Reduction melting separation furnace and reduction melting separation method for preparing DRI from low-grade ore

Abstract

The invention provides a reduction melting separation furnace and a reduction melting separation method for preparing DRI from low-grade ore, and belongs to the technical field of metallurgy. The reduction melt separation furnace comprises a melt separation furnace body, a material bearing pore plate, a gas injection device and an electrode, the melt separation furnace body is hollow and forms a furnace cavity, the material bearing pore plate is arranged in the furnace cavity and divides the furnace cavity into a reduction chamber and a molten pool which are arranged up and down, the material bearing pore plate is formed by splicing at least two pore plate bodies, and the at least two pore plate bodies can be opened and closed; when the at least two pore plate bodies are closed, the material bearing pore plate bears the DRI, when the at least two pore plates are opened, the DRI falls into the molten pool, the gas injection device is arranged in the furnace cavity and injects reducing gas to the DRI on the material bearing pore plate, and the electrode is inserted into the molten pool and used for being electrified to generate an electric arc so as to melt the DRI. According to the method, further efficient reduction of FeO in the low-grade DRI is achieved, the metallization ratio and the yield of the DRI are effectively increased, and low-grade ore resources are utilized to the maximum extent.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a reduction smelting furnace and a reduction smelting method for producing DRI from low-grade ore. Background Art

[0002] Hydrogen metallurgy is an important path for the steel industry to reduce greenhouse gas emissions. Its core is to produce direct reduced iron (DRI) by reducing iron ore with hydrogen-rich gas (such as H2+CO, pure hydrogen or coke oven gas). However, the existing hydrogen-based direct reduction process has extremely high requirements for the grade of the pellets entering the furnace, usually requiring an iron content (TFe) ≥ 66%, and the content of impurities (such as FeO, SiO2) must be strictly controlled. If low-grade ores (iron content of about 30%) are used, the FeO and gangue content in DRI will increase significantly (FeO ≥ 20%, gangue ≥ 6%), resulting in an increase in slag volume and reduced efficiency during subsequent electric furnace or converter smelting, which seriously restricts the utilization of low-grade iron ore resources. At present, the dependence on foreign iron ore exceeds 80%, and there is an urgent need to develop efficient reduction and smelting technologies suitable for low-grade ores to improve resource utilization.

[0003] In the prior art, the DRI melting process has the following defects:

[0004] Although the melting device disclosed in the patent document with application number 202410782006.2 can achieve the melting of metallized pellets, there is no reduction function in the furnace. The FeO remaining in the low-grade DRI cannot be deeply reduced before melting, resulting in low metallization rate and insufficient yield.

[0005] Patent document with application number 202410756095.3 adopts a vertical furnace structure to achieve reduction and smelting, but the furnace body is high, the investment cost is high, and there are strict requirements on the shape and uniformity of the pellets, making it difficult to ensure sufficient contact between the reducing gas and the material.

[0006] The patent document with application number 202210086538.3 uses rotary kiln pre-reduction combined with melting furnace treatment, but relies on residual coal as a reducing agent, which is contrary to the goal of reducing greenhouse gas emissions. In addition, the process is complex and the melting efficiency is limited.

[0007] In summary, existing technologies struggle to achieve economically and efficiently deep reduction and smelting of low-grade DRI, resulting in wasted resources and increased smelting costs. Therefore, there is an urgent need for a device and process that integrates reduction and smelting functions and adapts to the characteristics of low-grade ores. This can improve the DRI metallization rate and slag-iron separation efficiency, thereby promoting the efficient utilization of low-grade iron ore.

[0008] In view of this, the inventors, based on many years of experience in production design in this field and related fields, have designed a reduction smelting furnace and a reduction smelting method for producing DRI from low-grade ore after repeated experiments, in order to solve the problems existing in the prior art. Summary of the Invention

[0009] The object of the present invention is to provide a reduction smelting furnace and a reduction smelting method for producing DRI from low-grade ore, which can perform reduction smelting on DRI produced from low-grade ore.

[0010] In order to achieve the above-mentioned purpose of the invention, the present invention proposes a reduction smelting furnace, wherein the reduction smelting furnace includes a smelting furnace body, a material receiving orifice plate, a gas blowing device and an electrode. The interior of the smelting furnace body is hollow and forms a furnace cavity. The material receiving orifice plate is arranged in the furnace cavity and divides the furnace cavity into a reduction chamber and a molten pool arranged upper and lower. The material receiving orifice plate is spliced ​​by at least two orifice plate bodies, and at least two orifice plate bodies can be opened and closed. When the at least two orifice plate bodies are closed, the material receiving orifice plate receives DRI. When the at least two orifice plates are opened, DRI falls into the molten pool. The gas blowing device is arranged in the furnace cavity and blows reducing gas to the DRI on the material receiving orifice plate. The electrode is inserted into the molten pool for energizing to generate an arc to melt the DRI.

[0011] The present invention also proposes a reduction melting method for producing DRI from low-grade ore, wherein the reduction melting method includes: conveying the low-grade DRI to a material-receiving orifice plate, blowing reducing gas through a gas blowing device, the reducing gas passing through the material-receiving orifice plate to contact the low-grade DRI and reducing FeO in the low-grade DRI to Fe; allowing the reduced low-grade DRI to fall into a melting chamber, using electrodes to melt the low-grade DRI in the melting chamber, and using the flue gas generated when the reduced low-grade DRI is melted to heat the reducing gas and the low-grade DRI on the material-receiving orifice plate.

[0012] Compared with the prior art, the present invention has the following characteristics and advantages:

[0013] The reduction smelting furnace and the reduction smelting method for producing DRI from low-grade ores proposed in the present invention address the problems in the prior art of the inability to fully reduce FeO during the reduction smelting of low-grade DRI, resulting in low metallization rate, low yield, waste of resources, and increased smelting costs. By arranging a material-bearing orifice plate composed of rotatable orifice plates in the upper section of the smelting furnace to form a reduction section, and coordinating the gas blowing device to blow reducing gas and utilizing the high-temperature CO flue gas generated by the melting of DRI in the lower section of the smelting furnace, further efficient reduction of FeO in low-grade DRI is achieved, effectively improving the metallization rate and yield of DRI, maximizing the utilization of low-grade ore resources, and reducing resource waste and costs in the smelting process. At the same time, the method further optimizes the reduction process by controlling the injection of reducing gas through real-time monitoring of CO concentration, and setting precise flow parameters for different reducing gases, thereby ensuring the stability and reliability of the reduction effect, meeting the requirements of the invention for the effective reduction smelting of DRI produced from low-grade ores, and solving the defects of the prior art in the background technology.

[0014] The present invention proposes a reduction smelting furnace and a reduction smelting method for producing DRI from low-grade ores. The present invention fully contacts the low-grade DRI with the reducing gas on the receiving orifice plate, and combines the self-produced high-temperature flue gas generated by the melting of the molten pool electrodes with the recycling of the high-temperature flue gas to the reduction stage, forming a dual strengthening mechanism of "gas reduction + thermal reduction", so that FeO is deeply reduced to metallic iron, significantly improving the DRI metallization rate and yield; the flue gas is recycled to preheat the reducing gas and DRI, reducing energy consumption and avoiding dependence on external heat sources; the integrated process simplifies the traditional segmented process, reducing equipment investment and operational complexity, while hydrogen-based reduction replaces high-carbon fuels, significantly reducing greenhouse gas emissions. This method solves the core problems of high FeO residue and low smelting efficiency in DRI produced from low-grade ores, achieving a dual improvement in resource utilization and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the drawings are merely illustrative and are used to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the various components of the present invention. Those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to specific circumstances under the guidance of the present invention.

[0016] Figure 1 It is a schematic diagram of the melting furnace design of the present invention.

[0017] Description of the accompanying figures:

[0018] 1. Reduction smelting furnace; 2. Furnace cover;

[0019] 3. Graphite electrode; 4. DRI;

[0020] 5. Slag liquid; 6. Iron liquid;

[0021] 7. Graphite bricks; 8. Refractory layer;

[0022] 9. Insulation layer; 10. Taphole;

[0023] 11. Slag outlet; 12. Gas injection port;

[0024] 13. Rotating shaft; 14. Material receiving hole plate;

[0025] 15. Side sealing plate; 16. Smoke collection device;

[0026] 17. Hopper; 18. DRI feeding pipe;

[0027] 19. CO gas detector. DETAILED DESCRIPTION

[0028] The details of the present invention can be more clearly understood by referring to the accompanying drawings and the description of the specific embodiments of the present invention. However, the specific embodiments of the present invention described herein are only for the purpose of explaining the present invention and are not to be construed as limiting the present invention in any way. Based on the teachings of the present invention, a skilled person can conceive of any possible variations based on the present invention, and such variations should be considered to fall within the scope of the present invention.

[0029] The reduction smelting furnace 1 proposed by the present invention is as follows Figure 1 As shown, the reduction smelting furnace 1 includes a smelting furnace body, a receiving orifice plate 14, a gas blowing device and an electrode. The interior of the smelting furnace body is hollow and forms a furnace cavity. The receiving orifice plate is arranged in the furnace cavity and divides the furnace cavity into a reduction chamber and a molten pool arranged upper and lower. The receiving orifice plate is spliced ​​by at least two orifice plate bodies, and at least two orifice plate bodies can be opened and closed. When the at least two orifice plate bodies are closed, the receiving orifice plate receives direct reduced iron 4 (DRI). When the at least two orifice plates are opened, DRI falls into the molten pool. The gas blowing device is arranged in the furnace cavity and blows reducing gas to the DRI on the receiving orifice plate. The electrode is inserted into the molten pool for energizing to generate an arc to melt the DRI.

[0030] The reduction smelting furnace 1 proposed in this invention uses an openable and closable material-bearing orifice plate structure to separate the furnace chamber into a reduction chamber and a molten pool. This allows low-grade DRI to be evenly distributed in the reduction chamber and fully contacted with the injected reducing gas, achieving efficient reduction of FeO. The dynamic closure function of the orifice plate ensures that the reduced DRI precisely falls into the molten pool, and combined with electrode arc melting technology, slag and iron separation are rapidly achieved. This structural design addresses the shortcomings of traditional processes such as insufficient reduction before smelting, uneven DRI distribution, and segmented equipment operation, significantly improving metallization and yield. The integrated device also reduces equipment complexity and energy consumption, providing a compact and economical solution for efficient, low-carbon smelting of low-grade mineral resources.

[0031] The present invention proposes a reduction melting method for producing DRI from low-grade ore, which includes:

[0032] The low-grade DRI is transported to the receiving orifice plate, and reducing gas is blown through the gas blowing device. The reducing gas passes through the receiving orifice plate and contacts the low-grade DRI, reducing the FeO in the low-grade DRI to Fe. The reduced low-grade DRI falls into the melting chamber, and the low-grade DRI in the melting chamber is melted by electrodes. The flue gas generated when the reduced low-grade DRI is melted is used to heat the reducing gas and the low-grade DRI on the receiving orifice plate.

[0033] Specifically, low-grade DRI is evenly distributed on the receiving orifice plate in the upper section of the smelting furnace 1 through a hopper and a feeding pipe. The receiving orifice plate is composed of two rotatable semi-circular steel plates, which form a stable bearing surface when closed; a gas blowing device sprays reducing gas (such as hydrogen-rich gas, pure hydrogen or coke oven gas) with an adapted flow rate from below the orifice plate. The gas penetrates the through holes of the orifice plate and fully contacts the DRI, effectively reducing FeO to metallic iron; after the reduction is completed, the rotating shaft 13 drives the orifice plate to open, and the DRI falls into the molten pool. The graphite electrode 3 is energized to generate an arc to melt the DRI to form molten iron 6 and slag liquid 5. At the same time, the high-temperature CO flue gas (900-1200°C) generated during the melting process rises to the reduction section, preheating the DRI and the reducing gas to form a self-circulating heat energy cycle; the CO gas detector 19 monitors the CO concentration below the reduction section in real time, and automatically stops the gas blowing when it reaches 50%, ensuring precise control of the reaction; the molten iron 6 and the slag liquid 5 are separated and discharged through the iron outlet 10 and the slag outlet 11 respectively, realizing efficient separation of slag and iron.

[0034] The present invention proposes a reduction melting method for producing DRI from low-grade ore. This method involves conveying the low-grade DRI onto a receiving orifice plate. A gas injection device then blows reducing gas through the plate into contact with the DRI, reducing FeO to Fe and improving the metallization ratio. The reduced DRI then falls into a molten pool. The flue gas generated by the electrode melting the DRI is used to preheat the reducing gas and DRI, improving reduction efficiency. This method addresses the issue of insufficient reduction of low-grade DRI in existing technologies, achieving efficient resource utilization and cost reduction.

[0035] In an optional embodiment of the present invention, a hopper and a feeding pipe are provided on the top of the smelting furnace body for feeding low-grade DRI;

[0036] The material receiving plate 14 is provided at the upper section of the melting furnace 1. The material receiving plate 14 is composed of two semicircular steel plates, which are connected by a rotating shaft 13 and can be relatively closed to form a complete ring, and is used to carry low-grade DRI;

[0037] The gas injection port 12 is provided on the side wall of the smelting furnace 1 and is used to introduce reducing gas;

[0038] A graphite electrode 3 is provided at the center of the melting furnace 1. The graphite electrode 3 passes through the center hole of the furnace cover of the melting furnace 1 to the lower section of the melting furnace 1 and is used to generate an arc to melt the DRI.

[0039] A CO gas detector 19 is used to monitor the CO concentration in the lower area of ​​the receiving orifice plate 14 in real time;

[0040] The iron outlet 10 and the slag outlet 11 are respectively located at the bottom of the smelting furnace 1 and are used to separate the molten iron 6 and the slag liquid 5;

[0041] A flue gas collection device connected to the top of the smelting furnace 1 for recovering high-temperature flue gas;

[0042] The reducing gas contacts the low-grade DRI through the small holes of the receiving plate 14, reducing FeO to generate Fe. The high-temperature CO flue gas generated in the lower section of the smelting furnace 1 rises to the reduction section to heat the DRI and the reducing gas.

[0043] In an optional example of this embodiment, the power supply intensity of the graphite electrode 3 is 0.4 to 0.8 MVA / t DRI, preferably 0.6 MVA / t DRI. The graphite electrode 3 is connected to an external power supply system via a cable. The power supply system is equipped with a power regulation module to dynamically adjust the power supply intensity to 0.4 to 0.8 MVA / t DRI (preferably 0.6 MVA / t DRI) according to the DRI processing volume. The electrode is vertically inserted into the molten pool and maintains a non-contact state with the DRI in the molten pool. When energized, a high-temperature arc is generated that directly acts on the DRI material layer, causing it to melt into molten iron 6 and slag liquid 5. The setting range of the power supply intensity is based on the comprehensive optimization of the metallization rate of the DRI, the molten pool temperature, and the energy consumption economy. The preferred value of 0.6 MVA / t DRI can balance the melting efficiency and energy cost.

[0044] In an optional embodiment of the present invention, the aperture of the small holes of the material receiving orifice plate 14 is 3 to 8 mm in diameter, the hole spacing is 10 to 20 mm, and the steel plate thickness is 10 to 15 mm. The material receiving orifice plate 14 is made of a high-temperature resistant alloy, and its through holes are evenly distributed, with an aperture range of 3 to 8 mm, a hole spacing of 10 to 20 mm, and a steel plate thickness of 10 to 15 mm; the adaptive design of the aperture and hole spacing ensures that the reducing gas forms a uniform airflow when passing through the small holes, covering the entire DRI material layer, and avoiding excessive or weak local airflow; the steel plate thickness of 10 to 15 mm provides sufficient structural strength to bear the weight of DRI and resist high-temperature deformation, while ensuring that the gas penetration resistance is within a reasonable range. The material receiving orifice plate 14 is fixed to the inner wall of the smelting furnace 1 by welding or bolts, and is connected to the rotating shaft 13 to realize the opening and closing function.

[0045] In an optional embodiment of the present invention, one end of each orifice plate body can be rotatably connected to the melting furnace body, and the other end of the orifice plate body can be rotated horizontally to open. The orifice plate body is composed of two semi-circular ring-shaped material-bearing orifice plates 14. One end of each orifice plate body is rotatably connected to the inner wall of the melting furnace body through a rotating shaft 13, and the other end can swing horizontally around the rotating shaft 13. When the orifice plate body is in a horizontally closed state, the two semi-circular ring steel plates are tightly connected to form a complete circular bearing surface for evenly distributing low-grade DRI; when blanking is required, the drive mechanism controls the orifice plate body to rotate horizontally around the rotating shaft 13 to open, so that the reduced DRI slides evenly into the molten pool along the gap between the orifice plates. The horizontal opening and closing state switching of the orifice plate body is achieved through the mechanical transmission of the rotating shaft 13.

[0046] In an optional embodiment of the present invention, the receiving orifice plate 14 can be rotated 20 to 30 minutes after the low-grade DRI enters the hopper 17 above the smelting furnace 1 to allow the reduced low-grade DRI to fall into the molten pool.

[0047] In another optional embodiment of the present invention, the orifice plate body can also adopt a horizontal pull-out type, a flip-over type or other opening and closing forms familiar to those skilled in the art.

[0048] In an optional embodiment of the present invention, the orifice plate body is made of heat-resistant steel.

[0049] In an optional embodiment of the present invention, the electrode is vertically arranged and passes through the receiving orifice plate, and a side sealing plate is provided around the electrode in the reduction chamber. The side sealing plate is used to separate the electrode and the DRI, and the receiving orifice plate and the side sealing plate are respectively spaced apart from the electrode. The electrode is vertically arranged and passes through the center of the receiving orifice plate, with its lower end extending into the molten pool and its upper end fixed to the top of the smelting furnace 1; the side sealing plates are arranged circumferentially around the electrode, forming an annular gap between the outer wall of the electrode, the bottom of the side sealing plates is connected to the receiving orifice plate, and the top is connected to the inner wall of the smelting furnace 1; there is a slit between the bottom of the side sealing plate and the receiving orifice plate, and an annular gap is also retained between the receiving orifice plate and the electrode to ensure that the heat generated when the electrode is energized will not be directly conducted to the receiving orifice plate. The side sealing plates are sealed and fixed to the inner wall of the smelting furnace 1 by refractory materials to form an independent isolation space to prevent DRI from contacting the electrode or leaking from the gap.

[0050] In an optional embodiment of the present invention, a gas blowing device is provided below the material receiving orifice plate, and the reducing gas blown by the gas blowing device enters the reduction chamber through a plurality of through holes on the material receiving orifice plate. The gas blowing device is fixedly installed below the material receiving orifice plate, and its blowing port is directly opposite the through holes of the material receiving orifice plate; a plurality of through holes are evenly distributed on the material receiving orifice plate, and the aperture and the hole spacing are designed according to the reducing gas flow rate and the DRI particle size, to ensure that the gas is evenly diffused into the reduction chamber after penetrating the orifice plate; the gas blowing device is connected to an external gas source through a pipeline, and the blown reducing gas (such as hydrogen-rich gas, pure hydrogen or coke oven gas) flows vertically upward through the through holes, passes through the DRI material layer, and undergoes a reduction reaction with FeO. The gas blowing device is sealed with a flange to the furnace chamber wall to prevent gas leakage.

[0051] In an optional embodiment of the present invention, a CO gas detector 19 is further provided in the furnace chamber, and the CO gas detector 19 is located below the material receiving orifice plate. The CO gas detector 19 is fixedly mounted on the side wall of the furnace chamber below the material receiving orifice plate, with its probe facing the area between the gas injection device and the material receiving orifice plate, for real-time collection of CO concentration data in this area; the detector is sealed and fixed to the furnace chamber wall by a flange or threaded connection to prevent leakage of high-temperature flue gas; the signal output end of the detector is electrically connected to the control system of the gas injection device. When the CO concentration reaches a preset threshold (such as 50%), the control system automatically shuts down the gas injection device and stops the supply of reducing gas.

[0052] In an optional embodiment of the present invention, a feeding device for adding DRI into the furnace cavity is provided on the top of the melting furnace body. The feeding device consists of a hopper and a feeding pipe. The hopper is welded or bolted to the top of the melting furnace body, and its bottom outlet is sealed with the feeding pipe via a flange. The feeding pipe extends vertically into the furnace cavity, with its lower end opening facing the surface of the receiving orifice plate, ensuring that low-grade DRI falls evenly onto the receiving orifice plate along the feeding pipe through gravity. The feeding pipe is isolated from the furnace cavity top cover by a high-temperature resistant sealing ring to prevent high-temperature flue gas from escaping. The hopper capacity of the feeding device is adapted to the processing capacity of the melting furnace 1, enabling continuous or intermittent feeding.

[0053] In an optional embodiment of the present invention, a flue gas outlet and a flue gas collection device 16 are provided at the top of the melting furnace body. The flue gas outlet is located approximately one-quarter of the circumference of the furnace cover 2 on the top of the melting furnace body, and its outlet end is sealed with the inlet pipe of the flue gas collection device via a flange. The flue gas collection device includes a dust collector and a waste heat recovery unit. The high-temperature flue gas passes through the dust collector to remove particulate matter and then enters the waste heat recovery unit, which converts the thermal energy in the flue gas into a usable heat source (such as preheated reducing gas or DRI). The purified gas is finally discharged or reused through the exhaust port. The flue gas outlet is isolated from the furnace cavity by high-temperature resistant material to prevent flue gas leakage and maintain pressure balance in the furnace.

[0054] In an optional embodiment of the present invention, the flue gas outlet connected to the flue gas collection device 16 is provided with a waste heat collection device for recycling the heat energy of the high-temperature flue gas to the reducing gas preheating system. The waste heat collection device includes a heat exchanger and a connecting pipe. The heat exchanger is sealed with the flue gas outlet via a flange. When the high-temperature flue gas passes through the heat exchanger, it exchanges heat with the cold air flow of the reducing gas preheating system. After the flue gas temperature is reduced, it enters the dust removal unit for processing; the hot side outlet of the heat exchanger is connected to the air inlet of the reducing gas preheating system via a pipe, and the recovered heat energy is used to heat the reducing gas (such as hydrogen-rich gas or coke oven gas) to increase the reducing gas inlet temperature; the waste heat collection device and the flue gas collection device are wrapped with high-temperature resistant insulation material to reduce heat energy loss.

[0055] In an optional embodiment of the present invention, a slag outlet 11 is used to separate the slag liquid 5. The iron outlet 10 is opened at the bottom of the smelting furnace 1 near the lowest point of the molten pool, and the slag outlet 11 is located in the upper layer of the molten pool near the area where the slag liquid 5 accumulates. The opening and closing of both the iron outlet 10 and the slag outlet 11 are controlled by high-temperature resistant valves or baffles. The inner wall of the iron outlet 10 is lined with refractory material to withstand the high-temperature erosion of the molten iron 6. The diameter of the slag outlet 11 is slightly larger than that of the iron outlet 10 to accommodate the fluidity difference of the slag liquid 5. After the molten iron 6 and the slag liquid 5 are naturally stratified in the molten pool based on the density difference, they are discharged separately through independent outlets. The iron outlet 10 is opened first to discharge the lower layer of molten iron 6, and then the slag outlet 11 is opened to discharge the upper layer of slag liquid 5 to avoid mixing.

[0056] In an optional example of the present invention, the smelting furnace body includes a refractory layer 8 and a thermal insulation layer 9. The refractory layer 8 protects the smelting furnace body from direct erosion by high-temperature melt (molten iron, slag) and arc heat, thereby extending the life of the furnace body; the thermal insulation layer 9 reduces the heat loss from the furnace to the outside, maintains the high-temperature environment of the smelting furnace, and reduces energy consumption.

[0057] In an optional embodiment of the present invention, the reducing gas is hydrogen-rich gas (H2+CO), pure hydrogen gas (H2) or coke oven gas; wherein:

[0058] When using hydrogen-rich gas, the gas flow rate is 0.4-0.5Nm 3 / (min·t DRI);

[0059] When pure hydrogen gas is used, the gas flow rate is 0.2~0.3Nm 3 / (min·t DRI);

[0060] When using coke oven gas, the gas flow rate is 0.7~0.9Nm 3 / (min·t DRI).

[0061] The gas injection device is connected to the external gas source through a flow control valve. The corresponding flow parameters are set according to the selected gas type (hydrogen-rich gas, pure hydrogen or coke oven gas); the hydrogen-rich gas flow rate is 0.4~0.5Nm 3 / (min·t DRI), the mixing ratio of H2 and CO is controlled by the gas distribution module, and the pure hydrogen gas flow rate is 0.2~0.3Nm 3 / (min·t DRI) when using high-purity hydrogen source and coke oven gas flow rate of 0.7~0.9Nm 3 / (min·t DRI) when impurities are removed through pretreatment; the gas blowing device is aligned with the through hole of the receiving plate to ensure that the gas penetrates the DRI layer evenly.

[0062] In another optional embodiment of the present invention, the CO concentration in the area below the material receiving orifice plate is monitored in real time. When the CO concentration reaches 50%, the injection of reducing gas is stopped. The CO gas detector 19 is fixedly installed on the side wall of the furnace chamber below the material receiving orifice plate. Its detection probe faces the area between the gas blowing device and the orifice plate. It is connected to the furnace wall through a high-temperature resistant sealing structure to collect CO concentration data in real time. The signal output end of the detector is electrically connected to the control system of the gas blowing device. When the CO concentration reaches the 50% threshold, the control system immediately closes the flow control valve of the gas blowing device, cutting off the reducing gas supply. The installation position of the detector matches the gas flow path to ensure that the monitoring data accurately reflects the progress of the reduction reaction.

[0063] In another optional embodiment of the present invention, the reducing gas is hydrogen-rich gas (H2+CO), pure hydrogen gas (H2) or coke oven gas; wherein:

[0064] When the reducing gas is hydrogen-rich gas, the gas flow rate is 0.4-0.5 Nm 3 / (min·t DRI);

[0065] When the reducing gas is pure hydrogen, the gas flow rate is 0.2-0.3 Nm 3 / (min·t DRI);

[0066] When the reducing gas is coke oven gas, the gas flow rate is 0.7~0.9Nm 3 / (min·t DRI).

[0067] The gas injection device is connected to the external gas source through a flow control valve. The corresponding flow parameters are set according to the selected gas type (hydrogen-rich gas, pure hydrogen or coke oven gas); the hydrogen-rich gas flow rate is 0.4~0.5Nm 3 / (min·t DRI), the ratio of H2 and CO is adjusted by the gas distribution module to adapt to different reduction requirements; the pure hydrogen gas uses a high-purity hydrogen source with a flow rate of 0.2~0.3Nm 3 / (min·t DRI), directly delivered through the injection port; coke oven gas needs to be pre-treated to remove impurities and then be 0.7~0.9Nm 3 The gas injection port 12 is aligned with the through hole of the material receiving plate to ensure that the gas evenly penetrates the DRI layer and covers the material surface.

[0068] The present invention also proposes a method for processing low-grade DRI based on the aforementioned reduction smelting furnace, which comprises the following steps:

[0069] S1. The low-grade DRI is transported to the receiving orifice plate 14 through the hopper and feeding pipe;

[0070] S2. A reducing gas is introduced through the gas injection port 12, passing through the orifice plate 14 and contacting the DRI to reduce FeO to generate Fe;

[0071] S3 starts the graphite electrode 3 is energized to form the DRI arc melting molten iron and slag liquid 6 5;

[0072] S4 monitors the CO concentration in the lower region of the orifice plate 14, and stops introducing the reducing gas when the CO concentration is ≥50%;

[0073] S5 separation of liquid iron and slag liquid 6 5, and discharged through the taphole 10 and the slag outlet 11;

[0074] S6. Collect high-temperature flue gas from the upper section of the smelting furnace and achieve zero emissions after waste heat recovery.

[0075] The method for processing low-grade DRI in a reduction smelting furnace is implemented based on the above-mentioned reduction smelting furnace structure, and the specific process is: low-grade DRI is evenly distributed on the receiving orifice plate 14 through a hopper and a feeding pipe, and a supporting surface is formed when the receiving orifice plate 14 is closed; a gas blowing device blows reducing gas (hydrogen-rich gas, pure hydrogen or coke oven gas) of an appropriate flow rate from below the orifice plate, and the gas penetrates the through-holes of the orifice plate and contacts the DRI, completing the reduction of FeO→Fe; after the reduction is completed, the receiving orifice plate 14 is opened to allow the DRI to fall into the molten pool, and the graphite electrode 3 is energized to generate an arc to melt the DRI, forming layered molten iron 6 and slag liquid 5; the CO gas detector 19 monitors the CO concentration below the orifice plate in real time, and stops the gas when it reaches 50%; the molten iron 6 and slag liquid 5 are discharged through the iron outlet 10 and the slag outlet 11 respectively; the high-temperature flue gas from the upper section of the smelting furnace is purified and discharged after recovering heat energy through the waste heat unit of the flue gas collection device. In another optional embodiment of the present invention, the arc melting temperature in step S3 is 1500-1600°C, and the melting time is 30-60 minutes. The graphite electrode 3 is powered by a power supply system, and its power regulation module dynamically controls the input current according to the temperature of the molten pool, so that the arc is stably maintained in the range of 1500-1600°C; the electrode is vertically inserted into the molten pool and energized non-contactly with the DRI, and the DRI is melted into molten iron 6 and slag liquid 5 by arc heat energy; the melting time is set to 30-60 minutes, and the molten pool state (such as the fluidity of the molten iron 6 and the stratification of the slag liquid 5) is monitored in real time by the PLC control system to ensure that efficient melting is completed within the time range; the temperature in the molten pool is fed back to the control system through a thermocouple to achieve closed-loop temperature control.

[0076] The specific implementation process of the reduction smelting furnace and the reduction smelting method for producing DRI from low-grade ore proposed in the present invention will now be described in detail with reference to an embodiment. In this embodiment, the design scheme is based on a 60t smelting furnace.

[0077] The hopper at the top of the melting furnace is loaded with low-grade DRI, which then falls through the feeding pipe onto the receiving plate 14 at the upper section of the melting furnace. A side sealing plate 15 is provided between the receiving plate 14 and the electrode to prevent DRI from falling into the melting furnace.

[0078] The reducing gas is introduced into the gas injection port 12. The reducing gas can be hydrogen-rich gas (H2+CO) or pure hydrogen gas (H2) or coke oven gas. When hydrogen-rich gas (H2+CO) is used, the gas flow rate is 0.4Nm 3 / (min·tDRI); when pure hydrogen gas (H2) is used, the gas flow rate is 0.2Nm 3 / (min·t DRI); when coke oven gas is used, the gas flow rate is 0.9Nm 3 / (min·t DRI);

[0079] The reducing gas in the smelting furnace contacts the low-grade DRI through the receiving hole plate 14, and a reduction reaction occurs, and the FeO in the DRI is reduced to Fe;

[0080] The rotating shaft 13 connected to the rotating receiving plate 14 allows the reduced DRI to fall into the molten pool in the lower section of the smelting furnace;

[0081] Start the melting furnace and energize the graphite electrode 3 with a power supply intensity of 0.6MVA / t DRI. The arc generated by the electrode melts the DRI.

[0082] During the DRI melting process, high-temperature flue gases such as CO generated by oxidation of carbon in DRI, graphite electrodes 3, and graphite bricks 7 rise to the reduction section, where they heat the reducing gas and low-grade DRI.

[0083] The CO gas detector 19 monitors the CO concentration in the lower area of ​​the material receiving orifice 14 in the smelting furnace in real time. When the CO concentration reaches 50%, the gas injection port 12 stops blowing the reducing gas.

[0084] After DRI is melted in the smelting furnace, molten iron 6 and molten slag 5 are formed and separated into layers, with slag 5 in the upper layer and molten iron 6 in the lower layer.

[0085] Open the iron tapping hole 10 and the slag tapping hole 11, and the molten iron 6 and the slag liquid 5 flow out through the iron tapping hole 10 and the slag tapping hole 11 respectively, so as to separate the slag and the iron;

[0086] The flue gas generated in the upper section of the smelting furnace enters the flue gas collection device to achieve zero emissions.

[0087] The detailed explanations of the above-mentioned embodiments are intended only to explain the present invention so as to facilitate a better understanding of the present invention. However, these descriptions cannot be interpreted as limiting the present invention for any reason. In particular, the various features described in different embodiments may also be arbitrarily combined with each other to form other embodiments. Unless otherwise clearly described, these features should be understood to be applicable to any embodiment and are not limited to the described embodiments.

Claims

1. A reduction smelting furnace, characterized in that: The reduction smelting furnace includes a smelting furnace body, a material receiving orifice plate, a gas blowing device and an electrode. The interior of the smelting furnace body is hollow and forms a furnace cavity. The material receiving orifice plate is arranged in the furnace cavity and divides the furnace cavity into a reduction chamber and a molten pool arranged upper and lower. The material receiving orifice plate is spliced ​​by at least two orifice plate bodies. At least two of the orifice plate bodies can be opened and closed. When at least two of the orifice plate bodies are closed, the material receiving orifice plate receives DRI. When at least two of the orifice plates are opened, the DRI falls into the molten pool. The gas blowing device is arranged in the furnace cavity and blows reducing gas to the DRI on the material receiving orifice plate. The electrode is inserted into the molten pool for energizing to generate an arc to melt the DRI.

2. The reduction smelting furnace according to claim 1, characterized in that: One end of each of the orifice plates is rotatably connected to the smelting furnace body, and the other end of the orifice plate can be horizontally rotated and opened.

3. The reduction smelting furnace according to claim 1, characterized in that: The electrode is vertically arranged and passes through the material receiving hole plate. A side sealing plate is arranged around the electrode in the reduction chamber. The side sealing plate is used to separate the electrode and the DRI. The material receiving hole plate and the side sealing plate are respectively spaced apart from the electrode.

4. The reduction smelting furnace according to claim 1, characterized in that: The gas blowing device is arranged below the material receiving orifice plate, and the reducing gas blown by the gas blowing device enters the reduction chamber through a plurality of through holes on the material receiving orifice plate.

5. The reduction smelting furnace according to claim 1, characterized in that: A CO gas detector is also provided in the furnace chamber and is located below the material receiving orifice plate.

6. The reduction smelting furnace according to claim 1, characterized in that: A feeding device for adding the DRI into the furnace cavity is provided on the top of the melting furnace body.

7. The reduction smelting furnace according to claim 1, characterized in that: A smoke outlet and a smoke collecting device are provided on the top of the smelting furnace body.

8. The reduction smelting furnace according to claim 1, characterized in that: The bottom of the smelting furnace body is provided with an iron outlet and a slag outlet. The iron outlet is used to separate the molten iron, and the slag outlet is used to separate the slag liquid.

9. A reduction smelting method for producing DRI from low-grade ore, based on the reduction smelting furnace according to any one of claims 1 to 8, characterized in that: The reduction melting method comprises: Low-grade DRI is transported to the receiving orifice plate, and reducing gas is blown through the gas blowing device. The reducing gas passes through the receiving orifice plate and contacts the low-grade DRI, reducing FeO in the low-grade DRI to Fe. The reduced low-grade DRI is allowed to fall into a melting chamber, and the low-grade DRI in the melting chamber is melted by electrodes. The flue gas generated when the reduced low-grade DRI is melted is used to heat the reducing gas and the low-grade DRI on the receiving orifice plate.

10. The reduction smelting method for producing DRI from low-grade ore according to claim 9, characterized in that: The CO concentration in the area below the receiving orifice plate is monitored in real time, and when the CO concentration reaches 50%, the blowing of the reducing gas is stopped.

11. The reduction smelting method for producing DRI from low-grade ore according to claim 9, characterized in that: The reducing gas is hydrogen-rich gas, pure hydrogen gas or coke oven gas; wherein, When the reducing gas is hydrogen-rich gas, the gas flow rate is 0.4-0.5 Nm 3 / (min·t DRI); When the reducing gas is pure hydrogen gas, the gas flow rate is 0.2-0.3 Nm 3 / (min·t DRI); When the reducing gas is coke oven gas, the gas flow rate is 0.7-0.9 Nm 3 / (min·t DRI).

Images