Self-heating low-carbon direct reduction iron process

Abstract

The invention provides a self-heating low-carbon direct reduction iron process, which is used for preparing reduced iron or sponge iron and comprises the following steps of: pre-reducing an iron raw material containing iron oxide in a preheating section of an electric heating shaft kiln; and directly electrifying the iron raw material or a solid material (hereinafter referred to as the solid material) obtained by changing the iron raw material in the heating process through a power supply electrode in a heating section of the electric heating shaft kiln, heating the material through resistance heating of a solid material pile in the heating section, and providing reaction heat for an endothermic reaction of reducing iron oxide by the hydrogen-rich gas. The method has the advantages of simple process flow, low carbon emission, low investment, high hearth utilization rate and high production capacity.

Description

Technical Field

[0001] The invention belongs to the field of iron and steel metallurgy and relates to a production process of reduced iron or sponge iron. Background Art

[0003] Since wind power and solar power generation are unstable and not synchronized with the peaks and valleys of electricity demand, energy storage for wind power and photovoltaics is also a huge problem. In recent years, the use of wind power and photovoltaics to electrolyze water to produce hydrogen has flourished. Biomass utilization can also skip the power generation step and directly produce synthesis gas and hydrogen. As an energy storage medium, hydrogen has huge advantages in that it has large capacity, can store energy for a long time without attenuation, and can also be used in the chemical and metallurgical industries. The hydrogen obtained by these process routes has a new name, called green hydrogen.

[0004] Therefore, the iron-making process that uses green electricity as a heat source and green hydrogen as a reducing agent has the basic conditions of energy and raw materials.

[0005] Existing hydrogen metallurgical ironmaking processes include the hydrogen-rich reduction blast furnace process and the gas-based (hydrogen) direct reduction process.

[0006] The hydrogen-rich process injects coke oven gas or other coal gas into the blast furnace. The hydrogen in coke oven gas has strong reducing ability. The amount of coke oven gas introduced determines the economic benefits and carbon reduction effect of the process. The higher the percentage of coke oven gas used, the better the carbon reduction effect. The reaction of H2 in coke oven gas to reduce ferric oxide is an endothermic reaction. The more hydrogen participates in the reduction process, the more oxygen-rich gas needs to be injected for heat compensation. The increase in oxygen-rich concentration strengthens the combustion of carbon in the cyclotron zone, which is conducive to the rapid descent of the charge. In 2020, Baowu conducted a hydrogen-rich carbon circulating oxygen blast furnace process experiment at Bayi Iron and Steel, connecting the decarbonized coal gas to the hydrogen-rich carbon circulating blast furnace, which reduced carbon emissions by 30% compared to traditional blast furnaces. According to the experiment of Meigang No. 2 blast furnace, the hydrogen-rich blast furnace process of injecting coke oven gas can reduce carbon emissions by about 10%. The hydrogen-rich reduction blast furnace process is an improvement on the existing long process, and the carbon reduction effect is limited.

[0007] The hydrogen direct reduction process or gas-based direct reduction process generally uses a vertical furnace (also called a vertical kiln, vertical kiln) device, which does not require coke and coking links. This short-process steelmaking process is to aggregate the iron ore concentrate into green balls with uniform particle size (about 10mm in diameter) and a certain strength. The green balls are roasted in a strong oxidizing atmosphere at 1150~1300℃ (optimal 1200℃) to complete decomposition, oxidation, desulfurization and other solid-phase reactions, converting magnetite into hematite to obtain high-strength oxidized pellets. The oxidized pellet roasting process uses natural gas as fuel, and one ton of oxidized pellets consumes about 32m natural gas. 3Then, the oxidized pellets are reduced with hydrogen (green hydrogen) at high temperature in a vertical kiln or rotary kiln to obtain direct reduced iron (sponge iron). This process can theoretically reduce carbon emissions from the ironmaking process by more than 90%.

[0008] As mentioned before, in the hydrogen-rich reduction blast furnace process, since the reduction of hematite by hydrogen at high temperature is an endothermic reaction, when the hydrogen utilization rate increases, it is necessary to introduce oxygen-rich gas to provide heat by combustion reaction. When the gas-based direct reduction ironmaking process is adopted, heat supply for the reaction becomes a more serious problem. The existing 1.2 million tons / year hydrogen metallurgical demonstration project in China is a gas-based direct reduction ironmaking process. The process adopts ENERGIRON technology to achieve extremely low carbon dioxide emissions. The project uses coke oven gas as a reducing agent, and the coke oven gas also contains a large amount of carbon-containing gas (CO and methane account for about 20% molar ratio). Although the process claims to have an innovative technical solution of zero reforming of raw gas, it adds water vapor to the circulating gas, and in order to provide heat for the reduction reaction, it also preheats the coke oven gas to 850°C, and then adds oxygen combustion to further heat the reduced gas entering the furnace to about 950°C. The reduced gas should actually undergo reforming or partial reforming reaction before entering the furnace. Nevertheless, the sensible heat of the oxidized pellets and the gas entering the shaft kiln is much less than the latent heat of reaction required for the reaction, so an excessive amount of hydrogen-rich raw gas is required to enter the shaft kiln, increasing the power of the gas circulation process and the burden of the purification process. Moreover, the hydrogen-rich gas, when heated to such a high temperature, requires high high-temperature hydrogen resistance and low safety for the materials of the heating equipment. Furthermore, the combustion reaction of oxygen does not necessarily occur at the site of the reduction reaction of hydrogen-oxidized iron. The addition of additional oxygen wastes reducing gas, generated water or CO2, which is not conducive to the reduction reaction of iron oxide. Therefore, it is difficult to control the rate and specific area of ​​the reduction reaction in the shaft kiln reactor. It should be noted that after the hydrogen-rich gas enters the reaction system, the hydrogen in it reduces the iron oxide to generate water, and the water and CO and / or methane will reform to generate hydrogen under the catalysis of the generated reduced iron, so the main gas involved in the reduction reaction is hydrogen. The process requires the iron content of the iron ore entering the furnace to be more than 66%, but my country lacks high-grade iron ore, and most of the iron ore has a low grade and contains increased harmful impurities, which cannot meet the quality requirements of raw materials for direct reduction iron production of the process.

[0009] Baowu Zhanjiang Steel's gas-based vertical furnace direct reduced iron process was ignited and put into operation in December 2023. This hydrogen-based vertical furnace also uses the ENERGIRON® direct reduced iron technology jointly developed by Tenova and Danieli. Thanks to the ENERGIRON® ZR zero reformer technology, this hydrogen-based vertical furnace will use natural gas, coke oven gas and a large proportion of hydrogen to produce 1 million tons of high-quality direct reduced iron per year. In other words, although the process has the potential to use full hydrogen reduction, it has not yet achieved full hydrogen reduction.

[0010] In order to solve the problem of heat supply to the endothermic reduction reaction, the FINEX process was developed abroad, which is a process for reducing multiple fluidized beds in series. This process is mainly developed for coal-based reduction, using the heat from the reaction of oxygen or air with coal to heat the reaction. When this process is used for gas-based reduction, it not only requires the raw gas to bring heat to the endothermic reduction reaction, but also requires the gas flow rate to be large enough to fluidize the powdered iron ore raw material. Therefore, a large gas flow rate is required, which is far in excess of the reduction equivalent required for the reduction reaction, and the raw gas temperature cannot be too high to avoid high temperature sintering the ore powder and destroying the fluidized state. Such a process scheme requires a large amount of high-temperature gas to be heated, dusted, transported, cooled, and circulated, which has high energy consumption, low reliability, and poor safety. Similar gas-based fluidized bed processes include Finored, HyREX, HYFOR, etc. The only difference is the type of reducing gas used and the form of iron ore.

[0011] In summary, there is no gas-based vertical furnace direct iron reduction process with completely independent intellectual property rights in China. Due to the huge production capacity of the steel industry, the hydrogen-rich gas reduction ironmaking process must be planned to have an annual production capacity of at least 500,000 tons. Whether using a vertical kiln, a rotary kiln or other forms of reactors, heat supply and heat transfer are a huge challenge for large-scale endothermic reactions. Heating hydrogen or hydrogen-rich gas presents huge safety risks and energy waste. Passing oxygen into reducing gases such as hydrogen or hydrogen-rich gas for combustion poses the risk of explosion and wastes reducing gas. The heat brought in by the raw gas is rapidly absorbed as the reduction reaction proceeds, the temperature of the gas and solid drops rapidly, the effective reaction area in the furnace shrinks rapidly, and the furnace utilization rate is low. Especially in the vertical furnace process, the materials cannot be stir-fried, and there is no complete gas space above the reduction reaction section materials like a rotary kiln, which can heat the reaction by heating the gas in the space. Summary of the invention

[0012] The object of the present invention is to provide a gas-based vertical furnace ironmaking process which can supply in situ the heat required for the endothermic reaction of reducing iron oxide with hydrogen-rich gas on a scale of one hundred thousand tons or even one million tons or more, thereby avoiding preheating of the hydrogen-rich gas entering the reduction reactor to a high temperature, and also avoiding the introduction of oxygen into flammable and explosive high-temperature gases such as hydrogen or coke oven gas, and greatly improving the utilization rate of the reactor furnace, thereby ultimately enabling the hydrogen-rich gas reduction low-carbon ironmaking process to be realized on a large scale, at a low cost, and with high safety requirements.

[0013] The object of the present invention is achieved by: in the gas-based shaft furnace direct reduction iron process, by directly electrifying the iron raw material or the solid material (hereinafter referred to as material) generated during the reaction process with a power supply electrode in the electric heating shaft kiln, the material is heated by the resistance of the material pile itself under the action of the current to provide heat for the endothermic reaction. The gas withdrawn from the electric heating shaft kiln is subsequently treated and utilized.

[0014] The specific technical solutions are: A self-heating low-carbon direct iron reduction process, wherein an iron raw material containing iron oxide is fed into an electric heating vertical kiln for heating, and during the heating process, the iron oxide reacts with a hydrogen-rich gas for reduction to obtain reduced iron, characterized in that the process consists of an electric heating reduction process and an exhaust gas treatment process. The iron raw material is one or more of iron-containing dust in the steel industry, sea sand ore, block iron ore, sintered iron ore, iron ore powder formed pellets, or oxidized pellets obtained by oxidative roasting, and pellets formed by iron oxide. The technical solution of the present invention has no special requirements on the type of raw material ore, the occurrence form or crystal phase of iron in the ore, and has no special requirements on the types of common impurities in the ore and their occurrence forms, but has certain requirements on the iron content in the ore, requiring the total average total iron content of various iron-containing raw materials entering the kiln to be more than 40%, preferably more than 45%. The electric heating reduction process is as follows: in the heating section of an electric heating shaft kiln (hereinafter referred to as a shaft furnace or shaft kiln), the iron raw material and / or the material obtained by the change in the heating process (hereinafter referred to as the material) are directly electrified through a power supply electrode, and the material pile is heated by its own resistance. The material passes through a preheating section, a heating section, and a cooling section from top to bottom in the electric heating shaft kiln, and then is discharged; and the highest temperature of the material in the electric heating shaft kiln is not less than 600°C and not more than 1250°C; the material is withdrawn from the heating section in the preheating section. The gas is preheated and partially pre-reduced by the reducing gas in the gas phase so that its conductivity is improved; the iron oxide is reduced by the hydrogen-rich gas in the heating section to generate direct reduced iron or sponge iron; the hydrogen-rich gas enters the electric vertical kiln and passes through the cooling section, heating section and preheating section of the electric vertical kiln from bottom to top, and then withdraws from the electric vertical kiln; the hydrogen-rich gas is preheated by heat exchange with the material withdrawn from the heating section in the cooling section of the electric vertical kiln; the gas withdrawn from the electric vertical kiln enters the tail gas treatment process; the gas pressure of the gas in the electric vertical kiln is less than 1MPa.

[0015] It is further preferred that the highest temperature that the material passes through in the electric vertical kiln is not less than 650°C and not more than 1100°C. At too low a reaction temperature, the reduction reaction rate of iron oxide is very slow. However, too high a reaction temperature makes it easy for the materials in the heating section to stick together, and even causes the kiln to be blocked. Since the material in the heating section is directly heated by electricity, the main reduction reaction occurs in the heating section. When the current is uneven in the heating section, that is, the reaction section, the path with a larger current generates a large amount of heat. The temperature of the material on this path increases, and the reaction may be accelerated, resulting in a faster increase in the metallization rate, and a further decrease in the resistivity, resulting in a further increase in the current. This vicious cycle causes the material in the area to stick together or even melt. Finally, it may cause the material to become compacted or caught (incomplete reaction). In severe cases, it may cause the material on the path to melt or block the vertical furnace hearth.

[0016] Furthermore, the electric heating shaft kiln is: the furnace heating section is provided with a plurality of electrodes of a heating power source, through which a voltage is applied to the heated material so as to feed current to the heated material, and the heated material is heated by utilizing the resistance heating of the heated material accumulated in the heating section; the electric heating shaft kiln also has a preheating section and a cooling section; the material passes through the preheating section, the heating section and the cooling section in the electric heating shaft kiln in sequence; the electric heating shaft kiln is provided with a gas inlet at one end of the cooling section and a gas outlet at one end of the preheating section. The heating power source electrode of the electric heating shaft kiln can be embedded in the furnace wall, and the current path passes through the material in the heating section.

[0017] Furthermore, the hydrogen-rich gas is one or more of coal gas, shale gas, coalbed methane, coke oven gas, water gas, blast furnace gas, synthesis gas (synthesis gas is generally obtained by reforming coal, natural gas, oil or hydrocarbons with oxygen and / or water, containing hydrogen and CO), methanol, ammonia, straw gasification gas, methane, natural gas, or hydrogen is added to the above gases. The methane or other carbon-containing components in these gases will reform with the water generated during the reaction to generate hydrogen and CO and / or CO2, so the reducing component that undergoes the reduction reaction with the iron ore is mainly hydrogen.

[0018] Furthermore, the tail gas treatment process is that the tail gas is subjected to dust removal, dehydration, and decarbonization processes, and then mixed with fresh hydrogen-rich gas and enters the electric heating vertical kiln for recycling. The decarbonization process is to remove carbon dioxide and / or part of carbon monoxide in the tail gas. The commonly used triethanolamine decarbonization process can be used. Dust removal can be carried out by a cyclone separator and / or a bag filter, or by water spraying, while removing dust and a large amount of water vapor in the tail gas. When there is ammonia or nitrogen in the raw gas, a denitrification process needs to be added to the tail gas treatment process. Of course, denitrification can be carried out by carbon molecular sieve pressure swing adsorption and other process methods.

[0019] Alternatively, the hydrogen-rich gas is hydrogen. Photovoltaic and wind power can produce a large amount of green hydrogen. At present, electrolysis consumes about 45-55 kwh of electricity per kilogram of hydrogen. When the hydrogen-rich gas is pure hydrogen, the tail gas treatment process is to remove dust and dehydrate the tail gas withdrawn from the electric heating shaft kiln, and then mix it with fresh hydrogen and enter the electric heating shaft kiln for recycling.

[0020] Since the electric heating vertical kiln equipment is used as the reactor for the reduction reaction, the gas phase and the solid phase materials are in full contact, and the self-heating method of directly energizing the solid phase materials is adopted, the material heating and reduction reaction in the heating section can be timely supplemented with heat, so the heat required for the reaction and the sensible heat carried by the gas entering the electric heating vertical kiln are decoupled, so that there is no special requirement for the amount and temperature of the gas entering the electric heating vertical kiln - further, the air intake can be greatly reduced, and the air intake is only determined according to the needs of the reduction reaction. After the intake of hydrogen-rich gas is greatly reduced, not only the load of the tail gas treatment process is greatly reduced, but also the tail gas can be simply not recycled, and the tail gas treatment process is simplified to the combustion of the tail gas. The combustion process can be used to provide heat for the sintering of iron ore pellets and granular ore, produce oxidized pellets or sintered ore, and further reduce carbon emissions in the ironmaking process. The combustion process can also be used to preheat the hydrogen-rich gas before entering the electric heating vertical kiln to reduce the power consumption of the electric heating of the electric heating vertical kiln. Of course, the combustion process can also be used to generate electricity, which can further provide electricity for the electric heating process of the electric heating shaft kiln.

[0021] Compared with the prior art, the present invention has the following advantages: 1) Compared with the traditional blast furnace ironmaking process, the ironmaking process of the present invention can reduce carbon emissions by more than 50%.

[0022] 2) When green hydrogen is used as a reducing agent, carbon emissions can be reduced by more than 90%. When a small amount of hydrogen tail gas is burned into sintered oxide pellets and / or sintered ore, the ironmaking process can achieve zero carbon emissions. And the tail gas treatment process is simplified.

[0023] 3) Compared with the existing gas-based vertical furnace direct reduction process, the technical solution of the present invention can control a clear reaction area and control the heating section as the main reaction area. In the reaction area, the material temperature does not drop rapidly as the reaction proceeds, which greatly improves the furnace utilization of the vertical kiln.

[0024] 4) Compared with the existing gas-based vertical furnace direct reduction process, the technical solution of the present invention does not require the high-temperature hydrogen-rich gas feed gas to bring in sensible heat to provide heat for the reaction. It can minimize the excess amount of hydrogen-rich gas while meeting the degree of iron ore reduction, thereby greatly reducing the load of tail gas treatment.

[0025] 5) In contrast, the existing gas-based vertical furnace process uses iron ore with an iron grade of up to 66-69%. However, domestic high-grade iron ore needs to be imported. Moreover, worldwide, such high-grade iron ore reserves only account for about 3% of the total iron ore reserves. Experiments have shown that the direct iron reduction process of the present invention can use iron ore raw materials with an iron content as low as 45%. It is of great significance to the utilization of low-grade iron ore.

[0026] 6) Compared with the existing gas-based direct reduction process, it is not necessary to add oxygen-enriched or oxygen to the incoming gas to make it burn for reaction heat, nor is it necessary to preheat the raw gas at high temperature. The process and equipment are simplified, safety is improved, equipment investment is reduced, and operating costs are reduced.

[0027] 7) Compared with the existing rotary kiln direct iron reduction process, the technical solution of the present invention can not only effectively provide heat for the reduction reaction, but also greatly improve the furnace utilization rate, avoiding the problem of low furnace material filling rate in the reaction section of the rotary kiln and the lack of solid material in the upper part causing gas flow short circuit.

[0028] In summary, the present invention has opened up a technical route for the low-carbon ironmaking process using hydrogen-rich gas as a reducing agent, which has low carbon emissions, high safety, low investment and low operating costs, high reliability, and practical technology. DETAILED DESCRIPTION

[0029] The specific technical solutions of the present invention are described below in conjunction with the accompanying drawings and embodiments.

[0030] Attached Figure 1 It is a process flow chart of the self-heating low-carbon direct reduction iron of Example 1.

[0031] Attached Figure 2 It is a process flow chart of the self-heating low-carbon direct reduction iron of Example 2. Example

[0032] This embodiment adopts the coke oven gas reduction low carbon ironmaking process. The process flow chart is as shown in the attached figure. Figure 1 shown.

[0033] Iron ore pellets are oxidized and roasted to obtain oxidized pellets. In this embodiment, oxidized pellets with an iron content of about 54% are used as iron raw materials. Without preheating, they are directly fed into the charging hopper of the electric heating shaft kiln. As the solid material moves downward, the oxidized pellets enter the preheating section of the electric heating shaft kiln. In the preheating section, they exchange heat with the high-temperature gas (containing water vapor generated by the reduction reaction) from the heating section of the shaft kiln. When they are preheated to about 650°C, the oxidized pellets are partially reduced and become conductive. After the oxidized pellets move to the heating section, electrodes of a heating power supply are provided on the kiln chamber wall of the heating section, which feed current into the material in the heating section. The material is heated by the current, and the temperature is further increased to 950-1100°C. In the heating section, the iron oxide in the oxidized pellets is reduced to directly reduced iron. As the degree of reduction increases, the material resistance decreases, the reduction reaction also decreases, and the demand for heat is also reduced accordingly. The voltage of the heating power supply at this location is reduced to reduce the calorific value. The material leaving the heating section exchanges heat with the room temperature or low temperature coke oven gas entering the kiln, which reduces the material temperature and also preheats the coke oven gas. The coke oven gas already has a relatively high temperature when it enters the heating section.

[0034] The gas withdrawn from the feed end of the electric heating shaft kiln contains dust, a large amount of water and CO2. It is cleaned in the dust removal and dehydration process, and the CO2 is removed in the decarbonization process. The dust removal and dehydration process first uses circulating water spray to remove dust and most of the water in the circulating gas. Then it passes through molecular sieves or condensation drying. The obtained circulating gas, together with the fresh coke oven gas, basically enters the electric heating shaft kiln at room temperature.

[0035] Compared with the most advanced existing gas-based reduction ironmaking process (Zhang Xuan Technology's 1.2 million tons / year ironmaking process), the process of this embodiment lacks the processes of oxygen production (or oxygen-enriched gas), oxidized pellet spraying cement, preheating the intake air before entering the kiln, and adding oxygen-enriched or oxygen to the intake air. The process of this embodiment is simple and safe, and avoids the safety risks of high-temperature preheating of coke oven gas and adding oxygen or oxygen-enriched gas to combustible gases such as coke oven gas to cause explosions. In addition, the reduction reaction is fully carried out in the entire heating section, and the utilization rate of the kiln chamber is greatly improved. The process route of the present invention greatly reduces investment costs and operating costs. This embodiment and the present invention have opened up a safe, reliable, and economically feasible technical route for large-scale green electricity hydrogen-rich gas low-carbon ironmaking process. Example

[0036] This embodiment adopts the green hydrogen and green electricity reduction zero-carbon ironmaking process. The process flow chart is as shown in the attached Figure 2 shown.

[0037] Iron ore pellets are oxidized and roasted to obtain oxidized pellets. In this embodiment, oxidized pellets with an iron content of about 54% are used as iron raw materials. Without preheating, they are directly fed into the charging hopper of the electric heating shaft kiln. As the solid material moves downward, the oxidized pellets enter the preheating section of the electric heating shaft kiln. In the preheating section, they exchange heat with the high-temperature gas (containing water vapor generated by the reduction reaction) from the heating section of the shaft kiln. When they are preheated to about 650°C, the oxidized pellets are partially reduced and become conductive. After the oxidized pellets move to the heating section, electrodes of a heating power supply are provided on the kiln chamber wall of the heating section, which feed current into the material in the heating section. The material is heated by the current, and the temperature is further increased to 950~1150°C. The iron oxide in the oxidized pellets in the heating section is reduced to directly reduced iron. As the degree of reduction increases, the material resistance decreases, the reduction reaction also decreases, and the demand for heat is also reduced accordingly. The voltage of the heating power supply at this location is reduced to reduce the calorific value. The material leaving the heating section exchanges heat with the normal temperature or low temperature hydrogen entering the kiln, which lowers the material temperature and preheats the hydrogen. The hydrogen already has a high temperature when it enters the heating section. In the cooling section, the preheated hydrogen may also react with the high temperature material, further improving the degree of iron reduction, and the metallization rate of iron in the material leaving the kiln reaches more than 95%.

[0038] The hydrogen feed rate of the vertical kiln is controlled so that the hydrogen is 30-200% more than the reducing equivalent required for the oxidized pellets entering the electric thermal vertical kiln at the same time.

[0039] The gas withdrawn from the feed end of the electric heating shaft kiln contains dust and a large amount of water. The tail gas treatment process first uses circulating water spray to remove dust and most of the water in the tail gas. Part of the tail gas is transported to the oxidation pellet sintering process through the Roots blower to burn the sintered pellets or granular iron ore to achieve carbon-free sintering of the oxidation pellets or sintered ore. This process not only simplifies the tail gas treatment process, but also eliminates carbon emissions during the oxidation pellet sintering process.

[0040] Combined with the use of green electricity for heating in the electric vertical kiln and the use of green electricity in the auxiliary process, this embodiment can achieve zero carbon emissions in the ironmaking process.

[0041] The technical solution of the present invention can not only adopt iron ore raw materials with relatively high iron content, but also some types of ores with iron content as low as 40% can adopt the technical solution of the present invention; iron ore with iron content higher than 45% or dust from other steel industries can definitely adopt the technical solution of the present invention.

Claims

1. A self-heating low-carbon direct iron reduction process, wherein an iron raw material containing iron oxide is fed into an electric heating shaft kiln for heating, and during the heating process, the iron oxide reacts with hydrogen-rich gas to obtain reduced iron, characterized in that: The process is composed of an electric heating reduction process and a tail gas treatment process; The iron raw material is one or more of iron-containing dust in the steel industry, sea sand ore, lump iron ore, sintered iron ore, pellets formed from iron ore powder, oxidized pellets obtained by oxidative roasting, and pellets formed from iron oxide; The electric heating reduction process is as follows: in the heating section of the electric heating shaft kiln, the iron raw material and / or the material obtained by the change in the heating process (hereinafter referred to as the material) are directly electrified through the power supply electrode, the material pile is heated by its own resistance, the material passes through the preheating section, the heating section and the cooling section from top to bottom in the electric heating shaft kiln, and then is discharged; and the highest temperature of the material in the electric heating shaft kiln is not less than 600° C. and not more than 1250° C.; the material is preheated by the gas withdrawn from the heating section in the preheating section and is partially pre-reduced by the reducing gas in the gas phase, so that its conductivity is improved; the iron oxide is reduced by the hydrogen-rich gas in the heating section to generate direct reduced iron or sponge iron; After entering the electric heating shaft kiln, the hydrogen-rich gas passes through the cooling section, heating section and preheating section of the electric heating shaft kiln from bottom to top, and then withdraws from the electric heating shaft kiln; the hydrogen-rich gas is preheated by heat exchange with the material withdrawn from the heating section in the cooling section of the electric heating shaft kiln; the gas withdrawn from the electric heating shaft kiln enters the tail gas treatment process; The gas pressure in the electric heating vertical kiln is less than 1 MPa.

2. The autothermal low-carbon direct iron reduction process according to claim 1, characterized in that: Preferably, the highest temperature that the material passes through in the electric heating shaft kiln is not less than 650°C and not more than 1100°C.

3. The autothermal low-carbon direct iron reduction process according to any one of claims 1 and 2, characterized in that: The furnace heating section of the electric heating shaft kiln is provided with a plurality of electrodes of a heating power supply, through which a voltage is applied to the heated material so as to feed current into the heated material, and the heated material is heated by utilizing the resistance heating of the heated material accumulated in the heating section; the electric heating shaft kiln also has a preheating section and a cooling section; the material passes through the preheating section, the heating section and the cooling section in sequence in the electric heating shaft kiln and then is discharged; the electric heating shaft kiln is provided with a gas inlet at one end of the cooling section and a gas outlet at one end of the preheating section; the hydrogen-rich gas passes through the cooling section, the heating section and the preheating section in sequence after entering the shaft kiln.

4. The autothermal low-carbon direct iron reduction process according to any one of claims 1 to 3, characterized in that: The hydrogen-rich gas is one or more of coal gas, shale gas, coalbed methane, coke oven gas, blast furnace gas, water gas, synthesis gas, methanol, ammonia, straw gasification gas, methane, and natural gas, or hydrogen is added to the above gases.

5. The autothermal low-carbon direct iron reduction process according to claim 4, characterized in that: The tail gas treatment process is that the tail gas undergoes dust removal, dehydration and decarbonization processes, and then is mixed with fresh hydrogen-rich gas and enters the electric heating vertical kiln for recycling; the decarbonization process is to remove carbon dioxide and / or part of carbon monoxide in the tail gas.

6. The autothermal low-carbon direct iron reduction process according to claim 4, characterized in that: The tail gas treatment process is that the tail gas undergoes dust removal, dehydration, decarbonization and denitrification, and then is mixed with fresh hydrogen-rich gas and enters the electric heating vertical kiln for recycling; the decarbonization process is to remove carbon dioxide and / or part of carbon monoxide in the tail gas; the denitrification process is to remove nitrogen in the tail gas.

7. The autothermal low-carbon direct iron reduction process according to any one of claims 1 to 3, characterized in that: The hydrogen-rich gas is hydrogen.

8. The autothermal low-carbon direct iron reduction process according to claim 7, characterized in that: The tail gas treatment process is to remove dust and dehydrate the tail gas withdrawn from the electric heating shaft kiln, and then mix it with fresh hydrogen and enter the electric heating shaft kiln for recycling.

9. The autothermal low-carbon direct iron reduction process according to any one of claims 1 to 3, characterized in that: The tail gas treatment process is to burn the tail gas.

10. The autothermal low-carbon direct iron reduction process according to claim 9, characterized in that: The tail gas treatment process is to burn the tail gas for sintering the oxidized pellets and / or sintering the iron ore; or the tail gas treatment process is to burn the tail gas for preheating the hydrogen-rich gas before entering the electric heating shaft kiln.

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