Ammonia cooling reduction metallization agglomeration method and method for producing molten iron

Abstract

The invention relates to an ammonia cooling reduction metallization agglomeration method which comprises the following steps: a pellet manufacturing process: manufacturing green pellets containing iron oxide ore, and oxidizing and roasting at the temperature of 1180-1300 DEG C to obtain oxidized pellets; the oxidized pellets obtained in the pellet manufacturing procedure are not cooled and are added into a shaft furnace reduction section through a conveying system and a feeding system, the temperature of the pellets entering the feeding system ranges from 1080 DEG C to 1250 DEG C, ammonia gas heated to 780 DEG C to 920 DEG C is introduced into the shaft furnace reduction section, the pellets are reduced through the ammonia gas, and metallized pellets are obtained; and a carburizing process: arranging a carburizing section below the reduction section of the shaft furnace, introducing carbon-containing gas into the carburizing section for cooling and carburizing, and obtaining metal blocks of direct reduced iron (DRI) through a discharging system. The invention also relates to a method for producing molten iron, which comprises a metallization agglomeration process and an electric melting furnace melting process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steel metallurgy, and belongs to the technical field of pretreatment of raw materials for ferrous metallurgy (C22B 1 / 16). More particularly, it relates to an ammonia cooling reduction metallization briquetting method and a method for producing molten iron. BACKGROUND

[0002] Due to the influence of resource and energy endowment conditions, the steel process in China is mainly based on the blast furnace-converter long process technology. This process makes full use of the characteristics of heat release in the reduction process of fossil fuels and iron ore. Carbon is not only a reducing agent, but also a heating agent, and can maintain the high temperature required for the reaction during the reduction process, which has the advantages of high efficiency and high energy utilization rate, and provides a large amount of primary steel materials with high cost performance for economic and social development. However, in the process of rapid industrialization of society, human activities have had a certain impact on the global climate. During the industrialization process, the concentrated and large-scale emission of CO2 and other greenhouse gases is considered to be the main cause of global warming. Due to the characteristics of the steel industry, a certain amount of carbon dioxide must be emitted during the production process.

[0003] As an important process in the whole process, the energy consumption and carbon emission of blast furnace and raw material pretreatment before ironmaking account for 70-80% of the whole process. Therefore, how to reduce the carbon emission of the ironmaking process is the key to solving the green development of the steel industry. Due to the characteristics of the blast furnace ironmaking process, there are usually two technical ideas to reduce carbon emissions. One is to remove CO2 and add a certain amount of hydrogen through top gas circulation, recycle the reducing gas, and reduce the carbon consumption of the process. The second is to use gas-based direct reduction process to produce direct reduced iron (DRI) with hydrogen or full hydrogen as reducing agent, which can replace the molten iron in the blast furnace and be used in the electric furnace, thereby greatly reducing the carbon emission of the smelting process. Direct reduced iron retains the shape before oxygen loss and forms a large number of micropores after oxygen loss. Its microscopic morphology is in the form of sponge structure, also known as sponge iron.

[0004] Among them, the short process technology combined with hydrogen metallurgy and electric furnace is considered to be the most potential technology direction to realize carbon neutralization in the steel manufacturing process. Patent CN111534659A introduces a "parallel heat storage type gas-based shaft furnace and method for producing direct reduced iron"; patent CN104195278B introduces a "iron ore shaft furnace-rotary kiln direct reduction iron powder production process"; patent CN103261446 introduces a "method and device for producing direct reduced iron using hydrogen and CO containing reducing gas source"; patent CN105408500A introduces a "method for reducing iron oxide to metallic iron using natural gas"; patent CN103898265B introduces a "coke oven gas reforming direct reduction of iron ore system device and method"; and patent CN110484672A introduces a "method for producing direct reduced iron in a gas-based shaft furnace". These schemes introduce that after heating with coke oven gas, natural gas or hydrogen-rich gas, the iron concentrate or pellets are introduced into the reactor, and the iron concentrate or pellets are heated from room temperature to high temperature and react with hot reducing gas to obtain metal pellets or iron powder for subsequent process. However, these processes have the problems of low reaction temperature in the furnace, long residence time of the furnace charge in the furnace, especially in the reduction zone, and low industrial efficiency.

[0005] On the other hand, since the production site of green electricity and green hydrogen is usually at a certain distance from the use site, and the cost of hydrogen liquefaction and storage is relatively high, it limits its actual use in industry. Therefore, some researchers have carried out frontier exploration of ammonia reduction of iron ore.

[0006] Patent CN202110110344 introduces a "method for producing hot sponge iron by direct reduction of iron based on ammonia", which introduces ammonia into a reaction device containing iron-containing raw materials, and ammonia is catalytically decomposed into nitrogen and hydrogen while participating in the reduction reaction of iron oxides to reduce iron oxides to metallic iron. The raw material is iron concentrate, pellets or lump ore, intermittent production, first heat the iron-containing raw material to high temperature in the shaft furnace, then replace with nitrogen, then reduce with ammonia, the reaction temperature is 890-910℃, and the reaction time is more than 3h.

[0007] Although this type of research uses ammonia for direct reduction, the essence of the process is similar to using ammonia as a source of hydrogen, which cannot solve the above-mentioned problems of hydrogen-based shaft furnace process. Therefore, the direct reduction of ammonia is still at the stage of theoretical research and laboratory exploration, and it is urgent to innovate the ammonia reduction metal agglomeration process that meets the requirements of industry.

[0008] In addition, the existing research on ammonia reduction does not involve the subsequent use of sponge iron. This sponge iron, without the presence of carbon, has a melting point equivalent to that of metallic iron, reaching 1535℃, which is significantly different from the solidification temperature of conventional carbon-containing molten iron of 1150℃, and it is difficult to melt in an electric furnace.

[0009] The present inventors, in view of the above-described prior art problems, cancel the cooling process (for example, the ring cooler in the pellet chain grate-kiln or the belt-type roaster) in the conventional pellet manufacturing process, add hot pellets into a shaft furnace, increase the temperature in the furnace using the high temperature of the pellets, pass in high-temperature ammonia gas, and cool and rapidly reduce the pellets, thereby obtaining high-metalization DRI metal block furnace charge.

[0010] Further, the DRI furnace charge is permeated with biomass biogas, and hot DRI is passed into an electric melting furnace to complete the final reduction and melting separation, thereby obtaining molten iron and slag, realizing ammonia direct reduction metallization briquetting and molten iron production that meet industrial requirements, and meeting the demand for manufacturing various high-quality steels in a converter. At the same time, the method of the present application can realize low-carbon emission or zero-carbon emission. SUMMARY

[0011] In view of the above technical problems in the prior art of the gas-based shaft furnace-electric furnace process, in particular, the problems of insufficient temperature in the hydrogen-based gas reduction furnace and low efficiency, and the problems of immature ammonia gas reduction technology, and in view of the problems of long process, high energy consumption, low reduction efficiency, and high electric furnace smelting temperature caused by repeated heating, cooling, and temperature rising in the processes of pellet oxidation preparation, shaft furnace direct reduction, and electric furnace smelting, the present inventors have repeatedly researched, improved the ammonia direct reduction cooling process, and realized ammonia direct reduction metallization briquetting and molten iron production that meet industrial requirements, and met the demand for manufacturing various high-quality steels in a converter. At the same time, the method of the present application can meet the requirements of low-carbon emission or zero-carbon emission. Specifically, the present application relates to the following technical solutions:

[0012] [1]. An ammonia cooling reduction metallization briquetting method, characterized in that it comprises:

[0013] Pellet manufacturing process: manufacturing green pellets of iron oxide-containing ore, and performing oxidation roasting at a temperature of 1180-1300°C to obtain oxidized pellets;

[0014] Reduction process: directly adding the oxidized pellets obtained in the pellet manufacturing process into a reduction section of a shaft furnace through a conveying system and a feeding system without cooling, the temperature of the pellets entering the feeding system being 1080-1250°C, passing in ammonia gas heated to 780-920°C in the reduction section of the shaft furnace, and obtaining metallized pellets by reducing the pellets with the ammonia gas;

[0015] and a carburizing process: setting a carburizing section below the reduction section of the shaft furnace, passing in carbon-containing gas in the carburizing section to cool and carburize, and obtaining direct reduced iron (DRI) metal briquetting through a discharging system.

[0016] [2]. The ammonia-cooled reduction metallization briquetting method according to [1], wherein the time of the reduction process is 50-100 minutes, and the metallization rate of the metallized pellets in the reduction process is 82-99%.

[0017] [3]. The ammonia-cooled reduction metallization briquetting method according to [1], wherein in the reduction process, after the pellets enter the upper tank of the charging system, heated steam and / or nitrogen is first introduced to control the oxygen content in the gas phase in the material layer to be less than 1%, then the pellets enter the middle tank and are pressurized to 0.2-0.8 MPa, and then enter the lower tank and enter the shaft furnace with the pressure controlled to be between 0.2-0.8 MPa, and the temperature of the pellets when entering the shaft furnace is between 1150-1220°C.

[0018] [4]. The ammonia-cooled reduction metallization briquetting method according to any one of [1]-[3], wherein the volume ratio of the other gases in the reduction gas introduced into the shaft furnace to ammonia is less than 10%, and the ammonia consumption is 580-720 Nm 3 / tDRI, and the temperature of the shaft furnace reduction section is 1250°C or lower and 780°C or higher.

[0019] [5]. The ammonia-cooled reduction metallization briquetting method according to any one of [1]-[3], wherein in the pellet manufacturing process, one or more of magnetite, hematite and limonite with a Blaine specific surface area of ≧1400 cm 2 / g pretreated by ball milling or high-pressure roller milling is mixed with 0.7-1.5% bentonite, and limestone is added to adjust the CaO / SiO2 binary basicity of the pellets to 0.2-1.3, and green pellets with a particle size of 8-20 mm are obtained by a pelletizer, and the green pellets enter a chain grate-kiln and / or a belt-type roaster for drying and preheating, and then enter a roasting section with a preheating temperature of 900-950°C and a preheating time of 15-20 min, and a roasting temperature of 1180-1300°C, and the pellets after roasting are transported by a chain conveyor or a gas conveying system.

[0020] [6]. The ammonia-cooled reduction metallization briquetting method according to any one of [1]-[3], wherein in the carburization process, biomass biogas is introduced as a carbon-containing gas for carburization and cooling, and the metallized pellets are cooled to 450-550°C, and the C content is controlled to be between 1-3%, and the consumption of the biomass biogas is 60-90 Nm 3 / tDRI.

[0021] [7]. The ammonia-cooled reduction metallization briquetting method according to any one of [1]-[3], wherein the metallized briquettes obtained in the carburization process contain metallic iron, iron carbide, iron nitride, and 1-20% ferrous oxide.

[0022] [8]. A method for producing molten iron, characterized by comprising the following processes:

[0023] Metalizing briquetting process: using the ammonia cooling reduction metalization briquetting method of any one of [1] to [7], obtaining a metal briquette,

[0024] and an electric furnace melting process: adding the obtained metal briquette into an electric melting furnace for melting to obtain molten iron.

[0025] [9]. The method for producing molten iron according to [8], wherein after hot charging of the electric melting furnace, limestone and dolomite are added for slagging, the slag basicity is controlled between 1.0 and 1.2, and biomass carbon is sprayed for direct reduction of iron and carburization of molten iron.

[0026]

[10] . The method for producing molten iron according to [8] or [9], wherein no carbon emission is generated during the production of molten iron.

[0027] The ammonia cooling reduction metalization briquetting method and the method for producing molten iron of the present application can have at least the following advantages in industry:

[0028] 1. The oxidation pelletizing process is organically combined with the pellet cooling and reduction process by using the mature chain grate-rotary kiln production device and / or belt-type roaster and the most efficient shaft furnace, and the pellet cooling and direct reduction pellet heating processes are cancelled, pure ammonia gas is used for cooling and reduction, and the process is more concise and the energy utilization efficiency is improved.

[0029] 2. The physical heat of high-temperature pellets is used to meet part of the heat required for reduction and gas heating, so that the ammonia reduction thermodynamic condition is more reasonable, the reduction time is greatly shortened, and the metalization rate of ammonia reduction is high, which can obtain metal briquettes that are beneficial to further smelting, and further reduce the overall energy consumption and time cost;

[0030] 3. Ammonia is convenient to store and transport, green ammonia can be conveniently transported over a long distance, and a zero-carbon molten iron production solution is provided for steel enterprises near areas lacking green hydrogen resources, and the subsequent converter and rolling system does not need to be changed too much.

[0031] 4. The pellet roasting process preferably uses non-fossil energy combustion such as cracking gas, pyrolysis oil, biomass oil, and biomass carbon, green electricity drives the equipment, pure ammonia cooling reduction, and biomass biogas for carburization, which can realize low-carbon or zero-carbon process production of molten iron.

[0032] 5. In the ammonia reduction process, part of the reduced product will inevitably form nitrides, which will cause the nitrogen content of molten steel to be too high in the traditional electric furnace process, making it difficult to produce high-quality steel such as silicon steel / automobile sheet that requires strict nitrogen content. In the direct reduction iron electric melting furnace process, the nitrides will decompose at high temperatures during molten iron smelting, and nitrogen will not be brought into the subsequent process. It is beneficial to produce high-quality steel that requires strict nitrogen content. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A schematic diagram showing an example of the apparatus for the ammonia-cooled reduction metallization briquetting method and the hot metal production method of the present application. DETAILED DESCRIPTION

[0034] The present application relates to an ammonia-cooled reduction metallization briquetting method and a hot metal production method, wherein the metallization briquetting refers to the process of metallizing the metal elements in the oxidized state in the metal-containing ore through reduction, etc., and briquetting the metallized ore to obtain the metallization briquetting for subsequent melting and smelting. The hot metal production method includes the reduction metallization and the metallization briquetting processes, and further melting into hot metal.

[0035] One embodiment of the present application relates to an ammonia-cooled reduction metallization briquetting method, characterized in that it includes the following processes. A pellet manufacturing process: manufacturing green pellets of iron oxide-containing ore, and obtaining oxidized pellets by roasting at a temperature of 1180-1300°C; a reduction process: without cooling, the oxidized pellets obtained in the pellet manufacturing process are directly deoxidized and pressurized through a conveying system and a feeding system, and then added to a reduction section of a shaft furnace, the temperature of the pellets entering the feeding system is 1080-1250°C, ammonia gas heated to 780-920°C is introduced into the reduction section of the shaft furnace, and the ammonia gas reduces the pellets to obtain metallized pellets; and a carburizing process: a carburizing section is arranged below the reduction section of the shaft furnace, a carbon-containing gas is introduced into the carburizing section for cooling and carburizing, and the metallization briquetting of direct reduced iron is obtained through a discharging system.

[0036] < Pellet manufacturing process >

[0037] In the ammonia-cooled reduction metallization briquetting method of the present application, in the pellet manufacturing process, green pellets of iron oxide-containing ore are manufactured, and oxidized pellets are obtained by roasting at a temperature of 1180°C or higher. The pellet manufacturing process of the present application is characterized in that the ring cooler / cooling section of the conventional pellet manufacturing process is cancelled, and the high-temperature pellets are directly used in the next process, thereby reducing the time length of the pellet manufacturing process and shortening the process flow.

[0038] The temperature of the high-temperature pellets is usually 1080°C or higher, and is further preferably 1220°C or higher. There is no particular limitation on the upper limit, but from the perspective of industrial practicability, it can be 1300°C or lower. In typical examples, the temperature of the pellets can be 1250-1280°C.

[0039] In the ammonia-cooled reduction metallization briquetting method of the present application, the pellet manufacturing process can use the existing grate-kiln roasting or belt roasting system. For example, the iron ore concentrate can be finely ground in the conventional process, and then balling is performed after adding bentonite. The green pellets with a particle size of 8-20 mm are dried, preheated, and high-temperature roasted in the grate-kiln roaster or belt roaster, and the circular cooler or cooling section is eliminated. The high-temperature pellets (1080-1250°C) are pneumatically transported to the reduction shaft furnace by the chain conveyor or high-temperature resistant pipeline.

[0040] Specifically, in the pellet manufacturing process, one or more of magnetite, hematite, and limonite with a Blaine specific surface area of ≥ 1400 cm 2 / g, which is pretreated by ball milling or high-pressure roller milling, is mixed with 0.7-1.5% bentonite, and limestone is added to adjust the CaO / SiO2 binary basicity of the pellets to 0.2-1.3. The green pellets with a particle size of 8-20 mm are obtained by a balling machine, and the green pellets are dried and preheated in the grate-kiln roaster or belt roaster. Then, the pellets are preheated to a temperature of 900-950°C for 15-20 min, and then roasted at a temperature of 1180-1300°C. The roasted pellets are transported by the chain conveyor or gas transport system.

[0041] <Reduction process>

[0042] In the ammonia-cooled reduction metallization briquetting method of the present application, the oxidized pellets obtained in the pellet manufacturing process are not cooled, but are directly deoxidized and pressurized by the transport system and the feeding system, and then are added to the reduction section of the shaft furnace. The temperature of the pellets entering the feeding system is between 1080°C and 1250°C, and ammonia gas heated to 780-920°C is introduced into the reduction section of the shaft furnace. The ammonia gas reduces the pellets to obtain metallized pellets.

[0043] The main function of the feeding system is to control the oxygen content in the gas phase of the pellet bed and to adjust the pressure of the pellet bed to be consistent with that of the shaft furnace. Typically, the feeding system is located above the shaft furnace and includes an upper, middle, and lower pellet pipe. The high-temperature oxidized pellets, which are not subjected to a temperature adjustment step, enter the upper tank of the feeding system, and then heated steam or nitrogen is introduced to control the oxygen content in the gas phase of the pellet bed to be <1%. Then, the pellets enter the middle tank and are pressurized to 0.2-0.8 MPa. After that, the pellets enter the lower tank and then enter the shaft furnace, which is pressurized to 0.2-0.8 MPa. The temperature of the pellets entering the shaft furnace (reduction section) is between 1080°C and 1250°C.

[0044] One of the features of the present application is that the pellets entering the shaft furnace are high-temperature pellets that are not cooled after preparation, and the heat of the pellets is fully utilized for the reduction reaction. As a result, the temperature in the shaft furnace can be increased, the time for the reduction reaction in the reduction section of the shaft furnace can be shortened, and the cost can be reduced.

[0045] In the reduction section of the shaft furnace, high temperature ammonia gas is introduced to reduce and cool the high temperature pellets. In the present invention, the high temperature ammonia gas is ammonia gas heated to 780-920℃. The main body of the ammonia gas introduced into the shaft furnace is ammonia gas, not ammonia decomposition gas. Here, the main body of ammonia gas refers to the ammonia gas not containing or containing only a small amount of other gases, for example, the volume percentage of other gases is less than 10%, preferably less than 8%, more preferably less than 5%. Here, the ammonia gas introduced into the shaft furnace refers to the ammonia gas after the heating process. In the reduction section of the shaft furnace, due to the presence of iron oxides and metallic iron, part of the ammonia gas may decompose to produce hydrogen and nitrogen.

[0046] The ammonia gas is heated to above 780℃, preferably above 800℃, more preferably above 840℃. From the perspective of industrial application, the heating temperature of ammonia gas is below 920℃, preferably below 900℃. The heating method of ammonia gas is not particularly limited and can be any commonly used method in industry, preferably electric heating such as green electricity heating or other heating means that do not produce carbon emissions. In the heating process of ammonia gas in the present invention, no catalyst or the like for ammonia decomposition is provided.

[0047] In the reduction section of the shaft furnace, ammonia gas directly reduces high temperature pellets and produces water and nitrogen. The reduction section of the shaft furnace usually does not have a temperature adjusting means, and the reduction of iron ore is an endothermic reaction, so the high temperature pellets are cooled while being reduced by ammonia gas. Depending on the temperature of the pellets or ammonia gas and the reaction progress, the temperature of the solid material in the reduction section of the shaft furnace is below 1250℃ and above 780℃, preferably above 840℃.

[0048] One of the features of the present invention is the relatively high temperature in the reduction section of the shaft furnace, and the high temperature physical heat carried by the solid material, which provides part of the heat required for the reduction of iron oxides, and also reduces the time for the pellets in the conventional process to rise from room temperature (25℃) to about 900℃, thereby improving the efficiency of the reduction reaction and greatly reducing the reaction time, thereby saving a large amount of cost. In traditional hydrogen-based reduction, the process of hydrogen reducing iron ore to generate water will absorb a large amount of heat, causing the temperature in the furnace to drop rapidly, reducing the reaction efficiency, and the typical residence time of the reduction section in the MIDREX gas-based shaft furnace process is about six hours. However, in the present invention, although the ammonia reduction reaction is an endothermic reaction, the nitrogen gas produced by the ammonia reduction reaction accounts for a considerable proportion, which can slow down the decrease of the furnace temperature. Further, by using the heat of the high temperature pellets themselves and using high temperature ammonia gas as the reducing gas in the present invention, the temperature in the furnace can be ensured.

[0049] Therefore, the present invention also features that the time of the reduction process occurring in the reduction section of the shaft furnace is 50-100 minutes, preferably 90 minutes or less, more preferably 70 minutes or less. The shortening of the time in this reduction process will greatly improve the production efficiency, reduce the production cost, and bring huge economic benefits.

[0050] Meanwhile, the metallization rate of the metallized pellets in the reduction process is 82% or more, preferably 87% or more, and more preferably 92% or more, and the upper limit of the metallization rate is not particularly limited and can be 100%, but from the perspective of industrial practice, it is 99% or less. The reduction effect of the process of the present application is good, and the metallization rate of the metal briquetting meets the requirements of further smelting in industry, further reducing energy consumption and time cost.

[0051] In addition, the ammonia consumption in the ammonia gas introduced into the shaft furnace is 580-720 Nm 3 / tDRI, preferably 580-650 Nm 3 / tDRI.

[0052] <carburization process>

[0053] The ammonia cooling reduction metallization briquetting method of the present application further comprises a carburization process, which sets a carburization section below the reduction section of the shaft furnace, introduces carbon-containing gas into the carburization section to cool and carburize, and obtains direct reduced iron DRI metal briquetting through the discharge system.

[0054] In the carburization process, the pellets after metallization are carburized to adjust their carbon content and further cooled. The carbon-containing gas used is not particularly limited and can be a commonly used gas containing carbon elements in industry, such as methane, coke oven gas, etc., but from the perspective of carbon neutralization, it is preferred to use biomass biogas for carburization and cooling. The consumption of biomass biogas is, for example, 60-90 Nm 3 / tDRI.

[0055] After the carburization process, the temperature of the metallized pellets can be reduced to 450-550℃, and the C content is controlled between 1-3%. The metal briquetting obtained in the carburization process contains metallic iron, iron carbide, iron nitride, and 1-20% of ferrous oxide. The melting temperature of the above-mentioned metallized pellets is low, which can enter the electric melting furnace for deep reduction and slag-iron separation to produce molten iron. The content of ferrous oxide is preferably within 8%, and further preferably within 5%. The lower limit of the content of ferrous oxide is not particularly limited and can be 1% or more from the perspective of industrial practice.

[0056] Another embodiment of the present application relates to a method for producing molten iron, characterized in that it comprises: a metallization briquetting process: metallization briquetting is carried out by using the above-mentioned ammonia cooling reduction metallization briquetting method to obtain metal briquetting; and an electric furnace melting process: the obtained metal briquetting is added to an electric melting furnace for deep reduction and melting to obtain molten iron.

[0057] <electric furnace melting process>

[0058] The method for producing molten iron of the present application is a method for further performing electric melting and deep reduction in a separate furnace to obtain molten iron after performing metallization briquetting using the above-mentioned ammonia-cooled reduction metallization briquetting method.

[0059] The electric melting process can be performed using an electric melting separate furnace, but from the viewpoint of carbon neutrality, for example, limestone or dolomite can be added after hot charging of the electric melting separate furnace to form slag, the slag basicity is controlled to be between 1.0 and 1.2, and biomass carbon is sprayed to perform direct reduction iron deep reduction and molten iron carburization. After completing the final reduction and slag-iron melting separation, molten iron and slag are obtained.

[0060] The molten iron produced by the electric melting separate furnace can be used in a converter to produce various high-quality steel materials, and the slag can be comprehensively utilized as mineral wool, slag powder, and microcrystalline glass raw materials.

[0061] <Carbon neutrality, tail gas and waste heat treatment>

[0062] The cooling reduction metallization briquetting method and the method for producing molten iron of the present application can be low-carbon or zero-carbon emission throughout the entire production process.

[0063] In addition, as described above, the cooling reduction metallization briquetting method and the method for producing molten iron of the present application make full use of the heat of high-temperature pellets, and creatively perform direct reduction of ammonia at a high shaft furnace temperature, thereby reducing heat consumption by avoiding repeated heating and cooling, shortening the reduction time, and reducing other costs.

[0064] Further, in the method process of the present application, the top gas in the shaft furnace is used for waste heat recovery, washing, and pressure swing adsorption to remove ammonia, H2O, and nitrogen, hydrogen is recycled back to the reducing gas, and ammonia dissolved in water is recycled. For example, the waste heat can be used for waste heat of the pellets in the pellet manufacturing process. The carbon-containing exhaust gas in the carburization process can be supplemented with oxygen combustion, and the heat can be used for waste heat utilization.

[0065] Therefore, the cooling reduction metallization briquetting method and the method for producing molten iron of the present application are suitable for low-carbon emission requirements, reduce industrial emissions, greatly reduce energy consumption, are environmentally friendly, have excellent sustainability, and are a metallization briquetting method and a method for producing molten iron that meet the requirements of new era industrialization.

[0066] As a typical example, reference is made to Figure 1 In actual factory production, the device implementing the present application includes three parts, a chain grate-kiln roasting / belt roaster system, a reduction shaft furnace, and an electric melting separate furnace, and the main functions realized by each set of equipment are as follows:

[0067] 1) Iron ore concentrate is finely ground by a conventional process, and after bentonite is added, the green balls are pelletized, dried, preheated, and high-temperature roasted in a chain grate-rotary kiln or a belt roaster, and the high-temperature pellets are pneumatically transported by a chain plate machine or a high-temperature resistant pipeline to a reduction shaft furnace, and the circular cooler or the cooling section is cancelled.

[0068] 2) After the high-temperature pellets enter the charging system of the shaft furnace, high-temperature steam or nitrogen is first introduced to control the oxygen content in the gas phase in the material layer to be less than 1%, and then the material layer is pressurized to 0.3-0.7 MPa in the middle material tank, and then introduced into the lower material tank and enters the reduction shaft furnace, and the pressure in the shaft furnace is controlled to be between 0.3-0.7 MPa, and at this time the temperature of the pellets is between 1080-1250℃. After the ammonia gas is introduced into the middle part of the shaft furnace, the temperature of the gas is controlled to be between 800-900℃, and the high-temperature pellets rapidly react with the ammonia gas, and the temperature gradually decreases. The reduction time is controlled to be 1-1.5h, and the metallization rate of the pellets after cooling and reduction is controlled to be between 82-99%. The lower part of the shaft furnace is a pellet cooling section, and biomass biogas is introduced for carburizing and cooling, and the metallized pellets are reduced from 800-900℃ to about 500℃, and the C content is controlled to be between 1-3%. The iron elements in the pellets are mainly metallic iron, iron carbide and iron nitride, and there is a small amount of unreacted FeO.

[0069] 3) The hot metallized pellets (about 500℃) are subjected to hot state screening to remove the powder smaller than 5mm, which is returned to the previous pellet preparation process for reuse, and the metallic pellets larger than 5mm are transported to an electric smelting furnace by a sealed pneumatic conveying system, and biomass carbon, limestone, etc. are added in the electric smelting furnace to complete the final reduction and slag-iron separation, and obtain molten iron and slag.

[0070] 4) The zero-carbon molten iron is used for a converter, and the slag is finely ground to obtain slag powder or used as a raw material for mineral wool and microcrystalline glass, and high-value utilization is obtained.

[0071] Embodiment

[0072] The application is further described below in combination with embodiments.

[0073] Embodiment 1:

[0074] 80% hematite and 20% magnetite are respectively finely ground to a specific surface area ≧1500cm 2 / g (Blaine specific surface area), 0.8% bentonite, finely ground limestone, SiO2 content of pellets 3%, binary alkalinity of pellets adjusted to 1.2, that is, CaO content 3.6%, after pelletizing, screening, 8-20mm green pellets enter the chain grate machine - rotary kiln / or belt roaster, after drying, preheated at 950 ° C for 15 minutes, and then roasted at 1280 ° C for 30 minutes, the hot pellets enter the vertical furnace, the upper sealed tank is replaced with 200 ° C hot steam, after the oxygen content reaches 0.8%, it enters the middle sealed tank, nitrogen is pressurized to 0.5MPa, enters the lower sealed tank, and then enters the vertical furnace. At this time, the pellet temperature is about 1200 ° C. The ammonia is heated to 900 ° C and passed into the vertical furnace for reduction. The pellets are reduced at 1200-900 ° C for 60 minutes, and the ammonia consumption is 600Nm 3 / tDRI, then 80Nm 3 / tDRI biomass biogas was cooled and carburized, resulting in a DRI metallization of 95% and a carbon content of 2.3%. The hot DRI was smelted in an electric smelting furnace at 500°C, with 40kg of biomass carbon injected. The smelting time was 60 minutes, resulting in molten iron with a carbon content of 3%, a silicon content of 0.3%, and a sulfur content of 0.03%. The smelting furnace power consumption was 780kWh / tHM.

[0075] Example 2:

[0076] 60% hematite and 40% magnetite were finely ground to a specific surface area of ​​1500 cm 2 / g (Blaine specific surface area), 0.8% bentonite, finely ground limestone, SiO2 content of pellets 6%, binary alkalinity of pellets adjusted to 0.3, that is, CaO content 1.8%, after pelletizing, screening, 8-20mm green pellets enter the chain grate machine - rotary kiln / or belt roaster, after drying, preheated at 900 ° C for 15 minutes, and then roasted at 1230 ° C for 30 minutes, the hot pellets enter the vertical furnace, the upper sealed tank is replaced with 200 ° C hot steam, after the oxygen content reaches 0.8%, it enters the middle sealed tank, nitrogen pressurized to 0.4MPa, enters the lower sealed tank, and then enters the vertical furnace. At this time, the pellet temperature is about 1180 ° C. Ammonia is heated to 850 ° C and passed into the vertical furnace for reduction. The pellets are reduced at 1180-850 ° C for 80 minutes, and the ammonia consumption is 650Nm 3 / tDRI, then 70Nm 3 / tDRI biomass biogas was used for cooling and carburizing, resulting in a DRI metallization ratio of 85% and a carbon content of 2.0%. The hot DRI was smelted in an electric smelting furnace at 500°C. Limestone was added to adjust the slag basicity to 1.2, and 80kg of biomass carbon was injected. The smelting time was 70 minutes, resulting in molten iron with a carbon content of 2.8%, a silicon content of 0.3%, and an S content of 0.035%. The temperature was 1500°C, and the power consumption of the smelting furnace was 800kWh / tHM.

[0077] Example 3:

[0078] 40% hematite, 30% limonite and 30% magnetite were finely ground to a specific surface area of ​​1500 cm 2 / g (Blaine specific surface area), 0.8% bentonite, finely ground limestone, SiO2 content of pellets 5%, binary alkalinity of pellets adjusted to 0.7, that is, CaO content 3.5%, after pelletizing, screening, 8-20mm green pellets enter the chain grate machine - rotary kiln / or belt roaster, after drying, preheated at 900 ° C for 20 minutes, and then roasted at 1250 ° C for 30 minutes, the hot pellets enter the vertical furnace, the upper sealed tank is replaced with 200 ° C hot steam, after the oxygen content reaches 0.8%, it enters the middle sealed tank, nitrogen is pressurized to 0.7MPa, enters the lower sealed tank, and then enters the vertical furnace. At this time, the pellet temperature is about 1200 ° C. The ammonia is heated to 800 ° C and passed into the vertical furnace for reduction. The pellets are reduced at 1200-800 ° C for 90 minutes, and the ammonia consumption is 700Nm 3 / tDRI, then 80Nm 3 / tDRI biomass gas is cooled and carburized to obtain a DRI metallization rate of 88% and a C content of 2.8%. The hot DRI temperature is 500℃ and enters the electric smelting furnace for smelting. Limestone is added to adjust the slag basicity to 1.0. 75kg of biomass carbon is sprayed in. The smelting time is 80min, and the obtained molten iron has a carbon content of 3.5%, a silicon content of 0.4%, and an S content of 0.05%. The temperature is 1510℃. The power consumption of the smelting furnace is

[0079] The results of the above examples demonstrate that the ammonia-cooling reduction metallization agglomeration method and hot metal production method of the present invention can utilize existing equipment, achieve a short reduction time, a high pellet metallization ratio, and produce hot metal compositions that meet process requirements. Therefore, the present invention offers a simple process flow and can produce metal agglomerates and hot metal that meet industrial requirements with high efficiency, low energy consumption, and low carbon emissions, thus possessing extremely high industrial value.

Claims

1. An ammonia cooling reduction metallization agglomeration method, characterized in that: It comprises: Pellet manufacturing process: manufacturing green pellets of iron oxide-containing ore, and obtaining oxidized pellets by oxidizing roasting at a temperature of 1180-1300°C; Reduction process: without cooling, the oxidized pellets obtained in the pellet manufacturing process are directly deoxidized and pressurized by a conveying system and a feeding system, and then are added into a reduction section of a shaft furnace, the temperature of the pellets entering the feeding system is 1080-1250°C, ammonia gas heated to 780-920°C is introduced into the reduction section of the shaft furnace, and the pellets are reduced by the ammonia gas to obtain metallized pellets; and carburizing process: a carburizing section is arranged below the reduction section of the shaft furnace, a carbon-containing gas is introduced into the carburizing section for cooling and carburizing, and a metallic briquette of direct reduced iron (DRI) is obtained through a discharging system.

2. The ammonia-cooled reduced metal compacting method according to claim 1, wherein, The time of the reduction process is 50-100 minutes, and the metallization rate of the metallized pellets in the reduction process is 82-99%.

3. The ammonia-cooled reduced metal compacting method according to claim 1, wherein, In the reduction process, after the pellets enter an upper tank of the feeding system, heated steam and / or nitrogen gas is introduced to control the oxygen content in the gas phase in the material layer to be less than 1%, then the material layer is pressurized to 0.2-0.8 MPa in a middle tank, and then is introduced into a lower tank and enters the shaft furnace with a pressure of 0.2-0.8 MPa, and the temperature of the pellets when entering the shaft furnace is 1080-1250°C.

4. The ammonia-cooled reduced metal compacting method according to any one of claims 1 to 3, wherein The volume ratio of other gases into the shaft furnace is less than 10% except ammonia gas, and the ammonia gas consumption is 580-720 Nm 3 / tDRI, the solid material temperature in the reduction section of the shaft furnace is 1250 or less and 780°C or more.

5. The ammonia-cooled reduced metal compacting method according to any one of claims 1 to 3, wherein In the pellet production process, one or more of magnetite, hematite and limonite with a Blaine specific surface area ≧ 1400 cm 2 / g pretreated by ball milling or high pressure roller milling, 0.7-1.5% bentonite is added, limestone is added to adjust the pellet CaO / SiO2 binary basicity to 0.2-1.3, green balls with a particle size of 8-20 mm are obtained by a balling machine, the green balls enter a chain grate-kiln / or belt-type indurating machine, drying and preheating is performed; then it enters the induration section, the preheating temperature is 900-950°C, the time is 15-20 min, the induration temperature is 1180-1300°C, the indurated pellets are transported by a chain conveyor or a gas conveying system.

6. The ammonia-cooled reduced metal compacting method according to any one of claims 1 to 3, wherein In the carburizing process, as the carbon-containing gas, the biomass biogas is introduced for carburizing and cooling, the metallized pellets are lowered to 450-550℃, the C content is controlled between 1-3%, and the biomass biogas consumption is 60-90 Nm 3 / tDRI.

7. The ammonia-cooled reduced metal compacting method according to any one of claims 1 to 3, wherein The metallic briquette obtained in the carburizing process contains metallic iron, iron carbide, iron nitride, and 1-20% of ferrous oxide.

8. A method of producing molten iron, characterized by, It comprises the following processes: Metallized briquetting process: using the ammonia-cooled reduction metallized briquetting method according to any one of claims 1-7 to obtain a metallic briquette, and electric furnace melting process: adding the obtained metallic briquette into an electric melting furnace for melting to obtain molten iron.

9. The method of producing molten iron according to claim 8, wherein, After hot charging of the electric melting furnace, limestone and dolomite are added for slagging, the slag basicity is controlled to be 1.0-1.2, and biomass carbon is sprayed for deep reduction of direct reduced iron and carburizing of molten iron.

10. The method of producing molten iron according to claim 8 or 9, wherein, No carbon emission is generated in the production process of the molten iron.

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