Iron ore magnetization roasting shaft furnace coal-based reduction method
By adding a pulverized coal injection device outside the reduction zone of the vertical shaft furnace, and using H2 and CO gases generated from the flue gas and pulverized coal of the vertical shaft furnace as reducing agents, the problem that existing vertical shaft furnaces can only use gaseous fuels has been solved, and the quality of iron ore magnetization roasting has been improved and the cost reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIUQUAN IRON & STEEL (GRP) CO LTD
- Filing Date
- 2026-04-16
- Publication Date
- 2026-06-30
AI Technical Summary
Existing vertical shaft furnace iron ore gas-based reduction processes can only use gaseous fuels with low CO or H2 content, which limits their application range and easily leads to problems such as over-reduction on the iron ore surface or under-reduction in the core.
A pulverized coal injection device is added outside the reduction zone of the vertical shaft furnace. The flue gas discharged from the vertical shaft furnace is used as the injection gas to inject pulverized coal into the reduction zone for high-temperature pyrolysis and carbon gasification reaction, generating H2 and CO gases as reducing agents. The concentration of reducing gas is controlled by adjusting the flue gas volume to prevent over-reduction.
This expands the application range of iron ore magnetization roasting shaft furnace, improves the quality of magnetization roasting, reduces production costs, and prevents over-reduction of iron ore.
Smart Images
Figure CN122303511A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of metallurgical and mineral engineering technology, and specifically relates to a method for coal-based reduction in a vertical shaft furnace for magnetized roasting of iron ore. Background Technology
[0002] The utilization of difficult-to-process low-grade iron ore mainly involves using strong magnetic separation or magnetized roasting-grinding-magnetic separation processes to produce iron concentrate. For difficult-to-process low-grade specular hematite, after grinding and magnetic separation using strong magnetic separation, the iron concentrate produced has a grade of 46-47% and a metal recovery rate of 66-67%. This product not only fails to meet the needs of blast furnace production but also results in significant metal waste during the beneficiation process. The magnetized roasting-grinding-magnetic separation process involves magnetizing the difficult-to-process low-grade iron ore in a vertical shaft furnace or rotary kiln, followed by grinding and magnetic separation. This produces an iron concentrate with a grade of 56-58% and a metal recovery rate of 83-85%. Due to the higher grade and metal recovery rate of iron concentrate produced by the magnetized roasting-grinding-magnetic separation process using vertical shaft furnaces or rotary kilns for difficult-to-process low-grade iron ore, it has been widely adopted in China.
[0003] A vertical shaft furnace is primarily used to process iron ore with a particle size greater than 15mm. The entire furnace consists of a feeding system at the top, the furnace body, a discharge system at the bottom, a water quenching system, and a flue gas dust removal and extraction system. Internally, the furnace is divided into four sections from top to bottom: a drying and preheating zone, a heating zone, a reduction zone, and a cooling zone. Upper and lower combustion chambers are located on the furnace walls on both sides, each equipped with multiple heating burners to increase the length of the heating zone. Multiple upper tilting beams in the preheating zone, middle tilting beams in the heating zone, and lower tilting beams in the reduction zone are located along the furnace width, allowing the iron ore to be tilted during its downward flow, improving the uniformity of heating quality. A reducing gas injection tower is located in the reduction zone of the vertical shaft furnace, positioned along the furnace length and divided into 3-6 injection zones. Each injection zone is supplied with reducing gas via a separate gas injection pipe. From a vertical cross-sectional perspective, the vertical shaft furnace is wider at the top, gradually narrowing downwards to its narrowest point at the heating zone (furnace waist), before gradually widening again to the bottom of the reduction zone. The main auxiliary equipment for the vertical shaft furnace includes roller-type ore dischargers installed along the length of the furnace body on both sides of the lower part of the reduction zone. These rollers are submerged in a water-sealed pool below their centerline and are primarily used to discharge roasted iron ore. Below the discharge rollers are a water quenching system and a conveyor. After being discharged from the rollers, the high-temperature roasted ore enters the water quenching pool for cooling and then settles onto the conveyor, which transports the roasted ore out of the pool. A charging trolley is located at the top of the vertical shaft furnace, with a funnel at its bottom. Exhaust pipes are located on both sides of the funnel, and corresponding waste gas bends connect to the exhaust pipes. After dust removal, the flue gas is extracted by a blower and discharged into the atmosphere. The iron ore remains in the vertical shaft furnace for 6-10 hours.
[0004] After being added from the top of the shaft furnace, the iron ore flows downwards under its own gravity, exchanging heat with the high-temperature flue gas flowing counter-currently upwards. After passing through the drying and preheating zones, the iron ore absorbs heat from the flue gas and undergoes further drying and heating. When the iron ore temperature rises to 400-600℃, the siderite contained within it decomposes and generates Fe3O4. When the high-temperature iron ore flows into the reduction zone of the shaft furnace and reaches a temperature of 500-850℃, reducing gas is injected from the reduction zone. This reducing gas flows upwards through the iron ore, and the limonite and hematite contained within it undergo a reduction reaction upon contact with the reducing gas, generating Fe3O4, thus reducing the iron ore. Therefore, the existing iron ore shaft furnace magnetized roasting process employs a gas-based reduction process.
[0005] Figure 1 This is a diagram of an existing gas-based reduction unit for a vertical shaft furnace used for magnetizing and roasting iron ore.
[0006] The drying, preheating, heating, reduction and cooling of the iron ore magnetization roasting vertical furnace process are completed in a rectangular vertical furnace. Although this iron ore gas-based reduction process is simple, compact and low-investment, it has many problems due to the inherent and insurmountable defects in theory: (1) The vertical furnace can only use gaseous fuels containing CO or H2 for iron ore magnetization roasting. Generally, blast furnace gas with low CO or H2 content or mixed gas with a small amount of coke oven gas is used. For areas without blast furnace gas or lacking blast furnace gas, the application of iron ore magnetization roasting vertical furnace is limited. (2) When the CO content in the reducing gas exceeds 30% or the H2 content exceeds 5%, it will cause the surface of the block iron ore to be over-reduced and the core to be under-reduced. The commonly used gas in enterprises, such as producer gas, coke oven gas and converter gas, are restricted from use because the CO content exceeds 30% or the H2 content exceeds 5%. Natural gas, whose main component is CH4, needs to be pyrolyzed at high temperature before use. This will crack the high molecular hydrocarbons in the natural gas into H2 or CO before it can be supplied to the vertical furnace as a reducing gas. However, its use is restricted because the H2 or CO content in the pyrolyzed gas is too high. Summary of the Invention
[0007] To address the problem that existing vertical shaft furnaces for iron ore gas-based reduction can only use gaseous fuels with low CO or H2 content, and to expand the application range of iron ore magnetized roasting vertical shaft furnaces, this invention provides a method for iron ore magnetized roasting vertical shaft furnace coal-based reduction.
[0008] Therefore, the present invention adopts the following technical solution: A method for reducing iron ore using a magnetized roasting shaft furnace with coal as the injection gas is disclosed. Based on the existing structure of the iron ore magnetized roasting shaft furnace, a pulverized coal injection device is added outside the reduction zone of the furnace without requiring an external supply of reducing gas. The pulverized coal injection device consists of a shaft furnace flue gas return pipe, a Roots blower, a pulverized coal feed port, a feed pipe, a main injection pipe, a branch pipe, an injection branch pipe, a partition plate, and a reducing coal injection tower. The partition plate, located inside the reducing coal injection tower, divides the reducing pulverized coal injection tower along the length of the furnace into 3-6 unconnected injection zones. 10-15% of the flue gas discharged from the shaft furnace is extracted from the main flue gas pipe and returned to the reduction system via the shaft furnace flue gas return pipe as injection gas. After being pressurized to 20-30 kPa by a Roots blower, the injected gas comes into contact with the pulverized coal added from the pulverized coal feed port. The injected gas can fluidize the pulverized coal into a gas-solid two-phase flow. The gas-solid two-phase flow flows into multiple injection branch pipes after passing through the main injection pipe and the branch pipe. Each injection branch pipe then transports the gas-solid two-phase flow to the corresponding injection zone and injects it into the reduction zone of the vertical furnace from the gas-solid two-phase flow injection outlet. In the gas-solid two-phase flow, pulverized coal absorbs heat from the high-temperature iron ore in the reducing zone, causing its temperature to rise rapidly. When the temperature rises from room temperature to 300℃, the adsorbed moisture and CO2 and CH4 gases in the pulverized coal are removed. When the temperature rises from 300℃ to 600℃, the macromolecular structure of the pulverized coal breaks down, releasing coal gas containing a large amount of hydrocarbons and tar, and the pulverized coal gradually becomes residual char. When the temperature rises from 600℃ to 1000℃, the residual char further condenses and releases a small amount of fuel gas. At the same time, the high-molecular hydrocarbons and tar in the coal gas are finally decomposed into H2 and CO gases under the high temperature in the furnace. When H2 and CO gases pass through the high-temperature iron ore bed, they can reduce the iron ore and generate H2O and CO2 gases. The generated H2O and CO2 gases then react with the carbon in the residual carbon to produce H2 and CO gases again. When the H2 and CO gases pass through the high-temperature iron ore bed, they reduce the iron ore again and generate H2O and CO2 gases. This continuous coupling reaction can continue as long as enough reducing coal powder is added to the iron ore and the iron ore magnetization roasting is not complete, the iron ore magnetization roasting reaction can continue, thereby improving the quality of iron ore magnetization roasting.
[0009] This invention adds a pulverized coal injection device to the outside of the reduction zone of the vertical shaft furnace. The pulverized coal injection rate is 2-5% of the weight of the iron ore, while the solid-to-gas ratio used for injecting pulverized coal into the flue gas returning from the vertical shaft furnace is 3-8 kg / Nm³. 3In production, the amount of pulverized coal used is adjusted according to the different iron ore compositions and the volatile matter content in the pulverized coal. When the volatile matter content in the pulverized coal is low, the amount of pulverized coal injected should be reduced. The solid-gas ratio used for injecting pulverized coal into the vertical shaft furnace return flue gas is adjusted according to the H2 and CO content in the reducing gas generated by pulverized coal cracking and carbon gasification reaction. When the H2 and CO content in the reducing gas is high, the extraction rate of the vertical shaft furnace return flue gas should be increased to control the CO content in the reducing gas of the vertical shaft furnace to not exceed 30% and the H2 content to not exceed 5%, thereby effectively preventing over-reduction in the iron ore magnetization roasting vertical shaft furnace.
[0010] The flue gas returned from the vertical furnace in this invention contains 13-17% CO2 gas. When the gas-solid two-phase flow is injected into the reducing coal injection tower, when the temperature of the pulverized coal rises to above 800°C, the CO2 gas in the flue gas will react with the carbon in the pulverized coal to generate CO gas. The CO gas can be used as a reducing gas to magnetize and roast the iron ore.
[0011] The pulverized coal used in this invention is high volatile coal with a particle size of less than 1 mm. The volatile matter content in the pulverized coal is 25-45%, the fixed carbon content is 41-65%, the ash content is 8-15%, and the softening temperature of the coal ash is higher than 1150℃.
[0012] In this invention, the reduction zone of the vertical shaft furnace is divided into 3-6 non-interconnected injection zones by a vertical partition plate. Each injection zone is equipped with a pipe, through which pulverized coal is injected separately into the corresponding injection zone. The pulverized coal injection device includes a vertical shaft furnace flue gas return pipe, a Roots blower, a pulverized coal feed port, a feed pipe, a main injection pipe, a branch pipe, an injection branch pipe, a partition plate, and a reducing coal injection tower. The vertical shaft furnace flue gas return pipe is connected to the inlet of the Roots blower, the bottom of the pulverized coal feed port is connected to the inlet of the feed pipe, the outlet of the Roots blower and the outlet of the feed pipe are respectively connected to the inlet of the main injection pipe, the main injection pipe is connected to the branch pipe, the branch pipe is connected to each injection branch pipe, and the partition plate is set inside the reducing coal injection tower, dividing the reducing coal injection tower into multiple injection zones along its length.
[0013] The principle of the coal-based reduction method for iron ore magnetization roasting shaft furnace of the present invention is as follows: 1. 10-15% of the flue gas discharged from the top of the vertical shaft furnace is extracted and returned to the reduction system as injection gas through the vertical shaft furnace flue gas return pipeline.
[0014] 2. After being pressurized to 20-30 kPa by a Roots blower, the injected gas comes into contact with the pulverized coal added from the pulverized coal feed port. The injected gas can fluidize the pulverized coal into a gas-solid two-phase flow. The gas-solid two-phase flow flows into multiple injection branch pipes after passing through the main injection pipe and the branch pipe. Each injection branch pipe then transports the gas-solid two-phase flow to the corresponding injection zone and injects it into the reducing coal injection tower from the gas-solid two-phase flow injection outlet.
[0015] 3. As the pulverized coal injected into the reducing coal injection tower falls freely within the tower, it comes into contact with the high-temperature furnace gas and high-temperature iron ore, which causes the temperature of the pulverized coal to rise rapidly. The volatile matter volatilized from the pulverized coal flows from bottom to top, and the residual carbon remaining after the volatile matter volatilizes falls into the high-temperature iron ore.
[0016] 4. When the temperature of pulverized coal rises from room temperature to 300℃, the moisture and CO2 and CH4 gases adsorbed in the pulverized coal are removed; when the temperature of pulverized coal rises from 300℃ to 600℃, coal gas containing a large amount of hydrocarbons and tar are released.
[0017] 5. When the temperature of pulverized coal rises from 600℃ to 1000℃, the high-molecular hydrocarbons and tar in the coal gas are eventually decomposed into H2 and CO gases under the high temperature in the furnace. When the H2 and CO gases pass through the high-temperature iron ore bed, they can reduce the iron ore and generate H2O and CO2 gases. The H2O and CO2 gases can also perform carbon gasification reaction on the carbon in the residual char, generating H2 and CO gases again. When the H2 and CO gases pass through the high-temperature iron ore bed, they can again reduce the iron ore and generate H2O and CO2 gases, continuously forming a coupled reaction. In this way, a large amount of H2O and CO2 gases will be continuously generated during the magnetized roasting process of iron ore, allowing the magnetized roasting reaction of iron ore to continue.
[0018] 6. After iron ore with a particle size of 15-50mm is added from the top of the vertical shaft furnace, the iron ore comes into contact with the high-temperature flue gas as it flows from top to bottom in the drying and preheating zone of the vertical shaft furnace. This allows the physical water and crystal water to be removed as the temperature of the iron ore rises to 300-400℃. When the temperature of the iron ore reaches 400-600℃, the siderite in the iron ore decomposes and generates Fe3O4.
[0019] 7. When the temperature of the iron ore rises to 600-850℃ and flows downward into the reduction zone of the vertical furnace, the iron ore and pulverized coal undergo pyrolysis and carbon gasification to generate H2 and CO gases. During the upward flow, the gases come into full contact, which allows the limonite and hematite in the iron ore to undergo a reduction reaction and generate Fe3O4.
[0020] 8. When the iron ore flows to the bottom of the reduction zone of the vertical furnace, the iron ore completes the magnetization roasting reaction.
[0021] 9. After the roasted iron ore is discharged from the bottom of the vertical furnace, in order to prevent secondary oxidation of the high-temperature roasted ore, the high-temperature roasted ore is cooled by water or by indirect oxygen-free cooling, so that the high-temperature iron ore is cooled to room temperature without oxidation.
[0022] The beneficial effects of this invention are as follows: 1. By adding a pulverized coal injection device outside the existing vertical shaft furnace reduction zone, a portion of the flue gas discharged from the vertical shaft furnace is used as the injection gas. The pulverized coal injection device injects high volatile pulverized coal into the reduction zone of the vertical shaft furnace. After the pulverized coal is heated in the furnace, it undergoes high-temperature pyrolysis and carbon gasification reaction to generate reducing gas containing H2 and CO, thereby enabling the vertical shaft furnace to perform magnetized roasting of iron ore without using gas-based reducing agents.
[0023] 2. By adjusting the proportion of flue gas drawn from the main flue gas pipe of the vertical shaft furnace, the concentrations of H2 and CO in the reducing gas produced by the pulverized coal injection device can be adjusted. This can effectively control the CO content in the reducing gas of the vertical shaft furnace to not exceed 30% and the H2 content to not exceed 5%, thus preventing over-reduction during the magnetized roasting of iron ore.
[0024] 3. This invention uses pulverized coal as a reducing agent in the iron ore magnetization roasting shaft furnace, which enables the iron ore magnetization roasting shaft furnace to be widely used in areas where gaseous reducing agents are scarce, thus expanding the application range of the iron ore magnetization roasting shaft furnace.
[0025] 4. In industrial production, under the same heat conditions, the cost of using a gaseous reducing agent is generally higher than that of using pulverized coal as a reducing agent. This invention reduces the production cost of iron ore vertical shaft furnace magnetization roasting. Attached Figure Description
[0026] Figure 1 This is a diagram of the existing gas-based reduction unit for the iron ore magnetization roasting shaft furnace; Figure 2 This is a front view of the iron ore magnetization roasting shaft furnace coal-based reduction device; Figure 3 This is a left view of a coal-based reduction device for iron ore magnetization roasting vertical furnace. Detailed Implementation
[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Given that existing vertical shaft furnaces for iron ore magnetization roasting can only use gaseous reducing agents, the following process is adopted to enable iron ore magnetization roasting in vertical shaft furnaces without the use of gas-based reducing agents: Standard comparison example: This implementation method is based on 100m 3 The following describes the use of a small vertical shaft furnace and high-temperature coke oven mixed gas to reduce iron ore.
[0028] 1. Material selection Difficult-to-process low-grade iron ore: The ore type is specular hematite (composed of hematite, limonite and siderite), with a particle size of 15-50mm and an iron grade of 33%; Both heating and reduction in the vertical furnace use high-coke mixed gas.
[0029] Composition and calorific value of blast furnace gas Ingredients <![CDATA[CO2]]> <![CDATA[O2]]> CO <![CDATA[H2]]> <![CDATA[CH4]]> <![CDATA[N2]]> <![CDATA[Calorific value KJ / m 3 > content% 18.69 0.57 23.65 1.39 0.98 54.73 3484.98 Composition and calorific value of coke oven gas Ingredients <![CDATA[CO2]]> CnHm <![CDATA[O2]]> CO <![CDATA[H2]]> <![CDATA[CH4]]> <![CDATA[N2]]> <![CDATA[Calorific value KJ / m 3 > content% 2.40 1.99 0.55 7.83 64.89 18.15 4.19 15660.15 The blast furnace gas to coke oven gas ratio is 1:0.081, and the calorific value of the mixed gas is 4400 KJ / m³. 3 .
[0030] 2. Preheating of iron ore Iron ore with a particle size of 15–50 mm is added from the top of the shaft furnace. As the iron ore flows downwards under its own weight, it exchanges heat with the high-temperature flue gas flowing upwards from the heating zone in the preheating zone. After 2–3 hours of preheating, the iron ore reaches a temperature of 500–600°C when it exits the preheating zone. Simultaneously, the limonite in the specular hematite undergoes dehydration. After heat exchange in the preheating zone, the high-temperature flue gas, containing dust and at a temperature of 80–120°C, is discharged from the top of the shaft furnace. The flue gas undergoes wet dust removal and is then discharged into the atmosphere via an exhaust fan.
[0031] 3. Heating of iron ore Two combustion chambers are arranged along the height of the heating zone on both sides of the vertical furnace. The temperature of the upper combustion chamber is controlled at 700-800℃, and the temperature of the lower combustion chamber is controlled at 950-1050℃. In the combustion chamber, the gas and combustion air are mixed and burned. The high-temperature flue gas produced by combustion enters the feed zone from both sides of the furnace and exchanges heat with the iron ore flowing down from the preheating zone in the heating zone. After 2-3 hours of heating, the iron ore flows out of the heating zone at a temperature of 900-950℃, while the siderite in the specular hematite is fully decomposed.
[0032] 4. Reduction of iron ore In the reduction zone of the vertical shaft furnace, after the reducing gas is introduced from the bottom, the H2 and CO in the gas participate in the reduction of iron ore to generate water vapor and CO2. After the iron ore is reduced in the reduction zone of the vertical shaft furnace for 4 to 5 hours, the iron ore can be fully magnetized.
[0033] 5. Cooling, grinding and magnetic separation of roasted ore After the iron ore is roasted in the reduction zone of the vertical shaft furnace, the high-temperature roasted ore is discharged from the bottom of the vertical shaft furnace through the discharge roller. It is first cooled to 60-80°C by water. Then, the roasted ore is ground in a ball mill to a density of over 80% -200 mesh and subjected to a magnetic separation process with a magnetic field strength of 1250 Oe to obtain iron concentrate with an iron grade of 57% and a metal recovery rate of 83%.
[0034] Embodiments of the present invention: This implementation method is based on 100m 3 The small vertical shaft furnace is used to illustrate the process of reducing iron ore with coal.
[0035] 1. Material selection Difficult-to-process low-grade iron ore: The ore type is specular hematite (composed of hematite, limonite and siderite), with a particle size of 15-50mm and an iron grade of 33%; Pulverized coal injection: The pulverized coal selected is high volatile coal with a particle size of less than 1mm. The volatile matter content in the pulverized coal is 44%, the fixed carbon content is 45%, the ash content is 9%, and the softening temperature of the coal ash is 1180℃.
[0036] Gas for heating and reduction: high-coke mixed gas.
[0037] 2. Preheating of iron ore Iron ore with a particle size of 15–50 mm is added from the top of the shaft furnace. As the iron ore flows downwards under its own weight, it exchanges heat with the high-temperature flue gas flowing upwards from the heating zone in the preheating zone. After 2–3 hours of preheating, the iron ore reaches a temperature of 500–600°C when it exits the preheating zone. Simultaneously, the limonite in the specular hematite undergoes dehydration. After heat exchange in the preheating zone, the high-temperature flue gas, containing dust and at a temperature of 80–120°C, is discharged from the top of the shaft furnace. The flue gas undergoes wet dust removal and is then discharged into the atmosphere via an exhaust fan.
[0038] 3. Heating of iron ore Two combustion chambers are arranged along the height of the heating zone on both sides of the vertical furnace. The temperature of the upper combustion chamber is controlled at 700-800℃, and the temperature of the lower combustion chamber is controlled at 950-1050℃. In the combustion chamber, the gas and combustion air are mixed and burned. The high-temperature flue gas produced by combustion enters the feed zone from both sides of the furnace and exchanges heat with the iron ore flowing down from the preheating zone in the heating zone. After 2-3 hours of heating, the iron ore flows out of the heating zone at a temperature of 900-950℃, while the siderite in the specular hematite is fully decomposed.
[0039] 4. Reduction of iron ore A pulverized coal injection device is added outside the existing vertical shaft furnace reduction zone. Part of the flue gas discharged from the vertical shaft furnace is used as the injection gas. The pulverized coal injection device injects high volatile pulverized coal into the reduction zone of the vertical shaft furnace. After the pulverized coal is heated in the furnace, it undergoes high-temperature pyrolysis. At the same time, the residual carbon produced after the pyrolysis of the pulverized coal reacts with CO2 in the flue gas to generate reducing gas containing H2 and CO. After the iron ore is added from the top of the vertical shaft furnace, it passes through the drying preheating zone and the heating zone in sequence, which can raise the temperature to over 500℃. After the hematite and limonite contained in the iron ore come into contact with the reducing gas, the vertical shaft furnace can achieve magnetized roasting of iron ore without the use of reducing gas.
[0040] 5. Cooling, grinding and magnetic separation of roasted ore After the iron ore is roasted in the reduction zone of the vertical shaft furnace, the high-temperature roasted ore is discharged from the bottom of the vertical shaft furnace through the discharge roller. It is first cooled to 60-80°C by water. Then, the roasted ore is ground in a ball mill to a density of over 80% -200 mesh and subjected to a magnetic separation process with a magnetic field strength of 1250 Oe to obtain iron concentrate with an iron grade of 59% and a metal recovery rate of 85%.
[0041] Summarize: When conventional gas-based reducing agents are used as the reducing agent in iron ore magnetization roasting, blast furnace gas is typically used. Blast furnace gas has a low hydrogen content, and the roasted ore produced in the vertical shaft furnace, after grinding and magnetic separation, yields an iron concentrate with a grade of 56-58% and a metal recovery rate of 83-85%. However, when bituminous coal is used as the reducing agent in iron ore magnetization roasting, the large amount of hydrogen produced during pyrolysis can serve as a highly efficient reducing agent for iron ore magnetization roasting, improving the quality of the roasted ore. The roasted ore produced in the vertical shaft furnace, after grinding and magnetic separation, yields an iron concentrate with a grade of 58-59% and a metal recovery rate of 84-85%. This demonstrates that using bituminous coal as the reducing agent in the iron ore magnetization roasting of this invention can improve the quality of iron ore magnetization roasting. Furthermore, the production cost of using a gas-based reducing agent in iron ore magnetization roasting is higher than that of using bituminous coal as the reducing agent.
Claims
1. A method for reducing iron ore using a coal-based method in a vertical shaft furnace with magnetized roasting, characterized in that, A pulverized coal injection device is added outside the existing vertical furnace reduction zone. Part of the flue gas discharged from the vertical furnace is used as the injection gas. The pulverized coal injection device is used to inject high volatile pulverized coal into the vertical furnace reduction zone. After being heated in the furnace, pulverized coal undergoes high-temperature pyrolysis. Simultaneously, the residual char produced after pulverized coal pyrolysis reacts with CO2 in the flue gas to generate reducing gas containing H2 and CO. After iron ore is added from the top of the vertical shaft furnace, it passes through the drying preheating zone and the heating zone in sequence, raising the temperature to over 500℃. The hematite and limonite contained in the iron ore come into contact with the reducing gas, and the iron ore is then magnetized and roasted.
2. The method for reducing iron ore using a coal-based magnetized roasting shaft furnace according to claim 1, characterized in that, The reduction zone of the vertical furnace is divided into 3-6 non-interconnected injection zones by vertical partition plates. Each injection zone is equipped with a pipe, through which pulverized coal is injected separately into the corresponding injection zone.
3. The method for reducing coal-based iron ore in a vertical shaft furnace by magnetization roasting according to claim 2, characterized in that, The pulverized coal injection device includes a vertical shaft furnace flue gas return pipe, a Roots blower, a pulverized coal feed port, a feed pipe, a main injection pipe, a branch pipe, an injection branch pipe, a partition plate, and a reducing coal injection tower; The flue gas return pipe of the vertical furnace is connected to the inlet of the Roots blower, the bottom of the pulverized coal feed port is connected to the inlet of the feed pipe, the outlet of the Roots blower and the outlet of the feed pipe are respectively connected to the inlet of the main spray pipe, the main spray pipe is connected to the branch pipe, the branch pipe is connected to each spray branch pipe, and the partition plate is set in the reducing coal spray tower to divide the reducing coal spray tower into multiple spray zones along the length direction.
4. The method for reducing coal-based iron ore in a vertical shaft furnace by magnetization roasting according to claim 3, characterized in that, 10-15% of the flue gas is extracted from the main flue gas outlet of the vertical shaft furnace and returned to the reduction system as injection gas through the flue gas return pipe of the vertical shaft furnace. The injection gas is pressurized to 20-30 kPa by the Roots blower and then comes into contact with the pulverized coal added from the pulverized coal feed port. The injection gas fluidizes the pulverized coal and turns it into a gas-solid two-phase flow. The gas-solid two-phase flow flows into multiple injection branch pipes after passing through the main injection pipe and the branch pipe. Each injection branch pipe then transports the gas-solid two-phase flow to the corresponding injection zone and injects it into the reduction zone of the vertical shaft furnace from the gas-solid two-phase flow injection outlet.
5. The method for reducing coal-based iron ore in a vertical shaft furnace by magnetization roasting according to claim 1, characterized in that, The pulverized coal injection rate in the pulverized coal injection system is 2-5% of the iron ore weight, and the solid-to-gas ratio used for injecting pulverized coal into the flue gas return from the vertical shaft furnace is 3-8 kg / Nm³. 3 .
6. The method for reducing iron ore using a coal-based magnetized roasting shaft furnace according to claim 1, characterized in that, Pulverized coal injection uses high volatile matter with a particle size of less than 1 mm. The volatile matter content in the pulverized coal is 25-45%, the fixed carbon content is 41-65%, the ash content is 8-15%, and the softening temperature of the coal ash is greater than 1150℃.