Gold extraction technology of copper-containing polymetallic sulfide gold concentrate roasting-cyanide method

Zhaoyuan gold-containing copper smelter processing high (2.09%) of sulphides gold concentrate. Direct cyanidation gold extraction consumes a large amount of cyanide and the gold recovery rate is low. Using roasting - sulfuric acid leaching - cyanidation leaching residue to extract gold silver, gold recovery improved to 97.8%, and an integrated recovery of valuable metals as silver, copper, sulfur and the like.

First, the principle of the process

The purpose of roasting of copper-containing polymetallic sulphides is to maximize the conversion of copper, zinc and other metal sulphides into water-soluble or acid-soluble sulphates, basic sulphates and oxides in order to use wet methods prior to cyanidation. The metallurgical process extracts to eliminate the harmful effects on the cyanidation leaching of gold; the roasting and porous roasting after roasting is beneficial to the cyanide leaching of gold; the sulfur in the mineral is removed in the form of sulfur dioxide and is made into sulfuric acid.

The calcination is leached with dilute sulfuric acid, and metal sulfates such as copper and zinc are dissolved in the solution, while gold, silver and lead are insoluble in dilute sulfuric acid and remain in the acid leach residue. Solid-liquid separation after leaching, for most influential impurity element into the cyanide solution, copper was replaced with the scrap iron and copper recovery reaction is as follows:

Me+H ₂ SO ₄ =MeSO ₄ +H ₂ O (Me=Cu, Zn...)

CuSO ₄ +Fe=Cu↓+FeSO ₄

Dilute sulfuric acid leaching residue containing gold and silver is extracted by gold and silver by cyanidation.

Second, the production process

The original design process is roasting of gold concentrate, salt immersion in cyanidation after roasting ore leaching, and leaching of lead by saturated sodium chloride solution after salt leaching to eliminate the influence of lead sulfate produced by roasting on cyanide leaching. After the production, due to a large change in the composition of raw materials, the lead content was reduced from 2.12% to 0.59% of the original design, and the lead was lost. Therefore, the process is mainly composed of several parts of calcination, acid leaching and cyanidation.

Dilute sulfuric acid leaching:

The slaked dilute sulfuric acid leaching is carried out in a Ñ„2500×2500mm stirred tank. The leaching slurry is pumped by a Ñ„50mm pneumatic diaphragm pump to a 25m ² continuous horizontal vacuum belt filter for washing and washing. The filtrate and washing liquid are sent to a Ñ„12m thickener. The clarified liquid is sent to a Ñ„1300×1300mm horizontal drum type displacer to recover copper, and the concentrator bottom is returned to the filter, and the acid leaching residue after filtration and washing is sent to the cyanide leaching system.

Dilute acid leaching technical conditions, liquid-solid ratio: 1.5:1, leaching time: 60h, leaching temperature 80-90 ° C, immersion liquid containing acid 4 ~ 6g / L (per ton roasting ore plus 6 ~ 8kg sulfuric acid 98%).

Cyanide

After the acid leaching residue is added to the lean liquid and the alkali liquid, it is sent to 9 sets of Ñ„3000×5000mm axial flow cyanidation leaching tank for leaching, and the leaching slurry is fed into a Ñ„15m thickener for washing, and the bottom stream is fed into a continuous level of 25m ² . The vacuum belt filter is filtered and washed, and the filtrate is returned to the concentration machine. The overflow of the concentrator is the liquid, and the gold and silver are replaced by zinc powder after purification and deoxidation. The filter cake is cyanide residue and pumped to the tailings dam.

Cyanide leaching conditions: liquid-solid ratio: 3:1, leaching time: 38h, sodium cyanide concentration 0.08% to 0.12%, pH=10-11.

Filtration and washing conditions: filtration washing area is 25 m ² , washing water feeding amount is 1000-1200 L/h, filter cake thickness is 4-6 mm, vacuum degree is 4.9-5.8 kPa, and compressed air pressure is 4-6 kg/cm ² .

Third, the main technical and economic indicators

The main technical and economic indicators are shown in the table below.

Table Main technical and economic indicators

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