Carbon steel electric furnace dust self-circulation treatment process

Abstract

The present application is a process method for making the electric furnace dust into a ball, then burning into a balling agent in the electric furnace combustion chamber, and supplying the electric furnace through the high-position material bin feeding mode for self-circulation use, and finally smelting the dust into zinc-rich powder by using the zinc enrichment effect. The method uses the electric furnace combustion chamber to burn, improves the electric furnace heat energy utilization rate, solves the environmental protection requirement of "solid waste not leaving the factory" of the electric furnace dust, realizes the resource transformation of the dust, and improves the safety and economy of the dust in the electric furnace metallurgical process.

Description

Technical Field

[0001] This invention relates to the field of metallurgical engineering, and in particular to a self-circulating treatment process for dust from carbon steel electric furnaces. Background Technology

[0002] With the increasing environmental protection requirements imposed by national ministries on enterprises, the steel industry, especially Taiyuan Iron & Steel Group (TISCO), a city steel plant, has made a clear environmental commitment to "no solid waste leaving the plant." Internally, it has mandated the full utilization of solid waste, requiring "no external discharge, no spillage, and no leakage." This has led to the dilemma of whether electric arc furnace dust (EAF) ash must be internally recycled or processed into valuable raw materials for resale. The original treatment method involved the steel plant funding the transportation of EAF dust to the sintering process in the ironmaking plant, where it was mixed into the sintering material at a low proportion for recycling. This process increased costs for the steel plant and caused pollution during transportation, including spillage and runoff. Furthermore, mixing the dust into the sintering material affected the permeability of the sinter, leading to decreased strength of subsequent blast furnace aggregates, erosion of refractory bricks, formation of furnace nodules, and damage to tuyeres. This has repeatedly caused fluctuations in blast furnace production, resulting in low willingness among ironmaking plants to use the ash. Under these circumstances, the steel plant, based on its own conditions, researched a treatment process that allows for self-production and utilization, turning waste into valuable resources. The initial cold-pressed pellets, due to their water absorption and tendency to pulverize, posed safety hazards during use, including excessive boiling within the furnace and overhead crane lifting. After numerous studies and improvements, a more mature and safer self-circulating treatment model was developed: "electric furnace combustion chamber for sintering pellets – high-level silo for power furnace recycling – zinc-rich ash for external sale."

[0003] This invention provides a production process for the self-circulation treatment of dust from carbon steel electric furnaces. This process is low-cost, environmentally friendly, highly efficient, and has a high safety factor, ultimately achieving the goal of transforming electric furnace dust into zinc-rich powder resources. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a self-circulating process for treating dust from carbon steel electric furnaces.

[0005] The objective of this invention is achieved as follows: A self-circulating process for treating carbon steel electric arc furnace dust includes the following steps: Step 1: Combustion chamber ash treatment: The combustion chamber ash of the electric arc furnace is screened. Blocks ≥10mm are directly transferred to the scrap steel pool, prepared by a disk, and then loaded into the electric arc furnace for recycling. Powder <10mm is transferred to the electrostatic precipitator ash for pelletizing. Step 2: Dust removal ash treatment: Pelletizing: Bentonite is added to the electric arc furnace electrostatic precipitator ash at a ratio of 8%-10% by weight of the mixture. After stirring evenly, the mixture is cold-pressed into pellets using a roller press. Sintering: The pellets are then transferred to the electric arc furnace combustion chamber. In the combustion chamber of an electric furnace, at a high temperature of 1300℃-1500℃ and a reducing atmosphere, the compressed pellets are sintered into pellet slagging agents. The pellets are then transferred to a cooling zone and cooled to room temperature. After sieving, the pellets are carried to a high-level silo for later use. The pellet slagging agent made from dust collector ash has a moisture content of less than 0.5%, and after being carried to the high-level silo for 24 hours, the powder content of <5mm is less than 10%. Step 3: Use of slagging agent: The pellet slagging agent is added to the electric furnace for recycling. Step 4: Zinc enrichment of dust collector ash: After the zinc content in the dust collector ash is enriched to 20%-30%, the zinc-rich ash is sold externally.

[0006] In step two, the sphere making process specifically involves pressing the sphere into an elliptical sphere with a diameter of approximately 55mm-55mm.

[0007] In step three, the method for recycling the pellet slag-forming agent in the electric furnace is as follows: After the scrap steel is loaded into the electric furnace, the pellet slag-forming agent is added at a rate of 5 kg / t-6 kg / t, along with 8 kg / t-9 kg / t of lime, to quickly melt into initial slag; during the "re-drying" of the slag in the middle stage of smelting, it is added at a rate of 3 kg / t-5 kg / t to form intermediate slag; in the middle and late stages of smelting, it is added at a rate of 5 kg / t-6 kg / t along with an equal amount of lime, and smelting is completed.

[0008] The beneficial effects of this invention are: 1. Dust collector ash is transformed from solid hazardous waste into raw material resources. Before the implementation of this invention, dust collector ash contained small amounts of harmful elements such as zinc and was managed and treated as hazardous waste. After the implementation of this invention, hazardous waste electric furnace dust collector ash is ultimately transformed into zinc-rich raw material for rotary hearth furnaces, realizing the resource utilization of solid waste.

[0009] 2. Outstanding environmental benefits. Before the implementation of this invention, dust collector ash was transported in powder form, frequently causing spillage, scattering, and dust pollution. Some outsourced dust collector ash was treated and then landfilled, increasing the environmental burden. After the implementation of this invention, all dust collector ash is reused as a metallurgical raw material through industrial self-circulation. The amount of ash discharged during the steelmaking process is directly reduced to zero.

[0010] 3. Significant Economic Benefits. Before the implementation of this invention, there were two solid waste treatment models for dust collector ash. First, outsourcing the treatment at a self-paid cost, which was costly. Second, sending the ash to the sintering plant for a fee, adding a low proportion of sintered ore, which repeatedly caused fluctuations in blast furnace production and quality, creating a prominent point of contention regarding solid waste treatment within the company. After the implementation of this invention, the dust collector ash is self-circulated, improving slag formation and dephosphorization efficiency, reducing steel material consumption by 2.16 kg / t, reducing slag-forming lime consumption by 1.3 kg / t, and reducing solid waste treatment costs by 5.79 yuan / ton. Additionally, it generates revenue from the sale of zinc-rich ash.

[0011] 4. Safe and controllable use. The slagging agent for calcined pellets has a moisture content of less than 0.5%, which can effectively prevent boiling in the electric furnace caused by damp pellets. The calcined pellets have high strength and low pulverization rate, and can be used directly through the high-level silo system, avoiding burns and lifting injuries caused by overhead crane lifting. Attached Figure Description

[0012] The present invention will now be further described with reference to the accompanying drawings.

[0013] Figure 1 This is a flowchart of the present invention. Implementation

[0014] The technical concept of this invention is as follows: The furnace gas in the combustion chamber, under the influence of CO and a high temperature of 1300℃, forms a reducing atmosphere, which can reduce the iron oxide on the surface of the dust collector ash in the combustion chamber to elemental iron. We can utilize this high-temperature environment and reducing power to form briquettes by adding a binder to the dust collector ash, then returning it to the combustion chamber for firing to obtain dry sintered briquettes with a particle size that meets the requirements of the silo and has high surface strength. The particle size of the sintered briquettes can be controlled and adjusted by the briquette press. High-temperature firing reduces the moisture content of the briquettes to below 0.5%, ensuring safe and reliable addition of briquettes to molten steel. By controlling the firing time, the strength of the sintered layer on the briquette surface is improved, and the pulverization rate is reduced to meet the requirements for use in upper-level silos, avoiding the need for hoisting dust collector ash (briquettes) and further improving the safety factor during use. By screening the settling ash in the combustion chamber, the dust collection system is fully covered by ash without affecting the briquette pressing operation. The briquette making, transfer, baking, and feeding of dust collector ash are all carried out within the plant, and all work areas are equipped with dust collection systems, making the processing flow environmentally friendly and controllable. The sintered pellets made from dust collector ash contain a large amount of iron oxide and a small amount of carbon powder. When added in appropriate amounts to the electric furnace during smelting, they can rapidly increase the FeO content in the slag and promote the formation of foamy slag, thereby improving the slag-forming efficiency and dephosphorization efficiency of the electric furnace. They can be recycled as a slag-forming agent. Zinc in the dust collector ash is enriched during the electric furnace's circulating treatment process. The zinc content in the dust collector ash is periodically tested, and once it meets the standards for rotary hearth furnace raw materials, the dust collector ash is sold as zinc-rich powder.

[0015] This invention classifies electric arc furnace (EAF) dust into two categories for treatment: ash particles settled in the combustion chamber are returned to the scrap steel pool for recycling, while the EAF dust is used for pelletizing. The EAF dust is mixed with 8-10% bentonite, cold-pressed into pellets, and sintered using the heat from the combustion chamber. The slagging agent produced from the pelletized dust is added to the EAF for recycling, accelerating the formation of foamy slag and improving the dephosphorization effect of the EAF. The slagging agent used to make pellets from the dust has a moisture content of less than 0.5%, and after being carried into the high-level silo for 24 hours, the powder content <5mm is less than 10%. Through enrichment, the zinc content in the dust is recycled and enriched to ≥20%, after which zinc-rich dust is sold externally.

[0016] This invention transforms dust collector ash from solid hazardous waste into a raw material resource. It utilizes an electric furnace's self-circulating system for internal recycling or processes it into valuable raw materials for external sale. The heat from the electric furnace's combustion chamber is used for firing, reducing production costs. After implementing this invention, the self-circulation of dust collector ash improves slag formation and dephosphorization efficiency, reduces steelmaking material consumption by 2.16 kg / t, and reduces slag-forming lime consumption by 1.3 kg / t. This invention effectively prevents boiling within the electric furnace caused by damp pellets; the pellets directly enter the high-level silo, avoiding burns and lifting injuries caused by traditional overhead crane hoisting methods, thus significantly improving the safety factor of steelmaking.

[0017] The process for self-circulating electric furnace dust collection ash treatment of this invention includes the following steps: 1. Raw material conditions: 1.1 The ash extracted by the electric furnace dust collection system, part of which settles in the combustion chamber and part of which enters the dust collection ash. 1.2 The main components of the dust collection ash are as follows: TFe 46.95%, CaO 12.03%, SiO2 4.45%, MgO 2.81%, C 0.96%, Al2O3 0.91%, P 0.03%, S 0.109%.

[0018] Combustion chamber ash treatment: The combustion chamber ash of the electric furnace is screened. Blocks ≥10mm are directly transferred to the scrap steel pool, prepared by a disk, and then loaded into the electric furnace for use. Powdered materials <10mm are transferred to the electrostatic precipitator ash treatment facility.

[0019] 3. Dust Removal Ash Treatment: 3.1 Pelletizing: Add 8%-10% bentonite to the electrostatic precipitator dust, stir evenly, and then use a roller pelletizer to pelletize the granules into elliptical spheres with a diameter of approximately 50mm. 3.2 Sintering: Transfer the pellets to the electric furnace combustion chamber, and sinter them into pellet slag-forming agents using the high temperature of 1300℃ and the reducing atmosphere of the combustion chamber. 3.3 Use of Slag-Forming Agent: Transfer the pellets to the cooling zone to air-cool to room temperature, pass them through a 35mm sieve, and then carry them to the high-level silo for use in the electric furnace for slag formation. After the scrap steel is loaded into the electric furnace, 5 kg / t of pelletizing slag-forming agent is added to the furnace along with 8 kg / t of lime to quickly melt it into initial slag. During the "re-drying" of the slag in the middle stage of smelting, 3 kg / t is added to the furnace to form intermediate slag, which increases the iron oxide content of the slag and adjusts the slag activity. In the middle and late stages of smelting, 5 kg / t is added to the furnace along with an equal amount of 5 kg / t of lime to further improve the oxidizing properties of the slag and increase the carbon-oxygen reaction efficiency.

[0020] 4. Zinc enrichment in dust collector ash. During the recycling process, the zinc content of the dust collector ash increases. Once the zinc content reaches 20%, it is sold as raw material for rotary hearth furnaces.

[0021] The specific implementation of the method of the present invention will be described in detail below with reference to the embodiments, but the specific implementation of the present invention is not limited to the following embodiments.

[0022] This embodiment uses an EBT electric furnace, equipped with electrodes, a cluster oxygen lance, an elevated silo system, a combustion chamber, and an electrostatic precipitator system. The electrostatic precipitator ash chamber is equipped with a mixer and a roller briquetting machine, while the dust removal chamber outside the combustion chamber is equipped with a screening machine. A 20-ton electromagnetic chuck is installed on the overhead crane above the scrap steel pool. Example 1

[0023] 1. Use a loader to load the ash from the electric furnace combustion chamber into a screening machine to screen out the powder.

[0024] 2. Mix the combustion chamber ash powder with bentonite in a 9:1 ratio, stir evenly, and then use a roller briquetting machine to press it into an oval briquetting ball with a diameter of about 50mm.

[0025] 3. Use a loader to transfer the briquettes to the combustion chamber and spread them out to a thickness of no more than 100mm.

[0026] 4. Firing in the combustion chamber for 1 day, then cooling to room temperature before sieving.

[0027] 5. Pelletizing materials with a diameter ≥ 35mm are directly fed into the elevated silo system. Particles with a diameter ≥ 10mm are transferred to the scrap steel pool. Powder materials with a diameter < 10mm are transferred to the electrostatic precipitator room.

[0028] 6. After the scrap steel is loaded into the electric furnace, immediately add 5 kg / t of pellet slag-forming agent into the furnace, and at the same time add 8 kg / t of lime to ensure that the initial slag melts into slag quickly, reduce splashing, improve dephosphorization efficiency and steel yield.

[0029] 7. If the slag is found to be "drying back" during the middle stage of smelting, immediately add 3 kg / t into the furnace to increase the iron oxide content of the slag, adjust the slag activity, and reduce splashing.

[0030] 8. In the middle and late stages of smelting, add 5 kg / t of lime to the furnace and mix with 5 kg / t of lime to further improve the oxidizing properties of the slag, increase the carbon-oxygen reaction rate, and improve smelting efficiency. Example 2

[0031] 1. In the electrostatic precipitator dust chamber, mix bentonite and dust at a mass ratio of 1:9, load them into a mixer and stir evenly, then directly use a roller briquetting machine to press them into oval briquettes with a diameter of about 50mm.

[0032] 2. Use a loader to transfer the briquettes to the combustion chamber and spread them out to a thickness of no more than 100mm.

[0033] 3. Firing in the combustion chamber for 1 day, then cooling to room temperature before sieving.

[0034] 4. Pelletizing materials with a diameter ≥ 35mm are directly fed into the elevated silo system. Particles with a diameter ≥ 10mm are transferred to the scrap steel pool. Powder materials with a diameter < 10mm are transferred to the electrostatic precipitator room.

[0035] 5. After the scrap steel is loaded into the electric furnace, immediately add 5 kg / t of pellet slag-forming agent into the furnace, and at the same time add 8 kg / t of lime to ensure that the initial slag melts into slag quickly, reduce splashing, improve dephosphorization efficiency and steel yield.

[0036] 6. When the slag is severely "dryed" during the middle stage of smelting, add 5 kg / t into the furnace to increase the iron oxide content of the slag, adjust the slag activity, and reduce splashing.

[0037] 7. In the middle and late stages of smelting, add 5 kg / t of lime to the furnace and mix with 5 kg / t of lime to further improve the oxidizing properties of the slag, increase the carbon-oxygen reaction rate, and improve smelting efficiency. Example 3

[0038] 1. Use a loader to load the ash from the electric furnace combustion chamber into a screening machine, screen out lumps with a diameter ≥10mm, and transfer them directly to the scrap steel pool. Transfer the powdered material to the electrostatic precipitator ash room.

[0039] 2. Use an electric disk to suck the block material into the scrap steel basket, and load it into the electric furnace for smelting along with the scrap steel.

[0040] 3. In the electrostatic precipitator ash chamber, the combustion chamber ash and bentonite are mixed in a ratio of 1:4 to form a binder. Then, the binder and dust collector ash are mixed in a mass ratio of 1:9 and put into a mixer. After being mixed evenly, the mixture is directly pressed into elliptical briquettes with a diameter of about 50mm using a roller briquetting machine.

[0041] 4. Use a loader to transfer the briquettes to the combustion chamber and spread them out to a thickness of no more than 100mm.

[0042] 5. Firing in the combustion chamber for 1 day, then cooling to room temperature before sieving.

[0043] 6. Particles and pellets with a diameter ≥ 10mm shall be transferred to the scrap steel pool. Powder with a diameter < 10mm shall be transferred to the electrostatic precipitator room.

[0044] 7. Using an electric disk, add the pellets to the scrap steel basket at a rate of 5 kg / t, and add them into the furnace along with the scrap steel charging operation.

[0045] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A self-circulating process for treating dust from carbon steel electric furnaces, characterized in that: Includes the following steps: Step 1: Combustion chamber ash treatment: Screen the ash from the electric furnace combustion chamber. Pieces larger than or equal to 10mm are directly transferred to the scrap steel pool, prepared by a disk, and then loaded into the electric furnace for recycling. Powder smaller than 10mm is transferred to the electrostatic precipitator ash for pelletizing. Step Two: Dust Removal Ash Treatment: Pelletizing: Bentonite is added to the electric furnace electrostatic precipitator dust at a ratio of 8%-10% by weight of the mixture. After thorough mixing, the mixture is cold-pressed into pellets using a roller press. Sintering: The pellets are transferred to the electric furnace combustion chamber, where they are sintered into pellet slag-forming agents using the high temperature (1300℃-1500℃) and reducing atmosphere. The pellets are then transferred to a cooling zone and cooled to room temperature. After sieving, the pellets are carried to a high-level silo for later use. The pellet slag-forming agent made from the dust removal ash has a moisture content of less than 0.5%, and after 24 hours in the high-level silo, the powder content of pellets smaller than 5mm is less than 10%. Step 3: Use of slagging agent: The pelletizing slagging agent is added to the electric furnace for recycling; Step 4: Zinc enrichment in dust collector ash: The zinc content in the dust collector ash is recycled and enriched to 20%-30%; In step three, the method for recycling the pellet slag-forming agent in the electric furnace is as follows: After the scrap steel is loaded into the electric furnace, the pellet slag-forming agent is added at a rate of 5 kg / t-6 kg / t, along with 8 kg / t-9 kg / t of lime, to quickly melt into initial slag; during the middle stage of smelting, when the slag is being dried, it is added to the furnace at a rate of 3 kg / t-5 kg / t to form intermediate slag; during the middle and late stages of smelting, it is added to the furnace at a rate of 5 kg / t-6 kg / t, along with an equal amount of lime, and smelting is completed.

2. The self-circulation treatment process for dust from carbon steel electric furnaces according to claim 1, characterized in that: In step two, the sphere is specifically made into an elliptical sphere with a diameter of 50mm.

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