Method for smelting cold-state direct reduced iron in Consteel electric furnace

Abstract

The invention discloses a smelting method of cold-state direct reduced iron in a Consteel electric furnace, and belongs to the technical field of electric furnace steelmaking. The smelting method comprises the following steps that when smelting begins, low-gear power supply is adopted, a furnace wall oxygen lance and a carbon lance are adopted while electrification is conducted, foaming slag submerged arc is made through oxygen blowing and carbon spraying, scrap steel is continuously added through a Consteel system after 1-3 min, cold-state direct reduction iron is added through a fifth hole of an electric furnace, molten steel in the furnace is heated through the electric arc, and metal materials in the furnace are molten through the molten steel; in the whole smelting process, lime and light-burned dolomite are added in batches, the adding amount of the lime is 30-50 kg / t steel, and the adding amount of the light-burned dolomite is 25-30 kg / t steel. The method is beneficial to maintaining whole-course flat molten pool smelting, reducing the electric energy consumption of electric furnace smelting and reducing the smelting cost; a technical scheme is provided for short-process demonstration factories for efficiently using the direct reduction iron by the electric furnace, and the technical research blank of the domestic electric furnace short-process industry is filled.

Description

Technical Field

[0001] The invention belongs to the technical field of electric furnace steelmaking, in particular to a method for smelting cold direct reduced iron in a Consteel electric furnace. Background Art

[0002] At present, the development of "hydrogen metallurgy-electric furnace process" is on the rise, which can greatly reduce CO 2 Emissions will be reduced significantly, and the negative impact of steel smelting on the environment will be significantly reduced. This will further promote the transformation and upgrading of the steel industry and low-carbon smelting, and lead steel companies to transform from traditional "carbon metallurgy" to new "hydrogen metallurgy". However, direct reduced iron, as a product of hydrogen metallurgy, is rarely used in electric furnaces. There is no empirical data to refer to for the matching of direct reduced iron and scrap steel feeding speed and electrode power supply gear. The technical and economic indicators of direct reduced iron are high. If the direct reduced iron is not operated properly, it is very easy to form an iceberg phenomenon and a large boiling accident; or it may cause high temperature in the furnace, serious lining erosion, and reduced furnace life. Therefore, a method for smelting cold direct reduced iron in a Constite electric furnace is provided, which has an important impact on the electric furnace steelmaking process. Patent CN114540574A discloses a method for smelting cold-charged direct reduced iron in an electric furnace. The invention first adds a mixture of scrap steel and direct reduced iron into the electric furnace, and performs operations such as arcing, melting, and steel tapping. It has no guiding significance for the continuously charged Constite electric furnace. The present invention provides a method for smelting cold direct reduced iron in a Constite electric furnace, clarifies the relationship between the adding speed of direct reduced iron and scrap steel and the power supply gear of the electrode, provides a method for blowing oxygen, spraying carbon, and slag making with cold direct reduced iron, effectively avoids the slow melting and agglomeration of direct reduced iron, the formation of an iceberg phenomenon, stabilizes the smelting process and endpoint control, and improves technical and economic indicators such as electric furnace power consumption, oxygen consumption, carbon powder consumption, and smelting cycle. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for smelting cold direct reduced iron in a Conside electric furnace.

[0004] In order to solve the above technical problems, the technical scheme adopted by the present invention is: a method for smelting cold direct reduced iron in a Consteel electric furnace, the smelting method comprising the following steps: at the beginning of smelting, low-speed power supply is adopted, and at the same time of power on, the furnace wall oxygen lance and carbon lance are adopted to blow oxygen and spray carbon to form foam slag buried arc, 1 to 3 minutes later, scrap steel is continuously added by the Consteel system, and cold direct reduced iron is added from the fifth hole of the electric furnace, the molten steel in the furnace is heated by the electric arc, and the molten steel melts the metal material in the furnace; during the whole smelting process, lime and light-burned dolomite are added in batches, the amount of lime added is 30 to 50 kg / t steel, and the amount of light-burned dolomite added is 25 to 30 kg / t steel.

[0005] The specific control process of the smelting method of the present invention is as follows: Step 1, charging and melting period: At the beginning of smelting, low-speed power supply is used, and the oxygen lance and carbon lance on the furnace wall are used to blow oxygen and spray carbon to form foam slag buried arc; at the same time, Conside starts to add scrap steel, and direct reduced iron is added from the fifth hole of the electric furnace; Step 2, melting and heating period: blowing oxygen and spraying carbon to make foam slag, raising the power supply level after arc burial, adding scrap steel and direct reduced iron into the furnace continuously, and stopping adding scrap steel and direct reduced iron when the metal material in the furnace meets the steelmaking requirements, and entering the refining and heating period after 3 minutes; Step 3: After the temperature of the molten steel in the furnace reaches the tapping requirement, the smelting is completed and the tapping operation is performed.

[0006] In step 1 of the present invention, after the smelting of the previous heat is completed, 40% to 60% of the steel remains in the furnace as the starting heat for the next heat.

[0007] In step 1 of the present invention, scrap steel and direct reduced iron are continuously added into the furnace, the direct reduced iron adding speed is controlled at 1-4 t / min, the scrap steel feeding speed is 2-4 t / min, the added direct reduced iron ratio is 20%-60%, the scrap steel ratio is 40%-80%, and the direct reduced iron is in a cold state; the low-speed power supply is 75%-85% of the maximum power supply voltage output by the transformer.

[0008] In step 1 and step 2 of the present invention, oxygen is blown and carbon is sprayed to make foamed slag. The furnace wall oxygen lance and carbon lance are respectively 4 KT oxygen lances and 4 KT carbon lances. The oxygen supply intensity of the furnace wall oxygen lance is 7000-10000Nm 3 / h, and the carbon injection flow rate is 60~120kg / min.

[0009] In step 2 of the present invention, the high power supply gear is 85% to 95% of the maximum power supply voltage output by the transformer.

[0010] In step 1 and step 2 of the present invention, after the carbon oxygen gun on the furnace wall blows oxygen and sprays carbon to make foamed slag and bury the arc for 1 to 3 minutes, the metal material is added. At this time, the optimal temperature in the furnace is 1550 to 1570°C, and this temperature is maintained to melt the scrap steel and direct reduced iron in the furnace, and the direct reduced iron is in a cold state; the fifth hole of the electric furnace is located on the furnace cover of the electric furnace, and the direct reduced iron is vertically fed into the furnace from the material pipe above the furnace cover.

[0011] In step 3 of the present invention, scrap steel and cold direct reduced iron are continuously added into the furnace at a feeding rate increased from 3 to 5 t / min to 5 to 9 t / min; the metal material in the furnace meets the steel tapping requirements, that is, the total weight of the furnace body = the amount of steel tapped + the amount of steel retained.

[0012] In step 3 of the present invention, the relationship between the feeding speed of the scrap steel and the direct reduced iron continuously added into the furnace and the active power of the power supply should satisfy the requirements of formula (I): P 有功 =20×V废钢 +25×V 直接还原铁 (I) Where: P 有功 : The power supply level used for smelting corresponds to the active power, in MW; V 废钢 : Considy scrap steel feeding speed, unit is t / min; V 直接还原铁 : Cold direct reduced iron feeding rate, unit is t / min.

[0013] In step 3 of the present invention, the tapping temperature of the molten steel is 1600-1630°C.

[0014] The beneficial effects of adopting the above technical scheme are as follows: the present invention provides a method for smelting cold direct reduced iron in a Constite electric furnace, and provides a matching relationship between the feeding speed of scrap steel and direct reduced iron and the input active power. By controlling a reasonable oxygen supply system, a carbon injection system, and a power supply system, it is helpful to maintain flat molten pool smelting throughout the process, which is beneficial to improving energy efficiency, reducing the power consumption of electric furnace smelting by 10 to 30 kwh / t, shortening the smelting cycle by 3 to 6 minutes, and reducing smelting costs; at the same time, the whole process of foam slag submerged arc flat molten pool smelting reduces noise pollution; the present invention provides a technical solution for an electric furnace efficient use of direct reduced iron short process demonstration factory, filling the domestic electric furnace short process industry technology research gap. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below in conjunction with embodiments. Example 1

[0016] A method for smelting cold direct reduced iron in a Considy electric furnace, taking a 150-ton electric arc furnace as an example, the specific control process is as follows: Step 1, charging and melting period: after the smelting of the previous batch is finished, 70 tons of steel (40% of the steel) are left in the furnace as the starting heat for the next batch. At the beginning of smelting, 8 gears of power supply are used (8 gears of output power is 75% of the highest power), and the furnace wall oxygen gun and carbon gun are used at the same time to blow oxygen and spray carbon to make foam slag submerged arc, and the oxygen supply intensity is 7000Nm 3 / h, the carbon injection rate is 60kg / min. One minute after the power is turned on, the temperature in the furnace reaches 1550℃, and Conside starts to add scrap steel, and cold direct reduced iron is added from the fifth hole of the electric furnace. Scrap steel and direct reduced iron are added to the furnace continuously, the direct reduced iron addition rate is controlled at 1-2t / min, the scrap steel entry rate is 2-3t / min, the added direct reduced iron ratio is 20%, and the scrap steel ratio is 80%.

[0017] Step 2, melting and heating period: blowing oxygen and spraying carbon to make foam slag, the oxygen supply intensity is 8500Nm 3 / h, the carbon injection rate is 90kg / min. At 4min, the scrap steel and DRI feeding speeds are increased to 4-7t / min and 2-3t / min, respectively. At the same time, the power supply gear is adjusted according to the scrap steel and DRI feeding speeds. The relationship between the feeding speed of scrap steel and direct reduced iron continuously added to the furnace and the active power supply should meet the requirements of formula (I): P 有功 =20×V 废钢 +25×V 直接还原铁 (I) Where: P 有功 : The power supply level used for smelting corresponds to the active power, in MW; V 废钢 : Considy scrap steel feeding speed, unit is t / min; V 直接还原铁 : Cold direct reduced iron feeding rate, unit is t / min.

[0018] When the amount of scrap steel added reaches 136t and the amount of DRI added reaches 34t, the metal material in the furnace meets the steelmaking requirements, and the addition of scrap steel and DRI is stopped. After 3 minutes, the refining and heating period begins.

[0019] Step 3: When the temperature of the molten steel in the furnace reaches 1600°C, the smelting is completed and the steel tapping operation is carried out with a steel tapping amount of 155t.

[0020] During the entire smelting process, lime and light-burned dolomite are added in batches. The amount of lime added is 30kg / t steel, the amount of light-burned dolomite added is 25kg / t steel, and the power consumption for smelting one ton of steel is 393kWh / t. Example 2

[0021] A method for smelting cold direct reduced iron in a Considy electric furnace, taking a 150-ton electric arc furnace as an example, the specific control process is as follows: Step 1, charging and melting period: after the last heat of smelting is finished, 80 tons of steel (50% of the steel) are left in the furnace as the starting heat for the next heat. At the beginning of smelting, 10 gears of power supply are used (10 gears of output power is 80% of the highest power), and the furnace wall oxygen gun and carbon gun are used at the same time to blow oxygen and spray carbon to make foam slag submerged arc, and the oxygen supply intensity is 8000Nm 3 / h, the carbon injection rate is 80kg / min. 2 minutes after the power is turned on, the temperature in the furnace reaches 1560℃, and Conside starts to add scrap steel, and adds cold direct reduced iron from the fifth hole of the electric furnace. Scrap steel and direct reduced iron are added to the furnace continuously, the direct reduced iron addition rate is controlled at 1-2t / min, the scrap steel entry rate is 2-4t / min, the added direct reduced iron ratio is 40%, and the scrap steel ratio is 60%.

[0022] Step 2, melting and heating period: blowing oxygen and spraying carbon to make foam slag, the oxygen supply intensity is 9000Nm 3 / h, the carbon injection rate is 100kg / min. At 3min, increase the scrap steel and DRI feeding speed, scrap steel feeding speed 3-6t / min, DRI feeding speed 3-4t / min. At the same time, adjust the power supply gear according to the scrap steel and DRI feeding speed. The relationship between the feeding speed of scrap steel and direct reduced iron continuously added to the furnace and the active power of the power supply should meet the requirements of formula (Ⅰ): P 有功 =20×V 废钢 +25×V 直接还原铁 (I) Where: P 有功 : The power supply level used for smelting corresponds to the active power, in MW; V 废钢 : Considy scrap steel feeding speed, unit is t / min; V 直接还原铁 : Cold direct reduced iron feeding rate, unit is t / min.

[0023] When the amount of scrap steel added reaches 105t and the amount of DRI added reaches 70t, the metal material in the furnace meets the steelmaking requirements, and the addition of scrap steel and DRI is stopped. After 3 minutes, the refining and heating period begins.

[0024] Step 3: When the temperature of the molten steel in the furnace reaches 1620°C, the smelting is completed and the steel tapping operation is carried out, with a steel tapping volume of 154t.

[0025] During the entire smelting process, lime and light-burned dolomite are added in batches. The amount of lime added is 40kg / t steel, the amount of light-burned dolomite added is 27kg / t steel, and the power consumption for smelting one ton of steel is 428kWh / t. Example 3

[0026] A method for smelting cold direct reduced iron in a Considy electric furnace, taking a 150-ton electric arc furnace as an example, the specific control process is as follows: Step 1, charging and melting period: After the last heat of smelting is finished, 80 tons of steel (50% of the steel) are left in the furnace as the starting heat for the next heat. At the beginning of smelting, 12 gear power supply is used (12 gear output power is 85% of the maximum power), and the furnace wall oxygen gun and carbon gun are used at the same time to blow oxygen and spray carbon to make foam slag submerged arc, and the oxygen supply intensity is 9000Nm 3 / h, the carbon injection rate is 100kg / min. The furnace temperature reaches 1570℃ 3 minutes after power-on, and Conside starts to add scrap steel, and cold direct reduced iron is added from the fifth hole of the electric furnace. Scrap steel and direct reduced iron are added to the furnace continuously, and the direct reduced iron addition rate is controlled at 2-4t / min, and the scrap steel entry rate is 2-3t / min. The proportion of direct reduced iron added is 60%, and the proportion of scrap steel is 40%.

[0027] Step 2, melting and heating period: blowing oxygen and spraying carbon to make foam slag, the oxygen supply intensity is 10000Nm3 / h, carbon injection rate is 120kg / min. At 4min, increase the scrap steel and DRI feeding speed, scrap steel feeding speed 2-4t / min, DRI feeding speed 4-6t / min. At the same time, adjust the power supply gear according to the scrap steel and DRI feeding speed. The relationship between the feeding speed of scrap steel and direct reduced iron continuously added to the furnace and the active power of the power supply should meet the requirements of formula (Ⅰ): P 有功 =20×V 废钢 +25×V 直接还原铁 (I) Where: P 有功 : The power supply level used for smelting corresponds to the active power, in MW; V 废钢 : Considy scrap steel feeding speed, unit is t / min; V 直接还原铁 : Cold direct reduced iron feeding rate, unit is t / min.

[0028] When the amount of scrap steel added reaches 72t and the amount of DRI added reaches 108t, the metal material in the furnace meets the steelmaking requirements, and the addition of scrap steel and DRI is stopped. After 3 minutes, the refining and heating period begins.

[0029] Step 3: When the temperature of the molten steel in the furnace reaches 1630°C, the smelting is completed and the steel tapping operation is carried out, with a steel tapping volume of 156t.

[0030] During the entire smelting process, lime and light-burned dolomite are added in batches. The amount of lime added is 50kg / t steel, the amount of light-burned dolomite added is 30kg / t steel, and the power consumption for smelting one ton of steel is 453kWh / t.

[0031] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for smelting cold direct reduced iron in a Considy electric furnace, characterized in that: The smelting method comprises the following steps: at the beginning of smelting, low-speed power supply is adopted, and at the same time of power on, oxygen lance and carbon lance of furnace wall are adopted to blow oxygen and spray carbon to form foam slag buried arc, scrap steel is continuously added by Consteel system after 1 to 3 minutes, cold direct reduced iron is added by the fifth hole of electric furnace, molten steel in the furnace is heated by electric arc, and the molten steel melts the metal material in the furnace; during the whole smelting process, lime and light-burned dolomite are added in batches, the amount of lime added is 30 to 50 kg / t steel, and the amount of light-burned dolomite added is 25 to 30 kg / t steel.

2. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 1, characterized in that: The specific control process of the smelting method is as follows: Step 1, charging and melting period: At the beginning of smelting, low-speed power supply is used, and the oxygen lance and carbon lance on the furnace wall are used to blow oxygen and spray carbon to form foam slag buried arc; at the same time, Conside starts to add scrap steel, and direct reduced iron is added from the fifth hole of the electric furnace; Step 2, melting and heating period: blowing oxygen and spraying carbon to make foam slag, raising the power supply level after arc burial, adding scrap steel and direct reduced iron into the furnace continuously, and stopping adding scrap steel and direct reduced iron when the metal material in the furnace meets the steelmaking requirements, and entering the refining and heating period after 3 minutes; Step 3: After the temperature of the molten steel in the furnace reaches the tapping requirement, the smelting is completed and the tapping operation is performed.

3. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 2, characterized in that: In step 1, after the smelting of the previous heat is completed, 40% to 60% of the steel remains in the furnace as the starting heat for the next heat.

4. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 2, characterized in that: In the step 1, scrap steel and direct reduced iron are continuously added into the furnace, the direct reduced iron adding speed is controlled at 1-4 t / min, the scrap steel feeding speed is 2-4 t / min, the added direct reduced iron ratio is 20%-60%, the scrap steel ratio is 40%-80%, and the direct reduced iron is in a cold state; the low-speed power supply is 75%-85% of the maximum power supply voltage output by the transformer.

5. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 2, characterized in that: In the step 1 and step 2, oxygen is blown and carbon is sprayed to make foamed slag. The furnace wall oxygen lance and carbon lance are respectively 4 KT oxygen lances and 4 KT carbon lances. The oxygen supply intensity of the furnace wall oxygen lance is 7000-10000Nm 3 / h, and the carbon injection flow rate is 60~120kg / min.

6. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 2, characterized in that: In step 2, the high power supply gear is 85% to 95% of the maximum power supply voltage output by the transformer.

7. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 2, characterized in that: In the steps 1 and 2, after the carbon oxygen gun on the furnace wall blows oxygen and sprays carbon to make foamed slag and bury the arc for 1 to 3 minutes, the metal material is added. At this time, the optimal temperature in the furnace is 1550 to 1570°C, and this temperature is maintained to melt the scrap steel and direct reduced iron in the furnace, and the direct reduced iron is in a cold state; the fifth hole of the electric furnace is located on the furnace cover of the electric furnace, and the direct reduced iron is vertically fed into the furnace from the material pipe above the furnace cover.

8. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 2, characterized in that: In step 2, scrap steel and cold direct reduced iron are continuously added into the furnace at a feeding rate increased from 3 to 5 t / min to 5 to 9 t / min; the metal material in the furnace meets the steel tapping requirements, that is, the total weight of the furnace body = the amount of steel tapped + the amount of steel retained.

9. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 2, characterized in that: In step 2, the relationship between the feeding rate of scrap steel and direct reduced iron continuously added into the furnace and the active power supply should meet the requirements of formula (I): P 有功 =20×V 废钢 +25×V 直接还原铁 (Ⅰ) Where: P 有功 : The power supply level used for smelting corresponds to the active power, in MW; V 废钢 : Considy scrap steel feeding speed, unit is t / min; V 直接还原铁 : Cold direct reduced iron feeding rate, unit is t / min.

10. The method for smelting cold direct reduced iron in a Considy electric furnace according to claim 2, characterized in that: In step 3, the tapping temperature of the molten steel is 1600-1630°C.