Industry requirements for uranium ore reserves, Conditions for...

Industry requirements for uranium ore reserves

Uranium ore reserves in the bowels are expressed by their mass, as well as by the mass of uranium in the ore. The scale of uranium deposits is determined by their reserves. According to V.I. Krasnikova [17], uranium deposits with reserves of the first hundreds of thousands of tons are classified as unique, to large deposits with reserves of tens of thousands of tons, and to medium reserves with thousands of tons. Deposits with uranium reserves of less than a thousand tons are classified as small and, as a rule, do not have independent significance. As N.S. Umbrellas [46], the scale of uranium deposits in hundreds of thousands of tons of uranium is obviously limiting and find a justification in the regular dependence on uranium clark in the earth's crust.

As well as for other minerals, the qualitative and quantitative characteristics of uranium ore reserves are closely interrelated. The lower the uranium content in the ore is, the greater its reserves, as well as the ore reserves in the interior. However, according to statistical data, the correlation between the scale of deposits and the average uranium content in ores, with some exceptions, is practically nonexistent. The degree of concentration of uranium in the deposits depends on the composition of the mineral carrier and on the mechanism of ore deposition. It is much more easily predictable than the scale of deposits, since the range of fluctuations in the scale of deposits is much wider than the range of fluctuations in average contents. According to the data of [9, 13, 45], the coefficients of variation in scales and average contents are respectively 160-170 and 50-60%.

Conditions for the development of uranium deposits and technological properties of ores

The high value of uranium ores and complex conditions for their development allow the use of labor-intensive training schemes and development systems that ensure minimal and loss and dilution of ore. Operation of uranium deposits is carried out by both open and underground methods, depending on their scale, conditions of occurrence, quality and technological properties of ores. Recent years in the practice of developing uranium deposits are increasingly using new progressive mining methods:

• underground mining with the use of hydrotransportation of broken ore from cleaning faces to receiving storages or concentrating mills;

• Mechanized methods of excavating ore layers with a capacity of more than 1-1.5 m with the help of mountain combines, conveyors and mechanized complexes;

• Drilling methods of excavating low-density strata (less than 0.5-0.6 m) and especially widely - underground leaching of uranium ores.

The use of pressure hydrotransport is advisable for the underground development of uranium deposits with small-specific ores with no abrasive properties. Such deposits include many uranium-bearing sandstones, clays, coals and phosphorites. Mechanized excavation methods with the help of mining combines and other mechanized complexes and drilling methods of excavation are most effective in the development of uranium-coal deposits and uranium-bearing clays.

Underground leaching of uranium ores is used in mine and borehole applications. The methods of borehole underground leaching (SPS) are very economical and allow the exploitation of deposits with poor ores in industrial use. However, for the application of this method, it is necessary that uranium is easily leached from ores under the action of reagents (soda or dilute acids), the ore deposits possess good filtration properties and are limited to the top and bottom by waterproof layers. Underground leaching of uranium from the mine workings requires a preliminary crushing of an array of strong ores by drilling and blasting.

Operation of uranium deposits requires large volumes of radiometric work and is associated with a set of special measures to combat radon and radioactive dust, which often leads to a significant increase in the cost of mining uranium ore.

An important technological property of uranium ores is their radiometric contrast, characterizing the degree of uneven distribution of uranium minerals in ore, determined by certain volumes, therefore, the most effective methods of processing uranium ores are their radiometric sorting and enrichment, followed by leaching of uranium from the enriched ore mass. Radiometric sorting of ores is performed on the whole route of the ore mass from the face to the factory. In the faces, the ore and rock are separated by means of mine radiometers, then it is sorted in transport vessels (trolleys, cars) at radiometric control stations (RKS), and poor ores are sorted or enriched in special installations (RAS) or radiometric concentrating plants. The use of methods for radiometric sorting and enrichment of uranium ores provides a tangible economic effect, the significance of which increases with the increase in the degree of radiometric contrast of ores. Hydrometallurgical processing of enriched uranium ores consists in their crushing and grinding, transferring uranium to solution, separating the liquid phase, cleaning the solution of harmful impurities and depositing uranium from the solution into the commodity concentrate.

Technological properties of uranium ores significantly depend on their mineral and chemical composition. The classification of uranium ores, reflecting the methods and efficiency of hydrometallurgical processing, depending on these parameters, is given in Table. 1.3.2.

Transfer of uranium into the solution is carried out in two main ways:

• Acidic;

• carbonate.

The most widely used is the leaching of uranium from ores by dilute sulfuric acid, with transfer to a solution of up to 90-98% of uranium. In dilute acid, all secondary minerals decompose well, and in the presence of oxidants (pyrolusite) - and uranium oxide minerals.

The disadvantage of the acid method is the easy interaction of acids with other components of the processed ore, which causes a large overexpenditure of reagents.

Table 1.3.2

Technological classification of uranium ores by chemical composition (according to PV Pribytkov [46])

Types of ores

Species

Content of the main components,

%

Hydrometallurgical processing methods

Silicate and aluminosilite rolled

& lt; 95 silicates and aluminosilicates

Leaching with dilute acids

Carbonate

With a low carbonate content

6-12 carbonates

Carbonate leaching or acid leaching with carbonate pre-flotation

With an average carbonate content

12-25 carbonates

With a high content of carbonates

& lt; 25 carbonates

Sulphide

With a low sulphide content

3-10 sulphides

Leaching with dilute acids

With an average sulphide content

10-25

With a high content of sulphides

& lt; 25

Iron oxide

-

& gt; 50 oxides of iron

Phosphate

Low phosphate content

3-10 p 2 about 5

With an average phosphate content

10-20 P 2 0 5

With a high phosphate content

& gt; 20 P 2 0 5

Caustobiolito -

Uranium-bearing coals and solid bitumens

-

Carbonate leaching or leaching with weak acids

Coal and bituminous shales

-

The soda method is used to process ores containing a large amount of carbonates. The advantage of the soda method is a lower corrosion of the equipment than in the acid method. However, its use entails large losses of metal and requires very fine grinding of ores, which complicates the subsequent filtration of the pulp.

Separation of the liquid phase is achieved by filtration of uranium-containing solutions and their purification. Usually, uranium is sorbed from pulps on cation exchangers or anion exchangers and is extracted by purifying eluates to give pure compounds.

Factors and indices of industrial value of deposits

The main factors that determine the industrial value of deposits and the efficiency of using the mineral reserves contained in them are as follows:

Mining-geological factors are the basis of economic evaluation of deposits. They are established in the process of exploration of deposits, and their characteristics constitute the main content of the inventory calculation.

Socio-economic factors determine the needs of the national economy in this type of mineral raw materials and the prospects for its use in connection with the economic development of the state. At the same time, the country's and specific economic area's reserves of this type of mineral raw materials are taken into account, as well as its role in resolving the tasks of strengthening economic independence and the defense capability of our country.

When assessing deposits, the balance of stocks of a given type of mineral resources is taken into account, the degree of its deficiency is determined, the prospects for the development of mining technology and the introduction of artificial substitutes. For deposits located in areas with a low employment of the population, the socio-economic effect of involving the labor force in production activities is taken into account.

Economic and geographical factors have a decisive influence on the economic evaluation of deposits of widely distributed types of mineral raw materials, whose reserves far exceed the needs of the national economy. With significant demand and a tight balance of scarce mineral raw materials, the impact of economic and geographical factors is significantly reduced.

Among the favorable economic-geographical factors are:

high economic development and good industrial development of the deposit area, ensuring the possibility of cooperating and combining mining enterprises with other industrial facilities;

• availability of water resources and developed transport network;

the proximity of mining enterprises and industrial complexes developing and consuming this kind of mineral raw materials.

When assessing the economic effect of the industrial use of the field, not only the impact of economic and geographical conditions is taken into account, but also the impact of field development on the economic development of the area and the ecological situation. connection with the exclusion of fertile lands, violation of the regime of groundwaters, etc.

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