Rare earth electrolysis dust collection material pretreatment process

Abstract

The invention discloses a rare earth electrolysis dust collection material pretreatment process, and belongs to the technical field of rare earth molten salt electrolysis recycled material treatment. Comprising the following steps that an electrolytic cell with the service life smaller than 12 months is selected, a receiver is taken out, the height of a cathode is adjusted to be 1-2 cm lower than the bottom of an anode, a voltage stabilization mode is adopted as a power output mode, and the voltage is controlled to be 8.5-9.5 V; and adding the dust collecting material once every 5 minutes, cleaning the carbon powder on the surface once every 10 minutes, scooping out metal from the bottom by using a titanium spoon for casting every 2-3 hours, and scooping out the produced electrolyte every 1.5-2.5 hours. According to the method, valuable elements such as L and F are fully recycled, the follow-up environment-friendly treatment pressure is relieved, the rare earth recycling rate of the electrolysis procedure is increased, and meanwhile the weight of recycled materials needing to be further treated is greatly reduced. Wherein the rare earth recovery rate is not less than 86%, the L element yield is not less than 96%, the F element yield is not less than 95%, the weight of the reclaimed material is reduced by 90%, the addition amount of the new electrolyte is reduced by 10%, and the cost is remarkably reduced.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth molten salt electrolysis recovery material processing, in particular to a rare earth electrolysis dust collection material pretreatment process. Background Art

[0002] Rare earth electrolysis generally adopts the fluoride system molten salt electrolysis process, adding oxides to the electrolytic cell to produce rare earth metals. In this process, the anode will produce a large amount of CO, CO2, and a small amount of CF4 and other fluorine-containing gases. The escaped gas will carry molten salt and oxides into the flue gas recovery system. At the same time, high temperature will also cause part of the molten salt to volatilize. This type of flue gas needs to be dedusted and defluorinated by equipment such as bag filters and absorption towers, and finally produces fluorine-containing wastewater and dust collection materials. Fluorine-containing wastewater is discharged after environmental protection treatment. The dust collection materials contain impurities such as C, Fe, Li, Al, etc., and need to be recycled after certain treatment. The output of dust collection materials is about 0.8% of the metal output.

[0003] At present, there are two commonly used recycling and processing technologies for dust collection materials. The first is the direct reuse method. This method directly mixes the dust collection materials with oxides in a certain proportion, and then directly adds them to the electrolytic cell for production. Although this method is simple, it has the following disadvantages: 1. Because it contains a large amount of impurities and has a high content of rare earth fluoride and lithium fluoride, a large amount of oxides are required for mixing. The weight of the oxides during mixing is generally 100 times the weight of the dust collection materials. 2. It is necessary to add special mixing equipment and personnel, which greatly increases the cost. At the same time, adding processes will directly increase the loss of oxides. 3. The substances in the dust collection materials are all substances brought out by the anode gas or high-temperature volatile substances with a low density. If they are added again in the form of powder, it is easy to cause secondary volatilization and large losses.

[0004] The second is the sulfuric acid high-temperature decomposition method, which directly mixes the dust collection material with rare earth minerals in a certain proportion, adds sulfuric acid, and enters a rotary kiln for high-temperature decomposition, followed by leaching, impurity removal, transformation, extraction, precipitation, calcination and other processes to completely separate it into rare earth oxides. Although this method has complete decomposition, high recovery rate, and extremely pure oxides, it has the following disadvantages: 1. The processing flow is relatively long. This processing method is a complete rare earth smelting and separation method with a long process and high cost. 2. Valuable elements such as F and Li in the dust collection material are all treated as impurities and are not effectively recovered, which increases the processing pressure of the environmental protection process. Summary of the invention

[0005] The purpose of the present invention is to provide a rare earth electrolysis dust collection material pretreatment process, which has low treatment cost and high recovery rate of valuable elements, and can effectively reduce production costs, thereby solving the problems raised in the above background technology.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A rare earth electrolysis dust collection material pretreatment process comprises the following steps:

[0008] S1: An electrolytic cell with a service life of less than 12 months was selected as the carrier for processing dust collection materials; the receiver was taken out and the cathode height was adjusted to be 1 cm lower than the bottom of the anode; the power output mode adopted the voltage stabilization mode, the control voltage was 8.5~9.5V, and the current was 5500~6500A;

[0009] S2: Add dust collecting material every 5 minutes, and the amount of material added must ensure that the electrolytic cell does not have anode effect;

[0010] S3: Scoop out the produced electrolyte every 1.5-2.5 hours. The interval between scooping out the electrolyte must ensure that the electrolyte level does not exceed 2 cm below the top of the anode;

[0011] S4: Every 2-3 hours, scoop out the metal from the bottom of the electrolytic cell for casting. The time for scooping out the metal is adjusted according to the electrolytic voltage. When scooping out the metal, the electrolytic voltage shall not be less than 7.5V;

[0012] S5: Use a titanium colander to clean the carbon powder on the surface every 10 minutes and replace the anode every 12 hours;

[0013] S6: The electrolyte produced in step S3 is mixed with the new electrolyte in a ratio of 1:10 and added, and the mixed electrolyte is collected according to the usage of the electrolytic cell.

[0014] Furthermore, in step S1, the selected electrolytic cell is an 8000A electrolytic cell with a service life of 7 months.

[0015] Furthermore, in step S3, the produced electrolyte is scooped out every 1.5 hours, and after the temperature drops to room temperature, it is weighed and bagged.

[0016] Furthermore, in step S4, a titanium spoon is used to scoop out metal from the bottom of the electrolytic cell for casting every 3 hours, and after the temperature drops to room temperature, the metal is weighed and bagged.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0018] 1. The processing cost of the present invention is low. This process does not require the addition of new equipment and personnel. The electrolytic cells used are electrolytic cells close to the end of their service life, which can be fully utilized. The personnel used are original rare earth electrolysis workers.

[0019] 2. The present invention fully recovers valuable elements such as Li and F, reduces the subsequent environmental protection treatment pressure, partially recovers rare earth elements, improves the rare earth recovery rate of the electrolysis process, reduces production costs, and greatly reduces the weight of recycled materials that need further treatment. The rare earth recovery rate is not less than 86%, the Li element recovery rate is not less than 96%, the F element recovery rate is not less than 95%, the weight of recycled materials is reduced by 90%, the amount of new electrolyte added is reduced by 10%, and the cost is significantly reduced. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the specific data 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.

[0021] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0022] The rare earth electrolysis dust collection material pretreatment process provided by the present invention includes two parts: purification and separation and recycling. The remaining 10% needs to be further processed in the form of metal with high impurities. The purification and separation part is a molten salt electrolysis method; the recycling part is a mixed recycling method. The mixed recycling method is due to the high Li content in the produced electrolyte. In actual use, the produced old electrolyte needs to be added with the new electrolyte at the same time.

[0023] Example 1

[0024] This embodiment provides a rare earth electrolysis dust collection material pretreatment process, comprising the following steps:

[0025] S1: An 8000A electrolytic cell with a service life of 7 months was selected as the carrier for processing the dust collection material, and the components of the dust collection material added were shown in Table 1;

[0026] Take out the receiver, adjust the cathode height so that it is 1 cm lower than the bottom of the anode, and use the voltage stabilization mode for the power output. The voltage is controlled at around 9.0V, and the current is around 5800A.

[0027] S2: Determine the amount of material added while ensuring that the electrolytic cell does not have an anode effect. In this embodiment, 1.09 kg of dust collecting material is added every 5 minutes;

[0028] S3: Adjust the time of scooping out the electrolyte according to the height of the electrolyte liquid level. Determine the maximum interval time while ensuring that the electrolyte liquid level does not exceed 2 cm below the top of the anode. In this embodiment, the produced electrolyte is scooped out every 1.5 hours. After scooping out, the electrolyte liquid level is 8 cm below the top of the anode. The weight of the scooped electrolyte is about 14.3 kg. After the temperature drops to room temperature, weigh and bag it.

[0029] S4: adjusting the time for scooping out the metal according to the electrolysis voltage. In this embodiment, the electrolysis voltage is 8.2V when scooping out the metal. At this time, the interval time for scooping out the metal is 3 hours, and about 3.53 kg of metal is scooped out each time. After the temperature is lowered to room temperature, the metal is weighed and bagged;

[0030] S5: Use a titanium colander to clean the carbon powder on the surface every 10 minutes and replace the anode every 12 hours.

[0031] S6: Mix the produced electrolyte with the new electrolyte in a ratio of 1:10, collect and add the mixed electrolyte according to the usage of the electrolytic cell, and mix the electrolyte every time you collect it. The changes in output and quality are shown in Table 2;

[0032] The production lasted for 52 days and stopped after the furnace body broke. A total of 16.3 tons of dust collection materials were used, 11.9 tons of electrolyte and 1.47 tons of metal were produced, the rare earth recovery rate of the electrolysis process was 86.1%, the Li element recovery rate was 97.3%, the F element recovery rate was 98.2%, and the total rare earth recovery rate was 99.7%. Its output, content and recovery rate are shown in Tables 3 and 4.

[0033] Example 2

[0034] S1: An 8000A electrolytic cell with a service life of 8 months was selected as the carrier for processing the dust collection material. The composition of the dust collection material is shown in Table 1;

[0035] Take out the receiver, adjust the cathode height to 1 cm below the bottom of the anode, and use the voltage stabilization mode for the power output. The voltage is controlled at about 9.0V, and the current is about 6000A.

[0036] S2: Determine the amount of material added while ensuring that the electrolytic cell does not have an anode effect. In this embodiment, 1.03 kg of dust collecting material is added every 5 minutes;

[0037] S3: Adjust the time of scooping out the electrolyte according to the height of the electrolyte liquid level, and determine the maximum interval time while ensuring that the electrolyte liquid level does not exceed 2 cm below the top of the anode. In this embodiment, the produced electrolyte is scooped out every 1.8 hours, and the electrolyte liquid level after scooping out is 9 cm below the top of the anode. The weight of the scooped electrolyte is about 17.3 kg. After the temperature drops to room temperature, weigh and bag it;

[0038] S4: adjusting the time for scooping out the metal according to the electrolysis voltage. In this embodiment, the electrolysis voltage is 8.0V when scooping out the metal. At this time, the interval time for scooping out the metal is 3 hours. About 2.6 kg of metal is scooped out. After the temperature is lowered to room temperature, it is weighed and bagged;

[0039] S5: Use a titanium colander to clean the carbon powder on the surface every 10 minutes and replace the anode every 12 hours;

[0040] S6: Mix the produced electrolyte with the new electrolyte in a ratio of 1:10, collect and add according to the usage of the electrolytic cell, and mix them every time you collect the electrolyte. The changes in output and quality are shown in Table 2.

[0041] The production lasted for 36 days and stopped after the furnace body broke. A total of 10.7 tons of dust collection materials were used, 8.3 tons of electrolyte and 0.75 tons of metal were produced. The rare earth recovery rate of the electrolysis process was 89.6%, the Li element recovery rate was 96%, the F element recovery rate was 96.7%, and the total rare earth recovery rate was 99.6%. The changes in its output, content, and recovery rate are shown in Tables 3 and 4.

[0042] Embodiment 3:

[0043] S1: An 8000A electrolytic cell with a service life of 6 months was selected as the carrier for processing the dust collection material. The composition of the dust collection material is shown in Table 1;

[0044] Take out the receiver, adjust the cathode height to 1 cm below the bottom of the anode, use the voltage stabilization mode for power output, and control the voltage at around 8.7V. At this time, the current is around 5950A;

[0045] S2: Determine the amount of material added while ensuring that the electrolytic cell does not have an anode effect. In this embodiment, 1.04 kg of dust collecting material is added every 5 minutes;

[0046] S3: Determine the maximum interval time when the electrolyte level reaches 2 cm below the top of the anode, scoop out the produced electrolyte every 2.5 hours, and the electrolyte level after scooping out is 10 cm below the top of the anode. The weight of the scooped electrolyte is about 23.7 kg. After the temperature drops to room temperature, weigh and bag it;

[0047] S4: Adjust the time for scooping out the metal according to the electrolytic voltage. When scooping out the metal, the electrolytic voltage is 7.8V. At this time, the interval time is 2.5 hours. About 2.89 kg of metal is scooped out. After the temperature drops to room temperature, weigh and bag it.

[0048] S5: Use a titanium colander to clean the carbon powder on the surface every 10 minutes and replace the anode every 12 hours;

[0049] S6: The produced electrolyte is mixed with the new electrolyte in a ratio of 1:10, and added according to the usage of the electrolytic cell. The changes in output and quality are shown in Table 2;

[0050] The production lasted for 58 days and stopped after the furnace body broke. A total of 17.4 tons of dust collection materials were used, 13.2 tons of electrolyte and 1.61 tons of metal were produced. The rare earth recovery rate of the electrolysis process was 87.2%, the Li element recovery rate was 95.5%, the F element recovery rate was 98.7, and the total rare earth recovery rate was 99.7%. The changes in its output, content, and recovery rate are shown in Tables 3 and 4.

[0051] In summary, the present invention realizes the pretreatment of rare earth dust collection materials by controlling process parameters such as power output mode, voltage, current, cathode insertion depth, feeding amount, furnace exit time, and carbon powder cleaning time. In the electrolysis process, the rare earth recovery rate is not less than 86%, the Li element recovery rate is not less than 96%, the F element recovery rate is not less than 95%, the weight of the recovered material is reduced by 90%, the amount of new electrolyte added is reduced by 10%, and the cost is significantly reduced.

[0052] Table 1 Analysis results of dust collected in Example 1 (%)

[0053] serial number REO F Li C CaO MgO <![CDATA[Al2O3]]> Fe Example 1 53.6 29.8 5.8 4.37 0.78 0.021 0.56 3.92 Example 2 56 31.1 6.1 3.19 0.78 0.022 0.2 4.79 Example 3 57 30.2 6.3 3.93 0.78 0.024 0.48 4.13

[0054] Table 2 Electrolyte recycling results

[0055]

[0056] Table 3 Input, output and content

[0057]

[0058] Table 4 Recovery rate of valuable elements (%)

[0059]

Claims

1. A rare earth electrolysis dust collection material pretreatment process, characterized in that: The following steps are involved: S1: An electrolytic cell with a service life of less than 12 months was selected as the carrier for processing dust collection materials; the receiver was taken out, and the cathode height was adjusted to be 1-2 cm lower than the bottom of the anode; the power output mode adopted the voltage stabilization mode, and the control voltage was 8.5-9.5V and the current was 5500-6500A; S2: Add dust collecting material every 5 minutes, and the amount of material added must ensure that the electrolytic cell does not have anode effect; S3: Scoop out the produced electrolyte every 1.5-2.5 hours. The interval between scooping out the electrolyte must ensure that the electrolyte level does not exceed 2 cm below the top of the anode; S4: Every 2-3 hours, scoop out the metal from the bottom of the electrolytic cell for casting. The time for scooping out the metal is adjusted according to the electrolytic voltage. When scooping out the metal, the electrolytic voltage shall not be less than 7.5V; S5: Use a titanium colander to clean the carbon powder on the surface every 10 minutes and replace the anode every 12 hours; S6: The electrolyte produced in step S3 is mixed with the new electrolyte in a ratio of 1:10 and added, and the mixed electrolyte is collected according to the usage of the electrolytic cell.

2. A rare earth electrolysis dust collection material pretreatment process according to claim 1, characterized in that: In step S1, the selected electrolytic cell is an 8000A electrolytic cell with a service life of 7 months.

3. A rare earth electrolysis dust collection material pretreatment process according to claim 1, characterized in that: In step S3, the produced electrolyte is scooped out every 1.5 hours, and after the temperature drops to room temperature, it is weighed and bagged.

4. A rare earth electrolysis dust collection material pretreatment process according to claim 1, characterized in that: In step S4, metal is scooped out from the bottom of the electrolytic cell for casting using a titanium spoon every 3 hours, and after the temperature drops to room temperature, it is weighed and bagged.

Images