Gas-based shaft furnace pre-reduction-electric smelting separation iron manufacturing process for medium-low-grade ore

Abstract

The invention provides a middle-low-grade iron ore gas-based shaft furnace pre-reduction-electric smelting separation zero-carbon iron manufacturing process, which comprises a middle-low-grade ore pretreatment process, a chain grate-rotary kiln roasting / or belt type roasting machine process, a shaft furnace pre-reduction process and an electric smelting separation furnace process, and is characterized in that the iron grade of middle-low-grade ore is 52-65%; the green pellets subjected to the pretreatment process enter a chain grate-rotary kiln to be roasted or a belt type roasting machine to be subjected to drying, preheating and high-temperature roasting, the steps of cooling through a cooling machine are omitted, in the shaft furnace pre-reduction process, hot pellets enter a feeding system, hot steam replacement is adopted for an upper hopper, after the oxygen content is lower than 1%, the hot pellets enter a middle hopper, nitrogen is pressurized to 0.3-0.7 MPa, and the hot pellets enter the middle hopper; the pellets enter a lower hopper, in the shaft furnace, the temperature of the pellets ranges from 1100 DEG C to 1220 DEG C, pure hydrogen or ammonia gas obtained after electric heating is introduced into the middle of the shaft furnace, and the gas temperature is controlled to range from 800 DEG C to 900 DEG C;

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steel metallurgy, and in particular to an iron-making process of medium and low grade ores. BACKGROUND

[0002] The steel process is mainly based on the blast furnace-converter long process, in which carbon is both a reducing agent and a heating agent, and more importantly, it plays an important role in the skeleton of the blast furnace smelting process, maintaining the permeability of the large blast furnace and ensuring the efficient progress of the gas-solid reaction. The metallurgical reaction process has the advantages of high efficiency, high energy utilization rate and large production capacity, providing a large amount of high cost-effective steel materials for social development. With the development of industrialization, industries represented by electricity, steel, and cement are continuously emitting carbon dioxide into the atmosphere, causing the greenhouse effect and exacerbating global climate anomalies. Countries have proposed plans to reduce carbon emissions.

[0003] The traditional high-efficiency low-cost blast furnace-converter process with high carbon emissions faces great technical challenges. The traditional process emits about 2 tons of carbon dioxide per ton of steel, and major steel companies and research institutions are researching and testing hydrogen metallurgy as an important technical direction for carbon neutralization in the steel process. Many university scholars have conducted a large number of laboratory studies on iron ore hydrogen reduction-electric furnace processes long ago, but have not yet applied industrialization. The main technical difficulties of this process need to be solved: 1) Large-scale, low-cost green hydrogen production process has not been broken through; 2) The problem of low heat transfer and utilization rate caused by endothermic hydrogen reduction has not been solved; 3) DRI production of high-end products such as automobile plates and silicon steel faces challenges in controlling S and nitrogen; 4) High-grade iron ore (TFe≧66%) is needed to ensure the high efficiency of the process, and the supply of this grade of iron ore accounts for only 3-5% of the total. Among the above four technical challenges, with the rapid development of green electricity and the progress of hydrogen production technology, green hydrogen is expected to make breakthroughs in the future. Hydrogen reduction endothermic and DRI production of high-quality steel, with the establishment of different scales of pilot plants, production demonstration lines by major steel companies, and industrial-scale research and exploration, are also expected to be solved. High-grade iron ore resources, relying on the progress of beneficiation technology, are expected to expand the resource quantity, but it is still difficult to meet market demand, and there are also a large number of highly dispersed and difficult-to-select ores that are difficult to obtain high-grade ore through beneficiation processes at a low cost.

[0004] Therefore, developing an iron-making process with wider resource adaptability and lower carbon emissions has become the pursuit of ironmakers in the new era. Many scholars have studied the use of medium and low grade ores.

[0005] Patent CN104056724B introduces "a hematite reverse flotation collector and its preparation and use method", which relates to a low-temperature hematite reverse flotation desilication anion collector suitable for upgrading and reducing impurities of medium and low grade iron concentrate, and a method for preparing and using the collector. The method can obtain iron concentrate with a grade of 56-58% and a recovery rate of 82-88% from raw ore with a Fe grade of 41.04%.

[0006] Patent CN114669395A introduces "a beneficiation process for low-grade fine-grained disseminated magnetite hematite", which can obtain high-grade concentrate with a grade of 68-69% and an iron recovery rate of 79-80% from magnetite hematite mixed ore with an iron grade of 26-28% through more than 10 processes such as coarse crushing, primary discarding, ore I crushing, secondary discarding, ore II crushing, fine grinding, coarse field strong magnetic separator roughing, coarse concentrate regrinding, desliming, and iron coarse concentrate weak magnetic separation.

[0007] Patent CN104785347B introduces "a separation method for high-silicon low-grade oxidized iron ore", which can obtain iron concentrate with a grade of 53.58% and a SiO2 content of 12% from raw ore with an iron grade of 41.04% through ball milling, strong magnetic roughing and two sweeping, three-stage grinding and three-stage weak magnetic separation, and finally obtaining a flotation concentrate, with a total process metal recovery rate of 70.9%.

[0008] Patent CN102784712B introduces "a beneficiation process for low-grade fine-grained disseminated difficult-to-concentrate iron ore", which can obtain iron concentrate with a grade of 63% and a recovery rate of 64% from raw ore with an iron grade of 28%, with the characteristics of small investment, simple maintenance, strong adaptability, and good fine grinding and desliming effect.

[0009] It can be seen that a large number of technical personnel have carried out a lot of effective work on how to improve the quality of medium and low grade ore through grinding and beneficiation. However, due to the characteristics of the ore itself, a part of the difficult-to-concentrate ore is difficult to improve the grade to the direct reduction quality (TFe≧66%, Al2O3+SiO2≦3%).

[0010] In the steel industry, a large amount of medium-grade iron ore (TFe 56-65%) is mainly reduced and slag-iron separated through sintering (pellet) process, blast furnace ironmaking, to obtain blast furnace molten iron for converter steelmaking. This process has the characteristics of large scale, low production cost, and wide resource adaptability, but the carbon emission per ton of steel reaches about 2t, and it is difficult to achieve process carbon neutralization relying on the process itself.

[0011] In addition, the conventional iron ore pelletizing, blast furnace ironmaking or shaft furnace direct reduction process is usually arranged in different areas, each pursuing the lowest energy consumption, and the production capacity is usually not matched, and it is difficult to solve the repeated heating, cooling and reheating process in different processes, and the energy saving technology at the interface between processes is easily ignored. For example, the annual production capacity of a single belt roaster or chain grate-rotary kiln-ring cooler oxidized pellet roaster is 5-6 million tons, but the annual pellet consumption of a single large blast furnace / shaft furnace is about 3-3.5 million tons, and the blast furnace with carbon as the reducing agent can compensate for the energy consumption of heating and protect the top equipment. The process with hydrogen as the reducing agent has high demand for heat and thermal energy, and if the high-temperature solid cannot compensate for the endothermic reduction, the hydrogen utilization rate will be low. Different processes have different requirements for heat throughout the process.

[0012] In view of the limitations of the above-mentioned schemes, the present application mainly solves the problems of low hydrogen utilization rate, long process, high energy consumption, low metallization rate, poor adaptability of raw material resources, and high difficulty in producing high-quality steel materials from high-grade DRI in an electric furnace. A low-grade ore gas-based shaft furnace pre-reduction-electric melting separate ironmaking process is developed. SUMMARY

[0013] The technical problems to be solved by the present application are the problems of low hydrogen utilization rate, long process, high energy consumption, low metallization rate, poor adaptability of raw material resources, and high difficulty in producing high-quality steel materials from high-grade DRI in an electric furnace. In order to solve the above technical problems, the present application adopts the following technical scheme.

[0014] [1] A low-grade ore gas-based shaft furnace pre-reduction-electric melting separate ironmaking process, characterized in that it comprises a low-grade ore pretreatment process, a chain grate-rotary kiln roasting / belt roaster process, a shaft furnace pre-reduction process, and an electric melting separate furnace process,

[0015] The iron grade of the low-grade ore is 52-65%,

[0016] The green balls after the pretreatment process enter the chain grate-rotary kiln roaster / or belt roaster for drying, preheating and high-temperature roasting, and the cooling step of the cooler is cancelled, and the obtained high-temperature pellets are transported to the reduction shaft furnace,

[0017] In the shaft furnace pre-reduction process, the high-temperature pellets enter the feeding system, the upper hopper is replaced by hot steam, and after the oxygen content is lower than 1%, it enters the middle hopper and is pressurized to 0.3-0.7 MPa, and enters the lower hopper. In the shaft furnace, the pellet temperature is between 1100-1220℃, pure hydrogen or ammonia gas after electric heating is introduced into the middle part of the shaft furnace, and the gas temperature is controlled between 800-900℃, and the metallized pellets are obtained.

[0018] [2] The low-grade ore gas-based shaft furnace pre-reduction-electric melting separate iron process according to [1] above, characterized in that the consumption of hydrogen in the shaft furnace pre-reduction process is 600-650 Nm 3 / tDRI, or the consumption of ammonia is 400-460 Nm 3 / tDRI.

[0019] [3] The low-grade ore gas-based shaft furnace pre-reduction-electric melting separate iron process according to [1] above, characterized in that the electric heater for electric heating of the pure hydrogen or ammonia adopts an indirect heating mode, the hydrogen or ammonia flows between the high-temperature-resistant alloy sleeves, and is heated to 800-900℃.

[0020] [4] The low-grade ore gas-based shaft furnace pre-reduction-electric melting separate iron process according to [1] above, characterized in that the lower part of the shaft furnace is a pellet cooling section, and is permeated with biomass biogas or pyrolysis gas for carburization and cooling, the metallized pellets are reduced from 800-900℃ to 400-700℃, and the C content is controlled to be between 1-3%.

[0021] [5] The low-grade ore gas-based shaft furnace pre-reduction-electric melting separate iron process according to [1] above, characterized in that the metallized pellets cooled in the shaft furnace are subjected to hot-state screening, and the metallized powder with a particle size less than 5mm is removed, and the metallized pellets with a particle size more than 5mm are added to the electric melting separate furnace through a closed pipeline, low-ash anthracite, coke or biomass carbon, and / or quicklime powder are sprayed into the electric melting separate furnace, the final reduction and slag-iron separation are completed, and the molten iron and slag are obtained.

[0022] [6] The low-grade ore gas-based shaft furnace pre-reduction-electric melting separate iron process according to [1] above, characterized in that the spraying holes of the electric melting separate furnace are arranged at the bottom and the side of the electric melting separate furnace, and the powder is stirred after being sprayed.

[0023] The low-grade ore gas-based shaft furnace pre-reduction-electric melting separate iron process can be applied to raw material resources with an iron grade of 52-65%, and compared with the prior art, the hydrogen utilization rate is high, the process is short, the energy consumption is low, and the metallization rate is high, so it is a new process for the collaborative production of zero-carbon molten iron by biomass-hydrogen / ammonia-electricity. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a low-grade ore gas-based shaft furnace pre-reduction-electric melting separate iron process flow diagram of the present application.

[0025] Figure 2 is a temperature change comparison diagram of the present application and the traditional iron ore hydrogen reduction-electric furnace short process. DETAILED DESCRIPTION

[0026] In order to better understand the above technical solutions of the present disclosure, the technical solutions of the present disclosure are further described below in combination with the drawings and examples.

[0027] The low-grade ore gas-based shaft furnace pre-reduction-electric melting iron-making process of the present application comprises a low-grade ore pretreatment process, a chain grate-rotary kiln roasting process / or a belt roasting machine process, a shaft furnace pre-reduction process, and an electric melting furnace process. The following are described respectively.

[0028] (1) Pretreatment process

[0029] The pretreatment process of iron ore refers to the production process of obtaining concentrate meeting smelting requirements through various operations and processing of mined iron ore. It mainly includes: ore crushing and screening by a crusher and a vibrating screen, ore grinding and classification by a ball mill and a classifier; mineral separation, such as gravity separation, flotation, and electric separation; and mineral dehydration, including concentration, filtration, and drying production processes.

[0030] In the pretreatment process of the present application, the low-grade iron ore is crushed and finely ground, and the particle size is controlled at about 80% of -0.074 mm, the Blaine specific surface area is above 1500 cm 2 / g, and the concentrate moisture is controlled at a level below 2-3%. For easy-to-filter ore with low hydrophilicity, a ceramic filter or plate-and-frame filter press is directly used. For difficult-to-filter ore with high aluminum content or good hydrophilicity, when the moisture cannot be well controlled by a single filtration process, a microwave or electric heating method is used to adjust the concentrate moisture to below 2-3%.

[0031] In the present application, the low-grade ore refers to iron ore with an iron grade of 52-65%, represented by TFe 52-65%, and more preferably 52-62%. The iron ore type can be magnetite, hematite, limonite, and other common types of iron-making ore.

[0032] A small amount of bentonite or organic binder and 2-3% water are added to the concentrate thus obtained for pelletizing. The specific process is as follows: one or more of the pretreated magnetite, hematite, and limonite with a Blaine specific surface area ≥ 1500 cm 2 / g are mixed to obtain an iron ore raw material, then bentonite is added, and finely ground limestone or slaked lime is added to obtain a mixture with a binary basicity (CaO / SiO2) of 0.3-0.5 or 0.8-1.2, wherein the amount of bentonite added is 0.7-1.5 wt% of the iron ore raw material, the binary basicity of the mixture is adjusted by finely ground limestone or slaked lime, and needs to be determined according to the actual use; then an appropriate amount of water is added, and the disc pelletizer or drum pelletizer is used to pelletize to obtain iron-containing green balls with a particle size of 8-20 mm.

[0033] (2) Chain grate-rotary kiln roasting process / or belt roasting machine process

[0034] In the grate-kiln roasting / or belt roaster process of the present application, the green balls obtained from the pelletizing in the pretreatment process enter the grate-kiln roaster or belt roaster for drying, preheating, high-temperature roasting, and the pellets after roasting in this stage are not cooled, i.e. the process of cooling in the annular cooler is cancelled, and the obtained high-temperature pellets are transported to the reduction shaft furnace. The temperature of the high-temperature pellets is above 1250℃, and the high-temperature pellets are pneumatically transported to the reduction shaft furnace through the chain plate machine or high-temperature resistant pipeline.

[0035] The specific process is as follows: the iron-containing green balls prepared in process (1) are distributed to the grate system 18 through a conventional distribution device, an iron-containing green ball layer is obtained, and the total height of the layer is 250-400mm; then the green ball layer sequentially passes through the drying I section, the drying II section, the preheating I section and the preheating II section of the grate system 18, and the preheated pellets are obtained through blast drying, suction drying, primary preheating and secondary preheating; then the preheated pellets are roasted in the rotary kiln system 16 by using the combustion of combustibles by the burner to provide heat, and the roasted pellets are obtained.

[0036] The blast drying is carried out in the drying I section, the hot exhaust gas from the preheating I section is introduced into the iron-containing green balls from the bottom of the layer through the second regenerative air blower 15, the blast drying temperature is controlled to be 170-240℃, preferably 190-210℃, the air speed is 0.8-1.4m / s, preferably 0.9-1.2m / s, and the drying time is 1.5-2.5min.

[0037] The suction drying is carried out in the drying II section, the hot exhaust gas from the preheating II section is introduced above the layer by the first regenerative air blower 14, the suction drying temperature is adjusted according to the bursting temperature of the green balls and is controlled to be lower than the bursting temperature of the pellets, the suction drying temperature is 300-400℃, preferably 330-350℃, the air speed is 0.8-1.4m / s, preferably 0.9-1.2m / s, and the drying time is 4-6min.

[0038] The primary preheating is carried out in the preheating I section, the hot air is obtained by indirect heat exchange between air and flue gas after reduction reaction through the tubular heat exchanger 235 of the reduction gas system 23, the primary preheating temperature is 600-800℃, the air speed is 0.8-1.4m / s, preferably 0.9-1.2m / s, and the primary preheating time is 4-6min.

[0039] The secondary preheating is carried out in the preheating II section, the hot air comes from the hot exhaust gas generated by the rotary kiln roasting, the secondary preheating temperature is controlled to be 900-1100℃, the air speed is 0.8-1.4m / s, preferably 0.9-1.2m / s, and the preheating time is 4-6min.

[0040] The roasting is carried out in the rotary kiln system 16, and the heat is provided by the combustion of fuel at the burner, wherein the fuel can be combustible oil or combustible gas, including natural gas, coke oven gas, cracking gas, pyrolysis oil, biomass oil or biomass carbon, and the fuel is preferably a gas from a non-fossil energy source such as cracking gas, pyrolysis oil or biomass oil, and hot air is used for combustion to increase the combustion temperature, wherein the hot air is from a mixture of air and hot waste gas from the preheating stage I, the roasting temperature is controlled to be above 1250°C, the roasting time is 30-40 min, and the cold compressive strength of the roasted pellets is ≥2200N / pellet.

[0041] In the grate system 18, after the iron-containing green balls are dried by blast drying and suction drying, the waste gas passes through the main suction fan 11, the bag filter 12 and the dust removal, desulfurization and denitrification system, meets the ultra-low emission standard, and is discharged through the chimney 13.

[0042] The grate-kiln oxidized pellet system 1 used in the process comprises the grate system 18 and the rotary kiln system 16 connected to the grate system 18, and is used for sequentially drying, preheating and high-temperature roasting the iron-containing green balls.

[0043] In combination Figure 1 As shown in the figure, the grate system 18 sequentially dries and preheats the iron-containing green balls to obtain preheated pellets. The grate system 18 is provided with a drying stage I, a drying stage II, a preheating stage I and a preheating stage II in sequence along the movement direction of the green balls. The preheating stage II is connected in communication with the rotary kiln system 16. The preheating stage II is connected with the drying stage II through the first heat recovery fan 14. The preheating stage I is connected with the tube heat exchanger 235 of the reducing gas system 23. The preheating stage I is connected with the rotary kiln system 16 through the combustion air fan 17 and is connected with the drying stage I through the second heat recovery fan 15. The drying stage I and the drying stage II are connected with the bag filter 12 through the main suction fan 11. The rotary kiln system 16 is used for high-temperature roasting of the preheated pellets in the grate system 18. The rotary kiln system 16 uses the combustion of fuel at the burner to provide the heat required in the high-temperature roasting process. The roasted pellets obtained in the grate-kiln oxidized pellet system 1 are transported to the feeding system of the hydrogen-based shaft furnace reduction system 2 through the high-temperature resistant hopper.

[0044] (3) Shaft furnace pre-reduction process

[0045] The pre-reduced pellets after roasting enter a hydrogen-based shaft furnace reduction system, and a reduction reaction occurs with a reduction gas, and then the pre-reduced pellets after cooling treatment are obtained: the pre-reduced pellets after roasting enter the upper feeding system 21 of the hydrogen-based shaft furnace reduction system 2 through a high-temperature resistant hopper, and then enter the hydrogen-based shaft furnace 22 of the hydrogen-based shaft furnace reduction system 2 through the upper feeding system 21, and the reduction reaction occurs in the middle part of the hydrogen-based shaft furnace 22, and the pre-reduced pellets after cooling treatment are obtained after the cooling treatment in the lower part of the hydrogen-based shaft furnace 22. The flue gas after the reduction reaction enters the reduction gas system 23 from the flue gas outlet at the top of the hydrogen-based shaft furnace 22, and then enters the middle part of the hydrogen-based shaft furnace 22 through the reduction gas system 23 after heat exchange, waste heat recovery and washing to participate in the reduction reaction; the mixed gas after the cooling treatment enters the cooling system 24 from the gas outlet at the lower part of the hydrogen-based shaft furnace 22, and then the pre-reduced pellets are obtained through the cooling system 24 after waste heat recovery and washing.

[0046] In the shaft furnace pre-reduction process, the high-temperature pellets enter the upper feeding system, the upper hopper is replaced by hot steam, and after the oxygen content is less than 1%, the pellets enter the middle hopper and are pressurized to 0.3-0.7 MPa, and then enter the lower hopper. In the shaft furnace, the temperature of the pellets is between 1100-1220℃, pure hydrogen or ammonia gas heated by electricity is introduced into the middle part of the shaft furnace, and the gas temperature is controlled between 800-900℃, and the metallized pellets are obtained.

[0047] Specifically, in the shaft furnace pre-reduction process, after the high-temperature pellets enter the upper feeding system of the shaft furnace, 200℃ high-temperature steam / nitrogen is introduced to control the oxygen content in the gas phase in the material layer to be less than 1%, and then the pellets enter the middle hopper and are pressurized to 0.3-0.7 MPa, and then the pellets enter the lower hopper and enter the reduction shaft furnace. The pressure in the shaft furnace is controlled between 0.3-0.7 MPa, and the temperature of the pellets is between 1100-1220℃. Pure hydrogen or ammonia gas heated by electricity is introduced into the middle part of the shaft furnace, and the gas temperature is controlled between 800-900℃. The high-temperature pellets rapidly react with hydrogen or ammonia gas, and the temperature gradually decreases. The reduction time is controlled between 1-1.5h, and the metallization rate of the pellets after cooling reduction is controlled between 80-90%. The lower part of the shaft furnace is a pellet cooling section, and biomass biogas or pyrolysis gas is introduced for carburizing and cooling. The metallized pellets are reduced from 800-900℃ to 400-700℃, and the C content is controlled between 1-3%. The iron elements in the pellets are mainly metallic iron, iron carbide and iron nitride, and there are 11-22% FeO.

[0048] In the shaft furnace pre-reduction process, the consumption of hydrogen is 600-650 N m 3 / tDRI, or the consumption of ammonia gas is 400-460 N m 3 / tDRI.

[0049] The electric heater for electrically heating the pure hydrogen or ammonia gas adopts an indirect heating mode, the hydrogen or ammonia gas flows between the high-temperature alloy sleeve pipes, and is heated to 800-900 DEG C. The specific structure is a metal resistance rod, which is sleeved with a high-temperature alloy sleeve pipe, and no filler is arranged between the resistance rod and the inner wall of the high-temperature alloy sleeve pipe, so that the heat transfer efficiency is improved. A plurality of groups of the resistance rod high-temperature alloy sleeve pipes are integrated, and then are packaged into a high-temperature alloy cylinder, wrapped with refractory, and then wrapped with a stainless steel shell.

[0050] (4) Electric smelting separation furnace process

[0051] In the electric smelting separation furnace process of the present application, the metallized pellets cooled in the shaft furnace are subjected to hot state screening, and the metal powder with a particle size less than 5 mm is removed, and the metallized pellets with a particle size more than 5 mm are added into the electric smelting separation furnace, low-ash anthracite, coke or biomass carbon, and / or quicklime powder are sprayed into the electric smelting separation furnace, the final reduction and slag-iron separation are completed, and the molten iron and slag are obtained.

[0052] Preferably, the electric smelting separation furnace can adopt a semi-submerged arc operation mode, which matches the electric conductivity of the metal furnace charge, and uses the electric arc and resistance to jointly heat, so that the reaction temperature required for slag-iron separation is reached. The gas permeable bricks are arranged below the slag line and at the bottom of the side of the electric smelting separation furnace, the anthracite powder, biomass carbon powder, quicklime powder and the like can be sprayed through the gas holes of the gas permeable bricks, the molten pool stirring is strengthened, the carbonization and desulfurization effects of the molten iron are promoted, the final reduction and slag-iron separation are completed, and the molten iron and slag are obtained. The composition of the molten separation furnace iron is equivalent to that of the blast furnace.

[0053] In addition, the metallized pellets with a particle size more than 5 mm can be introduced into the electric smelting separation furnace through a closed pipeline.

[0054] The molten iron obtained is used in a converter or an electric furnace, the slag is finely ground to obtain slag powder or is used as a raw material for mineral wool and microcrystalline glass, and high value utilization is achieved.

[0055] The electric smelting separation furnace process of the present application has the following advantages:

[0056] 1. The grinding, filtering and drying system is used to pretreat the medium and low grade ore, so that the particle size and moisture content meet the requirements of pelletizing. Since the reduction relies on hydrogen or ammonia, there is no influence of ash brought by traditional coal-based fossil fuels, the grade of iron ore can be between 52-65%, which is lower than that in the traditional blast furnace-converter process, and is much lower than that in the traditional gas-based shaft furnace-electric furnace process. In the iron ore, the contents of silicon, aluminum and sulfur can be higher than those in the conventional blast furnace pellets, and the resource adaptability is wider. Moreover, the electric smelting separation furnace has a short column, a small amount of gas in the furnace, and a lower requirement for gas permeability, so that a larger amount of slag can be smelted.

[0057] 2. High-temperature briquetting and high-temperature reduction processes are seamlessly connected, and the mature grate-kiln production device / or belt-type roaster and the most efficient shaft furnace are used to organically combine the oxidized pellet roasting process with the pellet cooling reduction, and the pellet cooling and direct reduced pellet heating processes are cancelled. After the shaft furnace reduction and carburization, the DRI is hot-charged to the electric melting furnace, the process is more concise, and the energy utilization efficiency is higher.

[0058] 3. The physical heat of the high-temperature pellets is fully utilized to meet most of the heat required for hydrogen reduction, so that the hydrogen / ammonia reduction thermodynamic conditions are more reasonable, the reduction time is greatly shortened, and the reduction utilization rate is greatly improved.

[0059] 4. Hydrogen or ammonia is indirectly heated by a metal resistance rod external sleeve, which has a long service life and can avoid direct contact between impurity elements in the circulating gas and the heating element, thereby preventing corrosion and damage to the heating element.

[0060] 5. The pellet roasting process preferably uses non-fossil energy combustion such as cracking gas, pyrolysis oil, biomass oil, and biomass carbon, green electricity to drive equipment, pure hydrogen cooling reduction, and biomass biogas carburization to achieve low-carbon or zero-carbon process production of molten iron.

[0061] 6. The electric melting furnace adopts a semi-submerged arc operation mode that matches the electrical conductivity characteristics of the metal charge, uses an electric arc and resistance to heat together, reaches the reaction temperature required for slag-iron melting and separation, and sets gas permeable bricks below the side slag line and the bottom. Through the gas holes of the gas permeable bricks, anthracite powder, biomass carbon powder, and quicklime powder can be sprayed to strengthen the molten pool stirring and promote the carburization and desulfurization effects of the molten iron.

[0062] Embodiment

[0063] The application will be further described below in conjunction with the embodiments.

[0064] Reference Example 1:

[0065] 62% of hematite (TFe 64.4%) and 35% of limonite (TFe 61.5%) were finely ground to a specific surface area ≧1500 cm 2 / g (Blaine specific surface area), 1% bentonite is added, 2% finely ground limestone is added, the pellet Si02 content is 3.00%, the Al203 content is 1.94%, the TFe is 65.4%, the binary basicity is 0.37, after balling, screening is performed, the 8-20 mm green balls enter the grate-kiln / or belt induration machine, after drying, preheating is performed at 950°C for 15 min, then 1290°C is baked for 30 min, and cooling is performed for 60 min to room temperature, the energy consumption of the pellet preparation process per ton of product is 32 kgce / t. The cold-state oxidized pellets are then transported to a hydrogen-based shaft furnace, from entering the shaft furnace charging system to starting to heat up at the furnace top, to 800-900°C reduction, to a metallization rate of 92%, hydrogen utilization rate of 35% (H2 / (H2+H2O)*100% in the gas phase after the reaction), then carburization, and cooling to below 80°C, which takes 420 min, the DRI pellet consumption per ton is 1.43 t, the DRI product process energy consumption is 360 kgce / t. After the cold DRI is added to the electric furnace, it is heated and melted into molten steel, the product consumption per ton is 1.15 t, the smelting time is 70 min, the molten steel process energy consumption is 65 kgce / t, and then the total process energy consumption of the molten steel is calculated to be 65+1.15*360+1.15*1.43*32=531 kgce / t. The process time is 595 min, excluding the transportation of different states of materials.

[0066] Example 1:

[0067] 62% of the hematite (TFe 64.4%) and 35% of the limonite (TFe 61.5%) are finely ground to a specific surface area of ≧1500 cm 2 / g (Blaine specific surface area), 1% bentonite is added, 2% finely ground limestone is added, the pellet Si02 content is 3.00%, the Al203 content is 1.94%, the TFe is 65.4%, the binary basicity is 0.37, after balling, screening is performed, the 8-20 mm green balls enter the grate-kiln / or belt induration machine, after drying, preheating is performed at 950°C for 15 min, then 1290°C is baked for 30 min, and cooling is performed for 60 min to room temperature, the energy consumption of the pellet preparation process per ton of product is 32 kgce / t. The cold-state oxidized pellets are then transported to a hydrogen-based shaft furnace, from entering the shaft furnace charging system to starting to heat up at the furnace top, to 800-900°C reduction, to a metallization rate of 92%, hydrogen utilization rate of 35% (H2 / (H2+H2O)*100% in the gas phase after the reaction), then carburization, and cooling to below 80°C, which takes 420 min, the DRI pellet consumption per ton is 1.43 t, the DRI product process energy consumption is 360 kgce / t. After the cold DRI is added to the electric furnace, it is heated and melted into molten steel, the product consumption per ton is 1.15 t, the smelting time is 70 min, the molten steel process energy consumption is 65 kgce / t, and then the total process energy consumption of the molten steel is calculated to be 65+1.15*360+1.15*1.43*32=531 kgce / t. The process time is 595 min, excluding the transportation of different states of materials. 3 / t DRI, hydrogen utilization rate of 58%, then 70 Nm 3DRI biomass or biomass pyrolysis gas or natural gas cooling carburizing, carburizing time 20 min, DRI metallization rate of 90%, C content of 2.5%, tons of DRI pellets consumption of 1.43t, DRI process energy consumption in the reduction and carburizing stage is 280 kgce / t (minus the part of waste heat utilization). Hot DRI temperature is 500℃ into the electric melting furnace smelting, tons of product consumption of 1.15t, adding 72kg of limestone block or limestone powder, spraying 27kg of biomass carbon, smelting time is 50min, the carbon content is 3.08%, the silicon content is 0.13%, the S content is 0.005%, the P content is 0.12%, the temperature of the molten iron is 1520℃, the slag ratio is 140.5kg / tHM, the slag basicity is 1.2, the Al2O3 content in the slag is 20.3%, the MgO content is 7.8%, the electric melting furnace power consumption is 639kWh / tHM, the process energy consumption is 91kgce / t. Into the converter, smelting time is 30min, product consumption is 0.85t, product process energy consumption is-25kgce / t. Then the total energy consumption of molten steel of this process is 1*0.85*(-25)+0.85*91+0.85*1.15*280+0.85*1.15*1.43*45=393kgce / t. Processing the same grade of iron ore, the total energy consumption of this scheme is reduced by 26% compared with the conventional process, and the process time is 205min, which is shortened by 65% compared with the conventional process.

[0068] Example 2:

[0069] 45% of high-silicon hematite (TFe 56.0%) and 49% of limonite (TFe 61.5%) are respectively finely ground to a specific surface area≧1500cm 2 / g (Blaine specific surface area), 1% bentonite is added, 5% finely ground limestone is added, the TFe of the pellet is 60.3%, the SiO2 content is 8.9%, the Al2O3 content is 1.99%, the binary basicity is 0.3, after balling, screening is carried out, 8-20mm green balls enter the chain grate-rotary kiln / or belt type roaster, after drying, preheating at 950℃ for 18min, then roasting at 1250℃ for 40min, the product energy consumption of the oxidation roasting stage is 47kgce / t. After roasting, the hot pellets enter the feeding system, the upper hopper is replaced by 200℃ hot steam, after the oxygen content is lower than 1%, it enters the middle hopper, nitrogen is pressurized to 0.4MPa, it enters the lower hopper, then it enters the shaft furnace, at this time the pellet temperature is about 1180℃. Hydrogen or ammonia is electrically heated to 900℃, it is introduced into the shaft furnace for reduction, the pellets are reduced at 900-1180℃ for 80min, the hydrogen or ammonia consumption is 620, 450Nm 3 / tDRI, respectively, the hydrogen utilization rate is 56%, then 60Nm 3DRI biomass methane cooling carburizing, carburizing time 20 min, DRI metallization rate 85%, C content 2.5%, ton DRI pellet consumption 1.55 t, DRI process energy consumption in reduction and carburizing stage 260 kgce / t (minus part of waste heat utilization). Hot DRI temperature 600℃ into electric melting furnace smelting, ton product consumption 1.25 t, adding lime block or spraying lime powder 150 kg, adjusting slag basicity 1.2, spraying 75 kg biomass carbon, smelting time 70 min, obtaining carbon content 4.03%, silicon content 0.22%, S content 0.006%, P content 0.14%, temperature 1500℃ hot metal, slag ratio 380 kg / t HM, slag basicity 1.2, Al2O3 content 8.4%, MgO content 8.3%, melting furnace power consumption 766 kWh / t HM, process energy consumption 107 kgce / t. Into converter, smelting time 35 min, product unit consumption 0.85 t, product process energy consumption -26 kgce / t. Then the molten steel total energy consumption of the process is 1*0.85*(-26)+0.85*107+0.85*1.25*260+0.85*1.25*1.55*47=422 kgce / t, excluding transportation of different state materials, process time consumption is 263 min. Conventional hydrogen reduction, electric furnace process is limited by production efficiency, and cannot directly use the grade of iron ore.

[0070] Example 3:

[0071] 49% high-silicon hematite (TFe 56.0%) and 45% limonite (TFe 57.1%) are respectively finely ground to a specific surface area ≧1500 cm 2 / g (Blaine specific surface area), 1.0% bentonite is added, 5% finely ground limestone is added, the pellet TFe content is 58.8%, the SiO2 content is 10.6%, the Al2O3 content is 2.64%, the binary basicity is 0.25, after balling, screening is performed, 8-20 mm green balls enter the grate-kiln / or belt-type roaster, after drying, preheating at 900℃ for 20 min, and then roasting at 1250℃ for 35 min, the product energy consumption in the oxidation roasting stage is 46 kgce / t. After roasting, the hot pellets enter the feeding system, the upper hopper is replaced with 200℃ hot steam, after the oxygen content is lower than 1.0%, the pellets enter the middle hopper, nitrogen is pressurized to 0.7 MPa, and then the pellets enter the lower hopper and then enter the shaft furnace, at this time the pellet temperature is about 1200℃. Hydrogen or ammonia is heated to 800℃ and introduced into the shaft furnace for reduction, the pellets are reduced at 800-1200℃ for 90 min, the ammonia consumption is 650, 460 Nm 3 / t DRI, respectively, the hydrogen utilization rate is 53%, then 80 Nm 3The DRI biomass methane is cooled and carburized for 23 min, and the DRI metallization rate is 88%, the C content is 2.5%, the consumption of ton DRI pellets is 1.59 t, and the DRI process energy consumption in the reduction and carburization stage is 258 kgce / t (subtracting the part of waste heat utilization). The hot DRI at a temperature of 550°C enters the electric melting furnace for smelting, the consumption of ton product DRI is 1.24 t, 71 kg of quicklime is added, 39 kg of biomass carbon is sprayed, the smelting time is 80 min, the carbon content is 3.7%, the silicon content is 0.27%, the S content is 0.021%, the P content is 0.13%, the molten iron at a temperature of 1510°C is obtained, the slag ratio is 348 kg / tHM, the slag basicity is 0.61, the Al2O3 content in the slag is 12.5%, the MgO content is 5.5%, the electric melting furnace power consumption is 752 kWh / tHM, and the process energy consumption is 106 kgce / t. The product enters the converter, the smelting time is 35 min, the product consumption is 0.85 t, and the product process energy consumption is -26 kgce / t. Then the total molten steel energy consumption of the process is 1*0.85*(-26)+0.85*106+0.85*1.24*258+0.85*1.24*1.59*46=417 kgce / t, and the process time is 283 min after removing the transportation of materials in different states. The conventional hydrogen reduction and electric furnace process cannot directly use the iron ore of this grade due to the limitation of production efficiency.

[0072] Example 4:

[0073] 45% high-silicon hematite (TFe 56.0%) and 49% limonite (TFe 61.5%) are respectively finely ground to a specific surface area of ≧1500 cm 2 / g (Blaine specific surface area), 1% bentonite is added, 5% finely ground limestone is added, the TFe of the pellets is 60.3%, the SiO2 content is 8.9%, the Al2O3 content is 1.99%, and the binary basicity is 0.3. After pelletizing, screening is performed, the 8-20 mm green pellets enter the grate-kiln or belt-type roaster, are dried, are preheated at a temperature of 950°C for 18 min, and are then roasted at 1250°C for 40 min. The product energy consumption in the oxidation roasting stage is 47 kgce / t. The hot pellets enter the feeding system, the upper hopper is replaced by 200°C hot steam, the oxygen content is less than 1% after replacement, the pellets enter the middle hopper, nitrogen is pressurized to 0.4 MPa, the pellets enter the lower hopper, and then enter the shaft furnace. At this time, the pellet temperature is about 1180°C. Hydrogen or ammonia is electrically heated to 900°C, is introduced into the shaft furnace for reduction, the pellets are reduced at 900-1180°C for 80 min, and the hydrogen or ammonia consumption is 620, 450 Nm 3 / tDRI, respectively. The hydrogen utilization rate is 56%. Then 60 Nm 3The DRI biomass is cooled and carburized for 20 min to obtain a DRI metallization rate of 85%, a C content of 2.5%, and a consumption of 1.55 t of DRI pellets per ton, and the energy consumption of the DRI process in the reduction and carburization stage is 260 kgce / t (with the part of waste heat utilization deducted). The hot DRI at a temperature of 600℃ is fed into an electric smelting furnace for smelting, and the consumption of the hot DRI is 980 kg / tHM, while 320 kg / tHM of metal pellets at room temperature (with a metallization rate of 80% and a S content of 0.7%) produced by a rotary hearth furnace are added, the energy consumption of the rotary hearth furnace process is 240 kgce / t, the consumption of metal materials per ton of product is 1.30 t, 103 kg of quicklime blocks or quicklime powder is added, the slag basicity is adjusted to 1.2, 73 kg of biomass carbon is sprayed, the smelting time is 70 min, the C content is 3.92%, the Si content is 0.20%, the S content is 0.039%, the P content is 0.14%, the temperature of the molten iron is 1500℃, the slag ratio is 356 kg / tHM, the slag basicity is 1.2, the Al2O3 content is 8.8%, the MgO content is 9.8%, the electric consumption of the smelting furnace is 789 kWh / tHM, and the energy consumption of the process is 110 kgce / t. The molten iron is fed into a converter, the smelting time is 35 min, the consumption of the product is 0.85 t, and the energy consumption of the product process is -26 kgce / t. Therefore, the total energy consumption of the molten iron in the process is 1*0.85*(-26)+0.85*106+0.85*(0.98*260+0.32*240)+0.85*0.98*1.55*47=410 kgce / t, and the process time excluding the transportation of materials in different states is 263 min. The conventional hydrogen reduction and electric furnace process is limited by production efficiency and cannot directly use the iron ore and rotary hearth furnace metal pellets of the above-mentioned grade.

[0074] The results of the above-mentioned embodiments show that the low-grade ore gas-based shaft furnace pre-reduction-electric smelting ironmaking process of the present application can be applied to raw material resources with an iron grade of 52-65%, and compared with the prior art, the hydrogen utilization rate is high, the process is short, the energy consumption is low, and the metallization rate is relatively high, which is a new process for the coordinated production of zero-carbon molten iron by biomass-hydrogen / ammonia-electricity.

Claims

1. A process for producing direct reduced iron (DRI) and hot metal (HM) from low and medium grade ores and gaseous reductants in a shaft furnace, characterized in that, The process includes a low-grade ore pretreatment process, a chain grate-rotary kiln roasting process, a shaft furnace pre-reduction process, and an electric smelting furnace process, The iron grade of the low-grade ore is 52-65%, The green balls after the pretreatment process are dried, preheated, and high-temperature roasted in the chain grate-rotary kiln roasting process or the belt roaster process, and the step of cooling in a cooler is cancelled, and the obtained high-temperature pellets are transported to a reduction shaft furnace, In the shaft furnace pre-reduction process, the high-temperature pellets enter an upper hopper, are replaced by hot steam, and after the oxygen content is less than 1%, enter a middle hopper, are pressurized to 0.3-0.7 MPa, enter a lower hopper, and in the shaft furnace, the pellet temperature is between 1100-1220℃, pure hydrogen or ammonia gas after electric heating is introduced into the middle of the shaft furnace, the gas temperature is controlled between 800-900℃, and metallized pellets are obtained.

2. The process according to claim 1, characterized in that, In the shaft furnace pre-reduction process, the hydrogen consumption is 600-650 Nm 3 / tDRI, or the ammonia consumption is 400-460 Nm 3 / tDRI.

3. The process according to claim 1, characterized in that, The electric heater for electrically heating the pure hydrogen or ammonia gas adopts an indirect heating mode, the hydrogen or ammonia gas flows between high-temperature alloy sleeves, and is heated to 800-900℃.

4. The process for producing direct reduced iron from medium and low grade ores in a shaft gas based furnace as claimed in claim 1, wherein, The lower part of the shaft furnace is a pellet cooling section, biomass biogas or pyrolysis gas is introduced for carburizing and cooling, the metallized pellets are reduced from 800-900℃ to 400-700℃, and the C content is controlled between 1-3%.

5. The process for producing direct reduced iron from low grade ores in a shaft gas based furnace as claimed in claim 1, wherein, The metallized pellets after cooling in the shaft furnace are subjected to hot screening, the metal powder with a particle size less than 5mm is removed, the metallized pellets with a particle size greater than 5mm are added to an electric smelting furnace, low-ash anthracite, coke or biomass carbon, and / or quicklime powder are sprayed into the electric smelting furnace, the final reduction and slag-iron separation are completed, and molten iron and slag are obtained.

6. The process for prereduction-melted iron production in a shaft furnace with low-grade ore and gas according to claim 1, characterized in that, The electric smelting furnace spraying holes are arranged at the bottom and the side of the electric smelting furnace, and the powder is sprayed and stirred.

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