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All sliming gold cyanidation refers to the process of crushing and grinding all the gold ore into slurry, adding cyanide to leaching it, and then using activated carbon to directly adsorb the dissolved gold-laden carbon from the pulp to complete the gold extraction process. All sliming gold cyanidation mainly includes 8 stages, that is, raw ore crushing, ore grinding, slurry concentration, cyanidation and carbon absorption, gold-laden carbon desorption , pregnant liquid electrolysis, gold slime smelting and tailings processing.
Before all sliming gold cyanidation process, the raw gold ore needs to be processed. Firstly put the gold ore into the crusher and crush it to about 12mm. The ore with large particle size needs to be returned to the crusher after being separated by the classifier.
The crushed ore is put into ball mill and water is added for wet grinding to make it into slurry. The ratio of ore to water in this slurry is 1:3.5, and the ore with particle size less than 50um should accounts for more than 90%. Similarly, the ore with larger particle size needs to be returned to the ball mill after separation by the classifier. At the same time, quicklime is added at a dose of 4kg per ton of gold ore (when the process wastewater is reused, the amount of quicklime input can be reduced to about 40% of the original).
In order to meet the requirement of gold cyanidation process, the slurry needs to be concentrated. Put the ground gold ore slurry into the thickener for concentration until the ratio of slag to water is 1: 1.5. The water produced after concentration can be returned to the ore crushing and grinding stage.
This stage is an important process of all sliming gold cyanidation process. The concentrated slurry is then overflowed into leaching tank and NaCH is added at a dose of 400g per ton of gold ore. While stirring, the slurry passes through 10 leaching tanks in turn. In the end leaching tank, the activated carbon is reversely injected through the carbon separating screen, that is, the activated carbon flows in the screen in the opposite direction to the slurry, which allows the activated carbon to fully react with the slurry without entering the slurry. The dosage of activated carbon is 680g per ton of gold ore. The whole cyanidation and carbon absorption process is about 16 hours, the leaching rate is 87.88%, and the carbon adsorption rate is 99.2%.
The gold-laden carbon is separated at the outlet of the carbon screen, and then loaded into elution column. The gold-loaded carbon was eluted from bottom to top using a mixed elution solution containing 2% NaCH and 1% NaOH at
95 ° C. Elution column can process 200g gold-loaded carbon each time, consuming about 0.75 tons of elution solution. Each processing time is about 40 hours, and the desorption rate is 98.5%.
The desorbed gold-containing pregnant liquid is sent to a high-level storage tank, and is electrolyzed in an electrolytic tank. After being electrolyzed, gold slime can be obtained on the electrode. And the electrolytic extraction rate is 99.5%. Part of the lean liquid after electrolysis can be used for the preparation of elution liquid and recycled, and its circulation rate is about 65%.
The obtained electrolytic gold slime is smelted by pyrometallurgy to obtain a composite gold product containing more than 80% gold, and the smelting extraction rate is 99%.
The tailings after gold cyanidation process will be filtered by press filter. The dry gold tailings is discharged into the tailings dam, the waste water is recycled in the cyanidation process, and the water content of the dry tailings is about 20%-22%.
The above are the specific stages of all sliming gold cyanidation process. The highlight of all sliming gold cyanidation process mainly has the following points:
1. The filtrate of press filter, instead of fresh water, returns to the grinding and classifying operation, recovering dissolved gold in the tailings and reducing the loss of gold.
2. Since the CN- contained in the return filtrate is reused, the consumption of sodium cyanide in the gold cyanidation process is reduced.
3. It greatly reduces the amount of sewage processing and discharge, which is beneficial to environmental protection.
4. It greatly reduces the use of fresh water in production and saves resources.
5. After the tailings are pressed and filtered, the tailings are stored in the state of filter cake instead of slurry, which reduces the area of tailings storage and makes the tailings storage more flexible.
From the stages and highlights of all sliming gold cyanidation, it can be known that all sliming gold cyanidation process has the characteristics of simple process, small investment, low cost and high recovery rate, so it is welcomed by many gold mine owners. However, because cyanide is contained in the tailings, it will cause great harm to the ecological environment. Therefore, more and more gold processing plants begin to use low-toxic cyanide substitutes for gold cyanidation.