Depressant Dosage Research Articles

Aproveitamento econômico das lamas de ferro

A mineração iniciou suas atividades lavrando depósitos de alto teor, sem preocupação em maximizar seu aproveitamento. Ainda hoje, milhões de toneladas de minerais úteis são descartados anualmente para as barragens de rejeitos. Nesse trabalho, foram realizados testes de deslamagem e flotação com lamas de minério de ferro, primeiramente em escala de bancada. Várias dosagens de coletor e depressor foram utilizadas. Os resultados promissores dos testes em escala de bancada levaram a testes em escala-piloto. Foi constatado que, com o processo de flotação catiônica reversa em colunas, utilizando-se dosagem mais elevada de depressor, consegue-se recuperação mássica da ordem de 60% e 80% de recuperação metálica, 9 a 12 % de Fe no rejeito, 0,55 % a 0,90 % de SiO2 no concentrado (SiO2+Al2O3 < 2,00 %), além de alta seletividade no processo. A utilização da flotação de ultrafinos é uma alternativa econômica para o aumento das recuperações nos empreendimentos mineiros. A flotação de ultrafinos também pode ser avaliada para a redução ou tratamento de efluentes descartados no meio ambiente.

Utilization of soluble starch as a depressant for the reverse flotation of diaspore from kaolinite

The utilization of a non-toxic natural polysaccharide, soluble starch, in the flotation of diaspore and kaolinite with emphasis on depression of diaspore in the reverse flotation of bauxite ores by using a Gemini cationic collector, is reported in this work. Firstly, the depressant effect of soluble starch was studied by pure mineral micro-flotation of diaspore and kaolinite as functions of the depressant dosage and pulp pH. The results show that soluble starch depresses diaspore much better than kaolinite. When pH is over 10, a satisfactory separation of the alumina and the silicate minerals can be approached. Moreover, micro-flotation tests of artificial mixed minerals and bench scale reverse flotation of the diasporic bauxite ore was complementing conducted. The non-charged starch is highly proved to be an effective and selective depressant for the reverse flotation of diaspore from the gangue minerals like kaolinite. By zeta potential measurement, adsorption studies and D-IR spectra analysis, the mechanism of interaction between starch and the diaspore surfaces is established, which is the formation of a five membered ring complexes on mineral substrates. The number of broken Al–O bonds of diaspore is much more than that of kaolinite, so the selectivity separation of diaspore from kaolinite in this system is feasible.

Improvement of Egyptian talc quality for industrial uses by flotation process and leaching

Talc is an industrial mineral that is widely used. It is always associated with other minerals, which determine the quality of talc samples for industrial purposes. Various operating variables control the natural floatability of talc. For enhancement of talc flotation, sodium hexametphosphate is used as a depressant for associated gangue minerals. In addition, oleic acid (in an equal mixture with kerosene) is used as an anionic collector. The results presented in this paper provided useful and important information on how to improve the quality of Egyptian talc, obtained from different sites, for industrial uses. The optimum conditions were obtained at pH=11, depressant dosage=1.0 kg/t, collector dosage=1.2 kg/t and pulp density=200 g/L. At these conditions, SiO2 assay increased from 54.10% to 54.94%, MgO assay increased from 29.90% to 31.76%, CaO decreased from 0.80% to 0.42%, Al2O3 decreased from 5.50% to 3.11%, Fe2O3 decreased from 8.20% to 7.24%, the whiteness increased from 75.4% to 83.7%, and the loss on ignition decreased from 6.64% to 5.21%. The mass recovery of final concentrate was 92.4%. The component recoveries of SiO2 and MgO (the major constituents of talc) in the final concentrate were 93.8% and 98.2%, respectively. More improvement of talc quality was obtained by leaching the final concentrate of flotation with a 10% diluted hydrochloric acid. The mass recovery of final product was about 85% of initial feed. In this final product, Fe2O3 decreased to 3.12%, CaO decreased to 0.38%, and Al2O3 decreased to 3.01%. The assay of SiO2 increased to 58.96%, MgO percent was nearly the same as in the final concentrate of flotation, the whiteness increased to 88.5%, and the loss on ignition decreased to 4.03%. The final product may be suitable for many industrial uses such as low-loss electronics (a type of ceramics), paints, rubber, plastics, roofing, textiles, refractories, insecticides and coating of welding rods.

The response of sulphide and gangue minerals in selected Merensky ores to increased depressant dosages

Depressants are added to flotation circuits to reduce naturally floatable gangue (NFG) present in ores, but under certain conditions have been shown to affect sulphide mineral recovery, particularly guar reducing the recovery of pyrrhotite. Copper sulphate is added to increase sulphide mineral recovery, but may also activate gangue particularly in the presence of dithiophosphate. This has also been shown to vary with ore type. Previous work has shown the usefulness of analysing reagents holistically, decoupling pulp and froth effects and assessing material recovered by true flotation and that recovered by entrainment separately. This work assesses the effect of copper activation on different ores and the ability of two classes of depressants, guar gum (guar) and carboxymethylcellulose (CMC) to reduce this effect and shows that by a depressant dosage of 300 g/t almost all the NFG had been removed from the concentrate. It also evaluates the effect of depressants on the sulphide minerals and shows that pyrrhotite was most affected.

Selectivity in phosphate column flotation

The objective of this work was the study of the selectivity of apatite flotation in a column by means of kinetic analysis. The recovery and apatite content in the concentrate were correlated to the collector dosage, depressant dosage and air flow rate. The test results were subjected to statistical analysis aimed at identifying the experimental conditions producing the best P 2O 5 content and recovery.

IMPROVEMENT OF EGYPTIAN TALC QUALITY FOR INDUSTRIAL USES BY FLOTATION PROCESS AND LEACHING

Talc is an industrial mineral that is widely used. It is always associated with other minerals, which determine the quality of talc samples for industrial purposes. Various operating variables control the natural floatability of talc. For enhancement of talc flotation, sodium hexametphosphate is used as a depressant for associated gangue minerals. In addition, oleic acid (in an equal mixture with kerosene) is used as an anionic collector. The results presented in this paper provided useful and important information on how to improve the quality of talc for industrial uses. The optimum conditions were obtained at pH = 11, depressant dosage = 1.0 kg/t, collector dosage = 1.2 kg/t and pulp density = 200 g/L. At these conditions, SiO2 assay increased from 54.10% to 54.94%, MgO assay increased from 29.90% to 31.76%, CaO decreased from 0.80% to 0.42%, Al2O3 decreased from 5.50% to 3.11%, Fe2O3 decreased from 8.20% to 7.24%, the whiteness increased from 75.4% to 83.7%, and the loss on ignition decreased from 6.64% to 5.21%. The mass recovery of final concentrate was 92.4%. The component recoveries of SiO2 and MgO (the major constituents of talc) in the final concentrate were 93.8% and 98.2%, respectively. More improvement of talc quality was obtained by leaching of final concentrate of flotation with 10% dilute hydrochloric acid. The mass recovery of final product was about 85% of initial feed. In this final product, Fe2O3 decreased to 3.12%, CaO decreased to 0.38%, and Al2O3 decreased to 3.01%. The assay of SiO2 increased to 58.96%, MgO percent was nearly the same, the whiteness increased to 88.5%, and the loss on ignition decreased to 4.03%. The final product is suitable for many industrial uses such as low-loss electronics (a type of ceramics), paints, rubber, plastics, roofing, textiles, refractories, insecticides and coating of welding rods.

Industrial use of nitrogen in flotation of molybdenite at the Sarcheshmeh copper complex

The Sarcheshmeh copper deposit contains 1 billion tonnes of ore averaging 0.7% copper and 0.025% molybdenum. It is located southeast of Iran and currently processes 41,000 t/d. Molybdenite as a by-product is recovered in two separate stages. First, a bulk copper–molybdenum concentrate is produced and in the second stage these two are separated. The recovery of molybdenite in the first and second stages is 65% and 85–90%, respectively. The yearly production of molybdenite concentrate varies between 3500 and 4000 t. Sodium sulphide is used as the depressant of the copper and iron bearing minerals which due to a rather high consumption (17.7 kg/t) constitutes one of the major cost items of the plant (i.e., 58% of total reagents cost). Nitrogen for the plant was supplied from an oxygen plant used for the smelter through a 1400 m long pipeline. After using nitrogen in the plant for a period of 21 months, the consumption of sodium sulphide was reduced from 17.7 to 14.2 kg/t at constant metallurgy. The reduction was lower than expected which was mainly due to the type of sodium sulphide used and the lack of any automatic instrument to control the depressant (sodium sulphide) dosage.

Optimization of flotation parameters for enhancement of grade and recovery of phosphate from low-grade dolomitic rock phosphate ore from Jhamarkotra, India

Sedimentary dolomitic phosphate ores are difficult to treat by flotation, and high-grade phosphate concentrates with high recoveries are difficult to obtain. The literature indicates that the reagents required for beneficiation of such ores are generally dictated by the nature of the gangue. In this paper, the optimum flotation parameters necessary for enhancing the grade and recovery of a typical low-grade dolomitic rock phosphate ore from Jhamarkotra, Rajasthan, are highlighted. The standard design-of-experiment (DOE) technique was used to obtain empirical models for both grade and recovery. The model equations were then used for optimizing the flotation parameters, including pH, percent solids, collector dosage and depressant dosage. Laboratory experiments demonstrated that a phosphate concentrate containing about 36% P 2 O 5 , with a recovery greater than 95%, can be obtained in a single-stage by the reverse flotation of carbonaceous minerals at the optimized conditions.

Use of MIMO models in spreadsheets for the control of a column flotation circuit

The objective was to determine operating protocols for a lead and silver column flotation cleaner being considered/or installation at Sunshine Precious Metals Inc. ’s Kellogg mill in Northern Idaho. In this column, tetrahedrite and galena were floated, and pyrite and other gangue minerals, including siderite and silica, were depressed. The procedure was to develop a dynamic simulation using a linear transfer function approach. The transfer function related cause-and-effect variables such as the influence of collector and depressant dosages on recovery and grades. Bench-scale flotation tests followed by pilot column testing provided the data used to develop a linear transfer function. The transfer function was derived using a spreadsheet. This model was applied to simulate how the flotation column could be made to respond to disturbances in feed grade. The results were that xanthate, zinc sulfate and sodium cyanide were found to be suitable controls for grade and recovery. Simulations showed the best sequence of manipulations of these reagents, and these sequences are useful for future operator training. The conclusion was that linear transfer functions were able to simulate lead and silver recovery, develop scenarios for operator training and provide a foundation for future on-line control.

Reverse magnesite flotation

The present investigation deals with the production, at bench scale, of a high purity magnesite concentrate by means of reverse cationic flotation as an alternative to the direct anionic flotation currently employed in a concentrator in Brazil. The specification of the presently produced concentrate, in terms of maximum SiO 2 content, is 0.30% (calcined basis) and the weight recovery of the circuit is approximately 84%. The aim of this study was to produce concentrates with SiO 2 content ≤ 0.20% (calcined basis) and weight recovery ≥ 84%. A two level factorial design was employed in the first stage to optimise the variables that affect the behaviour of the system. In the second stage, the best conditions defined in the first stage were utilised in a locked cycle test, with simulation of circulating load, to predict the stability of the circuit in a continuous process. The main variables investigated were: percent solids and pH of the pulp, collector (ether amine) dosage, depressant (corn starch) dosage and flotation residence time. The aim of the study was achieved and a concentrate with 0.17% SiO 2, at a weight recovery level of 92.17%, was produced in the tests with simulation of circulating load in a rougher - cleaner - recleaner circuit. Lower SiO 2 contents could be reached with a reduction in weight recovery.

Effect of different collector dose rates on cobalt segregation

Nkana Concentrator is the most important mineral processing unit of Zambia Consolidated Copper Mines (ZCCM) (soon to be privatised) which contributes about 65% of cobalt concentrates treated at the Nkana and Chambeshi Cobalt plants to produce high purity cobalt metal. However, it has of late been experiencing problems with the segregation of the bulk concentrates which contain an appreciable amount of copper which overloads the performance of the cobalt tankhouses. In an effort to improve the copper/cobalt separation at segregation stage, a number of new collectors have been put on trial tests with a view of replacing the traditional Sodium Ethyl Xanthate (SEX) which has been in use since the sixties. The intention is to possibly isolate a collector that will give improved recoveries and grades of both copper and cobalt to their respective concentrates at different flotation stages. In this work, a series of laboratory testworks were conducted using Senkol 26, a Xanthic ester, Senkol 45, a blend of alkyl dithiophosphate and Xanthates and Senkol 700, a thionocarbomate type, which were supplied by SENMIN of South Africa on Nkana Concentrator feed materials. The feed materials are from four different sources namely; Mindola, Chibuluma, South Ore Body (S.O.B.) and Central shafts. The tests were carried out to compare the performance of the collectors based on their dose rates and later their performance compared to the collector currently being used at Nkana Concentrator. SEX at the dose rates of 20 and 30 g/t gave lower cobalt loses of 17 and 11.2 %TCo respectively, whilst grades were also very low at 0.25 and 0.19 %TCo respectively. The Senkol collectors exhibited poor separation of cobalt from copper at all dose rates except for Senkol 26 which gave loses of 8 %TCo at grade 0.14 %TCo at 50 g/t of collector which was much better than the SEX. This work has also shown that there is no incentive in increasing the dose rate of SEX beyond 30 g/t as there was no improved separation of cobalt from copper at an optimum depressant dosage and pH. On the other hand, the separation performance of Senkol 26 improved with increasing collector dose rate. Senkol 45 exhibited an increase in the of cobalt lost to the copper concentrate as the dose rate of the collector increased while no significant changes were noted with Senkol 700.

Reduction of magnesia in nickel concentrates by modification of the froth zone in column flotation

The reduction of the magnesia (MgO) content in a nickel concentrate was investigated for a nickel sulphide ore from Western Australia. Tests were conducted using both a conventional flotation cell and a column flotation cell. The conventional flotation tests show that the use of magnesia depressants were effective in controlling the magnesia levels in the concentrate. Of the depressants tested carboxy-methyl cellulose (CMC) and guargum were found to be the most effective. All of the column flotation tests were performed using a 7.0 cm diameter column. Depression of magnesia was studied by modifying the froth phase chemistry of the column via the wash water system. This allowed large addition rates of flotation modifiers to be used economically compared to high dosages normally added to the pulp phase. The depressant dosages tested in the wash water were equivalent to 0.66, 2.6, 4.6 and 6.6 kg/t in the froth respectively. It was found that CMC is a more effective magnesia depressant than guargum when added to both the pulp and wash water. Excessive addition of CMC show no obvious effects on the nickel grade and recovery compared with guargum where further addition above the optimum dosage had a detrimental effect on nickel grade and recovery. It was also found that the wash water pH can have a positive effect on concentrate grade and recovery.

Isometric contraction and contractility in the intact mammalian ventricle

The developed tension, the time derivative of tension, and the time integral of tension of segments of cardiac muscle contracting isometrically under conditions of altered length and contractility have been studied. The result of an increase in fiber length when heart rate and contractility are constant is to increase the rate of tension development and relaxation without altering the duration of any phase of contraction. The maximal developed tension and the integral of tension are, therefore, increased in proportion to the rate of development and relaxation of tension. The infusion of epinephrine resulted in an increase in the rate of tension development and a decrease in the duration of contraction. Consequently, the developed tension and the integral of tension were increased to a lesser extent than was the maximal rate of tension development. The effect of severely depressant dosages of quinidine was to decrease the rate of tension development without a predictable alteration in the duration of contraction, resulting in a proportionate decrease in the developed tension and the integral of tension. Lesser degrees of depression were sometimes accompanied by a slight increase in the rate of tension development, although the developed tension and the integral were frequently decreased under those conditions. There is no necessary reason apparent why any one of the time functions of isometric tension should be more directly related to myocardial contractility than the others. The variable responses to inotropic interventions of these functions, therefore, poses a number of questions as to the definition and measurement of the contractility of the myocardium.