Full-grade direct reduction iron pretreatment device

Abstract

The invention belongs to the technical field of steel smelting, and relates to a full-grade direct reduction iron pretreatment device. The device comprises a direct reduction iron preheating vertical shaft, a direct reduction iron feeding device and an electromagnetic induction heating coil. The direct reduction iron preheating vertical shaft is arranged at the top of the converter / electric furnace and extends in the vertical direction, and a DRI outlet is communicated with an inlet of the smelting furnace; the direct reduction iron feeding device is mounted at the top end of the direct reduction iron preheating vertical shaft, and internal DRI can be graded and distributed into the direct reduction iron preheating vertical shaft in rows when the direct reduction iron feeding device is started; and the electromagnetic induction heating coil covers the outer side of the direct reduction iron preheating vertical shaft. According to the device, efficient preheating of the DRI can be achieved on the basis of original preheating equipment. An electromagnetic induction coil is arranged outside a direct reduction iron preheating vertical shaft, a net-shaped induction heating rod is installed inside the direct reduction iron preheating vertical shaft, the dependence of a single heating mode on the DRI metallization ratio is broken through, high-grade DRI is rapidly heated through the direct induction eddy current effect, and medium-grade and low-grade DRI is heated through induction resistance heat of the induction heating rod; and the electromagnetic induction coil is simple and convenient to install, not easy to damage and low in maintenance cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel smelting, and relates to a pretreatment device for direct reduced iron with all grades of iron ore. Background Art

[0002] In the steel smelting process, the main raw materials for converters and electric furnaces have traditionally relied on hot metal and scrap steel. However, as metallurgical technology evolves towards green and low-carbon directions, direct reduced iron (DRI) has gradually become an important alternative or supplementary raw material for scrap steel due to its unique advantages. Specifically, DRI is produced from iron ore by the direct reduction method (such as gas-based or coal-based reduction processes), and its metallization rate (i.e., the content of metallic iron) can reach 50% - 95%. Compared with scrap steel, DRI has the characteristics of pure composition (without residual elements such as copper, tin, and lead), stable supply (not limited by the social recovery volume of scrap steel), uniform size (3 - 30 mm), and fast melting rate, and is particularly suitable for the production of high-quality steel and the smelting requirements in resource-scarce areas.

[0003] However, DRI needs to be pretreated before being charged into the furnace to optimize its applicability. Since DRI needs to be cooled by spraying water after production to inhibit oxidation reactions, and is often exposed to humid environments (such as sea transportation) during transportation, its temperature is usually lower than room temperature or even in a low-temperature state. The smelting of converters or electric furnaces has strict requirements for the temperature of raw materials: converter smelting relies on the heat value of hot metal itself and the heat release from carbon oxidation, and low-temperature DRI is likely to cause the temperature drop and solidification risk of molten steel; electric furnace smelting requires raw materials to have a relatively high charging temperature to shorten the melting cycle and reduce power consumption. Therefore, improving the drying efficiency and preheating temperature of DRI has become the core goal of pretreatment. The existing pretreatment of drying and preheating DRI before steelmaking has the following problems:

[0004] First, flue gas preheating technology: In the horizontal continuous feeding preheating device, due to the thermal buoyancy effect, the high-temperature flue gas quickly floats upward, resulting in a short contact time with DRI and low heat exchange efficiency, leading to insufficient preheating temperature (usually lower than 200°C), making it difficult to meet the smelting requirements; in the shaft-type preheating device, the flue gas will flow closely along the shaft wall after entering the shaft, and only DRI in local areas is heated, with poor preheating uniformity, and the high-temperature area is prone to cause secondary oxidation of DRI and a decrease in metallization rate.

[0005] Second, electromagnetic induction heating technology: High-grade DRI (metallization rate > 80%) can be effectively heated by the induction coil because its conductivity is similar to that of scrap steel. However, for medium and low-grade DRI (metallization rate 50% - 80%), due to the high content of iron oxides and gangue, the conductivity and magnetic permeability are significantly reduced, and a closed eddy current cannot be formed, resulting in the failure of induction heating. Therefore, electromagnetic induction heating has strict requirements for the metallization rate of DRI and is difficult to be compatible with high-grade and medium and low-grade raw materials.

[0006] Third, the gangue (such as impurities like SiO2, Al2O3, etc.) content in medium- and low-grade DRI is relatively high (usually more than twice that of high-grade DRI), resulting in a significant increase in slag volume during the smelting process and requiring higher energy input, with a substantial increase in power consumption. Therefore, pretreatment methods are usually required before the smelting process to increase the metallization rate of medium- and low-grade DRI.

[0007] Fourth, when adding DRI, all sizes of DRI are usually added together into the preheating furnace, and different sizes of DRI cannot be classified. For electromagnetic induction heating, the smaller the equivalent diameter of the material on the outer circle of the furnace, the better the induction heating effect. Therefore, a new device is needed to classify different sizes of DRI and add them to the preheating shaft.

[0008] The Chinese patent application with the publication number CN118475707A discloses a device for inductive heating of direct reduced iron, which provides heat for temperature rise through an inductive heating device and passes a reducing gas such as natural gas, hydrogen, or carbon monoxide into the reactor to manufacture hot briquetted iron (HBI) from direct reduced iron (DRI) at high temperature. Moreover, it does not mention how to carry out temperature rise and reduction in the case where medium- and low-grade DRI cannot be inductively heated.

[0009] The Chinese patent application with the publication number CN118064671A discloses a steelmaking device with the function of scrap preheating, which classifies and separately adds scrap through multiple feeding bins, creating differences in the size and porosity of scrap in the axial direction within the shaft to promote subsequent preheating. However, this method is not applicable to the charging method of inductive heating because inductive heating requires arranging materials with low porosity on the outer periphery of the furnace rather than in a certain column.

[0010] Based on this, there is an urgent need for a pretreatment device for all-grade direct reduced iron to solve the above problems. Summary of the Invention

[0011] The purpose of the present invention is to provide a pretreatment device for all-grade direct reduced iron to solve the problems existing in the above-mentioned prior art and improve the steel smelting efficiency.

[0012] To achieve the above purpose, the present invention adopts the following technical solutions:

[0013] A pretreatment device for all-grade direct reduced iron includes a direct reduced iron preheating shaft, a direct reduced iron feeding device, and an electromagnetic induction heating coil. The direct reduced iron preheating shaft is arranged on top of the converter / electric furnace and extends vertically, with the DRI outlet communicating with the inlet of the smelting furnace; the direct reduced iron feeding device is installed at the top of the direct reduced iron preheating shaft, and when starting, it can classify the internal DRI and distribute it in columns into the direct reduced iron preheating shaft; the electromagnetic induction heating coil is coated on the outside of the direct reduced iron preheating shaft.

[0014] Further features: The direct reduced iron feeding device is successively provided with a conveying device, a sorting device and a distributing device; the conveying device is used for horizontally conveying DRI to the sorting device; the sorting device is used for classifying DRI according to the size of DRI, sorting small-sized DRI to the outside of the distributing device, and sorting large-sized DRI to the inside of the distributing device; the distributing device feeds DRI of different sizes into the direct reduced iron preheating shaft according to the baffle in the middle. DRI moves along the baffle track of the distributing device towards the direct reduced iron preheating shaft and falls into the direct reduced iron preheating shaft. Until it is detected that the DRI fills the entire direct reduced iron preheating shaft, the direct reduced iron feeding device stops horizontal conveying and cuts off the feeding.

[0015] Further features: The inside of the direct reduced iron preheating shaft contains multiple high-permeability iron-based alloys, called induction heating rods. The induction heating rods are connected to the furnace body on the side of the direct reduced iron preheating shaft, and the middle section and the bottom end are interconnected by a mesh structure to enhance the heat conduction and electrical conductivity between the iron rods, and are used for applying conduction heating to medium and low-grade DRI with a metallization rate of 50% - 80%.

[0016] Further features: The crucible of the direct reduced iron preheating shaft is made of refractory material, heat insulation cotton and non-magnetic steel from the inside to the outside. The refractory material is made of magnesium oxide, refractory cement, glass water, etc., and fixes the internal induction heating rods. The heat insulation cotton isolates the internal heat from the outside, preventing the high temperature from being transmitted to the external non-magnetic steel, avoiding the softening of the non-magnetic steel due to excessive temperature, and improving the service life of the non-magnetic steel. The relative magnetic permeability of the non-magnetic steel is extremely low (slightly higher than 1) and cannot be inductively heated in the electromagnetic induction coil.

[0017] Further features: A temperature measuring thermocouple and a gas nozzle are provided at the bottom of the direct reduced iron preheating shaft. The gas nozzle is connected to a mixed gas source of hydrogen and carbon monoxide, and can inject reducing gas into the direct reduced iron preheating shaft, and contact with the high-temperature DRI to occur a secondary reduction reaction of iron oxide slag, improving the metallization rate of DRI and the quality of the molten steel in subsequent smelting.

[0018] Further features: The discharge valve at the bottom of the direct reduced iron preheating shaft is composed of two reversely rotatable honeycomb plates. There are multiple round holes in the two honeycomb plates, and the shapes, sizes and positions are the same. The feeding speed and feeding time of DRI can be controlled by the rotation angles of the two honeycomb plates.

[0019] Further features: The electromagnetic induction heating coil is connected to a power controller, and the power controller can be used to supply power to the electromagnetic induction coil and control its heating power.

[0020] Further features: The electromagnetic induction coil, the discharging valve, and the temperature measuring thermocouple all adopt an automatic control mode, and parameters such as the power of the electromagnetic induction coil and the feeding speed of the discharging valve can be dynamically adjusted according to the real-time state in the smelting furnace.

[0021] The equipment and method of the present invention have the following remarkable beneficial effects:

[0022] The device of the present invention can achieve efficient preheating of DRI on the basis of the original preheating equipment. By arranging an electromagnetic induction coil outside the direct reduced iron preheating shaft and installing a mesh induction heating rod inside, the dependence on a single heating method for the metallization rate of DRI is broken through. High-grade DRI rapidly heats up through the eddy current effect of direct induction, and medium and low-grade DRI heats up through the induction resistance heat of the induction heating rod. Moreover, the electromagnetic induction coil is easy to install, not easily damaged, and has low maintenance costs, and can be directly retrofitted on the existing shaft furnace, significantly improving the economic benefits. By designing a new direct reduced iron feeding device, DRI can be classified during the feeding process and fed into the preheating shaft, so that the DRI in the direct reduced iron preheating shaft is arranged in a separated manner, with smaller DRI on the outside and larger DRI on the inside, further improving the induction heating effect. By installing a gas spout at the bottom of the direct reduced iron preheating shaft, secondary reduction treatment of DRI is realized, the metallization rate of DRI is increased, the desulfurization burden during the smelting process is significantly reduced, and the quality of the molten steel in the subsequent smelting is improved. Finally, by designing the structure of the direct reduced iron discharging valve, the feeding speed and feeding time of DRI can be flexibly controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the full-grade direct reduced iron pretreatment device in the embodiment of the present invention;

[0024] Figure 2 It is a structural diagram of the induction heating rod, where (a) is the main view of the structure of the induction heating rod; (b) is the top view of the structure of the induction heating rod;

[0025] Figure 3 It is a schematic structural diagram of the discharging valve;

[0026] Figure 4 It is a schematic structural diagram of the sorting device;

[0027] Figure 5 It is a schematic structural diagram of the crucible.

[0028] In the figure: 1 direct reduced iron preheating shaft; 2 direct reduced iron feeding device; 3 electromagnetic induction heating coil;

[0029] 11 Furnace body; 12 Crucible; 13 Induction heating rod; 14 Gas nozzle; 15 Temperature measuring thermocouple; 16 Discharge valve; 21 Total conveying device; 22 Sorting device; 23 Small-size conveying device; 24 Large-size feeding port; 25 Small-size feeding port; 121 Refractory material; 122 Heat insulation cotton; 123 Non-magnetic steel. Detailed implementation mode

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments of the present invention.

[0031] An all-grade direct reduced iron pretreatment device is provided in an embodiment of the present invention. As shown in the figure, the all-grade direct reduced iron pretreatment device may include: a direct reduced iron preheating shaft 1, a direct reduced iron feeding device 2, and an electromagnetic induction heating coil 3.

[0032] Among them, the direct reduced iron preheating shaft is arranged on the top of the converter / electric furnace and extends in the vertical direction. The DRI outlet is communicated with the inlet of the smelting furnace; the direct reduced iron feeding device is installed at the top of the direct reduced iron preheating shaft. When starting, it can classify and distribute the DRI inside to the direct reduced iron preheating shaft; the electromagnetic induction heating coil is coated on the outside of the direct reduced iron preheating shaft.

[0033] An all-grade direct reduced iron pretreatment device provided in an embodiment of the present invention includes a direct reduced iron feeding device 2. The direct reduced iron feeding device 2 is fixedly connected to the top of the direct reduced iron preheating shaft 1 through a flange, and is internally provided with a total conveying device 21, a small-size conveying device 23, a sorting device 22, and feeding ports 24 and 25 in sequence. The total conveying device 21 is used to horizontally convey the DRI to the sorting device 22. The sorting device 22 is used to classify the DRI according to the size of the DRI, sort the small-size DRI to the small-size conveying device 23 and feed it to the outside of the feeding device, that is, the small-size feeding port 25, and sort the large-size DRI to the inside of the feeding device, that is, the large-size feeding port 24. The feeding device composed of two feeding ports feeds DRI of different sizes into the direct reduced iron preheating shaft 1 according to the baffle in the middle. The DRI moves along the baffle track of the feeding device towards the direct reduced iron preheating shaft 1 and falls into the direct reduced iron preheating shaft 1. Until it is detected that the DRI fills the entire direct reduced iron preheating shaft, the direct reduced iron feeding device 2 stops the total conveying device 21 and cuts off the feeding.

[0034] Specifically, the grading device 22 is a steel plate with multiple round holes of 20 mm in diameter inside. When DRI of different sizes enters the grading device 22 from the conveying device 21, the DRI rolls down along the steel plate. During the downward rolling process, small-sized DRI (diameter < 20 mm) will fall through the round holes onto the conveying device 23, and large-sized DRI (diameter > 20 mm) will continue to fall directly along the steel plate to the feeding port 24. The small-sized DRI falls through the conveying device 23 to the feeding port 25.

[0035] A full-grade direct reduced iron pretreatment device provided by an embodiment of the present invention includes a direct reduced iron preheating shaft 1, and the DRI inlet of the direct reduced iron preheating shaft 1 is connected to the DRI outlet of a direct reduced iron feeding device 2 through a flange interface. When DRI is output from the outlet of the direct reduced iron feeding device 2, it enters the direct reduced iron preheating shaft 1 separately through the material inlet of the direct reduced iron preheating shaft 1, and the preheating program is started.

[0036] Among them, the direct reduced iron preheating shaft 1 may include a furnace body 11 having a receiving cavity for DRI, a crucible 12 capable of heat insulation for the furnace body 11, an induction preheating rod 13 connected to the crucible 12, a gas nozzle 14 at the bottom for blowing reducing gas, a temperature measuring thermocouple 15 for measuring the temperature of DRI during preheating, and a discharge valve 16 for controlling the feeding speed and time of DRI. The DRI enters the receiving cavity of the furnace body 11 to start preheating.

[0037] Specifically, the crucible 12 of the direct reduced iron preheating shaft 1 is composed of a refractory material 121, a heat insulation cotton 122, and a non-magnetic steel 123 from the inside to the outside. The refractory material 121 is made of magnesium oxide, refractory cement, glass water, etc., and fixes the internal induction heating rod 13; the heat insulation cotton 122 isolates the heat of the internal furnace body 11 from the external non-magnetic steel 123, preventing high temperature from being transmitted to the external non-magnetic steel 123 and avoiding softening of the non-magnetic steel 123 due to excessive temperature, thereby improving the service life of the non-magnetic steel 123.

[0038] A full-grade direct reduced iron pretreatment device provided by an embodiment of the present invention includes an electromagnetic induction heating coil 3, and the electromagnetic induction coil 3 is connected to a power controller. The power controller supplies power to the electromagnetic induction coil 3 and accurately regulates the heating power. By heating the DRI passing through the direct reduced iron preheating shaft 1 through the electromagnetic induction coil 3, the DRI can be fully and evenly preheated, and there will be no heating dead corners, and the problem that some DRI cannot be fully preheated can be avoided. At the same time, by heating the raw materials in the direct reduced iron preheating shaft 1 through the electromagnetic induction coil 3, contactless heating of scrap steel can be realized, completely eliminating open flames and waste gas emissions, meeting the requirements of clean production. Compared with the traditional resistance coil and flue gas preheating processes, in this solution, the electromagnetic induction coil 3 generates an electromagnetic eddy current effect directly acting on the DRI, with high energy conversion efficiency, simple operation, no obvious mechanical wear parts, and low installation and maintenance costs.

[0039] In some examples, the heating rate and temperature of the raw materials passing through the direct reduced iron preheating shaft 1 by the electromagnetic induction coil 3 can be dynamically regulated by the power controller to form a closed-loop control system linked with the smelting process. When the smelting furnace needs to increase the DRI feeding amount at a specific stage, the power controller can dynamically increase the heating power of the electromagnetic induction coil 3 to make the preheating rate of the DRI in the shaft match the feeding demand, ensuring that the temperature of the raw materials entering the furnace is stably within the range of ±15°C, effectively suppressing the risk of molten steel solidification caused by temperature drop and the large fluctuation of the smelting cycle.

[0040] Specifically, the preheating temperature of the DRI can be monitored in real time by a temperature measuring thermocouple 15 at the bottom of the direct reduced iron preheating shaft 1, and the temperature measuring thermocouple 15 can be signal-interconnected with the power controller of the electromagnetic induction coil 3. When the temperature of the DRI at the outlet of the direct reduced iron preheating shaft 1 is monitored to be lower than the preset threshold, the power controller automatically activates the power compensation mechanism and stepwise increases the output power of the electromagnetic induction coil 3 to the target value, so that the temperature of the subsequent output DRI quickly returns to the set range, realizing the adaptive adjustment of the preheating process.

[0041] In some embodiments, the production method of DRI may result in a metallization rate of only 50% - 70%, and the high proportion of slag leads to insufficient conductivity of medium and low-grade DRI, which cannot be induced. A number of high-permeability iron-based alloys are welded and fixed on the crucible 12 of the direct reduced iron preheating shaft 1 as induction heating rods 13. The induction heating rods 13 are heated by induction and transfer heat to the medium and low-grade DRI in the furnace body 11 that cannot be induced through thermal radiation and heat conduction, increasing the preheating temperature of the DRI.

[0042] Specifically, the induction heating rods 13 are interconnected by a mesh structure in the middle and bottom sections. The reason is that individual iron-based alloys are not interconnected with each other, which will result in a relatively low magnetic induction intensity during induction heating, less self-heating, and less heat provided for DRI. After using the mesh structure for interconnection, the formed closed eddy current loop becomes larger, the magnetic induction intensity increases accordingly, and the heating amount increases, which is beneficial to providing more heat for DRI. Moreover, the mesh structure adopts a hollow design, which strengthens electromagnetic induction while ensuring that DRI can fall freely smoothly, and the mesh structure is strong and reliable with low maintenance costs.

[0043] In some embodiments, the induction heating rods 13 can also use graphite to replace the iron-based alloy. Because the physical property parameters such as the conductivity, relative magnetic permeability, and thermal conductivity of graphite are much higher than those of the iron-based alloy, it is more easily inductively heated in the electromagnetic induction coil 3, and its thermal conductivity is also good, which can quickly transfer heat to various positions of the entire furnace body 11, making the DRI heat up faster and more evenly. At the same time, graphite can undergo a gas-solid reduction reaction with the internal ferric oxide slag in DRI at high temperatures to generate metallic iron, improving the metallization rate of DRI in the furnace body 11.

[0044] In some embodiments, the winding structure of the electromagnetic induction coil 3 can be self-selected and designed for adaptability. The electromagnetic induction coil 3 should be wound conformally on the non-magnetic steel 123 on the outer wall of the direct reduced iron preheating shaft 1. That is, if the direct reduced iron preheating shaft 1 is a cylinder, the electromagnetic induction coil 3 is wound in an annular spiral shape; if the direct reduced iron preheating shaft 1 is a cuboid, the electromagnetic induction coil 3 is wound in a rectangular spiral shape. The conformal gap between the electromagnetic induction coil 3 and the non-magnetic steel 123 on the outer wall of the direct reduced iron preheating shaft 1 is less than 20 mm, so that the electromagnetic coupling efficiency is increased to more than 90%, and the energy utilization rate reaches more than 85%.

[0045] In some embodiments, for medium and low-grade DRI with a metallization rate of 50% - 80%, the gas nozzles 14 provided at the bottom of the furnace body 11 can inject a mixed gas of hydrogen and carbon monoxide into the furnace body 11. The gas countercurrently penetrates the DRI material layer in the furnace body 11 and undergoes a gas-solid reduction reaction with the internal ferric oxide slag in DRI in the temperature range of 600 - 750 °C to generate metallic iron, improving the metallization rate of DRI in the furnace body 11, completing the secondary thermal reduction of medium and low-grade DRI, and improving the quality of the molten steel in subsequent smelting. The reaction tail gas flows to the sealing cavity of the direct reduced iron feeding device 2 through the diversion channel at the top of the direct reduced iron preheating shaft 1, and the reduction gas is efficiently recovered and utilized through the cyclone dust removal and gas circulation system.

[0046] In some embodiments, when the preheating temperature of the DRI reaches a specified threshold, the discharge valve 16 at the bottom of the DRI preheating shaft 1 is opened, and the DRI that has completed preheating and secondary thermal reduction at the bottom of the DRI preheating shaft 1 is added to the smelting furnace. During this discharging stage, the spiral guide trough of the top DRI feeding device 2 continuously supplements cold DRI to the furnace body 11 of the DRI preheating shaft 1 at a rotation speed that dynamically matches the discharging rate, forming a continuous preheating operation mode.

[0047] Specifically, as Figure 3 shown, the structure of the discharge valve 16 is a two-layer honeycomb structure that can rotate in opposite directions to each other. The shapes, sizes, and positions of the round holes in the two honeycomb plates are exactly the same. During the rotation of the two honeycomb plates relative to each other, the round holes start to coincide, and the DRI preheating shaft 1 starts to feed materials into the smelting furnace; continuing to rotate, the DRI feeding speed continuously increases; when the round holes completely coincide, the DRI feeding speed is the maximum; when the round holes are completely staggered, the DRI feeding ends. By controlling the rotation angle of the two honeycomb plates from 0° to 180°, the feeding speed and feeding time of the DRI are controlled.

Claims

1. An apparatus for pre-treating full-grade direct reduced iron, characterized in that, It includes a direct reduced iron preheating shaft, a direct reduced iron feeding device, and an electromagnetic induction heating coil; the direct reduced iron preheating shaft is arranged on top of the converter / electric furnace and extends vertically, and the DRI outlet is communicated with the smelting furnace inlet; the direct reduced iron feeding device is installed at the top of the direct reduced iron preheating shaft, and when starting, it can classify the internal DRI and distribute it in rows into the direct reduced iron preheating shaft; the electromagnetic induction heating coil is coated on the outside of the direct reduced iron preheating shaft.

2. The device for pre-treating all-grade direct reduced iron according to claim 1, characterized in that, The direct reduced iron feeding device is successively provided with a conveying device, a sorting device, and a feeding device; the conveying device is used to horizontally convey the DRI to the sorting device; the sorting device is used to classify the DRI according to the size of the DRI, sort the small-sized DRI to the outside of the feeding device, and sort the large-sized DRI to the inside of the feeding device; the feeding device feeds the DRI of different sizes into the direct reduced iron preheating shaft according to the middle baffle, and the DRI moves along the baffle track of the feeding device towards the direct reduced iron preheating shaft and falls into the direct reduced iron preheating shaft. Until it is detected that the DRI fills the entire direct reduced iron preheating shaft, the direct reduced iron feeding device stops horizontal conveying and cuts off the feeding.

3. An apparatus for pre-treating full-grade direct reduced iron according to claim 1 or 2, characterized in that, The inside of the direct reduced iron preheating shaft contains multiple high-permeability iron-based alloys, called induction heating rods; the induction heating rods are connected to the furnace body on the side of the direct reduced iron preheating shaft, and the middle section and the bottom end are connected to each other by a mesh structure to enhance the heat conduction and electrical conductivity between the iron rods, and are used for applying heat conduction heating to medium and low-grade DRI with a metallization rate of 50% - 80%.

4. The device for pre-treating all-grade direct reduced iron according to claim 3, characterized in that, The crucible of the direct reduced iron preheating shaft is made of refractory material, heat insulation cotton, and non-magnetic steel from the inside to the outside. The refractory material is made of magnesia, refractory cement, glass water, etc., and fixes the internal induction heating rods. The heat insulation cotton isolates the internal heat from the outside, preventing the high temperature from being transmitted to the external non-magnetic steel, avoiding the softening of the non-magnetic steel due to excessive temperature, and improving the service life of the non-magnetic steel. The relative magnetic permeability of the non-magnetic steel is extremely low and cannot be inductively heated in the electromagnetic induction coil.

5. The device for pre-treating all-grade direct reduced iron according to claim 4, characterized in that, The bottom of the direct reduced iron preheating shaft is provided with a temperature measuring thermocouple and a gas nozzle. The gas nozzle is connected to a mixed gas source of hydrogen and carbon monoxide, and can inject reducing gas into the direct reduced iron preheating shaft, and contact with the high-temperature DRI to occur a secondary reduction reaction of iron oxide slag, improving the metallization rate of the DRI and the quality of the molten steel in the subsequent smelting.

6. A device for pre-treating all-grade direct reduced iron according to claim 4 or 5, characterized in that, The discharge valve at the bottom of the direct reduced iron preheating shaft is composed of two reversely rotatable honeycomb plates. There are multiple round holes in the two honeycomb plates, and their shapes, sizes, and positions are the same. The feeding speed and feeding time of the DRI can be controlled by the rotation angles of the two honeycomb plates.

7. The device for pre-treating full-grade direct reduced iron according to claim 6, characterized in that, The electromagnetic induction heating coil is connected to a power controller, and the power controller can be used to supply power to the electromagnetic induction coil and control its heating power.

8. An apparatus for pre-treating all-grade direct reduced iron according to claim 7, characterized in that, The electromagnetic induction coil, the discharge valve, and the temperature measuring thermocouple all adopt an automatic control method, and can dynamically adjust parameters such as the power of the electromagnetic induction coil and the feeding speed of the discharge valve according to the real-time state in the smelting furnace.

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