Carbon-based direct reduction iron process for electric heating rotary kiln

Abstract

According to the carbon-based direct reduction iron process for the electric heating rotary kiln, iron ore is reduced through solid carbon, and a preheating section, a reduction section and a cooling section are sequentially arranged from the feeding end to the discharging end of a hearth of the electric heating rotary kiln. And a heating power supply electrode is arranged on the furnace wall of the reduction section. Iron ore sequentially passes through the preheating section, the reduction section and the cooling section. And the solid carbon particles enter the hearth in the form of external carbon. The iron oxide is mainly reduced by hydrogen and CO generated by solid carbon reaction. The method has the advantages that the sintered ore and / or the oxidized pellets can be directly used as the furnace-entering iron ore raw materials, the materials are not prone to bonding and blocking a kiln, heat can be effectively provided for the reduction reaction, the advantage that the reduction reaction speed of hydrogen and CO is high is utilized, low-cost carbon resources can be utilized, and carbon emission is greatly reduced.

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

[0002] At present, the steelmaking process is still mainly a long process of blast furnace-converter, which has high carbon emissions.

[0003] Coal-based direct reduced iron generally adopts the rotary kiln process. During the reduction process, secondary air is blown into the middle of the rotary kiln, and burns with CO in the atmosphere in the kiln to generate heat for the reduction reaction. Since the reaction rate of CO and iron oxide reduction is slow when the temperature is lower than 800℃, the temperature in the kiln is generally controlled to be above 800℃. At this time, CO2 will react with solid carbon to generate CO. In addition, CO2 generated by CO reducing iron oxide will also undergo the above reaction. Therefore, in general, solid carbon reduces iron oxide to generate direct reduced iron, and solid carbon reacts with oxygen to generate CO. The reaction of solid carbon reducing iron oxide to generate metallic iron and CO is an endothermic reaction. Therefore, a large amount of carbon is burned to provide heat for the main reduction reaction and to provide heat for other heat dissipation processes. Only part of the solid carbon is used as a reducing agent. This also leads to a relatively low content of reducing gas in the rotary kiln tail gas, and it also contains a large amount of nitrogen brought in by the secondary air, making the recycling cost of the tail gas high and the value low.

[0004] The above is also the reason why coal-based direct reduced iron generally adopts rotary kiln process instead of vertical furnace process. Because in the vertical furnace, at above 800℃, solid carbon reduces iron oxide to generate metallic iron and CO. This reaction needs to absorb heat, and direct reduced iron requires large-scale production. In a larger vertical furnace reactor, it is difficult to provide heat to various parts of the furnace, especially the materials in the center of the furnace. In addition, the materials in the vertical furnace are easy to harden and block the furnace at the reaction temperature, so that the reaction process cannot be carried out stably for a long time.

[0005] In the process of producing direct reduced iron in coal-based rotary kiln, in order to effectively conduct heat and mass transfer, the material filling rate in the rotary kiln is relatively low, generally not exceeding 20%. This leaves a large space above the material in the rotary kiln, where a large amount of gas gathers and quickly flows out of the rotary kiln, that is, the gas flows through the space in a short circuit, resulting in low contact efficiency between gas and solid materials, low mass and heat transfer efficiency, low gas conversion rate, low furnace utilization rate, and low equipment capacity.

[0006] Analysis of the direct reduction iron process in an electric vertical kiln is similar to the electric vertical furnace for the production of vanadium-nitrogen alloys. Since electric current is passed through the material in the reaction section, the higher the material temperature, the faster the reduction reaction rate, the higher the metallization rate, and the smaller the material resistance, which further increases the material current at this point, further pushing up the material temperature, forming a vicious cycle, causing the material to overheat and agglomerate until it blocks the furnace. Due to the deterioration of mass transfer performance, the unreacted materials in the overheated sintered materials cannot effectively undergo a reduction reaction, forming raw materials. In addition, in the vertical furnace, high-volatile lignite is used as a reducing agent. During the heating process, lignite will volatilize a large amount of organic matter, which will further form high-molecular materials under heating conditions, causing blockage of the material bed.

[0007] In the existing rotary kiln, the material is directly heated by electricity to reduce iron oxide. In order to improve the conductivity of the iron ore material during the reduction process, the close contact between the solid carbon and the solid iron oxide, or other undisclosed reasons, the carbon powder and the iron oxide or iron ore are ground and mixed and then formed, and the mixture is fed into the kiln in the form of internal carbon. However, this requires the production of iron ore pellets or iron ore oxidized pellets for this process separately, and is not suitable for sintered ore. Moreover, before oxidative roasting, the iron ore and solid carbon are mixed and formed. In the subsequent oxidative roasting, part of the reducing carbon will be burned, which reduces the strength of the oxidized pellets. In addition, during the reduction process, due to the reaction of the internal carbon, the pellets become too loose and the apparent density is greatly reduced, which greatly reduces the strength of the pellets, and a large amount of fine particles or powder is generated during the reduction process. When coal or coke is used as a reducing agent, the internal carbon also causes the ash in the coal to remain in the pellets, which is difficult to separate at low cost through magnetic separation or air separation processes. These unfavorable factors are harmful to both the reduction process itself and the subsequent melting process.

[0008] The coal-based vertical furnace direct iron reduction process has the risk of material compaction, and it is inconvenient to use high-volatile coal as a reducing agent. The coal-based rotary kiln uses secondary air to burn into the furnace to provide heat for the reduction reaction, and the tail gas is difficult to recycle. It also has disadvantages such as low filling rate, low production efficiency, and high carbon emissions. Whether using a vertical furnace or a rotary kiln, heat supply and heat transfer are huge challenges for large-scale endothermic reactions. Since hydrogen is expensive and coke oven gas and blast furnace gas are not easy to obtain; using water gas as the reducing gas actually still uses coal or coke as the reducing agent. Therefore, the coal-based direct iron reduction process, even if it is the existing rotary kiln coal-based direct iron reduction process, still has a certain vitality. Summary of the invention

[0009] The purpose of the present invention is to provide an electric heating rotary kiln coal-based direct iron reduction process, which has a large production scale, can use the oxidized pellets and / or sintered ore used in the existing blast furnace or shaft furnace as iron ore raw materials, can use coal or other low-cost carbon as a reducing agent, use electric heat to replace secondary blast combustion to provide heat for the reduction reaction, has a high furnace utilization rate, occupies a small area of ​​equipment, can effectively provide heat for the reduction reaction in the furnace material, eliminate the problem of furnace blockage, reduce the complexity of the process flow and kiln equipment, reduce carbon emissions, and reduce investment and operating costs, so that the electric heating rotary kiln coal-based direct iron reduction process can be realized under the premise of large-scale, low-cost and high safety requirements.

[0010] The object of the present invention is achieved in that: In the electric heating rotary kiln process, iron ore is added to the rotary kiln furnace in the form of oxidized pellets or sintered ore, which contain little or no carbon. Coke, semi-coke, lignite and / or solid organic carbon enter the rotary kiln in the form of external carbon at the particle level, and oxidized pellets and / or sintered ore enter the furnace from the tail gas outlet of the rotary kiln. Solid organic carbon will be carbonized into carbon particles at high temperature. Since the added solid carbon is only used as a reducing agent and the amount added is relatively small, it has little effect on the conductivity of the pre-reduced iron ore pellet pile.

[0011] Since the contact area between the iron ore particles and the carbon particles is very small, it is not conducive to the direct reaction of carbon and iron oxides. Therefore, one or more gases of hydrogen, water, CO and carbon dioxide are introduced at the tail end of the rotary kiln reduction section, which are referred to as reducing gas in the present invention. The water in the reducing gas reacts with the carbon to generate CO and hydrogen, and / or the carbon dioxide reacts with the carbon to generate CO. Finally, the iron oxides are reduced by hydrogen and / or CO. The generated CO2 will also react with the carbon to generate CO again. The diffusion rate of hydrogen is faster than that of CO, and the reaction with iron oxides is also faster than that of CO.

[0012] As mentioned above, in order to increase the reaction rate, the reduction reaction is generally carried out at a higher temperature. When the reaction temperature is above 850°C, the overall reduction reaction is a reaction in which solid carbon reduces iron oxide to generate CO and metallic iron, or a reaction in which hydrogen reduces iron oxide to generate water and metallic iron. Both reactions are endothermic reactions and require heat from the outside.

[0013] The iron oxides in the preheating section will exchange heat with the gas withdrawn from the reduction section and be partially reduced, so that the materials entering the reduction section have a certain conductivity. The electrodes of the heating power supply are set on the furnace wall of the reduction section, and the materials in this section are directly energized, using the material's own resistance to generate heat, providing heat for the reduction reaction and other heat dissipation processes.

[0014] The specific technical solution for achieving the purpose of the present invention is: An electric heating rotary kiln carbon-based direct iron reduction process, which uses solid carbon to reduce iron ore, is characterized in that: the rotary kiln has an internal cavity that is close to a cylindrical or prismatic shape as a furnace, one end of the rotary kiln has a feed port and an exhaust gas outlet, and the other end has a discharge port and a reducing gas inlet, and reducing gas is introduced into the rotary kiln from the inlet. The furnace is provided with a preheating section and a reducing section from the feed end to the discharge end. A heating power supply electrode is provided in the reducing section, which is used to energize the conductive material in the section to heat the material.

[0015] The iron ore contains iron oxides, which are one or more of iron oxide, ordinary iron ore, ilmenite, vanadium-titanium magnetite, hematite, recovered iron-containing dust particles, and graded pre-selection, molding, pre-burning, and pre-reduction products of the above materials; the iron content in the iron ore is above 40%.

[0016] The solid carbon is one or more of coal, charcoal, coke, blue charcoal, activated carbon, graphite, petroleum coke, asphalt, and solid organic matter, that is, a carbon-containing solid material that can be thermally decomposed at the reaction temperature or whose volatile matter can reduce iron oxides, or can react with water and / or carbon dioxide. This greatly expands the scope of carbon raw materials, and cheaper or more environmentally friendly carbon raw materials can be used. In particular, lignite with a high volatile content can provide a large amount of organic matter, which is beneficial to this process.

[0017] The reducing gas is one or more of hydrogen, CO, ammonia, water, carbon dioxide, gaseous organic matter, and volatile organic matter.

[0018] After the iron ore and solid carbon (hereinafter referred to as materials) enter the furnace of the rotary kiln, they are piled up into a material bed layer inside the furnace. The tail gas outlet end of the rotary kiln furnace, i.e., the iron ore feed end, is located higher than the discharge end, i.e., the reducing gas inlet end. As the rotary kiln rotates, the materials move from the high end to the low end by gravity and move out of the furnace from the discharge port. The materials in the furnace pass through the preheating section and the reduction section in turn, and then obtain direct reduced iron; in the preheating section, the materials are preheated by the gas withdrawn from the reduction section and partially pre-reduced to obtain a certain conductivity, and then enter the reduction section, where the heating power supply electrode feeds current to the materials in the section, and the materials are heated by the resistance heat generated by the materials themselves.

[0019] Part or all of the solid carbon is fed into the rotary kiln in the form of external carbon. By using the external carbon, low-cost carbon such as lignite and blue charcoal can be used as the reducing agent raw material, or the oxidized pellets and / or sintered ore from blast furnace ironmaking can be directly used as the iron ore raw material. The pellets have high strength, low sulfur and phosphorus impurities, and the raw materials are easy to obtain and low in cost. The method of directly heating the raw materials with electricity is adopted to provide heat for the reduction reaction. The solid carbon is only used as a reducing agent, so the amount added is relatively small. When lignite and coke are used as raw materials, the ash brought in by fewer carbon particles is also relatively small, and the ash is not conductive, so the addition of less solid carbon is beneficial to the improvement of the conductivity of the material bed. When solid carbon is added in the form of external carbon, the ash brought in by the solid carbon in the material out of the kiln is not magnetic and has a low density, so it can be conveniently separated from the direct reduced iron pellets or particles by magnetic separation or air separation.

[0020] When lignite and / or high-volatile coal is used as a reducing agent, the coal powder can be sprayed into the furnace of the rotary kiln from the discharge end by coal injection, or it can be injected into the furnace of the rotary kiln together with the iron ore from the feed end of the rotary kiln. Preferably, the coal powder is sprayed into the reduction section of the furnace of the rotary kiln from the discharge end by coal injection. The volatile matter in the coal undergoes a process of decomposition and volatilization at high temperature, and reacts with carbon dioxide and / or water in the solid carbon and / or gas phase to generate CO and / or hydrogen. Hydrogen and / or CO further reduce the iron oxide.

[0021] The existing internal carbon direct reduction iron process mainly reacts solid carbon and solid iron oxide in a solid phase, and the reaction speed is relatively slow. Vacuuming or lower gas pressure is conducive to the reaction. The iron oxide reduction reaction described in the present invention is mainly a gas-solid reaction, the reducing agent directly involved in the reduction reaction is a gas, and the product is solid metallic iron and gaseous carbon dioxide or water. The reaction speed is fast, and maintaining a higher gas pressure is conducive to the occurrence of the reaction, and the solid carbon raw material does not need to be finely ground before use.

[0022] The non-volatile solid carbon in the external carbon will also react with the water and / or carbon dioxide in the reducing gas, or with the water and / or carbon dioxide generated by the reduction reaction, to generate hydrogen and / or CO. The non-volatile solid carbon enters the rotary kiln furnace from the feed end of the rotary kiln together with the iron ore. Due to the rotary mixing effect of the rotary kiln, the non-volatile solid carbon can be directly mixed into the kiln after metering without being pre-mixed with the iron ore particles. This process does not adopt the form of internal carbon, or only uses part of the solid carbon in the form of internal carbon when it is necessary to achieve other technical purposes.

[0023] The gas from the reduction section may or may not pass through a water-gas shift process, and then undergo a decarbonization and dehydration process to remove carbon dioxide and / or water therein, and then enter the rotary kiln as a reducing gas for recycling.

[0024] Furthermore, the reducing gas may be non-reducing gaseous water. The water component is introduced into the electric heating rotary kiln at a position where the furnace and / or material temperature of the electric heating rotary kiln is greater than or equal to 700° C. After entering the reduction section, the water reacts with the solid carbon to generate CO and hydrogen.

[0025] Alternatively, the reducing gas may be non-reducing carbon dioxide. The carbon dioxide component is introduced into the electric rotary kiln at a position where the furnace and / or material temperature of the electric rotary kiln is greater than or equal to 700°C. One molecule of carbon dioxide enters the reduction section and reacts with solid carbon to generate two molecules of CO.

[0026] Furthermore, the gas after the reduction stage and / or preheating stage undergoes a water-gas shift reaction to convert part or all of the CO therein into hydrogen, and then undergoes a decarbonization treatment, and the obtained hydrogen enters the electric rotary kiln as all or part of the reduction gas entering the furnace for recycling.

[0027] After recycling the reducing gas in the tail gas, the overall reaction is that solid carbon reduces iron oxide to generate carbon dioxide and / or hydrogen in the volatiles in the solid carbon reduces iron oxide to generate water. Considering only the case of using volatile-free carbon, theoretically, one ton of direct reduced iron requires 161 kg of carbon. In existing blast furnace ironmaking, coal and coke or coke powder consumes about 500 kg per ton of iron. If vanadium-titanium magnetite is used as the raw material, it consumes 530 kg, of which at least 350 kg is coke. The carbon emissions of the technical solution of the present invention are greatly reduced. Considering the carbon emissions in the coke production process, the carbon emissions of the technical solution of the present invention are reduced even more. Although the technical solution of the present invention requires electricity for heating, under the extremely energy-saving and optimized process conditions, the reduction in carbon emissions is also achieved by replacing coal with electricity, especially by replacing coal with green electricity.

[0028] Furthermore, the reduction equivalent of the solid carbon and reducing gas entering the rotary kiln exceeds the equivalent required for the reduction reaction of the iron oxide in the iron ore in the electric heated rotary kiln, so that the obtained direct reduced iron has a carburization content of more than 1% by weight.

[0029] Furthermore, the reduction equivalent of the solid carbon and the reducing gas entering the rotary kiln exceeds the equivalent required for the reduction reaction of the iron oxide in the iron ore in the electric heating rotary kiln, and there is also some unreacted residual carbon in the obtained direct reduced iron; the residual carbon accounts for more than 0.3% of the weight of the obtained material. The residual carbon is in the form of a single particle or powder or remains in a single particle or powder remaining after the reaction of the solid carbon.

[0030] Furthermore, the rotary kiln is provided with a cooling section at one end of the reduction section near the discharge end; reducing gas other than water and / or carbon dioxide enters the cooling section from the discharge end of the cooling section. The material enters the cooling section from the reduction section, exchanges heat with the reducing gas, preheats the gas, and cools the material. When the subsequent melting process requires hot charging of direct reduced iron, no cooling section is provided or a shorter cooling section is provided. When the subsequent slag-iron separation process requires cold direct reduced iron, a longer cooling section with better cooling effect is provided.

[0031] Furthermore, the maximum temperature of the reduction stage is controlled to be not less than 850°C, preferably between 850 and 1300°C. Controlling a higher maximum temperature is conducive to the occurrence of iron reduction reaction, water-gas reaction, or the reaction of carbon dioxide and solid carbon to generate CO, and is also conducive to the growth of generated metallic iron particles and the separation of slag and iron. Compared with the shaft furnace direct iron reduction process, the probability of material adhesion and kiln blocking in this process is reduced, and a higher maximum temperature of the reduction stage can be controlled.

[0032] Furthermore, the filling rate of the material in the reduction section of the rotary kiln furnace is above 25%. Since the material bed is directly heated by electricity, the heat transfer problem is solved. Under the premise of taking into account the gas phase mass transfer, a higher material filling rate in the reduction section is adopted, which is conducive to improving the equipment productivity and reducing the power consumption per unit of direct reduced iron product.

[0033] Furthermore, preferably, the iron content in the iron ore is above 50%. A higher iron content makes the conductivity of the material bed in the reduction section better.

[0034] The direct iron reduction process of the present invention can be conveniently operated at a pressure ranging from slightly negative pressure to below 1 MPa.

[0035] Compared with the prior art, the present invention has the following advantages: 1) Compared with the coal-based vertical furnace direct reduced iron process, it is more conducive to the use of high-volatile coal. Considering the carbon emissions in the coke production process and the price of coke or lignite, it can significantly reduce carbon emissions and the production cost of direct reduced iron.

[0036] 2) Compared with the rotary kiln direct iron reduction process in which the material is directly heated by electricity with internal carbon, it is not necessary to grind the coal and iron ore to less than 200 mesh and then mix them into a mixed shape. Sintered ore can be used to avoid partial combustion of coal during oxidative roasting. It is more conducive to the use of high-volatile coal, with low cost, low carbon emissions, and is more conducive to separating the ash brought in by the coal.

[0037] 3) Compared with the traditional blast furnace ironmaking process, the carbon emissions of the ironmaking process of the present invention can be greatly reduced by more than 65%.

[0038] 4) Compared with the coal-based vertical furnace direct reduction process in which the raw materials are directly heated by electricity, the problem of material compaction and furnace blockage is avoided.

[0039] 5) Compared with the existing coke oven gas or water gas-based vertical furnace direct reduction process, it is not necessary to add oxygen-enriched or oxygen to the incoming air to make it burn for reaction heat, nor is it necessary to preheat the raw gas at high temperature before it enters the furnace. The process and equipment are simplified, the safety is improved, the equipment investment is reduced, and the operating cost is reduced.

[0040] 6) Compared with the existing coke oven gas or water gas based direct reduction process, it does not require the previous gas generation process such as coking, coal gasification, and water electrolysis hydrogen production. It solves the gas source problem of the gas-based process. The process and equipment are simplified, the safety is improved, the equipment investment is reduced, and the operating cost is reduced.

[0041] 7) Compared with the existing direct reduction iron process using rotary kiln, it avoids the operation of blowing secondary air into the rotary kiln, reduces the nitrogen content in the tail gas, and improves the calorific value and availability of the tail gas. The value of tail gas recovery and recycling or direct use for combustion and power generation is improved.

[0042] 8) Compared with the blast furnace ironmaking process, for vanadium-titanium magnetite and ilmenite, the direct reduced iron obtained by the direct reduction iron process can easily separate iron and slag through smelting. The vanadium and titanium content in the slag is high, which is conducive to the subsequent utilization of vanadium and titanium.

[0043] In summary, the electric rotary kiln carbon-based direct iron reduction process of the present invention has low carbon emission, high safety, easy availability of raw materials, low investment, low operating cost, good reliability, high feasibility, and good technical and economic effects. DETAILED DESCRIPTION

[0044] The specific technical solution of the present invention is described below in conjunction with embodiments. Example 1

[0045] In this embodiment of the electric heating rotary kiln low carbon direct reduction iron process, the rotary kiln has a rotary tube length of 16m, an equivalent inner diameter of the furnace of 0.58m, a reduction section length of 6m, and a positive and negative pole of the heating power supply are respectively set at both ends. The preheating section is 5m long, the cooling section is 5m long, and the rotary tube of the rotary kiln has an inclination rate of 3%, and the feed end is higher than the discharge end. The total iron content of ordinary iron ore is 60~63%, which is an oxidized pellet after high temperature calcination. The pellet size is about 10mm and the bulk density is about 2300kg / m 3. The particle size of semi-coke particles is 1~10mm. 110kg semi-coke particles are added to each ton of oxidized pellets. After mixing, they enter the furnace from the feed end and are withdrawn from the furnace by gravity through the preheating section, reduction section and cooling section under the rotation of the rotary kiln. CO is used as the reducing gas instead of the circulating tail gas and introduced from the discharge section of the rotary kiln. The CO feed amount is 1350kg per ton of oxidized pellets. The maximum temperature of the reduction section is set to 1200℃. The temperature is measured by a k-division thermocouple, and the output power of the heating power supply is automatically controlled by the maximum temperature of the reduction section. As the rotary kiln rotates, the iron reduction process runs continuously and stably, and the material filling rate in the reduction section of the furnace is ~50%. The discharge speed is controlled so that the residence time of the pellet material in the furnace is about 10h. After withdrawing from the cooling section, the material can be directly sent to the subsequent melting process for slag iron separation or temporarily stored in the discharge tank. The outer wall of the discharge tank is water-cooled by the water-cooled jacket, and the reduction atmosphere system is withdrawn after nitrogen replacement. The metallization rate of iron in the discharged material is 97%, and the carbon content is ≤1%. The volume percentage of carbon dioxide in the tail gas is 25%. The tail gas can be recycled after dust removal and decarbonization. However, the process flow of this embodiment does not construct a device for removing carbon dioxide. Example 2

[0046] The electric heating rotary kiln direct reduction iron process in this embodiment uses vanadium-titanium magnetite as the iron ore raw material, and its total iron content is 53-55%, which is an oxidized pellet after high temperature calcination, with a pellet size of about 10 mm and a bulk density of about 2100 kg / m 3 . The particle size of lignite particles is 0~20mm. 90kg of lignite particles are added to each ton of oxidized pellets, and the lignite is sprayed from the discharge end of the furnace into the second half of the reduction section near the discharge end. Methanol gas is used as the reducing gas to enter the furnace, and the methanol flow rate is controlled according to 450kg methanol per ton of oxidized pellets. The rest is the same as Example 1. The metallization rate of iron in the discharged material is ~96%, and the carbon content is ≤3%. The daily output of metallized pellets is ~8 tons. It should be specially noted that, as in Example 1, in this embodiment, since there is no tail gas recovery and recycling device, methanol is used as the reducing gas to enter the kiln, and the tail gas is not recycled, it does not represent the actual reducing agent consumption and carbon emissions of the direct iron reduction process of the present invention.

Claims

1. An electric heating rotary kiln carbon-based direct iron reduction process, which uses solid carbon to reduce iron ore, characterized in that: The rotary kiln has an internal cavity that is nearly cylindrical or prismatic as a furnace, one end of the rotary kiln has a feed port and an exhaust gas outlet, and the other end has a discharge port and a reducing gas inlet, and the reducing gas is introduced into the rotary kiln from the inlet; the furnace is provided with a preheating section and a reducing section from the feed end to the discharge end; A heating power supply electrode is provided in the reduction section for supplying electricity to the conductive material in the section to heat the material; The iron ore contains iron oxides, which are one or more of iron oxide, common iron ore, ilmenite, vanadium-titanium magnetite, hematite, recycled iron-containing dust particles, and graded preselection, molding, pre-burning, and pre-reduction products of the above materials; the iron content of the iron ore is more than 40%; The solid carbon is one or more of coal, charcoal, coke, blue carbon, activated carbon, graphite, petroleum coke, asphalt, and solid organic matter; The reducing gas is one or more of hydrogen, CO, ammonia, water, carbon dioxide, gaseous organic matter, and volatile organic matter; After the iron ore and solid carbon (hereinafter referred to as materials) enter the furnace of the rotary kiln, they are piled up into a material bed layer inside the furnace; as the rotary kiln rotates, the materials move from the feed end to the discharge end by gravity, and move out of the furnace from the discharge port, and the materials in the furnace pass through the preheating section and the reduction section in sequence, and then obtain direct reduced iron; in the preheating section, the materials are preheated by the gas withdrawn from the reduction section and partially pre-reduced to obtain a certain conductivity, and then enter the reduction section, and the heating power supply electrode feeds current to the materials in the section, and the materials are heated by the resistance heat of the materials themselves; the highest temperature of the materials in the reduction section is not less than 850°C; Part or all of the solid carbon is fed into the rotary kiln in the form of additional carbon.

2. The electric heating rotary kiln carbon-based direct reduction iron process according to claim 1, characterized in that: The reducing gas contains water, and the water component is introduced into the electric heating rotary kiln at a position where the temperature of the furnace and / or the material of the electric heating rotary kiln is greater than or equal to 700°C.

3. The electric heating rotary kiln carbon-based direct iron reduction process according to claim 1, characterized in that: The reducing gas contains carbon dioxide, and the carbon dioxide component is introduced into the electric heating rotary kiln at a position where the temperature of the furnace and / or the material of the electric heating rotary kiln is greater than or equal to 700°C.

4. The electric heating rotary kiln carbon-based direct iron reduction process according to any one of claims 1 to 3, characterized in that: The gas after the reduction stage and / or preheating stage undergoes a water-gas shift reaction to convert part or all of the CO into hydrogen, and then undergoes a decarbonization treatment. The obtained hydrogen enters the electric rotary kiln as all or part of the reduction gas for recycling.

5. The electric heating rotary kiln carbon-based direct iron reduction process according to any one of claims 1 to 4, characterized in that: The reduction equivalent of the solid carbon and reducing gas entering the rotary kiln exceeds the equivalent required for the reduction reaction of the iron oxide in the iron ore in the electric heated rotary kiln, so that the obtained direct reduced iron has a carburization content of more than 1% by weight.

6. The electric heating rotary kiln carbon-based direct iron reduction process according to any one of claims 1 to 5, characterized in that: The reduction equivalent of the solid carbon and reducing gas entering the rotary kiln exceeds the equivalent required for the reduction reaction of the iron oxide in the iron ore in the rotary kiln, and there is also some unreacted residual carbon in the obtained direct reduced iron; the residual carbon accounts for more than 0.3% of the weight of the obtained material; the residual carbon is in the form of separate particles or powder or is retained in separate particles or powder remaining after the reaction of the solid carbon.

7. The electric heating rotary kiln carbon-based direct iron reduction process according to any one of claims 1 to 6, characterized in that: The rotary kiln is further provided with a cooling section at one end of the reduction section near the discharge end; the reducing gas except water and / or carbon dioxide enters the cooling section from the discharge end of the cooling section; the material enters the cooling section from the reduction section and exchanges heat with the reducing gas to preheat the gas and cool the material.

8. The electric heating rotary kiln carbon-based direct iron reduction process according to any one of claims 1 to 7, characterized in that: The maximum temperature of the reduction stage is controlled between 850 and 1300°C.

9. The electric heating rotary kiln carbon-based direct iron reduction process according to any one of claims 1 to 8, characterized in that: The filling rate of the material in the reduction section of the rotary kiln furnace is above 25%.

10. The electric heating rotary kiln carbon-based direct iron reduction process according to any one of claims 1 to 9, characterized in that: Preferably, the iron content in the iron ore is above 50%.