A method for in-situ collaborative development of coal-rock-sandstone type uranium deposits

Abstract

The present invention discloses a method for in-situ collaborative development of coal-rock-sandstone type uranium deposits. Uranium resources in coal-rock and sandstone type uranium deposits are mined by combining underground coal gasification with in-situ neutral (CO2+O2) in-situ leaching. This method can achieve clean utilization of coal resources through gasification and collaborative development of sandstone and coal-rock type uranium resources. The method has the advantages of low energy consumption, high resource recovery rate, simple process, and low environmental impact. It conforms to the concept of green mining and is of great significance for addressing my country's demand for strategic key metallic uranium resources and protecting the environment.

Description

Technical Field

[0001] The present invention relates to the field of coal rock-sandstone type uranium mine development, and in particular to a method for in-situ collaborative development of coal rock-sandstone type uranium mines. Background Art

[0002] Strategically important uranium metal is a vital raw material for the nuclear industry, with irreplaceable applications in key areas such as national defense and military industry. Industrially significant uranium deposits in my country primarily include volcanic, granite, coal, and sandstone types. Hard rock uranium deposits (volcanic and granite) require the ore to be mined to the surface for further processing, which causes significant surface damage and poses significant environmental risks. Most hard rock uranium mines have been closed, with mining shifting to sandstone and coal types. Coal-based uranium deposits are formed when uranium is adsorbed and fixed by coal through adsorption and strong reduction, forming uranium-rich coal seams. Sandstone uranium deposits are uranium deposits found in sandstone (including gravelly sandstone, siltstone, and mudstone). However, existing mining methods rely on single-use uranium mining, which is associated with low uranium recovery rates, high costs, and significant environmental impacts. Coal-based uranium deposits are primarily mined underground and then burned and leached with sulfuric acid to obtain uranium. However, this process has a low uranium recovery rate, and uranium volatilization during combustion poses significant risks to the environment and human health. Sandstone-type uranium deposits have low consolidation levels in their ore-bearing sand bodies and are rich in groundwater, making underground mining impossible and limiting their development. The Ili Basin in Xinjiang boasts abundant coal- and sandstone-type uranium deposits, with the presence of contacting strata between sandstone and coal-type uranium deposits, offering the potential for synergistic mining of uranium from coal and sandstone. Summary of the Invention

[0003] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a method for in-situ collaborative development of coal-rock and sandstone type uranium deposits, which mines uranium resources in coal-rock and sandstone type uranium deposits by combining underground coal gasification and in-situ neutral (CO2+O2) leaching, thereby realizing the clean gasification utilization of coal resources and the collaborative development of sandstone and coal-rock type uranium ore resources.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for in-situ collaborative development of coal-rock-sandstone type uranium deposits, comprising the following methods:

[0006] Step 1: Digest the sampled sandstone and coal and test the content of strategic critical metal uranium using inductively coupled plasma mass spectrometry;

[0007] Step 2: Select coal-rock and sandstone-type uranium deposits with a thickness greater than a, impermeable roof and floor, and uranium content in coal ash and sandstone higher than the set value as research objects, and conduct subsequent underground coal gasification and in-situ neutral leaching of sandstone-coal-rock uranium deposits to jointly mine uranium resources;

[0008] Step 3: Detect the mineral composition of coal and sandstone and uranium-containing carrier minerals to obtain their composition;

[0009] Step 4: Use step-by-step chemical extraction experiments to determine the occurrence state of uranium in sandstone and simulated gasification coal ash;

[0010] Step 5: Field drilling is carried out in the study area, including several groups of gas holes, coal seam gasification channels and sandstone blasting channels are opened in the lower part of the coal seam and sandstone layer, and then the coal is gasified;

[0011] Step 6: After coal gasification, the sandstone-type uranium ore above the coal seam is initially crushed; the sandstone layer is crushed through the sandstone blasting channel, so that the sandstone blocks are further broken up, which is conducive to the subsequent uranium leaching;

[0012] Step 7: Use the pores to introduce CO2 and O2, O2 oxidizes the tetravalent uranium to hexavalent uranium; because the sandstone layer is rich in groundwater, the introduced CO2 dissolves in the groundwater to form HCO3 - , which then reacts with the oxidized hexavalent uranium to leach out the strategic critical metal uranium;

[0013] Step 8: Use the low-level air holes to send the extraction device to the underground leaching location, extract the uranium-rich leachate through the air holes to the ground leachate storage device, and transport it to the leachate treatment plant to recover and purify the strategic critical metal uranium.

[0014] Preferably, in step 1, the sandstone and coal sampled from the borehole are digested according to the national standard GB / T 14506.30-2010 "Chemical analysis methods of silicate rocks - Part 30: Determination of 44 elements".

[0015] Preferably, in step 2, the thickness a of the coal seam and sandstone layer is 2 m, and the coal rock type and sandstone type uranium deposits with uranium contents in the coal ash and sandstone higher than 1000 μg / g and 0.01% respectively are studied.

[0016] Preferably, in step three, the mineral composition of the coal and sandstone is detected using an X-ray diffractometer and a scanning electron microscope energy dispersive spectrometer.

[0017] Preferably, the specific method in step 4 includes:

[0018] 4.1. Weigh 2 g of 200-mesh gasified fly ash or sandstone sample into a 100-mL centrifuge tube, add 60 mL of 1 mol / L magnesium chloride solution, and place in an oscillating oven at 200 rpm and 25°C for 1 h. Centrifuge the supernatant in the centrifuge tube at 4000 rpm for 5-10 min, separating the supernatant to be exchangeable. Dry the residue at the bottom, i.e., Residue I, at 90°C to constant weight.

[0019] 4.2. Add 60 mL of 1 mol / L sodium acetate solution to Residue I, adjust the pH to 5 with acetic acid, and place in an oscillating oven at 200 rpm and 25°C for 8 h. After centrifugation, the supernatant is the carbonate state, and the bottom residue, Residue II, is dried at 90°C to constant weight.

[0020] 4.3. Add 60 mL of a 0.04 mol / L hydroxylamine hydrochloride solution prepared in 25% acetic acid to Residue II. Place in an oscillating oven at 200 rpm and 95°C for 4 h. After centrifugation, the supernatant is iron-manganese oxide. Dry the residue at the bottom, Residue III, at 90°C to constant weight.

[0021] 4.4. Add 10 mL of 0.02 mol / L nitric acid and 30 mL of 30% hydrogen peroxide solution to the residue III, adjust the pH to 2 with nitric acid, and place in an oscillating oven at 200 rpm and 85°C for 5 h;

[0022] After cooling, add 20 mL of 1 mol / L ammonium acetate solution prepared with 20% nitric acid solution, place in an oscillating box at 200 r / min and 25°C to react for 0.5 h, centrifuge, and the supernatant is the organic phase. The bottom residue, i.e., residue IV, is dried at 90°C to constant weight.

[0023] 4.5. Since the gasified coal ash has an amorphous glass phase after high-temperature combustion, in order to more accurately determine the occurrence state of uranium in the gasified coal ash, the gasified coal ash sample needs to be further dissolved after step 4.4 to separate into the glass phase and the residue phase;

[0024] By adding 40 mL of concentrated hydrofluoric acid, placing it in an oscillating box at 200 r / min and 85°C for 2 hours, the supernatant after centrifugation is a glassy phase containing aluminosilicates. The bottom residue, residue IV, is dried at 90°C to constant weight. This step is not required for sandstone.

[0025] 4.6. Digest the residue IV in accordance with the national standard GB / T 14506.30-2010 "Chemical Analysis Methods of Silicate Rocks - Part 30: Determination of 44 Elements", and the resulting digestion solution is in the residual state;

[0026] 4.7. The content of strategic key metal uranium in exchangeable, carbonate, iron-manganese oxide, organic and residual states shall be tested by inductively coupled plasma mass spectrometry.

[0027] Preferably, the specific reaction mechanism in step 7 is as follows:

[0028] CO2+H2O=H2CO3

[0029]

[0030] 2UO2+O2=2UO3

[0031] UO3+2HCO3 - =[UO2(CO3)2] 2- +H2O

[0032] [UO2(CO3)2] 2- +HCO3 - =[UO2(CO3)3] 4- +H + .

[0033] The beneficial effects of the present invention are as follows: the present method mines uranium resources in coal rock and sandstone type uranium mines by combining underground coal gasification and in-situ neutral (CO2+O2) leaching, which can realize the clean gasification utilization of coal resources and the coordinated development of sandstone and coal rock type uranium resources. It has the advantages of low energy consumption, high resource recovery rate, simple process, low environmental impact, etc., conforms to the concept of green mines, and is of great significance to solving the demand for strategic key metal uranium resources in my country and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A schematic flow chart of a method for in-situ collaborative development of coal-rock-sandstone type uranium deposits provided by an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of underground gasification and in-situ neutral leaching structure of coal rock and sandstone type uranium deposits.

[0037] Figure numerals: 1-gas hole, 2-gasification ignition device, 3-gas recovery and separation device, 4-coalbed gasification channel, 5-sandstone blasting channel, 6-extraction device, 7-leachate storage device. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] like Figures 1 to 2 As shown, a method for in-situ collaborative development of coal-rock-sandstone type uranium deposits comprises the following steps:

[0040] Step 1: According to the national standard GB / T 14506.30-2010 "Chemical Analysis Methods of Silicate Rocks - Part 30: Determination of 44 Elements", the sandstone and coal obtained from the drilling samples were digested and the content of strategic critical metal uranium was tested using inductively coupled plasma mass spectrometry (ICP-MS).

[0041] Step 2: Select coal-rock and sandstone-type uranium deposits with a thickness of more than 2m, impermeable roof and floor, and uranium contents in coal ash and sandstone higher than 1000μg / g and 0.01% respectively as research objects, and conduct subsequent underground gasification of coal samples and in-situ neutral leaching of sandstone-coal-rock uranium deposits to jointly mine uranium resources.

[0042] Step 3: Mineral composition and uranium-containing carrier minerals in coal and sandstone.

[0043] X-ray diffractometer (XRD) and scanning electron microscope energy dispersive spectrometer (SEM-EDS) were used to examine the mineral composition of the coal and sandstone. The results show that the main minerals in the coal are quartz, kaolinite, and pyrite, accompanied by minor amounts of calcite, illite, gypsum, sphalerite, rutile, uraninite, pitchblende, and titanium-bearing uranium minerals. The main minerals in the sandstone are quartz, accompanied by minor amounts of kaolinite, illite, pyrite, calcite, orthoclase, pitchblende, uraninite, calcite, calcite, calcite, calcite, and titanium-bearing uranium minerals. Among them, the uranium carrier minerals in coal-type uranium deposits are mainly uraninite and pitchblende, with minor amounts of titanium-bearing uranium minerals; the uranium carrier minerals in sandstone-type uranium deposits are mainly pitchblende, with minor amounts of uraninite, titanium-bearing uranium minerals, calcite, and calcite.

[0044] Step 4: Occurrence of strategic critical metal uranium in gasification coal ash and sandstone.

[0045] A step-by-step chemical extraction experiment was used to determine the occurrence state of uranium in sandstone and gasified coal ash. The specific operation is as follows:

[0046] 4.1. Weigh 2 g of a 200-mesh coal or sandstone sample into a 100-mL centrifuge tube. Add 60 mL of a 1 mol / L magnesium chloride (MgCl2) solution and allow to react in an oscillating oven at 200 rpm and 25°C for 1 h. Centrifuge the supernatant in the tube at 4000 rpm for 5-10 min. The supernatant is exchangeable, and the residue at the bottom (residue I) is dried at 90°C to constant weight.

[0047] 4.2. Add 60 mL of 1 mol / L sodium acetate (CH3COONa) solution to the residue I, adjust the pH to 5 with acetic acid (CH3COOH), and place in an oscillating box at 200 r / min and 25°C for 8 h. After centrifugation, the supernatant is in the carbonate state, and the bottom residue (residue II) is dried at 90°C to constant weight.

[0048] 4.3. Add 60 mL of a 0.04 mol / L hydroxylamine hydrochloride (NH2OH·HCl) solution prepared with 25% acetic acid (CH3COOH) to the residue II. Place the mixture in an oscillating oven at 200 rpm and 95°C for 4 h. After centrifugation, the supernatant is in the form of iron and manganese oxides. Dry the residue at the bottom (residue III) at 90°C to constant weight.

[0049] 4.4. Add 10 mL of 0.02 mol / L nitric acid (HNO3) and 30 mL of 30% hydrogen peroxide solution to Residue III. Adjust the pH to 2 with HNO3. Place the mixture in an oscillating oven at 200 rpm and 85°C for 5 h. After cooling, add 20 mL of a 1 mol / L ammonium acetate (CH3COONH4) solution prepared with 20% HNO3 solution. Place the mixture in an oscillating oven at 200 rpm and 25°C for 0.5 h. After centrifugation, the supernatant is the organic phase. Dry the residue (Residue IV) at 90°C to constant weight.

[0050] 4.5. Because high-temperature combustion produces an amorphous glassy phase in fumed coal ash, to more accurately determine the uranium distribution in the fumed coal ash, the fumed coal ash sample should be further dissolved after step 4.4 to separate into a glassy phase and a residue phase. This is accomplished by adding 40 mL of concentrated hydrofluoric acid (HF) and reacting in an oscillating oven at 200 rpm and 85°C for 2 hours. After centrifugation, the supernatant is a glassy phase primarily composed of aluminosilicates. The bottom residue (Residue IV) is dried at 90°C to constant weight. This step is not necessary for sandstone.

[0051] 4.6. The residue IV is digested in accordance with the national standard GB / T 14506.30-2010 "Chemical analysis methods of silicate rocks - Part 30: Determination of 44 element quantities", and the resulting digestion solution is in a residual state.

[0052] 4.7. Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the content of strategically important uranium in exchangeable, carbonate, iron-manganese oxide, organic, and residual phases. The results showed that uranium in sandstone primarily exists in the form of carbonate, followed by iron-manganese oxide, organic, and smaller amounts of exchangeable and residual phases. Uranium in gasified coal ash primarily exists in the form of glass and residual phases, followed by iron-manganese oxide and organic phases, with smaller amounts of exchangeable and carbonate phases. The preponderance of uranium in carbonate, glass, iron-manganese oxide, and organic phases indicates that uranium is more susceptible to leaching.

[0053] Step 5: Field drilling was conducted in the study area, including three groups of six gas holes 1, with two holes in each group. The system also included coalbed gasification channels 4 and sandstone blasting channels 5. First, an ignition rod was introduced into the coalbed gasification channel. A gasification ignition device 2 then entered the coal seam through the gas holes. A 50% oxygen-enriched air gasifier was injected through the holes and ignited, gasifying the coal. Combustible gases (CO, H2, CH4, etc.) and non-combustible gases (CO2, etc.) produced by coal gasification were discharged through the gas holes and separated by a surface gas recovery and separation device 3. The CO2 could be used for subsequent in-situ neutral leaching, while the combustible gas could be used as clean gas fuel for power plants and other applications.

[0054] Step 6: Due to the low degree of consolidation in the sandstone layer, the sandstone-type uranium deposits above the coal seam are initially crushed after coal gasification. Explosive materials are delivered to the sandstone layer through the sandstone crushing channel. Ground detonators then crush the sandstone blocks, further fragmenting them and facilitating subsequent uranium leaching. The amount of blasting material used does not damage the sandstone roof, ensuring a stable roof structure.

[0055] Step 7: In-situ neutral leaching of uranium.

[0056] Carbon dioxide (CO2) and oxygen (O2) are introduced through the pores, where O2 is an oxidant that oxidizes tetravalent uranium to hexavalent uranium. Since the sandstone layer is rich in groundwater, the introduced CO2 dissolves in the groundwater to form HCO3 - , and then reacts with the oxidized hexavalent uranium to leach out the strategic key metal uranium. The reaction mechanism is as follows:

[0057] CO2+H2O=H2CO3

[0058]

[0059] 2UO2+O2=2UO3

[0060] UO3+2HCO3 - =[UO2(CO3)2] 2- +H2O

[0061] [UO2(CO3)2]2- +HCO3 - =[UO2(CO3)3] 4- +H +

[0062] Compared with the huge impact of acid (sulfuric acid) and alkaline (ammonium bicarbonate, sodium bicarbonate, sodium carbonate) leaching on the groundwater environment, and the fact that acid and alkaline leaching are prone to produce precipitation and blockage of channels, which is not conducive to the mining of uranium in coal and sandstone uranium deposits, neutral leaching of uranium uses CO2 and groundwater to prepare the leaching agent, and O2 as the oxidant. It has the advantages of mild leaching environment, high resource recovery rate, and small impact on the groundwater environment. At the same time, it makes full use of CO2, which is of great significance to the protection of the ecosystem.

[0063] Step 8: The extraction device 6 is sent to the underground leaching position through the two low-position air holes, and the uranium-rich leachate is extracted through the air holes to the ground leachate storage device 7, and then transported to the leachate treatment plant to recover and purify the strategic critical metal uranium.

[0064] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for in-situ collaborative development of coal-rock-sandstone type uranium deposits, characterized in that: This includes the following methods: Step 1: Digest the sampled sandstone and coal and test the content of strategic critical metal uranium using inductively coupled plasma mass spectrometry; Step 2: Select coal-rock and sandstone-type uranium deposits with a thickness greater than a, impermeable roof and floor, and uranium content in coal ash and sandstone higher than the set value as research objects, and conduct subsequent underground coal gasification and in-situ neutral leaching of sandstone-coal-rock uranium deposits to jointly mine uranium resources; Step 3: Detect the mineral composition of coal and sandstone and uranium-containing carrier minerals to obtain their composition; Step 4: Use step-by-step chemical extraction experiments to determine the occurrence state of uranium in sandstone and simulated gasification coal ash; Step 5: Field drilling is carried out in the study area, including several groups of gas holes, coal seam gasification channels and sandstone blasting channels are opened in the lower part of the coal seam and sandstone layer, and then the coal is gasified; Step 6: After coal gasification, the sandstone-type uranium ore above the coal seam is initially crushed; the sandstone layer is crushed through the sandstone blasting channel, so that the sandstone blocks are further broken up, which is conducive to the subsequent uranium leaching; Step 7: Use the pores to introduce CO2 and O2, O2 oxidizes the tetravalent uranium to hexavalent uranium; because the sandstone layer is rich in groundwater, the introduced CO2 dissolves in the groundwater to form HCO3 - , which then reacts with the oxidized hexavalent uranium to leach out the strategic critical metal uranium; Step 8: Use the low-level air holes to send the extraction device to the underground leaching location, extract the uranium-rich leachate through the air holes to the ground leachate storage device, and transport it to the leachate treatment plant to recover and purify the strategic critical metal uranium.

2. The method for in-situ collaborative development of coal-rock-sandstone type uranium deposits according to claim 1, characterized in that: In step 1, the sandstone and coal obtained from the pore sampling were digested according to the national standard GB / T 14506.30-2010 "Chemical analysis methods of silicate rocks - Part 30: Determination of 44 elements".

3. The method for in-situ collaborative development of coal-rock-sandstone type uranium deposits according to claim 1, characterized in that: In step 2, the thickness a of the coal seam and sandstone layer is set to 2m, and the coal rock type and sandstone type uranium deposits with uranium contents in the coal ash and sandstone higher than 1000μg / g and 0.01% respectively are studied.

4. The method for in-situ collaborative development of coal-rock-sandstone type uranium deposits according to claim 1, characterized in that: In step three, the mineral composition of coal and sandstone is detected using an X-ray diffractometer and a scanning electron microscope energy dispersive spectrometer.

5. The method for in-situ collaborative development of coal-rock-sandstone type uranium deposits according to claim 1, characterized in that: The specific methods in step 4 include: 4.

1. Weigh 2 g of 200-mesh gasified fly ash or sandstone sample into a 100-mL centrifuge tube, add 60 mL of 1 mol / L magnesium chloride solution, and place in an oscillating oven at 200 rpm and 25°C for 1 h. Centrifuge the supernatant in the centrifuge tube at 4000 rpm for 5-10 min, separating the supernatant to be exchangeable. Dry the residue at the bottom, i.e., Residue I, at 90°C to constant weight. 4.

2. Add 60 mL of 1 mol / L sodium acetate solution to Residue I, adjust the pH to 5 with acetic acid, and place in an oscillating oven at 200 rpm and 25°C for 8 h. After centrifugation, the supernatant is the carbonate state, and the bottom residue, Residue II, is dried at 90°C to constant weight. 4.

3. Add 60 mL of a 0.04 mol / L hydroxylamine hydrochloride solution prepared in 25% acetic acid to Residue II. Place in an oscillating oven at 200 rpm and 95°C for 4 h. After centrifugation, the supernatant is iron-manganese oxide. Dry the residue at the bottom, Residue III, at 90°C to constant weight. 4.

4. Add 10 mL of 0.02 mol / L nitric acid and 30 mL of 30% hydrogen peroxide solution to the residue III, adjust the pH to 2 with nitric acid, and place in an oscillating oven at 200 rpm and 85°C for 5 h; After cooling, add 20 mL of 1 mol / L ammonium acetate solution prepared with 20% nitric acid solution, place in an oscillating box at 200 r / min and 25°C to react for 0.5 h, centrifuge, and the supernatant is the organic phase. The bottom residue, i.e., residue IV, is dried at 90°C to constant weight. 4.

5. Since the gasified coal ash has an amorphous glass phase after high-temperature combustion, in order to more accurately determine the occurrence state of uranium in the gasified coal ash, the gasified coal ash sample needs to be further dissolved after step 4.4 to separate into the glass phase and the residue phase; By adding 40 mL of concentrated hydrofluoric acid, placing it in an oscillating box at 200 r / min and 85°C for 2 hours, the supernatant after centrifugation is a glassy phase containing aluminosilicates. The bottom residue, residue IV, is dried at 90°C to constant weight. This step is not required for sandstone. 4.

6. Digest the residue IV in accordance with the national standard GB / T 14506.30-2010 "Chemical Analysis Methods of Silicate Rocks - Part 30: Determination of 44 Elements", and the resulting digestion solution is in the residual state; 4.

7. The content of strategic key metal uranium in exchangeable, carbonate, iron-manganese oxide, organic and residual states shall be tested by inductively coupled plasma mass spectrometry.

6. The method for in-situ collaborative development of coal-rock-sandstone type uranium deposits according to claim 1, characterized in that: The specific reaction mechanism in step 7 is as follows: CO2+H2O=H2CO3 2UO2+O2=2UO3 <h2 style=";text-align:left;direction:ltr">UO3+2HCO3<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> =[UO2(CO3)2]<h2 style=";text-align:left;direction:ltr"> 2- <h2 style=";text-align:left;direction:ltr"> +H2O [UO2(CO3)2] 2- +HCO3 - =[UO2(CO3)3] 4- +H + 。

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