A method for improving the yield of metal raw materials in an electric arc furnace

Abstract

This invention provides a method for improving the yield of metal raw materials in an electric arc furnace, comprising the following steps: The furnace charge is added to the electric arc furnace in batches. After each batch is added, the smelting process of a single batch is divided into a slag-forming stage and a melting and heating stage. When the smelting process of a single batch is in the slag-forming stage, oxygen is supplied using the furnace door oxygen lance and carbon is supplied using a carbon lance, while the main oxygen mode of the furnace wall oxygen lance is turned off. When the smelting process of a single batch is in the melting and heating stage, the main oxygen of the furnace wall oxygen lance and the furnace door oxygen lance are used in tandem to enter the oxygen supply mode, while the carbon powder supply of the carbon lance is increased until the smelting of that batch is completed. This invention improves the oxygen supply and carbon powder injection operations in the electric arc furnace steelmaking process, thereby increasing the yield of metal raw materials. This method, while meeting the requirements of smelting speed and molten steel quality, can significantly reduce molten steel loss during the smelting process, and its scrap steel recovery rate can reach 93.9%.

Description

Technical Field

[0001] This invention belongs to the field of electric arc furnace steelmaking technology, specifically relating to a method for improving the yield of metal raw materials in an electric arc furnace. Background Technology

[0002] Electric arc furnace (EAF) short-process steelmaking uses scrap steel as raw material to smelt steel, with scrap steel accounting for 70-80% of the total cost. Therefore, saving on scrap steel costs is crucial for increasing the profit per ton of steel produced by EAF. Based on current profit per ton data for both blast furnace-converter long-process and EAF short-process steelmaking processes, the cost of EAF steelmaking using scrap steel is higher than that of blast furnace-converter steelmaking using iron ore and coke. This makes EAF steelmaking less cost-effective than converter steelmaking, thus reducing the cost of EAF steelmaking has become a key concern for enterprises.

[0003] For electric arc furnace steelmaking, increasing the yield of metal raw materials can reduce the cost per ton of steel. For example, with a capacity of 1 million tons, if the yield of metal raw materials increases by 1%, the cost per ton of steel can be reduced by 35 yuan, resulting in an annual profit of 35 million yuan. Therefore, how to develop a reasonable smelting process to improve the yield of metal raw materials in the electric arc furnace smelting process and thus bring economic benefits to electric arc furnace steelmaking enterprises has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the yield of metal raw materials in an electric arc furnace, which can at least solve some of the defects existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for improving the yield of metal raw materials in an electric arc furnace includes the following steps:

[0007] The furnace charge is added to the electric arc furnace in batches. After each batch of furnace charge is added, the smelting process of a single batch of furnace charge is divided into a slag-forming stage and a melting and heating stage.

[0008] When a single batch of furnace charge is in the slag-forming stage of the smelting process, oxygen is supplied by the furnace door oxygen lance and carbon is supplied by the carbon lance, while the main oxygen mode of the furnace wall oxygen lance is turned off.

[0009] When a single batch of furnace charge is in the melting and heating stage of the smelting process, the main oxygen lance of the furnace wall oxygen lance and the oxygen lance of the furnace door are used in synergy to enter the oxygen supply mode, while the carbon powder supply of the carbon lance is increased until the smelting of that batch is completed.

[0010] Furthermore, the furnace charge consists of 5-10 kg of carbon balls added per ton of scrap steel.

[0011] Furthermore, the dividing point between the slag-forming stage and the melting and heating stage is the designed power consumption per ton of steel, and / or the moment when the temperature of the topmost furnace charge reaches the designed temperature after the charge is added to the electric arc furnace.

[0012] Furthermore, the dividing point between the slag-forming stage and the melting and heating stage is when the power consumption per ton of steel is 150-180 kWh / t, and / or the temperature of the topmost furnace charge after the charge is added to the electric arc furnace is not lower than 600°C.

[0013] Furthermore, during the slagging stage of the single batch of furnace charge, the oxygen supply flow rate is 4000–5000 Nm³. 3 / h, toner flow rate is 70~90kg / min.

[0014] Furthermore, during the melting and heating stage of the single batch of furnace charge, the oxygen supply flow rate is 7000–8000 Nm³. 3 / h, toner flow rate is 90~110kg / min.

[0015] Furthermore, the average oxygen supply per ton of furnace charge in a single batch during the entire smelting process is 22–28 Nm³. 3 .

[0016] Furthermore, the average carbon supply per ton of furnace charge in a single batch during the entire smelting process is 15-25 kg.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The method for improving the yield of metal raw materials in electric arc furnaces provided by this invention comprehensively considers the relationship between the costs of scrap steel, electricity, etc. in the overall cost of steelmaking. By improving the oxygen supply and carbon powder injection operation in the electric arc furnace steelmaking process, the method achieves the goal of improving the yield of metal raw materials. While meeting the requirements of smelting speed and molten steel quality, this method can significantly reduce the loss of molten steel in the smelting process, and its scrap steel yield can reach 93.9%. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention addresses the high cost of existing electric arc furnace (EAF) smelting. From the perspective of cost savings in EAF steelmaking, it comprehensively considers the relationship between scrap steel, electricity, and other costs in the overall steelmaking cost. A comprehensive analysis of electricity and raw material costs is conducted. Currently, the average electricity consumption per ton of steel in a vertical shaft preheating electric furnace is 300 kWh / t, the average electricity price is 0.6 yuan / kWh, and the off-peak electricity price is 0.3 yuan / kWh. The average price of scrap steel is 3000-3500 yuan / t. If the metal raw material yield can be increased by 1%, the raw material cost per ton of steel can be reduced by nearly 35 yuan. The increase in electricity costs due to the increased metal raw material yield is still far less than the savings in raw material costs. Therefore, improving the metal raw material yield in the EAF to save steelmaking costs has economic advantages.

[0021] This embodiment provides a method for improving the yield of metal raw materials in an electric arc furnace, mainly by adopting a suitable oxygen supply and carbon injection system to reduce the loss of molten steel while ensuring the requirements of the smelting conditions. The specific process includes the following steps:

[0022] The furnace charge is added to the electric arc furnace in batches. After each batch is added, the smelting process for that batch is divided into a slag-forming stage and a melting and heating stage. During the slag-forming stage, the scrap steel temperature inside the furnace is relatively low, and the slag-forming process mainly focuses on creating foamy slag. Oxygen is supplied only through the furnace door oxygen lance, with carbon supplied in conjunction with the carbon lance. The main oxygen mode of the furnace wall oxygen lance is turned off to prevent direct oxidation of the scrap steel. During the melting and heating stage, the primary function is to rapidly melt the scrap steel and raise the temperature. Therefore, the main oxygen supply from the furnace wall oxygen lance and the furnace door oxygen lance are used in tandem, while the carbon powder supply from the carbon lance is increased until the smelting of that batch is complete.

[0023] Specifically, the present invention is applicable to vertical shaft preheating electric arc furnaces and adopts flat molten pool smelting technology based on large-scale steel retention. The furnace charge consists of 5-10 kg of carbon balls per ton of scrap steel, without the need to add pig iron.

[0024] The optimized technical solution defines the boundary between the slag-forming stage and the melting and heating stage as the designed power consumption per ton of steel and / or the moment when the temperature of the topmost charge after the charge is added to the electric arc furnace reaches the designed temperature. Specifically, in the electric arc furnace steelmaking scheme of this embodiment, the boundary between the slag-forming stage and the melting and heating stage is the moment when the power consumption per ton of steel is 150-180 kWh / t. This moment mainly depends on the temperature of the scrap steel in the furnace after it is added to the molten pool. That is, the boundary between the slag-forming stage and the melting and heating stage depends on the temperature of the scrap steel in the furnace after it is added to the molten pool. When the temperature of the topmost charge after the charge is added to the electric arc furnace is not lower than 600°C, the furnace wall oxygen lance can adopt the main oxygen mode. The main oxygen plays a role in cutting the scrap steel and uniformizing the molten pool, thereby achieving rapid melting of the scrap steel. Optimizedly, as smelting progresses, when the power consumption per ton of steel reaches 150-180 kWh / t, the furnace wall oxygen lance adopts the main oxygen mode, and the flow rate of the main oxygen in each furnace wall oxygen lance is controlled at 20-30 m³ / t. 3 / min;

[0025] In this embodiment, based on the requirements of scrap steel raw material composition and foamed slag, the oxygen blowing and carbon injection flow rates at each stage of the smelting process are controlled to ensure that the molten steel is not over-oxidized. Specifically, for the oxygen blowing process, during the slag-forming stage, due to the low temperature, the scrap steel is not completely melted, and the molten pool does not have sufficient carbon-oxygen reaction. If an excessively high oxygen supply intensity is used, it will lead to low oxygen utilization and have little effect on improving productivity. Therefore, a lower oxygen supply intensity should be used during the slag-forming stage. As smelting progresses, the molten pool becomes larger, the proportion of unmelted scrap steel is smaller, and there can be sufficient carbon-oxygen reaction in the molten pool. Therefore, the oxygen blowing intensity can be gradually increased. Thus, in this embodiment, the single batch of furnace charge is 4000-5000 Nm³ during the slag-forming stage. 3 The oxygen supply is provided at a flow rate of 7000-8000 Nm³ / h, while during the melting and heating stage, the oxygen supply flow rate is increased to 7000-8000 Nm³ / h. 3 / h. For the carbon injection process, the slag-forming stage is mainly focused on slag formation. A large amount of carbon powder is injected to support the carbon-oxygen reaction in the furnace and promote slag foaming. In the melting and heating stage, a large amount of carbon powder is needed to ensure that the oxidized scrap steel is fully reduced and to maintain a constant amount of foamy slag, thereby achieving arc submersion and improving heating efficiency. Therefore, in this embodiment, the carbon powder flow rate of the single batch of furnace charge is 70-90 kg / min during the slag-forming stage, while the carbon powder flow rate of the single batch of furnace charge is increased to 90-110 kg / min during the melting and heating stage.

[0026] Using the oxygen supply and carbon injection system of this embodiment, under the basic condition of ensuring foamy slag, the average oxygen supply per ton of furnace charge during the entire electric arc furnace smelting process can be increased from the traditional 32-35 mg / L. 3 Reduced to 22-28 Nm 3 Meanwhile, the average carbon supply per ton of furnace charge is 15-25 kg.

[0027] Preferably, during the slag-forming stage, the flux is 4400–4800 Nm 3 Oxygen is supplied at a flow rate of 80-90 kg / min, and carbon is supplied at a flow rate of 7200-7600 Nm³ / h during the melting and heating stage. 3 Oxygen is supplied at a flow rate of 100-110 kg / min, and carbon is supplied at a flow rate of 100-110 kg / min. Under this oxygen supply and carbon injection system, the oxygen consumption per ton of steel during electric furnace smelting is 24-26 Nm³. 3 / t, the carbon powder consumption per ton of steel is 18-22 kg / min.

[0028] The oxygen supply and carbon injection systems in the method for improving the yield of metal raw materials in an electric arc furnace according to the present invention are illustrated below through specific embodiments.

[0029] Example 1:

[0030] A 120t vertical shaft electric arc furnace is used to smelt all scrap steel. The furnace is fed in batches of 4 baskets. The smelting process of the first 3 baskets is basically the same. The last basket requires the molten steel to be heated, and the smelting time is longer. This embodiment uses the oxygen blowing and carbon injection system of the first 3 baskets for calculation and explanation. The smelting system of each stage of a single basket is shown in Table 1.

[0031] Table 1. Smelting System of Electric Furnace at Each Stage (Single Basket)

[0032]

[0033] After smelting, the calculated power consumption per ton of steel is 320 kWh / t, and the oxygen consumption is 25 Nm³. 3 / t steel, the amount of carbon powder injected is 20kg / t steel, and the scrap steel recovery rate reaches 93.9%.

[0034] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method for improving the yield of metal raw materials in an electric arc furnace, characterized in that, The process includes the following: The furnace charge is added to the electric arc furnace in batches. After each batch of furnace charge is added, the smelting process of a single batch of furnace charge is divided into a slag-forming stage and a melting and heating stage. When a single batch of furnace charge is in the slag-forming stage of the smelting process, oxygen is supplied by the furnace door oxygen lance and carbon is supplied by the carbon lance, while the main oxygen mode of the furnace wall oxygen lance is turned off. When a single batch of furnace charge is in the melting and heating stage of the smelting process, the main oxygen of the furnace wall oxygen lance and the oxygen lance of the furnace door are used in synergy to enter the oxygen supply mode, while the carbon powder supply of the carbon lance is increased until the smelting of that batch is completed. The dividing point between the slag-forming stage and the melting and heating stage is when the power consumption per ton of steel is 150-180 kWh / t, and / or when the temperature of the topmost furnace charge after the charge is added to the electric arc furnace is not lower than 600°C.

2. The method for improving the yield of metal raw materials in an electric arc furnace as described in claim 1, characterized in that: The furnace charge consists of 5-10 kg of carbon balls per ton of scrap steel.

3. The method for improving the yield of metal raw materials in an electric arc furnace as described in claim 1, characterized in that: During the slagging stage of the single batch of furnace charge, the oxygen supply flow rate is 4000–5000 Nm³. 3 / h, toner flow rate is 70~90kg / min.

4. The method for improving the yield of metal raw materials in an electric arc furnace as described in claim 3, characterized in that: During the melting and heating stage of the single batch of furnace charge, the oxygen supply flow rate is 7000–8000 Nm³. 3 / h, toner flow rate is 90~110kg / min.

5. The method for improving the yield of metal raw materials in an electric arc furnace as described in claim 4, characterized in that: The average oxygen supply per ton of charge in a single batch during the entire smelting process is 22–28 Nm³. 3 .

6. The method for improving the yield of metal raw materials in an electric arc furnace as described in claim 4, characterized in that: The average carbon supply per ton of furnace charge in a single batch during the entire smelting process is 15-25 kg.

Images