A method for reusing lithium-extracted wastewater in a waste lithium battery recycling process

Abstract

The invention relates to a method for reusing lithium-extracting wastewater in a waste lithium battery recycling process, comprising the following steps: step 1: collecting and storing the lithium-extracting wastewater; step 2: removing impurities from the wastewater through a filter; step 3: the filtered wastewater passes through a flow meter and enters a P507 extraction system; step 4: the lithium-extracting wastewater and a P507 extractant are saponified in a mixing chamber according to a certain ratio, Na2CO3 is added, and the following reaction occurs: 2R-H+Na2CO3=2R-Na+H2O+CO2↑, R-H is the P507 extractant, and the mixing time is greater than 3.5 minutes; step 5: CO2 generated in the saponification process is collected through a gas collecting device and used in a hydrogenation process for refining lithium carbonate: Li2CO3+CO2+H2O=2LiHCO3; step 6: after the lithium-extracting wastewater is saponified, it enters an oil removal and weight removal process with a P507 raffinate. The present invention uses the lithium extraction wastewater to replace liquid alkali after filtering and removing impurities, and reuses it to the P507 extraction line for saponification, thereby reducing the amount of liquid alkali used and reducing the amount of wastewater discharged, thereby achieving the purpose of energy conservation and emission reduction and turning waste into treasure.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling and treating scrapped lithium batteries, and in particular relates to a method for reusing lithium-extracted wastewater in a recycling and treating process of scrapped lithium batteries. Background Art

[0002] The lithium battery industry is an important component of the development of new energy storage devices and new energy vehicles. Directed recycling of waste batteries into battery raw materials can not only solve the environmental pollution caused by the scrapping of batteries during production and use, but also reduce resource consumption and environmental problems caused by mining raw ores.

[0003] With the sharp increase in sales of electric vehicles, the scale of the power battery recycling market continues to expand. It is predicted that by 2025, the annual scrap volume of power batteries may reach 350,000 tons. Recycling them as resources can not only solve the environmental problems caused by waste lithium-ion batteries, but also alleviate the shortage of strategic metal resources in my country and promote the sustainable development of my country's battery industry.

[0004] In the process of recycling waste lithium-ion batteries, the wastewater produced has a complex composition and is characterized by high sodium salt concentration and large total amount, resulting in high energy consumption, high cost, and complex treatment process for wastewater treatment. Currently, the wastewater from lithium extraction is acidified to remove carbonate (excess soda is neutralized into Na2SO4 and CO2), and the neutralized liquid enters the MVR system to evaporate and crystallize the Na2SO4 in the wastewater. The evaporated and concentrated MVR concentrate is deoiled and then returned to the lithium extraction process. This process is long, has high carbon emissions, high soda consumption, high energy consumption, and large equipment investment.

[0005] Therefore, it is necessary to provide a simple, energy-saving and safe method for recycling lithium extraction wastewater. Summary of the invention

[0006] The purpose of the present invention is to provide a method for recycling lithium extraction wastewater in the recycling process of scrapped lithium batteries, aiming to reuse the lithium extraction alkaline wastewater (Na2CO3) as a resource and use it in the extraction system instead of liquid alkali saponification, thereby reducing the amount of wastewater discharged and reducing the amount of liquid alkali used and acid consumption.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] A method for recycling lithium-extracting wastewater in a waste lithium battery recycling process comprises the following steps:

[0009] Step 1: Collect and store lithium extraction wastewater;

[0010] Step 2: Pass the wastewater through a filter to remove debris;

[0011] Step 3: The filtered wastewater passes through the flow meter and enters the P507 extraction system;

[0012] Step 4: The lithium extraction wastewater and the P507 extractant are saponified in a mixing chamber according to a certain ratio, Na2CO3 is added, and the following reaction occurs: 2R-H+Na2CO3=2R-Na+H2O+CO2↑, RH is the P507 extractant, and the mixing time is >3.5min;

[0013] Step 5: The CO2 produced during the saponification process is collected by a gas collection device and used in the hydrogenation process of refining lithium carbonate: Li2CO3+CO2+H2O=2LiHCO3;

[0014] Step 6: After saponification, the lithium extraction wastewater enters the oil and weight removal process along with the P507 raffinate.

[0015] Preferably, in step 1, the lithium extraction wastewater is placed in a storage tank and a pipeline, and the storage tank and the pipeline are equipped with insulation or heating equipment, and the temperature is controlled at >30°C.

[0016] Preferably, in step 2, the filter is a bag filter or a precision filter.

[0017] Preferably, in step 3, the ratio of lithium extraction wastewater to P507 extractant is adjusted to 1:(3-5) by adjusting the flow meter.

[0018] Preferably, in step 4, the saponification process releases heat, and a heat exchanger or a forced cooling device is added to the saponification stage.

[0019] In step 4, during the lithium extraction operation, an excess of Na2CO3 needs to be added to ensure the recovery rate of Li. The sodium ion content in the lithium extraction wastewater is 140g / L-160g / L and the pH is greater than 11. The existing process is to acidify the wastewater and then evaporate and crystallize Na2SO4 through the MVR system. The present invention utilizes the high pH and sodium ion characteristics of the lithium extraction wastewater to replace liquid alkali for saponification of the P507 extraction line, which can reduce the amount of wastewater discharged and the amount of liquid alkali used, and can also save the consumption of acid in the acidification process, thereby achieving the purpose of reducing emissions and reducing consumption.

[0020] Beneficial effects:

[0021] The lithium extraction wastewater generated in the waste lithium battery recycling process of the present invention does not need to be subjected to complicated treatment. It can be directly used on the P507 extraction line after heating and filtering. The high content of COD, sodium ions, carbonate ions and the like in the wastewater will not have a negative impact on the system. The COD source is the P507 extractant entrained in the raffinate, which is recycled to the P507 extraction system without causing pollution to the extraction system. The sodium ions are exchanged with H+ in the extractant when entering the P507 extraction system for saponification. After the carbonate ions enter, they are decomposed into CO2 during saponification and enter the collection device along with the negative pressure system for refining lithium carbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flow chart of a method for reusing lithium-extracted wastewater in a scrap lithium battery recycling process. DETAILED DESCRIPTION

[0023] Embodiment 1:

[0024] Reference Figure 1 The lithium extraction wastewater generated in the waste lithium battery recycling process is controlled at a temperature between 30-60°C and passed through a bag filter to remove suspended impurities in the wastewater.

[0025] The wastewater filtered in the above steps is added to the extraction tank through a flow meter and saponified with P507 extractant. Na2CO3 is added. CO2 gas will be released during the saponification process. The flow meter controls the flow ratio to remain at 1:5.

[0026] The saponified P507 extractant in the above step enters the extraction stage and contacts with the pre-extraction liquid. The organic full load of Ni is 10.21 g / L. The wastewater after saponification is discharged together with the raffinate.

[0027] The raffinate and saponified liquid produced in the above steps enter the lithium extraction process after oil and weight removal. The wastewater after lithium extraction contains 70-80g / L Na2CO3 and pH>11, which is collected and recycled.

[0028] Embodiment 2:

[0029] The lithium extraction wastewater generated in the waste lithium battery recycling process is controlled at a temperature between 30-60°C and passed through a bag filter to remove suspended impurities in the wastewater.

[0030] The filtered wastewater in the above step is added to the extraction tank through a flow meter and saponified with P507 extractant. CO2 gas will be released during the saponification process, and the flow meter controls the flow ratio to remain at 1:3.

[0031] After saponification in the above step, the P507 extractant enters the extraction stage and contacts with the pre-extraction liquid. The organic full load of Ni is 13.79 g / L. The wastewater after saponification is discharged together with the raffinate.

[0032] The raffinate and saponified liquid produced in the above steps enter the lithium extraction process after oil and weight removal. The wastewater after lithium extraction contains 70-80g / L Na2CO3 and pH>11, which is collected and recycled.

[0033] Embodiment 3:

[0034] The temperature of lithium extraction wastewater generated in the waste lithium battery recycling process is controlled between 30-60°C and passed through a precision filter to remove suspended impurities in the wastewater.

[0035] The filtered wastewater from the above step is added into the extraction tank through a flow meter and saponified with P507 extractant. CO2 gas will be released during the saponification process. The flow meter controls the flow ratio to remain at 1:3. The generated CO2 is collected through a gas collection device and used in the hydrogenation process of refining lithium carbonate: Li2CO3+CO2+H2O=2LiHCO3. Heat is generated during the saponification process and a heat exchanger is used for heat exchange.

[0036] After saponification in the above step, the P507 extractant enters the extraction stage and contacts with the pre-extraction liquid. The organic full load of Ni is 13.79 g / L. The wastewater after saponification is discharged together with the raffinate.

[0037] The raffinate and saponified liquid produced in the above steps enter the lithium extraction process after deoiling and weighing. The wastewater after lithium extraction contains 70-80g / L Na2CO3 and pH>11, which is collected and recycled.

[0038] Embodiment 1-3, after verification, based on 100m3 of lithium extraction wastewater per day, can replace 18 tons of liquid caustic soda, reduce acid consumption by 7 tons, reduce water discharge by 13 tons, according to 700 yuan per ton of liquid caustic soda, 200 yuan per ton of acid, 72.5 yuan per ton of water treatment fee, daily economic benefit is 14,900 yuan, annual economic benefit is 4.9 million yuan (330 working days / year). The present invention uses lithium extraction wastewater to replace liquid caustic soda after filtering and impurity removal, and reuses it to the P507 extraction line for saponification, thereby reducing the amount of liquid caustic soda used and reducing the amount of wastewater discharged, that is, achieving the purpose of energy saving and emission reduction, and turning waste into treasure.

Claims

1. A method for recycling lithium-extracting wastewater in a waste lithium battery recycling process, characterized in that: The steps include: Step 1: Collect and store lithium extraction wastewater; Step 2: Pass the wastewater through a filter to remove debris; Step 3: The filtered wastewater passes through the flow meter and enters the P507 extraction system; Step 4: The lithium extraction wastewater and the P507 extractant are saponified in a mixing chamber according to a certain ratio, Na2CO3 is added, and the following reaction occurs: 2R-H+Na2CO3=2R-Na+H2O+CO2↑, RH is the P507 extractant, and the mixing time is >3.5min; Step 5: The CO2 produced during the saponification process is collected by a gas collection device and used in the hydrogenation process of refining lithium carbonate: Li2CO3+CO2+H2O=2LiHCO3; Step 6: After the lithium extraction wastewater is saponified, it enters the oil removal and weight removal process along with the P507 raffinate; In step 1, the lithium extraction wastewater is placed in a storage tank and a pipeline, and heat preservation or heating equipment is added to control the temperature at >30°C; In step 3, the ratio of lithium extraction wastewater to P507 extractant is adjusted to 1:(3-5) by adjusting the flow meter; In step 4, the saponification process releases heat, and a heat exchanger or a forced cooling device is added to the saponification section.

2. The method for recycling lithium-extracting wastewater in the scrap lithium battery recycling process according to claim 1, characterized in that: In step 2, the filter is a bag filter or a precision filter.

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