A method and system for pre-treatment of a neutral leaching uranium injection solution system
By using cation exchange resin and hydrochloric acid pretreatment during CO2+O2 in-situ uranium mining, and adjusting the pH with O2 and CO2, the problem of ore layer blockage caused by CaCO3 precipitation was solved, achieving stable operation of the mining area and improving resource utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING RESEARCH INSTITUTE OF CHEMICAL ENGINEERING AND METALLURGY
- Filing Date
- 2025-04-11
- Publication Date
- 2026-07-14
AI Technical Summary
In the CO2+O2 in-situ leaching process of uranium mining, excessively high pH, HCO3- concentration, Ca2+ concentration, and Mg2+ concentration in the leaching solution can lead to CaCO3 precipitation, causing blockage of the ore-bearing layer and affecting the stable operation of the uranium mining process.
Two series fixed-bed adsorption towers are used, and cation exchange resins are installed. The resins are pretreated with hydrochloric acid solution, and the pH of the solution is adjusted by combining O2 and CO2 to reduce the enrichment of Ca2+ and Mg2+. Macroporous cation exchange resins are used for adsorption to form a neutral uranium leaching injection system.
It effectively reduces the enrichment of cations such as Ca2+ and Mg2+ in the leachate, lowers the risk of forming insoluble compounds, maintains the stable operation of the injection system in the mining area, avoids dead zones in ore leaching and permanent chemical blockage, and improves resource utilization.
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Figure CN122377162A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of in-situ leaching uranium mining technology, specifically to a pretreatment method and system for a neutral in-situ leaching uranium injection system. Background Technology
[0002] In-situ leaching of uranium refers to a uranium mining process where, under natural burial conditions, a leaching solution is injected into a sandstone-type uranium ore layer. The leaching solution reacts chemically with the ore to form a uranium-bearing leachate, which is then pumped to the surface via a pumping borehole for hydrometallurgical recovery. The CO2+O2 in-situ leaching process is my country's third-generation uranium mining and metallurgical technology. During in-situ leaching, after the leaching solution reacts with the minerals in the ore-bearing layer, uranium is leached from the ore. However, due to the increased mineralization of the groundwater, chemical precipitation occurs, leading to blockage of the ore-bearing layer.
[0003] Previous studies have shown that CaCO3 and MgCO3 precipitation is a significant cause of ore-bearing strata blockage during CO2+O2 in-situ leaching of uranium. The pH and HCO3 content of the leaching solution also play a role. - Concentration, Ca 2+ Concentration, Mg 2+ Concentration is the main factor affecting CaCO3 precipitation; excessively high pH and HCO3 concentration can also cause precipitation. - Concentration, Ca 2+ Concentration, Mg 2+ Both concentrations will cause CaCO3 to precipitate.
[0004] The saturation index, based on thermodynamics, is a hydrogeochemical parameter used to determine and evaluate the dissolution, equilibrium, or precipitation state of sparingly soluble compounds in a solid-liquid system; in other words, it determines the hydrogeochemical state of minerals in water. Its value is equal to the ion activity product (Isaturation index) of the sparingly soluble compound. AP The logarithm of the ratio of its solubility product constant (Ksp), i.e.
[0005] SI = lg(I) AP / K sp ).
[0006] SI is the saturation index of sparingly soluble compounds, and Ksp is the solubility product of sparingly soluble compounds.
[0007] Taking CaCO3 as an example, when the saturation index SI of calcium ions combining with bicarbonate ions is 0, the calcium ions and bicarbonate ions are in a dissolution-precipitation equilibrium state; when SI < 0, the solution is unsaturated and no precipitation occurs; and when SI > 0, calcium carbonate precipitate is formed. In CO2+O2 uranium leaching, under the same pH conditions, the calcium ions in the leaching solution... 2+ The higher the concentration, the more HCO3 precipitates from CaCO3. - The lower the concentration threshold, the more easily CaCO3 precipitates. At the same HCO3 concentration... -Under certain concentration conditions, the Ca in the leaching solution 2+ The lower the concentration, the higher the pH threshold for CaCO3 precipitation. 2+ When the concentration is constant, HCO3 - The higher the concentration, the lower the pH threshold for CaCO3 precipitation. Summary of the Invention
[0008] The purpose of this application is to provide a pretreatment method and system for a neutral leaching uranium injection system to solve the above-mentioned technical problems.
[0009] The following technical solution is adopted in this application:
[0010] A pretreatment method for a neutral leaching uranium injection system includes:
[0011] Step 1: Install cation exchange resins in two series-connected fixed-bed adsorption towers respectively;
[0012] Step 2: The 50%-X leachate is sequentially injected into the fixed bed adsorption tower for adsorption. At this time, the front tower is the first fixed bed adsorption tower and the rear tower is the second fixed bed adsorption tower. The adsorption tail liquid is returned to the leachate to obtain the treated solution.
[0013] Step 3: When the cation concentration in the adsorption tail liquid in Step 2 is the same as the cation concentration before entering the tower, stop the adsorption in the front tower and use the rear tower for adsorption alone;
[0014] Step 4: Clean the front tower described in Step 3, and then add it back into the adsorption system as the rear tower. At this time, the front tower is the second fixed-bed adsorption tower, and the rear tower is the first fixed-bed adsorption tower.
[0015] Step 5: Repeat steps 2-4;
[0016] Step 6: When the pH of the treated solution is ≤7.5, add O2 to a concentration of 300-500 mg / L and then inject it into the mineral-bearing aquifer; when the pH of the treated solution is >7.5, add CO2 to a concentration of 300-800 mg / L and add O2 to a concentration of 300-500 mg / L before injecting it into the mineral-bearing aquifer.
[0017] Preferably, the cation exchange resin includes a gel-type cation exchange resin or a macroporous cation exchange resin.
[0018] Preferably, the cation exchange resin described in step 1 is pretreated with a 0.01-0.5 mol / L hydrochloric acid solution for 12-24 hours.
[0019] Preferably, the concentration of the hydrochloric acid solution is 0.05-0.2 mol / L.
[0020] Preferably, the contact time in step 2 is 5-9 minutes.
[0021] Preferably, in step 4, the upstream column is eluted with a 0.01-0.5 mol / L hydrochloric acid solution, and the elution is stopped when the cation concentration in the effluent of the upstream column no longer changes.
[0022] Preferably, the concentration of the hydrochloric acid solution is 0.05-0.2 mol / L.
[0023] A pretreatment system for a neutral uranium leaching injection system includes the adsorption system involved in any of the above-described pretreatment methods, wherein the adsorption system includes an adsorption device and its control system.
[0024] Preferably, the adsorption device includes a tee installed on the main inlet pipe, and the cation exchange resin is installed in each of the two series-connected fixed-bed adsorption towers.
[0025] Current in-situ uranium leaching processes typically involve multiple adsorption steps to improve leaching efficiency, but the improvement effect is relatively limited.
[0026] Compared with the prior art, the beneficial effects of this application include:
[0027] After practical application, the preprocessing method of this application effectively reduced Ca 2+ Mg 2+ The enrichment of cations in the leachate reduces the risk of the formation of sparingly soluble compounds, maintains the stable operation of the injection system in the mining area, avoids the formation of dead zones in the ore leaching, prevents the formation of permanent chemical blockages from the root, and further improves resource utilization.
[0028] The pretreatment system of this application can efficiently adsorb leachate according to actual production conditions, and configure corresponding adsorption devices according to the pretreatment method to maintain the smooth and stable operation of the pretreatment system and the entire process. Attached Figure Description
[0029] Figure 1 This is a line graph showing the instantaneous flow rate of the original injection wells in the mining area.
[0030] Figure 2 This is a line graph showing the instantaneous flow rate of the injection hole after pretreatment. Detailed Implementation
[0031] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply.
[0032] A pretreatment method for a neutral leaching uranium injection system includes:
[0033] Step 1: Install cation exchange resins in two series fixed-bed adsorption towers respectively. The cation exchange resins include gel-type cation exchange resins or macroporous cation exchange resins, preferably macroporous cation exchange resins.
[0034] Step 2: Pretreatment of the cation exchange resin from Step 1 with a 0.01-0.5 mol / L hydrochloric acid solution, preferably 0.05-0.2 mol / L, for 12-24 hours. 50% of the leachate is then sequentially injected into a fixed-bed adsorption tower for adsorption. The preceding tower is the first fixed-bed adsorption tower, and the following tower is the second fixed-bed adsorption tower, with a contact time of 5-9 minutes. The leached ions Ca in the adsorption tail liquid are analyzed. 2+ The concentration of the adsorption tail liquid is adjusted, and the liquid is returned to the leachate to obtain the treated solution.
[0035] Step 3: When the cation concentration in the adsorption tail liquid in Step 2 is the same as the cation concentration before entering the tower, stop the adsorption in the front tower and use the rear tower for adsorption alone.
[0036] Step 4: Clean the pre-adsorption tower from Step 3 using a 0.01-0.5 mol / L hydrochloric acid solution, preferably 0.05-0.2 mol / L. Wash the pre-adsorption tower until the cation concentration in the effluent no longer changes, then stop washing. Then, add it back in series as the post-adsorption tower to the adsorption system. In this case, the pre-adsorption tower becomes the second fixed-bed adsorption tower, and the post-adsorption tower becomes the first fixed-bed adsorption tower. In this application, the adsorption system refers to the solution injected into the ore-bearing aquifer during the uranium leaching process.
[0037] Step 5: Repeat steps 2-4.
[0038] Step 6: When the pH of the treated solution is ≤7.5, add O2 to a concentration of 300-500 mg / L and then inject it into the mineral-bearing aquifer; when the pH of the treated solution is >7.5, add CO2 to a concentration of 300-800 mg / L and O2 to a concentration of 300-500 mg / L and then inject it into the mineral-bearing aquifer.
[0039] After the leaching solution is pretreated by the method described in this application, it can be subjected to conventional in-situ leaching of uranium, which can effectively prevent problems such as ore layer blockage and subsequent resin poisoning, and reduce discontinuous operation of the process caused by hole washing and resin cleaning.
[0040] Conventional uranium leaching methods include CO2+O2 leaching, O2-only leaching, and leaching processes such as CO2+NH4HCO3+O2. The solution treated in this application is injected into the ore-bearing aquifer and then processed using conventional methods.
[0041] Example 1
[0042] In a low-grade sandstone uranium deposit in Inner Mongolia, in-situ leaching of uranium using the CO2+O2 process began in 2015. The leaching agent contained c(CO2) ~500 mg / L and c(O2) ~300 mg / L. As the leaching reaction proceeded, ions in the leachate continuously accumulated. The chemical composition of the leachate from a pumping well in the northern part of the test area at different times was analyzed, and the results are shown in Table 1.
[0043] Table 1
[0044] time pH <![CDATA[Ca 2+ ]]> <![CDATA[Mg 2+ ]]> <![CDATA[HCO3 - ]]> <![CDATA[SO4 2- ]]> <![CDATA[Al 3+ ]]> <![CDATA[U 4+ ]]> <![CDATA[U 6+ ]]> 2019-6 6.67 145 17.45 1498 699 0.21 0.019 7.33 2020-1 6.61 165 23.52 1671 705 0.51 0.029 16.73 2020-12 6.65 192 30.31 1722 799 0.62 0.023 17.08
[0045] The results show that Ca 2+ Mg 2+ Same as HCO3 - The saturation index SI > 0 indicates a supersaturated state, leading to ore layer blockage.
[0046] Meanwhile, the changes in the pumping volume of this well from 2019 to 2020 were detected and analyzed, and the results are as follows: Figure 1 As shown. From Figure 1 It can be seen that from the beginning of 2019 to the end of 2020, the instantaneous flow rate of the extraction orifice increased from ~8m³ / h. 3 / h decreased to 5m 3 / h, the decrease is significant. Figure 2 This indicates that during the migration of the solution in the formation, local sparingly soluble precipitates with a saturation index greater than 0 appeared, thus forming a blockage in the ore layer and causing a decrease in the pumping volume.
[0047] To address existing operational issues in the mining area, the pretreatment method of the neutral leaching uranium injection system proposed in this application is adopted, including:
[0048] Step 1: Install macroporous cation exchange resin (D113) in two series fixed-bed adsorption towers.
[0049] Step 2: Pre-treat the cation exchange resin from Step 1 with a 0.05 mol / L hydrochloric acid solution for 12 hours. Add 50% leachate (flow rate approximately 3 m³ / h). 3The solution is sequentially injected into a fixed-bed adsorption tower for adsorption. The preceding tower is the first fixed-bed adsorption tower, and the following tower is the second fixed-bed adsorption tower, with a contact time of 9 minutes. The leached ions Ca in the adsorption tail liquid are analyzed. 2+ The concentration of the adsorption tail liquid is adjusted, and the liquid is returned to the leachate to obtain the treated solution.
[0050] Step 3: When the cation concentration in the adsorption tail liquid in Step 2 is the same as the cation concentration before entering the tower, stop the adsorption in the front tower and use the rear tower for adsorption alone.
[0051] Step 4: Clean the foreground column from Step 3 by rinsing it with a 0.05 mol / L hydrochloric acid solution. Stop cleaning when the cation concentration in the effluent from the foreground column no longer changes. Transfer the washed solution to the evaporation tank. Then, add it back into the adsorption system as the background column. At this point, the foreground column becomes the second fixed-bed adsorption column, and the background column becomes the first fixed-bed adsorption column.
[0052] Step 5: After the second fixed-bed adsorption tower is saturated, repeat steps 2-4.
[0053] Step 6: The pH of the treated solution is 6.8. At this point, add O2 to a concentration of 300 mg / L and inject it into the mineral-bearing aquifer.
[0054] After the above pretreatment, the change in the pumping volume in the mining area is as follows: Figure 2 As shown. After three adsorption cycles, the pumping flow rate was reduced from 5 m³ / h. 3 / h rose to 6.5m 3 / h.
[0055] Example 2
[0056] The pretreatment system of Example 1 includes an adsorption device and its control system. The adsorption device includes a tee installed on the main inlet pipe and two series-connected fixed-bed adsorption towers, each equipped with a macroporous cation exchange resin (D113). The outlet of the fixed-bed adsorption tower is returned to the injection system.
[0057] Finally, it should be noted that although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A pretreatment method for a neutral leaching uranium injection system, characterized in that, include: Step 1: Install cation exchange resins in two series-connected fixed-bed adsorption towers respectively; Step 2: 50% of the leachate is sequentially injected into the fixed-bed adsorption tower for adsorption. At this time, the front tower is the first fixed-bed adsorption tower and the rear tower is the second fixed-bed adsorption tower. The adsorption tail liquid is returned to the leachate to obtain the treated solution. Step 3: When the cation concentration in the adsorption tail liquid in Step 2 is the same as the cation concentration before entering the tower, stop the adsorption in the front tower and use the rear tower for adsorption alone; Step 4: Clean the front tower described in Step 3, and then add it back into the adsorption system as the rear tower. At this time, the front tower is the second fixed-bed adsorption tower, and the rear tower is the first fixed-bed adsorption tower. Step 5: Repeat steps 2-4; Step 6: When the pH of the treated solution is ≤7.5, add O2 to a concentration of 300-500 mg / L and then inject it into the mineral-bearing aquifer; when the pH of the treated solution is >7.5, add CO2 to a concentration of 300-800 mg / L and add O2 to a concentration of 300-500 mg / L before injecting it into the mineral-bearing aquifer.
2. The pretreatment method for the neutral ground leaching uranium injection system according to claim 1, characterized in that, The cation exchange resin includes gel-type cation exchange resin or macroporous cation exchange resin.
3. The pretreatment method for the neutral ground leaching uranium injection system according to claim 1, characterized in that, The cation exchange resin described in step 1 was pretreated with a 0.01-0.5 mol / L hydrochloric acid solution for 12-24 hours.
4. The pretreatment method for the neutral leaching uranium injection system according to claim 3, characterized in that, The concentration of the hydrochloric acid solution is 0.05-0.2 mol / L.
5. The pretreatment method for the neutral leaching uranium injection system according to claim 1, characterized in that, The contact time in step 2 is 5-9 minutes.
6. The pretreatment method for the neutral leaching uranium injection system according to claim 1, characterized in that, In step 4, the upstream column is eluted with a 0.01-0.5 mol / L hydrochloric acid solution. The elution is stopped when the cation concentration in the effluent of the upstream column no longer changes.
7. The pretreatment method for the neutral leaching uranium injection system according to claim 6, characterized in that, The concentration of the hydrochloric acid solution is 0.05-0.2 mol / L.
8. A pretreatment system for a neutral leaching uranium injection system, characterized in that, The adsorption system includes the pretreatment method described in any one of claims 1-7, wherein the adsorption system includes an adsorption device and its control system.
9. The pretreatment system of the neutral leaching uranium injection system according to claim 8, characterized in that, The adsorption device includes a tee installed on the main inlet pipe, and two fixed-bed adsorption towers connected in series, each containing a cation exchange resin.