Charged battery environment-friendly discharging method

Abstract

The invention relates to an environment-friendly discharging method for a charged battery, which belongs to the technical field of waste battery recovery, and comprises four steps of battery discharging, air shower drying, waste gas treatment system and wastewater treatment system. In the battery discharging stage, the waste lithium battery is soaked in the salt solution for discharging, the pH value of the salt solution is controlled through a pH online monitor, and waste gas enters a waste gas treatment system through a collection cover; in the air shower drying stage, an air shower chamber and a drying chamber are adopted for conducting primary air drying and low-temperature drying on the batteries correspondingly, and waste gas enters the waste gas treatment system as well; the waste gas treatment system comprises bag type dust removal, spray tower purification and activated carbon adsorption; and the wastewater treatment system reacts the collected acidic wastewater with calcium hydroxide to generate calcium fluoride, clear water is recycled after filter pressing, and sludge is transported outwards. Whole-process environment-friendly treatment of waste gas and waste water in the battery discharging process is achieved, the problem that an existing chemical discharging process is serious in environmental pollution is solved, and the method is suitable for environment-friendly discharging treatment of large-scale waste lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of waste battery recycling technology, and in particular to a method for environmentally friendly discharge of charged batteries. Background Technology

[0002] With the rapid popularization of new energy vehicles, the installed capacity of power lithium batteries is also increasing. When lithium batteries reach the end of their service life, they must be retired. For retired lithium batteries that can no longer be reused, the valuable metals in the battery are generally recycled by crushing. If the battery still contains a certain amount of charge, crushing it will pose a risk of explosion and damage the crusher. Therefore, when crushing and recycling batteries, it is generally necessary to discharge the battery first and then crush it to a certain voltage.

[0003] Battery discharge is mainly divided into physical discharge and chemical discharge. Physical discharge uses a discharge machine, which has high investment costs, involves load discharge, is uncontrollable, poses safety risks, and cannot be scaled up for mass production. Chemical discharge generally uses a salt solution, which is suitable for discharging large quantities of batteries. In the prior art, CN116247322A discloses a method for discharging waste lithium-ion batteries, which involves discharging the waste batteries with an aqueous solution and then using the residual heat of the battery discharge to dry the batteries. However, when lithium batteries are discharged with an aqueous solution, the electrolyte in the battery will be released from the battery. The solvent in the electrolyte is an ester, which will produce organic pollutants after volatilization. At the same time, the electrolyte lithium hexafluorophosphate in the electrolyte will produce hydrofluoric acid when it comes into contact with water, and the aqueous solution after discharge is also polluted water.

[0004] Therefore, an environmentally friendly discharge method is needed to discharge lithium batteries. Summary of the Invention

[0005] In response to the shortcomings of the existing production technologies, the applicant provides a method for environmentally friendly discharge of charged batteries, thereby achieving the complete collection and treatment of waste gas and wastewater during the discharge process, ensuring that the discharge process is safe, environmentally friendly, and controllable.

[0006] The technical solution adopted in this invention is as follows: A method for environmentally friendly discharge of a charged battery includes the following operational steps: Step 1: Discharge the battery. Immerse the waste lithium battery in a battery discharge solution containing salt solution, monitor and adjust the pH value of the salt solution, and collect the waste gas generated during the discharge process. Step 2: Air shower drying. The discharged batteries are first sent to the air shower room for preliminary air drying, and then sent to the drying room for low-temperature drying. The exhaust gas generated during the air shower and drying process is collected. Step 3: Waste gas treatment. The collected waste gas is treated sequentially through a bag filter, a spray tower, and an activated carbon adsorption device before being discharged. Step 4: Wastewater treatment. The acidic wastewater generated during the discharge and air shower processes is collected in the waste liquid collection pit. After reacting with calcium hydroxide and pressure filtration, the clean water is reused in the salt solution storage tank, and the sludge is transported off-site.

[0007] Its further technical solution lies in: In step one, the salt solution is a sodium chloride solution with a mass concentration of 5% to 20%.

[0008] In step one, when the pH value of the salt solution in the battery is lower than 5.5, some of the acidic solution is drained and new salt solution is added to restore the pH value to above 7.0.

[0009] In step two, the air-drying time in the air shower room is 15 to 25 minutes; In step three, the drying temperature in the drying chamber is 90℃~110℃, and the drying time is 30min~60min.

[0010] In step three, the spray tower uses a sodium hydroxide solution with a mass concentration of 3% to 6% for spraying.

[0011] In step three, the activated carbon used in the activated carbon adsorption device is wood-based activated carbon or fruit shell activated carbon, which is cylindrical or round in shape and has a diameter of 1.5 mm to 4 mm.

[0012] In step four, the mass concentration of the calcium hydroxide solution is 2% to 4%, and the reaction tank is equipped with a stirring device with a stirring speed of 10 r / min to 15 r / min.

[0013] In step four, the wastewater reacts with calcium hydroxide to produce calcium fluoride flocculants. After being filtered by a filter press, the clear water is returned to the brine storage tank, while the calcium fluoride sludge is transported off-site for treatment.

[0014] The beneficial effects of this invention are as follows: This invention achieves full-process environmental protection control of the discharge process: By setting up exhaust gas collection hoods, pipeline systems, and wastewater collection pits, all exhaust gases and wastewater generated in the discharge, air shower, and drying processes are collected and centrally treated, fundamentally solving the problem of unorganized pollutant emissions in traditional open chemical discharge processes and achieving clean and closed treatment of the discharge process.

[0015] This invention constructs a highly efficient waste gas co-treatment system: The waste gas treatment system innovatively combines a three-stage purification process: baghouse dust collection, alkaline spraying, and activated carbon adsorption. Baghouse dust collection effectively removes fine dust that may be generated during the discharge process; the spray tower utilizes sodium hydroxide solution to efficiently neutralize acidic gases in the waste gas (such as hydrofluoric acid and acidic components produced by the hydrolysis of volatile esters); and the activated carbon adsorption unit, as a deep treatment unit, effectively adsorbs residual trace organic pollutants. This combined process is highly targeted and efficient, ensuring that the emitted gas consistently meets emission standards.

[0016] This invention innovates a closed-loop wastewater treatment and resource reuse model: The wastewater treatment system introduces calcium hydroxide to react with fluoride ions in the wastewater, generating calcium fluoride precipitate. This not only efficiently removes highly toxic fluorides but also achieves the resource-based fixation of fluoride. After pressure filtration, the supernatant (mainly composed of sodium chloride) can be recycled back to the brine storage tank for use in preparing the discharge fluid, realizing the recycling of the discharge medium (salt solution). This significantly reduces the consumption of fresh water and salt, lowers operating costs, and eliminates the direct discharge of high-salt, high-fluoride wastewater.

[0017] This invention improves the intelligence and stability of the discharge process: By installing an online pH monitor on the side wall of the discharge battery and linking it with the drain valve and the injection valve, the system achieves automatic monitoring and adjustment of the discharge fluid's acidity and alkalinity. This system can promptly drain excessively acidic solutions and replenish the fluid with fresh liquid, always maintaining the discharge fluid within a suitable pH range (above 7.0). This not only ensures stable discharge efficiency but also effectively suppresses corrosion and harmful gas release problems that may be exacerbated by strong acid environments, improving the overall system's operational reliability and safety.

[0018] This invention optimizes the battery post-processing procedure and improves overall efficiency: The air shower chamber and the low-temperature drying chamber are organically combined. The air shower process can quickly remove a large number of residual liquid droplets on the battery surface, reducing the drying load in the subsequent process; the low-temperature drying (90℃~110℃) thoroughly removes moisture while avoiding the risk of violent reactions of residual electrolyte inside the battery or damage to the battery structure that may be caused by high temperatures. This process design shortens the processing time, reduces energy consumption, and ensures the safety of the subsequent battery crushing process.

[0019] This invention has good economic benefits and prospects for large-scale application: While addressing core environmental issues, the system utilizes mature and universally applicable equipment (such as spray towers, activated carbon adsorption devices, and filter presses), ensuring controllable investment costs. The entire system boasts a high degree of automation, making it suitable for large-scale, continuous waste battery discharge processing, providing a practical industrial solution for the large-scale environmental recycling of retired lithium batteries.

[0020] In summary, this invention not only effectively overcomes the technical challenge of environmental pollution in the chemical discharge process, but also achieves a balance of environmental protection, safety, economy, and efficiency through systematic process design, demonstrating significant technological advancement and broad industrial application value.

[0021] This invention can collect and treat the waste gas and wastewater generated during the salt water discharge process to meet emission standards, making the entire battery discharge process environmentally friendly and pollution-free. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0023] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0024] Example 1: like Figure 1 As shown, the method for environmentally friendly discharge of a charged battery in this embodiment includes the following operation process: Step 1: Discharge the battery. Immerse the waste lithium battery in a battery discharge solution containing salt solution, monitor and adjust the pH value of the salt solution, and collect the waste gas generated during the discharge process. Step 2: Air shower drying. The discharged batteries are first sent to the air shower room for preliminary air drying, and then sent to the drying room for low-temperature drying. The exhaust gas generated during the air shower and drying process is collected. Step 3: Waste gas treatment. The collected waste gas is treated sequentially through a bag filter, a spray tower, and an activated carbon adsorption device before being discharged. Step 4: Wastewater treatment. The acidic wastewater generated during the discharge and air shower processes is collected in the waste liquid collection pit. After reacting with calcium hydroxide and pressure filtration, the clean water is reused in the salt solution storage tank, and the sludge is transported off-site.

[0025] In step one, the salt solution is a sodium chloride solution with a mass concentration of 5% to 20%.

[0026] In step one, when the pH value of the salt solution in the battery is lower than 5.5, some of the acidic solution is drained and new salt solution is added to restore the pH value to above 7.0.

[0027] In step two, the air-drying time in the air shower room is 15 to 25 minutes; In step three, the drying temperature in the drying chamber is 90℃~110℃, and the drying time is 30min~60min.

[0028] In step three, the spray tower uses a sodium hydroxide solution with a mass concentration of 3% to 6% for spraying.

[0029] In step three, the activated carbon used in the activated carbon adsorption device is wood-based activated carbon or fruit shell activated carbon, which is cylindrical or round in shape and has a diameter of 1.5 mm to 4 mm.

[0030] In step four, the mass concentration of the calcium hydroxide solution is 2% to 4%, and the reaction tank is equipped with a stirring device with a stirring speed of 10 r / min to 15 r / min.

[0031] In step four, the wastewater reacts with calcium hydroxide to produce calcium fluoride flocculants. After being filtered by a filter press, the clear water is returned to the brine storage tank, while the calcium fluoride sludge is transported off-site for treatment.

[0032] Example 2: Step 1, Battery Discharge: First, neatly arrange the waste lithium batteries on a plastic pallet frame. A crane will then lower the waste lithium batteries from the pallet frame into the discharge tank. The solution inside the discharge tank is a salt solution, specifically a sodium chloride solution with a mass concentration of 5% to 20%. The waste lithium batteries will continue to discharge while immersed in the discharge tank until the internal voltage drops below 1.5V. The discharge time in the discharge tank is 24 to 72 hours. Because lithium hexafluorophosphate in the electrolyte of the waste lithium batteries reacts with water to produce hydrofluoric acid (HF), the pH value of the discharge salt solution gradually decreases. An online pH monitor is installed on the side wall of the discharge tank. When the pH value displayed by the monitor is below 5.5, the drain valve of the discharge tank will be activated to discharge the acidic salt solution into the waste liquid collection pit. Simultaneously, new salt solution will be injected into the discharge tank until the pH value displayed by the pH monitor is above 7.0. At this point, the injection of new salt solution will stop, and the drain valve will be closed. An exhaust gas collection hood is installed above the battery. The exhaust gas generated by the discharge of waste lithium battery salt solution is collected through pipelines and then enters the exhaust gas treatment system.

[0033] II. Air Shower Drying: After the waste lithium batteries have finished discharging in water, they are removed from the discharge chamber by a crane and placed in the air shower chamber. Since acidic salt solutions remain after the waste lithium batteries are removed, a residual liquid collection tank is provided at the bottom of the air shower chamber, and the collected liquid is discharged into a waste liquid collection pit. Blowers are installed on the side walls of the air shower chamber, which blow air into the air shower chamber to promote air circulation, thereby using airflow to remove moisture from the surface of the waste lithium batteries, achieving a preliminary drying effect. The exhaust gas generated in the air shower chamber is collected through pipes and enters the exhaust gas treatment system. The air drying time in the air shower chamber is 15 min to 25 min. After being air-dried, the waste lithium batteries are sent into the drying chamber, where circulating hot air is used to dry them at a low temperature. The dried waste lithium batteries are then packaged for further processing. The hot air exhaust gas is collected through pipes and enters the exhaust gas treatment system. The hot air drying temperature in the drying chamber is 90℃~110℃, and the drying time is 30min~60min.

[0034] III. Exhaust Gas Treatment System: The exhaust gas collected through the discharge battery, air shower, and drying chamber pipes first enters a bag filter to remove fine dust, then enters a spray tower to remove acidic gases. The exhaust gas exiting the spray tower enters an activated carbon adsorption device for further purification, and is then discharged through an induced draft fan and chimney. The spray tower uses an alkaline solution, specifically sodium hydroxide solution, with a mass concentration of 3%~6%. The neutralized wastewater at the bottom of the spray tower enters a waste liquid collection pit. The activated carbon in the activated carbon adsorption device uses either wood-based activated carbon or fruit shell activated carbon, in cylindrical or circular shapes, with a diameter ranging from 1.5mm to 4mm.

[0035] IV. Wastewater Treatment System: Wastewater from the waste liquid collection pit is pumped into the reaction tank. Calcium hydroxide solution is added to the reaction tank. The calcium hydroxide reacts with sodium fluoride in the wastewater to produce calcium fluoride flocculants. The wastewater after the reaction enters a filter press for filtration. The filtered water is returned to the brine storage tank and re-injected into the battery for discharging waste lithium batteries. The calcium fluoride sludge produced by filtration is collected and transported off-site for treatment. The mass concentration of the calcium hydroxide solution added to the reaction tank is 2%~4%. The reaction tank is equipped with a stirring device with a stirring speed of 10r / min~15r / min.

[0036] Using this method to treat the two types of retired lithium batteries mentioned above, no irritating odors or wastewater leaks occurred throughout the entire process. The treated waste gas and wastewater consistently met environmental emission or reuse standards. The discharged batteries maintained their structural integrity, showing no leakage or bulging, thus meeting the requirements for subsequent safe crushing. This method successfully achieved large-scale, continuous, and environmentally friendly discharge treatment of charged batteries.

[0037] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A method for environmentally friendly discharge of a charged battery, characterized in that: The following operational procedures are included: Step 1: Discharge the battery. Immerse the waste lithium battery in a battery discharge solution containing salt solution, monitor and adjust the pH value of the salt solution, and collect the waste gas generated during the discharge process. Step 2: Air shower drying. The discharged batteries are first sent to the air shower room for preliminary air drying, and then sent to the drying room for low-temperature drying. The exhaust gas generated during the air shower and drying process is collected. Step 3: Waste gas treatment. The collected waste gas is treated sequentially through a bag filter, a spray tower, and an activated carbon adsorption device before being discharged. Step 4: Wastewater treatment. The acidic wastewater generated during the discharge and air shower processes is collected in the waste liquid collection pit. After reacting with calcium hydroxide and pressure filtration, the clean water is reused in the salt solution storage tank, and the sludge is transported off-site.

2. The method for environmentally friendly discharge of a charged battery as described in claim 1, characterized in that: In step one, the salt solution is a sodium chloride solution with a mass concentration of 5% to 20%.

3. The method for environmentally friendly discharge of a charged battery as described in claim 1, characterized in that: In step one, when the pH value of the salt solution in the battery is lower than 5.5, some of the acidic solution is drained and new salt solution is added to restore the pH value to above 7.

0.

4. The method for environmentally friendly discharge of a charged battery as described in claim 1, characterized in that: In step two, the air-drying time in the air shower room is 15 to 25 minutes.

5. The method for environmentally friendly discharge of a charged battery as described in claim 1, characterized in that: In step three, the drying temperature in the drying chamber is 90℃~110℃, and the drying time is 30min~60min.

6. The method for environmentally friendly discharge of a charged battery as described in claim 1, characterized in that: In step three, the spray tower uses a sodium hydroxide solution with a mass concentration of 3% to 6% for spraying.

7. The method for environmentally friendly discharge of a charged battery as described in claim 1, characterized in that: In step three, the activated carbon used in the activated carbon adsorption device is wood-based activated carbon or fruit shell activated carbon, which is cylindrical or round in shape and has a diameter of 1.5 mm to 4 mm.

8. The method for environmentally friendly discharge of a charged battery as described in claim 1, characterized in that: In step four, the mass concentration of the calcium hydroxide solution is 2% to 4%, and the reaction tank is equipped with a stirring device with a stirring speed of 10 r / min to 15 r / min.

9. A method for environmentally friendly discharge of a charged battery as described in claim 1, characterized in that: In step four, the wastewater reacts with calcium hydroxide to produce calcium fluoride flocculants. After being filtered by a filter press, the clear water is returned to the brine storage tank, while the calcium fluoride sludge is transported off-site for treatment.

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