basic grinding in ore dressing operations

basic grinding in ore dressing operations

Ore Dressing Methods

The fact that a product of high value and small bulk can be produced at a gold mine, often by relatively simple milling processes, has made it possible to operate gold mines successfully in remote and inhospitable regions where high costs of transportation, fuel, and power would make it impossible to exploit profitably base metal ores of equal dollar value. As a result, in many instances gold mine development has been the advance guard of civilization in regions where other mineral resources were developed later and agriculture and industry followed.

See full list on

In the milling of gold ores, as with other kinds of ores, the treatment that will give the best metallurgical and economic results in any particular instance is determined primarily by the character of the ore, although other factors previously mentioned must be considered also. The principal ore characteristics that govern the selection of the milling method are grade of ore and uniformity of tenor, the size of the gold particles, the nature of the associated minerals, and the degree to which the gold particles are locked within them. The details of the process also will be determined by these characteristics and to a considerable extent by the crushing and grinding qualities of the ore. Ores of very low grade usually can be exploited successfully only when treated on a large scale in plants of high capacity, which involve heavy initial capital outlay. Higher grade ores may be treated profitably in smaller plants with lower initial outlay per dollar of output, unless the ore is ref...

See full list on

There are two principal methods of amalgamationplate amalgamation and barrel amalgamation. In plate amalgamation the ore is crushed wet in stamp mills or ground in ball mills and the resulting pulp flows over copper plates , which are coated with amalgam and mercury. Particles of free gold and silver coming in contact with the mercury alloy with it to form gold silver amalgam, which adheres to the plates. Where stamps are employed, the screen openings range from about 12 to 40 mesh as a rule, which determines the maximum size of ore particles in the pulp passing over the plates. Mercury sometimes is introduced into the stamp mortar, also, especially if there is much coarse free gold in the ore. The plates are dressed every few hours, the interval depending on the grade of the ore, amount of sickening that takes place, the scouring action of the pulp, and degree of discoloration of the plates by chemical action. Dressing usually comprises brushing the plates from the...

See full list on

Concentration is employed for the purpose of segregating the gold in a product of relatively small bulk for direct shipment to a smelter or for further treatment in the mill. For many years gravity concentration was virtually the only concentrating method employed in gold mills, but in recent years flotation methods have been used widely, especially in the flow sheets of new mills. As an adjunct to other methods, concentration may effect marked savings in operating costs. Thus, it is often possible to produce a concentrate containing most of the gold after relatively coarse grinding, then fine grind the concentrate preparatory to extracting the gold by cyanidation or amalgamation. Since fine grinding usually is the most costly operation in gold milling, it is obvious that where it can be restricted to a concentrate, the bulk of which is only a fraction of that of the original ore, the saving in cost is appreciable. Furthermore, the constituents of t...

See full list on

The cyanide process is based on the work of MacArthur and the Forrests and involves the leaching of gold and silver from alkaline pulps with dilute solutions of sodium or potassium cyanide, the filtering and clarification of the gold silver bearing solution, and precipitation of metals from solution. Oxygen is essential to the solution reaction, and in practice oxygenation is accomplished by violent agitation of the pulp by the injection of compressed air. Precipitation usually is by means of zinc shavings or zinc dust and is improved if the solution be first de aerated. Aluminum is used instead of zinc under some unusual conditions. Nearly all gold ores are amenable to cyanidation, although, as previously pointed out, certain constituents of some ores cause excessive consumption of cyanide and other reagents, or the fouling of solutions, with resultant high costs. A few are so difficult to treat by direct cyanidation that costly preliminary treatment must be employe...

See full list on

The data in table 57 have been obtained from various sources as noted. In view of the frequent changes in practice that take place in most mills due to changes in ore characteristics, in methods and equipment brought about by research and improved machines, and increases or decreases in capacity, these data should be understood to apply specifically to the period covered and only generally to long time operations. However, they represent broadly current practices and results obtained in milling various types of gold ores.

See full list on

Live Chat

Products

Copyright © 2021.Company name All rights reserved.

Call Us +86
15903396981
whatsapp
whatsapp