Method for deeply purifying free chlorine in cobalt electrodeposition solution of chlorination system
Through the combined physical and chemical method and micro negative pressure system, combined with gas-liquid separation and self-circulation, the problem of chlorine residue in cobalt chloride electrocobalt production is solved, efficient deep purification and recycling of metal cobalt, reducing cost and control difficulty.
Patent Information
- Application Number
- CN202510391533.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-07-08
AI Technical Summary
In the prior art, during the production process of cobalt chloride electrocobalt, residual chlorine gas cannot be completely removed, resulting in oxidation and decomposition of the extractant, which is high cost and difficult to control, affecting subsequent equipment and systems.
The combined physical and chemical method is adopted to gradually remove chlorine through a micro-negative pressure system and chemical reaction, combined with gas-liquid separation and self-circulation, to form a cobalt chloride and recover metal cobalt chips, forming a micro-negative pressure system to promote chlorine escape, and use the Clabellon equation to control the pressure to achieve deep purification.
Thoroughly remove free chlorine from cobalt chloride solution, reduce oxidation, reduce operating costs, improve cobalt metal recovery rate, ensure the purity of the solution, and realize the preparation of high-purity cobalt chloride solution.
Smart Images
Figure CN120272993A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of industrial deep purification and chlorine removal, and particularly relates to a method for deeply purifying free chlorine in an electrowinning cobalt solution of a chlorination system. Background Art
[0002] In the production of electrolytic cobalt from cobalt chloride, metallic cobalt plates are produced at the cathode and chlorine gas is produced at the anode. After the electrowinning solution passes through the dechlorination equipment, residual chlorine gas generally exists and cannot be completely removed, which affects the subsequent equipment and production system. When the post-electrowinning cobalt solution enters the extraction stripping section, it will oxidize the extractant P507 (chemically named 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) or Cyanex272 (chemically named bis(2,4,4-trimethylpentyl) phosphinic acid), resulting in the oxidative decomposition of the extractant. Therefore, deep purification must be carried out.
[0003] Currently, the commonly used dechlorination methods are: vacuum dechlorination method, hydrogen peroxide oxidation method, and hydrochloric acid dechlorination method. The equipment investment for vacuum dechlorination is relatively high, the requirement for vacuum degree is high, its control is difficult, and the energy consumption is large. For the hydrogen peroxide oxidation method, the amount of hydrogen peroxide added is large and the operating cost is high. The hydrochloric acid dechlorination method cannot completely remove free chlorine, and the residual chlorine affects the subsequent stripping section. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to overcome the defects of large consumption of auxiliary materials, high cost, difficult control, and residual free chlorine in the above-mentioned prior art, and provide a method for deeply purifying free chlorine in the post-cobalt electrolysis solution by using a combined physical and chemical method.
[0005] For this purpose, the present invention adopts the following technical solutions: The first step of dechlorination: The circulating liquid of the post-electrowinning cell solution passes through a gas-liquid separator to remove most of the chlorine gas generated during the electrowinning process, and then passes through the No. 1 circulating tank and the No. 2 circulating tank. Through self-circulation, it passes through the upper nozzles in the tank, forming a large contact area with the air. A micro-negative pressure system is connected in the tank, continuously pumping out the gas in the tank to form a micro-negative pressure system, making the solution in contact with the air more likely to escape chlorine gas and removing the dissolved chlorine gas in the solution. The second step of dechlorination: The post-electrowinning cobalt solution undergoes self-circulation in the post-electrowinning cobalt solution circulating tank, passes through the upper nozzles in the tank, forms a large contact area with the air. A micro-negative pressure system is connected in the tank, continuously pumping out the gas in the tank to form a micro-negative pressure system, making the solution in contact with the air more likely to escape chlorine gas. The third step of dechlorination: The post-electrowinning solution reacts chemically with metallic cobalt chips to consume the free chlorine in the solution and generate cobalt chloride.
[0006] It can not only effectively separate the cobalt chloride solution from free chlorine, but also realize the recycling of waste metallic cobalt and regenerate cobalt chloride solution to achieve the purpose of preparing high-purity cobalt chloride solution and removing free chlorine from the post-cobalt electrolysis solution.
[0007] The process flow of the present invention is: electrowinning cell - gas-liquid separator - No. 1 circulation tank - No. 2 circulation tank - No. 3 circulation tank - intermediate tank for electrowinning post-liquid - circulation tank for electrowinning post-liquid - dechlorination reaction tank - storage tank for post-dechlorination liquid
[0008] The principle of deeply purifying free chlorine in the cobalt electrorefining solution of the present invention is as follows:
[0009] 1. According to the Clapeyron equation: PV = nRT, (where P is the pressure (Pa), V is the volume (m 3 ³), n is the amount of substance (mol), T is the thermodynamic temperature (K), and R is the gas constant). Under the condition of constant temperature, when the pressure becomes smaller, the volume will become larger. Therefore, under the condition of slightly negative pressure in the tank, the volume of the diffused gas will become larger, and more chlorine gas will escape, thus reducing the free chlorine dissolved in the solution.
[0010] 2. Free chlorine gas dissolves in water to form an acidic solution, which then undergoes a chemical reaction with metallic cobalt to generate cobalt chloride and hydrogen gas, thereby achieving the purpose of consuming free chlorine. The chemical equations are as follows:
[0011] H2O + Cl2 = HCl + HClO (1)
[0012] 2HCl + Co = CoCl2 + H2 ↑ (2)
[0013] 4HClO + 2Co = CoCl2 + Co(ClO)2 + 2H2O (3)
[0014] Specifically, a method for deeply purifying free chlorine in a cobalt chloride electrowinning solution includes the following steps:
[0015] (1) After the cobalt electrorefining solution flows out of the closed electrowinning cell, it first passes through a gas-liquid separator to remove most of the chlorine gas;
[0016] (2) The solution obtained in step (1) then enters the No. 1 circulation tank. The circulation tank circulates by itself through a pump, so that the solution passes through a spray head to form fine water droplets, and free chlorine gas is fully released;
[0017] (3) The solution obtained in step (2) overflows to the No. 2 circulation tank. The circulation tank circulates by itself through a pump, so that the solution passes through a spray head to form fine water droplets, and free chlorine gas is fully released;
[0018] (4) The solution obtained in step (3) overflows to the No. 3 circulation tank. The solution in the No. 3 tank is pumped into the closed electrowinning cell through a circulation pump for an electrowinning reaction to obtain cobalt plates. An overflow port is opened at the upper position of the No. 3 circulation tank, and the low-concentration solution overflows to the intermediate tank for electrowinning post-liquid by gravity;
[0019] (5) Pump the solution obtained in step (4) into the post-electrolytic cobalt solution circulation tank. The solution circulates by itself through a pump and forms fine water droplets through the nozzle at the top of the tank, fully releasing free chlorine gas.
[0020] (6) Pump the solution obtained in step (5) into the dechlorination reaction tank through a pump, allowing the cobalt chips to fully react with the post-electrolytic cobalt solution to deeply purify the residual chlorine in the solution.
[0021] (7) Let the solution obtained in step (6) flow into the post-dechlorination solution storage tank for standby.
[0022] Preferably, in step (1), the solution passes through a gas-liquid separator. The solution flows downward and the gas flows upward. The upper part of this device is connected to a negative pressure system, which continuously extracts the gas. Most of the gas is extracted from the solution in step (1), which is more conducive to the electrowinning tank being powered on for operation.
[0023] Preferably, in the three circulation tanks in steps (2), (3), and (4), the intermediate transfer tank for the post-electrolytic cobalt solution in step (4), and the post-electrolytic cobalt solution circulation tank in step (5), all are connected to a negative pressure system, which continuously extracts the escaped chlorine gas, maintaining a slightly negative pressure system inside the tank, facilitating the escape of free chlorine.
[0024] Preferably, in steps (2), (3), and (5), the No. 1 circulation tank, the No. 2 circulation tank, and the post-electrolytic cobalt solution circulation tank have a self-circulation function, enabling the solution to pass through the nozzle at the top of the tank to form fine water droplets, making it easier for the chlorine gas in the solution to escape.
[0025] Preferably, in step (5), the post-electrolytic cobalt solution is pumped into the dechlorination reaction tank through a pump. By controlling the flow rate, sufficient reaction time is given, allowing the cobalt chips to fully react with the solution to achieve the effect of deep chlorine removal.
[0026] Preferably, the metallic cobalt chips are obtained by collecting the defective products during the cutting operation of the product metallic cobalt plate. During the cutting operation, iron filings and dust will be incorporated. Before using the cobalt chips, iron removal operation needs to be carried out first. After soaking in hydrochloric acid solution, it can be rinsed clean with clear water.
[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0028] (1) It can completely remove the free chlorine in the post-electrolytic cobalt solution of cobalt chloride, achieving the purpose of deeply purifying free chlorine.
[0029] (2) It reduces the oxidizing property of the cobalt electrolyte solution and eliminates the oxidative decomposition and consumption of the extractant by free chlorine.
[0030] (3) The operating cost is low, no other reagents are added additionally, and no other impurities are generated, ensuring the purity of the cobalt chloride solution.
[0031] (4) Improve the direct recovery rate of cobalt metal, recycle the waste cobalt chips generated during the processing of metallic cobalt. The consumption of cobalt chips per cubic solution is 159 g - 387 g.
[0032] (5) It can reduce the acidity in the post-electrowinning solution of cobalt, which is beneficial to the subsequent recycling of the post-electrowinning solution of cobalt. Description of the Drawings
[0033] Figure 1 It is a process flow chart.
[0034] Figure 2 It is an equipment flow chart.
[0035] Figure 2 In the figure, 1 - cobalt electrowinning cell, 2 - gas-liquid separator, 3 - No. 1 circulation tank, 4 - No. 2 circulation tank, 5 - No. 3 circulation tank, 6 - intermediate transfer tank for post-electrowinning solution, 7 - post-electrowinning solution circulation tank, 8 - dechlorination reaction tank, 9 - storage tank for post-dechlorination solution, 10A - No. 1 circulation pump, 10B - No. 2 circulation pump, 11 - No. 3 circulation liquid inlet pump, 12 - post-electrowinning solution transfer pump, 13 - post-electrowinning solution circulation pump, 14 - flowmeter for electrowinning solution, 15 - dechlorination flowmeter, 16 - spray head, 17 - tail gas absorption system, 18 - liquid level gauge, 19 - chlorine gas detector, 20 - hydrogen gas detector, 21 - ceiling, 22 - feeding platform. Detailed Embodiments
[0036] To make the technical solutions described in the present invention clearer and more understandable to those skilled in the art, the following examples are listed for illustration. It should be noted that the following examples do not limit the scope of protection required by the present invention.
[0037] Figure 1 and Figure 2As shown, a method for deeply purifying free chlorine in an electrowinning cobalt solution in a chlorination system. This method mainly uses a combined physical and chemical method for deep dechlorination. After electrowinning cobalt in the electrolysis cell, the post-electrolysis solution passes through a gas-liquid separator to separate most of the insoluble gases and most of the chlorine gas, with a residence time of 1 minute. The solution enters the No. 1 circulation tank from the gas-liquid separator. Through the action of the circulation pump, the dissolved chlorine gas is released again. The residence time in the circulation tank is 0.5 hours, and the number of circulation times per hour in the circulation tank is 1 time. The solution overflows into the No. 2 circulation tank, and through the action of the circulation pump, the dissolved chlorine gas is released again. The solution overflows into the No. 3 circulation tank. Through the action of gravity sedimentation, the high-concentration cobalt chloride is pumped to the closed electrolysis cell by the circulation pump for electrowinning to produce metallic cobalt plates. The solution with a lower concentration in the No. 3 circulation tank enters the post-electrolysis solution transfer tank through the overflow pipeline, and is pumped into the post-electrolysis solution circulation tank by the pump. The residence time in the circulation tank is 3 hours, and the number of circulation times per hour in the circulation tank is 2 times, so the solution circulates 6 times / hour, fully contacting with slightly negative-pressure air to release the dissolved chlorine gas in the solution and reduce the free chlorine in the solution. Later, it is branched to the dechlorination reaction tank by the circulation pump. The reaction tank has an inlet at the bottom and an outlet at the top, and the reaction time is controlled within 10 - 50 minutes. After the reaction is completed, it overflows into the dechlorinated solution storage tank. Thus, the deep removal of free chlorine in the electrolytic cobalt solution is completed.
[0038] Example 1 of slightly negative-pressure chlorine extraction: The outlet liquid of the electrolysis cell has H + = 0.056. Through the self-circulation action of the circulation pump, in a slightly negative-pressure system, the solution circulates 1 - 5 times respectively, and the OH - and chlorine content in the tail gas absorption liquid are detected.
[0039] NaOH once twice three times four times five times OH-(mol / l) 0.087 0.086 0.085 0.081 0.080 0.079 Cl(g / L) 0.008 0.088 0.091 0.10 0.12 0.13 Chlorine extraction efficiency (%) 10.79 11.15 12.21 14.48 15.57
[0040] In this case, with each circulation, the negative-pressure chlorine extraction effect shows a slow upward trend. In the technical solution of the present invention, in the first dechlorination process, the number of solution circulation times needs to be greater than 1 time. Then, the free chlorine content in the solution can be reduced by 10.79%, and the cobalt chip consumption can be reduced by 8.97%.
[0041] Example 2 of slightly negative-pressure chlorine extraction: The post-electrolysis solution has H + = 0.062. Through the self-circulation action of the circulation pump, in a slightly negative-pressure system, the solution circulates 1 - 5 times respectively, and the OH - and chlorine content in the tail gas absorption liquid are detected.
[0042] NaOH once twice three times four times five times six times OH-(mol / l) 0.1 0.099 0.099 0.096 0.096 0.096 0.096 Cl(g / L) 0.0087 0.063 0.077 0.079 0.081 0.084 0.086 Chlorine extraction efficiency (%) 8.31 10.43 10.73 11.04 11.49 11.79
[0043] In this case, with each circulation, the negative-pressure chlorine extraction effect shows a slow upward trend. In the technical solution of the present invention, in the second dechlorination process, the number of solution circulation times needs to be greater than 1 time. Since the flow rate of the post-electrolysis solution is small, at 5 - 10 m 3Between / h, it is easier to achieve multiple cycles of solution circulation. In this case, when the solution is circulated under slightly negative pressure for 6 times to extract chlorine, the free chlorine content in the solution can be reduced by 11.79%, and the consumption of cobalt chips can be reduced by 9.80%.
[0044] Dechlorination reaction tank comparison case 1: After electrolytic cobalt liquid H + = 0.083. Using the liquid inlet method of flowing in from the top and out from the bottom, passing through cobalt chips, the free chlorine situation in the aqueous solution is detected with test paper. The aqueous solution contains free chlorine and the effluent is unqualified; after 2 reactions, the effluent is qualified and contains no free chlorine. After the cobalt chips are rinsed with hot water, dried and weighed, the single consumption of cobalt chips is 0.037 g / l.
[0045] Dechlorination reaction tank comparison case 2: After electrolytic cobalt liquid H + = 0.083. Using the liquid inlet method of flowing in from the bottom and out from the top, passing through cobalt chips, the free chlorine situation in the aqueous solution is detected with test paper. The aqueous solution contains no free chlorine and the effluent is qualified. After the cobalt chips are rinsed with hot water, dried and weighed, the single consumption of cobalt chips is 0.037 g / l.
[0046] Dechlorination reaction tank comparison case 3: After electrolytic cobalt liquid H + = 0.1. Using the liquid inlet method of flowing in from the bottom and out from the top, and the solution is fed in by means of hot water insulation. The results show that when the solution at 50°C reacts with cobalt chips once, the test paper does not change color, but there is a faint pungent smell, which can be understood as reaching the reaction critical point. At high temperatures, it is beneficial to the progress of the dechlorination reaction. The single consumption of cobalt chips is 0.11 g / l.
[0047] Dechlorination reaction tank comparison case 4: After electrolytic cobalt liquid H + = 0.1. Using the liquid inlet method of flowing in from the bottom and out from the top, and the reaction situation of the solution at room temperature. The results show that when reacting at room temperature, after 1 reaction, the test paper changes color and the effluent is unqualified. It takes 2 reactions to reach the situation where the test paper does not change color and there is no pungent smell. The single consumption of cobalt chips is 0.148 g / l.
[0048] Dechlorination reaction tank case 5: After electrolytic cobalt liquid PH = 0.44, H + = 0.153. Using the method of maintaining heat at 50°C and flowing in from the bottom and out from the top. After a long-period reaction, the effluent situation is detected with test paper, and the dechlorinated liquid can continuously produce qualified effluent. The single consumption of cobalt chips is 0.387 g / l.
[0049] In summary of the above implementation cases, the acidity of the cobalt chloride solution after electrolytic cobalt is between 0.05 - 0.2. For cobalt chloride solutions with different acidities, different liquid inlet methods and different ambient temperatures for liquid inlet, the reaction between cobalt chips and the cobalt chloride solution after electrolytic cobalt can achieve the effect of complete dechlorination. After the cobalt chloride solution after electrolytic cobalt passes through the self-circulation system, the dissolved chlorine in the solution is fully released, the acidity of the solution will decrease, which is more conducive to the progress of deep dechlorination, and the single consumption of cobalt chips is reduced.
[0050] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.
Claims
1. A method for deeply purifying free chlorine in an electrowinning cobalt solution of a chlorination system, characterized in that, It includes the following steps: (1) After the electrolytic cobalt solution flows out of the closed electrolytic cell, it first passes through a gas-liquid separator to remove most of the chlorine gas; (2) The solution obtained in step (1) then enters the No. 1 circulation tank. Through the self-circulation of the pump in the circulation tank, the solution passes through the nozzles on the top of the tank to form fine water droplets, fully releasing the free chlorine gas; (3) The solution obtained in step (2) overflows to the No. 2 circulation tank. Through the self-circulation of the pump in the circulation tank, the solution passes through the nozzles on the top of the tank to form fine water droplets, fully releasing the free chlorine gas; (4) The solution obtained in step (3) overflows to the No. 3 circulation tank. The solution in the No. 3 tank is pumped into the closed electrolytic cell by a circulation pump for electrolytic reaction to obtain cobalt plates. An overflow port is opened at the upper position of the No. 3 circulation tank. Through the action of gravity, the low-concentration solution overflows to the intermediate tank for the post-electrolytic cobalt solution; (5) The solution obtained in step (4) is pumped into the post-electrolytic cobalt solution circulation tank. The solution circulates by itself through the pump, passes through the nozzles on the top of the tank to form fine water droplets, and fully releases the free chlorine gas; (6) The solution obtained in step (5) is pumped into the dechlorination reaction tank by a pump, allowing the cobalt chips to fully react with the post-electrolytic cobalt solution to deeply purify the residual chlorine gas in the solution; (7) The solution obtained in step (6) flows into the storage tank for the post-dechlorination solution for standby.
2. The method for deep purification of free chlorine according to claim 1, characterized in that In step (1), the solution passes through the gas-water separator. The solution goes down and the gas goes up. The upper part of this device is connected to a negative pressure system to continuously extract the gas. Most of the gas is extracted from the solution in step (1).
3. The method for deeply purifying free chlorine according to claim 1, wherein In the three circulation tanks described in steps (2), (3), and (4), the intermediate tank for the post-electrolytic cobalt solution in step (4), and the post-electrolytic cobalt solution circulation tank in step (5), all are connected to a negative pressure system to continuously extract the escaped chlorine gas and maintain a slightly negative pressure system in the tank.
4. The method for deep purification of free chlorine according to claim 1, wherein In steps (2), (3), and (5), in the No. 1 circulation tank, the No. 2 circulation tank, and the post-electrolytic cobalt solution circulation tank, through the self-circulation function, the solution passes through the nozzles on the top of the tank to form fine particles, making it easier for the chlorine gas in the solution to escape.
5. The method for deep purification of free chlorine according to claim 1, characterized in that, In step (5), the solution in the post-electrolytic cobalt solution tank is pumped into the dechlorination reaction tank by a pump. By controlling the flow rate, sufficient reaction time is given to allow the cobalt chips to fully react with the solution, achieving the effect of deep chlorine removal.
6. The method for deep purification of free chlorine according to claim 1, wherein The metallic cobalt chips are obtained from the collection of defective products during the cutting operation of the product metallic cobalt plates. During the cutting operation, iron chips and dust will be incorporated. Before using the cobalt chips, it is necessary to first perform iron removal operations. First, soak them in hydrochloric acid solution and then rinse them clean with water.