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China produces hundreds of thousands of tons of gold-containing sulfuric acid slag per year. At present, only more than 3 grams/ton of slag is used. Only 75,000 tons of processing capacity per year, and the remaining slag or waste is discarded or more than ten yuan/ton. The price is sold to the cement factory as raw materials, and the gold contained in it is lost. It is a pity.
From the technical literature at home and abroad, the technology for recovering gold from slag is limited to the cyanidation process. Re-election, flotation, magnetic separation, and thiourea processes are all in the research stage.
The current cyanidation process is only suitable for the treatment of sulfuric acid slag with a gold grade above 2.5 g/? ton. If the grade is low, the profit is too low, and the investment is difficult to recover in a short period of time. Therefore, although it has good social benefits, the economic benefits are not Obviously, there is no incentive to build a gold plant; although the heap leaching method can reduce the production cost, but it cannot be continuously produced and cannot be produced in winter, this process is also difficult to promote; re-election, magnetic separation and flotation are all capable of Recovering a part of the gold in the slag, but the recovery rate is not as high as the cyanidation method, and the recovery rate is not ideal when recovering gold from the produced concentrate. It is also difficult to promote. The thiourea method has high cost and the leaching conditions are difficult to control. The method of recycling of Zhongjin is still satisfactory, still in the exploration stage, far from industrial application.
We believe that there are two main factors affecting the withdrawal of gold from slag. First, the investment is too large, and second, the production cost is too high. If these two problems can be solved, the low-grade sulfuric acid slag gold extraction technology will be Smooth promotion.
Through the research on the cyanidation process promoted and used in China, it is found that the process has the following problems:
1. Many years of research by Changchun Gold Research Institute has proved that sulfuric acid slag can be ensured without the need to re-cyanide leaching rate. The purpose of using the grinding section is only to ensure that the slurry is stirred evenly during the cyanidation reaction. The investment of the miners is more than 400,000 yuan, and the production cost is as high as 15 yuan / ton. If the section can be cut by other means, the investment and production cost of the cyanide method will be greatly reduced.
2. Because of the overflow of the thickener after discharge grinding, the impurities such as iron and copper dissolved in the slag are removed, and cyanide cannot be added during the grinding process, so the lean liquid cannot be recycled. After the treatment of lean liquid, the production cost will not only increase the production cost, but also cause environmental pollution problems. In some areas with high environmental quality requirements, the environmental protection department will not approve the establishment of a cyanide plant.
3. Many sulfuric acid plant was built within the city? Without enough space to build a large tailings. When using the cyanide process now, whether or replaced with zinc powder by CIP,? Must be separated by filtration cyanide tail The waste slag is discharged, and the slag is transported to the vehicle by the motor vehicle. The filtration section increases the investment, and the grinding granules become finer, which increases the difficulty of filtration and increases the production cost.
4. The replacement of zinc powder will increase the concentration of zinc in the lean liquid, worsen the leaching conditions, and reduce the gold recovery rate. Because of the high hardness of the slag, the charcoal wear is large, the gold loss is more, and the production cost is increased.
5. The biggest shortcoming of the cyanidation method is not that the reaction time is too long, generally it takes at least 16 hours, which requires the construction of a large volume of leaching tank, increased investment, increased power consumption, and increased plant area.
In summary, the extraction of gold from low-grade sulfuric acid slag must develop new leaching techniques or new processes to reduce investment and costs. The specific research content includes the following ways:
1. Using the new leaching equipment , the leaching reaction can be carried out smoothly without grinding. The leaching power consumption does not increase or increase less.
2. Using the leaching method with fast leaching speed, the leaching time is only a few hours or less. The stirring strength can be increased to ensure the leaching effect. Because the reaction time is short, the unit power consumption will not increase much.
3. Adopting the whole process of lean liquid circulation, not discharging waste water, saving waste water treatment cost and saving leaching agent.
4. The gold is recovered from the noble liquid by the fixed bed adsorption method. There is no washing section or carbon slurry section. The direct filtration after immersion increases the gold concentration of the noble liquid to increase the gold grade of the adsorbent, and reduces equipment investment and production cost.
Through a large number of researches and experiments, the water and chlorine process has been selected. The results of the small test show that the leaching rate is higher than that of the cyanidation method. The reason is that the film on the gold surface of the slag particles in the cyanidation process hinders gold leaching and diffusion. Both are determined by the nature of the slag - the calcination temperature of cyanide tailings is important.
2. Technical and economic indicators of new processes and new equipment 1. Technical process indicators Gold recovery rate: 55%
Leaching time: 3min ? Lime consumption: 3kg/t
Power consumption: 15kwh / t
Water consumption: 0.15m 3 ?/t Liquid chlorine consumption: 3kg/t
Investment: 800,000 yuan Production cost: 38.6 yuan?/t Production staff: 35 people 2. Gold production and output value, profit According to the annual production of 300 days, the processing capacity is 100m 3 ?/d, and the slag gold grade is 1.5g/t. The recovery rate is 55%, and the amount of gold produced is as follows:
Gold production per ton of burning: 1 × 1.5 × 55% = 0.825g
Nissan Gold: 100×0.825=82.5g
Annual production of gold: 300 × 82.5 = 24750g
Output value per ton of slag: 0.825×96=79.2 yuan Daily output value: 100×79.2=0.792 million Annual output value: 300×0.792=237.6 million Annual profit: 300×100×(79.2-38.6)=1.2 million yuan according to 100 10,000 yuan investment calculation, the return period is 10 months.
The minimum economic grade for gold extraction with this process is 0.75g/t.
3. Comparison of new process and conventional cyanide process New process:
┌──除æ‚——â”
↓ │
Slag → leaching → separation ─ → adsorption → smelting → finished gold ↓
Waste residue Original cyanidation process:
┌────┬───────â”
↓ ↓ │
Slag → Ball Milling → Grading → Thickening → Leaching → Filtration or Washing – ┠│
↓ │ │
Waste residue │ │
│ │
Finished product gold ↠smelting ↠adsorption or replacement â†-┘ │
│ │
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New technology and equipment for gold extraction from sulfuric acid slag (1)
A. Sulfuric acid residues gold extraction technology status and research currently appears obvious use of gold resources in China can not keep up exploration and production requirements of the situation, which restricts the increase of China's gold production, at the same time, from gold-bearing waste rock and hard beneficiation The technology and support policies for gold recovery are not ideal. This part of the gold resources has not been fully utilized. The gold recovery technology containing gold sulfuric acid slag is urgently needed for development.