CN113373273A - Gas-based reduction method, gas-based reduction system and application of granular iron ore - Google Patents
Gas-based reduction method, gas-based reduction system and application of granular iron ore Download PDFInfo
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- C—CHEMISTRY; METALLURGY
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention provides a gas-based reduction method, a gas-based reduction system and application of granular iron ore, and relates to the technical field of smelting. The gas-based reduction method does not need pure oxygen or high-calorific-value fuel gas, takes natural gas as a raw material, and carries out desulfurization, steam reforming, shift reaction, first dehydration treatment and first CO removal on the compressed natural gas2The hydrogen-rich gas is preheated and is in countercurrent contact with the granular iron ore with specific particle size and specific preheating temperature to carry out reduction reaction, and granular direct reduced iron is prepared; because the particle size of the granular iron ore is smaller, the reduction reaction speed at the same temperature is faster than that of the traditional pellet ore, and the introduction is not neededAnd other binders and sintering processes greatly reduce pollution, and simultaneously, the granular iron ore and the hydrogen-rich gas at a specific preheating temperature are directly subjected to reduction reaction, and the reduction reaction is carried out at a low temperature by using the heat of the granular iron ore and the hydrogen-rich gas.
Description
Technical Field
The invention relates to the technical field of smelting, in particular to a gas-based reduction method and a gas-based reduction system for granular iron ore and application.
Background
In the global iron and steel smelting industry, various iron making technologies comprise blast furnace iron making technology and non-blast furnace iron making technology, wherein the non-blast furnace iron making technology comprises direct reduction and smelting reduction, and the direct reduction comprises gas-based reduction and coal-based reduction. The blast furnace ironmaking technology has the largest production scale and usage amount, and a large amount of dust, carbon dioxide and other gases are discharged in the coking and sintering processes in the blast furnace ironmaking process, thereby bringing great pressure to the environment. In the non-blast furnace ironmaking technology, the gas-based reduction process reduces iron oxide in iron ore into metallized pellets by using reducing gas, has higher ironmaking efficiency than the traditional carbon reduction method, does not need coking and sintering, and has cleaner production process.
At present, the gas-based reduction technology mainly adopts a Midrex gas-based shaft furnace technology and a HYL gas-based shaft furnace technology, and the use of the gas-based shaft furnace requires that iron ore and a binder are mixed and roasted to obtain oxidized pellets, and then reduction is carried out at high temperature by using reducing gas. Reducing gas in the Midrex gas-based shaft furnace enters the shaft furnace at 850-950 ℃, the reaction pressure is about 0.5MPa, and metallized pellets with the metallization rate of 92-93% can be obtained. The reducing gas of the HYL gas-based shaft furnace needs to be preheated to 900-2the/CO is 5.6-5.9, and the metallized pellet with the average metallization rate of 91-95 percent can be obtained.
In addition to shaft furnace technology, gas-based reduction technology also has fluidized bed technology. The hydrogen fluidized bed technology jointly developed by Hydro carbon Research Inc and Bethlehom Steel Conp adopts three sections of fluidized beds, and the mineral powder stays in the reduction bed for 45 hours to obtain reduced iron powder with the metallization rate of 98 percent, and H2The conversion rate is about 5 percent, and the operation is interrupted; the HIB fluidized bed technology developed by American iron and steel company adopts two-stage fluidized bed to obtain reduced iron powder H with metallization rate of 75% and temperature of 700 DEG C2The conversion rate is 32-36%; and FIOR technology developed by Exxon research and engineering companies under the operating conditions of 1.05MPa and 880 ℃, and adopting four fluidized beds for reaction to obtain metallization rate>90% of iron powder.
At present, the direct reduction technology adopts a shaft furnace technology for the most part, and adopts a coal-based direct reduction technology for a small amount so as to produce metal pellets with high metallization rate or hot-press the pellets into blocks as products. In the fluidized bed technology using iron powder as a product, only a few plants are still running due to the reasons of long retention time of reducing gas, low utilization efficiency of the reducing gas, low metallization rate of the product, influence of mutual adhesion among iron particles at high temperature on fluidization and the like, unstable running of the device, poor economic benefit and the like.
In view of the above, the present invention is particularly proposed to solve at least one of the above technical problems.
Disclosure of Invention
A first object of the present invention is to provide a method for gas-based reduction of particulate iron ore.
A second object of the present invention is to provide a gas-based reduction system of particulate iron ore.
A third object of the present invention is to provide a method for gas-based reduction of the above-mentioned particulate iron ore and the use of the gas-based reduction system.
In order to achieve the purpose, the following technical scheme is specially proposed:
the invention provides a gas-based reduction method of granular iron ore, which comprises the following steps:
(a) desulfurizing the compressed natural gas, mixing the desulfurized compressed natural gas with water vapor, and carrying out reforming reaction to obtain crude synthesis gas;
carrying out a shift reaction on the crude synthesis gas to obtain shift gas;
carrying out first dehydration treatment and decarbonization treatment on the converted gas to obtain hydrogen-rich gas;
(b) preheating hydrogen-rich gas, and then, carrying out countercurrent contact on the preheated granular iron ore to carry out reduction reaction to obtain granular directly-reduced iron;
wherein the average particle size of the granular iron ore is 0.015-4.00mm, the temperature of the preheated granular iron ore is 500-750 ℃, the temperature of the preheated hydrogen-rich gas is 450-650 ℃, and the average flow velocity of the hydrogen-rich gas is less than the minimum fluidization velocity of the granular iron ore.
Further, in the step (a), the pressure of the compressed natural gas is 1.5-3.0 MPa;
preferably, the natural gas is desulfurized after being preheated to the temperature of 200 ℃ and 400 ℃, and the mass fraction of sulfur in the natural gas after desulfurization is not higher than 0.1 ppm;
preferably, the volume ratio of the compressed natural gas to the water vapor is (2.5-3.6): 1;
preferably, the natural gas and the steam are mixed and then preheated to the temperature of 450-900 ℃ for reforming reaction, and the temperature of the reforming reaction is 800-900 ℃;
preferably, the composition of the dry gas in the raw synthesis gas comprises, in 100% by volume: h255-75％，CO 10-20％，CO210-20% and CH4 1-3％；
Preferably, the temperature of the shift reaction is 200-400 ℃;
preferably, the dry gas composition of the hydrogen-rich gas comprises, in 100% by volume: h285-99％，CO 0-10％，CO20-1％，CH4 1-10％。
Further, in the step (b), the flow ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore is 500-2000Nm3Reducing gas/t particulate iron ore;
preferably, the pressure of the reduction reaction is 0.05-3.00 MPa;
preferably, the time of the reduction reaction is 1 to 15 hours.
Further, the step (b) further comprises a step of carrying out second dehydration treatment on the reduction tail gas generated in the reduction reaction process to obtain purified tail gas;
preferably, at least part of the purified tail gas is mixed with the shift gas subjected to the first dehydration treatment for recycling; or at least partially purifying the tail gas and removing CO by the first CO removal2Mixing the treated hydrogen-rich gas for recycling;
preferably, the purified tail gas is mixed with fuel gas and oxygen-containing gas to be used as fuel, and the heat generated by the combustion of the fuel can be used for preheating the granular iron ore.
Further, in the step (b), the second CO removal is carried out on the reduction tail gas generated in the reduction reaction process2After the treatment, performing a second dehydration treatment to obtain purified tail gas;
preferably, the second CO removal2The decarbonizing agent used in the treatment comprises calcium oxide;
preferably, the calcium oxide is subjected to a second CO removal2Calcium carbonate is obtained after treatment, the calcium carbonate is regenerated at the temperature of 650-950 ℃, and the regenerated calcium oxide can be used as a decarbonizing agent for recycling.
The invention also provides a gas-based reduction system of the granular iron ore, which adopts the gas-based reduction method of the granular iron ore to produce the granular direct reduced iron;
the gas-based reduction system for the granular iron ores comprises a desulfurization device, a reforming device, a conversion device, a first dehydration device and a first CO removal device2The device comprises a device, a gas preheating device, a solid preheating device and a reduction reaction device;
compressed natural gas is conveyed into the desulfurization device through a pipeline, and the desulfurization device, the reforming device, the conversion device, the first dehydration device and the first CO removal device2The devices are connected in sequence so as to convert the compressed natural gas into hydrogen-rich gas;
the hydrogen-rich gas and the granular iron ore are respectively conveyed into the reduction reaction device through pipelines, a gas preheating device is arranged on the pipeline for conveying the hydrogen-rich gas, and a solid preheating device is arranged on the pipeline for conveying the granular iron ore.
Furthermore, a rotating part is arranged in the reduction reaction device.
Furthermore, the reduction reaction device comprises any one of a flow-through multi-stage furnace reactor, an air-suspension rotary kiln reactor or a flood dragon type reactor.
Further, the device also comprises a second dehydration device, the reduction reaction device is connected with the second dehydration device, and the second dehydration device is connected with the first CO removal device2Connecting devices; or, further comprises a second CO removal2The device and a second dehydration device, the reduction reaction device and the second CO removal device are sequentially arranged2The device is connected with a second dehydration device which is connected with the first CO removal device2The device is connected with or connected with the reduction reaction device；
Preferably, the gas-based reduction system further comprises a hot blast stove, the second dehydration device is connected with the hot blast stove, and the hot blast stove is connected with the solid preheating device;
preferably, the gas-based reduction system further comprises a regeneration device, the regeneration device and the second CO removal2The devices are connected.
The invention also provides an application of the gas-based reduction method of the granular iron ore or the gas-based reduction system of the granular iron ore in the field of direct reduced iron production.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention provides a gas-based reduction method of granular iron ore, which comprises the steps of desulfurizing compressed natural gas, reforming water vapor, carrying out shift reaction, carrying out first dehydration treatment and carrying out first CO removal2The gas-based reduction method does not need pure oxygen or high-calorific value fuel gas, uses natural gas as a raw material, converts the natural gas into hydrogen-rich gas, preheats the hydrogen-rich gas, and makes the hydrogen-rich gas contact with granular iron ore with a specific particle size and a specific preheating temperature in a countercurrent manner to carry out reduction reaction, thereby preparing granular directly reduced iron; because the particle size of the granular iron ore is smaller, the reduction reaction speed at the same temperature is higher than that of the traditional pellet ore, other binders and sintering processes are not needed to be introduced, the pollution is greatly reduced, meanwhile, the granular iron ore and the hydrogen-rich gas at the specific preheating temperature are directly subjected to the reduction reaction, the reduction reaction is carried out at low temperature by using the heat of the granular iron ore and the hydrogen-rich gas, the low-temperature reduction reaction does not need special high-temperature-resistant materials, and the bonding probability of the granular directly reduced iron in the reduction process is further reduced; the average flow velocity of the hydrogen-rich gas is lower than the minimum fluidization velocity of the granular iron ore, so that the gas cannot pass through a bed layer (the granular iron ore) in a bubble form to cause insufficient conversion rate of gas reaction; in addition, compared with the prior art, the CO in the gas-based reduction method for the granular iron ore provided by the invention is CO2Low dust discharge, cleanness and high efficiency.
(2) The invention provides a gas-based reduction system for granular iron ore, which adopts the gas-based reduction method for the granular iron ore to produce granular direct reduced iron, and has simple process flow and convenient operation.
(3) The invention also provides the application of the gas-based reduction method or the gas-based reduction system for the granular iron ore, and the gas-based reduction method or the gas-based reduction system for the granular iron ore has good application prospect in the field of direct reduced iron production in view of the advantages of the gas-based reduction method or the gas-based reduction system for the granular iron ore.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a gas-based reduction system of particulate iron ore according to an embodiment of the present invention;
FIG. 2 is a gas-based reduction system for particulate iron ore according to another embodiment of the present invention;
FIG. 3 is a schematic structural view of an air-suspension rotary kiln reactor provided by the present invention;
FIG. 4 is a schematic structural diagram of a shoveling and lifting component in the air-suspension rotary kiln reactor provided in FIG. 3;
FIG. 5 is a schematic structural diagram of a flood dragon type reactor provided by the invention;
FIG. 6 is a schematic structural diagram of a helical blade in the flood dragon type reactor provided in FIG. 5;
FIG. 7 is a schematic structural view of a flow-through multi-stage furnace reactor according to the present invention.
Icon: r1-desulfurization unit; r2-reformer; r3-transformation means; r4-first CO removal2A device; r5-reduction reaction device; r6-solid preheating device; r7-reduced iron powder hot briquetting machine; r8-electric furnace;r9-reduced iron powder tanker; r10-hot blast stove; r11-second CO removal2A device; e0-first dewatering device; e1-first heat exchanger; e2 — a second heat exchanger; e3-third heat exchanger; e4-fourth heat exchanger; e5-fifth heat exchanger; e6-sixth heat exchanger; e7-seventh heat exchanger; e8-eighth heat exchanger; e9-a second dewatering device; e10-gas preheating device; e11-eleventh heat exchanger; e12-twelfth heat exchanger; c1-compressor;
1-compressing natural gas; 2-water vapor; 3-an oxygen-containing gas a; 4-fuel gas a; 5-combustion gas tail gas; 6-condensed water a; 7-a decarboniser; 8-a decarboniser to absorb carbon dioxide; 9-sponge iron hot-pressing blocks; 10-condensate b; 11-recycle reducing gas tail gas; 12-fuel reducing gas tail gas; 13-fuel gas b; 14-oxygen-containing gas b; 15-burning tail gas by a hot blast stove; 16-a particulate iron ore; 17-calcium oxide; 18-calcium carbonate;
20-a main cylinder; 21-reducing; 22-a slewing cylinder section; 23-a closure mechanism; 24-a lifting component; 30-a rotating shaft; 31-a helical blade; 32-gas path channel; 33-a seal; 40-a housing; 41-stirring shaft; 42-material tray; 43-a blanking pipe; 44-a stirring arm; 45-a scraper; 46-air hole.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
According to a first aspect of the present invention, there is provided a gas-based reduction method of particulate iron ore, comprising the steps of:
(a) desulfurizing the compressed natural gas, mixing the desulfurized compressed natural gas with water vapor, and carrying out reforming reaction to obtain crude synthesis gas;
carrying out a shift reaction on the crude synthesis gas to obtain shift gas;
subjecting the shift gas to a first dehydration treatment and a first CO removal2Treating to obtain hydrogen-rich gas;
(b) preheating hydrogen-rich gas, and then, carrying out countercurrent contact on the preheated granular iron ore to carry out reduction reaction to obtain granular directly-reduced iron;
wherein the average particle size of the granular iron ore is 0.015-4.00mm, the temperature of the preheated granular iron ore is 500-750 ℃, the temperature of the preheated hydrogen-rich gas is 450-650 ℃, and the average flow velocity of the hydrogen-rich gas is less than the minimum fluidization velocity of the granular iron ore.
Specifically, in the step (a), the preparation of the granular direct reduced iron is carried out by using the compressed natural gas, which is feasible in cost and is beneficial to reducing the emission of carbon dioxide.
Because natural gas may contain a certain amount of sulfur, the sulfur in the natural gas is removed and then mixed with steam to carry out reforming reaction, and the reforming reaction generates crude synthesis gas mainly containing hydrogen, carbon monoxide and the like.
The raw syngas is subjected to a shift reaction to convert most of the carbon monoxide to hydrogen and carbon dioxide, resulting in a shifted gas.
The shift gas is subjected to a first dehydration treatment to convert water vapor contained in the shift gas into condensed water, and then removed, and subjected to a first CO removal treatment2Treating CO2Removing to obtain hydrogen-rich gas.
In the step (b), the reduction reaction is mainly carried out by using the reducing gas (hydrogen and carbon monoxide) in the hydrogen-rich gas and the granular iron ore.
The granular iron ore with the average grain diameter of 0.015-4.00mm is used as the raw material, and the granular iron ore has smaller grain size, so that the reduction reaction speed at the same temperature is higher than that of the traditional oxidized pellet or lump ore, and other binders and sintering processes are not required to be introduced, so that the energy consumption and pollution can be greatly reduced.
The size of the average particle diameter of the particulate iron ore is directly related to the size of the reduction reaction rate. The average particle size of the granular iron ore is too low (less than 0.015mm), so that the dust is easily too large, the void ratio is too low, the gas passing is influenced, the pressure drop and the energy consumption are increased, the average particle size of the granular iron ore is too high (more than 4.0mm), the problems of slow reduction rate, low product metallization rate, reaction pipeline blockage and the like are easily caused, and the average particle size of the granular iron ore is limited within a specific numerical range. Typical but non-limiting particulate iron ores have an average particle size of 0.015mm, 0.02mm, 0.04mm, 0.05mm, 0.08mm, 0.1mm, 0.2mm, 0.4mm, 0.5mm, 0.8mm, 1.0mm, 1.2mm, 1.4mm, 1.5mm, 1.8mm, 2.0mm, 2.2mm, 2.4mm, 2.5mm, 2.8mm, 3.0mm, 3.2mm, 3.4mm, 3.5mm, 3.8mm or 4.0 mm.
The granular iron ore and the hydrogen-rich gas are both preheated before the reduction reaction, the reduction reaction can be carried out at low temperature by utilizing the heat of the material, the temperature of the reduction reaction can reach 450-. The temperature of the preheated particulate iron ore is 500 ℃ and 750 ℃, and typical but not limiting temperatures are 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃ or 750 ℃. The temperature of the preheated hydrogen-rich gas is 450 ℃ to 650 ℃, and typical but not limiting temperatures are 450 ℃, 480 ℃, 500 ℃, 520 ℃, 550 ℃, 580 ℃, 600 ℃, 620 ℃ or 650 ℃.
The preheated granular iron ore and the preheated hydrogen-rich gas are in countercurrent contact, so that the gas-solid contact efficiency of the hydrogen-rich gas and the granular iron ore can be enhanced, the reduction reaction is more sufficient, and high conversion rate and metallization rate can be obtained at low temperature.
In the reduction reaction of the present invention, the average flow velocity of the hydrogen-rich gas is lower than the minimum fluidization velocity (U) of the particulate iron oremf) The granular iron ore is in a non-fluidized state, the hydrogen-rich gas can be more fully contacted with the granular iron ore, and the condition that a higher gas speed (generally the minimum is 0.8-1m/s, the retention time is shorter, and the gas can pass through a bed layer in a bubble form) is needed to ensure that the granules are in a fluidized state in a fluidized bed, so that the conversion rate is lower, the gas one-way conversion rate is only about 5 percent), the utilization efficiency of the hydrogen-rich gas is greatly improved compared with that of the fluidized bed, and the process energy consumption is reduced. At the same time, the production method has flexible and stable operation because the particles are not required to be maintained in a fluidized state at the momentThe performance is greatly improved.
The minimum fluidization velocity (U) of the particulate iron oremf) Can be measured by experiments or calculated by empirical formula, and the empirical formula is usually adopted
(principle of fluidization engineering, golden gush, etc., P19).
The invention provides a gas-based reduction method of granular iron ore, which comprises the steps of desulfurizing compressed natural gas, reforming water vapor, carrying out shift reaction, carrying out first dehydration treatment and carrying out first CO removal2The gas-based reduction method does not need pure oxygen or high-calorific value fuel gas, uses natural gas as a raw material, converts the natural gas into hydrogen-rich gas, preheats the hydrogen-rich gas, and makes the hydrogen-rich gas contact with granular iron ore with a specific particle size and a specific preheating temperature in a countercurrent manner to carry out reduction reaction, thereby preparing granular directly reduced iron; because the particle size of the granular iron ore is smaller, the reduction reaction speed at the same temperature is higher than that of the traditional pellet ore, other binders and sintering processes are not needed to be introduced, the pollution is greatly reduced, meanwhile, the granular iron ore and the hydrogen-rich gas at the specific preheating temperature are directly subjected to the reduction reaction, the reduction reaction is carried out at low temperature by using the heat of the granular iron ore and the hydrogen-rich gas, the low-temperature reduction reaction does not need special high-temperature-resistant materials, and the bonding probability of the granular directly reduced iron in the reduction process is further reduced; the average flow velocity of the hydrogen-rich gas is lower than the minimum fluidization velocity of the granular iron ore, so that the gas cannot pass through a bed layer (the granular iron ore) in a bubble form to cause insufficient conversion rate of gas reaction; in addition, compared with the prior art, the CO in the gas-based reduction method for the granular iron ore provided by the invention is CO2Low dust discharge, cleanness and high efficiency.
In a preferred embodiment of the present invention, in the step (a), the pressure of the compressed natural gas is 1.5 to 3.0 MPa; typical but non-limiting compressed natural gas pressures are 1.5MPa, 2.0MPa, 2.5MPa or 3.0 MPa.
The pressure of the natural gas in the invention is the common pressure of the natural gas in the pipeline, and the pressure can fluctuate due to the distance between the pipeline and the pipeline, and even if the pressure exceeds the range of 1.5-3.0MPa, the process and the technology of the invention are also within the protection range of the invention.
As a preferred embodiment of the invention, the natural gas is desulfurized after being preheated to the temperature of 200 ℃ and 400 ℃, and the mass fraction of sulfur in the natural gas after desulfurization is not higher than 0.1 ppm. The preheating temperature of the natural gas is 200 deg.C, 220 deg.C, 240 deg.C, 250 deg.C, 260 deg.C, 280 deg.C, 300 deg.C, 320 deg.C, 340 deg.C, 350 deg.C, 360 deg.C, 380 deg.C or 400 deg.C.
In a preferred embodiment of the present invention, the volume ratio of the compressed natural gas to the steam is (2.5 to 3.6): 1; the typical, but non-limiting, volume ratio of compressed natural gas to water vapor is 2.5: 1. 2.6: 1. 2.8: 1. 3.0: 1. 3.2: 1. 3.4: 1. 3.5: 1 or 3.6: 1.
as a preferred embodiment of the invention, after being mixed with water vapor, natural gas is preheated to 450-600 ℃ and then subjected to reforming reaction, wherein the temperature of the reforming reaction is 800-900 ℃; typical but non-limiting temperatures for the reforming reaction are 800 deg.C, 820 deg.C, 840 deg.C, 850 deg.C, 860 deg.C, 880 deg.C or 900 deg.C.
The volume ratio of the compressed natural gas to the steam and the temperature of the reforming reaction are limited, so that CH in the raw synthesis gas4As low as possible, and make H2The occupancy ratio is as large as possible.
As a preferred embodiment of the invention, the dry gas composition in the raw synthesis gas comprises, in 100% by volume: h2 55-75％，CO 10-20％，CO210-20% and CH4 1-3％。
Because the content of CO in the crude synthesis gas is high, the crude synthesis gas is subjected to shift reaction to obtain shift gas, and the shift gas is subjected to first dehydration treatment and first CO removal2And treating to obtain hydrogen-rich gas mainly containing hydrogen and carbon monoxide reduction gas.
As a preferred embodiment of the present invention, the dry gas composition of the hydrogen-rich gas comprises, in 100% by volume: h285-99％，CO 0-10％，CO20-1% and CH4 1-10％。
As a preferred embodiment of the present invention, the flow ratio of the reducing gas to the particulate iron ore in the hydrogen-rich gas in step (b) is 500-2000Nm3Reducing gas/t particulate iron ore. A typical but non-limiting flow ratio is 500Nm3Reducing gas/t particulate iron ore, 800Nm3Reducing gas/t particulate iron ore, 900Nm3Reducing gas/t particulate iron ore, 1000Nm3Reducing gas/t particulate iron ore, 1500Nm3Reducing gas/t particulate iron ore, 1800Nm3Reducing gas/t particulate iron ore or 2000Nm3Reducing gas/t particulate iron ore.
In the present invention, the hydrogen-rich gas reducing gas includes hydrogen and carbon monoxide, for example.
As a preferred embodiment of the present invention, in the step (b), the pressure of the reduction reaction is 0.05 to 3.00 MPa; typical but non-limiting reduction reaction pressures are 0.05MPa, 0.06MPa, 0.08MPa, 0.10MPa, 0.2MPa, 0.4MPa, 0.5MPa, 0.8MPa, 1.00MPa, 1.20MPa, 1.40MPa, 1.50MPa, 1.80MPa, 2.00MPa, 2.20MPa, 2.40MPa, 2.50MPa, 2.80MPa or 3.00 MPa.
By further limiting the pressure of the reduction reaction, not only the natural gas and the steam are reformed under proper pressure, but also the raw synthesis gas does not need to be compressed, and the raw synthesis gas is subjected to shift reaction, first dehydration treatment and first CO removal2After treatment, the wastewater can directly enter a reduction reactor for reduction reaction.
In a preferred embodiment of the present invention, the time for the reduction reaction is 1 to 15 hours. Typical but non-limiting reduction reaction times are 1h, 2h, 4h, 5h, 6h, 8h, 10h, 12h, 14h or 15 h.
By further limiting the reduction reaction time, the granular iron ores have enough reduction reaction time to obtain high metallization rate, and the low efficiency caused by overlong reaction time is avoided.
As a preferred embodiment of the present invention, the stepsIn the step (b), the method further comprises the step of subjecting the reduction tail gas generated in the reduction reaction process to optional second CO removal2And treating and performing second dehydration treatment to obtain the purified tail gas.
Note that "optional second CO removal2By treating "is meant secondary CO removal2The treatment may or may not be carried out, i.e. the reduction tail gas generated in the course of the reduction reaction is subjected to a second CO removal2And (3) treating and performing second dehydration treatment to obtain purified tail gas, or only performing second dehydration treatment on the reduced tail gas generated in the reduction reaction process to obtain purified tail gas.
As a preferred embodiment of the present invention, in the step (b), the second CO removal is carried out2The decarbonizing agent used in the treatment comprises calcium oxide;
preferably, the calcium oxide is subjected to secondary CO removal2Calcium carbonate is obtained after treatment, the calcium carbonate is regenerated at the temperature of 650-950 ℃, and the regenerated calcium oxide can be used as a decarbonizing agent for recycling.
The purified tail gas can be recycled in various ways.
As a preferred embodiment of the present invention, at least part of the purified tail gas is mixed with the shifted gas after the first dehydration treatment for recycling; or at least partially purifying the tail gas and removing CO by the first CO removal2The treated hydrogen-rich gas is mixed for reuse.
In a preferred embodiment of the present invention, the purified tail gas is mixed with a fuel gas and an oxygen-containing gas to be used as a fuel, and the heat generated by combustion is used for preheating the particulate iron ore.
The gas-based reduction method for the granular iron ore provided by the invention not only can realize the preparation of the granular direct reduced iron with higher metallization rate, but also can realize the efficient utilization of the reducing gas, greatly reduces the energy consumption in the process, fully recycles the heat and materials, and has good application prospect in the field of industrialized preparation of the granular direct reduced iron.
According to the second aspect of the present invention, there is also provided a gas-based reduction system for particulate iron ore, which performs production of particulate direct reduced iron by the above-mentioned gas-based reduction method for particulate iron ore;
the gas-based reduction system for the granular iron ores comprises a desulfurization device R1, a reforming device R2, a conversion device R3, a first dehydration device E0, and a first CO removal device2The device R4, the gas preheating device E10, the solid preheating device R6 and the reduction reaction device R5 are specifically shown in FIG. 1 and FIG. 2.
The compressed natural gas 1 is conveyed into a desulfurizer R1 through a pipeline, the desulfurizer R1, a reformer R2, a shift unit R3, a first dehydration unit E0 and a first CO removal unit2The device R4 is connected in turn to convert the compressed natural gas into hydrogen-rich gas;
the hydrogen-rich gas and the granular iron ores 16 are respectively conveyed into the reduction reaction device R5 through pipelines, a gas preheating device E10 is arranged on the pipeline for conveying the hydrogen-rich gas, and a solid preheating device R6 is arranged on the pipeline for conveying the granular iron ores.
Specifically, the compressed natural gas 1 is desulfurized by the desulfurizer R1, and the desulfurized natural gas is mixed with the steam 2 and then enters the reformer R2 to undergo a reforming reaction, so that the natural gas and the steam are converted into a raw synthesis gas mainly containing hydrogen, carbon monoxide, and the like. The raw syngas is passed to shift unit R3 to convert most of the carbon monoxide to hydrogen, yielding a shifted gas. The shift gas passes through a first dehydration device E0 to convert water vapor contained in the shift gas into condensed water a6, and then is subjected to first CO removal2The device R4 is used for removing carbon dioxide to obtain hydrogen-rich gas.
The gas preheating device E10 preheats the hydrogen-rich gas, the solid preheating device R6 preheats the granular iron ore 16, and the preheated hydrogen-rich gas and the preheated granular iron ore respectively enter the reduction reaction device R5 and are in countercurrent contact for reduction reaction. After the reduction reaction is finished, the reduction tail gas and the granular direct reduced iron are discharged from the reduction reaction device R5 respectively.
As an alternative embodiment of the invention, the gas-based reduction system also comprises a second dehydration device E9, and the reduction reaction device R5 is connected with the second dehydration device E9.
After the reduction reaction is finished, the reduction tail gas discharged from the reduction reaction device R5 is introduced into a second dehydration device E9 to remove condensed water b 10, and the purified tail gas is obtained after water is removed from the reduction tail gas.
As an alternative embodiment of the invention, the second dehydration unit E9 is connected to the first decarbonization2Device R4 is connected.
When the purified tail gas contains more carbon dioxide, at least part of the purified tail gas returns to the first dehydration treatment device E0, is mixed with the converted gas treated by the first dehydration treatment device E0 to be recycled as raw material, and then enters the first CO removal device2Apparatus R4 for CO removal2And (6) processing. Or when the purified tail gas contains less carbon dioxide, at least part of the purified tail gas is subjected to first CO removal2The hydrogen-rich gas treated by the device R4 is mixed.
As an alternative embodiment of the present invention, the gas-based reduction system further comprises a second CO removal system2The device R11, the second dehydration device E9, the reduction reaction device R5 and the second CO removal device in turn2The device is connected with a second dewatering device E9.
After the reduction reaction is finished, introducing the reduction tail gas discharged from the reduction reaction device R5 into a second CO removal device2Apparatus R11 for CO removal2And then, the condensed water is discharged through a second dehydration device E9, and the tail gas is reduced to remove water to obtain purified tail gas.
As an alternative embodiment of the invention, the second dehydration unit E9 is connected to the first decarbonization2The device R4 is connected, or the second dehydration device E9 is connected with the reduction reaction device R5, namely the purified tail gas and the first CO removal2The hydrogen-rich gas treated by the device R4 is mixed.
Preferably, second CO removal2The decarboniser used in unit R11 included calcium oxide;
preferably, the calcium carbonate obtained after the decarbonation treatment is regenerated at the temperature of 650-950 ℃, and the regenerated calcium oxide can be used as a decarbonizing agent for recycling.
The method is different from the prior method for removing carbon dioxide in the tail gas, wherein a liquid carbon dioxide absorbent or a solid adsorbent is usually used for removing carbon dioxide in the synthesis gas or the reduced tail gas at present, the gas is firstly cooled to normal temperature when in use, the gas is usually cooled to the normal temperature, and the gas is operated at the temperature of-50 ℃ even when low-temperature methanol washing is adopted, so that the energy consumption is great in the cooling and heating processes. The method directly absorbs the carbon dioxide in the hot reduction tail gas by using the calcium oxide, does not need to reduce the temperature, can reduce the amplitude of reducing the temperature of the reduction tail gas, only needs to consider the temperature (about 200 ℃) required in the second dehydration treatment, does not need to greatly increase the temperature when the dehydrated gas is recycled as the reduction gas, and reduces the energy consumption of the process. And the calcium oxide is used for absorbing the carbon dioxide, so that expensive liquid carbon dioxide absorbent (mostly organic amines) or other adsorbents are not consumed.
As an optional embodiment of the invention, the gas-based reduction system further comprises a hot blast stove R10, and the second dehydration device E9 is sequentially connected with the hot blast stove R10 and the solid preheating device R6;
at least part of the purified tail gas is used as fuel reducing gas tail gas 12 to be mixed with fuel gas b 13, then the mixture is combusted with oxygen-containing gas b14 in a hot blast stove R10, and the obtained combustion tail gas is introduced into a solid preheating device R6 to be discharged after heat utilization.
As an alternative embodiment of the present invention, the gas-based reduction system further comprises a regeneration device (not shown in the figure), which is separately connected to the first CO removal device2Plant and/or secondary CO removal2The devices are connected.
The regeneration device is mainly used for the first CO removal2Apparatus and second CO removal2And (4) regenerating the decarbonizing agent in the device.
Second CO removal2The device can adopt calcium oxide as decarbonizer, and the calcium oxide is subjected to CO removal2After treatment, calcium carbonate 18 is generated to remove CO from the second2Discharging the device, and then feeding the device into a regeneration device for regeneration treatmentThe obtained calcium oxide 17 can be returned to the second CO removal2The device is recycled as a decarbonizer.
Since each apparatus in the gas-based reduction system for particulate iron ore needs to use a large amount of heat to a different degree, the heat between the apparatuses is recycled.
As a preferred embodiment of the present invention, a gas-based reduction system for particulate iron ore comprises a desulfurization unit R1, a reforming unit R2, a shift unit R3, a first dehydration unit E0, and a first CO removal unit2The device R4, the gas preheating device E10, the solid preheating device R6, the reduction reaction device R5, the hot blast stove R10, the reduced iron powder hot briquetting machine R7, the electric furnace R8 and the reduced iron powder tanker R9, heat exchangers are further arranged among the devices, and each heat exchanger comprises a first heat exchanger E1, a second heat exchanger E2, a third heat exchanger E3, a fourth heat exchanger E4, a fifth heat exchanger E5, a sixth heat exchanger E6, a seventh heat exchanger E7, an eighth heat exchanger E8, an eleventh heat exchanger E11 and a twelfth heat exchanger E12 so as to realize the cyclic utilization of heat;
the compressed natural gas 1 is conveyed into a desulfurizer R1 through a pipeline, the desulfurizer R1, a reformer R2, a shift unit R3, a first dehydration unit E0 and a first CO removal unit2The device R4 is connected in turn to convert the compressed natural gas into hydrogen-rich gas;
the hydrogen-rich gas and the granular iron ores 16 are respectively conveyed into a reduction reaction device R5 through pipelines, a gas preheating device E10 is arranged on the pipeline for conveying the hydrogen-rich gas, and a solid preheating device R6 is arranged on the pipeline for conveying the granular iron ores;
the reduction reaction apparatus R5 is also connected to a fine reduced iron briquette machine R7, an electric furnace R8 or a fine reduced iron ladles car R9.
Specifically, the compressed natural gas 1 is preheated by a first heat exchanger E1 and then enters a desulfurization device R1 for desulfurization, the desulfurized natural gas is subjected to heat exchange by a second heat exchanger E2 and then is mixed with the steam 2 subjected to gradual heat exchange by a fifth heat exchanger E5 and a fourth heat exchanger E4, and the mixture is preheated by a third preheater E3 and then enters a reforming device R2 for reforming reaction, so that the natural gas and the steam are converted into the mixture mainly containing hydrogen, carbon monoxide and the likeThe raw synthesis gas of (3). The fuel gas a4 is mixed with the oxygen-containing gas a3 passing through the sixth heat exchanger E6 through the seventh heat exchanger E7 and then enters the reforming device R2 to be used as fuel for combustion to provide heat required by reforming, and the tail gas 5 of the combustion gas formed by fuel combustion is discharged after being subjected to gradual heat exchange through the third preheater E3, the fourth preheater E4, the fifth preheater E5, the sixth preheater E6 and the seventh preheater E7. Because the temperature of the crude synthesis gas is higher (about 800-. The shift gas passes through a first dehydration device E0 to convert water vapor contained in the shift gas into condensed water a6, and then is subjected to first CO removal2The device R4 is used for removing carbon dioxide to obtain hydrogen-rich gas. Wherein the first CO removal2In the device R4, the decarbonizer 7 is used for removing carbon dioxide, and the decarbonizer 8 absorbing carbon dioxide removes CO from the first2And discharged from the device R4.
And the hydrogen-rich gas enters a gas preheating device E10 for preheating after being subjected to heat exchange by an eighth heat exchanger E8. The granular iron ore 16 enters a solid preheating device R6 for preheating, the preheated hydrogen-rich gas and the preheated granular iron ore respectively enter a reduction reaction device R5 for carrying out a reduction reaction by countercurrent contact, after the reduction reaction is finished, the granular iron ore is converted into granules for directly reducing iron, and the hydrogen-rich gas is converted into reduction tail gas. The granular direct reduced iron enters a reduced iron powder hot briquetting machine R7 to be made into hot briquettes 9 according to the requirement, or directly enters an electric furnace R8 to be smelted in the next step, or enters a reduced iron powder loading truck R9 to enter the next working procedure.
According to different treatment modes of the reduction tail gas, different process flows can be adopted. As shown in fig. 1, the reduction tail gas is discharged from the reduction reaction device R5, enters the second dehydration device E9, and is subjected to condensed water b 10 removal, so as to obtain a purified tail gas. Returning partial purified tail gas serving as the tail gas 11 of the circulating reducing gas to a first dehydration treatment device E0 through a compressor C1, mixing the tail gas with the converted gas treated by a first dehydration treatment device E0, and then entering a first CO removal device2The apparatus R4 carries out decarbonation treatment. And after being mixed with fuel gas b 13 as fuel reducing gas tail gas 12, part of the purified tail gas is combusted with oxygen-containing gas b14 in a hot blast stove R10, and the obtained combustion tail gas is introduced into a solid preheating device R6 to be used as hot blast stove combustion tail gas 15 and then is discharged.
Alternatively, as shown in FIG. 2, the reduction tail gas is discharged from the reduction reactor R5 to enter the second CO removal2The device R11 is decarbonized and then enters a second dehydration device E9 to remove condensed water b 10, and purified tail gas is obtained. Part of the purified tail gas is used as a circulating reducing gas tail gas 11 and returns to the first CO removal process through a compressor C12After the device R4, the first CO removal is carried out2The hydrogen-rich gases treated by the device R4 are mixed and then enter a reduction reaction device R5 for reduction reaction. And after being mixed with fuel gas b 13 as fuel reducing gas tail gas 12, part of the purified tail gas is combusted with oxygen-containing gas b14 in a hot blast stove R10, and the obtained combustion tail gas is introduced into a solid preheating device R6 for heat utilization and then is discharged as hot blast stove combustion tail gas 15.
Through further limiting the specific structure and the process flow of the gas-based reduction system of the granular iron ore, the heat is fully recycled while the granular iron ore is realized.
The reduction reactor is an important part of the gas-based reduction system for the particulate iron ore.
As an alternative embodiment of the present invention, a rotating member is disposed in the reduction reaction apparatus, wherein the rotating member is any one of a screw, a rotating arm, or a rotary drum.
In order to further achieve sufficient contact between the granular iron ores and the hydrogen-rich gas so that the reduction reaction is sufficiently performed, as a preferred embodiment of the present invention, the reduction reaction apparatus includes any one of an air-suspension type rotary kiln reactor, a dragon type reactor, or a cross-flow type multi-stage furnace reactor.
An empty suspension type rotary kiln reactor, a flood dragon type reactor and a cross-flow type multi-stage furnace reactor are reduction reaction devices which are self-researched and designed by the inventor according to actual reaction requirements. The structure of each reactor will be described below.
Specifically, as shown in fig. 3 and 4, the air-suspension rotary kiln reactor includes: the rotary kiln comprises a rotary kiln barrel, wherein the rotary kiln barrel comprises a main barrel body 20 and reducing parts 21 which are connected to two ends of the main barrel body and respectively shrink outwards, the reducing ends of the reducing parts 21 are connected with rotary cylinder sections 22, the rotary cylinder sections 22 are connected with a sealing mechanism 23, and a sealing assembly is arranged at the joint of the sealing mechanism 23 and the rotary cylinder sections; the main cylinder 20 is internally provided with a plurality of lifting components 24, so that the granular iron ore can form a multi-layer material curtain when the rotary kiln cylinder rotates, and hydrogen-rich gas can pass through the multi-layer material curtain to be fully contacted with the granular iron ore. The sealing mechanism 23 is connected to the rotary shell ring 22 after necking, so that the mounting difficulty of the sealing assembly between the rotary shell ring 22 and the sealing mechanism 23 is reduced, the contact area of the granular iron ore and the hydrogen-rich gas is effectively increased by the formed multilayer material curtain, and the reaction can be fully and completely carried out.
As shown in fig. 5 and 6, the flood dragon reactor comprises a shell, a rotating shaft 30 is installed at the axis of the shell, a helical blade 31 for conveying solid materials is connected to the rotating shaft 30, and a plurality of gas path channels 32 for hydrogen-rich gas to pass through are arranged on the helical blade 31; the solid material is filled in the reaction cavity of the shell and contacts with the hydrogen-rich gas in the reverse direction to carry out reduction reaction. Through the pivot 30 at flood dragon reactor internally mounted and at sealing member 33 between pivot and casing, effectively improved flood dragon reactor's leakproofness to make flood dragon reactor can the pressure-bearing operation. Through the helical blade 31 of installation on pivot 30 to combine the airtight structure of flood dragon reactor, can make granular iron ore be full of the reaction chamber space of whole reactor, effectively improved the filling rate of granular iron ore.
A flow-through multi-stage furnace reactor is shown in fig. 7, comprising: the stirring device comprises a shell 40, a stirring shaft 41 and a plurality of material discs 42 arranged at intervals along the axial direction of the shell 40, wherein blanking pipes 43 for blanking are connected to the material discs 42; the upper parts of the material trays 42 are provided with stirring arms 44, and the stirring arms 44 are connected with scrapers 45 for uniformly distributing the granular iron ores on the material trays 42; a plurality of air holes 46 are uniformly distributed in each material tray 42 for allowing the granular iron ores uniformly distributed in the material tray 42 to be sufficiently contacted with the reducing gas in the hydrogen-rich gas. The plurality of air holes 46 uniformly distributed on the material tray 42 realize the uniform distribution of the hydrogen-rich gas, the hydrogen-rich gas can flow out layer by layer from bottom to top and can be fully contacted with the granular iron ores uniformly distributed on the material tray 42, the contact area of the granular iron ores and the hydrogen-rich gas is effectively increased, and the reaction can be fully and completely carried out.
According to a third aspect of the present invention, there is also provided the use of the above-described method for gas-based reduction of particulate iron ore or the system for gas-based reduction of particulate iron ore in the field of direct reduced iron production.
In view of the advantages of the gas-based reduction method or the gas-based reduction system for the granular iron ores, the method or the system has good application in the field of direct reduced iron production.
The technical solution of the present invention will be further described with reference to examples and comparative examples.
Example 1
The embodiment provides a gas-based reduction method of granular iron ores, which comprises the following steps:
(a) desulfurizing gasified liquefied natural gas with the pressure of 2.8MPa, and mixing the desulfurized liquefied natural gas with steam in a volume ratio of (3.5-3.6): 1, carrying out reforming reaction at the temperature of 870 ℃ to obtain crude synthesis gas; wherein the mass fraction of sulfur in the natural gas after desulfurization is less than 1 ppm; the composition of the dry gas in the raw synthesis gas comprises: h268-70％，CO 12-13％，CO216-18% and CH41-1.5％；
Carrying out a shift reaction on the crude synthesis gas, wherein the temperature of the shift reaction is 360-380 ℃, and obtaining shift gas;
subjecting the shift gas to a first dehydration treatment and a first CO removal2Treating to obtain hydrogen-rich gas; wherein, the dry gas composition of the hydrogen-rich gas comprises: h293-96％，CO 3-5％，CO20-0.2％，CH41.2-1.7％。
(b) Preheating hydrogen-rich gas, and then, carrying out countercurrent contact on the preheated granular iron ore to carry out reduction reaction, wherein the reduction reaction pressure is 2.5MPa, and the reduction reaction time is 6 hours, so as to obtain granular directly-reduced iron;
reducing the temperature of the reduction tail gas to 180 ℃ plus 210 ℃, and returning 95 percent of the reduction tail gas to the first CO removal after removing condensed water2And (4) pretreatment of the device.
Wherein the granular iron ore comprises the chemical compositions of total iron, FeO and SiO2、CaO、MgO、Al2O3MnO contents of 62.7%, 27.3%, 1.32%, 1.53%, 3.45%, 0.82% and 0.28% respectively, the particle size of the granular iron ore is 48-150 μm, the average particle size is 0.105mm, the temperature of the preheated granular iron ore is 650-700 ℃, and the temperature of the hydrogen-rich gas after preheating is 600-630 ℃;
the average flow velocity of the hydrogen-rich gas flowing through the bed was 0.065m/s, and the minimum fluidization velocity U was obtained under the conditions of the granular iron ore having the above particle diameter, the hydrogen-rich gas and the reaction pressuremfIt was 0.086 m/s.
In the reduction reactor, the flow ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore is 1400Nm3Reducing gas/t particulate iron ore.
The reduction reaction device is a cross-flow multi-stage furnace reactor, and the direct reduced iron powder with the metallization rate of 97.8 percent can be obtained in the process, the carbon content is 1.4 percent, and the once-through utilization efficiency of the reducing gas is 24.2 percent.
Example 2
The embodiment provides a gas-based reduction method of granular iron ores, which comprises the following steps:
(a) desulfurizing compressed natural gas with the pressure of 2MPa, and then mixing the desulfurized compressed natural gas with water vapor in a volume ratio of (3.2-3.3): 1, carrying out reforming reaction at the temperature of 850 ℃ to obtain crude synthesis gas; wherein the mass fraction of sulfur in the natural gas after desulfurization is less than 1 ppm; the composition of the dry gas in the raw synthesis gas comprises: h263-65％，CO 15-16％，CO213-15% and CH43-3.5％，N22-3％；
Carrying out a shift reaction on the crude synthesis gas, wherein the temperature of the shift reaction is 230 ℃ and 250 ℃, and obtaining shift gas;
subjecting the shift gas to a first dehydration treatment and a first CO removal2Treating to obtain hydrogen-rich gas; wherein, the dry gas composition of the hydrogen-rich gas comprises: h292-94％，CO 0.3-0.5％，CO20-0.1％，CH43.5-4.1％，N2 2.3-3.5％。
(b) Preheating hydrogen-rich gas, and then, carrying out countercurrent contact on the preheated granular iron ore to carry out reduction reaction, wherein the reduction reaction pressure is 1.5MPa, and the reduction reaction time is 3.5h, so as to obtain granular directly-reduced iron;
reducing the temperature of the reduction tail gas to 160-190 ℃, and returning 90 percent of the reduction tail gas to the first carbon dioxide removal device for post-treatment after removing condensed water.
Wherein the granular iron ore comprises the chemical compositions of total iron, FeO and SiO2、Al2O3And MnO with the content of 66.2%, 1.4%, 5.2%, 0.43% and 0.06%, wherein the particle size of the granular iron ore is 75-270 μm, the average particle size is 0.15mm, the temperature of the preheated granular iron ore is 630-560 ℃, and the temperature of the preheated hydrogen-rich gas is 540-560 ℃;
the average flow velocity of the hydrogen-rich gas flowing through the bed was 0.09m/s, and the minimum fluidization velocity U was determined under the conditions of the granular iron ore having the particle size, the hydrogen-rich gas and the reaction pressuremfIs 0.13 m/s.
In the reduction reactor, the flow ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore is 1500Nm3Reducing gas/t particulate iron ore.
The reduction reactor is a flood dragon reactor. The process can obtain direct reduced iron particles with the metallization rate of 98.5 percent, the carbon content is 0.1 percent, and the once-through utilization efficiency of reducing gas is 26.3 percent.
Example 3
The embodiment provides a gas-based reduction method of granular iron ores, which comprises the following steps:
(a) desulfurizing compressed natural gas with the pressure of 1MPa, and then mixing the desulfurized compressed natural gas with water vapor in a volume ratio of (3.1-3.2): 1, carrying out reforming reaction at 860 ℃ to obtain crude synthesis gas; wherein, the postdesulfurizationThe mass fraction of sulfur in the natural gas is less than 1 ppm; the composition of the dry gas in the raw synthesis gas comprises: h260-64％，CO 14-15％，CO214-16% and CH42-2.5％，N26-8％；
Carrying out a shift reaction on the crude synthesis gas, wherein the temperature of the shift reaction is 260 ℃ and 280 ℃, and obtaining shift gas;
subjecting the shift gas to a first dehydration treatment and a first CO removal2Treating to obtain hydrogen-rich gas; wherein, the dry gas composition of the hydrogen-rich gas comprises: h285-88％，CO 2-2.2％，CO20-0.1％，CH42.4-2.9％，N27-9.5％。
(b) Preheating hydrogen-rich gas, and then, carrying out countercurrent contact on the preheated granular iron ore to carry out reduction reaction, wherein the reduction reaction pressure is 0.6MPa, and the reduction reaction time is 5h, so as to obtain granular directly-reduced iron;
the reduction tail gas is firstly subjected to secondary CO removal2Plant in which CO2The content is reduced to below 0.1 percent, then the temperature is reduced to 130-150 ℃, and 80 percent of condensed water is returned to the first CO removal step after being removed2And (5) carrying out post-treatment on the device.
Wherein the granular iron ore comprises the chemical compositions of total iron, FeO and SiO2、CaO、MgO、Al2O3MnO, the content of which is respectively 55.2%, 0.29%, 8.69%, 0.01%, 6.53% and 0.07%, the particle size of the granular iron ore is 380-4000 mu m, the average particle size is 1.05mm, the temperature of the preheated granular iron ore is 710-730 ℃, and the temperature of the hydrogen-rich gas after preheating is 500-520 ℃;
the average flow velocity of the hydrogen-rich gas through the bed was 0.4m/s, and the minimum fluidization velocity was 0.63m/s under the conditions of the granular iron ore having the above particle diameter, the hydrogen-rich gas and the reaction pressure.
In the reduction reactor, the flow ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ore was 950Nm3Reducing gas/t particulate iron ore.
The reduction reactor is an air-suspension rotary kiln reactor. The direct reduced iron powder with the metallization rate of 96.5 percent can be obtained in the process, the carbon content is 0.7 percent, and the once-through utilization efficiency of reducing gas is 30.6 percent.
Example 4
This example provides a gas-based reduction system for particulate iron ore corresponding to the gas-based reduction method for particulate iron ore of example 1, as shown in fig. 1.
The gas-based reduction system for the granular iron ores comprises a desulfurization device R1, a reforming device R2, a conversion device R3, a first dehydration device E0 and a first CO removal device2The device R4, the gas preheating device E10, the solid preheating device R6, the reduction reaction device R5, the hot blast stove R10, the reduced iron powder hot briquetting machine R7, the electric furnace R8 and the reduced iron powder tanker R9, heat exchangers are further arranged among the devices, and each heat exchanger comprises a first heat exchanger E1, a second heat exchanger E2, a third heat exchanger E3, a fourth heat exchanger E4, a fifth heat exchanger E5, a sixth heat exchanger E6, a seventh heat exchanger E7, an eighth heat exchanger E8, an eleventh heat exchanger E11 and a twelfth heat exchanger E12 so as to realize the cyclic utilization of heat;
the compressed natural gas 1 is conveyed into a desulfurizer R1 through a pipeline, the desulfurizer R1, a reformer R2, a shift unit R3, a first dehydration unit E0 and a first CO removal unit2The device R4 is connected in turn to convert the compressed natural gas into hydrogen-rich gas;
the hydrogen-rich gas and the granular iron ores 16 are respectively conveyed into a reduction reaction device R5 through pipelines, a gas preheating device E10 is arranged on the pipeline for conveying the hydrogen-rich gas, and a solid preheating device R6 is arranged on the pipeline for conveying the granular iron ores;
the reduction reaction apparatus R5 is also connected to a fine reduced iron briquette machine R7, an electric furnace R8 or a fine reduced iron ladles car R9.
Example 5
This example provides a gas-based reduction system for particulate iron ore corresponding to the gas-based reduction method for particulate iron ore of example 2, as shown in fig. 1.
The gas-based reduction system for the granular iron ores comprises a second dehydration device E9 and a first CO removal device2The pipeline behind the device R4 is connected, so that the partially purified tail gas is subjected to first CO removal2Mixing the treated hydrogen-rich gas, and connecting the rest structuresExample 4 is the same.
Example 6
This example provides a gas-based reduction system for particulate iron ore corresponding to the gas-based reduction method for particulate iron ore of example 3, as shown in fig. 2.
The gas-based reduction system for the granular iron ores is used for removing CO from the reduction tail gas discharged from the reduction reaction device2After condensed water is discharged by the device R11 and the second dehydration device E9, purified tail gas is obtained. Second dehydration plant E9 and first CO removal2The pipeline behind the device R4 is connected, so that the partially purified tail gas is subjected to first CO removal2The treated hydrogen-rich gas was mixed, and the remaining structure and connection were the same as in example 4.
The above examples show that the gas-based reduction method for granular iron ore provided by the invention uses natural gas as a raw material, and obtains a hydrogen-rich gas through the processes of steam reforming, conversion, dehydration and decarburization, and the like, and the granular iron ore can be reduced into a granular directly-reduced iron product by using the hydrogen-rich gas, and the metallization rate of the product reaches 96-99%, and the product belongs to a high-specification reduced iron product. The processing process does not need to adopt a special pellet raw material of the gas-based shaft furnace, does not need to adopt high temperature of more than 900 ℃, does not need reaction time of dozens of hours like a fluidized bed, also greatly improves the conversion rate of reducing gas, avoids a large amount of gas circulation caused by too low conversion rate, reduces power consumption, is a clean and efficient direct iron reduction method, can reduce energy consumption in the steel smelting process by adopting a system of the method, and can remove carbon dioxide from reducing tail gas at high temperature by adopting calcium oxide as a decarbonizing agent, further reduces energy consumption and improves efficiency.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A gas-based reduction method of particulate iron ore, characterized by comprising the steps of:
(a) desulfurizing the compressed natural gas, mixing the desulfurized compressed natural gas with water vapor, and carrying out reforming reaction to obtain crude synthesis gas;
carrying out a shift reaction on the crude synthesis gas to obtain shift gas;
subjecting the shift gas to a first dehydration treatment and a first CO removal2Treating to obtain hydrogen-rich gas;
(b) preheating hydrogen-rich gas, and then, carrying out countercurrent contact on the preheated granular iron ore to carry out reduction reaction to obtain granular directly-reduced iron;
wherein the average particle size of the granular iron ore is 0.015-4.00mm, the temperature of the preheated granular iron ore is 500-750 ℃, the temperature of the preheated hydrogen-rich gas is 450-650 ℃, and the average flow velocity of the hydrogen-rich gas is less than the minimum fluidization velocity of the granular iron ore.
2. The gas-based reduction method of particulate iron ore according to claim 1, wherein in the step (a), the pressure of the compressed natural gas is 1.5 to 3.0 MPa;
preferably, the natural gas is desulfurized after being preheated to the temperature of 200 ℃ and 400 ℃, and the mass fraction of sulfur in the natural gas after desulfurization is not higher than 0.1 ppm;
preferably, the volume ratio of the compressed natural gas to the water vapor is (2.5-3.6): 1;
preferably, the natural gas and the steam are mixed and then preheated to the temperature of 450-900 ℃ for reforming reaction, and the temperature of the reforming reaction is 800-900 ℃;
preferably, the composition of the dry gas in the raw synthesis gas comprises, in 100% by volume: h255-75％，CO 10-20％，CO210-20% and CH4 1-3％；
Preferably, the temperature of the shift reaction is 200-400 ℃;
preferably, in volume percentThe dry gas composition of the hydrogen-rich gas comprises, by number 100%: h285-99％，CO 0-10％，CO20-1% and CH4 1-10％。
3. The gas-based reduction method for particulate iron ores as set forth in claim 1 or 2, wherein the flow ratio of the reducing gas in the hydrogen-rich gas to the particulate iron ores in step (b) is 500-2000Nm3Reducing gas/t particulate iron ore;
preferably, the pressure of the reduction reaction is 0.05-3.00 MPa;
preferably, the time of the reduction reaction is 1 to 15 hours.
4. The method for gas-based reduction of particulate iron ore according to claim 1 or 2, wherein the step (b) further comprises subjecting the reduction off-gas generated during the reduction reaction to a second dehydration treatment to obtain a purified off-gas;
preferably, at least part of the purified tail gas is mixed with the shift gas subjected to the first dehydration treatment for recycling; or at least partially purifying the tail gas and removing CO by the first CO removal2Mixing the treated hydrogen-rich gas for recycling;
preferably, at least part of the cleaned tail gas is used as fuel in combination with a fuel gas and an oxygen-containing gas, and the heat generated by the combustion of the fuel is used to preheat the particulate iron ore.
5. The gas-based reduction method of particulate iron ore according to claim 1 or 2, wherein the step (b) further comprises subjecting the reduction off-gas generated during the reduction reaction to a second CO removal2Treating, and then performing second dehydration treatment to obtain purified tail gas;
preferably, the second CO removal2The decarbonizing agent used in the treatment comprises calcium oxide;
preferably, the calcium oxide is subjected to a second CO removal2Calcium carbonate is obtained after treatment, the calcium carbonate is regenerated at the temperature of 650-950 ℃, and the regenerated calcium oxide can be used as a decarbonizing agent for recycling.
6. A gas-based reduction system for particulate iron ore, characterized in that the production of particulate direct reduced iron is carried out by the gas-based reduction method for particulate iron ore according to any one of claims 1 to 5;
the gas-based reduction system for the granular iron ores comprises a desulfurization device, a reforming device, a conversion device, a first dehydration device and a first CO removal device2The device comprises a device, a gas preheating device, a solid preheating device and a reduction reaction device;
compressed natural gas is conveyed into the desulfurization device through a pipeline, and the desulfurization device, the reforming device, the conversion device, the first dehydration device and the first CO removal device2The devices are connected in sequence so as to convert the compressed natural gas into hydrogen-rich gas;
the hydrogen-rich gas and the granular iron ore are respectively conveyed into the reduction reaction device through pipelines, a gas preheating device is arranged on the pipeline for conveying the hydrogen-rich gas, and a solid preheating device is arranged on the pipeline for conveying the granular iron ore.
7. The gas-based reduction system according to claim 6, wherein a rotating member is provided in the reduction reaction device.
8. The gas-based reduction system according to claim 6, wherein the reduction reaction device comprises any one of a flow-through multi-stage furnace reactor, an air-suspension rotary kiln reactor or a screw conveyor reactor.
9. The gas-based reduction system according to any one of claims 6 to 8, further comprising a second dehydration apparatus, wherein the reduction reaction apparatus is connected to the second dehydration apparatus, and the second dehydration apparatus is connected to the first CO removal apparatus2Connecting devices; or, further comprises a second CO removal2The device and a second dehydration device, the reduction reaction device and the second CO removal device are sequentially arranged2The device is connected with a second dewatering device which is connected with the first dewatering deviceFirst CO removal2The device is connected with the reduction reaction device;
preferably, the gas-based reduction system further comprises a hot blast stove, the second dehydration device is connected with the hot blast stove, and the hot blast stove is connected with the solid preheating device;
preferably, the gas-based reduction system further comprises a regeneration device, the regeneration device and the second CO removal2The devices are connected.
10. Use of the method for the gas-based reduction of particulate iron ore according to any one of claims 1 to 5 or the system for the gas-based reduction of particulate iron ore according to any one of claims 6 to 9 in the field of direct reduced iron production.
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| WO2023173147A1 (en) * | 2022-03-10 | 2023-09-14 | Manic Iron Technology Proprietary Limited | Recovery of iron from iron ore fines using hydrogen rich gas |
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