Method for improving available chlorine content of sodium hypochlorite in chlorination system cobalt electrodeposition chlorine gas absorption process

Abstract

The invention belongs to the technical field of colored hydrometallurgy processes, and particularly discloses a method for increasing the available chlorine content of sodium hypochlorite in a chlorination system cobalt electrodeposition chlorine gas absorption procedure, which comprises the following steps: introducing circulating water into a liquid inlet of a primary absorption tower, introducing chlorine gas into a gas inlet of the primary absorption tower, and introducing chlorine gas into a gas outlet of the primary absorption tower; an absorbent is introduced into a liquid inlet of the five-stage absorption tower, the volume ratio of water to alkali of the absorbent is (1-3): 1, chlorine is mainly subjected to step-by-step alkali absorption, the temperature during absorption is controlled to be 35-40 DEG C through a cooling plate heat exchanger, a generated sodium hypochlorite solution is discharged out of the second-stage absorption tower from a sodium hypochlorite discharge port, and the discharge potential of the sodium hypochlorite solution is controlled to be 450-500 mv; circulating water is introduced into a liquid inlet of the six-stage absorption tower to cool chlorine, generated chlorine water is discharged out of the six-stage absorption tower from a liquid outlet, and chlorine is discharged from a purified tail gas outlet of the six-stage absorption tower after being detected and analyzed to be qualified; the discharge amount of alkaline wastewater is reduced, the production environmental protection risk is reduced, and the available chlorine content of sodium hypochlorite is improved.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous hydrometallurgical process technology, specifically relating to a method for increasing the effective chlorine content of sodium hypochlorite in the cobalt chlorine absorption process of a chlorination system. Background Technology

[0002] Cobalt electrowinning employs a chloride-based insoluble anode electrowinning process. During production, a vacuum pump transports the chlorine gas generated at the anode of the electrolytic cell to an alkali absorption system, where it is absorbed by a sodium hydroxide solution, ensuring the exhaust gas meets emission standards. However, the available chlorine content of sodium hypochlorite is significantly affected by temperature. In the high-temperature summer season, sodium hypochlorite is prone to decomposition, and the alkali-absorbed liquid can only be discharged as wastewater, leading to increased production costs.

[0003] Therefore, it is necessary to design a method to increase the effective chlorine content of sodium hypochlorite in the cobalt electrowinning chlorine absorption process of the chlorination system, thereby reducing the discharge of alkaline wastewater and lowering the environmental risks of production. Summary of the Invention

[0004] To address the problems of existing technologies, the purpose of this invention is to provide a method for increasing the effective chlorine content of sodium hypochlorite in the cobalt electrowinning chlorine absorption process of a chlorination system, thereby solving the problem of large alkaline wastewater production and increased environmental risks during the cobalt electrowinning chlorine absorption process of a chlorination system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for increasing the available chlorine content of sodium hypochlorite in a cobalt electrowinning chlorine absorption process of a chlorination system, characterized by comprising the following steps: Step 1: Pass circulating water into the liquid inlet of the primary absorption tower, and pass the chlorine gas generated by the electrowinning of the chlorination system into the gas inlet of the primary absorption tower. The circulating water cools the chlorine gas while absorbing it. Step 2: The chlorine gas absorbed in Step 1 is discharged from the gas outlet of the primary absorption tower, and the chlorine water produced during absorption is discharged from the liquid outlet of the primary absorption tower. Step 3: The chlorine gas discharged in Step 2 is sequentially fed into the secondary absorption tower, tertiary absorption tower, quaternary absorption tower and quinary absorption tower for alkali absorption in stages. The temperature during absorption is controlled at 35-40℃ by a cooling plate heat exchanger. Step 4: Introduce absorbent into the inlet of the five-stage absorption tower. The volume ratio of absorbent to water and alkali is 1-3:1. The absorbent flows sequentially through the five-stage absorption tower, the four-stage absorption tower, the three-stage absorption tower, and the two-stage absorption tower. Step 5: The chlorine gas absorbed in Step 3 is discharged from the outlet of the five-stage absorption tower, and the sodium hypochlorite solution produced is discharged from the sodium hypochlorite outlet of the second-stage absorption tower. The external discharge potential of the sodium hypochlorite solution is controlled at 450-500mV. Step Six: The chlorine gas discharged in Step Five is introduced into the sixth-stage absorption tower. Circulating water is introduced into the inlet of the sixth-stage absorption tower to absorb trace amounts of chlorine gas. The resulting chlorine water is discharged from the sixth-stage absorption tower from the outlet. After passing the test and analysis, the chlorine gas is discharged from the purified tail gas outlet of the sixth-stage absorption tower.

[0006] More preferably, the temperature of the circulating water introduced in steps one and six is ​​25-30°C.

[0007] More preferably, the flow rate of the absorbent in step three is 1-2 m³ / h. 3 / h.

[0008] More preferably, the alkali in step four is NaOH.

[0009] Compared with the prior art, the present invention has the following advantages: 1. The present invention relates to controlling the ratio of water to alkali, controlling the discharge potential of the alkali circulating liquid in the chlorine absorption tower, and controlling the temperature of the alkali circulating liquid in the chlorine absorption tower during the preparation of the alkali absorption liquid in the chlorine absorption tower, thereby increasing the effective chlorine content of sodium hypochlorite and reducing the discharged chlorine content. The primary absorption tower pre-treats chlorine gas using circulating water, cooling it to prepare for subsequent alkali absorption. Absorbing a small amount of chlorine prevents high-concentration chlorine from directly impacting the main alkali section, which could lead to excessively rapid consumption of alkali solution and chlorine escape. The secondary to quinary absorption towers perform alkali absorption, using cooling plate heat exchangers to control the temperature and achieve stable absorption. This allows chlorine and alkali solution to react under optimal conditions, directionally generating a sodium hypochlorite solution with high available chlorine and low byproducts. The sixth absorption tower recirculates circulating water to further absorb any remaining trace amounts of chlorine not fully absorbed in the main alkali section. This effectively increases the available chlorine content of the sodium hypochlorite solution after chlorine absorption, thereby reducing the amount of alkaline wastewater discharged and mitigating environmental risks.

[0010] 2. The invention provides a method for increasing the effective chlorine content of sodium hypochlorite in the electrowinning cobalt chlorine absorption process of a chlorination system. The process is simple, and compared with single-stage absorption, multi-stage countercurrent absorption has high chlorine absorption efficiency. It mainly uses alkali absorption, which is more efficient, and the resulting sodium hypochlorite solution can be exported. Attached Figure Description

[0011] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0013] Example Step 1: Circulating water at 27±0.5℃ is introduced into the liquid inlet of the primary absorption tower, and chlorine gas generated by the electrowinning of the chlorination system is introduced into the gas inlet of the primary absorption tower. The circulating water cools the chlorine gas while absorbing it. Step 2: The chlorine gas absorbed in Step 1 is discharged from the gas outlet of the primary absorption tower, and the chlorine water produced during absorption is discharged from the liquid outlet of the primary absorption tower. Step 3: The chlorine gas discharged in Step 2 is sequentially fed into the secondary absorption tower, tertiary absorption tower, quaternary absorption tower and quinary absorption tower for alkali absorption in stages. The temperature during absorption is controlled at 35±0.5℃ by a cooling plate heat exchanger. Step 4: Introduce absorbent into the inlet of the five-stage absorption tower at a flow rate of 1.5 m³ / s. 3 / h, the absorbent uses NaOH solution, with a water to NaOH volume ratio of 2:1, and the absorbent flows sequentially through the five-stage absorption tower, the four-stage absorption tower, the three-stage absorption tower and the two-stage absorption tower; Step 5: The chlorine gas absorbed in Step 3 is discharged from the outlet of the five-stage absorption tower, and the sodium hypochlorite solution produced is discharged from the sodium hypochlorite outlet of the second-stage absorption tower. The external discharge potential of the sodium hypochlorite solution is controlled at 480mV. Step Six: The chlorine gas discharged in Step Four is introduced into the sixth-stage absorption tower. Circulating water is introduced into the inlet of the sixth-stage absorption tower to absorb trace amounts of chlorine gas. The temperature of the circulating water is 30±0.5℃. The chlorine water produced is discharged from the outlet of the sixth-stage absorption tower.

[0014] Analysis showed that the chlorine concentration discharged from the exhaust gas outlet of the six-stage absorption tower met the environmental protection standard of 25 mg / (N·m³). 3 The sodium hypochlorite solution discharged from the sodium hypochlorite outlet of the secondary absorption tower has an effective chlorine content of 10%.

[0015] Compared to single-stage absorption, multi-stage countercurrent absorption offers higher chlorine absorption efficiency, primarily utilizing alkali absorption for greater efficiency, and the resulting sodium hypochlorite solution can be sold externally. The first-stage absorption tower pre-treats the chlorine gas with circulating water, cooling it to prepare for subsequent alkali absorption. Absorbing a small amount of chlorine prevents high-concentration chlorine from directly impacting the main alkali section, which could lead to excessively rapid consumption of alkali solution and chlorine escape. The second to fifth-stage absorption towers perform alkali absorption, using cooling plate heat exchangers to control the temperature and achieve stable absorption. This allows chlorine and alkali solution to react under optimal conditions, directionally generating a sodium hypochlorite solution with high available chlorine and low byproducts. The sixth-stage absorption tower again circulates circulating water to further absorb any remaining trace amounts of chlorine not fully absorbed in the main alkali section.

[0016] The effluent potential of sodium hypochlorite solution is monitored using a Mettler Toledo InProG400, which displays pH / mV in real time. It is compatible with the EasyClean150 flushing system, enabling online pipeline monitoring and automatic cleaning. Under alkaline conditions, chlorine absorption primarily produces sodium hypochlorite; the stronger the alkalinity, the lower the potential. Under acidic conditions, the proportion of hypochlorous acid increases, and the stronger the acidity, the higher the potential. The potential indirectly reflects the solution pH, allowing for assessment of absorbent sufficiency and the need to increase the absorbent flow rate. Controlling the alkaline flow rate controls the potential. If the potential is too low, the solution pH is high; reducing the alkaline flow rate increases the potential. Conversely, if the potential is high, the solution pH is low; increasing the alkaline flow rate decreases the potential, thus maintaining the effluent potential of the sodium hypochlorite solution between 450-500 mV.

[0017] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for increasing the available chlorine content of sodium hypochlorite in the cobalt-chlorine absorption process of a chlorination system, characterized in that... Includes the following steps: Step 1: Pass circulating water into the liquid inlet of the primary absorption tower, and pass the chlorine gas generated by the electrowinning of the chlorination system into the gas inlet of the primary absorption tower. The circulating water cools the chlorine gas while absorbing it. Step 2: The chlorine gas absorbed in Step 1 is discharged from the gas outlet of the primary absorption tower, and the chlorine water produced during absorption is discharged from the liquid outlet of the primary absorption tower. Step 3: The chlorine gas discharged in Step 2 is sequentially fed into the secondary absorption tower, tertiary absorption tower, quaternary absorption tower and quinary absorption tower for alkali absorption in stages. The temperature during absorption is controlled at 35-40℃ by a cooling plate heat exchanger. Step 4: Introduce absorbent into the inlet of the five-stage absorption tower. The volume ratio of absorbent to water and alkali is 1-3:

1. The absorbent flows sequentially through the five-stage absorption tower, the four-stage absorption tower, the three-stage absorption tower, and the two-stage absorption tower. Step 5: The chlorine gas absorbed in Step 3 is discharged from the outlet of the five-stage absorption tower, and the sodium hypochlorite solution produced is discharged from the sodium hypochlorite outlet of the second-stage absorption tower. The external discharge potential of the sodium hypochlorite solution is controlled at 450-500mV. Step Six: The chlorine gas discharged in Step Five is introduced into the sixth-stage absorption tower. Circulating water is introduced into the inlet of the sixth-stage absorption tower to absorb trace amounts of chlorine gas. The resulting chlorine water is discharged from the sixth-stage absorption tower from the outlet. After passing the test and analysis, the chlorine gas is discharged from the purified tail gas outlet of the sixth-stage absorption tower.

2. The method for increasing the available chlorine content of sodium hypochlorite in the cobalt-chlorine absorption process of a chlorination system according to claim 1, characterized in that: The temperature of the circulating water introduced in steps one and six is ​​25-30℃.

3. The method for increasing the available chlorine content of sodium hypochlorite in the cobalt-chlorine absorption process of a chlorination system according to claim 1, characterized in that: The flow rate of the absorbent in step three is 1-2 m³ / h. 3 / h.

4. The method for increasing the available chlorine content of sodium hypochlorite in the cobalt-chlorine absorption process of a chlorination system according to claim 1, characterized in that: The alkali used in step four is NaOH.

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