUGLIČNIH MLINOVA KORIŠTENJEM MORRELLOVA MODELA SNAGE: STUDIJA SLUČAJA

The amount of comminution or fineness of minerals in a mill can be described by various parameters, the most important of which is d80 (80% passing size). The purpose of this study is to investigate and simulate the optimal operating conditions of a ball mill in a copper processing plant. The actual operating conditions in the intended mill are performed with a 300 tph tonnage, a 267 second retention time, and a discharge d80 = 53 μm. Laboratory studies showed that the optimal economical and metallurgical recovery of copper in this plant is achieved in 65 μm ≤ d80 ≤ 75 μm with Flotation Recovery (R) = 90.16%, Economical Efficiency (EE) = 93.04% and Separation Efficiency (SE) = 88.64%. In this study, having the optimal d80 for the concentration unit, the mill data, and utilizing Excel Software and the Morrell method, first the total power for the optimal set of d80 was calculated, which is equal to 7790 to 8005 kW. Then, according to these power values, the corresponding retention times were calculated, which are equal to 236 and 247 seconds respectively. Finally, utilizing the retention time-tonnage relationship and taking into account the specific filling of the mill, the optimal corresponding tonnages to the obtained retention times were calculated, ranging from 324 to 340 tph. The results of these studies showed that by reducing the level of comminution from d80 = 53 μm to 65 μm ≤ d80 ≤ 75 μm, in addition to increasing flotation efficiency to R = 90.16%, EE = 93.04% and SE = 88.64%, about 4.21% to 7.09% energy savings and an 8.00% to 13.33% tonnage increase will occur.Stupanj sitnjenja ili finoća mljevenih minerala u mlinu može se opisati raznim parametrima, od kojih je najvažniji d_80 (80 % prolazi kroz otvor sita). Svrha je ovoga rada istražiti i simulirati optimalne uvjete rada kugličnoga mlina u postrojenju za preradu bakra. Stvarni radni uvjeti u predviđenome mlinu izvode se s kapacitetom od 300 t/h, vremenom zadržavanja od 267 sekundi i izlaznom veličinom d_80 = 53 μm. Laboratorijske studije pokazale su da se optimalna ekonomičnost i metalurško iskorištenje bakra u ovome postrojenju postiže u rasponu 65 μm ≤ d_80 ≤ 75 μm s flotacijskim iskorištenjem (R) = 90,16 %, ekonomskom učinkovitošću (EE) = 93,04 % i učinkovitošću odvajanja (SE) = 88,64 %. U ovoj studiji, poznavajući optimalni d80 za jedinicu koncentracije i podatke iz mlina te korištenjem Excel softvera i Morrell metode, najprije je izračunana ukupna snaga za optimalni skup d80, koja je jednaka 7790 do 8005 kW. Zatim su, prema ovim vrijednostima snage, izračunana odgovarajuća vremena zadržavanja, koja su jednaka 236 odnosno 247 sekundi. Zaključno, korištenjem odnosa vremena zadržavanja i kapaciteta te uzimajući u obzir specifično punjenje mlina, izračunani su optimalni odgovarajući kapaciteti sukladno dobivenim vremenima zadržavanja u rasponu od 324 do 340 t/h. Rezultati ovih istraživanja pokazali su da smanjenjem stupnja usitnjavanja s d80 = 53 μm na 65 μm ≤ d_80 ≤ 75 μm, osim povećanja učinkovitosti flotacije na R = 90,16 %, EE = 93,04 % i SE = 88,64 %, doći će do uštede energije od oko 4,21 % do 7,09 % i povećanja kapaciteta od 8,00 % do 13,33 %

Dynamic simulation of a modular flotation plant

The aim if this thesis work is to develop a dynamic simulator tool of a modular flotation plant with the final purpose of the simulator to be used as a training tool for operators. The thesis report describes basic theory about froth flotation process, process modelling, automated control and the development process of the final simulator tool. The simula-tor tool was developed for Outotec Oy® Finland based on their designs and calculations. The simulator was developed with the aid of three different programs: HSC Sim 9, SIE-MENS PCS 7, Virtual Experience Manager and Virtual Experience Client. HSC Sim per-forms dynamic simulation of the flotation process. SIEMENS PCS is the Distributed Control System (D.C.S.) where the automated control, the human machine interface and the instrumentation are created. The final training platform development and training exercise creation was done using Virtual Experience Manager. Virtual Experience Client was used to activate the training simulator tool. The final version of the training simulator was capable of simulating the required flota-tion flowsheet with the input ore-feed. It can be used as a base platform on which further development regarding instrumentation, flotation circuit and mineral processing can be modified to fit different configurations as required. Further development of the simula-tor requires improvement on the capabilities of the programs used for the development

The effect of circuit configuration on regrind circuit performance

Includes bibliographical references (leaves 120-123).It was identified that potential improvements in recoveries were to be found in the better use of the regrind stages at a number of Anglo-Platinum concentrators. Historically, these concentrators used to operate in an open circuit configuration, over a relatively short period, the circuits were changed to closed circuit configurations because of the reported benefits of operating in this configuration. The effect of closing the circuit had, however not been quantified in these concentrators. This dissertation looks at quantifying the effects of each configuration with the purpose of drawing meaningful comparisons between them. The circuit configurations studied are open circuit, I-stage and 2-stage closed circuit configurations. The primary difference between these configurations is the network of hydrocyclones. This study pays special attention to the effect of cyclone performance on the regrind circuit performance. Comparisons were made between the open and the 2-stage closed circuits in three concentrators, and surprisingly the closed circuit did not show any improvement over the open circuit configuration from a combination efficiency perspective. The cyclones performance was analysed, and it was observed that the cyclones were operating inefficiently, most likely because the cyclones employed were not appropriate for regrind circuits. A further comparison was made between the I-stage and 2-stage circuit configurations and the I-stage closed circuit configuration proved to be more efficient than the 2-stage closed circuit configuration. Simulations were conducted to predict the performance of the circuit configurations by using more appropriate cyclones which are smaller in size. These cyclones are currently being used in a similar application in another concentrator. The simulations indicated that significant improvements in comminution performance could be realised with the utilisation of more appropriate cyclones, to achieve the closed circuit configuration

A flotation control system to optimise performance using peak air recovery

Automatic control of industrial flotation cells and circuits presents a set of significant challenges due to the number of variables, the sensitivity of flotation cells to variation in these variables and the complexity of predicting flotation performance and/or developing a strategy for optimisation. Air recovery, a measure of froth stability, has been shown to pass through a peak as flotation cell aeration increases. Furthermore, the air rate at which the peak air recovery (PAR) is obtained results in optimal flotation performance, whether improved concentrate grade, recovery or both grade and recovery. Peak air recovery, therefore, presents a clear optimising control strategy for the operation of flotation cells which is generic to all flotation cells regardless of position in the flotation circuit. In this study, a novel control system based on PAR is developed and demonstrated using a large continuous laboratory flotation cell. In this study, a direct search optimisation algorithm based on the GSS (generating set search) methodology was developed using a 70 l continuous flotation cell operating with a two-phase system (surfactant solution and air only). Characterisation of the laboratory system showed that it was stable for up to 6 h and exhibited a reproducible peak in air recovery. A dynamic model of the response of the system with regards to changes in air recovery was developed that allowed simulations of the proposed optimising control system to be carried out. The optimisation algorithm was then applied to the experimental system. The trialled GSS algorithm was shown to find the PAR air rate when starting above, below and at the PAR air rate, and additionally with a disturbance introduced into the system. While the direct search approach can be slow, it is simple and robust. This demonstrates an innovative approach to optimising control for froth flotation and is the first application of froth stability maximisation for flotation control