A device and method for purifying mixed positive and negative electrode powder of waste lithium iron phosphate battery

Abstract

The present invention discloses a purification device and method for the positive and negative electrode mixed powder of waste lithium iron phosphate batteries, which belongs to the technical field of battery recycling and processing, and includes: step one, dismantling the waste lithium iron phosphate batteries, taking out the positive and negative electrode materials, and crushing them; step two, using screening equipment to screen the crushed materials; step three, putting the obtained positive and negative electrode mixed powder into a reduction furnace for thermal reduction treatment; step four, cooling the reduced powder to room temperature, refining it, and then using a magnetic separator to separate the iron powder with strong magnetism from the non-magnetic powder; step five, using a chemical treatment method to further collect the metal in the non-magnetic powder. The present invention can judge whether the flow rate of the reducing gas is normal in combination with the judgment value generated in a large cycle, and timely adjust the abnormal flow rate, so that the reaction atmosphere in the entire reduction furnace is in the best state, which can further ensure the product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of battery recycling and processing, and specifically relates to a device and a method for purifying mixed positive and negative electrode powder of waste lithium iron phosphate batteries. Background Art

[0002] With the booming development of the global new energy vehicle market, the installed capacity of power batteries has increased rapidly, and the number of scrapped batteries has also gradually increased. Since waste lithium iron phosphate batteries contain a variety of valuable materials such as lithium, cobalt, nickel, manganese, copper, aluminum, etc., direct disposal will cause environmental pollution. Therefore, by purifying the positive and negative mixed powders of waste lithium iron phosphate batteries, these valuable elements can be effectively recovered to alleviate resource tensions.

[0003] Currently, the powder extraction of waste lithium iron phosphate batteries mostly adopts thermal reduction method to decompose organic matter, change material structure and promote the reduction of metal ions. However, in the thermal reduction treatment step, the flow rate of reducing gas is generally set in advance based on experience. During the reduction process, as the reaction proceeds, the reduction furnace will experience some fluctuations, such as temperature changes. If the reducing gas flow rate is always based on the pre-set value, it will affect the quality of the product in the reduction furnace. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for purifying mixed positive and negative electrode powders of waste lithium iron phosphate batteries, so as to solve the problems faced in the above-mentioned background technology.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for purifying mixed positive and negative electrode powder of waste lithium iron phosphate battery, the method comprising: Step 1: dismantle the waste lithium iron phosphate battery, perform a complete discharge process, take out the positive and negative electrode materials, and crush them into multiple granular materials through a crusher; Step 2: Use screening equipment to screen the crushed material to obtain positive and negative electrode mixed powders with relatively uniform sizes; Step 3: placing the obtained positive and negative electrode mixed powder into a reduction furnace for thermal reduction treatment to obtain reduced powder; Step 4: Cool the reduced powder to room temperature, refine it, and then use a magnetic separator to separate the iron powder with strong magnetism from the non-magnetic powder; Step 5: Use chemical treatment to further collect the metals in the non-magnetic powder.

[0006] Furthermore, the thermal reduction treatment method in step three includes: Place the positive and negative electrode mixed powders into the reduction furnace, and set the initial reaction temperature, the flow rate and velocity of the reducing gas; Acquire the reaction temperature in the reduction furnace and the concentration of the reducing gas obtained at the outlet of the reduction furnace, so as to analyze the obtained reaction temperature and reducing gas concentration every small period and generate a judgment value; The flow rate of the introduced reducing gas is analyzed to determine whether it is qualified according to the generated judgment value. If it is unqualified, the flow rate of the introduced reducing gas is adjusted according to the generated first adjustment instruction.

[0007] Furthermore, the method for generating the first adjustment instruction is: According to the obtained reaction temperature and the concentration of reducing gas at the outlet, a curve of reaction temperature variation over time in a small cycle is drawn up. And the reduction gas concentration at the outlet changes with time ; By formula Get the judgment value ; The judgment value obtained The preset judgment threshold interval To compare: when , a first adjustment instruction is generated; in, is the preset standard reaction temperature versus time curve, The standard reducing gas concentration curve preset at the outlet changes with time. is the temperature reference value, is the concentration reference value, as well as is the weight coefficient, is the start time of the small cycle, The end time of the small cycle.

[0008] Furthermore, the method for adjusting the flow rate of the introduced reducing gas according to the first adjustment instruction is: when When , the formula Adjust the flow rate of the reducing gas to ; when When , the formula Adjust the flow rate of the reducing gas to ; in, is the current flow rate of reducing gas, is the maximum reducing gas flow rate allowed to be adjusted, is the conversion coefficient.

[0009] Furthermore, the thermal reduction treatment method in step 3 further comprises: In a large cycle, which includes n small cycles, analysis is performed based on the obtained judgment value to determine whether to generate a second adjustment instruction, thereby adjusting the flow rate of the introduced reducing gas.

[0010] Furthermore, the second adjustment instruction generation method is: Get the big cycle The number of times d, through the formula Get the percentage value , and the obtained percentage value The ratio threshold is set Make a comparison; when When , a second adjustment instruction is generated.

[0011] Further, the second adjustment instruction includes an increase instruction and a decrease instruction; Get the big cycle The number of as well as The number of ; By formula The first judgment coefficient ; when When , a reduction instruction is generated; By formula The second evaluation coefficient ; when When , an increase instruction is generated; in, , is the number of times the judgment value is greater than the average judgment value, is the maximum judgment value within the large cycle, The number of times the judgment value is less than the average judgment value, is the minimum judgment value within the large cycle, as well as is the threshold coefficient, , , , is the proportionality coefficient.

[0012] Furthermore, when a reduction instruction is generated, the formula Reduce the flow rate of reducing gas speed; When an increase instruction is generated, the formula Increase the flow rate of reducing gas speed; in, and is the conversion coefficient.

[0013] A device for purifying mixed positive and negative electrode powder of waste lithium iron phosphate batteries, used to implement the above-mentioned method for purifying mixed positive and negative electrode powder of waste lithium iron phosphate batteries, the purification device includes but is not limited to a crusher, screening equipment, reduction furnace, magnetic separator, etc.

[0014] Beneficial effects of the present invention: During the thermal reduction treatment process, the present invention monitors the reaction temperature changes in the reduction furnace and the reducing gas concentration changes at the reduction furnace outlet in real time, thereby analyzing and generating a judgment value, and judging whether the introduced reducing gas flow is qualified based on the generated judgment value. When it is unqualified, the introduced reducing gas flow is adjusted based on the generated first adjustment instruction. In this way, the amount of the introduced reducing gas can be dynamically adjusted according to the temperature in the reduction furnace and the concentration changes of the reducing gas, thereby ensuring the reaction atmosphere in the reactor, thereby ensuring the quality of the generated product.

[0015] The present invention can determine whether the flow rate of the reducing gas is normal in combination with the judgment value generated in a large cycle, and timely adjust the abnormal flow rate, so that the reaction atmosphere in the entire reduction furnace is in the best state, which can further ensure the product quality.

[0016] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0018] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In one embodiment, a method for purifying mixed positive and negative electrode powders of waste lithium iron phosphate batteries is disclosed, such as Figure 1As shown, the purification method mainly comprises the following steps: Step 1: dismantle the waste lithium iron phosphate battery, perform a complete discharge process, take out the positive and negative electrode materials, and crush them into multiple granular materials through a crusher; Step 2: Use screening equipment to screen the crushed material to obtain positive and negative electrode mixed powders with relatively uniform sizes; Step 3: placing the obtained positive and negative electrode mixed powder into a reduction furnace for thermal reduction treatment to obtain reduced powder; Step 4: Cool the reduced powder to room temperature, refine it, and then use a magnetic separator to separate the iron powder with strong magnetism from the non-magnetic powder; Step 5: Use chemical treatment to further collect the metals in the non-magnetic powder; The method of thermal reduction treatment in step 3 includes: placing the positive and negative electrode mixed powders into a reduction furnace, and setting the initial reaction temperature, the flow rate and flow rate of the reducing gas; Acquire the reaction temperature in the reduction furnace and the concentration of the reducing gas obtained at the outlet of the reduction furnace, so as to analyze the obtained reaction temperature and reducing gas concentration every small period and generate a judgment value; The flow rate of the introduced reducing gas is analyzed to determine whether it is qualified according to the generated judgment value. If it is unqualified, the flow rate of the introduced reducing gas is adjusted according to the generated first adjustment instruction.

[0021] Through the above technical scheme, the present application first disassembles the waste lithium iron phosphate batteries and performs a complete discharge treatment to avoid safety accidents such as short circuit fire in subsequent treatment, and then takes out the positive and negative electrode materials, and crushes them into multiple granular materials through a crusher to convert them into fine particles for subsequent treatment. The crushed materials are then screened using screening equipment to obtain positive and negative electrode mixed powders with relatively uniform sizes, which are then put into a reduction furnace for thermal reduction treatment to obtain reduced powders. During the thermal reduction treatment, the reaction temperature changes in the reduction furnace and the reduction gas concentration changes at the reduction furnace outlet are monitored in real time, so as to analyze and generate a judgment value, and judge whether the reduction gas flow rate introduced is qualified based on the generated judgment value. If it is unqualified, When the reduction furnace is in the state of being heated, the flow rate of the reducing gas introduced is adjusted according to the first adjustment instruction, so that the amount of reducing gas introduced can be dynamically adjusted according to the temperature in the reduction furnace and the concentration change of the reducing gas, so as to ensure that the reducing gas is in the optimal range and the quality of the product in the reduction furnace is more qualified; after the reduction is completed, the reduced powder is cooled to room temperature and further refined, and a magnetic separator is used to separate the iron powder with strong magnetism from the non-magnetic material (such as lithium, aluminum, and copper), and then the metal in the non-magnetic powder is further collected by chemical treatment, such as leaching the non-magnetic material with acid, dissolving the metal ions in the solution, and then converting the specific metal ions into precipitates by adding appropriate precipitants, and then filtering and separating. In this way, the flow rate of the reducing gas introduced can be dynamically adjusted during the thermal reduction process, so as to ensure that the reduction furnace is in the nearest environmental atmosphere to ensure the quality of the generated product.

[0022] As an embodiment of the present invention, the method for generating the first adjustment instruction is: according to the obtained reaction temperature and the concentration of the reducing gas at the outlet, a reaction temperature variation curve over time in a small cycle is drawn up. And the reduction gas concentration at the outlet changes with time ; By formula Get the judgment value ; The judgment value obtained The preset judgment threshold interval To compare: when , a first adjustment instruction is generated; in, is the preset standard reaction temperature versus time curve, The standard reducing gas concentration curve preset at the outlet changes with time. is the temperature reference value, is the concentration reference value, as well as is the weight coefficient, is the start time of the small cycle, The end time of the small cycle; The method for adjusting the flow rate of the reducing gas introduced according to the first adjustment instruction is: When , the formula Adjust the flow rate of the reducing gas to ; when When , the formula Adjust the flow rate of the reducing gas to ; in, is the current flow rate of reducing gas, is the maximum reducing gas flow rate allowed to be adjusted, is the conversion coefficient.

[0023] Through the above technical solution, this embodiment provides a method for generating a first adjustment instruction and a method for adjusting the flow rate of the introduced reducing gas according to the first adjustment instruction. First, according to the obtained reaction temperature and the concentration of the reducing gas at the outlet, a reaction temperature variation curve over time in a small cycle is formulated. And the reduction gas concentration at the outlet changes with time , and the time length of the small cycle can be determined artificially, so that the formula Get the judgment value ,formula Indicates the difference between the temperature change and the standard temperature change. Generally speaking, the larger the difference between the temperature and the standard temperature, the higher the reaction temperature, indicating that the flow rate of the reducing gas introduced is too low to take away the reaction heat. In any case, when the difference is smaller, it means that the gas flow rate is too high and takes away most of the heat. Therefore, when the difference between the temperature and the standard temperature is smaller, the judgment value is The larger the value, the same formula It indicates the difference between the reducing gas concentration at the outlet and the standard reducing gas concentration. When the difference is larger, it means that the reducing gas concentration at the outlet is higher, which indicates that the gas flow rate is too high and does not fully participate in the reaction. On the contrary, if the detected reducing gas concentration is lower, it may mean that the flow rate is too low, resulting in the gas staying in the reactor for too long and being over-consumed. Therefore, when the formula The larger the value of By comprehensively analyzing the temperature and the concentration of the reducing gas at the outlet, we can more accurately understand the condition of the reducing gas, so as to make timely adjustments to ensure the reducing atmosphere. The preset judgment threshold interval For comparison, when When , it means that the judgment value is normal, that is, the flow rate of the reducing gas introduced is normal and does not need to be adjusted. Otherwise, it means that it is abnormal, and a first adjustment instruction is generated to adjust the flow rate. The adjustment method is: when When , it means that the judgment value is large, that is, the other flow rates introduced are too high. In order to ensure the reaction atmosphere in the reduction furnace, the formula Adjust the flow rate of the reducing gas to From the formula, we can see that the more the excess, the more the amount needs to be adjusted and reduced. In order to ensure the normal reaction, the flow rate of the gas cannot be reduced infinitely. Therefore, a maximum reduction gas flow rate that can be adjusted is set to ensure the normal reaction. , indicating that the flow rate of the reducing gas introduced at this time is small. In order to ensure the reaction atmosphere in the reduction furnace, the formula Increase the flow rate of the reducing gas to In this way, a comprehensive analysis can be conducted in real time based on the temperature changes in the reduction furnace and the changes in the concentration of the reducing gas at the outlet to determine whether the flow rate of the reducing gas is normal. If it is abnormal, the flow rate of the gas introduced can be increased or decreased based on the judgment result, thereby ensuring the atmosphere in the reaction furnace and thus ensuring the quality of the generated product.

[0024] In the above technical solution, the preset standard reaction temperature variation curve over time , The curve of standard reducing gas concentration preset at the outlet changing with time , conversion coefficient The threshold interval can be determined based on experimental data combined with historical data. , Temperature reference value , concentration reference value , weight coefficient as well as , the maximum reduction gas flow rate allowed to be adjusted This can be determined based on historical experience data, which will not be elaborated here.

[0025] As an embodiment of the present invention, the method of thermal reduction treatment in step 3 further includes: within a large cycle, the large cycle includes n small cycles, analyzing according to the obtained judgment value to determine whether to generate a second adjustment instruction, thereby adjusting the flow rate of the introduced reducing gas, wherein the second adjustment instruction generation method is: Get the big cycle The number of times d, through the formula Get the percentage value , and the obtained percentage value The ratio threshold is set Make a comparison; when , a second adjustment instruction is generated; The second adjustment instruction includes an increase instruction and a decrease instruction; Get the big cycle The number of as well as The number of , By formula The first judgment coefficient ; when , a reduction instruction is generated, and then the formula Reduce the flow rate of reducing gas speed; By formula The second evaluation coefficient ; when , an increase instruction is generated, and then the formula Increase the flow rate of reducing gas speed; in, , is the number of times the judgment value is greater than the average judgment value, is the maximum judgment value within the large cycle, The number of times the judgment value is less than the average judgment value, is the minimum judgment value within the large cycle, as well as is the threshold coefficient, , , , is the proportionality coefficient, as well as is the conversion coefficient.

[0026] Through the above technical solution, this embodiment provides a method for adjusting the flow rate of the reducing gas. First, a large cycle is formulated, and the large cycle contains n small cycles. The number of times d, through the formula Get the percentage value , and the obtained percentage value The ratio threshold is set To compare; when When , it means that the number of abnormalities in the large cycle is large, and the flow rate needs to be adjusted, then a second adjustment instruction is generated, and the second adjustment instruction includes an increase instruction and a decrease instruction, so the large cycle is obtained. The number of as well as The number of , respectively, through the formula The first judgment coefficient , through the formula The second evaluation coefficient ,formula It can be expressed as obtaining The number of And the proportion of the number of times the judgment value is greater than the average judgment value to the total number of times. The larger the value, the higher the judgment value in the entire large cycle. The value of is also relatively large, indicating that the gas flow rate is too much, and the formula Indicates the maximum judgment value and judgment threshold within a large cycle The difference between the two values ​​is that when the value is larger, it can also indicate that the gas flow rate is too much, so the formula The first judgment coefficient and set the threshold coefficient For comparison, when When the flow rate is too high, a reduction instruction is generated to ensure the reaction atmosphere. Reduce the flow rate of reducing gas From the formula, we can see that the larger the excess value is, the more the flow rate needs to be reduced. Indicated as obtained in a large cycle The number of And the proportion of the number of times the judgment value is less than the average judgment value to the total number of times. The larger the value, the higher the judgment value in the entire large cycle. The value of is small, indicating that the flow rate of the gas is too small, and the formula Indicates the maximum judgment value and judgment threshold within a large cycle The difference between the two values ​​is that when the value is larger, it can also indicate that the gas flow rate is smaller. Therefore, the formula The second evaluation coefficient and set the threshold coefficient For comparison, when , indicating that the flow rate is too small. In order to ensure the reaction atmosphere, an increase instruction is generated. At this time, the formula Increase the flow rate of reducing gas From the formula, it can be seen that the larger the value exceeds, the larger the flow rate needs to be increased. In this way, the flow rate of the reducing gas can be judged to be normal by combining the judgment value in the large cycle, and the abnormal flow rate can be adjusted in time, so that the reaction atmosphere in the entire reduction furnace is in the best state, thereby ensuring the product quality.

[0027] In the above technical solution, the threshold coefficient as well as , proportionality coefficient , , , can be determined based on historical experience data, and the conversion coefficient as well as It can be determined based on experimental data and historical data, and the length of the large cycle can be determined artificially based on actual conditions, which will not be elaborated here.

[0028] A device for purifying mixed positive and negative electrode powder of waste lithium iron phosphate battery is used to implement the above-mentioned purification method, and the purification device includes but is not limited to the above-mentioned crusher, screening equipment, reduction furnace, magnetic separator, etc.

[0029] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for purifying mixed positive and negative electrode powder of waste lithium iron phosphate batteries, characterized in that: The method comprises: Step 1: dismantle the waste lithium iron phosphate battery, perform a complete discharge process, take out the positive and negative electrode materials, and crush them into multiple granular materials through a crusher; Step 2: Use screening equipment to screen the crushed material to obtain positive and negative electrode mixed powders with relatively uniform sizes; Step 3: placing the obtained positive and negative electrode mixed powder into a reduction furnace for thermal reduction treatment to obtain reduced powder; Step 4: Cool the reduced powder to room temperature, refine it, and then use a magnetic separator to separate the iron powder with strong magnetism from the non-magnetic powder; Step 5: Use chemical treatment to further collect the metals in the non-magnetic powder.

2. The method for purifying the positive and negative electrode mixed powder of waste lithium iron phosphate batteries according to claim 1, characterized in that: The method of thermal reduction treatment in step 3 includes: Place the positive and negative electrode mixed powders into the reduction furnace, and set the initial reaction temperature, the flow rate and velocity of the reducing gas; Acquire the reaction temperature in the reduction furnace and the concentration of the reducing gas obtained at the outlet of the reduction furnace, so as to analyze the obtained reaction temperature and reducing gas concentration every small period and generate a judgment value; The flow rate of the introduced reducing gas is analyzed to determine whether it is qualified according to the generated judgment value. If it is unqualified, the flow rate of the introduced reducing gas is adjusted according to the generated first adjustment instruction.

3. The method for purifying the positive and negative electrode mixed powder of waste lithium iron phosphate batteries according to claim 2, characterized in that: The method for generating the first adjustment instruction is: According to the obtained reaction temperature and the concentration of reducing gas at the outlet, a curve of reaction temperature variation over time in a small cycle is drawn up. And the reduction gas concentration at the outlet changes with time ; By formula Get the judgment value ; The judgment value obtained The preset judgment threshold interval To compare: when , a first adjustment instruction is generated; in, is the preset standard reaction temperature versus time curve, The standard reducing gas concentration curve preset at the outlet changes with time. is the temperature reference value, is the concentration reference value, as well as is the weight coefficient, is the start time of the small cycle, The end time of the small cycle.

4. The method for purifying the positive and negative electrode mixed powder of waste lithium iron phosphate batteries according to claim 3, characterized in that: The method for adjusting the flow rate of the introduced reducing gas according to the first adjustment instruction is: when When , the formula Adjust the flow rate of the reducing gas to ; when When , the formula Adjust the flow rate of the reducing gas to ; in, is the current flow rate of reducing gas, is the maximum reducing gas flow rate allowed to be adjusted, is the conversion coefficient.

5. The method for purifying the positive and negative electrode mixed powder of waste lithium iron phosphate batteries according to claim 4, characterized in that: The method of thermal reduction treatment in step 3 further comprises: In a large cycle, which includes n small cycles, analysis is performed based on the obtained judgment value to determine whether to generate a second adjustment instruction, thereby adjusting the flow rate of the introduced reducing gas.

6. The method for purifying the positive and negative electrode mixed powder of waste lithium iron phosphate batteries according to claim 5, characterized in that: The second adjustment instruction generation method is: Get the big cycle The number of times d, through the formula Get the percentage value , and the obtained percentage value The ratio threshold is set Make a comparison; when When , a second adjustment instruction is generated.

7. The method for purifying the positive and negative electrode mixed powder of waste lithium iron phosphate batteries according to claim 6, characterized in that: The second adjustment instruction includes an increase instruction and a decrease instruction; Get the big cycle The number of times and The number of ; By formula The first judgment coefficient ; when When , a reduction instruction is generated; By formula The second evaluation coefficient ; when When , an increase instruction is generated; in, , is the number of times the judgment value is greater than the average judgment value, is the maximum judgment value within the large cycle, The number of times the judgment value is less than the average judgment value, is the minimum judgment value within the large cycle, as well as is the threshold coefficient, , , , is the proportionality coefficient.

8. The method for purifying the positive and negative electrode mixed powder of waste lithium iron phosphate batteries according to claim 7, characterized in that: When a reduction instruction is generated, the formula Reduce the flow rate of reducing gas speed; When an increase instruction is generated, the formula Increase the flow rate of reducing gas speed; in, as well as is the conversion coefficient.

9. A device for purifying the mixed positive and negative electrode powder of waste lithium iron phosphate batteries, characterized in that: Used to implement the method for purifying mixed positive and negative electrode powder of waste lithium iron phosphate battery described in claims 1-8, the purification device includes but is not limited to a crusher, a screening device, a reduction furnace, and a magnetic separator.

Images