阅读说明：本技术 一种含铁赤泥煤基直接还原工艺及系统 (Iron-containing red mud coal-based direct reduction process and system ) 是由 权芳民 何成善 丁凯 张丽宙 于 2020-07-07 设计创作，主要内容包括：本发明公开了一种含铁赤泥煤基直接还原工艺及系统,将赤泥、高挥发分煤进行干燥磨细,赤泥、高挥发分煤、粘结剂、金属聚集剂按质量比为1：0.25~0.35：0.01~0.03：0.01~0.03进行配料、混匀后,加水造球,得到粒径20~25mm的含碳球团；含碳球团干燥后输送至转底炉直接还原焙烧,通过高挥发分煤充分热解产生的H<Sub>2</Sub>和以H<Sub>2</Sub>O做气化剂的碳气化反应产生H<Sub>2</Sub>对赤泥进行还原,控制炉膛温度为1250~1280℃、焙烧时间为30~35min,可使赤泥得到充分还原。本发明采用氢冶金工艺对赤泥实现高效还原,具有炉膛传热效率高、铁氧化物还原速度快、单炉产能高、产品质量高、本质减排的优点。(The invention discloses a coal-based direct reduction process and a system for iron-containing red mud, which are characterized in that red mud and high-volatile coal are dried and ground, and the red mud, the high-volatile coal, a binder and a metal aggregating agent are mixed according to the mass ratio of 1: 0.25-0.35: 0.01-0.03: 0.01-0.03, mixing, adding water, and pelletizing to obtain carbon-containing pellets with the particle size of 20-25 mm; conveying the carbon-containing pellets after drying to a rotary hearth furnace for direct reduction roasting, and fully pyrolyzing the high-volatile coal to generate H 2 And with H 2 H is generated by carbon gasification reaction with O as gasification agent 2 Reducing the red mud, controlling the temperature of a hearth to be 1250-1280℃,The roasting time is 30-35 min, so that the red mud can be fully reduced. The invention adopts the hydrogen metallurgy process to realize the efficient reduction of the red mud, and has the advantages of high hearth heat transfer efficiency, high iron oxide reduction speed, high single-furnace productivity, high product quality and essential emission reduction.)

1. The iron-containing red mud coal-based direct reduction process is characterized by comprising the following steps of:

(1) drying raw materials: drying and dehydrating the red mud and the high-volatile coal after natural drying in the air, and controlling the external moisture content of the red mud and the high-volatile coal to be lower than 3 percent;

(2) dry milling to prepare powder: grinding the high-volatile coal to-200 meshes accounting for more than 80%, and grinding the red mud to-200 meshes accounting for more than 90%;

(3) preparing carbon-containing pellets: mixing red mud, high volatile coal, a binder and a metal aggregating agent in a mass ratio of 1: 0.25-0.35: 0.01-0.03: 0.01-0.03, mixing, adding water, and pelletizing to obtain carbon-containing pellets with the particle size of 20-25 mm;

(4) and (3) roasting in hydrogen metallurgy: conveying the carbon-containing pellets after drying to a rotary hearth furnace for direct reduction roasting, and fully pyrolyzing the high-volatile coal to generate H₂And with H₂H generated by carbon gasification reaction with O as gasification agent₂Reducing the red mud, controlling the temperature of a hearth to 1250-1280 ℃, and roasting for 30-35 min;

(5) and (3) cooling: cooling the high-temperature metallized pellet at 900-1000 ℃ obtained in the step (4) by an oxygen-free cooling device to obtain a normal-temperature metallized pellet;

(6) dry grinding and dry separation: and carrying out dry grinding and dry separation on the normal-temperature metallized pellets to obtain iron powder and high-aluminum tailings.

2. The ferrous red mud coal-based direct reduction process of claim 1, which is characterized by comprising the following steps: in the step (1), the high-volatile coal is lignite or peat.

3. The ferrous red mud coal-based direct reduction process of claim 1, which is characterized by comprising the following steps: in the step (1), the content of volatile matters in the high-volatile coal is 45-50% (wherein the content of hydrogen is 4-5%), and the content of fixed carbon is 43-48%.

4. The ferrous red mud coal-based direct reduction process of claim 1, which is characterized by comprising the following steps: in the step (1), the red mud and the high volatile coal are dried and dehydrated by a red mud dryer and a coal dryer, heat sources of the red mud dryer and the coal dryer are from flue gas at an outlet of a heat accumulating type heat exchanger, and the flue gas discharged after drying is purified by a dust removal system and then is pressurized and discharged by a smoke extractor.

5. The ferrous red mud coal-based direct reduction process of claim 1, which is characterized by comprising the following steps: in the step (3), the binder is bentonite; the metal aggregating agent is high-grade iron ore concentrate, the iron grade of the high-grade iron ore concentrate is more than 62%, and SiO is₂The content is 6-8%.

6. The ferrous red mud coal-based direct reduction process of claim 1, which is characterized by comprising the following steps: in the step (5), the carbon-containing pellets are dried by a chain grate, specifically, flue gas discharged from a heat accumulating type heat exchanger and having the temperature of 300-400 ℃ is used as a heat source for drying, and the flue gas discharged after the materials are dried and having the temperature of 150-180 ℃ is purified by a dust removal system and then is discharged by a smoke extractor in a pressurized manner.

7. The ferrous red mud coal-based direct reduction process of claim 1, which is characterized by comprising the following steps: in the step (5), the carbon-containing pellets are dried by a chain grate and then conveyed to a rotary hearth furnace, and are uniformly laid on the bottom of the rotary hearth furnace by a material distributor, wherein the laying thickness is controlled to be 60-70 mm.

8. The ferrous red mud coal-based direct reduction process of claim 1, which is characterized by comprising the following steps: in the step (5), the flue gas at 900-1000 ℃ discharged by the rotary hearth furnace enters a heat accumulating type heat exchanger, high-temperature hot air at 850-900 ℃ is replaced, high-temperature combustible gas generated in the reduction process of the carbon-containing pellets is mixed with the high-temperature hot air generated from the heat accumulating type heat exchanger and then is combusted, and the generated heat can be used for the heat requirement of the rotary hearth furnace.

9. The ferrous red mud coal-based direct reduction process of claim 1, which is characterized by comprising the following steps: in the step (6), the iron powder is subjected to iron powder cold press to produce an iron powder product; the high-aluminum tailings are leached by strong alkali to produce an aluminum oxide product, and the tailings are removed at the same time.

10. A direct reduction system of iron-containing red mud coal base comprises a mixer, a pelletizer, a chain grate, a hydrogen metallurgy rotary hearth furnace, an oxygen-free cooling device, a dry grinding machine and a dry magnetic separator which are connected in sequence; the mixer is also connected with a dry-type ore mill and a dry-type coal mill, and the dry-type ore mill and the dry-type coal mill are respectively connected with a red mud dryer and a coal dryer; the hydrogen metallurgy rotary hearth furnace is also connected with a heat accumulating type heat exchanger for providing high-temperature hot air for the hydrogen metallurgy rotary hearth furnace, the heat accumulating type heat exchanger is connected with a blower, and the heat accumulating type heat exchanger is connected with a chain grate machine, a red mud dryer and a coal dryer; the chain grate machine, the red mud dryer and the coal dryer are connected with a dust removal system, and the dust removal system is connected with a smoke extractor; the dry magnetic separator is connected with an iron powder cold pressing device and a strong alkali leaching device.

Technical Field

The invention belongs to the technical field of metallurgy and mineral engineering, and relates to a direct reduction process and a direct reduction system for iron-containing red mud coal base.

Background

The red mud is strong alkaline solid waste generated after alumina or aluminum hydroxide is prepared by taking bauxite as a raw material. The utilization rate of the Chinese red mud is only 4%, most of the Chinese red mud is stored in a yard stacking or damming wet stacking mode, not only a large amount of land is occupied, and serious environmental pollution is caused, but also a large amount of valuable elements contained in the red mud are not recycled. The red mud is reasonably treated and efficiently utilized, not only meets the requirement of environmental protection, but also is beneficial to the sustainable development of human society.

The red mud is rich in iron, aluminum, titanium and other valuable metals, and the iron is Fe₂O₃The form is fine, and the water content is high. According to the measurement and calculation, 1-2 t of red mud can be additionally produced when 1t of alumina is produced in the industry. Taking bayer process red mud as an example, the chemical composition of the red mud produced is TFe: 25 to 35% of Fe₂O₃：40～50%、SiO₂：15～20%、Al₂O₃：21～25%、CaO：2～10%、TiO₂: 2-5%. Therefore, the red mud has great economic utilization value.

In order to realize the efficient utilization of the red mud and the extraction of valuable elements, a great deal of research work is carried out at home and abroad, and at present, the main methods for extracting valuable metals from the red mud comprise: (1) valuable elements such as aluminum, iron, rare earth, scandium and the like are extracted from the red mud by a wet process. Mixing red mud with appropriate amount of concentrated sulfuric acid, aging, rapidly reducing and roasting with a reducing agent at a certain temperature to obtain SO-containing product₂The flue gas realizes the regeneration and cyclic utilization of sulfuric acid through an acid making process; the roasted reduction calcine is subjected to metallurgical enrichment, separation and purification by adopting a water leaching method to obtain a scandium oxide product and a rare earth enrichment material; and carrying out magnetic separation on the water leaching slag to obtain iron ore concentrate and magnetic separation tailings, and then carrying out alkaline leaching on the magnetic separation tailings to prepare the aluminum oxide. (2) Iron is selected from the red mud by a pyrogenic process. Uniformly mixing red mud, a reducing agent and an additive to prepare a 10-30mm red mud briquette, wherein the mass percentage of the additive in the ingredients is 3-10%, and the molar ratio of carbon to iron oxide in the red mud briquette is C/O =1.2-1.5 by reasonably adding the red mud and the reducing agent; the reducing agent is pulverized coal, coke powder and cokingOne kind of fly ash; the additive is calcium ferrite powder; the process comprises the following steps: the red mud block mass is added into an empty tank of a slag tank in advance, then high-temperature slag is injected during slag discharging, after reaction for 10-30min, the slag treatment process is adopted for post-treatment, and finally, magnetic separation is carried out on cooling slag to realize slag-iron separation, so that iron powder with high grade can be obtained. (3) A method for comprehensively recovering useful metals from red mud. The method comprises the steps of proportioning red mud, an alkali-increasing agent and a reducing agent, reducing and roasting, leaching aluminum, carrying out magnetic separation on a slag phase, recovering iron, leaching scandium by adopting an acid solution, and precipitating scandium in a scandium leaching solution by using a composite scandium precipitation agent consisting of mandelic acid and boric acid to obtain a scandium-containing product. (4) The red mud is utilized by adopting magnetic roasting-magnetic separation. Drying, crushing and grinding the red mud to the granularity of less than 0.25mm, uniformly mixing the red mud with a certain amount of alkali lignin reducing agent, adding the mixed material of the red mud and the alkali lignin reducing agent into a microwave reaction device, and carrying out microwave magnetizing roasting to obtain the roasted product. And naturally cooling the obtained calcine, then grinding the calcine to obtain ground ore slurry, and adding the ground ore slurry into a magnetic separator for magnetic separation to obtain iron ore concentrate.

As can be seen from the utilization method of the red mud, the existing red mud treatment process mainly focuses on two methods of roasting and wet leaching. The wet leaching process has the problems of small treatment capacity, low iron grade of the obtained iron ore concentrate, low product quality and high production cost; in the roasting process, because the iron grade of the red mud is low, a large amount of gangue particles are mixed between the fine iron oxide particles, so that the reduced fine metal particles are difficult to crystallize and link. When the reduced materials are subjected to iron extraction by a grinding and selecting process, the materials are ground to a small particle size to realize the separation of iron and gangue minerals, and the fine grinding particle size brings great difficulty to the magnetic separation process. In addition, in the coal-based direct reduction of the red mud, when carbon is used as a reducing agent to reduce the red mud, the carbon gasification temperature in the coal is above 850 ℃, so that the reduction temperature of the red mud is higher, the softening temperature of fayalite is reached, the red mud is easy to generate a liquid phase on the surface in the reduction process, the reduction reaction of iron oxide in the red mud is difficult to continue, the metallization rate of the reduced material is lower, the iron grade of the ground product is low, and the metal recovery rate is low.

Carbon metallurgy is a typical process of traditional development in the steel industry, the reducing agent being carbon and the end product being carbon dioxide. The hydrometallurgical reducing agent is hydrogen, the final product is water, and zero emission of carbon dioxide is realized. The traditional direct reduction process mainly uses CO as a reducing agent to remove oxygen in iron ore. CO has large molecules and is difficult to permeate into iron ore. H₂Has the smallest molecular weight and the smallest molecular diameter, can easily permeate into the iron ore, and H in the iron ore₂Has a permeation rate 5 times that of CO, H₂Has a reduction potential 11 times that of CO and a reduction potential 11 times that of carbon monoxide. Thus, the reduction efficiency of hydrometallurgy is multiplied compared to the reduction potential of CO compared to carbon metallurgy.

The so-called hydrogen metallurgy is mainly used for H in the iron ore smelting process₂As a reducing agent. H₂Is the most active reducing agent, and uses H in the gas-solid reduction reaction process of iron oxide₂When used as a reducing agent, the main products are metallic iron and water vapor, and the reduced tail gas has no influence on the environment. Therefore, the hydrogen metallurgy is vigorously developed, the reduction efficiency of the iron ore can be greatly improved, and the consumption of the carbon reducing agent in the smelting process is reduced.

Can economically supply H in scale₂Is the premise and the basis of the development of the hydrogen metallurgy process. At present, there are 4 methods for large-scale hydrogen production: coal gasification hydrogen production, natural gas cracking hydrogen production, petroleum gasification and cracking hydrogen production, and water electrolysis hydrogen production. In addition, the coke oven gas is also the gas of choice for preparing hydrogen in large quantities at low cost. It can be seen that in these iron ore hydrometallurgical techniques, H is produced in advance₂Then adding H₂After being stored and conveyed, the iron ore is introduced into high-temperature iron ore for reduction, and the production cost of the product is higher. Due to the limitation of the production cost of products, the various hydrogen metallurgy processes are only stopped on the basis of laboratory tests and mechanism researches, and no application example in the aspect of industrialization exists.

Disclosure of Invention

In view of the above technical problems, the present invention aims to provide a novel liquid crystal display deviceThe iron-red mud coal-based direct reduction process and system solve the problems of high reduction temperature, long reduction time, low metallization rate of reduced materials, low iron grade of ground products and low metal recovery rate in the direct reduction process of red mud, and safely and economically produce H₂And is combined with H₂Used in the direct reduction of red mud.

The invention fully utilizes H produced in the coal pyrolysis process₂H produced by carbon gasification reaction with water₂The coal pyrolysis process and the iron-containing red mud reduction process are combined, and the high volatile coal with a certain proportion is added into the iron-containing red mud, so that the coal can produce H in the pyrolysis process₂，H₂Production of H upon reduction of iron oxides₂O，H₂The O and the high-temperature carbon are subjected to carbon gasification reaction to generate H₂Forming a coupling reaction to thereby effect H₂The iron-containing red mud is quickly and efficiently reduced.

The production process comprises the following steps:

(1) drying raw materials: drying and dehydrating the red mud and the high-volatile coal after natural drying in the air, and controlling the external moisture content of the red mud and the high-volatile coal to be lower than 3 percent;

(2) dry milling to prepare powder: grinding the high-volatile coal to-200 meshes accounting for more than 80%, and grinding the red mud to-200 meshes accounting for more than 90%;

(3) preparing carbon-containing pellets: mixing red mud, high volatile coal, a binder and a metal aggregating agent in a mass ratio of 1: 0.25-0.35: 0.01-0.03: 0.01-0.03, mixing, adding water, and pelletizing to obtain carbon-containing pellets with the particle size of 20-25 mm;

(4) and (3) roasting in hydrogen metallurgy: conveying the carbon-containing pellets after drying to a rotary hearth furnace for direct reduction roasting, and fully pyrolyzing the high-volatile coal to generate H₂And with H₂H generated by carbon gasification reaction with O as gasification agent₂Reducing the red mud, controlling the temperature of a hearth to 1250-1280 ℃, and roasting for 30-35 min;

(5) and (3) cooling: cooling the high-temperature metallized pellet at 900-1000 ℃ obtained in the step (4) by an oxygen-free cooling device to obtain a normal-temperature metallized pellet; the metallization rate of the high-temperature metallized pellets is 93-96%, the carbon content is 0-1%, and the cold strength is more than 1800N;

(6) dry grinding and dry separation: the normal temperature metallized pellet is dry ground and selected to obtain iron powder and Al with iron grade of more than 88 percent, metallization rate of more than 90 percent and metal recovery rate of more than 92 percent₂O₃High-aluminum tailings with the content of 45-50%. .

In the step (1), the red mud comprises the following components: TFe: 25 to 35% by weight of Fe₂O₃：40~50%，Na₂O：2~5%，Al₂O₃：21~25%，SiO₂：15~20%，CaO：2~10%、H₂O：5~10%。

In the step (1), the high-volatile coal is lignite or peat.

In the step (1), the content of volatile matters in the high-volatile coal is 45-50% (wherein the content of hydrogen is 4-5%), and the content of fixed carbon is 43-48%.

In the step (1), the red mud and the high volatile coal are dried and dehydrated by a red mud dryer and a coal dryer, heat sources of the red mud dryer and the coal dryer are from flue gas at an outlet of a heat accumulating type heat exchanger, and the flue gas discharged after drying is purified by a dust removal system and then is pressurized and discharged by a smoke extractor.

In the step (3), the binder is bentonite; the metal aggregating agent is high-grade iron ore concentrate, the iron grade of the high-grade iron ore concentrate is more than 62%, and SiO is₂The content of the red mud is 6-8%, the grade of the red mud iron is low, the particles are extremely fine, metal particles in the reduced metallized pellets are difficult to grow up, and the metal recovery rate and the iron grade in the grinding and selecting process of the metallized pellets are low; in order to ensure that the metal particles grow up after the carbon-containing pellets are reduced, a metal focusing agent is added into the carbon-containing pellets.

In the step (5), the carbon-containing pellets are dried by a chain grate, specifically, flue gas discharged from a heat accumulating type heat exchanger and having the temperature of 300-400 ℃ is used as a heat source for drying, and the flue gas discharged after the materials are dried and having the temperature of 150-180 ℃ is purified by a dust removal system and then is discharged by a smoke extractor in a pressurized manner.

In the step (5), the carbon-containing pellets are dried by a chain grate and then conveyed to a rotary hearth furnace, and are uniformly laid on the bottom of the rotary hearth furnace by a material distributor, wherein the laying thickness is controlled to be 60-70 mm.

In the step (5), the flue gas at 900-1000 ℃ discharged by the rotary hearth furnace enters a heat accumulating type heat exchanger, high-temperature hot air at 850-900 ℃ is replaced, high-temperature combustible gas generated in the reduction process of the carbon-containing pellets is mixed with the high-temperature hot air generated from the heat accumulating type heat exchanger and then is combusted, and the generated heat can be used for the heat requirement of the rotary hearth furnace.

In the step (6), the iron powder is subjected to iron powder cold press to produce an iron powder product; the high-aluminum tailings are leached by strong alkali to produce an aluminum oxide product, and the tailings are removed at the same time.

A direct reduction system of iron-containing red mud coal base comprises a mixer, a pelletizer, a chain grate, a hydrogen metallurgy rotary hearth furnace, an oxygen-free cooling device, a dry grinding machine and a dry magnetic separator which are connected in sequence; the mixer is also connected with a dry-type ore mill and a dry-type coal mill, and the dry-type ore mill and the dry-type coal mill are respectively connected with a red mud dryer and a coal dryer; the hydrogen metallurgy rotary hearth furnace is also connected with a heat accumulating type heat exchanger for providing high-temperature hot air for the hydrogen metallurgy rotary hearth furnace, the heat accumulating type heat exchanger is connected with a blower, the heat accumulating type heat exchanger is connected with a chain grate machine, a red mud dryer and a coal dryer, the outlet flue gas of the heat accumulating type heat exchanger is used as a heat source to dry materials, the chain grate machine, the red mud dryer and the coal dryer are connected with a dust removal system, the dust removal system is connected with a smoke extractor, and the flue gas discharged after the materials are dried is purified by the dust removal system and then is discharged by the smoke extractor in a pressurizing manner; the dry magnetic separator is connected with an iron powder cold pressing device and a strong base leaching device, iron powder passes through the iron powder cold pressing device to obtain an iron powder product, and high-aluminum tailings pass through the strong base leaching device to obtain an aluminum oxide product.

The reduction principle of the red mud hydrometallurgy process is as follows:

according to the invention, high-volatile coal, a binder and a metal aggregating agent with a high proportion are added into red mud and prepared into carbon-containing pellets with the particle size of 20-25 mm, and H generated by full pyrolysis of coal is used in the heating and temperature rising process of the pellets in a hydrometallurgy rotary hearth furnace₂And with H₂H generated by carbon gasification reaction by taking O as gasification agent₂The red mud is reduced, so that the high integration of the coal full pyrolysis process and the red mud metallurgy reduction process in a thermal state is realized.

In the process of heating and warming carbon-containing pellets in a hydrometallurgy rotary hearth furnace, the surface layer of the carbon-containing pellets is preferentially heated and warmed, and when the temperature of the surface layer of the pellets rises to 350-400 ℃, tar, benzene, naphthalene, alkane, alkene, hydrocarbon and H in the raw coal are reduced on the surface layer₂When the volatile components are separated out, the volatile components directly enter a high-temperature combustion space of a hearth for full pyrolysis and serve as fuel for burning out. When the temperature of the surface layer of the pellet is raised to about 900 ℃, the iron oxide on the surface layer reaches the reduction temperature, the coal in the core part of the pellet gradually starts to be pyrolyzed from the shallow layer to the deep layer, tar, benzene, naphthalene, alkane, alkene, hydrocarbon and the like generated by pyrolysis can be fully pyrolyzed when passing through a high-temperature material layer on the surface layer or the shallow layer of the pellet, and finally active granular carbon and H are generated₂Activated granular carbon is deposited on the surface and shallow layer of the pellet, and H₂Will undergo a reduction reaction with iron oxides that reach the reduction temperature.

The coal pyrolysis hydrogen reduction process of the carbon-containing pellets in the hydrometallurgy rotary hearth furnace comprises the following steps: in high-volatile coal such as brown coal, the content of hydrogen element is generally 4-5%, and H is obtained by full pyrolysis of coal₂About 70 percent of the red mud can be used for reducing the red mud, and the part H₂About 40 percent of oxygen elements in iron oxides in the pellets can be removed, and the process is called as a coal pyrolysis hydrogen reduction process.

The carbon gasification hydrogen reduction process of the carbon-containing pellets in the hydro-metallurgy rotary hearth furnace comprises the following steps: h produced by coal pyrolysis₂Reduction of iron oxide to produce H₂O，H₂O reacts with newly generated active granular carbon or dead carbon to generate carbon gasification reaction (H)₂O+C→H₂+ CO) to H₂And CO, H₂Reducing iron oxide as reducing agent to obtain H₂O will gasify carbon to generate new H₂And co. Because of the selectivity of chemical reaction, only a small part of CO generated in the process participates in the reaction of reducing iron oxide, most of CO is discharged into a hearth to be used as fuel, and about 50 percent of oxygen elements in iron oxide in the pellets can be removed through the processThe process is called "carbon hydrogen gas reduction process".

Carbon reduction process of the carbon-containing pellets in the hydrometallurgy rotary hearth furnace: only when the volatilization analysis of the reduced coal in the pellets reaches a certain degree, the iron oxide in the pellets and the stagnant carbon generated by the pyrolysis of the coal are subjected to CO₂Is carbon gasification reaction (CO) of gasification agent₂+ C → 2 CO) as core, the reduction rate of iron oxide in the ball is only about 10%, and the process is called as carbon reduction process.

The red mud reduction is established on the basis of hydrogen metallurgy, the process energy consumption of the hydrogen metallurgy rotary hearth furnace is greatly reduced, namely, the effective heat for reducing iron oxide and physically heating materials is greatly reduced, which means that the capacity is greatly improved on the premise of the same heat transfer capacity. More importantly, the reaction temperature point of hydrogen metallurgy is low, iron oxide is reduced at lower temperature, and the temperature is lower when active particle carbon participates; because the heat transfer quantity depends on the difference between the temperature of the hearth and the temperature of the material, more heat can be transferred into the material layer under the same temperature of the hearth, and the use efficiency of the heat is improved.

The invention realizes the high integration of the coal full pyrolysis process and the red mud metallurgical reduction process in a thermal state, and the whole iron making process only adopts high-volatile coal such as lignite and the like, so that coking coal is not needed. The reduction of iron oxides is converted from the traditional metallurgical coke-based carbon metallurgy process to "H" iron₂The hydrogen metallurgy process mainly comprising activated granular carbon achieves the purposes of energy conservation and emission reduction of the iron making process.

The invention has the beneficial effects that:

1. the invention adopts the rotary hearth furnace low-temperature hydrogen metallurgy technology for the red mud, so that the Fe in the red mud can be ensured₂O₃Direct quilt H₂The reduction temperature is reduced to 900-1000 ℃, and the red mud does not generate Fe in the reduction process at the temperature₂SiO₄Liquid phase, iron oxide in red mud can be directly reduced into metallic iron with high efficiency in solid state.

2. The process has the core equipment of the rotary kiln, compared with the rotary kiln process, the rotary kiln is easy to form rings when the temperature in the rotary kiln is too high, the normal production and the product index are influenced after the rings are formed in the rotary kiln, the rotary kiln does not have the ring formation problem in the rotary kiln, and the normal production of the rotary kiln can be ensured as long as the temperature of the rotary kiln is controlled below the softening point temperature of materials.

3. High volatile coal is used as a reducing substance, and a large amount of H can be generated after the high volatile coal in the red mud carbon-containing pellets is fully pyrolyzed₂，H₂Formation of gaseous H after reduction of iron oxides₂O，H₂Gasifying carbon O and generating new H₂And CO, H₂Reducing the iron oxide; due to the selectivity of chemical reaction, H is used in the whole red mud reduction process₂Reduced mainly to H₂The method is easy to obtain, can be used in production and production, and realizes the thermal intersection of the coal full pyrolysis and the iron oxide reduction process.

4. The iron-containing red mud is high in reduction speed at high temperature in the rotary hearth furnace, the reaction temperature point of hydrogen metallurgy is low in the red mud reduction process, more heat can be transferred into a material layer at the same hearth temperature, so that the reduction speed of the pellets is accelerated, and the process energy consumption is low; under the premise of the same heat transfer quantity, the capacity of a single furnace is greatly improved,

5. the invention adopts the rotary hearth furnace hydrogen metallurgy process for the red mud, the rotary hearth furnace is a closed system, the micro negative pressure operation is carried out in the furnace, the pollution emission is basically avoided in the production process, the final solid product and the purified flue gas meet the environmental protection requirement, and the flue gas waste heat is fully utilized. In addition, the reducing agent uses high-volatile coal, the fixed carbon content of the reducing agent is low, the hydrogen element content of the reducing agent is high, and H is used in the metallurgical reduction process₂Reducing mainly CO in the discharged flue gas₂Compared with the traditional iron burning process, the content is greatly reduced, and the essential emission reduction is realized.

Drawings

FIG. 1 is a schematic flow chart of the present invention.

Detailed Description

The invention is illustrated in further detail below by means of specific examples.

As shown in fig. 1, the iron-containing red mud coal-based direct reduction system comprises a mixer, a pelletizer, a chain grate, a hydrometallurgy rotary hearth furnace, an oxygen-free cooling device, a dry mill and a dry magnetic separator which are connected in sequence; the mixer is also connected with a dry-type ore mill and a dry-type coal mill, and the dry-type ore mill and the dry-type coal mill are respectively connected with a red mud dryer and a coal dryer; the hydrogen metallurgy rotary hearth furnace is also connected with a heat accumulating type heat exchanger for providing high-temperature hot air for the hydrogen metallurgy rotary hearth furnace, the heat accumulating type heat exchanger is connected with a blower, the heat accumulating type heat exchanger is connected with a chain grate machine, a red mud dryer and a coal dryer, the outlet flue gas of the heat accumulating type heat exchanger is used as a heat source to dry materials, the chain grate machine, the red mud dryer and the coal dryer are connected with a dust removal system, the dust removal system is connected with a smoke extractor, and the flue gas discharged after the materials are dried is purified by the dust removal system and then is discharged by the smoke extractor in a pressurizing manner; the dry magnetic separator is connected with an iron powder cold pressing device and a strong base leaching device, iron powder passes through the iron powder cold pressing device to obtain an iron powder product, and high-aluminum tailings pass through the strong base leaching device to obtain an aluminum oxide product.

The specific process for directly reducing the iron-containing red mud coal base by using the system comprises the following steps:

(1) raw materials are selected: 25-35% of TFe and Fe are adopted in the red mud₂O₃40 to 50 percent of Na₂2-5% of O and Al₂O₃21 to 25% of SiO₂15-20%, CaO 2-10%, H₂O is 5-10% of materials; the fuel and the reducing agent are lignite with 45-50% of volatile content (wherein the hydrogen content is 4-5%) and 43-48% of fixed carbon content;

(2) drying raw materials: drying and dehydrating the red mud and the lignite through a red mud dryer and a coal dryer after natural drying in the sun, controlling the external moisture content of the red mud and the lignite to be lower than 3%, wherein the heat sources of the red mud dryer and the coal dryer are from the smoke at the outlet of a heat accumulating type heat exchanger, and the smoke exhausted after drying is purified by a dust removal system and then is exhausted by a smoke extractor under pressure;

(3) dry milling to prepare powder: respectively grinding lignite to be more than 80% of-200 meshes (namely less than 200 meshes) and grinding red mud to be more than 90% of-200 meshes by adopting a dry coal mill and a dry ore mill;

(4) preparing carbon-containing pellets: red mud, brown coal, bentonite, high-grade iron ore concentrate (iron grade is more than 62%, SiO)₂Content of 6-8%) according to a ratio of 1:0.3:0.02:0.02, mixing uniformly, adding water by using a disc pelletizer, and pelletizing to obtain wet pellets with the particle size of 20-25 mm;

(5) wet ball drying: paving the wet balls on a grate material bed, drying by taking flue gas discharged from a heat accumulating type heat exchanger and having the temperature of 300-400 ℃ as a heat source, purifying the flue gas discharged after the materials are dried and having the temperature of 150-180 ℃ by a dust removal system, and then pressurizing and discharging by a smoke extractor;

(6) distributing materials in a rotary hearth furnace: conveying the dried pellets to a feeding end of a rotary hearth furnace, uniformly paving the pellets on the bottom of the rotary hearth furnace by a distributor, and controlling the paving thickness to be 60-70 mm;

(7) and (3) roasting in hydrogen metallurgy: h generated by full pyrolysis of coal in the process of heating pellets in a rotary hearth furnace₂And with H₂H generated by carbon gasification reaction with O as gasification agent₂The red mud is reduced, so that the high integration of the coal full pyrolysis process and the red mud metallurgical reduction process in a thermal state is realized, the temperature of a hearth is controlled to be 1250-1280 ℃, and the roasting time is controlled to be 30-35 min, so that the red mud can be fully reduced;

(8) self-heating balance: the method comprises the following steps that (1) flue gas at 900-1000 ℃ discharged by a rotary hearth furnace enters a heat accumulating type heat exchanger, high-temperature hot air at 850-900 ℃ is replaced, high-temperature combustible gas overflowing from a pellet material layer enters a hearth space in the reduction process of carbon-containing pellets in the rotary hearth furnace, the high-temperature combustible gas and the high-temperature hot air produced by the heat accumulating type heat exchanger are mixed and then combusted, and the generated heat can be used for meeting the heat requirement of the rotary hearth furnace;

(9) unloading: when the pellets reach the discharging area of the rotary hearth furnace, the pellets are continuously discharged through a spiral discharging device to obtain high-temperature metallized pellets at the temperature of 900-1000 ℃, wherein the metallization rate is 95%, the carbon content is 0.5%, and the cold strength is 1800N;

(11) and (3) cooling: cooling the high-temperature metallized pellets by an oxygen-free cooling device to obtain normal-temperature metallized pellets;

(12) dry grinding and dry separation: the metallized pellets are subjected to dry grinding and dry separation in a dry ore grinding machine and a dry magnetic separator, and iron powder and Al with the iron grade of 90 percent, the metallization rate of 95 percent and the metal recovery rate of 95 percent can be produced₂O₃The high-aluminum tailings with the content of 50 percent can produce an iron powder product after the iron powder is subjected to iron powder cold pressing, and can produce an aluminum oxide product after the high-aluminum tailings are subjected to a strong alkali leaching device, and meanwhile, the tailings are removed.