The microbial leaching uranium process is a process technology that combines bacterial leaching technology with traditional uranium mining technology, and it has the advantage of bacterial leaching. Due to the characteristics of uranium resources, the current processes used for microbial leaching of uranium mainly include four types: conventional agitation leaching, surface heap leaching, in-situ blasting leaching and in-situ drilling and leaching.
1 conventional stirring leaching
Conventional agitation leaching is mainly suitable for high grade fine ore or mud. The uranium deposits in southern China are mainly hard rock types. These uranium deposits are generally characterized by high clay mineral content and poor permeability. In order to improve the production efficiency of this type of ore and the leaching rate of uranium, a bacterial agitation leaching process can be used. Li Guangrui et al. carried out a comparative study of sulfuric acid stirring leaching and bacterial stirring leaching process using low-grade uranium ore from a mine in Guangdong. The results showed that microbial stirred leaching not only saved acid consumption but also improved leaching rate.
2 heap dipping
Among the proven reserves of uranium resources in China, low-grade hard rock uranium resources account for a considerable proportion. Bacterial heap leaching uranium technology plays a role in low-grade uranium leaching due to its low cost and simple process. The more important the role. Since the mid-1980s, the leaching and uranium extraction process of hard rock uranium has been dominant in China's uranium mining and metallurgy production, and microbial oxidation heap leaching technology is one of the main research and development directions of uranium mining and metallurgy process. . Heap leaching is divided into surface heap leaching and underground heap leaching (mainly underground blasting heap leaching).
3 in-situ blasting
In-situ blasting leaching is the use of blasting method to break the ore in the ore body to a predetermined reasonable block, so that the piles with fine crack development, uniform blockage, reasonable gradation and good permeability can be generated locally. after the ore heap leaching solution wine cloth portion, the leaching solution is collected transfusion ground metal uranium recovery process, tailings remaining after leaching stope local storage for disposal. This process is mainly for low-grade uranium deposits with limited geological and hydrological conditions. It is impossible to carry out in-situ leaching and it is uneconomical to treat the ore from the surface. This technology has been successfully applied to the recovery of resources in multiple low-grade uranium deposits and post-harvest ore bodies. Since a large amount of ore does not need to be transported out of the earth's surface, the cost of uranium production is greatly reduced, and the level of radioactive contamination of the surface of the mine is also reduced.
The in-situ blasting and leaching production system includes three parts: underground leaching, ground heap leaching and metal recycling workshop. Since the conventional water and metallurgical plant is not built, the production process is simplified, the equipment and facilities are greatly reduced, the mechanization and automation are high, and the production efficiency is greatly improved. The production and management personnel can be reduced by 60% to 70% compared with conventional mining, selection and metallurgy. Production costs can be reduced by 30%, so the United States, the Commonwealth of Independent States, Canada, South Africa, Portugal and some countries in the third world use this technology to mine low-grade copper , uranium, nickel , radium and other colored rare metal primary ore and oxidation. Ore, especially low grade ore such as copper and uranium. At present, 0.15% to 4.5% of low-grade copper ore, more than 2% of copper oxide ore and 0.02% to 0.10% of uranium ore in these countries are basically leached by in-situ leaching and in-situ blasting.
4 in-situ drilling and leaching
The in-situ drilling leaching is characterized in that the ore is in a natural state of existence, and without any displacement, the leaching solution is injected into the ore layer through a drilling project to make contact with the useful components in the heterogeneous ore for chemical reaction. The soluble compound formed by the reaction leaves the chemical reaction zone by diffusion and convection, enters the liquid stream permeating along the ore layer, and is collected into a leachate (mother liquor) containing a certain concentration of useful components, and moves in a certain direction, and then is drilled by drilling. It is pumped to the surface water metallurgical plant for processing and extraction of leached metal uranium. The in-situ drilling and leaching process is subject to harsh conditions. Generally, the following conditions are met: (1) The ore body has natural permeability, the production is gentle, continuous and stable, and has a certain scale; (2) the ore body is present in the aquifer. In the middle, and the ratio of the thickness of the ore layer to the thickness of the aquifer is not less than 1:10, the permeability of the surrounding rock of the bottom plate or the top and bottom plates is impervious or the permeability of the surrounding rock of the top and bottom plates is much lower than that of the ore body. There shall be no water-conducting faults, underground caves, dark rivers, etc. within the scope of leaching minerals; (3) the target metal minerals are easily soluble in the leaching agent and the surrounding rock minerals are insoluble in the leaching agent, for example: copper oxide ore and Raw hexavalent uranium is easily soluble in dilute sulfuric acid, while its surrounding rock mineral quartz and silicate minerals are insoluble in dilute sulfuric acid, and the two minerals are beneficial for leaching. Due to the harsh conditions, the underground in-situ drilling method is only used in the loose sandstone uranium deposits at home and abroad. This loose sandstone uranium deposit usually occurs in the interlayer aquifer of the Mesozoic and Cenozoic geological background of the gravity basin. The ore-bearing lithology is sandstone, and the ore structure is loose. The secondary hexavalent uranium is more easily leached by acid and alkali, and is suitable for in-situ leaching.
Most of the uranium mining and metallurgical enterprises that use the in-situ leaching process to recover uranium are in remote areas with inconvenient transportation. The oxidant H2O2, which is often used, is expensive and inconvenient to transport, and the oxidant cost accounts for a large proportion of the production cost. The Sixth Research Institute of the Nuclear Industry conducted a pilot study on the replacement of hydrogen peroxide (hydrogen peroxide) with bacterial liquid in a uranium mine in a certain area of ​​Yunnan and a uranium mine in a certain area of ​​Xinjiang. The test results show that the oxidation of the infusion agent is equivalent to that of hydrogen peroxide, and the high-potential liquid can completely replace the hydrogen peroxide, which can reduce the cost of the oxidant by 70%.
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