Method and system for directly reducing iron by blast furnace gas and simultaneously converting and utilizing CO2 in situ

Abstract

The invention belongs to the technical field of iron and steel smelting and blast furnace gas recycling, and particularly relates to a method and a system for directly reducing iron by blast furnace gas and simultaneously converting and utilizing CO2 in situ. The existing blast furnace gas utilization way has the defects and the problem of insufficient gas source in the gas-based direct reduction iron process is solved. According to the method, CO in blast furnace gas and iron ore powder are subjected to a direct reduction reaction in an iron ore reduction reactor, and CO is converted into CO2 during iron making; after gas-solid separation, solid is subjected to magnetic separation to extract iron, unreacted iron ore powder enters a fine reduction reactor to be fully reduced, and conversion and utilization of the iron ore powder are improved; the gas subjected to gas-solid separation enters a carbon sequestration / carbon release reactor, CO2 in the gas is captured and immobilized during carbon sequestration, and reducing gas is introduced during carbon release to convert the immobilized CO2 into carbon-rich gas with high economic value, such as CO. And the development of low-carbon ironmaking and green metallurgy technologies is facilitated while the source of the raw material gas is optimized.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting and blast furnace gas recovery and utilization, and in particular relates to a method and system for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ. Background Art

[0002] China's steel industry produces about 1 billion tons of crude steel annually, and CO2 emissions during the production process account for 16% of the country's carbon emissions. One of the sources of CO2 is blast furnace gas, which is a byproduct of blast furnace ironmaking. The annual output of blast furnace gas in China is about 1.1 trillion Nm 3 The main components of blast furnace gas are N2 (50% to 55%), CO (20% to 28%), CO2 (17% to 25%), and H2 (1% to 3%). It has a low calorific value and low utilization efficiency. It is mostly burned directly, causing serious waste of resources and environmental pollution.

[0003] Blast furnace gas contains a high level of CO, and CO has a high utilization value. In the metallurgical field, CO can be used as a reducing agent for metal smelting and preparation; in the chemical industry, CO is a raw material for the production of various high-value products; in the medical field, CO can treat pneumonia, cardiovascular and other diseases. At present, CO is mainly produced from blast furnace gas through pressure swing adsorption, which is costly and energy-intensive, and only the CO of the gas itself is obtained, and the CO2 in it is not utilized. If CO2 is converted into CO in situ, it can not only reduce pollution to the environment, but also increase the output of CO, and achieve carbon negative emissions of blast furnace gas.

[0004] Under the "dual carbon" strategy of "carbon peak" and "carbon neutrality", the blast furnace ironmaking process faces unprecedented environmental constraints, and green transformation is imperative. The direct reduction iron process has received more and more attention as a technology to replace blast furnace smelting. In particular, the gas-based direct reduction iron process is a non-blast furnace ironmaking process that uses reducing gas to directly reduce iron oxide in iron ore to iron. At present, the reducing gas is mainly H2 / CO mixed gas, which is produced by reforming raw materials such as natural gas, coal gas, and coke oven gas. In addition, H2 / CO mixed gas has a wide range of uses. In addition to being used in gas-based metallurgy and gas energy fuels, it is also mainly used in the chemical industry to convert and synthesize high-value-added fine chemicals, such as methanol, ethylene, propylene, dimethyl ether, etc. However, the current lack of H2 / CO mixed gas sources has severely restricted the development of technologies such as direct reduction ironmaking and fine chemicals. Summary of the invention

[0005] In the context of "dual carbon", in response to the defects of existing blast furnace gas utilization methods and the problem of insufficient gas source in the gas-based direct iron reduction process, the present invention provides a method and system for directly reducing iron using blast furnace gas and simultaneously capturing CO2 for in-situ conversion and utilization. The purpose is to make full use of blast furnace gas and convert the CO2 therein into carbon-containing gases with high economic value such as CO, thereby generating added value while reducing carbon emissions.

[0006] The method of directly reducing iron with blast furnace gas and simultaneously capturing CO2 for in-situ conversion to produce carbon-containing gases with high economic value such as CO, according to the present invention, comprises the following contents:

[0007] Direct iron reduction reaction is carried out with blast furnace gas and iron ore powder as raw materials to obtain iron-containing solid and reaction gas; the reaction gas mainly contains CO2 and N2, and after the carbon fixation / carbon release reaction, the CO2 is converted into a generated gas containing carbon-rich gas in situ, and high-purity N2 is separated and recovered for other uses;

[0008] The carbon-rich gas includes CO gas, H2 / CO mixed gas or CH4 gas;

[0009] The blast furnace gas includes CO and CO2, and the main gas components and contents of the blast furnace gas are as follows: CO: 20% to 28%, CO2: 17% to 25%, N2: 50% to 55%, H2: 1% to 3%;

[0010] The CO2 in the reaction gas includes the original CO2 in the blast furnace gas and the CO2 converted from the CO in the blast furnace gas through the direct iron reduction reaction.

[0011] The carbon fixation / carbon release reaction includes a carbon fixation reaction and a carbon release reaction, wherein CO2 is first adsorbed and fixed by the filling material through the carbon fixation reaction, and then the CO2 fixed on the filling material is converted into carbon-rich gas in situ through the carbon release reaction under a reducing gas environment and released from the filling material;

[0012] The reducing gas includes natural gas, hydrogen, or industrial gas containing CH4 and H2;

[0013] The filling material includes a CO2 absorbent (including Ca-based, Mg-based and other absorbents, such as Ni-CaO or Cu-MgO adsorption-catalysis dual-functional materials) and a catalyst (such as Ni, Cu and other transition elements or metal catalysts), which can adsorb CO2 and convert it into carbon-rich gas, and N2 is not adsorbed to achieve separation and purification; according to the different target products after CO2 reduction, the type of external reducing gas can be flexibly selected, and the reaction temperature and the catalyst used can be adjusted accordingly to obtain different carbon-rich gases; for example, when the reducing gas is CH4, the carbon-rich gas is mainly a CO / H2 mixed gas; when the reducing gas is hydrogen, if the reaction temperature is about 500°C, the carbon-rich gas is mainly CH4; if the reaction temperature is about 700°C, the carbon-rich gas is mainly CO.

[0014] The temperature of the direct reduction iron reaction is 800℃~900℃, and the main reaction involved is: Fe2O3+3CO=2Fe+3CO2.

[0015] The iron-containing solid is magnetically separated into iron and unreduced iron ore powder, and carbon-rich gas is introduced into the unreduced iron ore powder for fine reduction reaction, so that the unreduced iron ore powder is further reduced to iron, and the temperature of the fine reduction reaction is 800°C to 900°C.

[0016] The system used for the above-mentioned direct reduction of iron with blast furnace gas and simultaneous capture of CO2 for in-situ conversion to produce carbon-containing gases with high economic value such as CO is as follows:

[0017] The system mainly includes a feeding device, an iron ore reduction reactor, a gas-solid separator, two sets of carbon fixation / release reactors, a gas storage tank, a fine reduction reactor, etc.

[0018] The feed inlet of the iron ore reduction reactor is connected to the feeding device, and the discharge port is connected to the gas-solid separator; the two groups of carbon fixation / carbon release reactors are respectively connected to the separation gas reversing valve, the reducing gas reversing valve, the generated gas control valve, and the tail gas discharge valve; the gas outlet of the gas-solid separator is respectively connected to the two groups of carbon fixation / carbon release reactors through the separation gas reversing valve, and the external reducing gas is respectively connected to the two groups of carbon fixation / carbon release reactors through the reducing gas reversing valve, and the generated gas outlets of the two groups of carbon fixation / carbon release reactors are respectively connected to the gas storage tank and the fine reduction reactor through the generated gas control valve and the diverter valve in turn; the solid discharge port of the gas-solid separator is connected to the fine reduction reactor through a magnetic separation and conveying device;

[0019] When the separation gas reversing valve interface connected to the carbon fixation / carbon release reactor is opened, the exhaust gas emission valve connected to the group of carbon fixation / carbon release reactors is opened, the reducing gas reversing valve is closed, and the generated gas control valve is closed; when the separation gas reversing valve interface connected to the carbon fixation / carbon release reactor is closed, the exhaust gas emission valve connected to the group of carbon fixation / carbon release reactors is closed, the reducing gas reversing valve interface is opened, and the generated gas control valve is opened.

[0020] The method for implementing the direct reduction of iron by blast furnace gas and the simultaneous capture of CO2 for in-situ conversion and utilization (i.e., the method for using the system) of the present invention is as follows:

[0021] (1) Blast furnace gas is introduced into an iron ore reduction reactor, and iron ore powder is introduced into the iron ore reduction reactor through a feeding device, and the temperature in the reactor is maintained between 800° C. and 900° C. to perform a direct iron reduction reaction; iron-containing solids and reaction gas are obtained; the reaction gas is mainly N2 and CO2, and the reaction gas carries the iron-containing solids into a gas-solid separator;

[0022] (2) The reaction gas carrying iron-containing solids is separated into gas and solids in a gas-solid separator. The iron-containing solids after gas-solid separation are subjected to magnetic separation for iron extraction, and the tailings powder discarded by magnetic separation enters the fine reduction reactor; the reaction gas after gas-solid separation enters the carbon fixation / release reactor for carbon fixation / release reaction, CO2 is converted into carbon-rich gas, and N2 is discharged and captured for other uses;

[0023] (3) A portion of the generated carbon-rich gas is passed into a gas storage tank for storage, and the other portion is passed into a fine reduction reactor to undergo a fine reduction reaction with the magnetic separation tailings powder, so that the unreduced magnetic separation tailings powder entering the fine reduction reactor is fully reduced to iron, and the fine reduction reaction temperature is 800°C to 900°C.

[0024] The carbon fixation / carbon release reaction in step (2) includes a carbon fixation reaction and a carbon release reaction, which are carried out in a fixed bed carbon fixation / carbon release reactor, wherein a filling material is present in the reactor bed, and two groups of carbon fixation / carbon release reactors work alternately; CO2 is first adsorbed and fixed by the filling material through a carbon fixation reaction, and then the CO2 fixed on the filling material is converted into a carbon-rich gas in situ through a carbon release reaction under a reducing gas environment and released from the filling material;

[0025] During the carbon fixation reaction, the carbon fixation reaction temperature is 400℃~500℃, and the CO2 in the reaction gas is absorbed and fixed by the filling material, and other gases are separated and discharged; the filling material is a mixture of a CO2 absorbent and a catalyst that promotes the conversion of CO2 into carbon-rich gas in a certain proportion, or a dual-functional material that can adsorb CO2 and simultaneously convert CO2 into carbon-rich gas.

[0026] Preferably, the CO2 absorbent can be selected from Ca-based (CaO+CO2=CaCO3), Mg-based and other materials; preferably, the catalyst can be selected from transition elements or metal catalysts such as Ni and Cu.

[0027] During the carbon release reaction, a reducing gas is introduced into the carbon fixation / release reactor to convert the CO2 absorbed by the carbon fixation reaction into a carbon-rich gas in situ; the reducing gas includes natural gas, hydrogen, or industrial gas containing CH4 and H2; the carbon-rich gas includes CO gas, H2 / CO mixed gas, or CH4 gas;

[0028] The carbon release reaction described in step (2) can flexibly select the type of external reducing gas, such as natural gas, hydrogen, industrial gas (such as coke oven gas), etc., according to the different target products after CO2 reduction, and adjust the reaction temperature and the catalyst used accordingly to obtain different target products, such as CO, H2 / CO synthesis gas, CH4, etc.; for example: when the external reducing gas is CH4, the carbon-rich gas is mainly H2 / CO mixed gas, and the main reaction of the carbon release reaction is CaCO3+CH4=CaO+2CO+2H2; when the external reducing gas is H2, by adjusting the reaction temperature, the carbon-rich gas is mainly CO gas or CH4 gas, and the main reactions of the carbon release reaction are CaCO3+H2=CaO+CO+H2O or CaCO3+4H2=CaO+CH4+2H2O, respectively.

[0029] Step (2) includes the following specific contents: the reaction gas after gas-solid separation enters one group of carbon fixation / carbon release reactors for carbon fixation reaction, CO2 is adsorbed and fixed in the filling material, and other gases such as N2 are discharged while carbon is fixed. After sufficient carbon fixation, the reaction gas is stopped from being introduced into the group of carbon fixation / carbon release reactors, and an external reducing gas is introduced into the group of carbon fixation / carbon release reactors, and a carbon release reaction occurs to convert the CO2 fixed on the filling material into a carbon-rich gas in situ and release it from the filling material, thereby obtaining a carbon-containing gas with high economic value such as CO, and at the same time achieving regeneration of the CO2 filling material (absorbent); after the carbon release reaction is completed, the reducing gas is stopped from being introduced into the group of carbon fixation / carbon release reactors, and the reaction gas is introduced into the group of carbon fixation / carbon release reactors to undergo a carbon fixation reaction with the regenerated filling material;

[0030] While reducing gas is introduced into the first group of carbon fixation / release reactors for carbon release reaction, the reaction gas (mainly N2 and CO2) after gas-solid separation is switched to the second group of carbon fixation / release reactors for carbon capture through adjusting valves to cause carbon fixation reaction. After sufficient carbon fixation, external reducing gas is introduced into the second group of reactors for carbon release reaction; while the second group of reactors is undergoing carbon release reaction, the reaction gas after gas-solid separation is allowed to enter the first group of reactors for carbon fixation reaction through adjusting valves; this cycle is repeated so that carbon fixation reaction and carbon release reaction are carried out alternately in the two groups of carbon fixation / release reactors.

[0031] Compared with the prior art, the characteristics and beneficial effects of the present invention are:

[0032] The present invention organically combines the processes of direct reduction of iron with blast furnace gas, in-situ capture and conversion of CO2, and can fully convert carbon-containing gases such as CO2 in blast furnace gas into carbon-containing gases of high economic value such as CO. While enriching the sources of high-quality raw gas for blast furnace injection, direct reduction processes, and chemical production processes, it effectively promotes the development of low-carbon ironmaking and green metallurgical technologies, and helps the steel industry reach carbon peak and carbon neutrality. In addition, the present invention can flexibly select the type of external reducing gas, such as natural gas, hydrogen, industrial gas (such as coke oven gas), etc., according to the different target products after CO2 reduction, and adjust the reaction temperature and the catalyst used accordingly to convert CO2 into different target products, such as CO, H2 / CO synthesis gas, CH4, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a process flow chart for directly reducing iron with blast furnace gas and simultaneously capturing CO2 to produce carbon-containing gases with high economic value such as CO.

[0034] Figure 2 The system diagram of the present invention is to directly reduce iron with blast furnace gas and simultaneously capture CO2 to produce carbon-containing gases with high economic value such as CO, including equipment connection methods and material flow directions, wherein: 1-feeding device, 2-iron ore reduction reactor, 3-gas-solid separator, 4-magnetic separation and conveying device, 5-fine reduction reactor, 6-1-separation gas reversing valve A, 6-2-reduction gas reversing valve B, 7-1-carbon fixation / carbon release reactor A, 7-2-carbon fixation / carbon release reactor B, 8-1-tail gas discharge valve A, 8-2-tail gas discharge valve B, 9-1-generated gas control valve A, 9-2-generated gas control valve B, 10-gas storage tank, 11-diverter valve.

[0035] Represents the flow direction of blast furnace gas; Represents the flow direction of iron ore powder; Represents the flow direction of the externally supplied reducing gas; Represents the flow direction of the generated gas in the carbon fixation / release reactor. DETAILED DESCRIPTION

[0036] The technical scheme of the present invention is clearly and completely described below in conjunction with the embodiments and the accompanying drawings. It should be pointed out that the embodiments described in the present invention are only used to further explain and illustrate, rather than to limit the scope of application. Based on the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0037] The process of the present invention is as follows Figure 1 shown.

[0038] The system used in the present invention is as follows Figure 2 shown.

[0039] The iron ore reduction reactor uses an entrained bed, and the carbon fixation / release reactor uses a double fixed bed. In the iron ore reduction reactor, blast furnace gas is the fluidizing gas and iron ore powder is the fluidizing particle. An entrained bed type fine reduction reactor can be added according to process requirements. In the fine reduction reactor, the carbon-rich gas converted from CO2 is the fluidizing gas, and the iron ore powder that is not fully reacted in the iron ore reduction reactor is the fluidizing particle.

[0040] In the embodiment, Qidashan hematite is taken as an example, and the production situation is as follows; the iron ore reduction reactor is a furnace with a reduction section length of 9m and a diameter of 4m. The mass fractions of the main components in the iron ore powder are as follows: TFe (total iron): 65.18%, FeO: 0.77%, SiO2: 4.41%, Al2O3: 0.12%, CaO: 0.077%, MgO: 0.45%, P: 0.042%, S: 0.051%. The contents of the various components of blast furnace gas in the embodiment are approximate values, and the components with very small contents are not listed.

[0041] Example 1

[0042] The components and contents of blast furnace gas are as follows: CO: 23%, CO2: 25%, N2: 50%, H2: 2%, the temperature of direct reduction of iron reaction is 850°C, the filling material is Ni-CaO adsorption-catalytic dual-functional material, methane is a reducing gas, the carbon fixation reaction temperature is 400°C, the carbon release reaction temperature is 650°C, the carbon-rich gas after CO2 conversion is mainly a CO / H2 mixed gas, and the fine reduction reaction temperature is 900°C.

[0043] The system for directly reducing iron with blast furnace gas and converting CO2 in situ is as follows:

[0044] The iron ore powder feeding device 1 is connected to the side feed port of the iron ore reduction reactor 2; the lower end of the iron ore reduction reactor 2 is connected to the blast furnace gas pipeline, and the upper end discharge port is connected to the gas-solid separator 3; the gas outlet of the gas-solid separator 3 is connected to the separation gas reversing valve A-6-1; the outlet of the separation gas reversing valve A-6-1 is respectively connected to the carbon fixation / release reactor A-7-1 and the carbon fixation / release reactor B-7-2; the reducing gas is respectively connected to the carbon fixation / release reactor A-7-1 and the carbon fixation / release reactor B-7-2 through the reducing gas reversing valve B-6-2; the carbon fixation / release reactor A-7-1 is respectively connected to the tail gas emission valve A-8-1 and the generated gas control valve A-9-1, and the carbon fixation / release reactor B-7-2 is respectively connected to the tail gas emission valve B-8-2 and the generated gas control valve B-9-2; the outlets of the generated gas control valve A-9-1 and the generated gas control valve B-9-2 are connected to the gas storage tank 10. According to the process requirements, a diverter valve 11 is arranged behind the generated gas control valve A-9-1 and the generated gas control valve B-9-2 and before the gas storage tank 10. One outlet of the diverter valve 11 is connected to the gas storage tank 10, and the other outlet is connected to the fine reduction reactor 5; the solid outlet of the gas-solid separator 3 is connected to the fine reduction reactor 5 via the magnetic separation and conveying device 4.

[0045] When the interface of the separation gas reversing valve A-6-1 connected to the carbon fixation / release reactor A-7-1 is opened, the exhaust gas emission valve A-8-1 connected to the carbon fixation / release reactor A-7-1 is opened, the interface of the reducing gas reversing valve B-6-2 is closed, and the generated gas control valve A-9-1 is closed; at this time, the interface of the separation gas reversing valve A-6-1 connected to the carbon fixation / release reactor B-7-2 is closed, the exhaust gas emission valve B-8-2 is closed, the interface of the reducing gas reversing valve B-6-2 is opened, and the generated gas control valve B-9-2 is opened.

[0046] When the interface of the separation gas reversing valve A-6-1 connected to the carbon fixation / release reactor A-7-1 is closed, the exhaust gas emission valve A-8-1 connected to the carbon fixation / release reactor A-7-1 is closed, the interface of the reducing gas reversing valve B-6-2 is opened, and the generated gas control valve A-9-1 is opened; at this time, the interface of the separation gas reversing valve A-6-1 connected to the carbon fixation / release reactor B-7-2 is opened, the exhaust gas emission valve B-8-2 is opened, the interface of the reducing gas reversing valve B-6-2 is closed, and the generated gas control valve B-9-2 is closed.

[0047] The method of directly reducing iron with blast furnace gas and capturing CO2 for in-situ conversion and utilization is as follows:

[0048] (1) Add Ni-CaO adsorption-catalysis dual-functional material to carbon fixation / release reactor A-7-1 and carbon fixation / release reactor B-7-2, and close the feed port after the addition is completed.

[0049] The blast furnace gas is heated to 6Nm 3 / s flow rate is passed into the iron ore reduction reactor 2 from the bottom, and the iron ore powder is fluidized under the influence of blast furnace gas. The feeding speed of the iron ore powder into the iron ore reduction reactor 2 is controlled and adjusted to 3.5kg / s by the feeding device 1, and the temperature is maintained at about 850°C. The reducing gases such as CO and H2 in the blast furnace gas can fully react with the iron oxides in the iron ore powder to generate iron by direct reduction reaction. At the same time, the CO in the blast furnace gas is oxidized to CO2, and the H2 is oxidized to H2O.

[0050] After the direct reduction reaction of iron, iron-containing solids and reaction gas mainly composed of N2 and CO2 are obtained. The reaction gas carries iron-containing solids (iron powder obtained by reduction, unreduced ore powder and other solid particles) into the gas-solid separator 3 for gas-solid separation.

[0051] (2) The reaction gas carrying the iron-containing solids undergoes gas-solid separation in the gas-solid separator 3. The iron-containing solids after gas-solid separation enter the magnetic separation and conveying device 4 to separate the iron powder. The unreduced ore powder obtained by magnetic separation is then conveyed to the fine reduction reactor 5.

[0052] After gas-solid separation, the reaction gas enters the carbon fixation / release reactor A-7-1 through the separation gas reversing valve A-6-1 for carbon fixation reaction. The reaction temperature is about 400°C. CO2 reacts with CaO to generate CaCO3, and the remaining gas (mainly N2) is discharged through the tail gas discharge valve A-8-1. During the carbon fixation reaction, the interface of the separation gas reversing valve A-6-1 connected to the carbon fixation / release reactor A-7-1 is opened, the tail gas discharge valve A-8-1 is opened, the interface of the reduction gas reversing valve B-6-2 is closed, and the generated gas control valve A-9-1 is closed.

[0053] After the carbon fixation / release reactor A-7-1 is fully carbon fixed, the interface of the separation gas reversing valve A-6-1 connected to it is closed, the tail gas discharge valve A-8-1 is closed, the interface of the reduction gas reversing valve B-6-2 is opened, and the generated gas control valve A-9-1 is opened. CH4 is the reducing gas at 3Nm 3 / s flow rate into the carbon fixation / release reactor A-7-1 for carbon release reaction, and at the same time realize the regeneration of CO2 absorbent. The carbon release reaction temperature is about 650℃, and the carbon-rich gas produced is mainly CO / H2 mixed gas. After passing through the generated gas control valve A-9-1, it passes through the diverter valve 11. According to the production situation, part of the generated gas is transported to the gas storage tank 10, and the other part of the generated gas is transported to the fine reduction reactor 5. While the carbon fixation / release reactor A-7-1 is performing the carbon release reaction, the interface of the separation gas reversing valve A-6-1 connected to the carbon fixation / release reactor B-7-2 is opened, the tail gas discharge valve B-8-2 is opened, the reduction gas reversing valve B-6-2 interface is closed, and the generated gas control valve B-9-2 is closed, so that the reaction gas separated by the gas-solid separator 3 enters the carbon fixation / release reactor B-7-2 for carbon fixation reaction, and the reaction temperature is about 400℃.

[0054] After the carbon fixation / release reactor B-7-2 is fully carbon fixed, the separation gas reversing valve A-6-1 connected to it is closed, the tail gas discharge valve B-8-2 is closed, the reduction gas reversing valve B-6-2 is opened, and the generated gas control valve B-9-2 is opened. Methane is used as the reducing gas at a rate of 3Nm 3 / s flow rate into the carbon fixation / release reactor B-7-2 for carbon release reaction, and at the same time realize the regeneration of CO2 absorbent. The carbon release reaction temperature is about 650℃, and the carbon-rich gas produced is mainly CO / H2 mixed gas. After passing through the generated gas control valve B-9-2, it passes through the diverter valve 11. According to the production situation, part of the generated gas is transported to the gas storage tank 10, and the other part of the generated gas is transported to the fine reduction reactor 5. While the carbon fixation / release reactor B-7-2 is performing the carbon release reaction, the interface of the separation gas reversing valve A-6-1 connected to the carbon fixation / release reactor A-7-1 is opened, the tail gas discharge valve A-8-1 is opened, the reduction gas reversing valve B-6-2 interface is closed, and the generated gas control valve A-9-1 is closed, so that the reaction gas separated by the gas-solid separator 3 enters the carbon fixation / release reactor A-7-1 for carbon fixation reaction, and the reaction temperature is about 400℃.

[0055] Gas analyzers are installed at tail gas discharge valve A-8-1 and tail gas discharge valve B-8-2. When the gas discharged from tail gas discharge valve A-8-1 contains CO2, carbon fixation / carbon release reactor A-7-1 ends carbon fixation and begins carbon release, and carbon fixation / carbon release reactor B-7-2 begins carbon fixation. Similarly, when the gas discharged from tail gas discharge valve B-8-2 contains CO2, carbon fixation / carbon release reactor B-7-2 ends carbon fixation and begins carbon release, and carbon fixation / carbon release reactor A-7-1 begins carbon fixation. This reciprocating cycle allows carbon fixation and carbon release reactions to be carried out alternately in carbon fixation / carbon release reactor A-7-1 and carbon fixation / carbon release reactor B-7-2, thereby achieving continuous and stable operation of the system.

[0056] (3) According to the process requirements, the CO / H2 mixed gas generated by the in-situ conversion of CO2 can be transported to the fine reduction reactor 5 through the diverter valve 11 to undergo a fine reduction reaction with the magnetic separation tailings powder. The reaction temperature is about 900°C, so that the ore powder in the fine reduction reactor 5 is fully reduced, thereby improving the conversion and utilization of the iron ore powder and the recovery rate of iron.

[0057] Example 2

[0058] The components and contents of blast furnace gas are as follows: CO: 23%, CO2: 25%, N2: 50%, H2: 2%, the temperature of direct reduction of iron reaction is 850°C, the filling material is Ni-CaO adsorption-catalytic dual-functional material, hydrogen is a reducing gas, the carbon fixation reaction temperature is 450°C, the carbon release reaction temperature is 700°C, the carbon-rich gas after CO2 conversion is mainly CO, and the fine reduction reaction temperature is 800°C.

[0059] The system for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ is the same as that in Example 1.

[0060] The method of directly reducing iron with blast furnace gas and capturing CO2 for in-situ conversion and utilization is as follows:

[0061] (1) Add Ni-CaO adsorption-catalysis dual-functional material to carbon fixation / release reactor A-7-1 and carbon fixation / release reactor B-7-2, and close the feed port after the addition is completed.

[0062] The blast furnace gas is heated to 5Nm 3 / s flow rate is passed into the iron ore reduction reactor 2, and the iron ore powder is fluidized under the influence of blast furnace gas, and the feeding speed of the iron ore powder into the iron ore reduction reactor 2 is controlled and adjusted to 3kg / s through the feeding device 1, and the temperature is maintained at about 850°C. The reducing gases such as CO and H2 in the blast furnace gas directly reduce the iron oxides in the iron ore powder to generate iron, and at the same time, the CO in the blast furnace gas is oxidized to CO2, and the H2 is oxidized to H2O.

[0063] After the direct reduction reaction of iron, iron-containing solids and reaction gas mainly composed of N2 and CO2 are obtained. The reactor carries the iron-containing solids (iron powder obtained by reduction, unreduced ore powder and other solid particles) into the gas-solid separator 3 for gas-solid separation.

[0064] (2) The reaction gas carrying the iron-containing solids undergoes gas-solid separation in the gas-solid separator 3. The iron-containing solids after gas-solid separation enter the magnetic separation and conveying device 4 to separate the iron powder. The unreduced ore powder obtained by magnetic separation is then conveyed to the fine reduction reactor 5.

[0065] In the carbon fixation / release reactor A-7-1 and the carbon fixation / release reactor B-7-2: the temperature of the carbon fixation reaction is 450°C; hydrogen is the reducing gas at 2.5 Nm 3 / s flow rate into the carbon fixation / release reactor A-7-1 or carbon fixation / release reactor B-7-2 for carbon release reaction, the carbon release reaction temperature is about 700°C, and the generated gas is mainly CO. The other processes are the same as in Example 1.

[0066] (3) According to the process requirements, the generated gas mainly composed of CO produced by the in-situ conversion of CO2 can be transported to the fine reduction reactor 5 through the diverter valve 11 to undergo a fine reduction reaction with the magnetic separation tailings powder. The reaction temperature is about 800°C, so that the ore powder in the fine reduction reactor 5 is fully reduced, thereby improving the conversion and utilization of the iron ore powder and the recovery rate of iron.

[0067] Example 3

[0068] The components and contents of blast furnace gas are as follows: CO: 23%, CO2: 25%, N2: 50%, H2: 2%, the temperature of direct iron reduction reaction is 850°C, the filling material is Ni-CaO adsorption-catalytic dual-functional material, hydrogen is a reducing gas, the temperature of carbon fixation reaction is 450°C, the carbon release reaction temperature is 500°C, the carbon-rich gas after CO2 conversion is mainly CH4, and the fine reduction reaction temperature is 800°C.

[0069] The system for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ is the same as that in Example 1.

[0070] The method of directly reducing iron with blast furnace gas and capturing CO2 for in-situ conversion and utilization is as follows:

[0071] (1) Add Ni-CaO adsorption-catalysis dual-functional material to carbon fixation / release reactor A-7-1 and carbon fixation / release reactor B-7-2, and close the feed port after the addition is completed.

[0072] The blast furnace gas is heated to 7Nm 3 / s flow rate is passed into the iron ore reduction reactor 2, and the iron ore powder is fluidized under the influence of blast furnace gas, and the feeding speed of the iron ore powder into the iron ore reduction reactor 2 is controlled and adjusted to 4kg / s through the feeding device 1, and the temperature is maintained at about 850°C. The reducing gases such as CO and H2 in the blast furnace gas directly reduce the iron oxides in the iron ore powder to generate iron, and at the same time, the CO in the blast furnace gas is oxidized to CO2, and the H2 is oxidized to H2O.

[0073] After the direct reduction reaction of iron, iron-containing solids and reaction gas mainly composed of N2 and CO2 are obtained. The reactor carries the iron-containing solids (iron powder obtained by reduction, unreduced ore powder and other solid particles) into the gas-solid separator 3 for gas-solid separation.

[0074] (2) The reaction gas carrying the iron-containing solids undergoes gas-solid separation in the gas-solid separator 3. The iron-containing solids after gas-solid separation enter the magnetic separation and conveying device 4 to separate the iron powder. The unreduced ore powder obtained by magnetic separation is then conveyed to the fine reduction reactor 5.

[0075] In the carbon fixation / release reactor A-7-1 and the carbon fixation / release reactor B-7-2: the temperature of the carbon fixation reaction is 450°C; hydrogen is the reducing gas at 13Nm3 / s flow rate into the carbon fixation / release reactor A-7-1 or carbon fixation / release reactor B-7-2 for carbon release reaction, the carbon release reaction temperature is about 500°C, and the generated gas mainly consists of CH4. The other processes are the same as in Example 1.

[0076] (3) According to the process requirements, the generated gas mainly composed of CH4 produced by the in-situ conversion of CO2 can be transported to the fine reduction reactor 5 through the diverter valve 11 to undergo a fine reduction reaction with the magnetic separation tailings powder. The reaction temperature is about 800°C, so that the ore powder in the fine reduction reactor 5 is fully reduced, thereby improving the conversion and utilization of the iron ore powder and the recovery rate of iron.

[0077] Example 4

[0078] The components and contents of blast furnace gas are as follows: CO: 24%, CO2: 25%, N2: 50%, H2: 1%, the temperature of direct iron reduction reaction is 800℃, the filling material is Cu-MgO adsorption-catalysis dual-functional material, natural gas is a reducing gas, the temperature of carbon fixation reaction is 300℃, the temperature of carbon release reaction is 650℃, the carbon-rich gas after CO2 conversion is mainly CO / H2 mixed gas, and the fine reduction reaction temperature is 900℃.

[0079] The system for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ is the same as that in Example 1.

[0080] The method of directly reducing iron with blast furnace gas and capturing CO2 for in-situ conversion and utilization is as follows:

[0081] (1) Add the Cu-MgO adsorption-catalysis dual-functional material into the carbon fixation / release reactor A-7-1 and the carbon fixation / release reactor B-7-2, and close the feed port after the addition is completed.

[0082] The blast furnace gas is heated to 5.5 Nm 3 / s flow rate is passed into the iron ore reduction reactor 2, and the iron ore powder is fluidized under the influence of blast furnace gas, and the feeding rate of the iron ore powder into the iron ore reduction reactor 2 is controlled and adjusted to 3.5kg / s through the feeding device 1, and the temperature is maintained at about 800°C. The reducing gases such as CO and H2 in the blast furnace gas directly undergo reduction reaction with the iron oxides in the iron ore powder to generate iron, and at the same time, the CO in the blast furnace gas is oxidized to CO2.

[0083] After the direct reduction reaction of iron, iron-containing solids and reaction gas mainly composed of N2 and CO2 are obtained. The reactor carries the iron-containing solids (iron powder obtained by reduction, unreduced ore powder and other solid particles) into the gas-solid separator 3 for gas-solid separation.

[0084] (2) The reaction gas carrying the iron-containing solids undergoes gas-solid separation in the gas-solid separator 3. The iron-containing solids after gas-solid separation enter the magnetic separation and conveying device 4 to separate the iron powder. The unreduced ore powder obtained by magnetic separation is then conveyed to the fine reduction reactor 5.

[0085] In the carbon fixation / release reactor A-7-1 and the carbon fixation / release reactor B-7-2: the temperature of the carbon fixation reaction is about 300°C, CO2 reacts with MgO to generate MgCO3; natural gas is the reducing gas at 3Nm 3 / s flow rate into the carbon fixation / carbon release reactor A-7-1 or carbon fixation / carbon release reactor B-7-2 for carbon release reaction, the carbon release reaction temperature is about 650°C, and the generated gas is mainly a CO / H2 mixed gas. The other processes are the same as in Example 1.

[0086] (3) According to the process requirements, the generated gas mainly consisting of a CO / H2 mixed gas produced by the in-situ conversion of CO2 can be transported to the fine reduction reactor 5 through the diverter valve 11 to undergo a fine reduction reaction with the magnetic separation tailings powder. The reaction temperature is about 900°C, so that the ore powder in the fine reduction reactor 5 is fully reduced, thereby improving the conversion and utilization of the iron ore powder and the recovery rate of iron.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the principle and spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ, characterized in that: The method includes the following: using blast furnace gas and iron ore powder as raw materials to directly reduce iron to obtain iron-containing solid and reaction gas; the reaction gas mainly contains CO2 and N2, and after the reaction of carbon fixation / carbon release, the CO2 is converted into generated gas containing carbon-rich gas in situ, and N2 is separated and recovered for other uses; The carbon-rich gas includes CO gas, H2 / CO mixed gas or CH4 gas; the blast furnace gas includes CO and CO2; the CO2 in the reaction gas includes the original CO2 in the blast furnace gas and the CO2 converted from the CO in the blast furnace gas through direct iron reduction reaction.

2. The method for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ according to claim 1, characterized in that: The carbon fixation / carbon release reaction includes a carbon fixation reaction and a carbon release reaction, wherein CO2 is first adsorbed and fixed by the filling material through the carbon fixation reaction, and then the CO2 fixed on the filling material is converted into carbon-rich gas in situ through the carbon release reaction under a reducing gas environment and released from the filling material; The reducing gas includes natural gas, hydrogen, or industrial gas containing CH4 and H2; the filling material includes a CO2 absorbent and a catalyst, which can adsorb CO2 and convert it into carbon-rich gas.

3. The method for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ according to claim 1, characterized in that: The main components and contents of the blast furnace gas are as follows: CO: 20% to 28%, CO2: 17% to 25%, N2: 50% to 55%, H2: 1% to 3%; the temperature of the direct reduction iron reaction is 800° C. to 900° C.; The iron-containing solid is magnetically separated into iron and unreduced iron ore powder, and carbon-rich gas is introduced into the unreduced iron ore powder for fine reduction reaction, so that the unreduced iron ore powder is further reduced to iron, and the temperature of the fine reduction reaction is 800°C to 900°C.

4. A system for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ, characterized in that: The system mainly includes a feeding device, an iron ore reduction reactor, a gas-solid separator, two groups of carbon fixation / release reactors, a gas storage tank, and a fine reduction reactor.

5. The system for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ according to claim 4 is characterized in that: The feed inlet of the iron ore reduction reactor is connected to the feeding device, and the discharge port is connected to the gas-solid separator; the two groups of carbon fixation / carbon release reactors are respectively connected to the separation gas reversing valve, the reducing gas reversing valve, the generated gas control valve, and the tail gas discharge valve; the gas outlet of the gas-solid separator is respectively connected to the two groups of carbon fixation / carbon release reactors through the separation gas reversing valve, the reducing gas is respectively connected to the two groups of carbon fixation / carbon release reactors through the reducing gas reversing valve, and the generated gas outlets of the two groups of carbon fixation / carbon release reactors are respectively connected to the gas storage tank and the fine reduction reactor through the generated gas control valve and the diverter valve in turn; the solid discharge port of the gas-solid separator is connected to the fine reduction reactor through a magnetic separation and conveying device.

6. The system for directly reducing iron with blast furnace gas and simultaneously converting and utilizing CO2 in situ according to claim 5, characterized in that: When the separation gas reversing valve interface connected to the carbon fixation / carbon release reactor is opened, the exhaust gas emission valve connected to the group of carbon fixation / carbon release reactors is opened, the reducing gas reversing valve is closed, and the generated gas control valve is closed; when the separation gas reversing valve interface connected to the carbon fixation / carbon release reactor is closed, the exhaust gas emission valve connected to the group of carbon fixation / carbon release reactors is closed, the reducing gas reversing valve interface is opened, and the generated gas control valve is opened.

7. The method for using the system according to any one of claims 4 to 6, characterized in that: The system is used to realize direct reduction of iron by blast furnace gas and capture CO2 for in-situ conversion and utilization, including the following specific contents: (1) Blast furnace gas is introduced into an iron ore reduction reactor, and iron ore powder is introduced into the iron ore reduction reactor through a feeding device, and the temperature in the reactor is maintained between 800° C. and 900° C. to perform a direct iron reduction reaction; iron-containing solids and reaction gas are obtained; the reaction gas is mainly N2 and CO2, and the reaction gas carries the iron-containing solids into a gas-solid separator; (2) The reaction gas carrying iron-containing solids is separated into gas and solids in a gas-solid separator. The iron-containing solids after gas-solid separation are subjected to magnetic separation for iron extraction, and the tailings powder discarded by magnetic separation enters the fine reduction reactor; the reaction gas after gas-solid separation enters the carbon fixation / release reactor for carbon fixation / release reaction, CO2 is converted into generated gas containing carbon-rich gas, and N2 is discharged and captured for other uses; (3) A portion of the generated gas containing carbon-rich gas is passed into a gas storage tank for storage, and the other portion is passed into a fine reduction reactor to undergo a fine reduction reaction with the magnetic separation tailings powder, so that the magnetic separation tailings powder that has not been reduced in the fine reduction reactor is reduced to iron, and the fine reduction reaction temperature is 800°C to 900°C.

8. The method for using the system according to claim 7, characterized in that: The carbon fixation / carbon release reaction in step (2) includes a carbon fixation reaction and a carbon release reaction, which are carried out in a fixed bed carbon fixation / carbon release reactor, wherein a filling material is present in the reactor bed, and two groups of carbon fixation / carbon release reactors work alternately; CO2 is first adsorbed and fixed by the filling material through a carbon fixation reaction, and then the CO2 fixed on the filling material is converted into a carbon-rich gas in situ through a carbon release reaction under a reducing gas environment and released from the filling material; During the carbon fixation reaction, the carbon fixation reaction temperature is 400℃~500℃, and the filling material is used to absorb and fix the CO2 in the reaction gas, and other gases are separated and discharged; During the carbon release reaction, a reducing gas is introduced into the carbon fixation / release reactor to convert the CO2 absorbed by the carbon fixation reaction into a carbon-rich gas in situ; the reducing gas includes natural gas, hydrogen, or industrial gas containing CH4 and H2; the carbon-rich gas includes CO gas, H2 / CO mixed gas, and CH4 gas.

9. The method for using the system according to claim 8, characterized in that: Step (2) includes the following specific contents: The reaction gas after gas-solid separation enters one of the groups of carbon fixation / carbon release reactors for carbon fixation reaction, and CO2 is adsorbed and fixed in the filling material. The remaining gas is discharged while the carbon is fixed. After sufficient carbon fixation, the reaction gas is stopped from being introduced into the group of carbon fixation / carbon release reactors, and reducing gas is introduced into the group of carbon fixation / carbon release reactors. A carbon release reaction occurs, and the CO2 fixed on the filling material is converted into carbon-rich gas in situ and released from the filling material, thereby realizing regeneration of the filling material. After the carbon release reaction is completed, the reducing gas is stopped from being introduced into the group of carbon fixation / carbon release reactors, and the reaction gas is introduced into the group of carbon fixation / carbon release reactors to undergo a carbon fixation reaction with the regenerated filling material. While reducing gas is introduced into the first group of carbon fixation / carbon release reactors for carbon release reaction, the reaction gas after gas-solid separation is introduced into the second group of carbon fixation / carbon release reactors for carbon fixation reaction by adjusting the valve. After sufficient carbon fixation, reducing gas is introduced into the second group of reactors for carbon release reaction; while the second group of reactors is carrying out carbon release reaction, the reaction gas after gas-solid separation is introduced into the first group of reactors for carbon fixation reaction by adjusting the valve; this cycle is repeated so that carbon fixation reaction and carbon release reaction are carried out alternately in the two groups of carbon fixation / carbon release reactors.

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