CN113699308B - Primary combustion auxiliary heating electric arc furnace steelmaking equipment and method - Google Patents
Primary combustion auxiliary heating electric arc furnace steelmaking equipment and method Download PDFInfo
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- CN113699308B CN113699308B CN202111098608.9A CN202111098608A CN113699308B CN 113699308 B CN113699308 B CN 113699308B CN 202111098608 A CN202111098608 A CN 202111098608A CN 113699308 B CN113699308 B CN 113699308B
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 93
- 238000010438 heat treatment Methods 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000009845 electric arc furnace steelmaking Methods 0.000 title claims abstract description 18
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 218
- 239000010959 steel Substances 0.000 claims abstract description 218
- 238000010891 electric arc Methods 0.000 claims abstract description 74
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 65
- 239000003546 flue gas Substances 0.000 claims abstract description 53
- 239000007789 gas Substances 0.000 claims abstract description 48
- 239000002699 waste material Substances 0.000 claims abstract description 40
- 239000000779 smoke Substances 0.000 claims abstract description 26
- 239000000463 material Substances 0.000 claims abstract description 24
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- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 51
- 229910052760 oxygen Inorganic materials 0.000 claims description 27
- 239000001301 oxygen Substances 0.000 claims description 27
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 26
- 230000008569 process Effects 0.000 claims description 17
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 12
- 238000007599 discharging Methods 0.000 claims description 11
- 230000000903 blocking effect Effects 0.000 claims description 10
- 239000002737 fuel gas Substances 0.000 claims description 9
- 238000002347 injection Methods 0.000 claims description 9
- 239000007924 injection Substances 0.000 claims description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 239000000428 dust Substances 0.000 claims description 8
- 230000007613 environmental effect Effects 0.000 claims description 6
- 210000000621 bronchi Anatomy 0.000 claims description 5
- 230000003647 oxidation Effects 0.000 claims description 5
- 238000007254 oxidation reaction Methods 0.000 claims description 5
- 238000010079 rubber tapping Methods 0.000 claims description 5
- 238000001514 detection method Methods 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 239000000567 combustion gas Substances 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims description 2
- 238000007906 compression Methods 0.000 claims description 2
- 238000005520 cutting process Methods 0.000 claims description 2
- 238000009628 steelmaking Methods 0.000 claims 2
- 229910052799 carbon Inorganic materials 0.000 abstract description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 5
- 238000001816 cooling Methods 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 4
- 230000008901 benefit Effects 0.000 abstract description 3
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- 239000000155 melt Substances 0.000 abstract 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 12
- 238000003723 Smelting Methods 0.000 description 10
- 239000003245 coal Substances 0.000 description 9
- 239000000446 fuel Substances 0.000 description 7
- 230000005611 electricity Effects 0.000 description 6
- 238000000462 isostatic pressing Methods 0.000 description 6
- 239000003345 natural gas Substances 0.000 description 6
- HGUFODBRKLSHSI-UHFFFAOYSA-N 2,3,7,8-tetrachloro-dibenzo-p-dioxin Chemical compound O1C2=CC(Cl)=C(Cl)C=C2OC2=C1C=C(Cl)C(Cl)=C2 HGUFODBRKLSHSI-UHFFFAOYSA-N 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 4
- 230000035699 permeability Effects 0.000 description 4
- 239000002893 slag Substances 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000000571 coke Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- FMMWHPNWAFZXNH-UHFFFAOYSA-N Benz[a]pyrene Chemical compound C1=C2C3=CC=CC=C3C=C(C=C3)C2=C2C3=CC=CC2=C1 FMMWHPNWAFZXNH-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
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- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
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- 230000008859 change Effects 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
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- 229910052751 metal Inorganic materials 0.000 description 2
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- 230000036284 oxygen consumption Effects 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 1
- 239000003830 anthracite Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000002817 coal dust Substances 0.000 description 1
- 239000003034 coal gas Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
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- 229910052742 iron Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 125000000864 peroxy group Chemical group O(O*)* 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
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- 230000002035 prolonged effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
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- 239000002918 waste heat Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/56—Manufacture of steel by other methods
- C21C5/562—Manufacture of steel by other methods starting from scrap
- C21C5/565—Preheating of scrap
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C2100/00—Exhaust gas
- C21C2100/04—Recirculation of the exhaust gas
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Furnace Details (AREA)
- Vertical, Hearth, Or Arc Furnaces (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
The invention relates to a primary combustion auxiliary heating electric arc furnace steelmaking device and a method, which belong to the technical field of metallurgy, wherein primary energy combustion in an electric arc furnace is selected to be added to supplement heat energy, primary energy is adopted to replace secondary energy so as to obtain greater carbon reduction benefit, waste steel blanking and flue gas are adopted to enter a shaft furnace for split passage through the improvement of the device, the waste steel blanking passage does not walk flue gas, and the flue gas singly enters the shaft furnace through a flue. For uniform gas distribution, the shaft furnace adopts an annular flue manifold to enter the furnace. The first layer of manipulator that causes because of traditional steel scrap heating adopts flue gas entering passageway and steel scrap unloading passageway sharing bears the temperature height, and the material is difficult to select, adopts the water-cooling to cause the potential safety hazard, and melts the steel scrap and easily causes the technical problem that the manipulator bonds. Comprehensively realize the effects of emission reduction and cost reduction, and ensure that the smoke emission completely reaches the standard while reducing the burning loss of steel materials.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to one-time combustion auxiliary heating electric arc furnace steelmaking equipment and a method.
Background
China is the first major country of steel production in the world, and is mainly a long process. The carbon emission of the long-flow steel smelting process is far greater than that of the short-flow electric arc furnace smelting process, so that the long-flow is limited gradually in the future development of China, and the short-flow development is encouraged. However, the main electric power in China is still from thermal power, the energy utilization rate is low through secondary energy conversion, the energy conversion rate of thermal power generation is only about 40%, the emission is still large, and the waste heat utilization of the furnace gas of many traditional electric arc furnaces is poor, so that the electricity consumption is high, the comprehensive carbon emission is still high, and therefore, the development of a low-carbon energy-saving short-flow technology is required, and the energy utilization rate is improved.
At present, the electric arc furnace is also provided with a coal injection gun, but the aim is to produce foam slag; oxygen lances are also provided to speed up scrap melting and heating, but at the cost of steel burn-out. Therefore, the yield of the scrap steel metal is only about 90 percent.
At present, the treatment of a plurality of waste steel preheating tail gases also has problems, and sulfur, nitrate and dioxin are not treated, so that the emission exceeds the standard. The flue gas temperature fluctuation of the electric arc furnace is too large, and the current flue gas treatment technology cannot adapt to the flue gas of the electric arc furnace.
In order to solve the problems, a low-carbon environment-friendly electric arc furnace smelting process and equipment are developed. Can obtain good energy-saving, low-carbon and environment-friendly effects.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides primary combustion auxiliary heating electric arc furnace steelmaking equipment and a primary combustion auxiliary heating electric arc furnace steelmaking process, wherein primary energy combustion in an electric arc furnace is selected to supplement heat energy, primary energy is adopted to replace secondary energy, so that greater carbon reduction benefits are obtained, and fuel selection such as coal or fuel gas is determined according to local resource conditions. Conventional scrap heating is typically common to the flue gas inlet channel and the scrap discharge channel. This can result in the first layer of manipulator being subjected to high temperatures and materials being difficult to select. Water cooling is adopted, so that potential safety hazards can be caused. And simultaneously, the molten scrap steel is easy to cause the bonding of the mechanical arm. For this purpose, we adopt scrap steel blanking and flue gas entering the shaft furnace for split passage. Namely, the waste steel discharging channel does not go away with the flue gas, and the flue gas independently enters the shaft furnace through the flue. For uniform gas distribution, the shaft furnace adopts an annular flue manifold to enter the furnace.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the primary combustion auxiliary heating electric arc furnace steelmaking equipment comprises an electric arc furnace and a scrap steel preheating shaft furnace which are connected, wherein a smoke exhaust pipe is arranged above the electric arc furnace, and the smoke exhaust pipe is connected with the scrap steel preheating shaft furnace.
Due to the defects of low geometric dimension, low height and small space of the electric arc furnace, the heat exchange time of the combustion furnace gas is short, and the heat of combustion cannot be fully utilized, which is the root cause for restricting the combustion in the electric arc furnace. Therefore, the waste steel preheating shaft furnace is added behind the electric arc furnace, so that the escaped high-temperature flue gas heats the waste steel, and the exhaust gas temperature is reduced and the energy utilization rate is improved through heat exchange with the waste steel.
The temperature of the scrap steel entering the furnace is increased through preheating the scrap steel, the melting time of the scrap steel is shortened, the smelting period is shortened, and the consumption of secondary energy sources and electricity is reduced.
The furnace wall of the electric arc furnace is uniformly provided with a plurality of strong reducing gas nozzles at intervals above the axial direction, and a plurality of oxygen coal guns/oxygen burning guns at intervals below the axial direction.
The waste steel preheating shaft furnace comprises an upper vertical channel and a bottom inclined blanking channel, and is arranged obliquely above the electric arc furnace and connected through the inclined blanking channel.
The bottom of the scrap steel preheating shaft furnace is provided with a rotary flap valve and is matched with a locking bolt.
The vertical section channel of the scrap steel preheating shaft furnace is an N-section preheating channel, and specifically comprises a first-layer scrap steel preheating section, a second-layer scrap steel preheating section, …, an N-layer scrap steel preheating section and N=2-4 from bottom to top.
The vertical section channel of the scrap steel preheating shaft furnace is sequentially provided with a first layer of mechanical arm, a second layer of mechanical arm, … th layer of mechanical arm and an N-1 th layer of mechanical arm from bottom to top, a layer of scrap steel preheating section is formed between the rotary flap valve and the first layer of mechanical arm, a two-layer scrap steel preheating section is formed between the second layer of mechanical arm and the first layer of mechanical arm, … is formed between the second layer of mechanical arm and the first layer of mechanical arm, and N layers of scrap steel preheating sections are formed above the N-1 th layer of mechanical arm.
The device is characterized in that an annular flue is arranged at the bottom of the side wall of the N-layer steel scrap preheating section, a two-layer steel scrap preheating section and a … -1-layer steel scrap preheating section in an N-section preheating channel of the shaft furnace section of the steel scrap preheating shaft furnace, one end of the annular flue is connected with the steel scrap preheating shaft furnace through a bronchus, and the other end of the annular flue is connected with a smoke exhaust pipe.
The smoke exhaust pipe/connecting flue connected with the annular flue at the bottom of the side wall of the layer 2 scrap steel preheating section is provided with a high-temperature resistant material valve, and a secondary combustion chamber is arranged between the high-temperature resistant material valve and the layer of annular flue.
The mechanical arms of each layer are used for supporting the scrap steel, so that the static pressure of the scrap steel layer of the shaft furnace to the lower scrap steel is too high to avoid the deterioration of air permeability, and meanwhile, the mechanical arms of each layer are arranged in the scrap steel preheating shaft furnace to heat the scrap steel layer by layer for the convenience of discharging. The number of layers is designed according to the capacity of the electric arc furnace, the variety of common scrap steel and the bearing capacity of the manipulator. The layered preheating process of the scrap steel is described by taking three layers as an example as follows: in the running process of the equipment, the first layer of scrap steel falls on the rotary flap valve at the bottom of the furnace, the second layer of scrap steel is supported by the first layer of mechanical arm, the third layer of scrap steel is supported by the second layer of mechanical arm, the amount of each layer of scrap steel is designed according to one half of the loading amount of an electric arc furnace, and each layer of scrap steel is added in two times.
The secondary combustion section is arranged between the first layer of mechanical arm and the first layer of scrap steel material top, and the secondary combustion section is matched with a combustion-supporting gas injection system.
A combustion-supporting gas nozzle is arranged between the first layer of scrap steel top and the second layer of scrap steel bottom, a small oxygen burning gun is arranged at the combustion-supporting gas nozzle and used as an igniter, and the position of the oxygen burning gun is far away from a manipulator as far as possible.
When the lower scrap steel is heated to a softening temperature, the resistance of the whole shaft furnace system can be increased due to the increase of the softening deformation density of the scrap steel, and when the resistance reaches a set limit value, the control system starts to open a high-temperature-resistant refractory valve on the connecting flue, so that most of the flue gas can directly enter the second scrap steel area. Because the flue gas does not pass through the secondary combustion section in the furnace, a secondary combustion chamber is arranged before the flue gas enters the upper annular flue after the refractory valve, unburned fuel gas is combusted in the secondary combustion chamber before the flue gas enters the upper annular flue, the peroxy coefficient is controlled, and the waste steel oxidation is avoided.
The injection quantity of the combustion-supporting gas of the secondary combustion section is controlled by the concentration of the carbon monoxide at the furnace top, the concentration of the carbon monoxide at the furnace top is injected until the concentration of the carbon monoxide at the furnace top does not exceed the local environment-friendly emission standard, and a carbon monoxide detector is arranged at the furnace top of the scrap steel preheating shaft furnace to obtain the concentration of the carbon monoxide at the furnace top at any time.
The height of each layer of scrap steel preheating section of the vertical section of the scrap steel preheating shaft furnace is designed according to the adding amount of each scrap steel required by the process, the change of the density of the scrap steel and the change of the bulk density caused by blanking are fully considered, the phenomenon that equipment cannot normally operate due to material expansion is avoided, and the scrap steel is relatively stable.
The inclined blanking channel is provided with a refractory sealing and blocking valve to prevent high-temperature damage to equipment at the bottom of the scrap steel preheating shaft furnace caused by gas cross of the inclined blanking channel and radiant heat of the electric arc furnace.
The furnace top of the scrap steel preheating shaft furnace is provided with a charging isostatic pressure chamber, the side wall of the furnace top is connected with a shaft furnace smoke exhaust pipeline, the shaft furnace smoke exhaust pipeline is sequentially provided with a pipeline reactor, a dust remover, an induced draft fan and a chimney, an inlet of the induced draft fan is provided with a gas release valve, and the chimney is designed to be reasonable in height according to local environmental requirements.
A gap is arranged between the scrap steel inclined blanking channel and the electric arc furnace body and is sealed by a sealing system; the gap is arranged between the smoke exhaust pipe and the electric arc furnace body, and the smoke exhaust pipe is sealed by the hydraulic sealing ring, so that the electric arc furnace can conveniently perform rotating operations such as tapping, slag discharging and the like, when the electric arc furnace needs tilting, the sealing system is opened, and the tilting operation of the electric arc furnace can be freely realized.
A moving gap is reserved between the inclined blanking channel of the scrap steel preheating shaft furnace and the charging port of the electric arc furnace, the inclined blanking channel is in closed connection by a sealing system, and a refractory sealing and blocking valve is arranged in the middle of the inclined blanking channel.
When the device is designed for a three-layer preheating section, a lower annular flue is arranged at a position 300-600mm above the rotary flap valve and is connected with the shaft furnace through a bronchus, so that high-temperature damage to furnace bottom equipment caused by high-temperature flue gas is avoided, bonding of the furnace bottom equipment caused by melting of a small amount of scrap steel is avoided, and the specific distance is determined according to the flue gas temperature, the flue gas amount, the smelting period and the scrap steel type. Arranging a first layer of manipulator at 200-300mm above the highest position of the designed first layer of scrap steel; an annular flue is arranged on the first layer of manipulator by 200-400mm and is connected with the inside of the shaft furnace by a bronchus; calculating the top height of the second layer of scrap steel according to the selected scrap steel bulk density and the sectional area of the furnace, and setting a second layer of mechanical arm at a certain safety distance to hold Fu Di three layers of scrap steel; according to the height of the third layer of scrap steel, the discharging mechanism is considered to be required to be provided with a charging isostatic pressing chamber at the top of the scrap steel preheating shaft furnace; the feeding isostatic pressing chamber is provided with an upper sealing plate and a lower sealing plate.
The primary combustion auxiliary heating electric arc furnace steelmaking process adopts the equipment and comprises the following steps:
(1) In the operation process of the electric arc furnace, high-temperature flue gas is obtained, the flue gas is communicated with a layer of waste steel preheating section-N-1 layer of waste steel preheating section through a flue gas exhaust pipe, waste steel is added to different preheating sections in the waste steel preheating shaft furnace in batches, the lower layer of flue gas is continuously upwards to heat the layer of waste steel, finally the flue gas is cooled to 80-150 ℃ after heat exchange with the waste steel, and is exhausted from a flue gas outlet of the shaft furnace, and power is derived from a rear induced draft fan.
(2) After the whole equipment runs stably, strong reducing fuel gas is blown into the electric arc furnace through a nozzle at the upper part of the electric arc furnace, nitrogen oxides generated by electric arc and lower oxygen burning guns are reduced and removed, and the nitrogen oxides are burnt with the lower oxygen burning guns by excessive oxygen, so that the oxygen oxidability is reduced, and the steel scrap burning loss is reduced. Unreacted reducing gas is burned in a secondary combustion section or a secondary combustion chamber.
(3) When the heating temperature of the first layer of waste steel reaches a reflow point, the compression density of the bottom waste steel is increased, the system resistance is rapidly increased, when the design limit value is reached, a high-temperature resistant refractory valve in front of a secondary combustion chamber is started, most smoke can directly enter an upper annular flue to directly heat the second layer and the waste steel above, a combustion air system of the secondary combustion chamber is started at the same time when the valve is started, the combustion air system is shared with a combustion air system of a secondary combustion section in a shaft furnace, a switching valve is arranged, and the combustion air quantity is simultaneously controlled by the concentration of carbon monoxide detected by a smoke detection system of a smoke outlet of the shaft furnace;
(4) Before tapping of the electric arc furnace, stopping the oxygen burning gun and the strong reduction gas injection, stopping the induced draft fan, or opening to the lowest gear, and arranging an air inlet valve in front of the induced draft fan to avoid oxidation of the scrap steel caused by air entering the scrap steel preheating shaft furnace system. Frequent adjustment of the frequency conversion system is avoided. Opening a sealing system between the scrap steel discharging channel and the flue gas channel and the electric arc furnace body, tilting the furnace body to discharge steel;
(5) After steel is discharged, a sealing system between a steel scrap discharging channel and a flue gas channel and an electric arc furnace body is closed, a refractory sealing plate of the steel scrap discharging channel is opened, a rotary flap valve of the bottom of a steel scrap preheating shaft furnace is pulled out for cutting, the rotary flap valve is started, steel scrap falls into the electric arc furnace, and steel scrap is reserved for reducing impact of steel scrap on the bottom of the electric arc furnace;
(6) After the addition of the scrap steel is completed, closing a rotary flap valve, inserting a bolt, recovering the refractory sealing and blocking valve to a protection state, withdrawing the first layer of mechanical arm, placing the second layer of scrap steel to the furnace bottom, recovering the first layer of mechanical arm to a supporting state, withdrawing the second layer of mechanical arm, placing the third layer of scrap steel to the first layer of mechanical arm, and recovering the second layer of mechanical arm to the supporting state; and (5) completing the whole process.
In the step (1), nitrogen oxides in the flue gas of the electric arc furnace are reduced into nitrogen and removed.
In the step (1), the arc temperature of the arc furnace is extremely high, and air brought by raw materials and air entering the furnace due to the fact that the furnace is not tightly sealed can be oxidized to generate nitrogen oxides in a high-temperature environment. Post combustion in the furnace also produces nitrogen oxides. The temperature fluctuation of the flue gas of the electric arc furnace is too large, and a proper section is difficult to find for conventional flue gas denitration. Therefore, the flue gas of the current arc furnace is not subjected to flue gas denitration. In order to solve the problem, the strong reducing agent reduction method is adopted for denitration, and strong reducing gas is injected into the electric arc furnace through a strong reducing gas nozzle at the upper part in the electric arc furnace. Such as natural gas, coke oven gas, etc. Under the high-temperature environment, the nitrogen oxides can be quickly reduced into nitrogen by the gas with strong reducibility so as to be removed.
In the step (1), the charging isostatic pressure chamber at the top of the scrap steel preheating shaft furnace is specifically opened when scrap steel is added into the charging isostatic pressure chamber, the upper sealing plate is closed after the scrap steel is added, and the lower sealing plate is opened when the scrap steel is added into the scrap steel preheating shaft furnace, so that the pressure of the top of the furnace is not relieved.
In the step (1), when the second layer of mechanical arm is restored to the supporting state, the lower sealing plate of the isostatic pressing chamber is opened, after the scrap steel falls to the second layer of mechanical arm, the lower sealing plate is restored to the sealing state, the upper sealing plate can be continuously opened, the isostatic pressing chamber is charged, and after the scrap steel is added, the upper sealing plate is closed, so that the sealing of the furnace top is enhanced.
In the step (2), residual unburnt reducing gas enters the shaft furnace, and waste steel oxidation in a high temperature area of the shaft furnace is avoided due to the existence of excessive reducing gas. Air is blown into the shaft furnace in the temperature range of 550-800 ℃ for secondary combustion. The fuel gas at the temperature has combustion conditions, and the scrap steel is not easy to oxidize.
In the step (2), the oxygen-coal gun or the oxygen-combustion gun of the electric arc furnace selects fuel according to the local resource advantage, the gas with strong reducibility is natural gas or coke oven gas, and the like, if the selected gas is natural gas or coke oven gas, the aim of controlling nitrogen oxides can be achieved by adjusting the oxygen-combustion ratio of combustion in the furnace, so that the nozzle with strong reducibility can be canceled; when coal is selected as fuel, low sulfur, low phosphorus and low ash content are selected as much as possible, and the influence of ash content on slag alkalinity and harmful components is considered when an electric arc furnace is used for slagging.
In the step (2), as primary combustion is added, sulfur in flue gas is increased, and the flue gas needs to be treated, and as paint and grease substances are arranged on waste steel, harmful gases such as dioxin, benzopyrene and the like are generated during preheating, a surface active adsorption material is sprayed into a pipeline reactor, so that dioxin and benzopyrene are desulfurized and removed; the dust remover is used for capturing surface active substances sprayed by the pipeline reactor and dust of the shaft furnace system; the induced draft fan is used for providing running power for the whole system, and a proper fan is selected according to the resistance and the smoke quantity of the whole system. The control information of the induced air intensity of the fan comes from a pressure sensor of the electric arc furnace and is controlled to be micro negative pressure or micro positive pressure in the furnace. Controlling according to smelting process requirements; the treated flue gas is discharged through a chimney after reaching the standard, and the surface active adsorption material is activated carbon powder.
In the step (2), an induced draft fan is selected and designed according to the flue gas resistance and the flue gas amount of the whole system, and a variable frequency motor is selected by an induced draft fan motor. The variable frequency fan is controlled to keep the micro negative pressure point of the arc furnace mouth, and because the excessive fuel gas exists in the furnace, the atmosphere in the furnace is not destroyed by less air entering a point, so that the leakage of the furnace gas can be avoided.
In the step (2), a secondary combustion process is adopted, namely combustion with a low oxygen combustion ratio is adopted in a hearth, furnace gas is reduced, high-temperature burning loss of preheated scrap steel is reduced, if the fuel is solid carbonaceous fuel, part of strong reducing fuel gas can be supplemented and blown at the upper part of the electric arc furnace, nitrogen oxides in the flue gas are reduced, unburned carbon monoxide and the supplemented and blown strong reducing fuel gas are subjected to blast secondary combustion in an empty section between the top of the first layer of scrap steel material and the second layer of scrap steel. The secondary combustion section is provided with a small-sized normal-combustion oxygen combustion gun for ignition. Because of the low temperatures at this point, the amount of steel burned for post combustion is small and the temperature burns substantially no nitrogen oxides are produced by combustion.
In the step (2), the sectional heating of the scrap steel is realized by the cooperation of the refractory sealing and blocking valve and the secondary combustion chamber, so that the overall temperature of the scrap steel is improved. Because the heating temperature of the bottom scrap steel cannot be too high, otherwise, the scrap steel can be softened and adhered, the air permeability of the shaft furnace is affected, and the temperature of the upper scrap steel cannot be heated too high due to the limitation of the temperature rise of the lower part. The problem that the smoke exhaust system cannot work due to the increase of system resistance caused by the fact that the preheating time of scrap steel is prolonged when smelting is abnormal can also be solved. According to the principle, a method of using a plurality of secondary combustion chambers for each layer of small batch of scrap steel can be adopted, so that the whole preheating temperature of the scrap steel is improved.
In the step (2), a secondary combustion process is adopted, the atmosphere below the secondary combustion section is a reducing atmosphere, and if the preheated scrap steel is a crushed material with high zinc content, part of flue gas is led out for zinc recovery before secondary combustion.
In the step (2), a secondary combustion process is adopted, the flue gas in front of the secondary combustion section is in a reducing atmosphere, nitrogen oxides generated by electric arc high temperature in the furnace and nitrogen oxides generated during combustion are reduced into nitrogen, the upper secondary combustion temperature is lower, nitrogen oxides are not generated any more, and therefore the nitrogen oxides of the flue gas can be controlled to be very low. Solves the problem that the oxygen of the electric arc furnace cannot be denitrated.
In the step (2), the whole equipment is operated initially, and the secondary combustion cannot be realized because the temperature of the whole system is low and the temperature of the secondary combustion section is low, so that the oxygen ratio is properly increased without blowing strong reducing gas, and the carbon monoxide concentration of the discharged flue gas is ensured to reach the standard. Because the scrap temperature is low at this point, scrap burn-out is not severe. Avoiding the escape of fuel gas; a small-sized normal-combustion oxygen burning gun is arranged in the secondary combustion section to play a role in ignition and combustion supporting; the secondary combustion air is sprayed into the carbon monoxide concentration detected by a smoke detection system at the smoke outlet of the shaft furnace with controlled quantity; when the equipment enters normal operation, starting to spray strong reducing gas.
In the step (4), when the coal injection, the air injection and the tapping are stopped in the electric arc furnace, in order to prevent the waste steel preheating system from sucking air, the rotating speed of the variable frequency fan can be reduced to be very low or the induced air is stopped, the variable frequency fan is not suitable for being frequently stopped and started, and in order to conveniently regulate and control the induced air pressure of the shaft furnace, a bleed valve is arranged on a pipeline between the dust remover and the induced draft fan, so that the frequent starting of the frequency modulation fan is avoided.
In the process, the first layer of manipulator adopts air cooling. Because the secondary combustion gas quantity is small, the general temperature is not too high, the air cooling can be satisfied, and water cooling is preferably not needed;
The loading system of scrap steel considers the problem of material leakage caused by supporting of a manipulator, and simultaneously also considers the problem of air permeability of an air inlet part of an annular flue, so that broken materials and light and thin materials with poor air permeability are not required to be loaded.
The invention has the beneficial effects that:
the process solves the denitration problem by two-step combustion, reduces the burning loss of the steel scraps, obviously improves the integral charging temperature of the steel scraps by adding a secondary combustion heat source, solves the problems of rapid increase of system resistance and even incapability of running of the system caused by high preheating temperature of the steel scraps, comprehensively realizes the effects of emission reduction and cost reduction, reduces the burning loss of the steel scraps, and ensures that the fume emission completely reaches the standard.
Drawings
FIG. 1 is a schematic view of a primary combustion auxiliary heating electric arc furnace steelmaking apparatus according to embodiment 1 of the present invention, wherein:
The device comprises a 1-electric arc furnace, a 2-scrap steel preheating square shaft furnace, a 3-connecting flue, a 4-oxygen coal gun, a 5-strong reducing gas nozzle, a 6-hydraulic sealing system, a 7-refractory sealing and blocking valve, an 8-split rotary plate valve, a 9-1 lower annular flue, a 9-2 upper annular flue, a 10-1 first layer manipulator, a 10-2 second layer manipulator, an 11-hydraulic sealing ring, a 12-refractory valve, a 13-secondary combustion chamber, a 14-charging isostatic pressing chamber, a 15-pipeline reactor, a 16-dust remover 16, a 17-induced draft fan, an 18-chimney and a 19-air release valve.
Detailed Description
Example 1
A75-ton ultrahigh-power electric arc furnace is arranged in a short-flow steel plant of an electric arc furnace, and a ladle oxygen burning gun is arranged to heat scrap steel in order to reduce cost and improve productivity. The heat efficiency is less than 40%, the burning loss of the scrap steel is more than 11%, and the flue gas only has dust removal and the sulfur, the nitrate and the dioxin exceed the standards. Because the environmental protection can not reach the standard, the system is shut down by the local environmental protection department. Because no scrap steel is heated, the smelting period cannot meet the requirement of continuous casting procedures, and a casting breaking phenomenon frequently occurs, so that the cost is increased. In order to solve the problem of scrap steel preheating, the technology and the equipment are adopted.
The primary combustion auxiliary heating electric arc furnace steelmaking equipment has a structure schematic diagram shown in fig. 1: four oxygen coal guns 4 and two natural gas nozzles 5 are arranged on the furnace wall of a 75-ton electric arc furnace 1, a waste steel preheating square shaft furnace 2 is built above the side of the electric arc furnace, the side length of the refractory material in the furnace is 2 meters, and the lowest bulk specific gravity of the waste steel is designed according to 2.0 tons/cubic meter. 2m square openings are formed in the furnace cover of the electric arc furnace and used for feeding scrap steel; the waste steel in the shaft furnace is divided into three layers, two layers of manipulators 10-1 and 10-2 are arranged, and each layer of waste steel is predicted to be 35-40 tons. Adding scrap steel twice in each furnace smelting;
the bottom of the shaft furnace is provided with a rotary flap valve 8, the rotary flap valve 8 is provided with a locking bolt, a first layer of mechanical arm 10-1 is arranged at a position 6 meters away from the bottom of the shaft furnace and provided with the rotary flap valve 8, a second layer of mechanical arm 10-2 is 5.5 meters away from the first layer of mechanical arm 10-1, and the top of the scrap steel preheating shaft furnace 2 and the second layer of mechanical arm 10-2 are 6 meters;
The bottom of the shaft furnace is connected with a scrap steel charging hole of the electric arc furnace through an inclined slideway, a certain gap is reserved between a sealing seat arranged at the scrap steel charging hole of the electric arc furnace and the scrap steel inclined slideway, the electric arc furnace is sealed through a hydraulic sealing system 6, and when the electric arc furnace tilts tapping and deslagging, the hydraulic sealing plate 6 is automatically opened; a refractory sealing and blocking valve 7 is arranged on the inclined slide way to block the radiant heat of the electric arc furnace, prevent high-temperature smoke from leaking and protect furnace bottom equipment of the shaft furnace;
Taking a three-section preheating channel as an example, a lower annular flue 9-1 and an upper annular flue 9-2 are respectively arranged on the upper part of the scrap steel preheating shaft furnace 2, which is 500mm and 6300mm away from the furnace bottom, and the upper annular flue and the lower annular flue are connected with the inside of the shaft furnace by bronchi which are arranged around; the lower annular flue and the upper annular flue are connected with the arc furnace exhaust port through a connecting flue.
The lower annular flue 9-1 and the upper annular flue 9-2 are connected with an arc furnace exhaust port through a connecting flue 3, a secondary combustion chamber 13 is arranged before the connecting flue 3 enters the upper annular flue 9-2, a refractory valve 12 is arranged on the connecting flue 3 before the secondary combustion chamber 13, a secondary combustion section in the furnace is arranged between the first layer of scrap steel material top and the first layer of manipulator, 3 auxiliary gas nozzles are arranged on each surface of the furnace wall, and combustion-supporting gas is supplemented and blown in the secondary combustion section to burn off unburned gas. The command system of the high temperature resistant material valve 12 is limited by system resistance, the high temperature resistant material valve 12 is connected with the command system, the command system can detect equipment pressure, when the detected negative pressure value reaches a set value, the command system automatically opens the material valve 12, the combustion-supporting gas system of the secondary combustion chamber 13 is shared with the combustion-supporting gas system of the secondary combustion section in the furnace, when the high temperature resistant material valve 12 is opened, the combustion-supporting gas system is automatically switched to the secondary combustion chamber 13 to support combustion, and simultaneously, the amount of injected combustion-supporting gas is automatically adjusted according to the carbon monoxide concentration value of the flue gas detection system, so that the carbon monoxide concentration is reduced to the local environmental emission standard.
The gas outlet of the arc furnace is provided with a connecting sealing seat, a certain gap is reserved between the connecting flue 3 and the connecting sealing seat of the gas outlet of the arc furnace, the arc furnace is sealed by a hydraulic sealing ring 11, and the hydraulic sealing ring 11 can be automatically opened when the arc furnace tilts to discharge steel and slag;
The bottom of the shaft furnace is provided with two opposite rotary plate valves 8, the rotary shafts are arranged on two sides, the middle parts of the rotary plates are respectively provided with locking bolts of the two rotary plate valves when the rotary plates are in a sealed steel scrap bearing state, when steel scraps are unloaded, the bolts are pulled out firstly, the rotary plate valve rotary system is started to unload the steel scraps, and after the steel scraps are unloaded, the rotary plate valves are rotated back to the sealed state, and the bolts are inserted.
An isostatic pressing sealing charging system is arranged at the top of the shaft furnace. The isostatic pressure sealing charging system is provided with an upper sealing plate and a lower sealing plate, the upper sealing plate and the lower sealing plate are in a sealing state during the non-working period of the charging system, the upper sealing plate is opened when the scrap steel is added into the scrap steel groove, the upper sealing plate is closed after the scrap steel is added, the lower sealing plate is opened when the scrap steel is added into the shaft furnace, and the lower sealing plate is closed after the scrap steel is discharged. Therefore, a large amount of wild wind can be prevented from entering the system due to pressure relief of the system, and normal smoke flow of the system is prevented from being influenced.
A blow-off valve 19 is arranged on a pipeline between the dust remover 16 and the induced draft fan 17, and when the frequency modulation fan runs to a low position, the regulation state of the blow-off valve is started. The regulation control system signal is derived from the electric arc furnace pressure sensor.
The main fuel is selected from 6500 kcal/kg anthracite, 40 kg/ton steel of coal injection per ton steel, 10 cubic meters/ton steel of natural gas consumption, 100 kWh/ton steel of electricity consumption and 95 cubic meters/ton steel of oxygen consumption. Before transformation, the electricity consumption per ton of steel is 550 degrees per ton of steel, the oxygen consumption per ton of steel is 40 cubic meters, the coal dust consumption per ton of steel is 15 kg, and the electricity consumption per ton of steel is 550 kilowatt-hours.
Metal yield: 89% before transformation, 97% after transformation and 8% improvement.
Nitrogen oxide removal rate: 350mg/Nm 3 before modification and 30mg/Nm 3 after modification.
Coal cost is calculated according to 800 yuan/ton of steel, electricity price is calculated according to 0.6 yuan/kilowatt hour, oxygen is calculated according to 0.5 yuan/cubic meter, natural gas is calculated according to 2.8 yuan/cubic meter, steel loss is calculated according to 2500 yuan/ton of steel, ton of steel saves fuel cost by 190 yuan/ton of steel, and steel and iron are saved by 200 yuan/ton of steel. The effect of reducing the cost is obvious.
The smelting period is shortened by 10 minutes after transformation, and the continuous casting rhythm can be completely satisfied. The fume emission completely meets the environmental protection requirement. The carbon dioxide emission of ton steel is reduced by about 300 kg/ton steel, and the emission is reduced by about 60%.
Claims (10)
1. The utility model provides a once burn auxiliary heating electric arc furnace steelmaking equipment, its characterized in that, including electric arc furnace and the waste steel preheating shaft furnace that is connected, electric arc furnace top be equipped with the exhaust pipe, exhaust pipe and waste steel preheating shaft furnace be connected, waste steel preheating shaft furnace stove bottom be equipped with rotatory flap valve, waste steel preheating shaft furnace includes upper portion vertical channel and the oblique unloading passageway of bottom, waste steel preheating shaft furnace sets up in electric arc furnace's oblique top, both are connected through oblique unloading passageway, be equipped with resistant material sealing and blocking valve in the middle of the oblique unloading passageway, wherein:
The vertical section channel of the scrap steel preheating shaft furnace is an N-section preheating channel, and specifically comprises a first scrap steel preheating section, a second scrap steel preheating section, … and an N-layer scrap steel preheating section from bottom to top, wherein N=2-4;
The vertical section channel of the scrap steel preheating shaft furnace is sequentially provided with a first layer of mechanical arm, a second layer of mechanical arm, … th layer of mechanical arm and an N-1 th layer of mechanical arm from bottom to top, a layer of scrap steel preheating section is formed between the rotary flap valve and the first layer of mechanical arm, a two-layer scrap steel preheating section is formed between the second layer of mechanical arm and the first layer of mechanical arm, … is formed, and N layers of scrap steel preheating sections are formed above the N-1 th layer of mechanical arm;
the bottom of the side wall of the N-layer scrap preheating section and the bottom of the side wall of the N-1 layer scrap preheating section are respectively provided with an annular flue, one end of the annular flue is connected with the scrap preheating shaft furnace through a bronchus, and the other end of the annular flue is connected with a smoke exhaust pipe.
2. The primary combustion assisted heating electric arc furnace steelmaking apparatus of claim 1 wherein:
A plurality of strong reducing gas nozzles are uniformly arranged above the furnace wall of the electric arc furnace at intervals, and a plurality of oxygen burning guns are uniformly arranged below the furnace wall at intervals; the rotary flap valve is matched with a locking bolt.
3. The primary combustion assisted heating electric arc furnace steelmaking apparatus of claim 1 wherein:
a high-temperature resistant material valve is arranged on the smoke exhaust pipe connected with the annular flue at the bottom of the side wall of the layer 2 scrap steel preheating section, and a secondary combustion chamber is arranged between the high-temperature resistant material valve and the layer of annular flue;
The secondary combustion section is arranged between the first layer of mechanical arm and the first layer of scrap steel material top, and the secondary combustion section is matched with a combustion-supporting gas injection system.
4. The primary combustion assisted heating electric arc furnace steelmaking apparatus of claim 1 wherein a combustion gas nozzle and a small oxygen lance are disposed between the first layer scrap top and the second layer scrap bottom, the oxygen lance being located remotely from the robot.
5. The primary combustion auxiliary heating electric arc furnace steelmaking equipment according to claim 1, wherein a refractory sealing and blocking valve is arranged on the inclined blanking channel, a charging isostatic pressure chamber is arranged on the top of the scrap steel preheating shaft furnace, a shaft furnace smoke exhaust pipeline is connected to the side wall of the top of the furnace, a pipeline reactor, a dust remover, an induced draft fan and a chimney are sequentially arranged on the shaft furnace smoke exhaust pipeline, a gas release valve is arranged at an inlet of the induced draft fan, and the chimney is designed to be reasonable in height according to local environmental requirements.
6. The primary combustion assisted heating electric arc furnace steelmaking apparatus of claim 1 wherein:
A gap is arranged between the scrap steel inclined blanking channel and the electric arc furnace body and is sealed by a sealing system; a gap is arranged between the smoke exhaust pipe and the electric arc furnace body and is sealed by a hydraulic sealing ring;
A moving gap is reserved between the inclined discharging channel of the scrap steel preheating shaft furnace and the charging hole of the electric arc furnace, and a sealing system is used for sealing and connecting a refractory sealing and blocking valve.
7. A primary combustion assisted heating electric arc furnace steelmaking process employing an apparatus according to any one of claims 1 to 6 comprising the steps of:
(1) In the operation process of the electric arc furnace, high-temperature flue gas is obtained, the flue gas is communicated with a layer of waste steel preheating section-N-1 layer of waste steel preheating section through a flue gas exhaust pipe, waste steel is added to different preheating sections in the waste steel preheating shaft furnace in batches, the lower layer flue gas is continuously upwards used for heating the layer-by-layer waste steel, and finally the flue gas is cooled to 80-150 ℃ after heat exchange with the waste steel and is discharged from a flue gas outlet of the shaft furnace;
(2) After the whole equipment runs stably, strong reducing fuel gas is injected into the electric arc furnace at the upper part of the electric arc furnace, nitrogen oxides generated by electric arc and lower oxygen burning guns are reduced and removed, and the nitrogen oxides are burnt with the excessive oxygen of the lower oxygen burning guns, so that the oxygen oxidability is reduced, and the burning loss of scrap steel is reduced;
(3) When the heating temperature of the first layer of scrap steel reaches a reflow point, the compression density of the bottom scrap steel is increased, and when the system resistance reaches a design limit value, a high-temperature resistant material valve in front of a secondary combustion chamber is started, and most of smoke gas directly enters an upper annular flue to directly heat the second layer of scrap steel and the upper layer of scrap steel;
(4) Before the electric arc furnace tapping, stopping the oxygen burning gun and the strong reduction gas injection, stopping or starting the induced draft fan to the lowest grade, avoiding the waste steel preheating shaft furnace system from entering air to cause oxidation of the waste steel, opening a waste steel discharging channel and a sealing system between a flue gas channel and the electric arc furnace body, and tilting the furnace body to tap;
(5) After the steel is discharged, a sealing system between a steel scrap discharging channel and a flue gas channel and an electric arc furnace body is closed, a refractory sealing plate of the steel scrap discharging channel is opened, a rotary flap valve of the bottom of a steel scrap preheating shaft furnace is pulled out for cutting, the rotary flap valve is started, steel scrap falls into the electric arc furnace 1, steel scrap is reserved, and impact of the steel scrap to the bottom of the furnace is reduced;
(6) After the scrap steel is added, closing a rotary flap valve, recovering a refractory sealing and blocking valve to a protection state, withdrawing a first layer of mechanical arm, placing a second layer of scrap steel to the furnace bottom, recovering the first layer of mechanical arm to a supporting state, withdrawing the second layer of mechanical arm, placing a third layer of scrap steel to the first layer of mechanical arm, recovering the second layer of mechanical arm to the supporting state, and sequentially recovering all layers of mechanical arms to the supporting state; and (5) completing the whole process.
8. The primary combustion assisted heating electric arc furnace steelmaking method according to claim 7 wherein in step (1) nitrogen oxides in the electric arc furnace flue gas are reduced to nitrogen and removed.
9. The steelmaking method of a primary combustion auxiliary heating electric arc furnace according to claim 7, wherein in the step (2), residual unburned reducing gas enters the shaft furnace, waste steel oxidation in a high temperature area of the shaft furnace is avoided due to existence of excessive reducing gas, and air is blown in for secondary combustion in a temperature interval of 550-800 ℃ of the shaft furnace to ensure that the unburned reducing gas is burned. And the scrap steel is not easy to oxidize.
10. The steelmaking method of a primary combustion auxiliary heating electric arc furnace according to claim 7, wherein in the step (3), a combustion air system of the secondary combustion chamber is started at the same time when the high temperature resistant refractory valve is started, the combustion air system is shared with a combustion air system of a secondary combustion section in the shaft furnace, a switching valve is arranged, and the combustion air quantity is controlled by the carbon monoxide concentration detected by a smoke detection system of a smoke outlet of the shaft furnace.
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