A crystal-chemical investigation of phases of relevance to lime-chromite roast reactions
Evaluation of a platinum group metal flotation re-cleaner stage performance and possible improvement
- Authors: Nheta, Willie , Mphahlele, Karabo
- Date: 2019
- Subjects: Platinum-group mineral , Flotation , Chromite
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/400038 , uj:33368 , Citation: Nheta, W. & Mphahlele, K. 2019. Evaluation of a platinum group metal flotation re-cleaner stage performance and possible improvement.
- Description: Abstract: South Africa has massive Platinum Group Metal (PGM) deposits found in Bushveld Igneous Complex (BIC). Due to depletion of Merensky reef, many companies are now treating UG2 reef which has a high chromite content which has negative impact in the smelting process of the platinum concentrates. Generally, PGMs are processed by rougher followed by cleaner and re-cleaner flotation banks and the final concentrate must contain less than 3% chromite. The effect of residence time and depressant dosage on PGM recovery and chromite entrainment on the recleaner stage was investigated by floating the feed to the re-cleaner banks using Dow froth 200, Cu2SO4, sodium isobutyl xanthate and carboxymethyl cellulose in a 3l Denver cell. It was found that extra 30g/t of depressant dosage (carboxymethyl cellulose) from standard conditions reduces the chromite content to 2.11% from 8.63% and only 37.54% of PGMs are lost to the recleaner tailings which are recirculated to the cleaner feed. The residence time was reduced by 15minutes from the normal residence time. The Malvern particle size analyzer results indicated that the increase in depressant dosage and decrease in residence time the finer the concentrate. By controlling the depressant dosage, amount of chromite content in the final concentrate can effectively be reduced to meet the required standards.
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Liberation analysis of South African middle group seam chromite ore processed with vertical shaft impactor crusher
- Authors: Maruli, Mashudu , Nheta, Wille
- Date: 2020
- Subjects: Chromite , Middle Group seam , Liberation
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/450662 , uj:39622 , Citation: Maruli, M. & Nheta, W. 2020. Liberation analysis of South African middle group seam chromite ore processed with vertical shaft impactor crusher.
- Description: Abstract: In this study, the impact of vertical shaft impactor (VSI) crusher on fine and ultrafine production during crushing of South African Middle group (MG) chromite seam was investigated. The chromite ore was subjected to size reduction with VSI crusher at varied rotor tip speed (30, 35 &40 Hz) and particle size distribution analysis was done on all the three products. The VSI crusher product particle size distribution indicated that as the VSI rotor speed was increased, the amount of ultrafine generated also increased. The product at rotor speed of 35Hz revealed a lower percentage of ultrafines at 6.16% in the -212+150μm and 0.85% in the -150+53μm particle size range. Ball mill product from the Plant was analysed and the results revealed that the ball mill is more efficient for chromite ore liberation as 84% of the -425+300μm was produced compared to the VSI which only produced 51.27% -425+300μm. However, the amount of ultrafines produced was high at 9.2% of -150+106μm size fraction, with most ultrafine particle size of 4.42% in the -53+26μm size fraction. The mineral liberation analysis conducted on the -425+300 and -300+212μm VSI crusher products indicated that the degree of chromite liberation was higher at 95% on the -300+212μm size fraction compared to 78% liberation on the -425+300 μm size fraction. From the liberation analysis conducted in this investigation, it can be concluded that VSI crusher has a greater potential in chromite size reduction as it has shown to produce a liberated product with reduced percentage of ultrafines. However more test needs to be done on the VSI residence time to improve the percentage mass of the required liberated product particle size.
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The Merensky Reef at Dwarsriver 372 KT with reference to the mineral chemistry and the platinum group minerals in the Merensky reef chromitite stringers
- Authors: Rose, Derek Hugh
- Date: 2012-06-06
- Subjects: Merensky Reef Chromitite Stringers , Mineralogical chemistry , Platinum group minerals , Chromite , Bushveld Complex (South Africa)
- Type: Thesis
- Identifier: uj:2538 , http://hdl.handle.net/10210/4992
- Description: M.Sc. , This study focuses on the Merensky Reef (MR) occurring within the Two Rivers Platinum mine property in the farm Dwarsriver 372 KT, on the Southern sector of the Eastern Limb of the Bushveld Complex. Five MR exploratory drill core intersections were obtained. Petrographic and mineral chemical characteristics of these drill core samples focused on the characterization of minerals like clinopyroxene, orthopyroxene, plagioclase, chromite and olivine. Data of the cryptic variation of orthopyroxene, plagioclase and chromite, from a 10 m interval (approximate thickness of the section studied); from footwall through the MR to the hangingwall lithologies at Dwarsriver are described in this study. Locally the vertical cryptic variation of these minerals is broadly consistent with regional trends of the RLS. The lateral variation (i.e. along strike) is less pronounced; however, locally these minerals appear to be chemically evolving moving to the south of the property. Footwall orthopyroxene compositions vary from a minimum of En66 and reach a maximum of En84. Those of the MR range from En71 to En85. Hangingwall orthopyroxene compositions range from En60 and reach a maximum of En80. Plagioclase compositions in the footwall units range from a minimum of An69 and reach a maximum of An85. Those of the MR range from a minimum of An35 to a maximum of An84. This wide range in plagioclase compositions is believed to be as a result of the increased presence of fluids within the MR interval. The hangingwall plagioclase compositions range from An64 to An84. By analogy of the Western Limb, where the lithologies of the Northwestern sector are believed to be proximal to the feeder of this limb; the local lateral variation in the present study suggests that the lithologies of either the Central or Western sectors are most probably proximal to the feeder for the Eastern Limb. PGM assemblages associated with and adjacent to the MR chromitite stringers were evaluated using an MLA. Data obtained from this technique is in broad agreement with regional studies of the MR. With the aid of wholerock PGE assays the MLA technique has proven to be a powerful tool in evaluating PGM assemblages relatively quickly, from a few carefully selected samples. The mineralogical associations of the PGM with the gangue and host minerals have shown three main associations. These are the associations of chromite, BMS and silicates with the PGM, of which the base metal sulfide (BMS) association is remarkable given that these have a relatively low modal abundance. The relatively high mineralogical association of the BMS with PGM has been explained by a model involving a base metal sulfide liquid which possibly scavenged chalcophile and siderophile elements. Chromite chemistry and modal analyses of MR secondary silicate phases, which peak adjacent to the chromitite stringers, suggests elevated fluid overprinting within and adjacent to the chromitite stringers. The upper chromitite stringers, however, have higher abundances of PGM phases that are believed to be secondary in origin relative to the basal chromitite stringers. Generally the PGM associated with the upper chromitite stringers are also bigger in size averaging 70 μm as opposed to 27 μm for those associated with the basal chromitite stringers. The increase in grain size of the PGM along with the higher modal abundance of secondary PGM phases associated with the upper stringers is believed to be as a result of fluids. These fluids although affecting both the upper and basal chromitite stringers, appear to have had a relatively higher influence on the upper chromitite stringers. The most common PGMs encountered in this study are isoferroplatinum, sperrylite, michenerite, maslovite, cooperite, laurite and braggite.
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