Canadian experts talk about ways to recover gold from low grade refractory ore

Refractory and low-grade gold ore processing technology, the Canadian company Barrick Gold metallurgy technology consultant Gupta comprehensive evaluation of the level of processing of technological development in this area.

Gu Da said that the total cost allocation study shows that the mining cost is the main part of small underground mines; in the larger tonnage of underground mines and open pit mines, the cost of ore dressing, especially the processing cost of difficult ore smelting, is the main part; In terms of processing cost allocation, smashing steel and electricity can account for 50% of the cost; the treatment of typical difficult smelting ore can double the total cost.

Therefore, it is necessary to study the recycling process for reducing the amount of pulverization and grinding, the efficient pulverization treatment, and the low-cost refractory treatment method.

Reduce mining costs

Ways to reduce mining costs include: plant mining methods, drilling methods, in-situ filtration methods for mining sites, and advanced underground mining methods. To reduce the cost of open pit mining, you can use elevators or conveyor belts to upgrade. In addition, tailings reclamation is also a way to effectively reduce costs.

Gold filter method

Is there a breakthrough in technology and cost in the gold filtration method? Gu Da said that the current general cyanidation process is still the most effective. Alternative methods to choose from in the future are: Hunter method, which can reduce the consumption of cyanide by up to 90%. The vulcanization method, the advantage of ammonium thiosulfate is that it will not be consumed by natural carbon in the ore, but the vulcanization method is not better than cyanide. The method has a cost advantage; the halogenation method has many advantages, and produces sulfur oxides while decomposing gold. The halogenation method is generally low in toxicity and can be taken underground. Other methods, such as the Hubble method, are environmentally friendly and are therefore advocated for replacing cyanidation. In addition, future alternatives to cyanidation include biological methods and humic acid methods. Among them, the humic acid method may be used for underground filtration, and most of its research is done in China.

Reduce processing costs

For coarse ore processing, the benefit from lowering the processing cost is that the crushing cost is lower. There are two possibilities: mining metals from non-difficult smelting ore and difficult ore smelting or pre-concentration treatment.

- Coarse ore heap leaching: heap leaching of gold and copper is a common method, which can be applied during or after pulverization. Uranium ore can also be treated in the same way. Nickel and zinc are also recommended. Heap leaching involves special treatment of concentrates or high grade ores for higher and faster recovery. For example, the RubyHill mine in Nevada uses grinding to filter high-grade ore and then use a heap of leaching to polymerize the tailings.

- coarse ore pretreatment and leaching: if it is difficult to select smelting ore, simple heap leaching has no effect; bio- heap leaching and biological fine grinding can be used to vulcanize refractory metallurgical ore, and bio-dump immersion requires about 200 days of bacterial heap leaching The biological fine grinding method takes about 200 days of bacterial heap leaching and then recovers and finely grinds. In addition, chlorine can also be used for heap leaching.

- The coarse ore preconcentration treatment is also very effective. Screening of ore and automatic ore sorting can double the highest grade. After screening, high-grade products can be processed centrally, and low-grade products can be heap leached.

There are many new technologies that can be used for the treatment of low-grade and difficult-to-smelt ore.

——In the treatment of low grade ore, effective concentration can fully improve the economics of the project. Concentration is a prerequisite for many treatment methods, usually using a froth flotation flotation for grinding ore concentrate treatment.

- Possible solutions for difficult metallurgical ores include: sulfide encapsulation, oxidative or ultrafine grinding; gold in gold-containing solutions is snatched by natural carbon, masking, passivating or oxidizing; gold compounds such as antimony , 锑 , can be oxidized, ultra-fine grinding or high pressure. Copper is mixed into the gold, and the Hunter method or the like can be used.

- For bio-oxidized concentrates, trough bio-oxidation is generally uneconomical if used in whole mud. In the case of beneficiation, agitating tanks can be used. In addition, non-agitated reactors have been tested several times and can process 50 tons of ore per day in a production plant in South Africa.

- Whole mud roasting is now common and is usually used after dry grinding. It can solve the problem of vulcanization and gold robbing. Pyrite and tellurides with single-stage roasting filler, the filler for an arsenic-containing two-stage firing.

—— Pressure oxidation method is widely used. Full mud pressure oxidation is very common, usually with acid and occasionally with alkali. The cost of construction and production of alkali in the project development phase is low, and alkali should be used at this time. Quenching pressure oxidation is not commonly used.

——In the application of chemical oxidation method, coarse whole mud is oxidized before heap leaching; grinding whole mud treatment, some mines use chlorine gas to treat carbonaceous ore and refractory smelting; concentrate treatment, some mines try to use nitric acid treatment , but all failed.

——With the advancement of machinery, the application of ultra-fine grinding is becoming more and more widespread. Grinding to 5 to 15 microns releases and produces an effective cyanide filtration. This method requires more power, up to 100 kWh per ton.

- In copper-gold ore processing, it is very difficult to economically treat copper-gold ore because copper minerals consume cyanide. Because it is copper oxide, flotation is not often used. Methods that can be employed include: flotation, Hunter, ion exchange, and the like.

Troughing idler, which is the most common idlers used on belt conveyor, is mounted on the carrying side, used for conveying bulk materials. Generally it consists of 3 rollers in equal length. The two outer rollers are inclined upward and the middle one is horizontal. The inclined degree can be 30°,35°and 45°, some can be up to 60° in suspended type. There are two basic types: standard type and ahead inclined type. The latter can also be present all through the conveyor to prevent the belt from sideslip.