Zero oxygen injection low carbon ironmaking method

Abstract

The present application relates to a kind of zero oxygen injection low carbon ironmaking method, belong to non high carbon metallurgy technical field.The method includes: hot self-fluxing oxidized pellet is loaded from furnace top into gas-based shaft furnace, cold reduction gas is injected from the bottom of gas-based shaft furnace into gas-based shaft furnace, while hot reduction gas is injected from the junction of reduction section and cooling section of gas-based shaft furnace into gas-based shaft furnace, the cold reduction gas is heated and mixed with the hot reduction gas during ascending, and then pre-reduction reaction occurs with self-fluxing oxidized pellet, and hot direct reduced iron is obtained, and the hot direct reduced iron is cooled by cold reduction gas in cooling section, and direct reduced iron is obtained;Solid carbon material and direct reduced iron are loaded from the top of zero oxygen injection furnace, and superheated reduction gas is injected into zero oxygen injection furnace, and direct reduced iron is reduced and melted, and liquid slag and molten iron are obtained.The present application reduces gas heating energy consumption, and compared with blast furnace, carbon emission is significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of non-blast furnace low-carbon metallurgical technology, and specifically relates to a zero-oxygen injection low-carbon ironmaking method. Background Technology

[0002] Currently, the main mature ironmaking processes include blast furnace ironmaking, smelting reduction (HIsmelt, COREX, Finex), and direct reduction (gas-based direct reduction, coal-based direct reduction), etc. Each existing process has its own advantages and disadvantages, mainly:

[0003] 1. Blast furnace ironmaking technology is mature and can achieve an annual production capacity of over one million tons per unit. However, its drawback is its over-reliance on high-quality metallurgical coke, with the industry average solid fuel consumption being 0.55 kg / t. 铁水 It requires the construction of supporting coking, sintering, and pelletizing facilities, resulting in large system investments; blast furnace operation is difficult, and it is hard to recover after furnace conditions become abnormal or fluctuate; it also has high costs, carbon emissions, and energy consumption.

[0004] 2. Melt reduction

[0005] (1) The heat transfer effect of the HIsmelt process is poor, the temperature of the molten iron in the molten pool is low at only 1400-1450℃, and the flue gas flow rate is as high as 2700Nm. 3 The temperature of the iron and flue gas reaches 1600℃, and a large amount of physical heat is lost outside the furnace with the flue gas; the iron loss is high, the fuel consumption is high, and the carbon emissions are high.

[0006] (2) COREX and Finex have high iron [Si] content, excessive gas production, and high primary carbon consumption.

[0007] (3) The chemical energy utilization rate of carbon is insufficient. Some carbon elements escape with the coal gas in the form of CO and cannot be further utilized for their chemical energy.

[0008] 3. Direct restoration

[0009] Direct reduction is a process of smelting iron ore into iron through solid-state reduction below the ore's melting temperature. Iron produced using this method is called direct reduced iron (DRI). Depending on the reducing agent, it can be divided into two main categories: gas-based direct reduction and coal-based direct reduction. Gas-based reduction is the mainstream and dominant process globally.

[0010] Coal-based direct reduction requires solid fuel, resulting in high carbon consumption. From the perspective of green and low-carbon development in the steel industry, coal-based direct reduction cannot solve the problem of reducing carbon emissions in ironmaking, and it also has high requirements for ore quality.

[0011] Gas-based shaft furnaces currently represent the process with the greatest potential for carbon reduction, accounting for 75.3% of total direct reduction output (of which MIDREX accounts for 60.0%, HYL for 12.4%, and PERED for 2.9%). However, existing gas-based shaft furnace processes have the following drawbacks:

[0012] (1) High raw material costs and difficulty in promotion: The existing gas-based shaft furnace process uses electric arc furnace deep melting for direct reduction of iron, which requires the pellets to have TFe > 67% and SiO2 < 3.0%. Without high-grade pellets, the electric arc furnace will produce a large amount of slag in the subsequent smelting. Since the electric arc furnace production process does not involve a large amount of gas injection and stirring like a blast furnace, its production process has poor kinetic conditions. The increased slag will result in slow heat transfer, low electric arc furnace production efficiency, long smelting cycle, high energy consumption, and high costs. In my country, iron ore is mainly lean ore. The current stringent requirements of gas-based shaft furnaces on raw materials not only result in high raw material procurement costs but also make it difficult to promote gas-based shaft furnaces in my country.

[0013] (2) High gasification cost and significant safety risks. Existing gas-based vertical shaft furnaces use cold-charged pellets, with the heat required for the reaction inside the furnace carried in by heated reducing gas. To expand the high-temperature zone of 600-1100℃ inside the furnace, a higher gas temperature and a larger gas volume are needed. On the other hand, to prevent the generated sponge iron from sticking together inside the furnace, the volume ratio of H2 to CO inside the furnace must be controlled to be greater than 1:1, and the upper limit of the reducing gas temperature must be controlled to be less than 1100℃. Since the reduction of iron oxides by H2 is an endothermic reaction, this exacerbates the temperature drop inside the furnace, requiring even more gas. Because the cost of obtaining H2 is higher than that of CO, the cost of heating H2 at high temperatures is high, and the power cost of circulating and pressurizing a large amount of gas in the system is high, this is one of the reasons for the high cost and high safety risks of gas-based vertical shaft furnaces.

[0014] (3) The gas-based vertical shaft furnace-electric furnace smelting process has low operating efficiency and is difficult to scale up. The vertical shaft furnace has a large gas volume, high temperature and high hydrogen content, which requires 20 days of annual shutdown for inspection of all pipelines; the electric furnace has difficulties in continuous charging and continuous slag and iron discharge, and it is difficult to increase the furnace capacity and the reaction rate of the electric furnace.

[0015] In summary, the operating cost of existing gas-based shaft furnaces is 600 yuan / ton higher than that of conventional furnace ironmaking, and this could be approximately 1000 yuan / ton higher when converted to electric arc furnace steelmaking. Therefore, developing a low-cost, safe, and efficient gas-based direct reduction process suitable for the characteristics of China's iron ore and energy resources would play a very positive role in advancing my country's steel industry. Summary of the Invention

[0016] To address the aforementioned problems, this invention provides a zero-oxygen injection low-carbon ironmaking method. It employs a self-fluxing pellet submerged arc charge into a gas-based vertical shaft furnace. Gas from the cooling section of the gas-based vertical shaft furnace enters the reduction section as a reducing agent. A portion of the hot reducing gas is added to the reduction section of the vertical shaft furnace, yielding cold direct reduced iron (DRI) with a metallization rate exceeding 92%. DRI and solid carbon materials are added through the top of the zero-oxygen injection furnace, while superheated reducing gas is injected into the furnace hearth. The DRI is further reduced and heated within the zero-oxygen injection furnace to generate high-temperature molten iron and slag, which are discharged from the slag-iron taphole. The gaseous products generated in the gas-based vertical shaft furnace and the zero-oxygen injection furnace have their heat recovered through a heat exchanger, and after further removal of dust, CO2, and H2O, they are recycled as a gaseous reducing agent for the system. This effectively reduces the heating temperature and amount of reducing gas in the gas-based vertical shaft furnace, lowers the cost and energy consumption of deep reduction and smelting, and improves the system's operating rate.

[0017] The first objective of this invention is to provide a zero-oxygen injection low-carbon ironmaking method, the method comprising:

[0018] Hot self-fluxing oxide pellets are loaded into a gas-based vertical shaft furnace from the top of the furnace. Cold reducing gas is injected into the gas-based vertical shaft furnace from the bottom. At the same time, hot reducing gas is injected into the gas-based vertical shaft furnace from the junction of the reduction section and the cooling section. The cold reducing gas is heated during its ascent and mixes with the hot reducing gas. It then undergoes a pre-reduction reaction with the self-fluxing oxide pellets to obtain hot direct reduced iron. The hot direct reduced iron is cooled by the cold reducing gas in the cooling section to obtain direct reduced iron.

[0019] Solid carbon feed and direct reduced iron are charged from the top of a zero-oxygen injection furnace at a mass ratio of (0.03–0.1):1, with a temperature of 1800–2350℃ and a flow rate of 900–1500 Nm³. 3 / ton of superheated reducing gas is injected into a zero-oxygen injection furnace, directly reducing the iron to undergo reduction melting, yielding liquid slag and molten iron.

[0020] When the hot self-fluxing oxide pellets are charged into the gas-based vertical shaft furnace, the temperature is 600–1100°C. The self-fluxing oxide pellets are obtained by high-temperature treatment of iron ore, flux, and bentonite. This high-temperature treatment is a well-known method in the technical field and will not be described further in this embodiment. The high-temperature treatment does not include cooling of the self-fluxing oxide pellets. The temperature of the self-fluxing oxide pellets is 600°C. The temperature of 1100℃ is generated during the high-temperature processing, not by secondary heating.

[0021] Furthermore, when flux (mainly CaCO3) is added to a gas-based vertical shaft furnace or a zero-oxygen injection furnace, CaCO3 decomposes and absorbs heat, affecting the system temperature and reaction rate. Therefore, self-fluxing pellets must be used. Thus, the mass ratio of CaO:SiO2 in the self-fluxing oxide pellets is 0.9 to 1.3, and the mass percentage of Fe in the pellets is 50% to 69%.

[0022] Furthermore, the Fe element content in the self-fluxing oxide pellets is 50%–69% by mass; the direct reduced iron obtained after being cooled by cold reducing gas in the cooling section has a temperature of less than 250°C and a metallization rate of ≥92%; the solid carbon material is any one or more of coke, semi-coke, and shaped coke, and the fixed carbon content in the solid carbon material is greater than 75%; the temperature of the cold reducing gas is less than 50°C.

[0023] Furthermore, the hot reducing gas and the superheated reducing gas are reducing gas from a reducing gas holder, and the cold reducing gas is reducing gas from a reducing gas holder and / or coke oven gas.

[0024] The reducing gas in the reducing gas holder includes purified coal gas and newly replenished reducing gas. The reducing gas in the reducing gas holder consists of CO, H2, N2 and impurity gases, and the sum of the volume percentages of CO and H2 is greater than 92%.

[0025] The purified coal gas is the coal gas obtained after the top coal gas of the gas-based vertical furnace and the zero oxygen injection furnace has been purified and recovered after heat exchange and heat energy recovery.

[0026] The heat reduction gas is a gas that is pressurized, preheated by a heat exchange system, and then heated to the required temperature by a portion of the reduction gas in the reduction gas holder.

[0027] The superheated reducing gas, which is another part of the gas in the reducing gas holder, is pressurized, preheated by the heat exchange system, and then heated to the required temperature.

[0028] Furthermore, the total gas flow rate in the gas-based vertical furnace includes cold reducing gas flow rate and hot reducing gas flow rate, wherein the ratio of cold reducing gas flow rate to hot reducing gas flow rate is K;

[0029] When the reducing gas H2:CO > 5 injected into the gas-based vertical shaft furnace, the charging temperature of the self-fluxing oxidized pellets is 1050–1100℃, and the total flow rate of the reducing gas in the gas-based vertical shaft furnace is 1800–1900 Nm³. 3 / t ferrite, K ranges from 1.7 to 2.1, and the temperature of the thermal reducing gas is 1050±20℃;

[0030] When the reducing gas content injected into the gas-based vertical shaft furnace is 1.5 < H2:CO ≤ 5, the charging temperature of the self-fluxing oxidized pellets is 1000–1050℃, and the total flow rate of the reducing gas in the gas-based vertical shaft furnace is 1900–2000 Nm³.3 / t ferrite, K ranges from 1.5 to 1.8, and the temperature of the thermal reducing gas is 1000 to 1050℃;

[0031] When the reducing gas content injected into the gas-based vertical shaft furnace is 0.6 < H2:CO ≤ 1.5, the charging temperature of the self-fluxing oxidized pellets is 950–1000℃, and the total flow rate of reducing gas in the gas-based vertical shaft furnace is 2000–2100 Nm³. 3 / t ferrite, K ranges from 1.3 to 1.6, and the temperature of the thermal reducing gas is 980±20℃;

[0032] When the reducing gas content injected into the gas-based vertical shaft furnace is 0.2 < H2:CO ≤ 0.6, the charging temperature of the self-fluxing oxidized pellets is 900–950℃, and the total flow rate of reducing gas in the gas-based vertical shaft furnace is 2100–2200 Nm³. 3 / t ferrite, K ranges from 1.2 to 1.4, and the temperature of the thermal reducing gas is 950±20℃;

[0033] When the reducing gas H2:CO ≤ 0.2 injected into the gas-based vertical shaft furnace, the charging temperature of the self-melting oxidized pellets is 880–920℃, and the total flow rate of the reducing gas in the gas-based vertical shaft furnace is 2200–2300 Nm³. 3 / t ferrite, K ranges from 1.1 to 1.3, and the temperature of the thermal reducing gas is 930±20℃.

[0034] During the descent of hot self-fluxing oxide pellets in a gas-based vertical shaft furnace, they come into contact with the gas formed by the mixture of hot reducing gas and the heated cold reducing gas in the gas-based vertical shaft furnace, and undergo reduction reactions: Fe2O3+CO→Fe3O4+CO2, Fe3O4+CO→FeO+CO2, FeO+CO→Fe+CO2, and reactions: Fe2O3+H2→Fe3O4+H2O(g), Fe3O4+H2→FeO+H2O(g), FeO+H2→Fe+H2O(g), generating hot solid direct reduced iron (DRI), gaseous CO2 and H2O. This process is called the pre-reduction of self-fluxing oxide pellets, and the product after the pre-reduction of self-fluxing oxide pellets is called DRI (direct reduced iron).

[0035] Subsequently, the hot DRI continues to descend and encounters the ascending cold reducing gas, resulting in heat exchange. This causes the temperature of the cold reducing gas to rise and the temperature of the hot DRI to fall, and reactions occur: FeO + H2 → Fe + H2O (gas), FeO + CO → Fe + CO2, and / or CH4 = C + H2, and / or C + 3Fe = Fe3C, yielding cold DRI. At the same time, the temperature of the cold reducing gas rises, and it continues to ascend and mix with the hot reducing gas, contacting the self-fluxing oxide pellets and reducing them.

[0036] Finally, the cold DRI is discharged from the bottom outlet of the gas-based vertical shaft furnace, and the upper furnace charge of the gas-based vertical shaft furnace moves down in sequence; among them, the gas generated by the chemical reaction in the gas-based vertical shaft furnace and the reducing gas that has not undergone chemical reaction are collectively referred to as vertical shaft furnace gas, which is output from the gas outlet pipe at the top of the vertical shaft furnace.

[0037] Furthermore, the specific control range of the inlet flow rate and inlet temperature of the superheated reducing gas injected into the zero-oxygen injection furnace is as follows:

[0038] When the flow rate of superheated reducing gas injected into the furnace is 900–1200 Nm 3 When the ferrite content is 1 ton, the temperature of the superheated reducing gas entering the furnace is controlled at 2130~2320℃.

[0039] When the flow rate of superheated reducing gas injected into the furnace is 1200-1500 Nm 3 When the temperature of the superheated reducing gas entering the furnace is controlled at 1850~2250℃ per ton of ferrite.

[0040] In the oxygen-free injection furnace, the solid carbon material and direct reduced iron are in contact with reducing gas, wherein the direct reduced iron is deeply reduced to obtain molten iron and slag; the gas generated by the chemical reaction in the oxygen-free injection furnace and the reducing gas that has not undergone chemical reaction are collectively referred to as oxygen-free injection furnace gas, which is output from the oxygen-free injection furnace gas outlet pipe at the top of the oxygen-free injection furnace.

[0041] The second objective of this invention is to provide a zero-oxygen injection low-carbon ironmaking apparatus to achieve the above-mentioned zero-oxygen injection low-carbon ironmaking method, including a gas-based vertical shaft furnace and a zero-oxygen injection furnace.

[0042] The gas-based vertical furnace is divided into a reduction section and a cooling section from top to bottom along the internal vertical direction.

[0043] Several hot reducing gas injection inlets are symmetrically arranged on the same horizontal cross section at the junction of the reduction section and the cooling section. The reduction section is used for the pre-reduction reaction of self-fluxing oxidized pellets to obtain hot direct reduced iron.

[0044] Several cold reducing gas injection inlets are symmetrically arranged on the same horizontal cross section inside the lower part of the cooling section. The cooling section is used to cool the hot direct reduced iron to obtain cold direct reduced iron.

[0045] The direct reduced iron discharged from the bottom of the cooling section is transported to the zero oxygen injection furnace. The zero oxygen injection furnace is a non-electric furnace and a non-blast furnace, with zero oxygen injection. The interior of the zero oxygen injection furnace is divided into a furnace body and a hearth along its vertical centerline from top to bottom. The zero oxygen injection furnace is used for the reduction melting of direct reduced iron to obtain liquid slag and molten iron.

[0046] Furthermore, the interior of the furnace body is vertically divided into a solid material layer and a soft melt dripping zone from top to bottom; the interior of the furnace hearth is vertically divided into a gas swirling zone, a slag layer, and a molten iron layer from top to bottom.

[0047] Furthermore, the furnace hearth is located at the same horizontal cross section of the gas swirl zone, with several reducing gas injection ports symmetrically distributed around the circumference; the furnace hearth is located at the same horizontal cross section of the liquid slag layer, with several slag outlets symmetrically distributed around the circumference; and the furnace hearth is located at the same horizontal cross section of the liquid iron layer, with several iron outlets symmetrically distributed around the circumference.

[0048] Furthermore, the diameter of the zero-oxygen injection furnace cylinder adopts an adjustable loop design, and the diameter of the zero-oxygen injection furnace cylinder and the injection superheated reducing gas flow rate are controlled as follows:

[0049] When the furnace hearth diameter d < 10m, the velocity of the superheated reducing gas flow is 150-350m / s.

[0050] When the furnace hearth diameter d > 10m, the velocity of the superheated reducing gas is 250-450m / s.

[0051] Furthermore, the ratio of the inner diameter of the lower horizontal section of the reduction section of the gas-based vertical shaft furnace to the diameter of the hearth of the zero-oxygen injection furnace is 1.0 to 1.3; the material layer height in the reduction section of the gas-based vertical shaft furnace is 5 to 8 meters; the ratio of the hearth height to the hearth diameter of the zero-oxygen injection furnace is 0.35 to 0.6; and the ratio of the furnace body height to the hearth diameter of the zero-oxygen injection furnace is 0.8 to 1.3.

[0052] The beneficial effects of this invention are:

[0053] (1) The present invention uses self-melting oxidized pellets thermally charged into a gas-based vertical shaft furnace, so that all the ore in the furnace is in the high-temperature zone, that is, the reaction zone is expanded and the metallization rate is increased, so as to reduce the gas heating temperature and / or reduce the flow rate of the heated gas, thereby reducing energy consumption.

[0054] (2) This process uses cold reducing gas, which enters the reduction section of the vertical shaft furnace after exchanging heat with the hot DRI to participate in the pre-reduction reaction of self-melting oxide pellets. The beneficial effects of this design are reflected in two aspects: on the one hand, it reduces the total gas flow of reducing gas and cooling gas in the gas-based vertical shaft furnace, thereby reducing the power cost of gas transportation; on the other hand, the cold reducing gas acts as a carrier to transfer the physical heat of the hot DRI to the reduction section of the gas-based vertical shaft furnace, and the physical heat of the DRI is recovered and utilized, further reducing the system energy consumption.

[0055] (3) This invention is not limited by the gas source and has low requirements for the H2:CO content of the reducing gas, and can be applied to reducing gas with any H2:CO content. There is an existing gas-based vertical shaft furnace process. Due to the hot gas and cold ore, and the mass and heat transfer mode of cold top and hot bottom, when the pellets descend to the middle and lower part of the reduction section in the gas-based vertical shaft furnace, the metallization rate rises to more than 80%. In order to prevent the pellets from sticking together at high temperature and high metallization rate, which would prevent the vertical shaft furnace from feeding smoothly, it is necessary to control the H2:CO content of the reducing gas to be greater than 1.2. The gas-based vertical shaft furnace of this invention uses hot ore with warm gas in the middle and hot gas at the top and cold gas at the bottom. When the self-melting oxidized pellets descend to the lower part of the reduction section and the metallization rate rises to more than 80%, the pellet temperature has already dropped to below 800°C. Moreover, the temperature of the mixed gas formed by the cold reducing gas and the hot reducing gas is much lower than that of the existing gas-based vertical shaft furnace process. It is only necessary to control the flow rate and temperature of the hot reducing gas according to the parameters in the claims. The test results show that even under the condition that the H2:CO ratio of the reducing gas approaches 0, it can still effectively prevent pellet sticking and the resulting production problems in the vertical shaft furnace.

[0056] (4) This process uses a zero-oxygen injection furnace instead of an electric furnace to achieve deep reduction and slag-iron molten separation in DRI. Its beneficial effects are as follows:

[0057] Compared with gas-based vertical shaft furnace-electric furnace deep reduction melting, its advantages are as follows: ① Lower cost of electrodes and other consumables. Zero-oxygen injection furnaces are non-electric furnaces and do not require electrode insertion, avoiding the costs associated with electrode consumption during production. ② Higher thermal efficiency. Zero-oxygen injection furnaces use superheated reducing gas as a carrier, introducing heat into the furnace from the reducing gas injection port in the hearth. The injection port is located below the solid material layer and the soft melt dripping zone, meaning the heat source is below and the heated material is above. Electric furnaces, on the other hand, insert electrodes from above, resulting in top heating. Therefore, zero-oxygen injection furnaces have higher thermal efficiency. ③ Zero-oxygen injection furnaces are suitable for smelting high, medium, and low-grade ores. Electric furnaces typically have no or only a small amount of gas injection, resulting in extremely uneven heat transfer within the furnace. This is particularly problematic when smelting low-grade ores, where the large amount of slag and its low thermal conductivity lead to slow and uneven heat transfer in the molten pool, ultimately resulting in high power consumption and low output. Therefore, the current gas-based vertical shaft furnace-electric furnace smelting process is unsuitable for smelting medium- and low-grade iron ore. Zero-oxygen injection furnaces typically inject 900–1500 Nm³ of superheated reducing gas. 3 / ton of ferrite, the larger the furnace hearth diameter, the higher the gas flow rate. Even when smelting low-grade ores, the powerful airflow agitation enables rapid and complete reaction of slag and iron, which then drips into the hearth and separates. ④ Zero-oxygen injection furnaces have high metal recovery rates. The reduction process of DRI in a zero-oxygen injection furnace mainly occurs in the solid material layer, the soft melt dripping zone, and the swirling zone, while the slag-iron separation process occurs in the slag layer and the molten iron layer. The injection nozzle is located in the swirling zone, and the upward movement of the injected reducing gas, under the "stirring" effect of the reducing gas, promotes rapid and complete reduction reaction in the upper part. The injected reducing gas does not pass through the slag-iron layer, keeping the molten slag and iron in a relatively "static" state, which is more conducive to slag-iron stratification and separation. Therefore, it is more conducive to improving the metal recovery rate. ⑤ Zero-oxygen injection furnaces are suitable for smelting special ores. When smelting difficult-to-process and separate ores, such as vanadium-titanium magnetite, the zero-oxygen injection furnace has good kinetic conditions, which can achieve rapid DRI reduction and rapid separation and discharge of slag and iron, avoiding the generation of foamy slag. Conversely, in the gas-based vertical shaft furnace-electric furnace smelting process for vanadium-titanium ore, rapid separation and discharge of slag and iron cannot be achieved within the electric furnace, resulting in foamy slag and inability to properly discharge slag and tap iron. ⑥ Zero-oxygen injection furnaces employ continuous charging and continuous slag and iron discharging operations, and the furnace volume can be expanded to 5000m³. 3 With a capacity of 3.5 million tons or more per year, a single unit of equipment can achieve an annual output of over 3.5 million tons of molten iron, making it more valuable for widespread application.

[0058] Compared to blast furnaces, its advantages include: ① Significantly reduced carbon emissions. The O2 injection rate at the tuyeres of traditional blast furnaces is 350-370 Nm³. 3 / ton of molten iron, the O2 blown in burns with solid carbon at the tuyeres, generating high-temperature CO. The higher the O2 blown in, the higher the carbon consumption and emissions. Zero-oxygen injection furnaces are non-blast furnaces; the oxygen blown in is zero. Zero-oxygen injection furnaces recover and utilize CO from the furnace top, resulting in zero actual CO2 emissions. ② The furnace temperature in a zero-oxygen injection furnace is controlled by the temperature of the superheated reducing gas at the injection port, located in the hearth. Hearth heat can be quickly and flexibly adjusted. In contrast, the hearth heat of a blast furnace is determined by the amount of solid carbon burned per ton of charge. Adjusting hearth heat requires adjusting the amount of coke charged at the furnace top or the amount of pulverized coal blown in through the tuyeres. The adjustment results lag by approximately 2-5 hours, and the adjustment process is affected by slag and iron discharge, easily leading to uncontrolled hearth temperature. ③ This is beneficial for the smelting of special minerals such as vanadium-titanium magnetite. The nitrogen content in the injected gas of the zero-oxygen injection furnace is less than 8% (compared to 79% in a conventional blast furnace), and the consumption of solid carbon materials is less than 0.1 kg / t of molten iron (compared to 0.55 kg / t in a blast furnace). 铁水 The zero-oxygen injection furnace can effectively suppress the formation of Ti(C,N) during the smelting of vanadium-titanium ore. Due to the rapid and flexible adjustment of the furnace hearth temperature, the zero-oxygen injection furnace can reduce the frequency of low furnace temperatures, which is beneficial to the recovery of vanadium.

[0059] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 A schematic diagram of a zero-oxygen injection low-carbon ironmaking device according to an embodiment of the present invention is shown.

[0062] In the picture:

[0063] 10. Gas-based vertical shaft furnace; 11. Reduction section; 12. Cooling section; 13. Vertical shaft furnace charging assembly; 14. Cold reducing gas inlet; 15. Discharge port; 16. Hot reducing gas inlet; 17. Vertical shaft furnace gas outlet pipe; 18. First gravity dust collector; 20. Zero oxygen injection furnace; 21. Solid material layer; 22. Softening dripping zone; 23. Gas swirling zone; 24. Slag layer; 25. Molten iron layer; 26. Zero 27. Oxygen injection furnace charging assembly; 28. Slag outlet; 29. ​​Iron outlet; 20. Zero oxygen injection furnace gas outlet pipe; 210. Zero oxygen injection furnace reducing gas injection port; 211. Second gravity dust collector; 30. Reducing gas holder; 31. First compressor; 32. First heat exchanger; 40. First heating furnace; 50. Second compressor; 51. Second heat exchanger; 60. Second heating furnace; 70. Gas purification system. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] like Figure 1 As shown, a zero-oxygen injection low-carbon ironmaking device according to an embodiment of the present invention includes a gas-based vertical shaft furnace 10 and a zero-oxygen injection furnace 20.

[0066] The gas-based vertical furnace 10 is divided into a reduction section 11 and a cooling section 12 from top to bottom along the internal vertical direction.

[0067] Several hot reducing gas injection inlets 16 are symmetrically arranged on the same horizontal cross section at the junction of the reduction section 11 and the cooling section 12. The reduction section 11 is used for the pre-reduction reaction of self-fluxing oxidized pellets to obtain hot direct reduced iron.

[0068] Several cold reducing gas injection inlets 14 are symmetrically arranged on the same horizontal cross section at the lower part of the cooling section 12. The cooling section 12 is used to cool hot direct reduced iron to cold direct reduced iron. In this embodiment of the invention, the height of the cold reducing gas injection inlet 14 from the bottom of the cooling section 12 is 0.5-2.5 meters.

[0069] The cold direct reduced iron discharged from the bottom of the cooling section 12 is transported to the zero oxygen injection furnace 20. The zero oxygen injection furnace 20 is a non-electric furnace, does not require the insertion of electrodes, and is not a blast furnace. The oxygen injection rate is zero. The zero oxygen injection furnace 20 is divided into a furnace body and a hearth in the vertical direction from top to bottom. The zero oxygen injection furnace 20 is used for the reduction melting of direct reduced iron to obtain liquid slag and molten iron.

[0070] In this embodiment of the invention, the cooling section 12 adopts an inverted frustum design, with the lower cross-sectional diameter being smaller than the upper cross-sectional diameter.

[0071] In this embodiment of the invention, a discharge port 15 is provided at the bottom of the cooling section 12, and the cold direct reduced iron is discharged from the discharge port 15. The discharge port 15 is located below the cold reducing gas injection port 14.

[0072] In this embodiment of the invention, for the convenience of charging, the top of the gas-based vertical furnace 10 is provided with a vertical furnace charging assembly 13, and the top of the zero-oxygen injection furnace 20 is provided with a zero-oxygen injection furnace charging assembly 26. The vertical furnace charging assembly 13 and the zero-oxygen injection furnace charging assembly 26 are equipment well known to those skilled in the art, and will not be described in detail here.

[0073] In this embodiment of the invention, in order to facilitate the discharge of vertical furnace gas and oxygen-free injection furnace gas, the top of the gas-based vertical furnace 10 is provided with a vertical furnace gas outlet pipe 17, and the top of the oxygen-free injection furnace 20 is provided with an oxygen-free injection furnace gas outlet pipe 29.

[0074] In this embodiment of the invention, the interior of the furnace body is divided vertically from top to bottom into a solid material layer 21 and a soft melt dripping zone 22; the interior of the furnace hearth is divided vertically from top to bottom into a gas swirling zone 23, a slag layer 24 and a molten iron layer 25.

[0075] The hearth is located at the same horizontal cross section at the top of the gas swirl zone 23, with several zero-oxygen injection furnace reducing gas injection ports 210 symmetrically distributed around the circumference; the hearth is located at the same horizontal cross section of the liquid slag layer 24, with several slag outlets 27 symmetrically distributed around the circumference; the hearth is located at the same horizontal cross section of the liquid iron layer 25, with several iron outlets 28 symmetrically distributed around the circumference.

[0076] For example, in this embodiment of the invention, the longitudinal section of the furnace hearth is rectangular.

[0077] In this embodiment of the invention, the diameter of the reducing gas injection port 210 of the zero oxygen injection furnace adopts an adjustable loop design to control the superheated reducing gas flow rate injected from the reducing gas injection port 210 of the zero oxygen injection furnace.

[0078] The diameter of the furnace cylinder of the zero-oxygen injection furnace 20 and the velocity of the injected superheated reducing gas flow are controlled as follows:

[0079] When the furnace hearth diameter d < 10m, the velocity of the superheated reducing gas flow is 150-350m / s.

[0080] When the furnace hearth diameter d > 10m, the velocity of the superheated reducing gas is 250-450m / s.

[0081] The reaction process of direct reduced iron (DRI) within the zero-oxygen injection furnace 20 (DRI undergoes deep reduction, melting, and slag-iron separation within the zero-oxygen injection furnace 20) is as follows:

[0082] Inside the zero-oxygen injection furnace 20, DRI and solid carbon materials are added from the top charging equipment of the zero-oxygen injection furnace 20 and distributed on the surface of the solid material layer 21; ultra-high temperature (1800~2350℃) reducing gas (i.e., superheated reducing gas) is injected from the reducing gas injection port 210 of the zero-oxygen injection furnace at a high velocity (flow rate 900~1500Nm) under high pressure. 3 / ton of ferrite) is injected into the gas swirling zone 23 of the hearth, that is, the superheated reducing gas injected into the reducing gas injection port 210 of the zero oxygen injection furnace does not directly enter the liquid iron layer 25 and the slag layer 24.

[0083] At the front end of the reducing gas injection port 210 of the zero oxygen injection furnace, when the high-pressure, high-velocity superheated reducing gas is blown into the hearth, it blows away the material at the front end of the reducing gas injection port 210, forming a high-temperature space with gas as the main material, which is the gas swirling zone 23. The gas swirling zone 23 is located between the liquid slag layer 24 and the soft melting dripping zone 22. The airflow generated by the gas swirling zone 23 agitates the material passing through the horizontal cross section of the gas swirling zone 23, so that the material and temperature in the hearth are evenly distributed and the physicochemical reaction in the hearth is more complete.

[0084] After passing through the gas swirl zone 23, the superheated reducing gas enters the softening and dripping zone 22. In the softening and dripping zone 22, the superheated reducing gas undergoes intense heat exchange with the DRI and solid carbon material, causing the DRI temperature to rise, soften, and melt into a liquid slag-iron mixture. Under the action of gravity, the liquid slag-iron mixture begins to drip, passing through the gas swirl zone 23 and entering the molten pool in the hearth. In the molten pool, the slag and molten iron are automatically separated into layers due to their different densities. The molten iron sinks to the bottom to form a liquid molten iron layer 25, while the slag floats above the molten iron to form a liquid slag layer 24.

[0085] Liquid slag and iron in the hearth are discharged from the furnace through slag outlet 27 and iron outlet 28, respectively. For ore with a small amount of slag, the slag outlet can be eliminated and the slag can be discharged through iron outlet 28.

[0086] Liquid slag and iron are discharged from the hearth to make room in the furnace, so that the slag and iron in the softening dripping zone 22 can continuously drip into the hearth. The solid material layer 21 moves down and enters the softening dripping zone 22 in sequence. The zero oxygen injection furnace charging assembly 26 continuously loads new furnace material onto the surface of the solid material layer 21, and the thickness of the solid material layer 21 remains unchanged.

[0087] The superheated reducing gas exchanges heat with DRI and solid carbon material in the softening and dripping zone 22, and then enters the solid material layer 21. In the solid material layer 21, DRI and solid carbon material are preheated, and the gas reacts with the iron oxides in DRI that are not completely reduced, with FeO+CO=Fe+CO2 and / or FeO+H2=Fe+H2O. The gaseous products are output from the zero oxygen injection furnace gas outlet pipe 29 at the top of the zero oxygen injection furnace 20.

[0088] The carbon in the solid carbon material has a melting point of over 4000℃. During the above smelting process, the solid carbon material is continuously heated as the furnace charge descends until it enters the softening dripping zone 22, the gas swirling zone 23, the slag layer 24 and the molten iron layer 25. It remains solid and is called a solid material column.

[0089] Influenced by the high-velocity reducing gas in the gas swirling zone 23, the solid material column is mainly distributed in the center of the hearth on the horizontal cross section of the gas swirling zone 23, and gradually diffuses to other areas of the hearth after entering the molten slag and iron.

[0090] In the molten iron layer 25, some of the carbon in the solid material column dissolves into the molten iron, and a carburizing reaction occurs.

[0091] In the slag layer 24 and the softening dripping zone 22, some of the carbon in the solid column undergoes a direct reduction reaction with the incompletely reduced iron oxides: FeO + C = Fe + CO. The gaseous product CO rises and is output through the zero-oxygen injection furnace gas outlet pipe 29 at the top of the furnace.

[0092] The carburizing and direct reduction of molten iron continuously "dissolve" the solid charge column, while the upper and lower furnace charge continuously provides new solid charge columns, making the solid charge column permanent and constantly replaced.

[0093] The high-pressure airflow in the solid material column and gas swirl zone 23 provides support for the solid material layer 21 in the furnace body.

[0094] The gas produced by the chemical reaction inside the zero-oxygen injection furnace 20, and the gas injected into the furnace that has not undergone a chemical reaction, are collectively referred to as zero-oxygen injection furnace gas. The zero-oxygen injection furnace gas is output from the top of the furnace through the zero-oxygen injection furnace gas outlet pipe 29.

[0095] In some embodiments of the present invention, in order to improve the coordination of pre-reduction and deep reduction in the gas-based vertical shaft furnace 10 and the oxygen-free injection furnace 20, as well as the reduction efficiency of the overall ironmaking unit, and because the inner diameter of the horizontal cross-section of the hearth of the oxygen-free injection furnace 20 (hereinafter referred to as the hearth diameter of the oxygen-free injection furnace 20) is an important parameter determining the system's molten iron production capacity; in order to ensure that the production capacity of the ore pre-reduction system matches the slag-iron smelting production capacity, the ratio of the inner diameter of the lower horizontal cross-section of the reduction section 11 of the gas-based vertical shaft furnace 10 to the hearth diameter of the oxygen-free injection furnace 20 is 1.0 to 1.3; the material layer height in the reduction section 11 of the gas-based vertical shaft furnace 10 is 5 to 8 meters; the ratio of the hearth height of the oxygen-free injection furnace 20 to the hearth diameter of the oxygen-free injection furnace 20 is 0.35 to 0.6, and the ratio of the furnace body height of the oxygen-free injection furnace 20 to the hearth diameter of the oxygen-free injection furnace 20 is 0.8 to 1.3.

[0096] In some embodiments of the present invention, in order to save energy consumption of the ironmaking device, the zero-oxygen injection low-carbon ironmaking device further includes a gas and heat recovery system;

[0097] The gas and heat recovery system includes a vertical shaft furnace gas and heat recovery subsystem and a zero-oxygen injection furnace gas and heat recovery subsystem;

[0098] The vertical shaft furnace gas and heat recovery subsystem and the zero oxygen injection furnace gas and heat recovery subsystem can be set up independently, or they can be partially or completely shared.

[0099] The gas output from the top of the vertical shaft furnace has a temperature of 700-900℃. After coarse dust removal by a gravity dust collector to remove large dust particles, it enters the heat exchange system, where it transfers heat to the heated medium before being output from the heat exchange system. The next step is to enter the gas purification system 70, where fine dust particles, CO2, and H2O are further removed. This is called purified gas. The combined volume percentage of CO2 and H2O in the purified gas is less than 1.5%. The purified gas is then sent to a reducing gas holder for recycling.

[0100] The gas output from the top of the zero-oxygen injection furnace 20 has a temperature of 500-700℃. After coarse dust removal by a gravity dust collector to remove large dust particles, it enters the heat exchange system, where heat is transferred to the heated medium before being output from the heat exchange system. The next step is to enter the gas purification system 70, where fine dust particles are first removed, and then CO2 and H2O are selectively removed based on the gas composition, or it is output directly. The zero-oxygen injection furnace gas output by the gas purification system 70 is called purified gas. The combined volume percentage of CO2 and H2O in the purified gas is less than 1.5%. The purified gas is sent to the reducing gas holder for recycling.

[0101] In this embodiment of the invention, the vertical furnace gas and heat recovery subsystem includes a first gravity dust collector 18 and a reducing gas holder 30. The first gravity dust collector 18 is connected to the vertical furnace gas outlet pipe 17 to remove dust and other impurities from the vertical furnace gas.

[0102] The reducing gas holder 30 is connected to a first pressurizer 31, and the first pressurizer 31 is connected to a first heating furnace 40 through a first heat exchanger 32.

[0103] The first gravity dust collector 18 is connected to the port of the reducing gas holder 30 through the first heat exchanger 32. This port is different from the connection port of the reducing gas holder 30 and the first gravity dust collector 18.

[0104] After the vertical furnace gas (high temperature) is discharged from the vertical furnace gas outlet pipe 17, it passes through the first gravity dust collector 18 and then exchanges heat with the reducing gas pressurized by the first compressor 31 in the first heat exchanger 32 to obtain vertical furnace purified gas, which is then returned to the reducing gas holder 30.

[0105] To further remove dust, carbon dioxide, and water vapor from the vertical shaft furnace gas, the first gravity dust collector 18 is connected to the reducing gas holder 30 via the first heat exchanger 32 and the gas purification system 70 (which performs fine dust removal, CO2 removal, and H2O removal). That is, after the vertical shaft furnace gas undergoes dust removal, heat exchange, and purification (fine dust removal, CO2 removal, and H2O removal), purified vertical shaft furnace gas is obtained and returned to the reducing gas holder 30. The gas purification system 70 is a device well known to those skilled in the art, and will not be described in detail here.

[0106] Meanwhile, the reducing gas in the reducing gas holder 30 is preheated by the heat exchange of the vertical furnace gas (high temperature) and used as the gas source of the hot reducing gas. Then it is heated by the first heating furnace 40 (connected to the hot reducing gas injection inlet 16) and then enters the gas-based vertical furnace 10 from the hot reducing gas injection inlet 16.

[0107] The above subsystem fully recovers and utilizes the thermal and chemical energy of the vertical furnace gas on the one hand, and purifies the vertical furnace gas on the other hand, and recycles it as reducing gas, thus realizing the dual recovery and utilization of gas and heat.

[0108] The zero-oxygen injection furnace gas and heat recovery subsystem includes a second gravity dust collector 211 and a reducing gas holder 30. The second gravity dust collector 211 is connected to the zero-oxygen injection furnace gas outlet pipe 29 to remove dust and other impurities from the zero-oxygen injection furnace gas.

[0109] The reducing gas holder 30 is connected to a second compressor 50 (the connection port is different from the connection port between the reducing gas holder 30 and the first compressor 31), and the second compressor 50 is connected to a second heating furnace 60 through a second heat exchanger 51.

[0110] The second gravity dust collector 211 is connected to the reducing gas holder 30 through the second heat exchanger 51;

[0111] After the zero-oxygen injection furnace gas (high temperature) is discharged from the zero-oxygen injection furnace gas outlet pipe 29, it passes through the second gravity dust collector 211 and then exchanges heat with the reducing gas pressurized by the second compressor 50 in the reducing gas holder 30 in the second heat exchanger 51 to obtain zero-oxygen injection furnace purified gas, which is then returned to the reducing gas holder 30.

[0112] To further remove dust from the zero-oxygen injection furnace gas, the second gravity dust collector 211 is connected to the reducing gas holder 30 through the second heat exchanger 51 and the gas purification system 70 (whose main function is fine dust removal). That is, after the zero-oxygen injection furnace gas undergoes dust removal, heat exchange, and purification (fine dust removal), it becomes zero-oxygen injection furnace purified gas, which is returned to the reducing gas holder 30. The reducing gas holder 30 is a device well known to those skilled in the art, and will not be described in detail here.

[0113] Meanwhile, the reducing gas in the reducing gas holder 30 is preheated by the gas (high temperature) of the zero-oxygen injection furnace and used as the source of the hot reducing gas. Then it is heated by the second heating furnace 60 (connected to the reducing gas injection port 210 of the zero-oxygen injection furnace) and then enters the zero-oxygen injection furnace 20 from the reducing gas injection port 210 of the zero-oxygen injection furnace.

[0114] To illustrate the implementation effect of the zero-oxygen injection low-carbon ironmaking method and apparatus provided in the embodiments of the present invention, three types of typical domestic iron ore of the grades listed in Table 1 were used and implemented under different atmospheres. The components in Table 1 are all mass ratios, unit: %.

[0115] Table 1

[0116]

[0117] Example 1

[0118] A zero-oxygen injection low-carbon ironmaking method for smelting high-grade iron ore in China:

[0119] 1.1 The ore is blended according to the composition of iron ore, flux and bentonite. The composition of each material is shown in Table 2 (mass ratio, unit: %).

[0120] Table 2

[0121]

[0122] With bentonite at a ratio of 1.5%, and a CaO to SiO2 mass ratio of 1.2 in the pellets, the mass proportions of each material were calculated as follows:

[0123] Iron ore: flux: bentonite = 96.4%: 2.1%: 1.5%.

[0124] The composition of the self-fluxing oxide pellets produced according to the above proportions is detailed in Table 3 (mass ratio, unit: %).

[0125] Table 3

[0126] Pellet Ore 67.48 85.91 9.45 1.68 0.02 0.60 2.02 0.14 0.19 100

[0127] 1.2 Production is organized based on the composition of economically reducing gas in the gas-based vertical shaft furnace 10 and the zero-oxygen injection furnace 20.

[0128] In a certain region, H2 resources are relatively abundant, or the cost of obtaining H2 is lower than the cost of CO. In this case, when the reducing gas is mainly composed of H2, the production cost of the gas-based vertical shaft furnace 10 is lower. Therefore, a production method with a higher H2:CO ratio can be selected, taking H2:CO = 5 (volume ratio, the same below) as an example.

[0129] The composition of the reducing gas is detailed in Table 4 (volume ratio, unit: %).

[0130] Table 4

[0131] 79.2 15.8 5.0 100

[0132] The pellet charging temperature is 1000℃, and the total reducing gas flow rate in the gas-based vertical shaft furnace 10 is 2000 Nm³. 3 For 1 ton of ferrite, choose K (cold reducing gas flow rate: hot reducing gas flow rate) = 1.62, and cold reducing gas flow rate = 1237 Nm. 3 / ton of ferrite, cold reducing gas temperature = 25℃, hot reducing gas flow rate = 763Nm 3 / ton of ferrite, hot reducing gas temperature = 1000℃. Based on ore grade, the total reducing gas flow rate of a 10-ton gas-based vertical shaft furnace is calculated to be 1832 Nm³. 3 / ton DRI, of which, cold reducing gas flow rate = 1133 Nm3 / ton DRI, heat reducing gas flow rate = 699Nm 3 / ton DRI.

[0133] Output flow rate from the reducing gas holder = 699 Nm 3 The reducing gas of / ton DRI is blown into the first gas heat exchanger 32 through the first compressor 31. The reducing gas is preheated to 300°C and then blown into the first heating furnace 40 to be heated to 1000°C, becoming hot reducing gas, which is then injected from the hot reducing gas injection port 16.

[0134] The DRI discharged from the bottom of the gas-based vertical shaft furnace 10 has a temperature of 250°C and its composition is shown in Table 5 (mass ratio, unit %).

[0135] Table 5

[0136] 91.6 84.3 9.4 2.3 0.0 0.8 2.7 0.2 0.3 100

[0137] Cold reducing gas is injected into the cooling section 12 from the cold reducing gas inlet 14 of the gas-based vertical shaft furnace 10. Upon reaching the reduction section 11, its temperature is 514℃. After mixing with the hot reducing gas injected from the hot reducing gas inlet 16, the resulting mixed reducing gas has a temperature of 700℃. This mixed reducing gas reacts with iron oxides in the pellets in the reduction section 11 to produce metallic iron and vertical shaft furnace gas. The composition of the vertical shaft furnace gas is shown in Table 6 (volume ratio, unit: %). The vertical shaft furnace gas is discharged from the vertical shaft furnace gas outlet pipe 17, with a flow rate of 1832 Nm³. 3 / tDRI, vertical shaft furnace gas temperature = 750℃. After passing through the first heat exchanger 32, the temperature of the vertical shaft furnace gas decreases. Further fine dust removal and CO2 and H2O removal occur, resulting in clean vertical shaft furnace gas. The amount of CO2 removed is 189 kg / ton of ferrite. The composition of the clean vertical shaft furnace gas is shown in Table 7 (volume ratio, unit: %). The volume of clean vertical shaft furnace gas is 1332 Nm³. 3 / tDRI=1454m 3 / ton of ferrite.

[0138] Table 6

[0139] 56.7％ 11.0％ 22.5％ 4.8％ 5.0％

[0140] Table 7

[0141] 78.0％ 15.2％ 6.9％

[0142] The solid carbon feed uses coke with a fixed carbon content of 85% by mass. The coke and direct reduced iron (DRI) produced in the shaft furnace are added from the top charging assembly 26 of the zero-oxygen injection furnace 20 at a mass ratio of 0.064:1. The feed is then pumped through a second press 50 at a flow rate of 1000 Nm³. 3The reducing gas of / ton of ferrite is blown into the second heat exchanger 51, where it is preheated to 300°C. Then it enters the second heating furnace 60 and is further heated to 2250°C to become superheated reducing gas. The superheated reducing gas is blown into the zero oxygen injection furnace reducing gas injection port 210 of the zero oxygen injection furnace 20.

[0143] Inside the oxygen-free injection furnace 20, superheated reducing gas undergoes intense heat exchange with the solid direct reduced iron (DRI) inside the furnace, generating a liquid mixed slag-iron mixture at 1400-1600℃. The temperature of the superheated reducing gas decreases from 2250℃ to 1800-2000℃. As the superheated reducing gas moves upward, it continues to preheat the DRI in the furnace body, finally reducing its temperature to around 600℃ before exiting through the oxygen-free injection furnace gas outlet pipe 29 at the top of the furnace. The high-temperature liquid mixed slag-iron mixture undergoes chemical reactions with the hot reducing gas and solid coke: FeO + H2 = H2O + Fe, H2O + C = H2 + CO, FeO + CO = CO2 + Fe, CO2 + C = 2CO, FeO + C = CO + Fe. The gaseous products inside the furnace are exited through the oxygen-free injection furnace gas outlet pipe 29 at the top of the furnace. The exited gas is the oxygen-free injection furnace gas, with a flow rate of 1032 Nm³. 3 The composition of gas in a zero-oxygen injection furnace per ton of molten iron is shown in Table 8 (volume ratio, unit: %).

[0144] Table 8

[0145] 76.71 18.44 4.84 100

[0146] Since the gas does not contain H2O and CO2, it only needs to be dusted to obtain oxygen-free purified gas from the injection furnace.

[0147] 1.3 Implementation Results

[0148] Based on market prices from January to August 2023, the production cost of the above process was 2,093 yuan / ton of molten iron, as detailed in Table 9. This cost is 717 yuan / ton lower than the traditional blast furnace molten iron cost of 2,810 yuan / ton, representing a cost reduction of 25.5%.

[0149] Table 9

[0150]

[0151]

[0152] The actual CO2 emissions from the above production process are 189 kg CO2 / ton of molten iron, which is 34% lower than the 287 kg CO2 / ton of molten iron emissions from the existing gas-based vertical shaft furnace process. Converting the energy and material consumption of the production process into CO2 emissions according to their respective carbon emission factors, the generalized CO2 emissions from the production process are 771.4 kg CO2 / ton of molten iron (see Table 10). This CO2 emission is 878.6 kg CO2 / ton of molten iron lower than the 1650 kg CO2 / ton of molten iron produced by the traditional blast furnace process for smelting high-grade ore, representing a reduction of 53.2%.

[0153] Table 10

[0154] Pellet production kgce 2.69 34.1 91.7 Coke production kgce 2.69 7.5 20.2 Reducing gas heating kgce 2.69 122.6 329.7 coke kg 3.26 69.6 226.6 electricity kwh 0.57 240.0 136.9 reducing gas <![CDATA[m 3 ]]> 0.31 3,000.0 933.0 Vertical shaft furnace purified gas <![CDATA[m 3 ]]> 0.30 -1,453.8 -432.8 Zero-oxygen injection furnace purified gas <![CDATA[m 3 ]]> 0.36 -1,032.0 -373.9 molten iron kg 0.16 -1,000.0 -160.0 total 771.4

[0155] Example 2:

[0156] A zero-oxygen injection low-carbon ironmaking method for smelting domestic medium-grade iron ore

[0157] 2.1 The ore was blended according to the composition of iron ore, flux, and bentonite. The composition of each material is shown in Table 11. All components in Table 11 are mass ratios, in units of %.

[0158] Table 11

[0159]

[0160] With bentonite at a ratio of 1.5%, and a CaO to SiO2 mass ratio of 1.2 in the pellets, the mass proportions of each material were calculated as follows:

[0161] Iron ore: flux: bentonite = 91.2%: 7.3%: 1.5%.

[0162] The composition of the self-fluxing oxide pellets produced according to the above proportions is shown in Table 12 (mass ratio, unit: %).

[0163] Table 12

[0164] 56.56 80.43 0.33 6.20 0.15 4.18 7.44 0.99 0.27 100

[0165] 2.2 Production of gas-based vertical shaft furnace 10 is organized according to the economic reducing gas composition.

[0166] In a certain region, due to resource and price factors, the reducing gas H2:CO ratio is more economical within a certain range. Therefore, production is organized in the most economical way. Taking H2:CO = 1.0 as an example, the reducing gas composition is detailed in Table 13 (volume ratio, unit: %).

[0167] Table 13

[0168] 47.5 47.5 5.0 100

[0169] The pellet charging temperature is 980℃, and the total reducing gas flow rate of the gas-based vertical shaft furnace is 2100 Nm³. 3 For 1 ton of ferrite, choose K (cold reducing gas flow rate: hot reducing gas flow rate) = 1.47, and cold reducing gas flow rate = 1249 Nm³. 3 / ton of ferrite, cold reducing gas temperature = 25℃, hot reducing gas flow rate = 851Nm 3 / ton of ferrite, hot reducing gas temperature = 980℃. Based on ore grade, the total reducing gas flow rate of a 10-ton gas-based vertical shaft furnace is calculated to be 1541 Nm³. 3 / tDRI, where cold reducing gas flow rate = 917 Nm 3 / tDRI, heat reducing gas flow rate = 624 Nm 3 / tDRI.

[0170] The output flow rate from the reducing gas holder is 624 Nm. 3 The reducing gas from / tDRI is blown into the first gas heat exchanger 32 through the first compressor 31. The reducing gas is preheated to 300°C and then blown into the first heating furnace 40, where it is heated to 980°C to become hot reducing gas, which is then injected from the hot reducing gas injection port 16.

[0171] The DRI temperature discharged from the bottom of the gas-based vertical shaft furnace 10 is 250°C, and the composition is shown in Table 14 (mass ratio, unit %).

[0172] Table 14

[0173] 73.4 67.5 7.5 8.0 0.2 5.4 9.7 1.3 0.4 100

[0174] Cold reducing gas is injected into the cooling section 12 from the cold reducing gas inlet 14 of the gas-based vertical shaft furnace 10. Upon reaching the reduction section 11, its temperature is 521℃. After mixing with the hot reducing gas injected from the hot reducing gas inlet 16, the resulting mixed reducing gas has a temperature of 700℃. In the reduction section 11, the mixed reducing gas reacts with iron oxides in the pellets to produce metallic iron and vertical shaft furnace gas. The composition of the vertical shaft furnace gas is shown in Table 15 (volume percentage, unit: %). The vertical shaft furnace gas is discharged from the vertical shaft furnace gas outlet pipe 17, with a flow rate of 1541 Nm³. 3 / tDRI, vertical shaft furnace gas temperature = 750℃. After passing through the first heat exchanger 32, the temperature of the vertical shaft furnace gas decreases. Further fine dust removal and CO2 and H2O removal occur, resulting in clean vertical shaft furnace gas. The amount of CO2 removed is 577 kg / ton of ferrite. The composition of the clean vertical shaft furnace gas is shown in Table 16 (volume percentage, unit: %). The volume of clean vertical shaft furnace gas is 1125 Nm³. 3 / tDRI=1533m 3 / ton of ferrite.

[0175] Table 15

[0176] 34.5％ 33.5％ 13.0％ 14.0％ 5.0％

[0177] Table 16

[0178] 47.2％ 45.9％ 6.8％

[0179] The solid carbon feed uses coke with a fixed carbon content of 85% by mass. The coke and direct reduced iron (DRI) produced in the vertical shaft furnace are added from the top charging assembly 26 of the zero-oxygen injection furnace 20 at a mass ratio of 0.051:1. The feed is then pumped through a second pressurizer 50 at a flow rate of 1100 Nm³. 3 The reducing gas of / ton of ferrite is blown into the second heat exchanger 51, where it is preheated to 300°C. Then it enters the second heating furnace 60 and is further heated to 2200°C to become superheated reducing gas. The superheated reducing gas is blown into the zero oxygen injection furnace reducing gas injection port 210 of the zero oxygen injection furnace 20.

[0180] Inside the zero-oxygen injection furnace 20, superheated reducing gas undergoes intense heat exchange with the solid direct reduced iron (DRI) within the furnace, generating a liquid mixed slag-iron mixture at 1400-1600℃. The temperature of the superheated reducing gas decreases from 2200℃ to 1800-2000℃. As the superheated reducing gas moves upward, it continues to preheat the DRI in the furnace body, eventually reducing its temperature to around 600℃ before exiting through the zero-oxygen injection furnace gas outlet pipe 29 at the top of the furnace. The high-temperature liquid mixed slag-iron mixture undergoes chemical reactions with the superheated reducing gas and solid coke: FeO + H₂ = H₂O + Fe, H₂O + C = H₂ + CO, FeO + CO = CO₂ + Fe, CO₂ + C = 2CO, FeO + C = CO + Fe. The gases produced by these reactions, along with the superheated reducing gas that did not participate in the chemical reactions, are exited through the zero-oxygen injection furnace gas outlet pipe 29. The exited gas is the zero-oxygen injection furnace gas, with a flow rate of 1132 Nm³. 3 The composition of gas in a zero-oxygen injection furnace per ton of molten iron is shown in Table 17 (volume percentage, unit: %).

[0181] Table 17

[0182]

[0183]

[0184] Since the gas does not contain H2O and CO2, it only needs dust removal to obtain oxygen-free pulverized gas.

[0185] 2.3 Implementation Results

[0186] Based on market prices from January to August 2023, the production process cost was RMB 1,998 per ton of molten iron (see Table 18 for details). This cost is RMB 812 per ton lower than the traditional blast furnace molten iron cost of RMB 2,810 per ton, representing a cost reduction of 28.9%.

[0187] Table 18

[0188]

[0189] The actual CO2 emissions from the above production process are 577 kg CO2 / ton of molten iron. Converting the energy and material consumption of the production process into CO2 emissions based on their respective carbon emission factors, the generalized CO2 emissions from the production process are 1216.8 kg CO2 / ton of molten iron (see Table 19). This CO2 emission is 580.2 kg CO2 / ton of molten iron lower than the 1797 kg CO2 / ton of molten iron produced by traditional blast furnace smelting of medium-grade ore, representing a 32.3% reduction in CO2 emissions.

[0190] Table 19

[0191]

[0192]

[0193] Example 3:

[0194] A zero-oxygen injection low-carbon ironmaking method for smelting low-grade, difficult-to-process, and difficult-to-smelt iron ores in China.

[0195] Low-grade, difficult-to-process, and difficult-to-smelt iron ore is the most challenging and demanding iron ore resource for reducing carbon emissions in China. The CO2 emissions during the smelting process can reach as high as 2150 kg CO2 / ton of molten iron. Prior to this invention, no economically effective technical measures to reduce carbon emissions had been found.

[0196] 3.1 The ore is blended according to the composition of iron ore, flux, and bentonite. The composition of various materials is shown in Table 20. All components in Table 20 are mass ratios, in units of %.

[0197] Table 20

[0198]

[0199] With bentonite at a ratio of 1.5%, and a CaO to SiO2 mass ratio of 1.05 in the pellets, the mass proportions of each material were calculated as follows:

[0200] Iron ore: flux: bentonite = 93.0%: 5.5%: 1.5%.

[0201] The composition of the self-melting oxide pellets produced by mixing the ingredients according to the above ratio is shown in Table 21 (mass ratio, unit: %).

[0202] Table 21

[0203] 51.16 38.77 30.88 5.35 10.70 4.18 5.63 4.03 0.47 100

[0204] 3.2 Organize gas-based shaft furnace production based on economic reducing gas composition

[0205] 3.2.1 Low H2: CO smelting and its effects

[0206] (1) Using a gas-based vertical shaft furnace 10 and a zero-oxygen injection furnace 20 with H2:CO = 0.2, production is carried out.

[0207] In some regions, H2 resources are scarce, or the cost of obtaining H2 is higher than the cost of CO. In this case, production can be organized using a lower H2:CO ratio. Taking H2:CO = 0.2 as an example, the composition of the reducing gas is shown in Table 22 (volume ratio, unit: %).

[0208] Table 22

[0209] 15.8 79.2 5.0 100

[0210] The pellet charging temperature is 930℃, and the total reducing gas flow rate of the gas-based vertical shaft furnace is 2200 Nm³. 3 For 1 ton of ferrite, choose K (cold reducing gas flow rate: hot reducing gas flow rate) = 1.26, and cold reducing gas flow rate = 1227 Nm³. 3 / ton of ferrite, cold reducing gas temperature = 25℃, hot reducing gas flow rate = 973Nm 3 / ton of ferrite, hot reducing gas temperature = 930℃. Based on the ore grade, the total reducing gas flow rate of a 10-ton gas-based vertical shaft furnace is calculated to be 1361 Nm³. 3 / tDRI, where the cold reducing gas flow rate = 759 Nm 3 / tDRI, heat reducing gas flow rate = 602 Nm 3 / tDRI.

[0211] The output flow rate from the reducing gas holder is 602 Nm. 3 The reducing gas from / tDRI is blown into the first gas heat exchanger 32 through the first compressor 31. The reducing gas is preheated to 300°C and then blown into the first heating furnace 40, where it is heated to 930°C to become hot reducing gas. It is then injected into the hot reducing gas inlet 16.

[0212] The DRI temperature discharged from the bottom of the gas-based vertical shaft furnace 10 is 250℃, and the composition is shown in Table 23 (mass ratio, unit %).

[0213] Table 23

[0214] 61.9 56.9 6.4 6.5 12.9 5.1 6.8 4.9 0.6 100

[0215] Cold reducing gas is injected into the cooling section 12 from the cold reducing gas inlet 14 of the gas-based vertical shaft furnace 10. Upon reaching the reduction section 11, its temperature is 518℃. After mixing with the hot reducing gas injected from the hot reducing gas inlet 16, the resulting mixed reducing gas has a temperature of 700℃. This mixed reducing gas reacts with iron oxides in the pellets in the reduction section 11 to produce metallic iron and vertical shaft furnace gas. The composition of the vertical shaft furnace gas is shown in Table 24 (volume ratio, unit: %). The vertical shaft furnace gas is discharged from the vertical shaft furnace gas outlet pipe 17, with a flow rate of 1361 Nm³. 3 / tDRI, vertical shaft furnace gas temperature = 750℃. After passing through the first heat exchanger 32, the temperature of the vertical shaft furnace gas decreases. Further fine dust removal and CO2 and H2O removal occur, resulting in clean vertical shaft furnace gas. The amount of CO2 removed is 787 kg / ton of ferrite. The composition of the clean vertical shaft furnace gas is shown in Table 25 (volume percentage, unit: %). The volume of clean vertical shaft furnace gas is 1068 Nm³. 3 / tDRI=1726m 3 / ton of ferrite.

[0216] Table 24

[0217] 12.5％ 60.9％ 3.3％ 18.2％ 5.0％

[0218] Table 25

[0219] 15.9％ 77.7％ 6.4％

[0220] The solid carbon feed uses coke with a fixed carbon content of 85% by mass. The coke and direct reduced iron (DRI) produced in the vertical shaft furnace are added from the top charging assembly 26 of the zero-oxygen injection furnace 20 at a mass ratio of 0.043:1. The feed is then pumped through a second press 50 at a flow rate of 1200 Nm³. 3 The reducing gas of / ton of ferrite is blown into the second heat exchanger 51, where it is preheated to 300°C and then enters the second heating furnace 60, where it is further heated to 2150°C to become superheated reducing gas. The superheated reducing gas is blown into the reducing gas injection port 210 of the zero oxygen injection furnace.

[0221] Inside the oxygen-free injection furnace 20, superheated reducing gas undergoes intense heat exchange with the solid direct reduced iron (DRI) within the furnace, generating a liquid mixed slag-iron mixture at 1400-1600℃. The temperature of the superheated reducing gas decreases from 2150℃ to 1800-2000℃. As the superheated reducing gas moves upward, it continues to preheat the DRI in the furnace body, eventually reducing its temperature to around 600℃ before exiting through the oxygen-free injection furnace gas outlet pipe 29 at the top of the furnace. The high-temperature liquid mixed slag-iron mixture undergoes chemical reactions with the superheated reducing gas and solid coke: FeO + H₂ = H₂O + Fe, H₂O + C = H₂ + CO, FeO + CO = CO₂ + Fe, CO₂ + C = 2CO, FeO + C = CO + Fe. The gases produced by these reactions, along with the superheated reducing gas that did not participate in the chemical reactions, are exited through the oxygen-free injection furnace gas outlet pipe 29. The exited gas is the oxygen-free injection furnace gas, with a flow rate of 1232 Nm³. 3 The composition of gas from the zero-oxygen injection furnace for molten iron is shown in Table 26 (volume percentage, unit: %).

[0222] Table 26

[0223] 15.42 79.71 4.87 100

[0224] Since the gas does not contain H2O and CO2, it only needs dust removal to obtain oxygen-free pulverized gas.

[0225] (2) Implementation Results

[0226] Based on market prices from January to August 2023, the production cost of the above process was RMB 1,288 per ton of molten iron (see Table 27 for details). This cost is RMB 1,522 per ton lower than the traditional blast furnace molten iron cost of RMB 2,810 per ton, representing a cost reduction of 54.2%.

[0227] Table 27

[0228]

[0229]

[0230] The actual CO2 emissions from the above production process are 787 kg CO2 / ton of molten iron. Converting the energy and material consumption of the production process into CO2 emissions based on their respective carbon emission factors, the generalized CO2 emissions from the production process are 1477.7 kg CO2 / ton of molten iron (see Table 28). This CO2 emission is 672.3 kg CO2 / ton of molten iron lower than the 2150 kg CO2 / ton of molten iron produced by traditional blast furnace smelting of low-grade ore, representing a 31.3% reduction in CO2 emissions.

[0231] Table 28

[0232]

[0233] 3.2.2 High H2:CO smelting and its effects

[0234] (1) The gas is produced by a vertical shaft furnace 10 and a zero-oxygen injection furnace 20 with the effective component of reducing gas being all-hydrogen gas. The composition of the reducing gas is shown in Table 29 (volume ratio, unit: %).

[0235] Table 29

[0236] 95 0 5.0 100

[0237] The pellet charging temperature is 1050℃, and the total reducing gas flow rate of the gas-based vertical shaft furnace is 1800 Nm³. 3 For 1 ton of ferrite, choose K (cold reducing gas flow rate: hot reducing gas flow rate) = 2.02, and cold reducing gas flow rate = 1204 Nm. 3 / t ferrite, cold reducing gas temperature = 25℃, hot reducing gas flow rate = 596Nm 3 / ton of ferrite, hot reducing gas temperature = 1050℃. Based on ore grade, the total reducing gas flow rate of a 10-ton gas-based vertical shaft furnace is calculated to be 1114 Nm³. 3 / tDRI, where the cold reducing gas flow rate = 745 Nm 3 / tDRI, heat reduction gas flow rate = 369 Nm 3 / tDRI.

[0238] Output flow rate from the reducing gas holder = 369 Nm 3 The reducing gas from / tDRI is blown into the first heat exchanger 32 (a gas heat exchanger) through the first compressor 31. The reducing gas is preheated to 300°C and then blown into the first heating furnace 40, where it is heated to 1050°C to become hot reducing gas, which is then injected from the hot reducing gas injection port 16.

[0239] The DRI temperature discharged from the bottom of the gas-based vertical shaft furnace 10 is 250℃, and the composition is shown in Table 30 (mass ratio, unit %).

[0240] Table 30

[0241] 61.9 56.9 6.4 6.5 12.9 5.1 6.8 4.9 0.6 100

[0242] Cold reducing gas is injected into the cooling section 12 from the cold reducing gas inlet 14 of the gas-based vertical shaft furnace 10. Upon reaching the reduction section 11, its temperature is 527℃. After mixing with the hot reducing gas injected from the hot reducing gas inlet 16, the resulting mixed reducing gas has a temperature of 700℃. This mixed reducing gas reacts with iron oxides in the pellets in the reduction section 11 to produce metallic iron and vertical shaft furnace gas. The composition of the vertical shaft furnace gas is shown in Table 31 (volume ratio, unit: %). The vertical shaft furnace gas is discharged from the vertical shaft furnace gas outlet pipe 17, with a flow rate of 1114 Nm³. 3 / tDRI, vertical shaft furnace gas temperature = 750℃. After passing through the first heat exchanger 32, the temperature of the vertical shaft furnace gas decreases. Further fine dust removal and CO2 and H2O removal occur, resulting in clean vertical shaft furnace gas. The amount of CO2 removed is 0 kg / ton of ferrite. The composition of the clean vertical shaft furnace gas is shown in Table 32 (volume ratio, unit: %). The volume of clean vertical shaft furnace gas is 821 Nm³. 3 / tDRI=1326m 3 / ton of ferrite.

[0243] Table 31

[0244] 68.7％ 0.0％ 26.3％ 0.0％ 5.0％

[0245] Table 32

[0246] 93.2％ 0.0％ 6.8％

[0247] The solid carbon feed uses coke with a fixed carbon content of 85% by mass. The coke and direct reduced iron (DRI) produced in the vertical shaft furnace are added from the top charging assembly 26 of the zero-oxygen injection furnace 20 at a mass ratio of 0.043:1. Reducing gas with a flow rate of 1200 Nm³ / tHM is blown into the second heat exchanger 51 via the second pressurizer 50, where it is preheated to 300°C. Then, it enters the second heating furnace 60 and is further heated to 2150°C, becoming superheated reducing gas. This superheated reducing gas is blown into the reducing gas injection port 210 of the zero-oxygen injection furnace.

[0248] Inside the zero-oxygen injection furnace 20, superheated reducing gas undergoes intense heat exchange with the solid direct reduced iron (DRI) within the furnace, generating a liquid mixed slag-iron mixture at 1400-1600℃. The temperature of the superheated reducing gas decreases from 2150℃ to 1800-2000℃. As the superheated reducing gas moves upwards, it continues to preheat the DRI in the furnace body, finally reducing its temperature to around 600℃ before exiting through the zero-oxygen injection furnace gas outlet pipe 29. The high-temperature liquid mixed slag-iron mixture undergoes chemical reactions with the superheated reducing gas and solid coke: FeO + H₂ = H₂O + Fe, H₂O + C = H₂ + CO, FeO + CO = CO₂ + Fe, CO₂ + C = 2CO, FeO + C = CO + Fe. The gases produced by these reactions, along with the superheated reducing gas that did not participate in the chemical reactions, are exited through the zero-oxygen injection furnace gas outlet pipe 29. The exited gas is the zero-oxygen injection furnace gas, with a flow rate of 1232 Nm³. 3 The composition of the gas in the zero-oxygen injection furnace for molten iron is shown in Table 33 (volume ratio, unit: %).

[0249] Table 33

[0250] 92.53 2.60 4.87 100

[0251] Since the gas does not contain H2O and CO2, it only needs dust removal to obtain oxygen-free pulverized gas.

[0252] (2) Implementation Results

[0253] The iron recovery rate during the production process is 98.4%, which is 2.6% higher than the 95.8% of the blast furnace process and 29.7% higher than the 68.7% of the gas-based vertical shaft furnace-electric furnace smelting process; the V recovery rate is 71.2%, which is 1.9% higher than the 69.3% of the blast furnace process and 21.5% higher than the 47.8% of the gas-based vertical shaft furnace-electric furnace smelting process.

[0254] Based on market prices from January to August 2023, the production cost of the above process was RMB 1,260 per ton of molten iron (see Table 34 for details). This cost is RMB 1,550 per ton lower than the traditional blast furnace molten iron cost of RMB 2,810 per ton, representing a cost reduction of 55.2%.

[0255] Table 34

[0256]

[0257]

[0258] The actual CO2 emissions from the above production process are 0 kg CO2 / ton of molten iron. Converting the energy and material consumption of the production process into CO2 emissions according to their respective carbon emission factors, the generalized CO2 emissions from the above production process are 622.34 kg CO2 / ton of molten iron (see Table 35). This CO2 emission is 1527.7 kg CO2 / ton of molten iron lower than the 2150 kg CO2 / ton of molten iron produced by traditional blast furnace smelting of low-grade ore, representing a 71.1% reduction in CO2 emissions.

[0259] Table 35

[0260]

[0261] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A zero-oxygen injection low-carbon ironmaking method, characterized in that, include: Hot self-fluxing oxide pellets are loaded into the gas-based vertical shaft furnace (10) from the top of the furnace. Cold reducing gas is injected into the gas-based vertical shaft furnace (10) from the bottom of the furnace. At the same time, hot reducing gas is injected into the gas-based vertical shaft furnace (10) from the junction of the reduction section (11) and the cooling section (12) of the furnace. The cold reducing gas is heated during the ascent and mixed with the hot reducing gas. It then undergoes a pre-reduction reaction with the self-fluxing oxide pellets to obtain hot direct reduced iron. The hot direct reduced iron is cooled by the cold reducing gas in the cooling section (12) to obtain direct reduced iron. Solid carbon material and direct reduced iron are charged from the top of a zero-oxygen injection furnace (20) at a mass ratio of (0.03-0.1):1, with a temperature of 1800-2350℃ and a flow rate of 900-1500 Nm³. 3 / ton of superheated reducing gas is injected into the zero oxygen injection furnace (20) to directly reduce iron to undergo reduction melting, resulting in liquid slag and molten iron; The zero-oxygen injection furnace is a non-electric furnace and a non-blast furnace, with zero oxygen injection rate; The total gas flow rate in the gas-based vertical furnace (10) includes cold reducing gas flow rate and hot reducing gas flow rate, wherein the ratio of cold reducing gas flow rate to hot reducing gas flow rate is K; When the reducing gas H2:CO > 5 is injected into the gas-based vertical shaft furnace (10), the charging temperature of the self-melting oxidized pellets is 1050-1100℃, and the total flow rate of the reducing gas in the gas-based vertical shaft furnace (10) is 1800-1900 Nm³. 3 / t ferrite, K ranges from 1.7 to 2.1, and the temperature of the thermal reducing gas is 1050±20℃; When the reducing gas content in the gas-based vertical shaft furnace (10) is 1.5 < H2:CO ≤ 5, the charging temperature of the self-fluxing oxidized pellets is 1000-1050℃, and the total flow rate of the reducing gas in the gas-based vertical shaft furnace (10) is 1900-2000 Nm³. 3 / t ferrite, K ranges from 1.5 to 1.8, and the temperature of the thermal reducing gas is 1000-1050℃; When the reducing gas content injected into the gas-based vertical shaft furnace (10) is 0.6 < H2:CO ≤ 1.5, the charging temperature of the self-fluxing oxidized pellets is 950-1000℃, and the total flow rate of reducing gas in the gas-based vertical shaft furnace (10) is 2000-2100 Nm³. 3 / t ferrite, K ranges from 1.3 to 1.6, and the temperature of the thermal reducing gas is 980±20℃; When the reducing gas content injected into the gas-based vertical shaft furnace (10) is 0.2 < H2:CO ≤ 0.6, the charging temperature of the self-fluxing oxidized pellets is 900-950℃, and the total flow rate of the reducing gas in the gas-based vertical shaft furnace (10) is 2100-2200 Nm³. 3 / t ferrite, K ranges from 1.2 to 1.4, and the temperature of the thermal reducing gas is 950±20℃; When the reducing gas H2:CO ≤ 0.2 is injected into the gas-based vertical shaft furnace (10), the charging temperature of the self-melting oxidized pellets is 880-920℃, and the total flow rate of the reducing gas in the gas-based vertical shaft furnace (10) is 2200-2300 Nm³. 3 / t ferrite, K ranges from 1.1 to 1.3, and the temperature of the thermal reducing gas is 930±20℃.

2. The zero-oxygen injection low-carbon ironmaking method according to claim 1, characterized in that, The CaO:SiO2 mass ratio in the self-fluxing oxide pellets is 0.9-1.3, and the Fe element mass percentage in the self-fluxing oxide pellets is 50%-69%; the temperature of the cold reducing gas is less than 50℃; the temperature of the direct reduced iron obtained after the hot direct reduced iron is cooled by the cold reducing gas in the cooling section (12) is less than 250℃, and the metallization rate is ≥92%; the fixed carbon content in the solid carbon material is greater than 75%.

3. The zero-oxygen injection low-carbon ironmaking method according to claim 1, characterized in that, The hot reducing gas and the superheated reducing gas are reducing gas in a reducing gas holder, and the cold reducing gas is reducing gas in a reducing gas holder and / or coke oven gas. The reducing gas in the reducing gas holder includes purified coal gas and newly replenished reducing gas. The reducing gas in the reducing gas holder consists of CO, H2, N2 and impurity gases, and the sum of the volume percentages of CO and H2 is greater than 92%. The purified coal gas is the coal gas recovered after heat exchange and purification from the top coal gas of the gas-based vertical furnace (10) and the zero-oxygen injection furnace (20).

4. A zero-oxygen injection low-carbon ironmaking device, characterized in that, The zero-oxygen injection low-carbon ironmaking method according to any one of claims 1-3 includes a gas-based vertical shaft furnace (10) and a zero-oxygen injection furnace (20); The gas-based vertical furnace (10) is divided into a reduction section (11) and a cooling section (12) from top to bottom along the internal vertical direction; Several hot reducing gas injection inlets (16) are symmetrically arranged on the same horizontal cross section at the junction of the reduction section (11) and the cooling section (12). The reduction section (11) is used for the pre-reduction reaction of self-fluxing oxidized pellets to obtain hot direct reduced iron. Several cold reducing gas injection inlets (14) are symmetrically arranged on the same horizontal cross section inside the lower part of the cooling section (12). The cooling section (12) is used to cool the hot direct reduced iron to obtain cold direct reduced iron. The direct reduced iron discharged from the bottom of the cooling section (12) is transported to the zero oxygen injection furnace (20). The zero oxygen injection furnace (20) is a non-electric furnace and a non-blast furnace, with zero oxygen injection. The interior of the zero oxygen injection furnace (20) is divided into a furnace body and a furnace hearth from top to bottom along its vertical center line. The zero oxygen injection furnace (20) is used for the reduction melting of direct reduced iron to obtain liquid slag and molten iron.

5. The zero-oxygen injection low-carbon ironmaking device according to claim 4, characterized in that, The interior of the furnace body is divided vertically from top to bottom into a solid material layer (21) and a soft melt dripping zone (22); the interior of the furnace hearth is divided vertically from top to bottom into a gas swirling zone (23), a slag layer (24), and a molten iron layer (25).

6. The zero-oxygen injection low-carbon ironmaking device according to claim 5, characterized in that, The hearth is located on the same horizontal section of the gas swirling zone (23), with several reducing gas injection ports (210) symmetrically distributed around the circumference. The hearth is located on the same horizontal section of the slag layer (24), with several slag outlets (27) symmetrically distributed around the circumference. The hearth is located on the same horizontal section of the molten iron layer (25), with several iron outlets (28) symmetrically distributed around the circumference.

7. The zero-oxygen injection low-carbon ironmaking device according to claim 6, characterized in that, The diameter of the reducing gas injection port (210) adopts an adjustable loop design. The furnace cylinder diameter of the zero-oxygen injection furnace (20) and the injection superheated reducing gas flow rate are controlled as follows: When the furnace hearth diameter d < 10m, the velocity of the superheated reducing gas flow is 150-350m / s; When the furnace hearth diameter d > 10m, the velocity of the superheated reducing gas is 250-450m / s.

8. A zero-oxygen injection low-carbon ironmaking apparatus according to any one of claims 5-7, characterized in that, The ratio of the inner diameter of the lower horizontal section of the reduction section (11) of the gas-based vertical shaft furnace (10) to the diameter of the hearth of the zero-oxygen injection furnace (20) is 1.0-1.3; the material layer height in the reduction section (11) of the gas-based vertical shaft furnace (10) is 5-8 meters; the ratio of the height of the hearth of the zero-oxygen injection furnace (20) to the diameter of the hearth of the zero-oxygen injection furnace (20) is 0.35-0.6; and the ratio of the height of the furnace body of the zero-oxygen injection furnace (20) to the diameter of the hearth of the zero-oxygen injection furnace (20) is 0.8-1.3.

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