A smelting method of cold direct reduced iron in a Consteel electric furnace

Abstract

The invention discloses a smelting method of cold direct reduced iron in a Consteel electric furnace, belonging to the technical field of electric furnace steelmaking. The smelting method comprises the following steps: at the beginning of smelting, low-grade power supply is adopted, and at the same time of power-on, oxygen lances and carbon lances on the furnace wall are used to blow oxygen and spray carbon to produce foamed slag for submerged arc. After 1-3 minutes, scrap steel is continuously added by the Consteel system, and cold direct reduced iron is added through 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 materials in the furnace; during the whole smelting process, lime and light burned dolomite are added in batches. The addition amount of lime is 30-50 kg / t of steel, and the addition amount of light burned dolomite is 25-30 kg / t of steel. The invention helps to maintain the whole-process flat bath smelting, reduce the power consumption of electric furnace smelting, and reduce the smelting cost; it provides a technical solution for a short-process demonstration plant for the efficient use of direct reduced iron in an electric furnace, filling the domestic technical research gap in the short-process industry of electric furnaces.

Description

Technical Field

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

[0002] At present, the development of the "hydrogen metallurgy - electric furnace process" is on the rise. It can greatly reduce CO2 emissions, significantly reduce the negative impact of steelmaking on the environment, further promote the transformation and upgrading of the steel industry and low-carbon smelting, and lead steel enterprises to transform from traditional "carbon metallurgy" to new "hydrogen metallurgy". However, the application of direct reduced iron as a product of hydrogen metallurgy in electric furnaces is extremely rare. There is no available empirical data for the matching between the charging speed of direct reduced iron and scrap and the electrode power supply gear. The technical and economic indexes of adding direct reduced iron are relatively high. If the operation is improper, the direct reduced iron is extremely easy to form an iceberg phenomenon and cause a large boiling accident; or cause high temperature in the furnace, serious erosion of the furnace lining, and reduction of the furnace life. Therefore, providing a smelting method of cold direct reduced iron in a Consteel electric furnace is of great significance to the electric furnace steelmaking process. Patent CN114540574A discloses an electric furnace smelting method of cold-charged direct reduced iron. The invention first adds a mixture of scrap and direct reduced iron into the electric furnace, and after operations such as arc starting, melting, and tapping, it has no guiding significance for the continuous charging Consteel electric furnace. The smelting method of cold direct reduced iron in a Consteel electric furnace of the present invention clarifies the relationship between the adding speed of direct reduced iron and scrap and the electrode power supply gear, provides a method of oxygen blowing, carbon spraying, and slag making for adding cold direct reduced iron, effectively avoids the slow melting and caking of direct reduced iron and the formation of the iceberg phenomenon, stabilizes the smelting process and end point control, and improves the technical and economic indexes such as the power consumption, oxygen consumption, pulverized coal injection consumption, and smelting cycle of the electric furnace. Summary of the Invention

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

[0004] To solve the above technical problem, the technical solution adopted by the present invention is: a smelting method of cold direct reduced iron in a Consteel electric furnace, the smelting method includes the following steps: at the beginning of smelting, low-gear power supply is adopted. While powering on, an oxygen lance and a carbon lance on the furnace wall are used to blow oxygen and spray carbon to make a foamed slag for submerged arc. After 1 - 3 minutes, scrap is continuously added by the Consteel system, and cold direct reduced iron is added through the fifth hole of the electric furnace. The molten steel in the furnace is heated by the arc, and the molten steel melts the metal materials in the furnace; during the whole smelting process, lime and calcined dolomite are added in batches. The addition amount of lime is 30 - 50 kg / t of steel, and the addition amount of calcined dolomite is 25 - 30 kg / t of steel.

[0005] The specific control process of the smelting method of the present invention is as follows:

[0006] Step 1, charging and melting period: At the beginning of smelting, low gear power supply is adopted. While powering on, the wall oxygen lance and carbon lance are used to blow oxygen and inject carbon to create foamy slag for submerged arc; at the same time, Consarc starts to add scrap steel, and directly reduced iron is added through the fifth hole of the electric furnace.

[0007] Step 2, molten steel cleaning and temperature rising period: Blow oxygen and inject carbon to create foamy slag. After submerged arc, increase the power supply gear. Scrap steel and directly reduced iron are continuously added into the furnace. When the metal materials in the furnace meet the tapping requirements, stop adding scrap steel and directly reduced iron, and enter the refining and temperature rising period after 3 minutes.

[0008] Step 3, until the molten steel temperature in the furnace reaches the tapping requirements, the smelting ends and tapping operation is carried out.

[0009] In step 1 of the present invention, at the end of the previous smelting cycle, 40% - 60% of the molten steel is left in the furnace as the starting heat for the next smelting cycle.

[0010] In step 1 of the present invention, scrap steel and directly reduced iron are continuously added into the furnace. The adding speed of directly reduced iron is controlled at 1 - 4 t / min, the charging speed of scrap steel into the furnace is 2 - 4 t / min, the proportion of added directly reduced iron is 20% - 60%, the proportion of scrap steel is 40% - 80%, and the directly reduced iron is in cold state; the low gear power supply is 75% - 85% of the highest output power supply voltage of the transformer.

[0011] In steps 1 and 2 of the present invention, when blowing oxygen and injecting carbon to create foamy slag, there are 4 KT oxygen lances and 4 KT carbon lances on the furnace wall respectively. The oxygen supply intensity of the wall oxygen lance is 7000 - 10000 Nm 3 / h, and the carbon injection flow rate is 60 - 120 kg / min.

[0012] In step 2 of the present invention, the high gear power supply is 85% - 95% of the highest output power supply voltage of the transformer.

[0013] In steps 1 and 2 of the present invention, after blowing oxygen and injecting carbon by the wall carbon-oxygen lance to create foamy slag and carry out submerged arc for 1 - 3 minutes, metal materials are added. At this time, the optimal temperature in the furnace is 1550 - 1570 °C, and this temperature is maintained to melt the scrap steel and directly reduced iron in the furnace. The directly reduced iron is in cold state; the fifth hole of the electric furnace is located on the furnace cover of the electric furnace, and the directly reduced iron is vertically input into the furnace through the charging pipe above the furnace cover.

[0014] In step 3 of the present invention, the charging speed of scrap steel and cold directly reduced iron continuously added into the furnace is increased from 3 - 5 t / min to 5 - 9 t / min; the metal materials in the furnace meet the tapping requirements, that is, the total weight of the furnace body = tapping amount + remaining molten steel amount.

[0015] In step 3 of the present invention, the relationship between the charging speed of scrap steel and directly reduced iron continuously added into the furnace and the active power of the power supply should meet the requirements of formula (Ⅰ):

[0016] P 有功 = 20×V 废钢 + 25×V 直接还原铁 (Ⅰ)

[0017] Wherein:

[0018] P 有功 : The active power corresponding to the power supply gear used for smelting, unit MW; V 废钢 : The feeding speed of Considere scrap, unit t / min; V 直接还原铁 : The feeding speed of cold direct reduced iron, unit t / min.

[0019] In step 3 of the present invention, the tapping temperature of molten steel is 1600 - 1630 °C.

[0020] The beneficial effects of adopting the above technical solutions are as follows: The present invention provides a smelting method of cold direct reduced iron in a Considere electric furnace, and provides the matching relationship between the feeding speeds of scrap and direct reduced iron and the input active power. By controlling reasonable oxygen supply system, carbon injection system, and power supply system, it helps to maintain the whole-process flat bath smelting, which is beneficial to improving energy efficiency, reducing the power consumption of electric furnace smelting by 10 - 30 kwh / t, shortening the smelting cycle by 3 - 6 min, and reducing the smelting cost; at the same time, the whole-process foam slag submerged arc flat bath smelting reduces the noise pollution; the present invention provides a technical solution for the short-process demonstration plant of the efficient use of direct reduced iron in electric furnaces, filling the technical research gap in the domestic electric furnace short-process industry. Specific Embodiments

[0021] The present invention will be further described in detail below in conjunction with embodiments. Embodiment 1

[0022] A smelting method of cold direct reduced iron in a Considere electric furnace, taking a 150-ton electric arc furnace as an example, the specific control process is as follows:

[0023] Step 1, charging and melting period: At the end of the previous furnace smelting, 70 tons of molten steel (40% of the molten steel left) is left in the furnace as the starting heat for the next furnace. At the start of smelting, 8th gear power supply is adopted (the output power of the 8th gear is 75% of the maximum power). While powering on, the oxygen lance and carbon lance on the furnace wall are used to blow oxygen and inject carbon to make foam slag and submerge the arc, and the oxygen supply intensity is 7000 Nm 3 / h, and the carbon injection rate is 60 kg / min. When the temperature in the furnace reaches 1550 °C after 1 min of powering on, Considere starts to add scrap, and cold direct reduced iron is added through the fifth hole of the electric furnace. The scrap and direct reduced iron are continuously added into the furnace. The feeding speed of direct reduced iron is controlled at 1 - 2 t / min, the scrap charging speed into the furnace is 2 - 3 t / min, the proportion of added direct reduced iron is 20%, and the proportion of scrap is 80%.

[0024] Step 2, melting and temperature-rising period: Oxygen is blown and carbon is sprayed to create foamy slag. The oxygen supply intensity is 8500 Nm 3 / h, and the carbon spraying rate is 90 kg / min. At 4 minutes, increase the feeding speed of scrap steel and DRI. The feeding speed of scrap steel is 4 - 7 t / min, and the feeding speed of DRI is 2 - 3 t / min. At the same time, adjust the power supply gear according to the feeding speeds of scrap steel and DRI. The relationship between the feeding speeds of scrap steel and direct reduced iron continuously added into the furnace and the active power of the power supply should meet the requirements of formula (Ⅰ):

[0025] P 有功 =20×V 废钢 +25×V 直接还原铁 (Ⅰ)

[0026] In the formula: P 有功 : The active power corresponding to the power supply gear used for smelting, with the unit of MW; V 废钢 : The feeding speed of Considere scrap steel, with the unit of t / min; V 直接还原铁 : The feeding speed of cold direct reduced iron, with the unit of t / min.

[0027] When the addition amount of scrap steel reaches 136 t and the addition amount of DRI reaches 34 t, the metal materials in the furnace meet the tapping requirements. Stop adding scrap steel and DRI, and enter the refining and temperature-rising period after 3 minutes.

[0028] Step 3, until the temperature of the molten steel in the furnace reaches 1600 °C, the smelting ends, and tapping operation is carried out with a tapping amount of 155 t.

[0029] During the whole smelting process, lime and lightly burned dolomite are added in batches. The addition amount of lime is 30 kg / t of steel, the addition amount of lightly burned dolomite is 25 kg / t of steel, and the power consumption per ton of steel smelting is 393 kWh / t. Example 2

[0030] A smelting method of cold direct reduced iron in a Considere electric furnace. Taking a 150-ton electric arc furnace as an example, the specific control process is as follows:

[0031] Step 1, feeding and melting period: After the previous furnace smelting ends, 80 tons of molten steel (50% of the molten steel left) is left in the furnace as the starting heat for the next furnace. At the start of smelting, 10th gear power supply is adopted (the output power of the 10th gear is 80% of the maximum power). While powering on, the oxygen lance and carbon lance on the furnace wall are used to blow oxygen and spray carbon to create foamy slag for submerged arc, and the oxygen supply intensity is 8000 Nm 3 / h, the carbon injection rate is 80 kg / min. When the power is turned on for 2 minutes, the temperature in the furnace reaches 1560 °C, and Consarc starts to add scrap steel, and cold direct reduced iron is added through the fifth hole of the electric furnace. The scrap steel and direct reduced iron are continuously added into the furnace. The addition rate of direct reduced iron is controlled at 1 - 2 t / min, the scrap steel charging rate into the furnace is 2 - 4 t / min, the proportion of direct reduced iron added is 40%, and the proportion of scrap steel is 60%.

[0032] Step 2, melting and temperature rising period: Oxygen is blown and carbon is injected to form foamy slag, and the oxygen supply intensity is 9000 Nm 3 / h, the carbon injection rate is 100 kg / min. At 3 minutes, the charging rates of scrap steel and DRI are increased. The scrap steel charging rate is 3 - 6 t / min, and the DRI charging rate is 3 - 4 t / min. At the same time, the power supply gear is adjusted according to the charging rates of scrap steel and DRI. The relationship between the charging rates of scrap steel and direct reduced iron continuously added into the furnace and the active power of the power supply should meet the requirements of formula (Ⅰ):

[0033] P 有功 = 20×V 废钢 + 25×V 直接还原铁 (Ⅰ)

[0034] In the formula:

[0035] P 有功 : The active power corresponding to the power supply gear used for smelting, unit is MW; V 废钢 : The Consarc scrap steel charging rate, unit is t / min; V 直接还原铁 : The cold direct reduced iron charging rate, unit is t / min.

[0036] When the scrap steel addition amount reaches 105 t and the DRI addition amount reaches 70 t, the metal materials in the furnace meet the tapping requirements, stop adding scrap steel and DRI, and enter the refining and temperature rising period after 3 minutes.

[0037] Step 3, until the molten steel temperature in the furnace reaches 1620 °C, the smelting is completed, and tapping operation is carried out, and the tapping amount is 154 t.

[0038] During the whole smelting process, lime and calcined dolomite are added in batches. The lime addition amount is 40 kg / t of steel, the calcined dolomite addition amount is 27 kg / t of steel, and the power consumption for smelting per ton of steel is 428 kWh / t. Example 3

[0039] A smelting method of cold direct reduced iron in Consarc electric furnace, taking a 150-ton electric arc furnace as an example, the specific control process is as follows:

[0040] Step 1, Charging and Melting Period: At the end of the previous furnace operation, 80 tons of molten steel (50% of the molten steel left) is left in the furnace as the starting heat for the next furnace operation. At the start of the smelting, the power supply is set to gear 12 (the output power of gear 12 is 85% of the maximum power). While powering on, an oxygen lance and a carbon lance on the furnace wall are used to blow oxygen and inject carbon to create a foamy slag and bury the arc. The oxygen supply intensity is 9000 Nm 3 / h, and the carbon injection rate is 100 kg / min. When the temperature in the furnace reaches 1570 °C after 3 minutes of powering on, Consarc starts adding scrap steel, and directly reduced iron (DRI) in cold state is added through the fifth hole of the electric furnace. The scrap steel and DRI are continuously added into the furnace. The addition rate of DRI is controlled at 2 - 4 t / min, the scrap steel charging rate into the furnace is 2 - 3 t / min, the proportion of added DRI is 60%, and the proportion of scrap steel is 40%.

[0041] Step 2, Molten Metal Clearing and Temperature Rising Period: Blow oxygen and inject carbon to create a foamy slag. The oxygen supply intensity is 10000 Nm 3 / h, and the carbon injection rate is 120 kg / min. After 4 minutes, increase the charging rates of scrap steel and DRI. The scrap steel charging rate is 2 - 4 t / min, and the DRI charging rate is 4 - 6 t / min. At the same time, adjust the power supply gear according to the charging rates of scrap steel and DRI. The relationship between the continuous charging rates of scrap steel and DRI into the furnace and the active power of the power supply should meet the requirements of formula (Ⅰ):

[0042] P 有功 =20×V 废钢 +25×V 直接还原铁 (Ⅰ)

[0043] In the formula:

[0044] P 有功 : The active power corresponding to the power supply gear used for smelting, unit: MW; V 废钢 : The charging rate of Consarc scrap steel, unit: t / min; V 直接还原铁 : The charging rate of cold state directly reduced iron, unit: t / min.

[0045] When the scrap steel addition reaches 72 t and the DRI addition reaches 108 t, the metal charge in the furnace meets the tapping requirements. Stop adding scrap steel and DRI, and enter the refining and temperature rising period after 3 minutes.

[0046] Step 3, When the molten steel temperature in the furnace reaches 1630 °C, the smelting ends and tapping operation is carried out. The tapping amount is 156 t.

[0047] During the whole smelting process, lime and calcined dolomite are added in batches. The lime addition amount is 50 kg / t of steel, the calcined dolomite addition amount is 30 kg / t of steel, and the power consumption for smelting per ton of steel is 453 kWh / t.

[0048] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the present invention, and any modification or partial substitution without departing from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. A smelting method of cold direct reduced iron in a Consteel electric furnace, characterized in that, The smelting method includes the following steps: At the beginning of smelting, low-grade power supply is adopted. While powering on, wall oxygen lance and carbon lance are used. Oxygen is blown and carbon is sprayed to create foamed slag for submerged arc. After 1 - 3 minutes, scrap steel is continuously added by the Consteel system, and cold direct reduced iron is added through 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 materials in the furnace. During the whole smelting process, lime and light burned dolomite are added in batches. The addition amount of lime is 30 - 50 kg / t of steel, and the addition amount of light burned dolomite is 25 - 30 kg / t of steel. The specific control process of the smelting method is as follows: Step 1, charging and melting period: At the beginning of smelting, low-grade power supply is adopted. While powering on, wall oxygen lance and carbon lance are used. Oxygen is blown and carbon is sprayed to create foamed slag for submerged arc. After 1 - 3 minutes, the Consteel starts to add scrap steel, and direct reduced iron is added through the fifth hole of the electric furnace. Step 2, molten steel clearing and temperature rising period: Oxygen is blown and carbon is sprayed to create foamed slag. After submerged arc, the power supply grade is increased. Scrap steel and direct reduced iron are continuously added into the furnace. When the metal materials in the furnace meet the tapping requirements, the addition of scrap steel and direct reduced iron is stopped. After 3 minutes, it enters the refining and temperature rising period. Step 3, until the temperature of the molten steel in the furnace reaches the tapping requirements, the smelting ends and tapping operation is carried out. In Step 1, after the previous smelting cycle ends, 40% - 60% of the molten steel remains in the furnace as the starting heat for the next smelting cycle. In Step 2, the relationship between the feeding speed of scrap steel and direct reduced iron continuously added into 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) In the formula: P 有功 : Active power corresponding to the power supply gear used for smelting, unit: MW; V 废钢 : Scrap charging speed of Consteel, unit: t / min; V 直接还原铁 : Cold direct reduced iron charging speed, unit: t / min; In the above-mentioned Step 1 and Step 2, foam slag is formed by blowing oxygen and injecting carbon. There are 4 KT oxygen lances and 4 KT carbon lances on the furnace wall respectively. The oxygen supply intensity of the oxygen lances on the furnace wall is 7000-10000 Nm 3 / h, and the carbon injection flow rate is 60-120 kg / min.

2. The smelting method of cold direct reduced iron in a Consteel electric furnace according to claim 1, characterized in that In Step 1, scrap steel and direct reduced iron are continuously added into the furnace. The addition speed of direct reduced iron is controlled at 1 - 4 t / min, the scrap steel charging speed is 2 - 4 t / min, the proportion of direct reduced iron added is 20% - 60%, the proportion of scrap steel is 40% - 80%, and the direct reduced iron is cold. The low-grade power supply is 75% - 85% of the highest output supply voltage of the transformer.

3. The smelting method of cold-state direct reduced iron in a Consteel electric furnace according to claim 1, characterized in that, In Step 2, the high power supply grade is 85% - 95% of the highest output supply voltage of the transformer.

4. A smelting method of cold-state direct reduced iron in a Consteel electric furnace according to claim 1, characterized in that, In Step 1 and Step 2, after blowing oxygen and spraying carbon by the wall carbon-oxygen lance to create foamed slag for submerged arc for 1 - 3 minutes, metal materials are added. At this time, the optimal temperature in the furnace is 1550 - 1570 °C, and this temperature is maintained to melt the scrap steel and direct reduced iron in the furnace. The direct reduced iron is cold. The fifth hole of the electric furnace is located on the furnace cover of the electric furnace, and the direct reduced iron is vertically input into the furnace through the charging pipe above the furnace cover.

5. A smelting method of cold direct reduced iron in a Consteel electric furnace according to claim 1, characterized in that, In Step 2, the feeding speed of scrap steel and cold direct reduced iron continuously added into the furnace is increased from 3 - 5 t / min to 5 - 9 t / min. When the metal materials in the furnace meet the tapping requirements, that is, the total weight of the furnace body = tapping amount + remaining molten steel amount.

6. A smelting method of cold direct reduced iron in a Consteel electric furnace according to claim 1, characterized in that, In Step 3, the tapping temperature of the molten steel is 1600 - 1630 °C.