Method for co-processing electrolytic aluminum overhaul slag with converter steel slag

Abstract

The invention discloses a method for co-processing electrolytic aluminum overhaul slag with converter steel slag. First, carbon blocks in the overhaul slag produced by the electrolytic aluminum enterprise are crushed to less than 5 cm, the carbon blocks and waste refractory materials are mixed in a mass percentage of 20:80, and the mixture is processed to less than 1 mm by a rod mill and a Raymond mill, and then transported to a pelletizing production line for use as an overhaul slag powder material; converter sludge is added to the overhaul slag powder material as a binder, and the added amount of converter sludge is 5% to 10% of the mass of the overhaul slag powder material, and a high-pressure dry powder pelletizing machine is used to press it into pellets with a diameter of 30 to 50 mm, and then the pellets are transported to a converter production line and a hot slag production line for use; the pellets are used as a defoaming agent for converter foam slag or as a slag pressing defoaming agent for a slag pot or added to a slag pot filled with converter liquid steel slag, and the pellets are treated according to normal hot slag pouring or hot slag stuffing process.

Description

Technical Field

[0001] The invention relates to two technical fields: steel slag thermal coupling (steel slag online quenching and tempering) technology and harmless treatment of hazardous wastes, and specifically to a method for co-processing electrolytic aluminum overhaul slag with converter steel slag. Background Art

[0002] Aluminum electrolytic cells need to be overhauled after 4 to 7 years of operation. The dismantled waste is called overhaul slag, which mainly includes waste cathode carbon blocks, waste refractory materials, waste insulation materials, etc. Due to the large differences in current capacity, internal village structure, lining material types, electrolysis process conditions, operating systems, and cell life of each electrolytic aluminum plant, the specific composition of the waste is also quite different, but the main components are basically the same. The overhaul slag produced by the electrolytic aluminum industry contains soluble fluorides and cyanides, which are extremely harmful to the environment. It is a hazardous waste that is difficult to recycle in the electrolytic aluminum industry, especially the waste clay refractory materials and calcium silicate insulation board refractory materials in the overhaul slag.

[0003] Literature review (1) Li Hong published a paper titled “Pollution prevention and comprehensive utilization of aluminum electrolytic cell overhaul slag” in the 55th volume of the Nonferrous Metals magazine in 2003. The paper states that “During the storage process of electrolytic cell overhaul slag, the management of the slag field should be strengthened to prevent secondary pollution, and a comprehensive utilization method that can be widely applied should be found to ultimately achieve the goal of turning harm into benefit and turning waste into treasure.” (2) Li Chaonan published a paper titled “Harmless treatment of aluminum electrolytic cell overhaul slag” in the 9th issue of the Industrial Safety and Dust Control magazine in 2000. The paper states that “Sanitary landfill is the final treatment method for solid waste. Sanitary landfill requires that the bottom layer of the yard be treated with anti-seepage treatment, and the solid waste is landfilled in layers for harmless landfill. After compaction, the top layer is covered with soil to achieve forest (cultivation) recovery. method. Sanitary landfill requires safe storage, no collapse, no hidden dangers, and harmless treatment without polluting the land and groundwater. " (3) Gao Kangning, Chao Boyang, Shen Wenbin, and Yan Xionghua published a paper entitled "Analysis and Prevention Measures of Pollution from Overhaul Slag of Electrolytic Aluminum Plants" in the 8th issue of "Resource Conservation and Environmental Protection" in 2017. In the middle, there is a statement that "The treatment and disposal technologies of overhaul slag mainly include: rotary kiln roasting treatment, cement kiln coordinated treatment, bauxite sintering, flotation treatment, lime water soaking treatment, etc. Bauxite sintering can generally only treat the carbonaceous waste in the overhaul slag, and cannot thoroughly treat the overhaul slag. Flotation treatment and lime water soaking treatment will produce a large amount of toxic and harmful waste gases such as hydrogen cyanide, which have a great impact on the environment."

[0004] According to the above literature introduction, there is currently no process technology for co-processing overhaul slag using converter slag.

[0005] Converter slag is a by-product of converter steelmaking. The temperature of liquid converter slag is between 1350℃ and 1750℃. The converter liquid contains a large amount of physical heat that is difficult to use. In addition, the basicity of converter slag is high. The f-CaO and f-MgO contained in the slag affect the safety of the resource utilization of the slag. At present, there are a lot of literatures on the technical research of online quenching and tempering of converter slag to optimize the performance of converter slag. However, there is no literature on the relevant technology of using converter slag to coordinate the treatment of hazardous waste from the electrolytic aluminum industry. References (1) Xu Ying, Wang Qiaoling, Hu Chenguang, and Zhang Zizi published a paper titled "Research Progress of Online Reconstruction Technology of Liquid Steel Slag" in the 2nd issue of "Mineral Comprehensive Utilization" in 2019. The paper states: "This paper briefly describes the characteristics and existing problems of steel slag, and focuses on the effects of tempering components, temperature system, cooling system, atmosphere system, mixing system, process equipment, and thermodynamic and kinetic research on the gelling activity and volume stability of reconstructed steel slag during online reconstructing of liquid steel slag; finally, the problems existing in online reconstructing of steel slag and the more advanced technologies in the steel industry are discussed. Reconstruction of the development trend. ", the article did not mention the use of converter slag to treat overhaul slag; (2) Lv Kaihui published a paper entitled "Innovation and Governance of the Mechanism of Using Converter to Incinerate Combustible Industrial Waste" in the 5th issue of "China Metallurgy" in 2019. The article stated that "As the public's environmental awareness increases and the country pays more and more attention to environmental protection, Fujian Quanzhou Minguang Iron and Steel Co., Ltd. actively studies and explores the path of enterprise industrial waste disposal, and uses converter incineration to treat enterprise combustible industrial waste. This is of great significance for recycling resources, reducing social burdens, and reducing environmental risks." The article also did not mention the process of using converter slag to co-treat overhaul slag produced by the electrolytic aluminum industry.

[0006] In summary, there is currently no introduction to a process for utilizing converter slag to co-treat overhaul slag. Summary of the invention

[0007] The purpose of the present invention is to provide a method for co-processing electrolytic aluminum overhaul slag with converter steel slag, which utilizes the overhaul slag to optimize the mineral structure of the converter steel slag while achieving the harmless transformation of electrolytic aluminum hazardous waste and reducing the overall carbon emissions of the metallurgical industry.

[0008] The technical solution adopted by the present invention is a method for co-processing electrolytic aluminum overhaul slag with converter steel slag, which is carried out according to the following steps: 1. First, the overhaul slag generated by the electrolytic aluminum enterprise is transported to the steel slag plant, and the carbon blocks and refractory materials in the overhaul slag are picked and separated and then classified and stored; 2. The carbon blocks are crushed to less than 5 cm by a chain crusher, and the carbon blocks and waste refractory materials are mixed in a ratio of 20:80 by mass. The mixture is processed by a rod mill and a Raymond mill to less than 1 mm, and is transported to a pelletizing production line as an overhaul slag powder material for standby use; 3. The sludge of the operating furnace steel plant is pulled to the pelletizing production line for standby use; 4. The converter sludge is added as a binder to the above-mentioned overhaul slag powder material, and the added amount of the converter sludge is 5% to 10% of the mass of the overhaul slag powder material, and a high-pressure dry powder pelletizing machine is used to press it into pellets with a diameter of 30 to 50 mm. , and transported to the converter production line and the hot slag production line for standby use; 5. When the converter smelting is close to the end, the above-mentioned pellets are added before the converter slag is poured out, and the addition amount is 3-5kg per ton of steel, and used as a defoaming agent for the converter foam slag; or, when pouring the furnace and slag before the converter taps out steel, the above-mentioned pellets are used as slag pressing and defoaming agents for the slag pot, and are added to the slag pot along with the converter slag flow, and the addition amount is 250kg-500kg per ton of slag; 6. When the two processes in step 5 are inconvenient to use, after the converter slag is finished, the slag pot filled with the converter liquid steel slag is transported to the slag plant, and the above-mentioned pellets are added to the slag pot filled with the converter liquid steel slag, and the addition amount is 100-250kg per ton of slag. After adding, the slag pot is allowed to stand for 30 minutes, and the converter slag in the slag pot is poured into another empty slag pot. After standing for 60 minutes, it can be treated according to the normal hot slag pouring or hot slag stuffing process.

[0009] The inventor discovered the following scientific phenomena through experiments and research:

[0010] 1. The inventors found that the load softening point temperature of the clay refractory and calcium silicate insulation material in the overhaul slag is between 1430℃ and 1450℃. Since the melting point of clay bricks is related to the structure of clay brick crystals, the greater the binding force between crystal particles, the more stable the structure. The oxides in the clay refractory are ionically bonded, and the chemical bonds of the silicate silicon oxygen backbone are close to covalent bonds. The silicon oxygen backbone and the external cations are ionically bonded. Therefore, the clay refractory and calcium silicate insulation board are processed to less than 1mm by using the mechanical force chemical reaction pretreatment technology. The waste refractory in the overhaul slag has chemical reaction activity in the high-temperature converter steel slag. Under the process conditions of high-temperature converter steel slag, the easily soluble fluoride and cyanide dissolved in the overhaul slag refractory can achieve harmless transformation. The principle of harmless transformation is as follows:

[0011] A: Dissolution of soluble fluorides in high-temperature converter slag:

[0012] 2Na3AlF6+6(O)→3Na2O+Al2O3+12F-

[0013] 2NaF+(O)→Na2O +2F -

[0014] B: The most basic harmless transformation of F ions dissolved in converter slag when solidifying:

[0015] Ca 2+ +2F - =CaF2

[0016] Mg 2+ +2F - =MgF2

[0017] C: Sodium cyanide, melting point (℃) 563.7, boiling point 1496℃, potassium cyanide, melting point 634.5℃. According to the basic principle of chemical reaction equilibrium shift, sodium cyanide and potassium cyanide are first melted in the process of steelmaking or slag treatment. Under the condition of oxygen atmosphere, the following reactions occur to achieve harmless transformation:

[0018] 2(NaCN)+5(FeO)→5Fe+2CO2↑+N2↑+Na2O

[0019] 2(KCN)+5(FeO)→5Fe+2CO2↑+N2↑+K2O

[0020] 2. The inventors found that the refractory components in the overhaul slag can undergo chemical reactions in both the liquid converter slag and the high-temperature solid converter slag, reducing the basicity of the slag and digesting the f-CaO and f-MgO in the converter slag, creating conditions for the direct resource utilization of the converter slag and ensuring the safety and stability of the resource utilization of the converter slag. The main chemical reactions are as follows:

[0021] nf-CaO+SiO2→nCaO·SiO2

[0022] nf-CaO+mAl2O3→nCaO·mAl2O3

[0023] f-MgO+Al2O3→MgO·Al2O3

[0024] 3. The hazardous waste of overhaul slag can be recycled in three forms: ① Add it to the converter from the high-level silo before the converter taps steel; ② Add it to the slag pot with the slag flow during the converter tapping process; ③ Add it to the slag pot filled with liquid slag from the converter. All of them can meet the requirements of online quenching and tempering of converter slag and harmless transformation of overhaul slag, and the implementation process is simple and easy, with strong operability.

[0025] The innovative features of the present invention are as follows:

[0026] 1. Based on the above scientific discoveries, the inventors proposed to use graphitized carbon blocks in overhaul slag as grinding aids and reducing agents after crushing, and mix them with waste refractory materials in overhaul slag and process them to less than 1 mm, and use them as resource-based tempering materials for converter steel slag, thus realizing the resource-based utilization of waste refractory materials in overhaul slag as tempering materials for converter steel slag;

[0027] 2. Use converter sludge as a catalyst for slag tempering reaction (TFe in converter sludge>30%, and the amount added is 5%-10% of the total amount of overhaul slag), mix it with the overhaul slag powder processed above, use a dry powder briquette machine to produce 30-50mm pellets, add it to the slag tank filled with converter liquid slag, the graphite carbon in the pellets reacts with the converter sludge to produce gas that can promote the explosion of the pellets, and the gas stirs the slag during the escape process, optimizing the kinetic conditions of the slag tempering reaction, and solving the problem of poor kinetic conditions in the reaction process of the slag quality thermal coupling technology;

[0028] 3. Use a crane to lift the converter slag pot with overhaul slag added, and pour the high-temperature converter slag in the slag pot into another empty slag pot to improve the reaction interface between the converter slag and the overhaul slag, so as to realize the rapid online quenching and tempering reaction;

[0029] 4. The overhaul slag is used to optimize the mineral structure of converter slag and realize the harmless transformation of hazardous waste from electrolytic aluminum. The physical heat of converter slag is converted into chemical heat and used in the harmless transformation process of overhaul slag, which reduces the overall carbon emissions of the metallurgical industry, optimizes the energy consumption of the metallurgical industry, and reduces the overall carbon emissions of the metallurgical industry.

[0030] 5. The process method of the present invention can be widely used in hot slag splashing, hot slag stuffing and drum slag treatment processes, has strong process adaptability and strong operability.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1. The present invention can utilize converter slag to treat overhaul slag on a large scale, with low treatment cost, complete harmless transformation of overhaul slag, and no new solid waste generated during the treatment process. The treated overhaul slag is utilized as a component of converter slag for resource utilization, and its safety is better than the existing pyrometallurgical and hydrometallurgical treatment processes;

[0033] 2. Since steel slag is overburned silicate cement clinker, the harmless result of the present invention is similar to that of cement kiln treatment, but the treatment cost is equivalent to 30% of that of cement kiln treatment, which has great economic advantages in terms of treatment cost;

[0034] 3. The process method of the present invention not only realizes the harmless transformation of overhaul slag, but also optimizes the performance of converter slag, reduces f-CaO and f-MgO in the slag, and ensures the safety of converter slag resource utilization. The process method is conducive to the promotion and implementation of steel mills;

[0035] 4. The process of the present invention realizes the transfer of physical heat of converter slag to chemical reaction heat, saves energy consumption in the pyrometallurgical treatment process of overhaul slag under the same conditions, reduces the overall carbon emissions of the metallurgical industry, and is conducive to the integrated development of the metallurgical industry;

[0036] 5. By utilizing the process of the present invention, China can fully utilize the overhaul slag produced by China's electrolytic aluminum industry by using the steelmaking slag of China Baowu Group every year, which will bring huge environmental and economic benefits. Implementation

[0037] The embodiment of the present invention is described by taking a hot stuffing production line of China Baowu Group with an annual output of 600,000 tons of steel slag as an example.

[0038] 1. First, the overhaul slag produced by the electrolytic aluminum enterprises in Wucaiwan area of ​​Xinjiang is transported to the steel slag plant, and the carbon blocks and refractory materials in the overhaul slag are sorted and separated and then stored in different categories;

[0039] 2. Use a chain crusher to crush the carbon blocks to less than 5 cm, mix the carbon blocks and refractory materials in a mass percentage of 20:80, and use a rod mill and a Raymond mill to process the mixture to less than 1 mm, and transport it to the pelletizing production line as overhaul slag powder for standby use;

[0040] 3. Pull the sludge from the running furnace steel plant to the pelletizing production line for standby use;

[0041] 4. Add converter sludge as a binder to the overhaul slag powder material, the amount of converter sludge added is 5% to 10% of the mass of the overhaul slag powder material, use a high-pressure dry powder pelletizing machine to press the powder material into pellets with a diameter of 30 to 50 mm, and transport them to the converter production line and hot smoldering slag production line for standby use;

[0042] 5. When converter smelting is near the end, add pellets before slag pouring and steel tapping in the converter. The amount added is 3-5 kg ​​per ton of steel as a defoaming agent for converter foam slag.

[0043] 6. When pouring the slag before tapping the converter, the pellets can also be used as slag pressing and defoaming agents for the slag pot. They can be added to the slag pot along with the converter slag flow. The amount added is 250kg to 500kg per ton of slag.

[0044] 7. When the above two steps 5 and 6 are inconvenient to use, after the slag discharge of the converter is completed, the slag pot containing the liquid slag of the converter is transported to the slag plant, and the pellets are added to the slag pot containing the liquid slag of the converter. The amount added is 100-250kg per ton of slag. After adding, the slag pot is allowed to stand for about 30 minutes. The converter slag in the slag pot is poured into another empty slag pot. After standing for 60 minutes, it can be processed according to the normal hot slag pouring or hot slag stuffing process.

Claims

1. A method for co-processing electrolytic aluminum overhaul slag with converter steel slag, characterized in that Follow these steps: 1) First, the overhaul slag produced by the electrolytic aluminum enterprise is transported to the steel slag plant, and the carbon blocks and refractory materials in the overhaul slag are sorted and separated and then stored in different categories; 2) Use a chain crusher to crush the carbon blocks to less than 5 cm, mix the carbon blocks and the refractory materials in a mass percentage of 20:80, and use a rod mill and a Raymond mill to process the mixture to less than 1 mm, and transport it to the pelletizing production line as overhaul slag powder for standby use; 3) Pull the sludge from the operating furnace steel plant to the pelletizing production line for standby use; 4) Add converter sludge as a binder to the overhaul slag powder material, the amount of converter sludge added is 5% to 10% of the mass of the overhaul slag powder material, use a high-pressure dry powder pelletizing machine to press the powder material into pellets with a diameter of 30 to 50 mm, and transport them to the converter production line and hot smoldering slag production line for standby use; 5) When converter smelting is close to the end, the above pellets are added before the converter slag is discharged, and the amount added is 3-5 kg ​​per ton of steel, and used as a defoaming agent for the converter foam slag; or, when the converter is discharged before the converter is discharged, the above pellets are used as a slag pressing defoaming agent for the slag pot, and are added to the slag pot along with the converter slag flow, and the amount added is 250 kg-500 kg per ton of slag; 6) When the two processes in step 5 are inconvenient to use, after the slag discharge of the converter is completed, the slag pot containing the liquid slag of the converter is transported to the slag plant, and the above-mentioned pellets are added to the slag pot containing the liquid slag of the converter, and the added amount is 100-250kg per ton of slag. After adding, the slag pot is allowed to stand for 30 minutes, and the converter slag in the slag pot is poured into another empty slag pot. After standing for 60 minutes, it can be processed according to the normal hot slag pouring or hot slag stuffing process.