A smelting process for reducing the content of ferrous oxide in the slag

Abstract

The present application belongs to the field of smelting process, and particularly relates to a smelting process for reducing the content of ferrous oxide in slag. The present application effectively reduces the content of ferrous oxide in slag by optimizing the oxygen feeding time, adjusting the position of the oxygen lance, combining with the point-to-point injection of carbon powder and specific power supply process parameters, reduces the content of ferrous oxide to 13% to 17%, and also reduces the oxygen consumption, smelting cycle and smelting power consumption, the average oxygen consumption is 17.74 Nm 3 / t, the average smelting cycle is 49.0 min / oven, and the average smelting power consumption is 433.71 kWh / t, which greatly reduces the smelting cost. Due to the reduction of ferrous oxide in slag, a large amount of iron loss in the slag discharge process is avoided, which is of great significance for low-cost smelting of scrap steel in an electric furnace.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of smelting process, in particular to a smelting process for reducing the content of ferrous oxide in slag. BACKGROUND

[0002] The electric arc smelting is mainly applied to the treatment of scrap steel materials, and the scrap steel materials are heated by graphite electrodes, and slagging is performed by oxygen combustion and carbon powder injection, so that the scrap steel materials can be effectively treated.

[0003] However, in actual production, through sampling and testing of the slag generated by arc smelting of scrap steel, it is found that the content of ferrous oxide in the slag is high, up to 27%-30%, so that a large amount of iron is lost with the slag during the slagging process in the later stage of the electric furnace, and the iron loss caused by combined slag is as high as 12.08 kg / t according to the calculation of 85 t / furnace steel. 钢 Such a large amount of iron loss directly leads to an increase in the cost of scrap steel treatment. In order to reduce the production cost, the amount of oxygen used is usually reduced in the prior art, but this will prolong the smelting cycle and increase the smelting power consumption, and thus cannot achieve the effect of reducing the cost. Therefore, it is of great significance to develop a smelting process for reducing the content of ferrous oxide in slag without increasing the smelting cycle for the utilization of scrap steel. SUMMARY

[0004] In view of the technical problems in the prior art that the high content of ferrous oxide in the slag of arc smelting of scrap steel leads to an increase in production cost, and reducing the amount of oxygen used will prolong the smelting cycle, the present application provides a smelting process for reducing the content of ferrous oxide in slag. By setting the oxygen feeding time and adjusting the height / angle / distance of the oxygen lance from the molten pool, the amount of oxygen used is reduced while the oxygen is used to the maximum, which not only does not prolong the smelting cycle, but also reduces the content of ferrous oxide in the slag, greatly reduces the iron loss, and saves the process cost.

[0005] To achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a smelting process for reducing the content of ferrous oxide in slag, comprising the following steps:

[0007] Step one, adding a first batch of scrap steel materials into the electric arc furnace, supplying power, opening the oxygen lance after 6-7 minutes, preheating by oxygen blowing, and performing oxygen combustion and slagging after 50-70 seconds, when the melting rate of the first batch of scrap steel materials is greater than or equal to 80%, performing oxygen blowing and slagging, when the cumulative power consumption is 10000-11000 kWh / t, adding a first batch of lime, injecting carbon powder, and stopping power supply;

[0008] Step two, when the first batch of scrap steel melting rate is 90%-95%, the second batch of scrap steel is added, power supply, 5-6min after starting oxygen lance preheating, 30-50s after oxygen combustion smelting, when the second batch of scrap steel melting rate is greater than or equal to 80%, oxygen blowing smelting is carried out, when the cumulative power consumption is 20500-21500kWh / t, the second batch of lime is added, carbon powder is injected, slagging is carried out, and power supply is stopped;

[0009] Step three, when the second batch of scrap steel melting rate is 90%-95%, the third batch of scrap steel is added, power supply, 1-3min after starting oxygen lance preheating, 20-40s after oxygen combustion smelting, when the third batch of scrap steel melting rate is greater than or equal to 90%, oxygen blowing smelting is carried out, and carbon powder is injected to obtain a smelting melt;

[0010] Step four, when the cumulative power consumption is 31000-32000kWh / t, the smelting melt is heated to greater than or equal to 1580 DEG C, carbon powder is injected, when the molten steel temperature is greater than or equal to 1610 DEG C and the composition is qualified, power supply is stopped, and tapping is organized.

[0011] Preferably, the vertical height h of the central jet hole of the oxygen lance nozzle from the highest horizontal plane of the lower furnace body of the electric arc furnace is 150-180mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 41 DEG -45 DEG ; and the horizontal distance s of the central jet hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 150-260mm.

[0012] Compared with the prior art, the present application provides a smelting process for reducing the content of ferrous oxide in slag, and the inventor has found through a large number of studies that the main reason for the high content of ferrous oxide in slag is the improper timing of oxygen use and the excessive oxidation loss of scrap steel caused by excessive oxygen use. For the timing of oxygen use, the present application calculates and summarizes the existing oxygen supply mode, and the calculation formula for opening the oxygen lance in advance under the condition of insufficient carbon content in the furnace is T=HR / [5.47xn(M-2m)]-[Hx5.47xn(M-2m)], wherein the oxygen flow is M m³ / min, the natural gas flow is m m³ / min, the number of oxygen lances is n, the total slag amount in the furnace is R, the content of ferrous oxide in the slag is H, and the opening time of the oxygen lance is T min. According to the calculation, if the oxygen supply is advanced by 1 minute, the content of ferrous oxide in the slag will increase by 8.01%. Although the opening of the oxygen lance in advance will make the slag forming speed faster, the fluidity of such slag will be good, which is easy to cause low-temperature slag flow, and the slag at this time is difficult to separate from the steel due to low temperature, and a large amount of particle steel is contained in the slag, which causes a large amount of loss of ferrous oxide and particle steel. Therefore, the present application further optimizes the timing of oxygen supply and delays the opening time of the oxygen lance to reduce the content of ferrous oxide in the slag.

[0013] And for the excessive oxygen caused by scrap steel oxidation loss, mainly refers to the oxygen supply under the condition of fixed carbon content, exceeding the oxygen demand of carbon reaction, causing the molten steel over oxidation, leading to excess oxygen participating in the oxidation of the metal in the furnace, at the same time, the influence of the chemical heat generated by oxygen supply on the reduction of smelting power consumption and the improvement of production efficiency should be considered. Therefore, the oxygen consumption should be fully considered in the control of oxygen consumption. In view of this, the present application adjusts the angle, position and distance of the oxygen lance to improve the oxygen utilization rate, and the main principle is to adjust the liquid level of the molten pool or the position and angle of the oxygen lance, so that the oxygen lance has a closer jet distance with the liquid surface of the molten pool. Under the condition of the same or slightly lower oxygen consumption, even if the oxygen supply amount and intensity are lower, good decarburization and penetration effect can still be achieved.

[0014] Preferably, in step one, the amount of the first batch of lime added is 3%-4% of the mass of the first batch of scrap steel.

[0015] Preferably, in step two, the amount of the second batch of lime added is 2%-3% of the mass of the second batch of scrap steel.

[0016] Preferably, the power supply includes arc striking power supply, well penetrating power supply, melting power supply and temperature rising power supply.

[0017] Further preferably, the power supply includes arc striking power supply, well penetrating power supply, melting power supply and temperature rising power supply; wherein the power supply mode of the first batch of scrap steel and the second batch of scrap steel adopts arc striking power supply, well penetrating power supply and melting power supply; the power supply mode of the third batch of scrap steel adopts arc striking power supply, well penetrating power supply, melting power supply and temperature rising power supply.

[0018] Preferably, the arc striking power supply current is 45569-45589kA, and the voltage is 755-770V.

[0019] Preferably, the well penetrating power supply current is 42650-42670kA, and the voltage is 807-822V.

[0020] Preferably, the melting power supply current is 41326-41346kA, and the voltage is 833-848V.

[0021] Preferably, the temperature rising power supply current is 38911-38931kA, and the voltage is 885-900V.

[0022] Further preferably, the duration of the arc striking power supply is 1-2min.

[0023] Further preferably, the duration of the well penetrating power supply is 6-9min.

[0024] Further preferably, the duration of the melting power supply is 3-4min.

[0025] Preferably, the oxygen lance comprises a No. 1 oxygen lance, a No. 2 oxygen lance, a No. 3 oxygen lance and a No. 4 oxygen lance.

[0026] Further preferably, the vertical height h of the central nozzle hole of the No. 1 oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 160-180 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°-44°; and the horizontal distance s of the central nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 170-200 mm.

[0027] Further preferably, the vertical height h of the central nozzle hole of the No. 2 oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 160-175 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°-44°; and the horizontal distance s of the central nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 220-230 mm.

[0028] Further preferably, the vertical height h of the central nozzle hole of the No. 3 oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 150-155 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 42°-44°; and the horizontal distance s of the central nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 250-260 mm.

[0029] Further preferably, the vertical height h of the central nozzle hole of the No. 4 oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 165-175 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 41°-43°; and the horizontal distance s of the central nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 170-190 mm.

[0030] Preferably, in steps one to three, the nitrogen flow rate of the oxygen lance during the oxygen blowing preheating is 90-100 Nm³ / h, and the oxygen flow rate is 65-75 Nm³ / h.

[0031] Preferably, in steps one to three, the natural gas flow rate of the oxygen lance during the oxygen combustion fluxing is 95-105 Nm³ / h, and the oxygen flow rate is 275-285 Nm³ / h.

[0032] Preferably, in steps one to three, the natural gas flow rate of the oxygen lance during the oxygen blowing fluxing is 65-75 Nm³ / h, and the oxygen flow rate is 1490-1510 Nm³ / h.

[0033] Preferably, in step four, the oxygen supply intensity is adjusted before tapping, and the natural gas flow rate of the adjusted oxygen supply intensity is reduced by 8-12 Nm³ / h compared with the oxygen supply intensity during the oxygen blowing fluxing in step three, and the oxygen flow rate is reduced by 190-210 Nm³ / h.

[0034] Preferably, in steps one to four, the carbon powder is sprayed by point-by-point spraying, the flow rate of the sprayed carbon powder is 0.7-1.0 kg / (min·t), and the interval time is 7-9 s.

[0035] Preferably, the scrap steel material comprises the following components: 30%-35% of automobile cold plates, 65%-70% of metal scrap, and 1%-1.5% of graphite balls.

[0036] Further preferably, the scrap steel material is fed in three batches, the first batch of scrap steel accounts for 40%-48% of the total amount, and the graphite balls account for 0.5%-0.75% of the total amount; the second batch of scrap steel accounts for 36%-44% of the total amount, and the graphite balls account for 0.5%-0.75% of the total amount; and the third batch of scrap steel accounts for 8%-24% of the total amount, and the total amount of the three batches is 100%.

[0037] In view of the problem of excessively high ferrous oxide content in the slag of the electric arc furnace smelting scrap steel, the present application provides a smelting process for reducing the ferrous oxide content in the slag, which adjusts the electric arc furnace body structure by delaying oxygen feeding and adjusting the height / angle / distance from the molten pool of the oxygen lance, greatly improves the oxygen utilization rate, thereby reducing the ferrous oxide content in the slag and greatly reducing the iron loss, and does not prolong the smelting cycle, thereby reducing the smelting cost. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is an electric arc furnace cross-sectional view, wherein (100) is a lower furnace body of the electric arc furnace; (200) is an upper furnace body of the electric arc furnace; (300) is an oxygen lance; and (310) is a lance nozzle of the oxygen lance. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0040] Embodiment 1

[0041] The present embodiment provides a smelting process for reducing the ferrous oxide content in the slag, and the total amount of the steel and graphite balls used in the present embodiment is 88 t, and the specific smelting process is as follows:

[0042] Batching: 27 t of briquettes, 60 t of scrap steel, and 1000 kg of graphite balls;

[0043] Distributing: the first batch of scrap steel, 3.5 t of bottoming scrap steel, 500 kg of graphite balls distributed thereon, 10.6 t of scrap steel distributed thereon, 12 t of briquettes distributed thereon, and 10.8 t of scrap steel distributed thereon;

[0044] The second batch of scrap steel material: 3.5 tons of bottoming scrap steel, 500 kg of graphite balls distributed thereon, 9 tons of scrap steel distributed thereon, 11 tons of briquettes distributed thereon, and 9.7 tons of scrap steel distributed thereon;

[0045] The third batch of scrap steel material: 8 tons of bottoming scrap steel, 2 tons of briquettes distributed thereon, and 4.9 tons of scrap steel distributed thereon;

[0046] Step one, the first batch of scrap steel material is added into the electric arc furnace, arc power supply is started, the current is 45579 kA, and the voltage is 760 V; after 1.5 min, the through-hole power supply is started, the current is 42660 kA, and the voltage is 815 V; after 6 min, the oxygen lance is started, oxygen blowing preheating is performed, the nitrogen flow rate is 95 Nm³ / h, the oxygen flow rate is 70 Nm³ / h, oxygen combustion melting aid is performed after 60 s, the natural gas flow rate is 100 Nm³ / h, the oxygen flow rate is 280 Nm³ / h, when the melting rate of the first batch of scrap steel material is greater than or equal to 80%, oxygen blowing melting aid is performed, the natural gas flow rate is 70 Nm³ / h, the oxygen flow rate is 1500 Nm³ / h, at the same time, the melting power supply is started, the current is 41336 kA, and the voltage is 840 V; when the cumulative power consumption is 10500 kWh / t, 1.13 tons of lime is added, the carbon powder is sprayed in a point mode, the carbon powder flow rate is 0.8 kg / (min·t), the interval is 8 s, the slag is formed, and the power supply is stopped;

[0047] Step two, when the melting rate of the first batch of scrap steel material is 90%-95%, the second batch of scrap steel material is added, arc power supply is started, the current is 45579 kA, and the voltage is 760 V; after 2 min, the through-hole power supply is started, the current is 42660 kA, and the voltage is 815 V; after 5 min, the oxygen lance is started, oxygen blowing preheating is performed, the nitrogen flow rate is 95 Nm³ / h, the oxygen flow rate is 70 Nm³ / h, oxygen combustion melting aid is performed after 40 s, the natural gas flow rate is 100 Nm³ / h, the oxygen flow rate is 280 Nm³ / h, when the melting rate of the second batch of scrap steel material is greater than or equal to 80%, oxygen blowing melting aid is performed, the natural gas flow rate is 70 Nm³ / h, the oxygen flow rate is 1500 Nm³ / h, at the same time, the melting power supply is started, the current is 41336 kA, and the voltage is 840 V; when the cumulative power consumption is 20500 kWh / t, 0.72 tons of lime is added, the carbon powder is sprayed in a point mode, the carbon powder flow rate is 0.8 kg / (min·t), the interval is 7 s, the slag is formed, and the power supply is stopped;

[0048] Step three, when the second batch of scrap steel melting rate is 90%-95%, the third batch of scrap steel is added, the arc power supply is started, the current is 45579kA, the voltage is 760V, 1min later, the power supply is changed to the through-hole, the current is 42660kA, the voltage is 815V, 2min later, the oxygen lance is started, the oxygen blowing preheating is carried out, the nitrogen flow is 95Nm³ / h, the oxygen flow is 70Nm³ / h, 30s later, the oxygen combustion melting aid is carried out, the natural gas flow is 100Nm³ / h, the oxygen flow is 280Nm³ / h, when the third batch of scrap steel melting rate is greater than or equal to 90%, the oxygen blowing melting aid is carried out, the natural gas flow is 70Nm³ / h, the oxygen flow is 1500Nm³ / h, at the same time, the melting power supply is changed to the power supply, the current is 41336kA, the voltage is 840V, when the cumulative power consumption is 28800kWh / t, the carbon powder is sprayed, the carbon powder flow is 0.9kg / (min·t), the interval is 8s, and the smelting melt is obtained;

[0049] Step four, when the cumulative power consumption is 31000kWh / t, the melting power supply is changed to the heating power supply, the current is 38921kA, the voltage is 886V, the smelting melt is heated to 1580℃, before tapping, the oxygen supply intensity is reduced to the natural gas flow of 60Nm³ / h and the oxygen flow of 1300Nm³ / h, the carbon powder is sprayed in the intermittent mode, the carbon powder flow is 0.9kg / (min·t), the interval is 7s, when the molten steel temperature is 1620℃ and the composition is qualified, the tapping is organized, and the content of ferrous oxide in the slag when the tapping is detected is 13.42%;

[0050] The vertical height h of the center nozzle of the oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 180mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 200mm;

[0051] The vertical height h of the center nozzle of the oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 170mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 220mm;

[0052] The vertical height h of the center nozzle of the oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 150mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 260mm;

[0053] The vertical height h of the center nozzle hole of the No. 4 oxygen lance nozzle from the highest level of the lower furnace body of the electric arc furnace is 170 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 180 mm.

[0054] Example 2

[0055] The present example provides a smelting process for reducing the ferrous oxide content in slag. The total amount of steel material and microcrystalline block loaded in the present example is 86 t, and the specific smelting process is as follows:

[0056] Batching: briquettes 26 t, scrap steel 60 t and graphite balls 1000 kg;

[0057] Dressing: the first batch of scrap steel material, 3.5 t of bottoming scrap steel, 500 kg of graphite balls, 10.1 t of scrap steel, 11 t of briquettes, and 10.8 t of scrap steel;

[0058] The second batch of scrap steel material: 3.5 t of bottoming scrap steel, 500 kg of graphite balls, 10 t of scrap steel, 12 t of briquettes, and 8.2 t of scrap steel;

[0059] The third batch of scrap steel material: 7.5 t of bottoming scrap steel, 2 t of briquettes, and 5.4 t of scrap steel;

[0060] Step one, add the first batch of scrap steel material to the electric arc furnace, start the arc power supply, the current is 45579 kA, and the voltage is 760 V. After 1 min, switch to the through-hole power supply, the current is 42660 kA, and the voltage is 815 V. After 6 min, start the oxygen lance for preheating, the nitrogen flow rate is 95 Nm³ / h, the oxygen flow rate is 70 Nm³ / h, and after 60 s, oxygen combustion melting is carried out, the natural gas flow rate is 100 Nm³ / h, and the oxygen flow rate is 280 Nm³ / h. When the melting rate of the first batch of scrap steel material is ≥80%, oxygen melting is carried out, the natural gas flow rate is 70 Nm³ / h, the oxygen flow rate is 1500 Nm³ / h, and at the same time, the melting power supply is switched on, the current is 41336 kA, and the voltage is 840 V. When the cumulative power consumption is 10600 kWh / t, 1.1 t of lime is added, the carbon powder is sprayed in a point mode, the flow rate of the sprayed carbon powder is 0.8 kg / (min·t), the interval is 8 s, slagging is carried out, and the power supply is stopped.

[0061] Step two, when the first batch of scrap steel melting rate is 90%-95%, the second batch of scrap steel is added, the arc power supply is started, the current is 45579kA, the voltage is 760V, 1min later, the power supply is changed to the through-hole, the current is 42660kA, the voltage is 42660815V, 5min later, the oxygen lance is started, the oxygen preheating is carried out, the nitrogen flow is 95Nm³ / h, the oxygen flow is 70Nm³ / h, 40s later, the oxygen combustion melting aid is carried out, the natural gas flow is 100Nm³ / h, the oxygen flow is 280Nm³ / h, when the second batch of scrap steel melting rate is ≥80%, the oxygen melting aid is carried out, the natural gas flow is 70Nm³ / h, the oxygen flow is 1500Nm³ / h, at the same time, the melting power supply is changed, the current is 41336kA, the voltage is 840V, when the cumulative power consumption is 21000kWh / t, 0.7t of lime is added, the carbon powder is sprayed by the intermittent spraying, the carbon powder flow is 0.8kg / (min·t), the interval is 7s, the slag is made, and the power supply is stopped;

[0062] Step three, when the second batch of scrap steel melting rate is 90%-95%, the third batch of scrap steel is added, the arc power supply is started, the current is 45579kA, the voltage is 760V, 1min later, the power supply is changed to the through-hole, the current is 42660kA, the voltage is 815V, 2min later, the oxygen lance is started, the oxygen preheating is carried out, the nitrogen flow is 95Nm³ / h, the oxygen flow is 70Nm³ / h, 30s later, the oxygen combustion melting aid is carried out, the natural gas flow is 100Nm³ / h, the oxygen flow is 280Nm³ / h, when the third batch of scrap steel melting rate is ≥90%, the oxygen melting aid is carried out, the natural gas flow is 70Nm³ / h, the oxygen flow is 1500Nm³ / h, at the same time, the melting power supply is changed, the current is 41336kA, the voltage is 840V, when the cumulative power consumption is 28800kWh / t, the carbon powder is sprayed by the intermittent spraying, the carbon powder flow is 0.9kg / (min·t), the interval is 8s, and the smelting melt is obtained;

[0063] Step four, when the cumulative power consumption is 31500kWh / t, the melting power supply is adjusted to the temperature rising power supply, the current is 38921kA, the voltage is 886V, the smelting melt is heated to 1580℃, before tapping, the oxygen supply intensity is reduced to the natural gas flow of 60Nm³ / h and the oxygen flow of 1300Nm³ / h, the carbon powder is sprayed by the intermittent spraying, the carbon powder flow is 0.9kg / (min·t), the interval is 7s, when the molten steel temperature is 1620℃ and the composition is qualified, the tapping is organized, the power supply is stopped, and the detection shows that the content of ferrous oxide in the slag is 13.42% when tapping;

[0064] The vertical height h of the center nozzle hole of the No. 1 oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 170 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 190 mm.

[0065] The vertical height h of the center nozzle hole of the No. 2 oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 175 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 44°; and the horizontal distance s of the center nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 225 mm.

[0066] The vertical height h of the center nozzle hole of the No. 3 oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 155 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 44°; and the horizontal distance s of the center nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 260 mm.

[0067] The vertical height h of the center nozzle hole of the No. 4 oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 170 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 180 mm.

[0068] Example 3

[0069] The present example provides a smelting process for reducing the ferrous oxide content in slag. The total amount of steel material and microcrystalline block loaded in the present example is 90 t, and the specific smelting process is as follows:

[0070] Batching: briquettes 27 t, scrap steel 63 t and graphite balls 1000 kg;

[0071] Distributing: the first batch of scrap steel material, 4.5 t of bottoming scrap steel, 500 kg of graphite balls, 9.6 t of scrap steel, 12.7 t of briquettes, and 11.5 t of scrap steel;

[0072] The second batch of scrap steel material: 3.5 t of bottoming scrap steel, 500 kg of graphite balls, 10.3 t of scrap steel, 12.3 t of briquettes, and 9.7 t of scrap steel;

[0073] The third batch of scrap steel material: 7 t of bottoming scrap steel, 2 t of briquettes, and 5.9 t of scrap steel;

[0074] Step one, add the first batch of scrap steel into the electric arc furnace, start the arc power supply, the current is 45579kA, the voltage is 760V, after 1min, change to the through-hole power supply, the current is 42660kA, the voltage is 815kkAV, after 6min, start the oxygen lance, preheat by blowing oxygen, the nitrogen flow is 95Nm³ / h, the oxygen flow is 70Nm³ / h, after 60s, perform oxygen combustion melting aid, the natural gas flow is 100Nm³ / h, the oxygen flow is 280Nm³ / h, when the melting rate of the first batch of scrap steel is ≥80%, perform oxygen combustion melting aid, the natural gas flow is 70Nm³ / h, the oxygen flow is 1500Nm³ / h, at the same time, change to the melting power supply, the current is 840kkA, the voltage is 41336V, when the cumulative power consumption is 11000kWh / t, add 1.17t of lime, perform point-to-point injection of carbon powder, the carbon powder flow is 0.8kg / (min·t), the interval is 8s, slagging, stop the power supply;

[0075] Step two, when the melting rate of the first batch of scrap steel is 90%-95%, add the second batch of scrap steel, start the arc power supply, the current is 45579kA, the voltage is 760V, after 1min, change to the through-hole power supply, the current is 42660kA, the voltage is 815V, after 4min, start the oxygen lance, preheat by blowing oxygen, the nitrogen flow is 95Nm³ / h, the oxygen flow is 70Nm³ / h, after 40s, perform oxygen combustion melting aid, the natural gas flow is 100Nm³ / h, the oxygen flow is 280Nm³ / h, when the melting rate of the second batch of scrap steel is ≥80%, perform oxygen combustion melting aid, the natural gas flow is 70Nm³ / h, the oxygen flow is 1500Nm³ / h, at the same time, change to the melting power supply, the current is 41336kA, the voltage is 840V, when the cumulative power consumption is 21500kWh / t, add 0.73t of lime, perform point-to-point injection of carbon powder, the carbon powder flow is 0.8kg / (min·t), the interval is 7s, slagging, stop the power supply;

[0076] Step three, when the second batch of scrap steel melting rate is 90%-95%, the third batch of scrap steel is added, the arc power supply is started, the current is 45579kA, the voltage is 760V, 2min later, the power supply is changed to the through-hole, the current is 42660kA, the voltage is 815V, 1min later, the oxygen lance is opened, the oxygen blowing preheating is carried out, the nitrogen flow is 95Nm³ / h, the oxygen flow is 70Nm³ / h, 30s later, the oxygen combustion melting aid is carried out, the natural gas flow is 100Nm³ / h, the oxygen flow is 280Nm³ / h, when the third batch of scrap steel melting rate is greater than or equal to 90%, the oxygen blowing melting aid is carried out, the natural gas flow is 70Nm³ / h, the oxygen flow is 1500Nm³ / h, at the same time, the melting power supply is changed to, the current is 41336kA, the voltage is 840V, when the cumulative power consumption is 28800kWh / t, the carbon powder is sprayed, the carbon powder flow is 0.9kg / (min·t), the interval is 8s, and the smelting melt is obtained;

[0077] Step four, when the cumulative power consumption is 32000kWh / t, the melting power supply is adjusted to the heating power supply, the current is 38921kA, the voltage is 886V, the smelting melt is heated to 1580℃, before tapping, the oxygen supply intensity is reduced to the natural gas flow of 60Nm³ / h, the oxygen flow of 1300Nm³ / h, the carbon powder is sprayed by the intermittent spraying, the carbon powder flow is 0.9kg / (min·t), the interval is 7s, when the molten steel temperature is 1620℃ and the composition is qualified, the power supply is stopped, the tapping is organized, and the content of ferrous oxide in the slag when tapping is detected to be 14.52%;

[0078] The vertical height h of the center nozzle of the oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 175mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 200mm.

[0079] The vertical height h of the center nozzle of the oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 175mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 200mm.

[0080] The vertical height h of the center nozzle of the oxygen lance nozzle from the highest horizontal surface of the lower furnace body of the electric arc furnace is 175mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 43°; and the horizontal distance s of the center nozzle of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 200mm.

[0081] The vertical height h of the central injection hole of the No. 4 oxygen lance nozzle from the highest level of the lower furnace body of the electric arc furnace is 170 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 42°; and the horizontal distance s of the central injection hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 190 mm.

[0082] Comparative Example 1

[0083] The present comparative example provides a smelting process for reducing the content of ferrous oxide in slag, and the technical solutions of the remaining examples 1 are basically the same, except that the present comparative example uses the No. 1 oxygen lance nozzle, and the vertical height h of the central injection hole of the oxygen lance nozzle from the highest level of the lower furnace body of the electric arc furnace is 190 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 47°; and the horizontal distance s of the central injection hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 140 mm.

[0084] The vertical height h of the central injection hole of the No. 2 oxygen lance nozzle from the highest level of the lower furnace body of the electric arc furnace is 190 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 46°; and the horizontal distance s of the central injection hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 145 mm.

[0085] The vertical height h of the central injection hole of the No. 3 oxygen lance nozzle from the highest level of the lower furnace body of the electric arc furnace is 140 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 40°; and the horizontal distance s of the central injection hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 270 mm.

[0086] The vertical height h of the central injection hole of the No. 4 oxygen lance nozzle from the highest level of the lower furnace body of the electric arc furnace is 145 mm; the inclination angle θ of the central axis of the oxygen lance nozzle in the vertical direction is 46°; and the horizontal distance s of the central injection hole of the oxygen lance nozzle from the vertical inner wall of the upper furnace body of the electric arc furnace is 265 mm.

[0087] The content of ferrous oxide in the obtained slag is 21.07%

[0088] To further confirm the technical effects of the present application, the oxygen consumption and smelting cycle of Examples 1-3 and Comparative Example 1 are calculated, and the results are as follows: the average oxygen consumption of Examples 1-3 is 17.74 Nm3 / t, the average smelting cycle is 49.02 min / furnace, and the average smelting power consumption is 433.71 kWh / t; while the oxygen consumption of Comparative Example 1 is 21.38 Nm3 / t, the smelting cycle is 49.12 min / furnace, and the smelting power consumption is 435.39 kWh / t. It can be seen that the smelting process for reducing the content of ferrous oxide in slag provided by the present application not only reduces the content of ferrous oxide in slag, but also reduces the oxygen consumption, smelting cycle and smelting power consumption, greatly reduces the smelting cost, reduces the iron loss, and provides a new method for scrap steel utilization.

[0089] The above merely describes preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A smelting process for reducing the ferrous oxide content in slag, characterized in that: Includes the following steps: Step 1: Add the first batch of scrap steel into the electric arc furnace, power on, turn on the oxygen lance after 6-7 minutes for oxygen preheating, and then perform oxygen combustion to assist melting after 50-70 seconds. When the melting rate of the first batch of scrap steel is ≥80%, continue oxygen blowing to assist melting. When the cumulative power consumption is 10000-11000kWh / t, add the first batch of lime, inject carbon powder, slag formation, and then stop power supply. Step 2: When the melting rate of the first batch of scrap steel is 90%-95%, add the second batch of scrap steel, power on, and turn on the oxygen lance after 5-6 minutes for oxygen preheating. After 30-50 seconds, perform oxygen combustion to assist melting. When the melting rate of the second batch of scrap steel is ≥80%, perform oxygen blowing to assist melting. When the cumulative power consumption is 20500-21500kWh / t, add the second batch of lime, inject carbon powder, slag formation, and stop power supply. Step 3: When the melting rate of the second batch of scrap steel is 90%-95%, add the third batch of scrap steel, power on, and turn on the oxygen lance for oxygen preheating after 1-3 minutes. After 20-40 seconds, perform oxygen combustion to assist melting. When the melting rate of the third batch of scrap steel is ≥90%, perform oxygen blowing to assist melting and inject carbon powder to obtain the smelting melt. Step 4: When the cumulative power consumption is 31000-32000 kWh / t, heat the smelting melt to ≥1580℃, inject carbon powder, and when the steel temperature is ≥1610℃ and the composition is qualified, stop the power supply and organize the tapping of steel. Wherein, the vertical height h of the center nozzle of the oxygen lance from the highest horizontal plane of the lower furnace body of the electric arc furnace is 150-180mm; the tilt angle θ of the central axis of the oxygen lance in the vertical direction is 41°-45°; the horizontal distance s of the center nozzle of the oxygen lance from the vertical inner wall of the upper furnace body of the electric arc furnace is 150-260mm; in steps one to four, the oxygen lance includes oxygen lance No. 1, oxygen lance No. 2, oxygen lance No. 3 and oxygen lance No. 4; The vertical height h of the center nozzle of oxygen lance No. 1 from the highest horizontal plane of the lower furnace body of the electric arc furnace is 160-180mm; the tilt angle θ of the central axis of oxygen lance No. 1 along the vertical direction is 43°-44°; and the horizontal distance s of the center nozzle of oxygen lance No. 1 from the vertical inner wall of the upper furnace body of the electric arc furnace is 170-200mm. The vertical height h of the center nozzle of oxygen lance No. 2 from the highest horizontal plane of the lower furnace body of the electric arc furnace is 160-175mm; the tilt angle θ of the central axis of oxygen lance No. 2 along the vertical direction is 43°-44°; the horizontal distance s of the center nozzle of oxygen lance No. 2 from the vertical inner wall of the upper furnace body of the electric arc furnace is 220-230mm. The vertical height h of the center nozzle of oxygen lance No. 3 from the highest horizontal plane of the lower furnace body of the electric arc furnace is 150-155mm; the tilt angle θ of the central axis of oxygen lance No. 3 along the vertical direction is 42°-44°; the horizontal distance s of the center nozzle of oxygen lance No. 3 from the vertical inner wall of the upper furnace body of the electric arc furnace is 250-260mm. The vertical height h of the center nozzle of oxygen lance No. 4 from the highest horizontal plane of the lower furnace body of the electric arc furnace is 165-175mm; the tilt angle θ of the central axis of oxygen lance No. 4 along the vertical direction is 41°-43°; and the horizontal distance s of the center nozzle of oxygen lance No. 4 from the vertical inner wall of the upper furnace body of the electric arc furnace is 170-190mm.

2. The smelting process for reducing the ferrous oxide content in slag as described in claim 1, characterized in that: In step one, the amount of lime added in the first batch is 3%-4% of the mass of the first batch of scrap steel.

3. The smelting process for reducing the ferrous oxide content in slag as described in claim 1, characterized in that: In step two, the amount of the second batch of lime added is 2%-3% of the mass of the second batch of scrap steel.

4. The smelting process for reducing the ferrous oxide content in slag as described in claim 1, characterized in that: The power supply includes arc-starting power supply, well-penetration power supply, melting power supply and heating power supply; the first and second batches of scrap steel are powered by arc-starting power supply, well-penetration power supply and melting power supply; the third batch of scrap steel is powered by arc-starting power supply, well-penetration power supply, melting power supply and heating power supply.

5. The smelting process for reducing the ferrous oxide content in slag as described in claim 4, characterized in that: The arc-starting power supply current is 45569-45589kA, and the voltage is 755-770V; and / or The well penetration power supply current is 42650-42670kA, and the voltage is 807-822V; and / or The melting power supply current is 41326-41346kA, and the voltage is 833-848V; and / or The heating power supply current is 38911-38931kA, and the voltage is 885-900V.

6. The smelting process for reducing the ferrous oxide content in slag as described in any one of claims 4 or 5, characterized in that: The duration of the arc-starting power supply is 1-2 minutes; and / or The duration of the well-penetration power supply is 6-9 minutes; and / or The duration of the melting power supply is 3-4 minutes.

7. The smelting process for reducing the ferrous oxide content in slag as described in claim 1, characterized in that: In steps one through three, the nitrogen flow rate of the oxygen lance during oxygen preheating is 90-100 Nm³ / h, and the oxygen flow rate is 65-75 Nm³ / h.

8. The smelting process for reducing the ferrous oxide content in slag as described in claim 1, characterized in that: In steps one through three, the natural gas flow rate of the oxygen lance during oxy-fuel melting is 95-105 Nm³ / h, and the oxygen flow rate is 275-285 Nm³ / h; and / or In steps one through three, the natural gas flow rate of the oxygen lance during oxygen blowing for fusion is 65-75 Nm³ / h, and the oxygen flow rate is 1490-1510 Nm³ / h.

9. The smelting process for reducing the ferrous oxide content in slag as described in claim 1, characterized in that: In steps one through four, the injected toner is applied using a jog-type injection method, with a flow rate of 0.7-1.0 kg / (min·t) and an interval of 7-9 seconds.

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