Mineral Processing Engineering

Heap Leaching Economics

Expanded markets for copper in the past few years and a consequent search for new ore bodies have revitalized the widely known but seldom applied method of producing copper called heap leaching. This term should be differentiated from dump leaching in that the latter is applied to dumps of mixed oxide and sulfide ores (although either may predominate) that have been too low grade to beneficiate and have, therefore, been stripped off the higher grade underlying sulfide ores. Heap leaching is defined here as the process applied to oxide ores which have been mined solely for the purpose of leaching.

Although heap leaching does reduce capital expenditures, it also requires extensive test work and sound engineering to produce a successful operation. A company contemplating heap leaching must insist on a definite, well planned program of investigation. Adequate exploration is a necessity to assure that high acid consuming sections are not present in the ore body and test work must be done on drill cores to determine if acid attack on the host rock will result in physical degradation which would blind a leach heap. Items such as acid consumption, seepage and evaporation losses, leaching rates and anticipated ultimate recovery must be

Fly Ash as a Portland Cement Raw Material

In 1966, approximately 125 million tons of raw materials, exclusive of fuel, air, water, and power were consumed to produce almost 74 million tons of portland cement in the United States that is about 3,400 pounds of raw material per ton of finished cement produced. To present the figure in another way, a single plant producing 600,000 tons of cement a year would consume about 1,000,000 tons of raw materials.

At a portland cement manufacturing plant, fly ash may be used in the process, principally, at three points. It can be mixed with the finished cement, interground with the cement clinker, or serve as a component in the cement raw batch. In the first two instances it serves as a quick and inexpensive way to increase the capacity of the cement plant if kiln or grinding departments are limiting factors to production, or else to create products with special properties such as portland-pozzolan cement or certain oil-well cements. If it is interground with the cement clinker it also serves the purpose of a grinding aid. As a rule when fly ash is added in these instances, and let me stress that this presently is not a common American practice, it will

Kyanite Flotation

The ores used in the investigation were obtained from the Aluminum Silicates, Inc., Washington, Ga., and the Commercialores, Inc., Clover, S. C.

The sample from Georgia contained kyanite and quartz with clay pyrophyllite, limonite, pyrite, and rutile. Petrographic examination showed that the kyanite was essentially; liberated between -35 and 48 mesh. In the screen sizes between 48 and 100 mesh a few of the, kyanite grains had small attachments of quartz.

The mineral constituents of the sample from South Carolina were kyanite, quartz, mica, clay, pyrite, limonite, and rutile. The kyanite was essentially liberated at 65 mesh. In the screen sizes between 65 and 200 mesh, a few of the kyanite grains had small attachments of quartz.

Petrographic analyses of the two samples are, given in table 1.

flotation petrographic analysis

Experimental Results

Laboratory Batch Tests

Preliminary batch flotation tests were made of the two ores to determine the optimum conditions for separating the kyanite from the gangue minerals. The use of varying quantities and types of collectors and depressants, conditioning at different time and pulp solids, and varying the pH of the pulp were investigated. Results of preliminary tests led to adoption of

Flotation of Artificial Sulfide Minerals

The gradual depletion of high-grade sulphide mineral deposits has turned the attention of the mineral industry to the recovery of metals from the oxides and silicates. Anionic (fatty acid) and cationic collectors have in some cases made flotation of non-sulphides possible, although in general, flotation of oxide ores is not as yet an economic process.

Sulphidization of Metal Oxides and Silicates

Sulphidization with hydrogen sulphide gas was carried out in a horizontal tube furnace (Fig. I). The temperature of the furnace was regulated by means of a Variac and determined with a chromel-alumel thermocouple. The constant temperature zone in the furnace was about 6″ in length, and it was within this zone that the experiments were carried out.

Samples of reagents or minerals, placed in a 3″ alundum boat, were inserted within the constant temperature zone of the furnace. Nitrogen gas (6 ppm O2 content) was passed through the tubes at room temperature to remove air in the tube, and continued to pass whilst the furnace was heating up. When the required temperature was reached, hydrogen sulphide was allowed to enter the tube and the supply of nitrogen was shut off.

Experimental Results

When H2S, either alone or with nitrogen, is

Fine Cobbing with Alternate Polarity Magnets

At the MacIntyre Development of the Titanium Division of National Lead Company a magnetite-ilmenite ore together with gabbro-anorthosite waste is mined front an open pit by shovels and trucks. The ore from the pits is trucked to ore stockpiles for blending ahead of the crusher and to free the mine from crusher delivery schedules.

The ore is reclaimed from stockpile by an electric shovel and trucked to the crusher; all ore has been blasted or drop-ball fractured to feed the 48 x 60 inch jaw crusher. The jaw feed is controlled by a chain feeder over a stationary grizzly with 6-8 inch opening to bypass most of the fines.

Fine magnetic cobbing of minus one-half inch material was recognized as desirable very early in the operation. Maximum waste removal was not attainable, however, with i the conventional radial magnetic pulley. As mentioned earlier, the liberation of ilmenite and magnetite starts at 10 mesh so that the practical range for dry fine cobbing is minus one-half plus 10 mesh.

Many types of magnetic separator equipment have been investigated over the years. Full success in fine cobbing however was not achieved until a laboratory wet permanent magnetic drum separator for magnetite was disassembled and the

How to Evaluate Washery Performance

Many attempts have been made during the last forty years to evaluate the performance of gravity separation equipment, that is, the effectiveness with which light and heavy particles are separated. The most comprehensive treatment of the subject was made at the 1st International Conference on Coal Preparation held in Paris (1950) by Cerchar.. The float and sink analysis of the product is presented on a Gaussian distribution curve, resulting in an easier visualization of the inherent difficulties of separation. The gives of the distribution curve are then plotted, giving a quantitative measure of the deviation from perfect separation as an error distance instead of an error area.

Heavy Media Separation (HMS) Performance Criteria

In the ideal HMS process, all material lower in density than the specific gravity of separation (S.G.S.) would be recovered as floats and all material of higher density would appear as sinks.

In order to evaluate the misplaced material, the washery products are tested at the density at which the washing unit is operated. The original type of plot is shown and was developed primarily for coal cleaning units. The curve for raw coal represents the cumulative percentages of sink material. The refuse curve is also plotted as

Emulsion Flotation

Because of the extensive surface area of oil droplets in emulsions, emulsion flotation offers possibilities for the recovery of finely divided mineral particles. Surfactants must stabilize the emulsion and possess an affinity for the desired minerals. Other important factors are the nature of the emulsion ingredients, the relative volumes of the continuous and discontinuous phases, the charge sign borne by the droplets of the oil phase, the zeta potential of the desired mineral, the soluble salt content the water-pulped and ground ores. At or near the isoelectric point or ZPC, the double layer about, the mineral-laden oil droplets is reduced in thickness and the droplets will coalesce and continue to aggregate into agglomerates. Inversion from O/W to W/O can occur depending upon a number of interrelated factors. Electrokinetic Instrumentation to measure, the ZPC, electrophoretic mobility, zeta potential and streaming current are invaluable in the application of emulsion flotation to metallic and no metallic minerals.


In mineral separation, an emulsion is a mixture of two immiscible or partially miscible liquids and one or more surface active agents, one of which may or may not be a collector. When the continuous phase is water and the dispersed phase is a ‘neutral oil’ (petroleum

Electrolytic Removal of Iron from Aluminum Sulfate Solutions

A study on the sulfuric acid extraction of alumina from some Pennsylvania ferruginous clays indicated that the published electrolytic method seems to be more efficient than the known chemical methods for removing iron from the leach liquor. The main disadvantages of the chemical methods are the consumption of excessive amounts of reagents and/or the precipitation of prohibitive amounts of aluminum. In the electrolytic method iron is deposited on the mercury cathode, while aluminum is not and remains in solution. This method, however, had been handicapped by the lack of an effective and economical way to purify the contaminated mercury cathode. .

The electrolytic apparatus used in this investigation was designed and constructed to consist of an electrolytic cell and a mercury purification unit. The cell itself was a 600 mls. pyrex beaker with an outlet on the bottom and an inlet on the inside wall for recycling of mercury. The mercury cathode, having a surface area of 53.0 cm² was connected to the power source with a thin platinum wire, and agitated by air bubbling at a rate of about one bubble per second.

The mercury purification unit consisted of two verticle “M” glass tubes, with its lower ends fused separated onto

Electrokinetic Behavior of Kaolinite in Surfactant Solutions

A number of investigators have studied the electrokinetic potential (ζ) of kaolinite as a function of pH. These investigators all agree that the ζ is negative except at quite acid pH values. The actual shapes of the curves reported by the several authors vary considerably.

In spite of the general negative character of kaolinite the mineral has a rather high anion exchange capacity. The cation exchange capacity is the lowest for the clay minerals. It has been shown that anionic surfactants adsorb readily onto the mineral even up to neutrality, often in quantities exceeding the reported anion exchange capacity.


The kaolinite studied was obtained commercially and was from the American Petroleum Institute standard locality at Lewiston, Montana (project 49, sample 17). Infrared, X-ray diffraction and microscopic examinations of the material have indicated that it is a high grade kaolinite. The material is the same as was used by Choi, Smith and Wen in their study of surfactant adsorption on kaolinite.

During the past decade a large number of studies have been made of ζ of oxide minerals in aqueous solutions by the streaming potential technique. Limitations of the method, such as the measured ζ being too low because of surface conductance

Dump Leaching

The dump leaching of low-grade copper ores, as an integral part of the open-pit mining operations in the Southwest, has been practiced for the last fifty years and is increasing in importance as one of the major sources of copper. The recent acceleration in dump leaching can be attributed to the greater tonnages of low-grade ores mined and dumped at newer mines as well as resulting from increased stripping ratios at the older mines; to the relatively small investment in leaching facilities per pound of copper recovered contrasted with expansion of milling facilities to recover equal amounts of the metal by raising tonnage throughout; to low labor requirements needed for leaching; to the simple and continuous nature of the process needing little close supervision of trained operators; and, in recent years, to the awareness by the operators that dump leaching is not only an art but also a scientific process dependent on physical, chemical, and biological factors.

Materials and Methods

Samples for analysis of bacteria activity were collected from the mine dumps of the Chino Mine Division, Kennecott Copper Corporation, Santa Rita, New Mexico. All were placed in sterile 8-ounce screw-cap plastic or glass bottles and were returned to the

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