High grade ore

Longer-chain amines, ie, arachidyl—behenyl (C2Q to C22) amines, are used ia special cases ia which brine temperatures exceed 35°C. At temperatures higher than ambient, normal tallow amine tends to dissolve and therefore is unavailable to coat the surfaces of the potassium chloride crystals. Amine consumption is from 50 g/1 (ca 40 wt % KCl) of high grade ore, to 150 g/1 (ca 20 wt % KCl) of low grade ore. 

It is most economical when high-grade ores are used, becoming less economical with poorer feed materials containing iron, because of the production of chloride wastes from which the chlorine cannot be recovered. By contrast the sulfate process cannot make use of rutile which does not dissolve in sulfuric acid, but is able to operate on lower grade ores. However, the capital cost of plant for the sulfate process is higher, and disposal of waste has proved environmentally more difficult, so that most new plant is designed for the chloride process. 

The depletion of domestic high-grade ore deposits has made the United States vulnerable... 

Copper ores are found worldwide, in Russia, Chile, Canada, Zambia, and Zaire and, in the United States, in Arizona, Michigan, Montana, Nevada, New Mexico, Tennessee, and Utah. High-grade ores of 99% pure metal were found in the United States (and other countries), but many of these native ore deposits have been mined over the past hundred years and are now exhausted. Even so, many low-grade ores with concentrations of 10% to 80% pure copper still exist and await a technology that will make them more profitable for exploitation. 

Silver is usually extracted from high-grade ores by three common processes that have been known for many years. These are amalgamation, leaching, and cyanidation. In one amalgamation process, ore is crushed and mixed with sodium chloride, copper sulfate, sulfuric acid, and mercury, and roasted in cast iron pots. The amalgam is separated and washed. Silver is separated from its amalgam by distillation of mercury. 

The above processes are applied for extraction of silver from high-grade ores. However, with depletion of these ores, many processes were developed subsequently to extract silver from low-grade ores, especially lead, copper, and zinc ores that contain very small quantities of silver. 

MgO, and sulfur and phosphorus content. In some operations high-grade ore is selectively mined, hand sorted and screened, and sold as lump and fines. More commonly the high-grade lump material is removed by hand, and the reminder is crushed and ground before beneficiation. LIBS may be used for chromite sorting and Mg, Al, Si contents evaluation (Fig. 8.12). 

In addition to potassium hydrogen sulphate and sodium hydrogen sulphate8 for opening up the ore, potassium carbonate,9 sodium peroxide, and alkali hydroxides 10 have been employed. The use of potassium hydroxide is preferred in the case of a high-grade ore of low titanium content 11 it has the advantage over sodium hydroxide that potassium tantalates are soluble in solutions which contain excess of the alkali, whereas sodium tantalates are insoluble. 

Roasting. The process of roasting consists of heating the finely powdered ore (either a concentrate or the crude high-grade ore) in the presence of air. This treatment may serve one of three purposes, depending on the nature of the ore ... 

Metallurgy. Owing to the instability of mercuric sulfide and mercuric oxide, the metallurgy of mercury is relatively simple. Low-grade ores that have been concentrated by flotation or high-grade ores may be treated in one of two ways. The simplest procedure involves roasting the sulfide to produce mercury vapor and sulfur dioxide ... 

An older metallurgical process, which is still used extensively, involves a rather extended treatment of high-grade ore or concentrates obtained by a flotation process. In either case, the finely divided ore is roasted to convert sulfides and carbonates to oxides, which are then reduced by means of carbon at temperatures of 1200 to 1300°C. Since zinc boils at 907°C, the liberated metal distills from the earthenware retort and may be condensed in suitable receivers. If the temperature of the condenser is kept below the melting temperature of zinc (419.3°C), the metal is obtained in the form of zinc dust which, in addition to metallic impurities, contains approximately 5% zinc oxide. If, however, the zinc vapors are condensed at a temperature above... 

The derivatives of various secondary stages of mineral formation are not included here hematites of specular type in veins of alpine type and in high-grade ores, siderite veins martites, goethites, and carbonates from the oxidation zone. 

Wadsworth, M.E., 1972. Second Tutorial Symposium on Extractive Metallurgy, Leaching of Low and High Grade Ores, Dump Deposits and Concentrates, Part III, Advances in the leaching of sulfide and oxide minerals. University of Utah. 

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