Carbon reduction ironmaking system and process based on three-stage reduction

Abstract

The invention belongs to the technical field of low-carbon ironmaking, and relates to a carbon-reduction ironmaking system and process based on three-stage reduction. The fluidized bed reactor is connected with a rotary kiln discharge port of the rotary kiln reactor; the electric smelting separation furnace is connected with a fluidized bed discharge port of the fluidized bed reactor; the dust removal device is connected with the gas outlet of the rotary kiln and the gas outlet of the electric smelting separation furnace and is used for treating dust in the flue gas; the dehydration device is connected with a gas outlet of the dust removal device and is used for removing moisture in the flue gas and forming circulating reducing gas; the heating device is connected with the dehydration device and is used for heating the circulating reducing gas; wherein the heating device is respectively connected with a fluidized bed gas inlet and an electric smelting separation furnace gas inlet, and a fluidized bed gas outlet is connected with the rotary kiln reactor. Through the series design of rotary kiln pre-reduction, fluidized bed reduction and electric smelting separation furnaces, the ironmaking efficiency is remarkably improved, and carbon emission is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-carbon ironmaking, and relates to a carbon-reducing ironmaking system and process based on three-stage reduction. Background Art

[0002] The iron and steel industry is a major energy consumer and CO2 emitter. Every step of the steel production process, from raw material preparation and sintering to coking and blast furnace ironmaking, consumes vast amounts of energy and produces significant amounts of CO2, making it a significant source of global CO2 emissions. With growing international attention to climate change and the gradual tightening of emission reduction policies worldwide, the iron and steel industry faces unprecedented pressure to reduce emissions.

[0003] my country has actively laid out its plans in the field of low-carbon ironmaking technology and vigorously promoted the research, development and application of related technologies. At present, a variety of low-carbon ironmaking technologies such as direct reduction technology, smelting reduction technology, and oxygen-enriched ironmaking technology have been explored and practiced to varying degrees. Among them, coal direct reduction technology, as an important low-carbon ironmaking technology, has attracted much attention. This technology uses coal as a reducing agent to directly reduce iron ore into metallic iron at a relatively low temperature (about 600°C). Compared with the traditional blast furnace ironmaking process using coke as the main reducing agent, coal direct reduction technology reduces the use of coke, thereby significantly reducing the large amount of carbon dioxide emissions generated by coke combustion and reduction reactions in the traditional blast furnace ironmaking process.

[0004] As an industrial equipment widely used in the ironmaking industry, the rotary kiln plays a key role in the production of direct reduced iron (DRI). It has the ability to process various types of iron ore, especially low-grade ores. Due to their complex composition and high impurity content, these ores are difficult to effectively utilize in blast furnaces. However, the rotary kiln can process these ores, achieving efficient resource utilization. The use of rotary kilns for coal-based direct reduction ironmaking offers advantages such as high resource utilization, low environmental pollution, and relatively low production costs. However, the solid materials produced by coal-based direct reduction in rotary kilns may not directly meet the requirements of subsequent industrial production in terms of composition and particle size, and further processing is required. Therefore, considering combining it with other equipment and processes can fully utilize the advantages of this technology and achieve more efficient and low-carbon ironmaking production. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a carbon-reducing ironmaking system and process based on three-stage reduction to solve the technical problems raised in the background technology.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A carbon reduction ironmaking system based on three-stage reduction, comprising:

[0008] Rotary kiln reactor for pre-reduction of iron ore;

[0009] A fluidized bed reactor connected to the rotary kiln discharge port of the rotary kiln reactor, used for deep reduction of the pre-reduced iron ore;

[0010] An electric smelting furnace is connected to the fluidized bed discharge port of the fluidized bed reactor and is used for final reduction of the deep-reduced iron ore and separation of iron slag;

[0011] The dust removal device is connected to the gas outlet of the rotary kiln and the gas outlet of the electric melting furnace to handle the dust in the flue gas;

[0012] Dehydration device, connected to the air outlet of the dust removal device, used to remove moisture from the flue gas and form circulating reducing gas;

[0013] a heating device connected to the dehydration device and used for heating the circulating reducing gas;

[0014] The heating device is respectively connected to the air inlet of the fluidized bed and the air inlet of the electric melting furnace, and the air outlet of the fluidized bed is connected to the rotary kiln reactor.

[0015] Furthermore, a decarbonization device is provided between the dehydration device and the heating device for decarbonizing the flue gas;

[0016] A hydrogen inlet is provided on the heating device to replenish hydrogen.

[0017] The capture agent used in the decarbonization device is a liquid or solid substance that can absorb CO2, including one or more mixtures of methanol, propylene carbonate, ethanolamine, organic amine solution, sodium hydroxide solution or solid sodium hydroxide, calcium oxide, etc. The dust content of the flue gas is ≤2mg / m3 by combining the dust removal device with the decarbonization device. 3 , CO2 removal efficiency ≥95%.

[0018] Furthermore, an air inlet is provided on the rotary kiln reactor, and the air inlet is arranged in the middle of the rotary kiln reactor.

[0019] Furthermore, it also includes:

[0020] The crushing device is arranged between the rotary kiln reactor and the fluidized bed reactor and is used for crushing the iron ore.

[0021] A carbon reduction ironmaking process based on three-stage reduction, using the above ironmaking system, specifically comprises the following steps:

[0022] Rotary kiln pre-reduction: Iron ore and coal are mixed and fed into a rotary kiln reactor. The flue gas discharged from the fluidized bed reactor is used to preheat and pre-reduce the mixed iron ore and coal. After the rotary kiln pre-reduction, the iron ore reduction conversion rate reaches 50%.

[0023] Fluidized bed reduction: The pre-reduced iron ore is transferred to a fluidized bed reactor for deep reduction with circulating reducing gas. After deep reduction in the fluidized bed reactor, the iron ore reduction conversion rate reaches 90%.

[0024] Electric smelting furnace reduction: The iron ore after deep reduction is transferred to the electric smelting furnace for final reduction and iron slag separation with the circulating reducing gas;

[0025] Flue gas circulation: The flue gas generated by the rotary kiln reactor and the electric melting furnace is recycled into the fluidized bed reactor and the electric melting furnace for use after dust removal, dehydration and heating treatment;

[0026] The molten iron produced by the ironmaking process of rotary kiln-fluidized bed-electric melting furnace is used for subsequent processes.

[0027] Furthermore, the operating temperature of the rotary kiln reactor is 900° C. to 1000° C., and the operating pressure is 0.1 MPa to 4 MPa;

[0028] The operating temperature of the fluidized bed reactor is 900°C to 1100°C, and the operating pressure is 0.1MPa to 4MPa;

[0029] The operating temperature of the electric melting furnace is 1350° C. to 1500° C., and the operating pressure is 0.1 MPa to 4 MPa.

[0030] Furthermore, the temperature at which the mixed iron ore and coal are preheated by the flue gas discharged from the fluidized bed reactor is 500-600°C.

[0031] Furthermore, the particle size of the iron ore fed into the rotary kiln reactor is 0.5 to 1.0 mm, wherein the ore smaller than 0.5 mm and larger than 1.0 mm does not exceed 5%;

[0032] The sulfur content of the coal is less than 1%, the moisture content is less than 5%, and the average particle size does not differ from that of the iron ore by more than 10%.

[0033] Furthermore, the operating gas velocity of the fluidized bed reactor is 1.2 to 2.0 times the minimum fluidization velocity of the pre-reduced iron ore.

[0034] Furthermore, a decarbonization device is provided between the dehydration device and the heating device, a hydrogen inlet is provided on the rotary kiln reactor, and a hydrogen inlet is provided on the heating device to replenish hydrogen;

[0035] The flue gas circulation is controlled according to the CO2 content in the circulating reducing gas formed after dehydration. When the CO2 content in the circulating reducing gas is less than 30%, the flue gas circulation is as follows: the flue gas generated by the rotary kiln reactor and the electric melting furnace is subjected to dust removal, dehydration and heating treatment by a dust removal device, a dehydration device and a heating device to form a circulating reducing gas, which is then circulated into the rotary kiln reactor, the fluidized bed reactor and the electric melting furnace for use.

[0036] When the CO2 content in the circulating reducing gas is ≥30%, the flue gas circulation is as follows: the flue gas generated by the rotary kiln reactor and the electric smelting furnace is subjected to dust removal, dehydration, decarburization and heating treatment by a dust removal device, a dehydration device, a decarbonization device and a heating device, and then circulated into the fluidized bed reactor and the electric smelting furnace for use;

[0037] When the gas flow rate of the circulating reducing gas after decarburization is lower than 1.3 times the minimum fluidizing gas flow rate of the fluidized bed reactor, hydrogen needs to be supplemented at the hydrogen inlet.

[0038] The beneficial effects of the present invention are:

[0039] 1. This technical solution utilizes a serial design of rotary kiln pre-reduction, fluidized bed reduction, and electric smelting furnaces to form a progressive, three-stage reduction and carbon reduction ironmaking system, significantly improving ironmaking efficiency and reducing carbon emissions. Pulverized coal is injected into the rotary kiln, with oxygen injected into the center, ensuring more complete fuel combustion and improving thermal efficiency, thereby reducing coal usage and lowering carbon emissions. The serial reduction units ensure full reduction of the iron ore in multiple stages, gradually increasing the metallization rate to 0-50%, 50-90%, and above 90-99%. Final reduction and iron-slag separation in the electric smelting furnace further shorten the ironmaking process and improve production efficiency. This optimized design not only saves energy but also lays the foundation for green ironmaking.

[0040] 2. Flue gas recycling is a core highlight of this technical solution. Flue gas generated by the rotary kiln reduction and electric smelting furnace reduction processes undergoes dust removal, dehydration, decarbonization, and heating before entering a circulation pipeline for use in the rotary kiln reactor, fluidized bed reactor, and electric smelting furnace reduction processes. This effectively improves the utilization rate of reducing gas and reduces the consumption of fresh reducing gas. Furthermore, the decarbonization device reduces the CO2 content in the flue gas, improving the quality of the circulating reducing gas. Combined with the hydrogen replenishment mechanism, the CO2 content in the reducing gas is maintained below 30%. This efficient circulation model reduces energy waste while enhancing the stability and flexibility of the system.

[0041] 3. This solution has achieved significant results in energy conservation and emission reduction. By optimizing fuel utilization and flue gas recirculation, the amount of pulverized coal required per ton of molten iron is significantly reduced, thereby lowering CO2 emissions. Furthermore, the synergistic effect of the series reduction unit and the electric smelting furnace not only improves the metallization rate of the iron ore, but also ensures high-quality molten iron. Compared with traditional processes, this technology shortens the ironmaking process and time, reduces production costs, and achieves a win-win situation in terms of efficiency and environmental protection, demonstrating the potential of modern ironmaking technology for green transformation.

[0042] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0044] Figure 1 Schematic diagram of the structure of a carbon reduction ironmaking system based on three-stage reduction in the present invention;

[0045] Figure 2 This is a schematic structural diagram of a carbon reduction ironmaking system based on three-stage reduction in Example 1;

[0046] Figure 3 This is a structural schematic diagram of a carbon reduction ironmaking system based on three-stage reduction in Example 2.

[0047] Figure markings: 1-rotary kiln reactor; 2-iron ore and coal powder inlet; 3-air inlet; 4-hydrogen inlet; 5-rotary kiln discharge port; 6-crushing device; 7-crushing device discharge port; 8-fluidized bed reactor; 9-fluidized bed discharge port; 10-fluidized bed air inlet; 11-fluidized bed air outlet; 12-electric smelting furnace air inlet; 13-electric smelting furnace; 14-electric smelting furnace air outlet; 15-electric smelting furnace discharge port; 16-heating device; 17-rotary kiln air outlet; 18-dust removal device; 19-dust removal device air outlet; 20-dehydration device; 21-dehydration device air outlet; 22-decarbonization device; 23-decarbonization device air outlet. DETAILED DESCRIPTION

[0048] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0049] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0050] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0051] See also Figure 1 , a carbon-reducing ironmaking system based on three-stage reduction, including:

[0052] The rotary kiln reactor 1 is used for pre-reduction of iron ore and is provided with an iron ore and coal powder inlet 2 and an air inlet 3;

[0053] The fluidized bed reactor 8 is connected to the rotary kiln discharge port 5 of the rotary kiln reactor 1 and is used for deep reduction of the pre-reduced iron ore;

[0054] The electric smelting furnace 13 is connected to the fluidized bed discharge port 9 of the fluidized bed reactor 8 and is used for final reduction of the deep-reduced iron ore and separation of iron slag;

[0055] The dust removal device 18 is connected to the rotary kiln outlet 17 and the electric melting furnace outlet 14 to process dust in the flue gas;

[0056] The dehydration device 20 is connected to the dust removal device outlet 19 and is used to remove moisture from the flue gas and form a circulating reducing gas;

[0057] A heating device 16 connected to the dehydration device 20 for heating the circulating reducing gas;

[0058] The heating device 16 is connected to the fluidized bed air inlet 10 and the electric smelting furnace air inlet 12 respectively, and the fluidized bed air outlet 11 is connected to the rotary kiln reactor 1 .

[0059] Furthermore, a decarbonization device is provided between the dehydration device 20 and the heating device 16 for decarbonizing the flue gas; and a hydrogen inlet 4 is provided on the heating device 16 for replenishing hydrogen.

[0060] Furthermore, it also includes: a crushing device 6, arranged between the rotary kiln reactor 1 and the fluidized bed reactor 8, for crushing iron ore.

[0061] The present invention also provides a carbon reduction ironmaking process based on three-stage reduction, which uses the above ironmaking system and specifically includes the following steps:

[0062] Rotary kiln pre-reduction: The iron ore and coal are mixed and fed into the rotary kiln reactor 1. The flue gas discharged from the fluidized bed reactor 8 is used to preheat and pre-reduce the mixed iron ore and coal respectively;

[0063] Fluidized bed reduction: The pre-reduced iron ore is transferred to the fluidized bed reactor 8 and subjected to deep reduction with the circulating reducing gas;

[0064] Electric smelting furnace reduction: The iron ore after deep reduction is transferred to the electric smelting furnace 13 for final reduction and iron slag separation with the circulating reducing gas;

[0065] Flue gas circulation: The flue gas generated by the rotary kiln reactor 1 and the electric melting furnace 13 is circulated into the fluidized bed reactor 8 and the electric melting furnace 13 for use after dust removal, dehydration and heating treatment.

[0066] Furthermore, the operating temperature of the rotary kiln reactor 1 is 900° C. to 1000° C., and the operating pressure is 0.1 MPa to 4 MPa;

[0067] The operating temperature of the fluidized bed reactor 8 is 900°C to 1100°C, and the operating pressure is 0.1MPa to 4MPa;

[0068] The operating temperature of the electric melting furnace 13 is 1350° C. to 1500° C., and the operating pressure is 0.1 MPa to 4 MPa.

[0069] Furthermore, the temperature at which the mixed iron ore and coal are preheated by the flue gas discharged from the fluidized bed reactor 8 is 500-600°C.

[0070] Furthermore, the particle size of the iron ore fed into the rotary kiln reactor 1 is 0.5 to 1.0 mm, wherein the ore smaller than 0.5 mm and larger than 1.0 mm does not exceed 5%;

[0071] The sulfur content of the coal is less than 1%, the moisture content is less than 5%, and the average particle size does not differ from that of the iron ore by more than 10%.

[0072] Furthermore, the operating gas velocity of the fluidized bed reactor 8 is 1.2 to 2.0 times the minimum fluidization velocity of the pre-reduced iron ore.

[0073] Furthermore, the flue gas circulation is controlled according to the CO2 content in the circulating reducing gas formed after dehydration. When the CO2 content in the circulating reducing gas is less than 30%, the flue gas circulation is as follows: the flue gas generated by the rotary kiln reactor 1 and the electric smelting furnace 13 is subjected to dust removal, dehydration, and heating treatment by the dust removal device 18, the dehydration device 20, and the heating device 16 to form a circulating reducing gas, which is then circulated into the fluidized bed reactor 8 and the electric smelting furnace 13 for use;

[0074] When the CO2 content in the circulating reducing gas is ≥30%, the flue gas circulation is as follows: the flue gas generated by the rotary kiln reactor 1 and the electric melting furnace 13 is subjected to dust removal, dehydration, decarbonization, and heating treatment by the dust removal device 18, the dehydration device 20, the decarbonization device 22, and the heating device 16, and then circulated into the fluidized bed reactor 8 and the electric melting furnace 13 for use;

[0075] When the gas flow rate of the circulating reducing gas after decarburization is lower than 1.3 times of the minimum fluidizing gas flow rate of the fluidized bed reactor 8 , hydrogen needs to be supplemented at the hydrogen inlet 4 .

[0076] Taking the production process of 500,000 tons of molten iron per year as an example, the present invention is further explained by simulating the physical and thermal balances of the process equipment and combining different treatment scenarios of the circulating gas.

[0077] Tables 1 to 3 show the calculation parameters for the iron ore grade, pulverized coal composition, and minimum fluidizing gas velocity of the fluidized bed, respectively. The reduction degree is calculated by the iron ore grade, the carburizing amount and gas composition are calculated by the composition of the injected coal, and the minimum fluidizing velocity of the solid particles is calculated by calculating the density and viscosity of the mixed gas to determine the required gas volume for the fluidized bed.

[0078] Table 1 Iron ore grade

[0079] FeO <![CDATA[Fe2O3]]> TFe other 7.24％ 73.78％ 57.28％ 18.98％

[0080] Table 2 Composition of pulverized coal injection

[0081]

[0082] Table 3 Calculation parameters of minimum fluidizing gas velocity in fluidized bed (900℃)

[0083] Mixed gas density Viscosity of mixed gas Solid density Particle size Minimum fluidizing gas velocity 0.022g / l <![CDATA[21.0*10^ -6 Step]]> 7251.8g / l 0.0005m 0.500m / s 0.022g / l <![CDATA[21.0*10^ -6 Step]]> 7251.8g / l 0.0008m 1.95m / s 0.022g / l <![CDATA[21.0*10^ -6 Step]]> 7251.8g / l 0.001m 1.27m / s

[0084] Example 1: A carbon reduction ironmaking system based on three-stage reduction

[0085] System composition: Figure 2 As shown, this embodiment provides a carbon reduction ironmaking system based on three-stage reduction, comprising:

[0086] Rotary kiln reactor 1: used for pre-reduction of iron ore;

[0087] Fluidized bed reactor 8: connected to the rotary kiln reactor 1 through the rotary kiln discharge port 5, used for deep reduction of pre-reduced iron ore;

[0088] Electric smelting furnace 13: connected to fluidized bed reactor 8 through fluidized bed discharge port 9, used for final reduction of deep-reduced iron ore and separation of iron slag;

[0089] A crushing device 6 is arranged between the rotary kiln reactor 1 and the fluidized bed reactor 8 and is used to crush the iron ore;

[0090] Dust removal device 18: connected to the rotary kiln outlet 17 and the electric melting furnace outlet 14, used to remove dust in the flue gas;

[0091] Dehydration device 20: connected to the dust removal device outlet 19, used to remove moisture from the flue gas to form circulating reducing gas;

[0092] Heating device 16: connected to the dehydration device 20, used to heat the circulating reducing gas.

[0093] The output end of heating device 16 is connected to fluidized bed air inlet 10 and electric smelting furnace air inlet 12, respectively. Fluidized bed air outlet 11 is connected to the rotary kiln air inlet of rotary kiln reactor 1, forming a flue gas circulation loop. The reduction utilization rate of CO and H2 in the circulating reducing gas is calculated as 20%.

[0094] Process

[0095] The ironmaking process of this embodiment includes the following steps:

[0096] Rotary Kiln Pre-Reduction: Iron ore (particle size 0.5mm, with no more than 5% of ore smaller than 0.5mm and larger than 1.0mm) is mixed with coal (sulfur content less than 1% and moisture content less than 5%) and fed into the rotary kiln reactor 1 through the iron ore and coal inlet 2. The mixture is preheated to 600°C using high-temperature flue gas discharged from the fluidized bed reactor 8 through the fluidized bed outlet 11. Air is then introduced through the air inlet 3. Pre-reduction then takes place at 900°C, partially converting the iron oxide in the iron ore into metallic iron, achieving a reduction conversion rate of 50%.

[0097] Fluidized bed reduction: The pre-reduced iron ore enters the fluidized bed reactor 8 through the rotary kiln discharge port 5 and undergoes deep reduction with the heated circulating reducing gas. The operating gas velocity is 1.2 times the minimum fluidization velocity of the pre-reduced iron ore, and the reduction conversion rate is increased to 90%.

[0098] Electric smelting furnace reduction: After deep reduction, the iron ore enters the electric smelting furnace 13 through the fluidized bed discharge port 9 and undergoes final reduction with the circulating reducing gas. The reduction conversion rate is increased to 99%. At the same time, the separation of molten iron and slag is completed, and liquid molten iron is produced and discharged through the electric smelting furnace discharge port 15.

[0099] Flue gas circulation: Flue gas generated by the rotary kiln reactor 1 and the electric melting furnace 13 is discharged from the rotary kiln outlet 17 and the electric melting furnace outlet 14 respectively. After being treated by the dust removal device 18, the dust content is reduced to 2mg / m 3 After that, the water is removed by the dehydration device 20 to form the circulating reducing gas. The circulating reducing gas is heated to 900°C by the heating device 16 and then fed into the fluidized bed reactor 8 and the electric melting furnace 13 respectively.

[0100] Operating parameters

[0101] Take the production process of 500,000 tons of molten iron per year as an example:

[0102] Iron ore input: 77,000kg / h

[0103] Pulverized coal input: 17,000kg / h

[0104] Circulating reducing gas flow rate: 1.08*10^ 5 m 3 / h (composition: 17.4% CO, 78.0% H2, 0.3% N2, 4.3% CO2)

[0105] Circulating reducing gas flow rate entering the fluidized bed reactor: 9.30*10^ 4 m 3 / h, which is 1.2 times the minimum fluidizing gas flow rate. The gas composition is consistent with the circulating reducing gas. The fluidized bed reactor reduces the iron ore from 50% to 90%. The gas composition after the fluidized bed reactor is 13.3% CO, 71.0% H2, 0.3% N2, 8.4% CO2, and 7.0% H2O.

[0106] Circulating reducing gas flow rate entering the electric melting furnace: 1.52*10^ 4 m 3 / h, the gas composition is consistent with the circulating reducing gas composition; the electric smelting furnace reduces the iron ore from 90% to 99%, and the gas composition at the outlet of the electric smelting furnace is 13.9% CO, 66.3% H2, 0.3% N2, 7.8% CO2, and 11.7% H2O;

[0107] The top gas of the fluidized bed is discharged to the rotary kiln reactor through the fluidized bed outlet 11, preheating 77000.0 kg / h of iron ore and 17000 kg / h of pulverized coal from 25°C to 600°C, and considering 5% heat loss, it is calculated that the heat consumption is 1*10^ 7 KJ / h, it needs to consume 8.0% of the top gas of the fluidized bed reactor. Therefore, after deducting the preheating consumption, the cumulative air intake of the rotary kiln reactor is 1.19*10^ 5 m 3 / h (excluding the air entering the air inlet), the composition of the mixed coal pulverized matter after volatilization is 30.2% CO, 57.4% H2, 0.5% N2, 6.6% CO2, 5.4% H2O. After the iron ore fines are reduced to 50%, the gas composition at the rotary kiln outlet is 21.7% CO, 48.0% H2, 0.5% N2, 15.0% CO2, 14.8% H2O;

[0108] The tail gas from the electric melting furnace is mixed with the tail gas from the rotary kiln reactor and then passes through the dust removal device, dehydration device, and heating device before entering the circulating gas pipeline.

[0109] Table 4 Heat calculation data table

[0110]

[0111] Table 4 shows the specific heat capacity of iron oxide and ferrous oxide in iron ore powder and the calorific value of carbon monoxide and hydrogen, which is used to calculate the heat required to be provided by the mixed gas for preheating iron ore powder and coal powder.

[0112] By limiting the particle size of iron ore powder and coal powder, the minimum fluidizing gas flow rate of the fluidized bed reactor 8 is obtained to determine the flow rate of the circulating reducing gas, and the amount of hydrogen required to be supplemented after decarbonization can be given. Through the reduction of 0-50% in the rotary kiln, 50-90% in the fluidized bed, and 90-99% in the electric smelting furnace, the coal powder consumed in the reduction, hydrogen, and carbon dioxide emission content can be calculated. A simple calculation shows that, after deducting the power consumption of the rotary kiln, fluidized bed, and electric smelting furnace for heating and the heat loss of the pipeline, a carbon reduction ironmaking process based on three-stage reduction in this embodiment consumes 286.7 kg / t of coal powder and 248.7 m3 of H2 to produce one ton of iron. 3 / t, CO2 emissions per ton of iron are 580kg / t. Conventional blast furnaces emit 1800kg / t to 2000kg / t of CO2 per ton of iron. This process can achieve the goal of significantly reducing carbon emissions by up to 60-70%.

[0113] Example 2: A carbon reduction ironmaking system based on three-stage reduction, with an additional decarbonization-hydrogenation step

[0114] like Figure 3As shown, the difference from Example 1 is that after the circulating reducing gas is dedusted and dehydrated, if the carbon dioxide content exceeds 30%, it needs to undergo an additional decarbonization process. If the total gas flow rate after decarbonization is lower than 1.3 times the minimum fluidizing gas flow rate of the fluidized bed, additional hydrogen needs to be added through the hydrogen inlet 4 to replenish the total gas flow rate of the circulating reducing gas after decarbonization to more than 1.3 times the minimum fluidizing gas flow rate of the fluidized bed reactor 8 (specifically, a hydrogen blowing device can be connected at the hydrogen inlet 4). Other systems and processing methods, as well as raw fuel conditions are exactly the same as in Example 1 and will not be repeated. Only the differences are described.

[0115] Gas flow rate after dehydration and dust removal in the circulating gas pipeline is 1.37*10^ 5 m 3 / h, of which the CO2 content is 40.6%, and it needs to go through a decarbonization process. The gas flow rate after decarbonization is 8.41*10^ 4 m 3 / h, which is lower than 1.3 times of the minimum fluidizing gas flow rate, it is necessary to replenish hydrogen at the hydrogen inlet 1 of the heating device 16. The total gas flow rate after replenishment is 1.16*10^ 5 m 3 / h, the gas composition is 33.1% CO, 63.5% H2, 1.0% N2, 2.4% CO2. The gas flow rate into the fluidized bed reactor is 1.01*10^ 5 m 3 / h (1.3 times the minimum fluidizing gas flow rate), reducing the iron ore from 50% to 90%; the gas flow rate entering the electric melting furnace is 1.50*10^ 4 m 3 / h, reducing the iron ore from 90% to 99%; the top gas of the fluidized bed enters the rotary kiln reactor to preheat and pre-reduce the iron ore and coal powder.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A carbon reduction ironmaking system based on three-stage reduction, characterized in that: include: A rotary kiln reactor (1) for pre-reducing iron ore; A fluidized bed reactor (8) is connected to the rotary kiln discharge port (5) of the rotary kiln reactor (1) and is used for deep reduction of the pre-reduced iron ore; An electric smelting furnace (13) is connected to the fluidized bed discharge port (9) of the fluidized bed reactor (8) and is used for final reduction of the deep-reduced iron ore and separation of iron slag; A dust removal device (18) is connected to the rotary kiln gas outlet (17) and the electric melting furnace gas outlet (14) and is used to treat dust in the flue gas; A dehydration device (20) connected to the dust removal device outlet (19) is used to remove moisture from the flue gas and form a circulating reducing gas; a heating device (16), connected to the dehydration device (20), for heating the circulating reducing gas; The heating device (16) is respectively connected to the fluidized bed air inlet (10) and the electric melting furnace air inlet (12), and the fluidized bed air outlet (11) is connected to the rotary kiln reactor (1).

2. The ironmaking system according to claim 1, characterized in that A decarbonization device (22) is further provided between the dehydration device (20) and the heating device (16) for decarbonizing the flue gas; A hydrogen inlet (4) is provided on the heating device (16) to replenish hydrogen.

3. The ironmaking system according to claim 1, characterized in that An air inlet (3) is also provided on the rotary kiln reactor (1), and the air inlet (3) is arranged in the middle of the rotary kiln reactor.

4. The ironmaking system according to claim 1, characterized in that Also includes: A crushing device (6) is arranged between the rotary kiln reactor (1) and the fluidized bed reactor (8) and is used for crushing iron ore.

5. A carbon reduction ironmaking process based on three-stage reduction, characterized in that: The ironmaking system according to any one of claims 1 to 4 comprises the following steps: Rotary kiln pre-reduction: iron ore and coal are mixed and fed into a rotary kiln reactor (1), and the mixed iron ore and coal are preheated and pre-reduced respectively using the flue gas discharged from the fluidized bed reactor (8); Fluidized bed reduction: The pre-reduced iron ore is transferred to a fluidized bed reactor (8) and subjected to deep reduction with circulating reducing gas; Electric smelting furnace reduction: The deep-reduced iron ore is transferred to the electric smelting furnace (13) for final reduction and iron slag separation with the circulating reducing gas; Flue gas circulation: The flue gas generated by the rotary kiln reactor (1) and the electric melting furnace (13) is subjected to dust removal, dehydration and heating treatment by a dust removal device (18), a dehydration device (20) and a heating device (16) to form a circulating reducing gas, which is then circulated into the fluidized bed reactor (8) and the electric melting furnace (13) for use.

6. The ironmaking process according to claim 1, characterized in that The operating temperature of the rotary kiln reactor (1) is 900° C. to 1000° C., and the operating pressure is 0.1 MPa to 4 MPa; The operating temperature of the fluidized bed reactor (8) is 900° C. to 1100° C., and the operating pressure is 0.1 MPa to 4 MPa; The operating temperature of the electric melting furnace (13) is 1350°C to 1500°C, and the operating pressure is 0.1MPa to 4MPa.

7. The ironmaking process according to claim 1, characterized in that: The temperature at which the mixed iron ore and coal are preheated by the flue gas discharged from the fluidized bed reactor (8) is 500-600°C.

8. The ironmaking process according to claim 1, characterized in that The particle size of the iron ore fed into the rotary kiln reactor (1) is 0.5-1.0 mm, wherein the ore smaller than 0.5 mm and larger than 1.0 mm does not exceed 5%; The sulfur content of the coal is less than 1%, the moisture content is less than 5%, and the average particle size does not differ from that of the iron ore by more than 10%.

9. The ironmaking process according to claim 1, characterized in that: The operating gas velocity of the fluidized bed reactor (8) is 1.2 to 2.0 times the minimum fluidization velocity of the pre-reduced iron ore.

10. The ironmaking process according to claim 1, characterized in that: A decarbonization device (22) is further provided between the dehydration device (20) and the heating device (16), and a hydrogen inlet (4) is further provided on the rotary kiln reactor (1); and a hydrogen inlet (4) is provided on the heating device (16) to replenish hydrogen; The flue gas circulation is controlled according to the CO2 content in the circulating reducing gas formed after dehydration. When the CO2 content in the circulating reducing gas is less than 30%, the flue gas circulation is as follows: the flue gas generated by the rotary kiln reactor (1) and the electric melting furnace (13) is subjected to dust removal, dehydration and heating treatment by a dust removal device (18), a dehydration device (20) and a heating device (16) to form a circulating reducing gas, which is then circulated into the fluidized bed reactor (8) and the electric melting furnace (13) for use; When the CO2 content in the circulating reducing gas is ≥30%, the flue gas circulation is as follows: the flue gas generated by the rotary kiln reactor (1) and the electric melting furnace (13) is subjected to dust removal, dehydration, decarbonization, and heating treatment by a dust removal device (18), a dehydration device (20), a decarbonization device (22), and a heating device (16), and then circulated into the fluidized bed reactor (8) and the electric melting furnace (13) for use; When the gas flow rate of the circulating reducing gas after decarburization is lower than 1.3 times the minimum fluidizing gas flow rate of the fluidized bed reactor (8), hydrogen needs to be supplemented at the hydrogen inlet (4).

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