A system and method for efficiently separating and extracting lithium from electrolytic aluminum solid waste

Abstract

The present invention provides a system and method for separating and extracting lithium from electrolytic aluminum solid waste. The method first crushes the waste cathode carbon blocks, then separates the electrolyte from the waste cathode carbon blocks by heating in a high-temperature electric furnace, and finally injects the electrolyte into a molten salt electrochemical reactor for continuous heating to remove impurities in the electrolyte and further enrich the Li element. This method can not only efficiently separate the electrolyte from the carbonaceous components in the waste cathode carbon blocks, but also enrich lithium-containing substances from the separated electrolyte, solving the problem that a large amount of hazardous waste waste cathode carbon blocks generated in the electrolytic aluminum industry cannot be harmlessly disposed of, and realizes efficient resource recycling of electrolytic aluminum solid waste.

Description

Technical Field

[0001] The present invention relates to the field of environmentally friendly solid waste treatment, and in particular to a system and method for efficiently separating and extracting lithium from electrolytic aluminum solid waste. Background Art

[0002] Waste cathode carbon blocks are a type of solid waste that is produced during the production of aluminum electrolysis. The cathode carbon blocks at the bottom and sides of the electrolytic cell are inevitably corroded by high-temperature melt (950-970°C) for a long time. They are repaired and replaced after 4-6 years of use due to deformation, cracking and other problems. Waste cathode carbon blocks have been listed as non-ferrous metal smelting waste (HW48) in the National List of Hazardous Wastes (2021 edition) with a code of 321-023-48 because they absorb a large amount of soluble fluoride and a small amount of cyanide and other harmful substances.

[0003] my country is the world's largest producer of primary aluminum. Every ton of primary aluminum produced generates about 10 to 15 kg of waste cathode carbon blocks. Taking 2023 as an example, China's electrolytic aluminum output is 41.59 million tons. Based on this calculation, the annual output of waste cathode carbon blocks is 415,900 tons to 623,800 tons. Waste cathode carbon blocks are mainly composed of carbonaceous components (about 60% to 70%) and electrolytes (about 30% to 40%). Both components have high recycling value, especially the electrolyte. With the development and application of lithium-containing medium- and low-grade bauxite in recent years, the Li element has accumulated for a long time in the electrolyte of aluminum electrolytic cells using this type of alumina raw materials, and its concentration can reach 1.0 to 2.7% (measured in Li + Therefore, the efficient resource recycling of waste cathode carbon blocks from electrolytic aluminum, especially the separation and extraction of lithium from them, is of great significance. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for efficiently separating and extracting lithium from electrolytic aluminum solid waste, comprising the following steps:

[0005] Step 1: Send the waste cathode carbon blocks from electrolytic aluminum into the crusher for crushing.

[0006] Step 2: Load the crushed waste cathode carbon blocks into a high-temperature melting furnace, and load covering material on the upper layer of the high-temperature melting furnace to prevent high-temperature oxidation.

[0007] Step 3: The high-temperature melting furnace is powered for heating, and the gas generated during the heating process is discharged from the exhaust port under negative pressure and then emptied after being harmlessly treated.

[0008] Step 4: After the heating is completed, the carbonaceous components in the waste cathode carbon block remain in the high-temperature melting furnace, and the electrolyte close to the cathode of the high-temperature melting furnace flows into the cathode end of the molten salt electrolysis furnace from the discharge port No. 1, and the electrolyte close to the anode of the high-temperature melting furnace flows into the anode end of the molten salt electrolysis furnace from the discharge port No. 2; after adding the electrolyte, the molten salt electrolysis furnace is sealed, and power is continuously supplied for heating for a period of time, so that the Li element is fully enriched at the cathode end of the molten salt electrolysis furnace, and finally a lithium-rich electrolyte is obtained at the cathode end of the molten salt electrolysis furnace, and a lithium-poor electrolyte is obtained at the anode end of the molten salt electrolysis furnace.

[0009] In some embodiments, the crusher in step 1 is one or more of a jaw crusher, a box crusher, a hammer crusher, and a drum ball mill.

[0010] In some embodiments, step 1 requires breaking the spent cathode carbon blocks into blocks of 3 to 10 cm.

[0011] In some embodiments, the covering material in step 2 is one or more of alumina, anthracite, and graphite powder.

[0012] In some embodiments, in step 3, the high temperature melting furnace is heated by applying voltage according to a preset temperature regime, wherein the temperature regime is:

[0013] The first stage: room temperature ~ 1000℃, time 0 ~ 15h;

[0014] The second stage: 1000-2200℃, time is 15-25h;

[0015] The third stage: 2000-2200℃, time is 25-40h;

[0016] The fourth stage: 2200℃~room temperature, time 40~60h, natural cooling until the slag can be removed mechanically.

[0017] After heating in step 4, the carbonaceous components in the waste cathode carbon block remain in the high-temperature melting furnace and can be removed by slagging later. The carbonaceous components are mainly graphite with a purity of 90% to 98%, which can be recycled as a resource after being crushed into graphite blocks or graphite powder. In some embodiments, the carbonaceous components are crushed into particles of 0 to 10 mm and returned to step 2 for recycling as a covering material.

[0018] In some embodiments, in step 4, before the electrolyte discharged from the high-temperature melting furnace flows into the molten salt electrolysis furnace, the molten salt electrolysis furnace is preheated, and the preheating temperature is >400°C.

[0019] In some embodiments, in step 4, the heating temperature is 1200-1400° C., and the heating time is 5-10 hours.

[0020] After separation and discharge, the Li content in the lithium-rich electrolyte is greater than 4%, and the Li content in the lithium-poor electrolyte is less than 0.3%.

[0021] On the other hand, the present invention also provides a system for separating and extracting lithium from electrolytic aluminum solid waste, which can be used to perform the above method, including the following parts:

[0022] Crusher, used for crushing waste cathode carbon blocks from electrolytic aluminum;

[0023] The high-temperature melting furnace is used to accommodate the crushed waste cathode carbon blocks, and the upper layer thereof is filled with covering materials to prevent high-temperature oxidation; it is then powered for heating, and the gas generated during the heating process is discharged through the exhaust port under negative pressure, and then emptied after harmless treatment; after the heating is completed, the carbonaceous components in the waste cathode carbon blocks remain in the high-temperature melting furnace; the electrolyte close to the cathode of the high-temperature melting furnace flows into the cathode end of the molten salt electrolysis furnace from the discharge port No. 1, and the electrolyte close to the anode of the high-temperature melting furnace flows into the anode end of the molten salt electrolysis furnace from the discharge port No. 2;

[0024] The molten salt electrolysis furnace is continuously powered and heated, so that the Li element is fully enriched at the cathode end of the molten salt electrolysis furnace; ultimately, a lithium-rich electrolyte is obtained at the cathode end of the molten salt electrolysis furnace, and a lithium-poor electrolyte with high purity is obtained at the anode end of the molten salt electrolysis furnace.

[0025] In some embodiments, the furnace body of the molten salt electrolysis furnace is made of graphite.

[0026] In some embodiments, the lining material of the high-temperature melting furnace is one or more of silicon carbide bricks, magnesia carbon bricks, high-alumina hollow bricks, and silicon nitride bricks, and is built in a multi-layer continuous masonry manner.

[0027] In some embodiments, at the bottom of the high-temperature melting furnace, there are two inverted cone structures at the cathode and the anode, respectively, corresponding to the discharge port No. 1 and the discharge port No. 2, so as to collect the molten electrolyte and discharge it quickly through the discharge port.

[0028] The method provided by the present invention can not only efficiently separate the electrolyte and carbonaceous components in the waste cathode carbon blocks, but also enrich the lithium-containing substances from the separated electrolyte, thereby solving the problem that a large amount of hazardous waste waste cathode carbon blocks generated in the electrolytic aluminum industrial production cannot be harmlessly disposed of as resources, and realizing the efficient resource recycling of electrolytic aluminum solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A flow chart of a method for efficiently separating and extracting lithium from electrolytic aluminum solid waste provided by the present invention is shown. DETAILED DESCRIPTION

[0031] The solution provided in this specification is described below in conjunction with the accompanying drawings.

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0033] In the description of the embodiments of the present application, words such as "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a concrete way.

[0034] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, B exists alone, and A and B exist at the same time. In addition, unless otherwise specified, the term "plurality" means two or more.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. The terms "include", "comprises", "has" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0036] The present invention provides a method for efficiently separating and extracting lithium from solid waste from electrolytic aluminum. The method first crushes the waste cathode carbon blocks, then separates the electrolyte from the waste cathode carbon blocks by heating them in a high-temperature electric furnace, and finally injects the electrolyte into a molten salt electrochemical reactor to achieve the purpose of removing impurities in the electrolyte and further enriching the Li element. The method provided by the present invention is further explained in conjunction with the accompanying drawings. The process flow chart of the method is as follows: Figure 1 As shown, the specific steps are as follows:

[0037] Step 1: Send the waste cathode carbon blocks from electrolytic aluminum into the crusher for crushing.

[0038] In some embodiments, the crusher is one or more of a jaw crusher, a box crusher, a hammer crusher, and a drum ball mill.

[0039] In some embodiments, step 1 requires breaking the spent cathode carbon blocks into blocks of 3 to 10 cm.

[0040] This step of crushing the spent cathode carbon blocks is mainly to facilitate subsequent assembly, filling and separation of electrolyte after heating.

[0041] Step 2: Load the crushed waste cathode carbon blocks into a high-temperature melting furnace, and load covering material on the upper layer of the high-temperature melting furnace to prevent high-temperature oxidation.

[0042] In some embodiments, the covering material in step 2 is one or more of alumina, anthracite, and graphite powder.

[0043] Step 3: supplying electricity to heat the high-temperature melting furnace, and the gas generated during the heating process is discharged through the exhaust port under negative pressure, and then emptied after being harmlessly treated;

[0044] In some embodiments, in step 3, the high temperature melting furnace is heated by applying voltage according to a preset temperature regime, wherein the temperature regime is:

[0045] The first stage: room temperature ~ 1000℃, time 0 ~ 15h;

[0046] The second stage: 1000-2200℃, time is 15-25h,

[0047] The third stage: 2000-2200℃, time is 25-40h;

[0048] The fourth stage: 2200℃~room temperature, time 40~60h, natural cooling until the slag can be removed mechanically.

[0049] This step is to heat with electricity in order to achieve the effect of efficiently separating the electrolyte from the carbonaceous components in the spent cathode carbon block. After heating, the molten electrolyte sinks to the lower layer of the high-temperature melting furnace and flows out into the molten salt electrolysis furnace in step 4, while the carbonaceous components remain in the high-temperature melting furnace.

[0050] Step 4: After the heating is completed, the carbonaceous components in the waste cathode carbon block remain in the high-temperature melting furnace, and the electrolyte close to the cathode of the high-temperature melting furnace flows into the cathode end of the molten salt electrolysis furnace from the discharge port No. 1, and the electrolyte close to the anode of the high-temperature melting furnace flows into the anode end of the molten salt electrolysis furnace from the discharge port No. 2; after adding the electrolyte, the molten salt electrolysis furnace is sealed, and power is continuously supplied for heating for a period of time, so that the Li element is fully enriched at the cathode end of the molten salt electrolysis furnace, and finally a lithium-rich electrolyte is obtained at the cathode end of the molten salt electrolysis furnace, and a lithium-poor electrolyte is obtained at the anode end of the molten salt electrolysis furnace.

[0051] After heating in step 4, the carbonaceous components in the waste cathode carbon block remain in the high-temperature melting furnace and can be removed by slagging later. The carbonaceous components are mainly graphite with a purity of 90% to 98%, which can be recycled and reused as resources after being crushed into graphite blocks or graphite powder. In some embodiments, the carbonaceous components in step 4 are crushed into particles of 0 to 10 mm and returned to step 2 for recycling as covering materials.

[0052] In some embodiments, in step 4, before the electrolyte discharged from the high-temperature melting furnace flows into the molten salt electrolysis furnace, the molten salt electrolysis furnace is preheated, and the preheating temperature is >400°C.

[0053] In some embodiments, in step 4, the heating temperature is 1200-1400° C., and the heating time is 5-10 hours.

[0054] After separation and discharge, the Li content in the lithium-rich electrolyte is greater than 4%, and the Li content in the lithium-poor electrolyte is less than 0.3%.

[0055] The following is a detailed description of the electrolytic aluminum solid waste treatment method provided by the present invention in conjunction with the embodiments:

[0056] Example 1

[0057] Take 1000kg of the cathode carbon blocks of the electrolytic aluminum waste to be processed, add them into the box crusher, crush them to 3-10cm, and then send them into the high-temperature melting furnace, and put the covering material on the upper layer to prevent high-temperature oxidation. According to the pre-set temperature system, the high-temperature melting furnace is powered and heated, and the gas generated during the heating process is discharged from the exhaust port under negative pressure and emptied after harmless treatment. The temperature system is:

[0058] The first stage: room temperature ~ 1000℃, time is 13h;

[0059] The second stage: 1000-2200℃, time is 20h;

[0060] The third stage: 2000-2200℃, time is 30h;

[0061] The fourth stage: 2200℃ ~ room temperature, natural cooling until the slag can be removed mechanically.

[0062] After the heating is completed, the carbonaceous components in the waste cathode carbon blocks remain in the high-temperature melting furnace, and are subsequently removed by slagging to obtain 654kg of carbonaceous components for use, the main component of which is graphite. The electrolyte close to the cathode of the high-temperature melting furnace flows into the cathode end of the molten salt electrolysis furnace from the No. 1 discharge port, and the electrolyte close to the anode of the high-temperature melting furnace flows into the anode end of the molten salt electrolysis furnace from the No. 2 discharge port; after adding the electrolyte, the molten salt electrolysis furnace is sealed and continuously powered for heating at a temperature of 1300°C for 6 hours. Finally, 148kg of lithium-rich electrolyte is obtained at the cathode end of the molten salt electrolysis furnace, and 153kg of lithium-poor electrolyte is obtained at the anode end of the molten salt electrolysis furnace. The gas and dust discharged by negative pressure are about 45kg. It has been tested that the Li content (measured as Li + The Li content in the lithium-poor electrolyte (in terms of Li + The total weight of the product is 0.2%.

[0063] In summary, compared with the prior art, the method for efficiently separating and extracting lithium from electrolytic aluminum solid waste provided by the present invention has the following beneficial effects:

[0064] 1) The electric heating method adopted in the present invention to dispose of electrolytic aluminum solid waste in a resource-based manner can effectively reduce environmental pollution and improve the safety factor of operation;

[0065] 2) The high-temperature melting furnace used in the present invention is resistant to high temperatures and corrosion, and can achieve efficient separation of the electrolyte and carbonaceous components in the waste cathode carbon blocks; the molten salt electrolysis furnace used can utilize the characteristics of molten salt electrolysis to enrich the Li element and achieve the purpose of resource utilization of the waste cathode carbon blocks.

[0066] 3) The use of pyrometallurgical methods to treat electrolytic aluminum solid waste shortens the process flow. While achieving separation of electrolyte and carbonaceous components through high-temperature melting, the electrolyte can be further utilized as a resource to enrich the Li element therein, which can greatly save energy in industrial production.

[0067] On the other hand, the present invention also provides a system for separating and extracting lithium from electrolytic aluminum solid waste, which can be used to perform the above method, including the following parts:

[0068] Crusher, used for crushing waste cathode carbon blocks from electrolytic aluminum;

[0069] The high-temperature melting furnace is used to accommodate the crushed waste cathode carbon blocks, and the upper layer thereof is filled with covering materials to prevent high-temperature oxidation; it is then powered for heating, and the gas generated during the heating process is discharged through the exhaust port under negative pressure, and then emptied after harmless treatment; after the heating is completed, the carbonaceous components in the waste cathode carbon blocks remain in the high-temperature melting furnace; the electrolyte close to the cathode of the high-temperature melting furnace flows into the cathode end of the molten salt electrolysis furnace from the discharge port No. 1, and the electrolyte close to the anode of the high-temperature melting furnace flows into the anode end of the molten salt electrolysis furnace from the discharge port No. 2;

[0070] In some embodiments, the lining material of the high-temperature melting furnace is one or more of silicon carbide bricks, magnesia carbon bricks, high-alumina hollow bricks, and silicon nitride bricks, and is built in a multi-layer continuous masonry manner.

[0071] In some embodiments, at the bottom of the high-temperature melting furnace, there are two inverted cone structures at the cathode and the anode, respectively, corresponding to the discharge port No. 1 and the discharge port No. 2, so as to collect the molten electrolyte and discharge it quickly through the discharge port.

[0072] The molten salt electrolysis furnace is continuously heated by electricity, so that the Li element is fully enriched at the cathode end of the molten salt electrolysis furnace; finally, a lithium-rich electrolyte is obtained at the cathode end of the molten salt electrolysis furnace, and a lithium-poor electrolyte with a high purity is obtained at the anode end of the molten salt electrolysis furnace. In some embodiments, the furnace body of the molten salt electrolysis furnace is made of graphite.

[0073] It should be noted that the above components can be assembled into a production line to realize the automated processing of waste cathode carbon blocks of electrolytic aluminum. In addition, the functions of each component can also refer to the relevant embodiments when introducing the method above, and will not be repeated here.

[0074] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solution of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for separating and extracting lithium from electrolytic aluminum solid waste, characterized in that: The following steps are involved: Step 1: Send the waste cathode carbon blocks of electrolytic aluminum into the crusher for crushing; Step 2: Load the crushed waste cathode carbon blocks into a high-temperature melting furnace, and add covering materials to the upper layer of the high-temperature melting furnace to prevent high-temperature oxidation; Step 3: supplying electricity to heat the high-temperature melting furnace, and the gas generated during the heating process is discharged through the exhaust port under negative pressure, and then emptied after harmless treatment; Step 4: at the bottom of the high-temperature melting furnace, the cathode and the anode are respectively provided with discharge outlets of inverted cone structures, which are respectively recorded as discharge outlet No. 1 and discharge outlet No. 2; After the heating is completed, the carbonaceous components in the spent cathode carbon blocks remain in the high-temperature melting furnace, and the electrolyte close to the cathode of the high-temperature melting furnace flows into the cathode end of the molten salt electrolysis furnace from the No. 1 discharge port, and the electrolyte close to the anode of the high-temperature melting furnace flows into the anode end of the molten salt electrolysis furnace from the No. 2 discharge port; after adding the electrolyte, the molten salt electrolysis furnace is sealed, and power is continuously supplied for heating for a period of time, so that the Li element is fully enriched at the cathode end of the molten salt electrolysis furnace, and finally a lithium-rich electrolyte is obtained at the cathode end of the molten salt electrolysis furnace, and a lithium-poor electrolyte is obtained at the anode end of the molten salt electrolysis furnace.

2. The method according to claim 1, characterized in that The crusher is one or more of a jaw crusher, a box crusher, a hammer crusher, and a drum ball mill.

3. The method according to claim 1, characterized in that The covering material is one or more of alumina, anthracite, and graphite powder.

4. The method according to claim 1, characterized in that: The high temperature melting furnace is heated by applying voltage according to a preset temperature regime, wherein: The first stage: room temperature ~ 1000℃, time 0 ~ 15h; The second stage: 1000-2200℃, time is 15-25h, The third stage: 2000-2200℃, time is 25-40h; The fourth stage: 2200℃~room temperature, time 40~60h, natural cooling until the slag can be removed mechanically.

5. The method according to claim 1, characterized in that After the carbonaceous component is crushed into particles of 0 to 10 mm, it is returned to step 2 and recycled as a covering material.

6. The method according to claim 1, characterized in that In the step 4, before the electrolyte discharged from the high-temperature melting furnace flows into the molten salt electrolysis furnace, the molten salt electrolysis furnace is preheated, and the preheating temperature is greater than 400°C.

7. The method according to claim 1, characterized in that In step 4, the heating temperature of continuous power supply heating is 1200-1400° C., and the time is 5-10 hours.

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