| 1. |
- Berglund, Gun
(författare)
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Pulp Chemistry in Sulphide Mineral Flotation
- 1991
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 33:1-4, s. 21-31
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Tidskriftsartikel (refereegranskat)abstract
- Variations in the oxidizing conditions of the pulp and their subsequent effects on flotation were examined for three types of natural sulphide ore, a complex pyrite ore, a sphalerite-galena ore and a chalcopyrite ore. Different gas mixtures ranging from pure nitrogen to pure oxygen were used to control the oxidizing conditions. The use of an oxygen rich flotation gas was found to be a suitable method for changing the oxidizing conditions and improving flotation under controlled conditions. The flotation results were correlated to the oxygen content and the redox potential, parameters which describe the pulp chemistry conditions.
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| 2. |
- Forsling, Willis, et al.
(författare)
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Use of surface complexation models in sulphide mineral flotation
- 1997
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 51:1-4, s. 81-95
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Tidskriftsartikel (refereegranskat)abstract
- Surface complexation modelling is introduced to investigate the surface reactions in a mixed galena and sphalerite flotation system. Computer-assisted calculations based on surface complexation modelling (SCM) are performed to obtain the mineral surface distribution of ethyl xanthate as well as carbonate and excess sulphide ions as a function of pH. The significance of pe is demonstrated by computing the mineral surface speciation in a flotation system with xanthate and excess of sulphide ions. The results are used to evaluate the influences of pH, pe, the concentration of xanthate, sulphide or carbonate ions to the mineral flotability. The flotation mechanisms in galena-sphalerite system are discussed based on SCM.
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| 3. |
- Forsmo, Seija, et al.
(författare)
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Influence of the olivine additive fineness on the oxidation of magnetite pellets
- 2003
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 70:1-4, s. 109-122
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Tidskriftsartikel (refereegranskat)abstract
- Olivine is used as an additive in Luossavaara-Kiirunavaara AB (LKAB) blast furnace pellets. The LKAB iron ore is magnetite which oxidizes to hematite during the sintering process. Olivine retards the oxidation of magnetite pellets if the threshold temperature of magnesioferrite formation is exceeded. In this study, we have developed a thermogravimetric measuring method to study the relationship between the olivine reactivity in green pellets and the olivine fineness. A less reactive olivine makes the pelletizing process more tolerant of excessively high temperatures in the green pellets during oxidation. The reactivity of olivine decreases when the amount of fine tail in olivine is decreased. The top size is limited by balling. Grinding tests in pilot scale show that if the olivine additive is ground in closed circuit with a ball mill keeping good control over the top size, the olivine fineness can be appreciably decreased without disturbing balling. The olivine reactivity can be decreased by 40% compared to the reference olivine in the production plant. Also, savings can be made on both the grinding energy and grinding media consumption. The results in both pilot scale and full production scale show that better oxidation in the grate due to a coarser olivine additive improves the low temperature reduction strength (LTD, ISO 13930) in pellets. The measuring method developed for the olivine reactivity enabled evaluation of different particle-sizing methods for olivine characterisation. The screening size fraction % - 45 mum showed a good correlation to olivine reactivity in green pellets within a very large measuring range. The correlation of laser diffraction analysis to the olivine reactivity showed, however, that the laser diffraction measuring method is affected too much by variations in the large particles.
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| 4. |
- Forssberg, Eric, et al.
(författare)
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Influence of different grinding methods on floatability
- 1988
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Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 22:1, s. 183-192
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Tidskriftsartikel (refereegranskat)abstract
- Investigations have been in progress since the middle of 1981 to prove and explain differences in the influence of conventional and autogenous grinding on the floatability of sulphide minerals. Techniques for liberation and particle shape studies under the microscope, and measurement of pulp chemistry as to redox potential and contents of free oxygen and various sulphur-carrying ions were tested on samples from batch tests, pilot plant runs and commercial practice. The phenomena observed can partly be explained in terms of liberation and chemical characteristics of the pulp.
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| 5. |
- Forssberg, Eric, et al.
(författare)
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Influence of grinding method on complex sulphide ore flotation: a pilot plant study
- 1993
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 38:3, s. 157-175
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Tidskriftsartikel (refereegranskat)abstract
- The present work deals with plant investigations on the influence of conventional and autogenous grinding methods in the floatation of a complex sulphide ore. The study includes the investigation of the particle size and shape analysis and the pulp chemical measurements-Eh, pH, O2 concentration of cations and anions, at several stages of the grinding and flotation circuits. The rougher floatation concentrates of the Cu-Pb and Zn circuits were analysed to evaluate the floatation behaviour of chalcopyrite, galena and sphalerite. The results indicate better liberation of minerals in coarse size fractions for the pulp ground by autogenous mill while conventional grinding shows higher degree of liberation in the fine size range. Metallurgical analyses of the final floatation concentrates shows higher recoveries of Cu, Pb and Zn for the pulp ground by autogenous milling. The grades of Cu and Pb were better with conventional grinding but the recoveries were less than those obtained by autogenous grinding. Several interesting observations concerning pulp chemistry (e. g. the concentrations of Fe ions is lower in pulps ground by conventional method than by autogenous means!) are discussed.
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| 6. |
- Gao, Ming-Wei, et al.
(författare)
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Power predictions for a pilot scale stirred ball mill
- 1996
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Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 44-45, s. 641-652
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of a stirred ball mill to grind to a certain product size efficiently depends strongly on the power intensity in the milling chamber. The dependence of power intensity on stirrer speed, slurry density, bead density and the amount of dispersant added to the feed was investigated using a 6-litre 11-kW horizontal stirred ball mill fitted with perforated disks as stirrers. Dolomite was ground at a fixed volumetric flow rate, but with slurry densities ranging from 65 to 75 percent by weight, stirrer speeds from 805 to 2253 rpm, bead densities from 2.5 to 5.4 g/ml and the dispersant level from 0.5 to 1.5 percent of dry solids. Three levels of the four variables were used in 27 continuous milling tests, set up as one-third of a 34 factorial design. All factors affected the power draft in a highly significant way. Speed, and to a lesser extent slurry density, were the dominant factors with significant non-linear effects. A six-term model, incorporating all significant effects, predicted the experimental results with an accuracy of about 12%. Increasing the power accelerated size reduction dramatically with only a small change to the energy efficiency of the process.
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| 7. |
- Gao, Ming-Wei, et al.
(författare)
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Study on the effect of parameters in stirred ball milling
- 1993
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 37:1, s. 45-59
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-fine grinding involves a large number of parameters in its operation. In this paper, four important parameters of the Drais stirred ball mill, i.e., the bead density, slurry density, mill speed, and the effect of dispersant were selected for investigation. The experimental work was based on a factorial design and 27 milling tests were conducted. It is found that the bead density has an optimum value of 3.7 g/cc in this investigation. A lower slurry density and a smaller amount of dispersant appear to be better conditions. The mill speed should be as high as possible within the speed limit tested in this work for the best process efficiency.
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| 8. |
- Kalinkina, Elena V., et al.
(författare)
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Sorption of atmospheric carbon dioxide and structural changes of Ca and Mg silicate minerals during grinding : I. Diopside
- 2001
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 61:4, s. 273-288
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Tidskriftsartikel (refereegranskat)abstract
- Processes which occur during dry grinding of the magnesium and calcium silicate minerals enstatite MgSiO3, åkermanite Ca2MgSi2O7 and wollastonite CaSiO3, have been studied with the use of diffuse reflectance Fourier transform infrared spectroscopy (DRIFT), powder X-ray diffraction, 29Si MAS-NMR spectroscopy, CO2-content analysis, and BET surface area measurements. It has been found that the extensive sorption of atmospheric CO2 (carbonization) by the ground mineral that was reported earlier for diopside CaMgSi2O6 also occurs for the minerals included in this study. The shape and position of the double peak of the CO32--group in the 1430-1515 cm-1 region in the FT-IR spectra of ground minerals are similar to that of ground diopside. CO2-content analysis and BET surface area measurements show that carbonate groups are present not only at the surface but also in the bulk of the ground minerals. The degree of carbonization of silicate depends on its calcium content. The higher the fraction of Ca in octahedral positions in the silicate structures, the higher the degree of carbonization. For synthetic wollastonite CaSiO3, which is a pure calcium silicate, the degree of carbonization is 102.6 mg CaCO3 per gram of sample after 36 h of grinding. The structure of silicate appears to be less important for the degree of carbonization during grinding.
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| 9. |
- Kalinkina, Elena V., et al.
(författare)
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Sorption of atmospheric carbon dioxide and structural changes of Ca and Mg silicate minerals during grinding: II. Enstatite, åkermanite and wollastonite
- 2001
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 61:4, s. 289-299
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Tidskriftsartikel (refereegranskat)abstract
- Processes which occur during dry grinding of the magnesium and calcium silicate minerals enstatite MgSiO3, åkermanite Ca2MgSi2O7 and wollastonite CaSiO3, have been studied with the use of diffuse reflectance Fourier transform infrared spectroscopy (DRIFT), powder X-ray diffraction, 29Si MAS-NMR spectroscopy, CO2-content analysis, and BET surface area measurements. It has been found that the extensive sorption of atmospheric CO2 (carbonization) by the ground mineral that was reported earlier for diopside CaMgSi2O6 also occurs for the minerals included in this study. The shape and position of the double peak of the CO32--group in the 1430-1515 cm-1 region in the FT-IR spectra of ground minerals are similar to that of ground diopside. CO2-content analysis and BET surface area measurements show that carbonate groups are present not only at the surface but also in the bulk of the ground minerals. The degree of carbonization of silicate depends on its calcium content. The higher the fraction of Ca in octahedral positions in the silicate structures, the higher the degree of carbonization. For synthetic wollastonite CaSiO3, which is a pure calcium silicate, the degree of carbonization is 102.6 mg CaCO3 per gram of sample after 36 h of grinding. The structure of silicate appears to be less important for the degree of carbonization during grinding.
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| 10. |
- Kundu, T.K., et al.
(författare)
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Atomistic simulation of the surface structure of wollastonite and adsorption phenomena relevant to flotation
- 2003
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 72:1, s. 111-127
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Tidskriftsartikel (refereegranskat)abstract
- Atomistic simulation techniques have been used to calculate the surface structure and stability of wollastonite crystal and its adsorption behaviour in the presence of molecular and dissociated water, and two widely used collector head group molecules of methanoic acid and methylamine. Seven predominant surfaces have been modelled and their calculated surface energies correspond well with their preferred morphological domination. Surfaces are identified having fourfold and threefold coordination of surface silicon. Threefold surface silicon are stabilized by addition of hydroxyl ion on them and proton on surface oxygen. Stable surfaces thus obtained are subjected to surface Ca2+ replacement by 2H+ by transforming 2O2− to 2OH−. Surface energy and reaction energy values indicate wollastonite surface stabilized to a great extent by adsorbing water in dissociated form. The Ca2+ replacement from the first few layers of the surface is energetically more favourable in acidic condition. Three Miller indexed surfaces terminating with fully coordinated silicon were reconstructed to make the surface free of lone oxygen, and these surface cuts were chosen to carry out simulation work for adsorption of molecules. A comparison of surface energies revealed that all the surfaces become stabilized in the presence of added molecules but the presence of methylamine decreases surface energy to lowest values. Adsorption of dissociated water is preferred by {100} and {102} surfaces, while {001} surface adsorbs methylamine strongly as the results show highly negative adsorption energies. In terms of pure molecule adsorption, the preferred adsorption sequence for all the surfaces is methylamine>methanoic acid>water. For {100} and {102} predominant surfaces, the difference in adsorption energy values is not much and we conclude that the collectors having long-chain hydrophobic alkyl chain, the two head group molecules considered, cannot render enough hydrophobicity due to inadequate adsorption on wollastonite. Thus the presence of activators/modifiers in actual wollastonite flotation practice is substantiated.
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