Method for preparing industrial pure iron through green low-carbon smelting reduction

Abstract

The invention discloses a method for preparing industrial pure iron through green low-carbon smelting reduction. The method comprises the steps of raw material preparation, heating and temperature rise, reduction dripping, inert gas cooling, tail gas recycling and waste heat utilization and pure iron preparation. The method comprises the specific steps that coke and iron ore are placed in a high-temperature-resistant reactor in a layered mode, the iron ore is placed on the upper layer of a coke stock column, coke is laid on the upper layer of the iron ore, the coke and the iron ore are preheated, then the high-temperature-resistant reactor is placed in a high-temperature reaction furnace, the high-temperature-resistant reactor is heated to a certain temperature and then kept at the constant temperature for a period of time, and reduced metal iron penetrates through a coke layer to drip; when the CO concentration in the tail gas of the reactor reaches a peak value, inert gas is rapidly introduced to cool liquid-phase slag adhered to a coke layer, the liquid-phase slag is quenched and converted into powder, H2, CO and CH4 in the tail gas can be recycled, tail gas waste heat can be used for preheating raw materials next time, dripped molten metal iron enters a vacuum induction furnace, O2 is introduced to prepare industrial pure iron, and the tail gas enters the vacuum induction furnace; and efficient slag-iron separation and green low-carbon pure iron production are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of smelting reduction, and in particular relates to a method for preparing industrial pure iron through green and low-carbon smelting reduction. Background Art

[0002] The liquid slag iron obtained from blast furnace ironmaking is discharged from the iron outlet. In the process of slag iron flowing along the iron outlet groove, due to the higher density of molten iron than slag liquid, the molten iron is distributed in the lower layer, and the slag iron floats on the upper layer of the molten iron. The slag iron liquid in different layers is separated by a slag skimmer. The high-temperature molten liquid slag after separation is cooled by water pumping, and the heat carried by the molten slag escapes into the atmosphere with water vapor, and a large amount of slag quenching wastewater is generated at the same time. Patent 202010472478X introduces a device and method for simulating the coke reaction in the high-temperature section of a blast furnace, which mainly simulates the reaction process of different stages of high temperature in a blast furnace, and then obtains the quality change of coke under different conditions, and does not involve molten reduction reaction. Patent 202210328783.0X introduces a device and method for simulating the permeability of a blast furnace column, which mainly involves the high-temperature reaction of iron-containing minerals and coke, the molten flow of iron-containing minerals through the coke layer and dripping, and then evaluates the influence of the coke column on the permeability of the iron-containing mineral. Patent 202310914778.2 introduces a method for treating coking wastewater sludge. By pressing the sludge into balls, reducing and roasting, and recovering metallic iron, the above technology does not involve the judgment process of the layered distribution of coke, the adhesion of slag, and the introduction of inert gas when the CO concentration of the tail gas reaches the peak. In addition, the requirements for iron ore raw materials suitable for blast furnaces are relatively high. Most of the iron ore raw materials in my country are of low grade and small particle size, and the iron ore needs to be sintered or pelletized, which greatly increases the cost of ironmaking production. To this end, if iron-containing lump ore or refractory iron ore can be directly used to manufacture pure iron, and the heat of liquid slag can be effectively recovered at the same time, the cost of ironmaking can be significantly reduced, the recycling of tail gas can be realized, and efficient slag-iron separation and green and low-carbon ironmaking production can be achieved. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing industrial pure iron by green and low-carbon smelting reduction, wherein the reduction of metallic iron in iron ore is achieved through high-temperature smelting reaction, the efficient separation of slag and iron is achieved through inert gas cooling, and the heat of high-temperature molten slag and iron is recovered and reused after gas heat exchange.

[0004] To achieve the above object, the technical solution of the present invention is characterized by:

[0005] Step (1) raw material preparation. Coke and iron ore are placed in a high temperature resistant reactor in layers, the iron ore is placed on the upper layer of the coke column, and the upper layer of the iron ore is covered with coke. The coke and iron ore are preheated to 100°C or above, and then the high temperature resistant reactor is placed in a high temperature reactor. The mass ratio of iron ore to coke is controlled at (10-40): (100-200), the coke particle size is ≥10mm, the coke layer is divided into two layers, the coke particle size of the upper layer is larger than the coke particle size of the lower layer, the reactivity of the upper layer coke is greater than the reactivity of the lower layer coke, the upper layer coke and iron ore are mixed and loaded layer by layer or the iron ore is arranged on the upper surface of the coke layer, the upper layer coke mainly undergoes a molten reduction reaction with the iron ore, and the lower layer coke is a molten slag iron filter layer for inhibiting and adhering to the liquid slag. Coke and iron ore form a material column of a certain thickness, and the fluctuation range of each layer of coke particle size does not exceed 3mm. The thickness of the coke and iron ore charge is 2 times or more of the thickness of the iron ore charge, ensuring that the slag phase minerals are bonded to the coke in the material column, and at the same time, the metallic iron drips along the pores of the material column. The strength of the upper coke after reaction CSR ≥ 63%, the reactivity CRI > 24%, and the strength of the lower coke after reaction CSR ≥ 63%, the reactivity CRI ≤ 24%.

[0006] Step (2) heating, temperature raising, reduction and dripping. After heating to a certain temperature, the temperature is maintained for a period of time. The constant temperature time is not less than the time required for the liquid metal iron to drip completely, that is, not less than the time required for the tail gas CO to reach a peak value. The time required for the tail gas CO to reach a peak value refers to the time corresponding to the maximum value reached by the CO concentration in the tail gas during the high-temperature reaction. The iron ore melts at high temperature and undergoes a reduction reaction with the coke. The reduced metal iron flows along the gap between the material columns and finally passes through the material column layer and drips from the bottom of the reactor.

[0007] Step (3) observe the CO concentration of the tail gas and the inert gas cooling. The reduced metallic iron drips through the coke layer. When the CO concentration in the reactor tail gas reaches a peak, the inert gas is quickly introduced to cool the liquid slag adhering to the coke layer. The liquid slag is rapidly cooled and converted into powder, achieving efficient separation of slag (solid) and iron (liquid). The metallization rate of the reduced iron is not less than 90%.

[0008] Step (4) tail gas recovery and waste heat utilization. The reactor tail gas contains H2, CO, and CH4, which are recycled. In particular, the H2, CO, and CH4 in the tail gas can also be used in step (2) to accelerate the smelting reduction of iron ore. The waste heat of the tail gas can be used to preheat the next raw material.

[0009] Step (5) Preparation of industrial pure iron: The dripping molten metal iron enters a vacuum induction furnace and is introduced with O2 to prepare industrial pure iron.

[0010] Furthermore, the bottom of the high temperature resistant reactor described in step (1) is a porous cone or arc-shaped concave shape, which is convenient for the liquid metal iron produced after molten reduction to flow and drip under the action of gravity, and then separate from the material column. The maximum heating temperature of the high temperature reactor is 1350-2000°C. The iron ore is one or more of sintered ore, pelletized ore, and lump ore. The iron ore particle size should not be less than 5mm, and the lump ore can also be a difficult-to-select iron ore. The coke layer can be reused. When the metallization rate of the dripping reduced iron is lower than 90%, it is necessary to reload and replace the new coke layer.

[0011] Furthermore, the heating to a certain temperature in step (2) refers to heating the sintered ore to 1450°C or above, heating the pelletized ore to 1300°C or above, and heating the lump ore to 1400°C or above. During the constant temperature process, the reducing gas may not be introduced, or one or more of the reducing gases H2, CO, and CH4 may be introduced. The concentration and flow rate of the introduced reducing gas are kept stable so as to confirm the concentration peak of the tail gas CO.

[0012] Furthermore, the inert gas described in step (3) is nitrogen, argon or helium, and the purity of the inert gas is not less than 99%.

[0013] Furthermore, the tail gas described in step (4) is recycled after dust removal, heat exchange, purification, separation and purification, and the temperature of the recycled tail gas after heat exchange does not exceed 50°C.

[0014] Furthermore, the iron content of the industrial pure iron prepared in step (5) can reach 99.9% or above.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] Taking full advantage of the fact that the viscosity of molten slag is higher than that of molten metal iron, the slag is more likely to adhere to coke under the action of viscous tension, thereby promoting the separation of liquid metal iron from solid powder slag. To this end, the present invention designs two layers of coke charging, especially the particle size of the upper coke layer is larger than the particle size of the lower coke layer, and the reactivity of the upper coke layer is greater than the reactivity of the lower coke layer, wherein the upper layer of high-reactivity coke and large-particle coke undergo sufficient molten reduction with the iron ore, while the lower layer of small-particle, low-reactivity coke has an inhibitory and adhesive effect on the reduced liquid slag, thereby achieving efficient separation of the reduced metal iron in the iron ore from the slag. In order to accurately measure the molten reduction process of iron ore and coke, the CO concentration change in the tail gas is used to judge the intensity of the reaction. When CO reaches a peak value, it means that the reduction reaction between coke and iron ore is the most intense. Because the reduced metallic iron melts and drips, the CO concentration decreases, and it is judged that the molten reduction is over. Inert gas is quickly introduced for cooling, so that the molten slag mainly adhering to the lower layer of coke is instantly converted into amorphous powder, and the solid-liquid separation of slag-iron is realized. Different temperature control ranges are given for different types of iron-containing minerals to accurately judge the dripping time of molten iron, so that the metallization rate of reduced iron is not less than 90%, and iron ore and gangue are efficiently separated, laying the preliminary foundation for the preparation of industrial pure iron; the heat of slag iron is recovered through tail gas heat exchange, which is used for raw material preheating and re-reduction, reducing CO2 emissions. Compared with the water cooling of blast furnace ironmaking slag, the heat of tail gas is recovered through heat exchange between reducing gas and slag, and the reducing gas and inert gas in the tail gas are recycled, realizing the green low-carbon slag iron smelting separation. DETAILED DESCRIPTION

[0017] Figure 1 A high temperature resistant reactor with a porous conical bottom.

[0018] Figure 2 The invention discloses a high temperature resistant reactor with a porous concave arc-shaped bottom.

[0019] Figure 3 Schematic diagram of the iron ore and coke charging structure.

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of the exemplary embodiments is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The present invention is described in more detail below through examples.

[0022] (1) Raw material preparation. Coke and iron ore are placed in layers in a high temperature reactor. The iron ore is placed on the upper layer of the coke column. The upper layer of the iron ore is covered with coke. The coke and iron ore are mixed and placed in a high temperature reactor. The coke and iron ore are preheated to 100°C before heating and reduction. The high temperature reactor is then placed in a high temperature reactor. The bottom of the high temperature reactor is a porous cone ( Figure 1 ) or notched arc ( Figure 2 ), so that the liquid metal iron produced after smelting reduction can flow and drip under the action of gravity, and then separate from the material column. Coke and iron ore are laid layer by layer and mixed, and coke is laid on the top of the material column, such as Figure 3 As shown, iron ore and coke can also be mixed and distributed in layers. The mass ratio of iron ore to coke is (10-40): (100-200), and the particle size of the upper coke layer is larger than that of the lower coke layer for loading. The coke and iron ore form a material column of a certain thickness to ensure that the slag phase minerals are bonded to the coke in the material column, and the metallic iron drips along the pores of the material column.

[0023] (2) Heating and reducing and dripping. After heating to a certain temperature, keep the temperature constant for a period of time. The CO concentration in the tail gas reaches a peak after a period of reaction. The iron ore melts at high temperature and reacts with the coke to reduce it. The reduced metallic iron flows along the gaps in the material column and eventually passes through the material column layer and drips from the bottom of the reactor.

[0024] (3) Observe the CO concentration in the tail gas and the inert gas cooling. When the CO concentration in the reactor tail gas reaches the peak, argon gas is quickly introduced to cool the liquid slag adhering to the coke layer after the metallic iron drips. The adhering liquid slag is instantly cooled and turned into amorphous powder under the action of argon gas, realizing efficient separation of slag (solid) and iron (liquid). After the metallic iron melts and drips, the slag and iron are efficiently separated.

[0025] (4) Tail gas recovery and recycling and waste heat utilization. The tail gas is recycled after dust removal, heat exchange, purification, separation and purification. The temperature of the tail gas recycled after heat exchange shall not exceed 50°C.

[0026] (5) Preparation of industrial pure iron. The dripping molten metal iron enters the vacuum induction furnace and is fed with O2 to prepare industrial pure iron. The coke layer can be reused. When the metallization rate of the dripping reduced iron is lower than 90%, it needs to be reloaded and replaced with a new coke layer.

[0027] The specific raw material preparation process parameters, heating reduction-cooling-exhaust waste heat utilization-pure iron preparation process parameters are shown in Tables 1 and 2.

[0028] Table 1 Process parameters for raw material preparation

[0029]

[0030]

[0031] Table 2 Heating reduction-cooling-exhaust waste heat utilization-pure iron preparation process parameters

[0032]

Claims

1. A method for preparing industrial pure iron by green low-carbon smelting reduction, comprising the steps of raw material preparation, heating and temperature raising, reduction dripping, inert gas cooling, tail gas recovery and recycling and waste heat utilization, and industrial pure iron preparation, characterized in that: Coke and iron ore are placed in layers in a high-temperature reactor, iron ore is placed on the upper layer of the coke column, and coke is placed on the upper layer of the iron ore. The coke and iron ore are preheated to 100°C or above, and then the high-temperature reactor is placed in a high-temperature reactor. After heating to a certain temperature, the temperature is kept constant for a period of time, and the reduced metallic iron drips through the coke layer. When the CO concentration in the reactor tail gas reaches a peak, inert gas is quickly introduced to cool the liquid slag adhered to the coke layer. The liquid slag is rapidly cooled and converted into powder, and the H2 and CO in the tail gas are and CH4 can be recycled, and the waste heat of the tail gas can be used for preheating the next raw material. The dripping molten metal iron enters the vacuum induction furnace, and O2 is introduced to prepare industrial pure iron. The coke is divided into two layers, the particle size of the upper coke is larger than that of the lower coke, and the reactivity of the upper coke is greater than that of the lower coke. The upper coke is mixed with the iron ore and loaded layer by layer, or the iron ore is arranged on the upper surface of the coke layer. The upper coke mainly undergoes a molten reduction reaction with the iron ore, and the lower coke is a molten slag iron filter layer for inhibiting and adhering to the liquid slag.

2. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: The lower bottom of the high temperature resistant reactor is in a porous cone shape or a notched arc shape.

3. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: The high temperature reaction furnace has a heating temperature of 1350-2000°C.

4. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: The iron ore particle size is ≥5mm, the iron ore is one or more of sintered ore, pelletized ore, and lump ore, the mass ratio of iron ore to coke is controlled at (10-40): (100-200), the coke particle size is ≥10mm, the fluctuation range of the particle size of each layer of coke does not exceed 3mm, and the thickness of the charge composed of coke and iron ore is 2 times or more of the thickness of the iron ore charge.

5. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: The upper coke layer has a strength CSR of ≥63% and a reactivity CRI of >24% after reaction, and the lower coke layer has a strength CSR of ≥63% and a reactivity CRI of ≤24% after reaction.

6. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: The heating to a certain temperature refers to heating the sintered ore to 1450°C or above, heating the pelletized ore to 1300°C or above, and heating the lump ore to 1400°C or above.

7. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: During the constant temperature process, one or more reducing gases selected from the group consisting of H2, CO and CH4 are introduced.

8. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: The inert gas is nitrogen, argon or helium, and the purity of the inert gas is not less than 99%.

9. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: The coke layer can be reused. When the metallization rate of the dripping reduced iron is lower than 90%, it is necessary to reload and replace a new coke layer.

10. The method for preparing industrial pure iron by green and low-carbon smelting reduction according to claim 1, characterized in that: The tail gas is recycled after dust removal, heat exchange, purification, separation and purification, and the temperature of the recycled tail gas after heat exchange does not exceed 50°C.

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