Mineral Processing Engineering

Sinter Plant Operation

The sintering process for the preparation of raw materials to be fed to the Imperial Smelting Furnace (I.S.F.) is rather diversified in its characteristics. In comparison to the other preparation process for zinc extraction, i.e., fluidized bed roasting, the sintering process enables the Imperial Smelting Process (I.S.P.) smelter to treat a variety of raw materials.

Process Control of Sintering Plant

Sulfide concentrates, oxide materials and I.S.F. dross are prepared in the proportioning bins (There are ten bins for raw materials.). The raw materials and flux are fed by separate variable speed belt conveyers consisting of computer controlled belt weighers.

Raw materials and crushed return sinter are then mixed and pelletized in mixing and conditioning drums. The moisture content of return sinter is controlled to within 2 – 3 % in the cooling drum as will be explained later. In the mixing drum, the moisture content of the mix is controlled to about 4 – 5 % which is very important for keeping good permeability of the feed mix to the sinter machine.

Feed mix thus uniformed in the preceding process is fed respectively into an ignition and a main layer hopper of the sintering machine by a reversible conveyer. The weight of

By |2018-11-16T06:23:03+00:00November 15th, 2018|Categories: Pyrometallurgy|Tags: |Comments Off on Sinter Plant Operation

Gearless Warp Around SAG Mill

For almost a decade now, very good operating experiences have been gained with a total of 28 gearless ring motor drives in the cement industry, driving tube mills with diameters of 2.5 to 4 meters with drive powers ranging from 3000 to about 5000kW. Why then did the mineral ore processing industry hesitate till 1980 to adopt this successful concept for their undisputably similar application on ball, semi-autogenous, and autogeneous mills? There are a number of good reasons in the eyes of conservative mill builders and operators, the most commonly cited ones of which are as follows:

  • No operating experience in this segment of specialized industry.
  • More severe environmental conditions in the wet ore grinding process.
  • An indifferent attitude of mill builders and electric motor manufacturers towards new drive technologies.
  • Limited confidence in solid-state power supply systems,such as frequency converters of the required size.

At this point, one should reflect on the reasons, why such large mills are considered to begin with. After all, one could avoid all the above problem areas by simply staying with smaller mill unit sizes. Under competitive pressures of free markets however, grinding efficiencies and specific energy consumption become key factors in the selection of new

By |2018-11-13T16:01:44+00:00November 11th, 2018|Categories: Grinding|Tags: |Comments Off on Gearless Warp Around SAG Mill

Computer Control & On-Stream XRF Analyser Flotation Process

The grade of the feed to the concentrator averages 0.9 g/t Au, 110 g/t Ag, 1.1% Cu, 2.8% Pb, 9.2% Zn, 5.0% Pyrite-S and 13% BaSO4.

Recently, a new automatic reagent control system was developed by Dowa Mining Co., Ltd. This system consists of On-Stream X-ray Fluorescence Analyser (OSA), Central Processing Unit (CPU), Cathod Ray Tube (CRT) and Control Units. This system calculates the material balance and flotation rate constants in the circuit based on the OSA assay data, and then predicts the assay of flotation products. According to the prediction, reagent additions at five points are automatically controlled.

The flotation is characterized by the adoption of SO2-lime method and hot pulp flotation, both of which are developed in Kosaka concentrator of Dowa mining Co., Ltd. After the conditioning with H2SO3 solution and lime, Cu.Pb bulk flotation is carried out according to the flowsheet. Cu.Pb bulk concentrate is then treated by means of hot pulp method to separate it into copper and lead concentrates. The tailing from the Cu.Pb bulk flotation goes to the zinc flotation, where zinc concentrate is recovered by conventional method. This new system has the following features.

  1. With this system, nine different sample flows can be treated at
By |2018-11-12T16:38:31+00:00November 11th, 2018|Categories: Flotation|Tags: |Comments Off on Computer Control & On-Stream XRF Analyser Flotation Process

Flotation Kinetics Data Analysis

Several reasons contribute to the wide gap in the industrial application of the academic models. These include: 1) the lack of generality in the model, e.g., the model is limited to certain size ranges; 2) the academic models involve complicated mathematics 3) confusion about the order of the flotation rate, e.g., several authors proposed a first order rate model, whereas the others propagated a second order rate model 4) the use of an unrealistic rigid value, such as the use of a maximum recovery of 100%, which is unrealistic in industrial operations; and 5) the use of graphs that confuse the reader rather than interpret information.

The standard procedure in the laboratory rougher flotation testing was as follows: 1500 g of sample was ground in the presence of lime at 60% solids to a specific grinding requirement. The pulp was then transferred to a 5.8-liter Denver cell. Flotation chemicals were added and the pulp level adjusted to the 4.4-liter level. After conditioning for 30 sec, flotation was started. The froth was collected at intervals which were more frequent in the beginning and less frequent to the end.

The flotation rate of copper is proportional to the residual recoverable fraction of copper and

By |2018-11-12T16:38:25+00:00November 11th, 2018|Categories: Flotation|Tags: |Comments Off on Flotation Kinetics Data Analysis

Non Toxic Pyrite Depression Reagents

The depressing effects of different inorganic chemicals on the flotation of pyrite have been investigated in this study. The results of the flotation tests indicate that pyrite can be depressed by oxidizing as well as reducing agents under controlled conditions of pH and reagent dosage. Oxidizing reagents such as potassium chromate and potassium dichromate were found to cause complete depression of pyrite in the acidic pH range. These effects are similar to those obtained in the pyrite-cyanide system. A less stable oxidant, potassium permanganate, inhibited the flotation of pyrite at a concentration as low as 0.1 mol/L at all pH values. Addition of reducing chemicals such as ferrous chloride or manganous sulphate to the flotation of pyrite were found to produce depressing effects depending on the additive concentration and pH of the solution.

Experimental

Massive pyrite was crushed and dry ground in a porcelain ball mill. The 100/400 mesh fraction was separated by wet screening with tap water, and panned to remove the small amount of silicates present as inclusions, and deslimed. The cleaned sample was given a final wash with 0.1 M HCl solution to remove the adsorbed impurities, and thoroughly rinsed with distilled deionized water.

Collector (KEX): Commercial Potassium

By |2018-11-12T16:35:42+00:00November 10th, 2018|Categories: Flotation|Tags: |Comments Off on Non Toxic Pyrite Depression Reagents

Mill Design Example

Pinson Mining Company was formed to develop a gold orebody located in northern Nevada near Winnemucca. A feasibility study was undertaken in 1979 by a consortium of three Toronto-based mining companies arid a Reno-based exploration company.

The Pinson plant has been described in some detail by Mcquiston and Shoemaker in the AIME’s Gold and Silver Cyanidation Plant Practices. I will review the flowsheet only briefly, highlighting significant features. The emphasis of this presentation will be on specifics of the design.

The crushing plant flowsheet is illustrated. It is a conventional two-stage plant, producing a minus 5/8 inch product. The most significant feature of the design, from a mill superintendent’s view¬point, was the provision of a belt plow and outdoor crushed-ore stockpile. This stockpile of about 20,000 tons is used to maintain steady mill feed during crushing plant maintenance shutdowns.

The grinding circuit is illustrated schematically also. The Pinson ore is extremely clean from a leaching standpoint. There are no sulfides or carbonaceous materials to consume reagents or rob dissolved gold. This fact allows the leaching reagents to be fed dry onto the mill feed belt with the crushed ore, eliminating the capital and operating cost of a reagent mix system.

Cyanide leaching is rapid

By |2018-11-12T16:33:41+00:00November 10th, 2018|Categories: Leaching|Tags: |Comments Off on Mill Design Example

Large Flotation Cells Mechanism

The development of larger size flotation machines, which started in the 1950’s and 1960’s, is still proceeding. The largest mechanical flotation machines available today have unit volumes in the range of 38 to 42 m³ (1,350 to 1,500 cft). In fact, the motivating forces of increasing capital and energy costs and decreasing ore grades, which created the need for large flotation cells, not only still exist, but are becoming more critical.

The development of the Dorr-Oliver Flotation machine was initiated as a result of an industry need for more efficient mechanical flotation performance. The cost pressures facing the minerals industry today are severe and result from a variety of factors including:

a) Low product demand and depressed prices
b) Older process equipment with low energy efficiency
c) Poor productivity
d) High labor costs
e) Falling ore grades

Design Considerations

The purpose of the rotor in a mechanical flotation cell is two-fold. First, it must perform the task of a pump in maintaining the suspension of solids throughout the lower portions of the tank. Second, it must produce the required quantity of fine air bubbles and effectively disperse them into the slurry.

The guidelines called for a small diameter energy efficient rotor that would operate as an efficient

By |2018-11-12T16:32:42+00:00November 10th, 2018|Categories: Flotation|Tags: |Comments Off on Large Flotation Cells Mechanism

Liquid Membrane Processes in Copper Extraction

In a conventional liquid ion exchange process, there exists three distinct phases: an aqueous phase as the source of metal ion; an-organic phase consisting of an ion exchanger dispersed in an organic solvent; and an aqueous phase as the sink for recovering metal ion from the organic phase. The process of recovering metal ion is accomplished in two consecutive steps. In the first extraction step, the metal ion in the source aqueous phase reacts with the ion exchanger in the organic phase to form a metal complex. The metal complex is soluble in the solvent but not in the aqueous phase. The organic phase, which now contains the metal complex, is referred to as the loaded organic. In the subsequent stripping step, the metal ion is stripped from the metal complex in the loaded organic and recovered as an ion in the sink aqueous phase.

Experimental

The membrane oil used was a mixture of surfactant and solvent. The surfactant used was a polyamine with an average molecular weight of 1500. The solvents used were S100N, Isopar M, and LOPS, either singly or a mixture of S100N with either Isopar M or LOPS. All these solvents are basically isoparaffin hydrocarbons

By |2018-11-10T09:48:11+00:00November 9th, 2018|Categories: Hydrometallurgy|Tags: |Comments Off on Liquid Membrane Processes in Copper Extraction

Kivcet Process

It has long been recognized that the conventional method of producing lead bullion from concentrates via the sinter-blast furnace route presents problems in meeting the tight regulations for environmental protection which have been introduced in many countries. As described by Chaudhuri and Melcher, 1978, this has led to the development over the past decade of various processes aimed at the production of lead directly from concentrate in a single furnace.

Features of Kivcet metallurgy

Of the new lead smelting processes Kivcet is the only process which offers the potential operator the choice of simultaneously recovering the zinc, which inevitably occurs in the lead concentrate, as a saleable product. Zinc sulphide as well as other metallic sulphides in the concentrate are oxidized with technical grade oxygen in the smelting shaft of the Kivcet furnace.

Alternatively, the amount of reducing agent fed to the furnace can be controlled so that minimum fuming of zinc takes place and a slag suitable for dezincing in a conventional slag fuming furnace or Waelz Kiln is tapped. Recent pilot plant test work has shown that it is possible to selectively reduce lead oxide from the oxidised melt produced in the smelting shaft by the charging of specially

By |2018-11-10T09:46:48+00:00November 9th, 2018|Categories: Pyrometallurgy|Tags: |Comments Off on Kivcet Process

Galvanic Bio-Leaching – Pyrite Chalcopyrite & Sphalerite Interaction

The role of microorganisms in the leaching of metal sulfides is well established. However, this established knowledge applies mostly to chemolithotropic microorganisms such as Thiobacillus ferrooxidans which function optimally in leaching catalysis between 25-35° C, and in a pH range of 2-2.5. Although leaching with thermophilic microorganisms capable of extending the range of catalytic viability beyond 35° C is also documented, there are few if any attempts to optimize or extend sulfide concentrate leaching with thermophilic microorganisms.

sulfide-leaching-equation

where M in reaction (1) designates the metal (or metals in the specific case of chalcopyrite) to be released to solution by galvanic conversion.

Efforts were made to optimize the ratio of chalcopyrite to pyrite by adding various amounts of pyrite to a constant amount of chalcopyrite. Further experiments were carried out to study the particle size effect of both pyrite and chalcopyrite.

Large mineral samples of chalcopyrite, pyrite and sphalerite were cut into cubic shapes with a nominal size of 2 cm using a diamond saw. They were then polished on 50, 80, 120, 240, 320, 400, 600 grit size papers and finally, fine polishing was done using 1 µm alumina powder. To ensure maximum electrical contact

By |2018-11-10T09:46:15+00:00November 9th, 2018|Categories: Hydrometallurgy|Tags: |Comments Off on Galvanic Bio-Leaching – Pyrite Chalcopyrite & Sphalerite Interaction

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