Uranium in situ leaching mining example

    1. Clay West uranium mine (clay west)

The mine was the first large-scale commercial production of in-situ leaching uranium mines in the United States, which was commissioned in April 1975. Pumping jointly run by the United States Steel Corporation (USSteel) and Niagara Corporation (Niagara). Its annual production capacity of U ₃ O ₈ is 112.5t at the beginning and then increased to 450t.

(1) Geographic location

The Kleves uranium mine, located 16km southwest of George West, Texas.

(2) Geological and hydrogeological conditions

The uranium ore body is linguistically present in the Miocene oakville sandstone . The ore-bearing layer has an average buried depth of 116-150 m and an average thickness of 10 m. Mineral sandstone with loose structure and permeability of 2000 millidarcy. The average grade of ore is 0.1%. The main uranium minerals are bituminous uranium or hydrous uranium ore. The symbiotic minerals are selenium and molybdenum .

(3) Drilling arrangement

The total number of drill holes is more than 2,000, with a total of four mining areas. Each mining area has an average of 550 drill holes, of which 250 are liquid injection holes, 150 are liquid extraction holes, and 150 are monitoring holes. Each set of drill holes is generally arranged in a 5-point style. The square side length is 16.67m, the liquid suction hole is at the center, the four corners are the liquid injection holes, and the distance between the liquid extraction hole and the liquid injection hole is 11.78m. The drill holes are also arranged in a square shape with a side length of 22.33 to 33.33 m.

(4) Drilling structure

The structures of the pumping, injecting and monitoring holes are basically the same. The borehole is slightly deeper than the bottom of the ore body. A PVC plastic sleeve with an inner diameter of 100 mm was installed in the injection and monitoring holes. Inside the liquid suction hole is a PVC plastic sleeve with an inner diameter of 150 mm; a filter tube for the mineral layer. Cementing between the wall of the hole and the wall of the casing, in order to prevent the cement slurry from entering the filter pipe and the ore layer during cementing, a joint with a gypsum plug is placed on the filter pipe; the cement slurry enters the casing through the discharge hole above the gypsum plug The outer gap, the gasket under the discharge hole prevents the cement slurry from leaking. In order to protect the filter tube, there are 3 to 4 centralizers on the sleeve to position the sleeve and the filter tube in the hole.

(5) Preparation of leach solution

The leaching solution is prepared, and ammonium carbonate, ammonium hydrogencarbonate and hydrogen peroxide are initially used, followed by sodium carbonate, sodium hydrogencarbonate and oxygen. The content of oxygen in the immersion liquid is 300 to 400 mg/L. The pH of the leach solution is about 9.

(6) Pumping equipment and extract

Inject the leaching solution with a corrosion-resistant horizontal pump at an injection pressure of about 1.5 MPa; extract the solution from the suction hole, use a 2.24 to 5.6 kW stainless steel submersible pump, and connect the pump to a stainless steel tube or a fiberglass tube with a diameter of 50 ~60mm. Due to the high permeability of the ore layer and the large amount of drilling fluid, the content of U ₃ O ₈ in the extract is only 20-30 mg/L.

(7) Water treatment and processing of product solutions

The uranium in the product solution is adsorbed by the ion exchange resin, and the uranium is eluted from the resin by using NaCl (plus Na ₂ CO ₂ ) as the eluent, and NH ₃ is used to wash the high concentration uranium solution from the leaching solution. Precipitated uranium (ammonium diuranate), the final product is a powdered yellow cake. The waste liquid is injected into the deep formation through the borehole.

    2. Chenjiashan Uranium Deposit

The Chenjiashan Mine is the first in-situ leaching mining site in China.

(1) Geological and hydrogeological conditions

The main industrial uranium deposits are pebbly sandstone and glutenite layers with a basement of granite . The composition of ore is mainly composed of quartz and feldspar , followed by biotite , hydromica and chlorite, as well as pyrite, mud, carbon and organic matter. Uranium is present in the form of bituminous uranium and uranium black and in the state of adsorption in carbon, organic matter and shale.

The ore permeability coefficient is greater than 0.72m/d, and the ore body depth is from tens of meters to one or two hundred meters.

(2) Drilling arrangement

The drill holes are arranged in a triangle and a rectangle, and the distance between the liquid suction hole and the liquid injection hole is about 15 m.

(3) Drilling structure

The structure of the liquid suction hole and the liquid injection hole are basically the same, the hole depth is several tens of meters, the hole diameter is 130 mm, and the hole diameter in the ore body portion is 300 to 400 mm.

(4) Preparation of leach solution

The leaching solution is prepared from ground water, sulfuric acid and hydrogen peroxide.

(5) Pumping equipment and extract

Stainless steel horizontal pump for liquid injection, air lift pump for liquid extraction and stainless steel submersible pump. The uranium content in the extract is 50-150 mg/L.

(6) Water treatment and processing of product solutions

The uranium in the product solution was adsorbed by an ion exchange resin, and NaCl (addition of H ₂ SO ₄ ) was used as an eluent, and NaOH was used as a precipitation liquid. The final product is a syrupy yellow cake.