Processing Of Low-grade Ores Research Articles

Population balance based modelling of nickel laterite agglomeration behaviour

Agglomeration of fine mineral particles as a precursor to heap leaching is an important means of enhancing leaching rates and metal recoveries, particularly in processing low grade ores. In this paper, the modelling of a batch drum agglomeration process applied to nickel laterite using population balance model is explored. The coalescence kernels which are linked to feed material and agglomerator operating conditions are reviewed. The use of a physically based coalescence kernel which relates agglomerate layer thickness to binder content and agglomerate consolidation shows great promise for the modelling of the agglomerate size distribution of nickel laterite ore. The model parameters were then used to predict the effect of operating parameters such as binder content on agglomerate size distribution.

Steady-State Simulation of Hybrid Nickel Leaching Circuit Using Syscad

There is an increasing focus on the hydrometallurgical processing of nickel-rich laterite ore due to declining global reserves of nickel sulphides. The development of new technology called hybrid nickel leaching circuit that encompasses pressure acid leaching (PAL) and atmospheric leaching (AL) processes has made processing of low-grade ores (with nickel content as low as 0.5%) a possibility. However, significant challenges exist in lowering the operating costs for this new process including the reduction of sulphuric acid and the energy required to heat the pulp to the desired temperature (250oC). To address above challenges, a detailed understanding of the process chemistry together with interactions between unit operations feeding into and out of the system is required. To accomplish this, a software package with powerful convergence algorithms, control loops, background chemical equilibrium, aqueous thermodynamics and extensive databases containing information on the physical properties of desired components is needed. Using such a process simulator, it is possible to produce numerically rigorous mass/energy balances for as many variations of the model as desired. This allows enhanced analysis of the flowsheet, better process design, and ultimately, better business decisions. Although there have been several studies on hybrid circuit, most of these studies have only dealt with the effects of process variable such as temperature, acidity, pulp density. Thus far, no complete study has been published on the modelling of different proposed scenarios. The present work constitutes an effort towards bridging this gap. A number of possible flowsheeting combinations were simulated using a commercial software packages SysCAD, and some optimal configurations were identified.

Dissolution of wollastonite and its flotation and surface interactions with tallow-1,3-diaminopropane (duomeen T)

Wollastonite finds an important place among industrial minerals due to its high chemical and thermal resistance and also as a substitute for asbestos. With the depletion of high-grade ores and increased demand, it becomes inevitable to process low-grade ores. Flotation can be employed effectively for processing these ores. Flotation behavior of wollastonite was studied using tallow-1,3-diaminopropane as collector in the Hallimond micro-flotation cell. The flotation recoveries obtained were correlated with contact angle measurements. Dissolution studies clearly bring out the incongruent dissolution of wollastonite, resulting in a silica rich layer on the surface of the mineral. The release rates of calcium and silicon decrease with the particle size. Maximum flotation obtained at 1 × 10 −5 M diamine concentration. DRIFT studies indicate that the intensity of alkyl chain bands increases with increasing diamine concentration, thus corroborating increased presence of diamine on wollastonite resulting in maximum contact angle and flotation recovery. Surface free energy values of wollastonite were determined by different approaches using contact angle data of well-defined components of polar and apolar liquids. An attempt has been made to correlate between the flotation response and the surface free energy values of wollastonite in the presence diamine.

Estudo comparativo entre dois sistemas de aeração de coluna de flotação

O aumento na demanda de recursos naturais não renováveis e a exaustão de jazimentos com teores dos elementos de interesse mais elevados têm colocado a indústria mineral frente ao desafio de beneficiar minérios mais complexos e tendo de atender às especificações de mercado, que estão cada vez mais restritas. Considerando essa realidade, novos equipamentos e técnicas para a concentração de minérios têm sido desenvolvidos nos últimos anos. Entre esses desenvolvimentos, a flotação em coluna tem-se mostrado adequada para o tratamento de minérios mais complexos, com teores mais baixos e granulometria de liberação mais fina. O desempenho da coluna de flotação está intimamente relacionado com o controle do tamanho e uniformidade de distribuição das bolhas de ar introduzidas em sua base. Em função disso, diversos tipos de sistemas de aeração têm sido disponibilizados no mercado mundial. Esse trabalho foi realizado com o objetivo de comparar os dois tipos de aeradores que têm sido empregados na indústria mineral brasileira atualmente, ou seja, o aerador tipo lanças perfuradas, que utiliza uma mistura água/ar sob pressão, e o de um único orifício na sua extremidade, que utiliza somente ar. Os resultados obtidos mostram que, nas condições usuais de operação das colunas de flotação, a utilização do aerador tipo água-ar acarreta a geração de bolhas com diâmetro médio menor que os obtidos com o aerador do tipo ar, indicando sua utilização nos processos industriais onde o tamanho e a uniformidade das bolhas geradas sejam fatores decisivos para obtenção de um bom desempenho metalúrgico.

Full length article

Gold has played an important role in the settlement and economics of the United States. Commercial production from 24 states totaled more than 420 million troy ounces (13,000 metric tons) from 1804 through 1995. There were, no doubt, early undocumented discoveries by Native Americans, but the first records are those from the mid-1600's in the east and from the 1770's in the west. Commercial production began in 1804 in North Carolina and spread among several Appalachian states in the 1820's and 1830's as placer deposits were discovered and exploited. After peaking in the 1830's and 1840's, Appalachian production began to decline as deposits were worked out and as miners moved westward in response to the news of the discoveries in California in 1848. Appalachian production virtually ceased with the Civil War while production from California and adjacent states remained at several millions of ounces per year. As the California Gold Rush waned, new discoveries brought the Rocky Mountain states, South Dakota, and Alaska into prominence. Local, state and total production responded to time of discovery, extent of placers, labor availability, technology, government mandates and, of course, the price of gold. By 1900, the major gold rushes had occurred and most of the major producing districts were defined; however, the fixed price of gold (since 1837) provided a decreasingly attractive incentive for more exploration and exploitation. The rise in the price of gold, during the Depression provided a powerful incentive to increase gold production, but one that was cut short by War Production Board Order L-208 which closed the gold mines in 1942. In the post-war period, the fixed price, combined with the prohibition of American gold ownership, again proved to be a disincentive and gold production dropped. The era of free gold price that began in 1968, followed by the permission for Americans to again own gold, brought new interest in gold with prices rising briefly in 1980 to US$850 per ounce and remaining above US$350 per ounce through 1995. This higher price, combined with the technology for bulk mining and processing of low grade ores, provided incentive for new exploration and exploitation. Consequently, gold production soared above 10 million ounces per year in the early 1990's with 65% coming from Nevada. There has been a general decrease in the grade of gold ores since the early 1900's and significant changes in the methods of recovery. Despite the decreasing grade, the reserves of recoverable gold have more than doubled since the early 1970's.

Discussion

Gold has played an important role in the settlement and economics of the United States. Commercial production from 24 states totaled more than 420 million troy ounces (13,000 metric tons) from 1804 through 1995. There were, no doubt, early undocumented discoveries by Native Americans, but the first records are those from the mid-1600's in the east and from the 1770's in the west. Commercial production began in 1804 in North Carolina and spread among several Appalachian states in the 1820's and 1830's as placer deposits were discovered and exploited. After peaking in the 1830's and 1840's, Appalachian production began to decline as deposits were worked out and as miners moved westward in response to the news of the discoveries in California in 1848. Appalachian production virtually ceased with the Civil War while production from California and adjacent states remained at several millions of ounces per year. As the California Gold Rush waned, new discoveries brought the Rocky Mountain states, South Dakota, and Alaska into prominence. Local, state and total production responded to time of discovery, extent of placers, labor availability, technology, government mandates and, of course, the price of gold. By 1900, the major gold rushes had occurred and most of the major producing districts were defined; however, the fixed price of gold (since 1837) provided a decreasingly attractive incentive for more exploration and exploitation. The rise in the price of gold, during the Depression provided a powerful incentive to increase gold production, but one that was cut short by War Production Board Order L-208 which closed the gold mines in 1942. In the post-war period, the fixed price, combined with the prohibition of American gold ownership, again proved to be a disincentive and gold production dropped. The era of free gold price that began in 1968, followed by the permission for Americans to again own gold, brought new interest in gold with prices rising briefly in 1980 to US$850 per ounce and remaining above US$350 per ounce through 1995. This higher price, combined with the technology for bulk mining and processing of low grade ores, provided incentive for new exploration and exploitation. Consequently, gold production soared above 10 million ounces per year in the early 1990's with 65% coming from Nevada. There has been a general decrease in the grade of gold ores since the early 1900's and significant changes in the methods of recovery. Despite the decreasing grade, the reserves of recoverable gold have more than doubled since the early 1970's.

Gold production history of the United States

Gold has played an important role in the settlement and economics of the United States. Commercial production from 24 states totaled more than 420 million troy ounces (13,000 metric tons) from 1804 through 1995. There were, no doubt, early undocumented discoveries by Native Americans, but the first records are those from the mid-1600's in the east and from the 1770's in the west. Commercial production began in 1804 in North Carolina and spread among several Appalachian states in the 1820's and 1830's as placer deposits were discovered and exploited. After peaking in the 1830's and 1840's, Appalachian production began to decline as deposits were worked out and as miners moved westward in response to the news of the discoveries in California in 1848. Appalachian production virtually ceased with the Civil War while production from California and adjacent states remained at several millions of ounces per year. As the California Gold Rush waned, new discoveries brought the Rocky Mountain states, South Dakota, and Alaska into prominence. Local, state and total production responded to time of discovery, extent of placers, labor availability, technology, government mandates and, of course, the price of gold. By 1900, the major gold rushes had occurred and most of the major producing districts were defined; however, the fixed price of gold (since 1837) provided a decreasingly attractive incentive for more exploration and exploitation. The rise in the price of gold, during the Depression provided a powerful incentive to increase gold production, but one that was cut short by War Production Board Order L-208 which closed the gold mines in 1942. In the post-war period, the fixed price, combined with the prohibition of American gold ownership, again proved to be a disincentive and gold production dropped. The era of free gold price that began in 1968, followed by the permission for Americans to again own gold, brought new interest in gold with prices rising briefly in 1980 to US$850 per ounce and remaining above US$350 per ounce through 1995. This higher price, combined with the technology for bulk mining and processing of low grade ores, provided incentive for new exploration and exploitation. Consequently, gold production soared above 10 million ounces per year in the early 1990's with 65% coming from Nevada. There has been a general decrease in the grade of gold ores since the early 1900's and significant changes in the methods of recovery. Despite the decreasing grade, the reserves of recoverable gold have more than doubled since the early 1970's.

Applications of biological processes in mineral processing

Biological processes have been attracting attention in mineral processing recently due to lower operating costs and their possible applications in processing low-grade ores that are not easily concentrated using conventional processes. Adhesion of microbes to particle surfaces can alter the hydrophobicity of minerals markedly. Such surface modification to impart hydrophobicity or hydrophilicity is used in flotation of sulfide as well as nonsulfide minerals. Microbes are also able to assist dissolution of precious metals from insoluble solids. In some systems they also cause excellent flocculation of fine particles. In addition, certain microbes possess the ability to adsorb toxic heavy metal ions, and hence are finding applications for environmental protection. These processes (microbially induced flotation, flocculation and biosorption) are examined in this paper. While certain microbes will adhere to some surfaces and not to others, others will adhere to all and some to none. Interestingly, even the same microbe, with fimbriae which are its discriminating tethers, can undergo marked changes in its preference to adhere to surfaces upon selectively removing some of the fimbriae. In this regard, the role of changes in surface properties brought onto microorganisms and the minerals due to microbe-mineral interactions also needs to be recognized. Clearly, understanding the mechanisms involved in all these processes will prove useful for developing new and improved biomineral processing techniques.

Microbial ore leaching in developing countries

Microbial leaching processes are being considered as an economical and technically viable alternative for processing low-grade ores and wastes in developing countries. The research and development programs in developing countries aim to design appropriate technologies for the large scale exploitation of local mines. In most cases mining companies, universities, research institutes and governmental and international agencies are all involved, demonstrating a widespread confidence in the application of this technology.