阅读说明：本技术 一种铁精矿回转窑煤基氢冶金-热造块-电炉生产半钢工艺 (Process for producing semisteel by coal-based hydrogen metallurgy, hot agglomeration and electric furnace in iron ore concentrate rotary kiln ) 是由 王明华 雷鹏飞 权芳民 张志刚 张小兵 卢红山 吴振中 胡建国 蔡斌 张红军 王 于 2021-07-21 设计创作，主要内容包括：本发明提供了一种铁精矿回转窑煤基氢冶金-热造块-电炉生产半钢工艺：将高挥发份煤种做还原剂及燃料,以回转窑为煤基氢冶金核心还原设备,在窑内实现煤的充分热解过程与铁精矿冶金还原过程在热态下的高度集成,将H-(2)作为铁精矿还原过程的主力还原剂,实现铁精矿的氢冶金；同时在铁精矿还原过程中伴有“铁晶须”生成,物料在窑内焙烧翻滚过程中相互交叉、团聚形成含碳金属化块料；铁精矿还原后残留一部分残炭,窑体发生挂料时,所挂物料含有的残炭燃烧产生热应力可将所挂物料自动清理。高温还原物料经无氧冷却、干式磁选后,得到的金属化块料再加入电炉进行深度还原和渣铁分离,可得到半钢水。(The invention provides a process for producing semisteel by using iron ore concentrate in a rotary kiln through coal-based hydrogen metallurgy, hot briquetting and an electric furnace, which comprises the following steps: high-volatile coal is used as a reducing agent and fuel, a rotary kiln is used as coal-based hydrogen metallurgy core reduction equipment, the full pyrolysis process of coal and the iron ore concentrate metallurgy reduction process are highly integrated in the kiln in a thermal state, and H is used 2 The hydrogen metallurgy of the iron ore concentrate is realized by taking the iron ore concentrate as a main reducing agent in the reduction process of the iron ore concentrate; meanwhile, the generation of iron whiskers is accompanied in the reduction process of the iron ore concentrate, and the materials are mutually crossed and agglomerated in the roasting and rolling process in the kiln to form the carbon-containing metallized lump materials; a part of carbon residue is remained after the reduction of the iron ore concentrate, and when the kiln body is hung, the hung material contains the carbon residueThe thermal stress generated by combustion can automatically clean the hung materials. After the high-temperature reduction material is subjected to anaerobic cooling and dry magnetic separation, the obtained metallized block material is added into an electric furnace for deep reduction and slag iron separation, and semi-molten steel can be obtained.)

1. A process for producing semisteel by using coal-based hydrogen metallurgy, hot agglomeration and an electric furnace in an iron ore concentrate rotary kiln comprises the following steps:

(1) screening high volatile coal with the granularity of 3-15mm into fine coal with the granularity of 3-8mm and coarse coal with the granularity of 8-15 mm;

(2) mixing iron ore concentrate and a liquid-phase modifying agent according to the proportion of 100 (0.5-1), mixing, pelletizing to obtain pellets with the granularity of 3-15mm, and adding the pellets and carbon residue with the granularity of more than 1mm into a kiln from a rotary kiln feeding end; respectively blowing and distributing 8-15mm coarse-grained coal and 3-8mm fine-grained coal to the front section and the middle section of a hydrogen metallurgy roasting area of the rotary kiln from the discharge end of the rotary kiln when the reduction is carried out for 60-70 min; controlling the reduction time of the iron ore concentrate in the rotary kiln to be 80-100min and the reduction temperature to be 1050-;

(3) discharging high-temperature reduced materials produced after the iron ore concentrate is reduced from the discharge end of the rotary kiln, and then cooling the materials in an oxygen-free cooling device;

(4) carrying out dry magnetic separation on the reduced material after cooling to obtain a magnetic material and nonmagnetic carbon residue;

after the nonmagnetic carbon residue is screened, obtaining a material with the diameter of 0-1mm as coal ash to be discharged outside, and obtaining carbon residue with the diameter of more than 1mm to be returned to a batching system for utilization;

screening the magnetic material to obtain a magnetic material of 0-10mm and a metallized block material larger than 10 mm; and (3) after the 0-10mm magnetic material is subjected to dry grinding and dry separation and is pressed by a cold press, adding the obtained metal block material and the metallized block material with the thickness of more than 10mm into an electric furnace, and performing deep reduction and slag iron separation on the electric furnace to obtain semi-molten steel.

2. The process for producing semisteel by using the iron ore concentrate rotary kiln coal-based hydrogen metallurgy, hot briquetting and electric furnace according to claim 1, wherein in the step (1), the high volatile coal is lignite, and the volatile content of the lignite is 35-49%, and the fixed carbon content of the lignite is 44-55%.

3. The process for producing semisteel by using the iron ore concentrate rotary kiln coal-based hydrogen metallurgy, hot briquetting and electric furnace according to claim 1, wherein in the step (2), the grade of the iron ore concentrate is 50-65%, and SiO is adopted₂The content is below 10%.

4. The process for producing semisteel by using the iron ore concentrate rotary kiln coal-based hydrogen metallurgy, hot briquetting and electric furnace according to claim 1, wherein in the step (2), the liquid-phase modifying agent is sodium carbonate or potassium carbonate.

5. The process for producing semisteel by using the iron ore concentrate rotary kiln coal-based hydrogen metallurgy, hot briquetting and electric furnace according to claim 1, wherein in the step (2), the adding amount of carbon residue with the granularity of more than 1mm is 10-20% of the mass of the pellet ore.

6. The process for producing semisteel by using the rotary kiln coal-based hydrogen metallurgy, hot briquetting and electric furnace of iron ore concentrate as claimed in claim 1, wherein in the step (2), 8-15mm coarse-grained coal and 3-8mm fine-grained coal are added in a total amount of 28-37% of the total amount of the iron ore concentrate.

Technical Field

The invention belongs to the technical field of metallurgy and mineral engineering, and relates to a process for producing semisteel by using an iron ore concentrate rotary kiln coal-based hydrogen metallurgy, hot agglomeration and an electric furnace.

Background

The traditional blast furnace iron making is a smelting technology using metallurgical coke as a reducing agent and fuel, and the process is a typical carbon metallurgy process. The annual capacity of blast furnace iron making all over the world is very large, a large amount of high-quality metallurgical coke needs to be provided for preparing molten iron, the high-quality metallurgical coke needs to be refined by expensive caking coking coal, the coking coal only accounts for 8-10% of the total coal reserves in the world at present, and the coking coal resources are more and more scarce along with the continuous development of the steel industry; the traditional blast furnace iron-making process consumes high-quality metallurgical coke, has strict requirements on iron materials, needs high grade of the iron materials, and also needs to prepare the iron materials into pellets or lump materials with certain strength through a sintering or pelletizing process, has long production process flow, and simultaneously has at least three processes of sintering (or pelletizing), coking and iron-making in the whole iron-making process, which relate to waste gas emission.

In the non-blast furnace ironmaking process, the direct reduction of iron ore is to reduce iron oxide in the iron ore into metallic Fe in a reaction vessel by a gas or solid reducing agent in a solid state, so that the iron ore is reduced into a metallized charging material, then the metallized charging material is cold-pressed into a metallized block material, and the metallized block material is melted and separated by an electric furnace to produce molten iron. At present, iron and steel enterprises have commercialized and operated two-step melting reduction ironmaking processes COREX and FINEX, which are the most successful non-blast furnace ironmaking technologies, but the iron and steel enterprises still do not completely get rid of the dependence on coke, and the consumption of per ton of iron and coke is 50-200 kg. The iron ore gas-based shaft furnace direct reduction technology is rapidly developed abroad, and for countries with abundant natural gas resources and short coking coal resources, the technology can produce high-quality sponge iron with low price. Because of the shortage of natural gas resources in China and the high price of industrial electricity, the processes of producing sponge iron by directly reducing iron ores by using a gas-based shaft furnace and producing molten iron by melting and separating by using an electric furnace are limited. Therefore, a novel non-blast furnace ironmaking process is developed, various iron ore resources are comprehensively treated, the energy consumption and pollutant discharge of molten iron smelting are reduced, and the international competitiveness of Chinese iron and steel enterprises can be improved.

When the traditional rotary kiln equipment is used for direct reduction of iron ore, because the direct reduction process of the iron ore rotary kiln adopts anthracite or metallurgical coke with high thermal shock resistance as a reducing agent and fuel and adopts a typical carbon metallurgy process, although a direct reduced iron product with the metallization rate of about 80 percent can be obtained, the further development of the direct reduced iron product is limited by inherent defects of poor raw fuel applicability, low productivity, high energy consumption, high cost, poor production stability and the like. When the metallized charging material is added into an electric furnace for use, the electric furnace needs to carry out final reduction of the material while carrying out material melting and slag iron separation due to the low metallization rate of the metallized charging material, so that the problems of long smelting time, low productivity, high energy consumption and the like of the electric furnace are caused.

For powdery iron ore, the coal-based direct reduction process of the iron ore rotary kiln needs to mix the iron ore, auxiliary additive raw materials and coal for pelletizing, the strength of the obtained green pellets entering the rotary kiln is required to be more than 600N/per pellet (generally, the green pellets enter an oxidizing roasting kiln for oxidizing roasting, and the strength of the green pellets can be greatly improved by oxidizing roasting), so that the rotary kiln cannot generate the pulverization phenomenon in the reduction process, and the iron ore is reduced into sponge iron at high temperature in the rotary kiln. Meanwhile, carbon reduction is adopted in the reduction of the iron ore, the reduction temperature is high, the reflow temperature of the materials is overlapped with the reduction temperature, liquid phase is easily generated in the reduction process of the iron ore, the reduction quality of the iron ore is influenced, and the metallization rate of the reduced materials is not high. The problems that it has are: the grade of the raw material iron used by the rotary kiln method is generally more than 50%, the reduction temperature of carbon-based reduction is higher, the reduction time is long, the requirement on the kiln feeding strength of the iron ore is higher, the production process is complex (oxidation roasting is needed before direct reduction), the cost is higher, and the problems of ring formation and the like exist in a kiln body in the roasting process.

The invention provides a process for producing semisteel by an iron ore concentrate rotary kiln through coal-based hydrogen metallurgy-hot briquetting-electric furnace, which aims to solve the problems that the traditional direct reduction process of an iron ore rotary kiln has high reduction temperature and long reduction time, the requirement on the strength of iron ore entering the kiln is high, the cost of the iron ore entering the kiln is high, the materials in the kiln cannot be agglomerated (the materials need to be agglomerated and enter the kiln for reduction), the ring of the kiln body is formed in the roasting process, and the like.

Disclosure of Invention

The invention relates to a process for producing semisteel by using coal-based hydrogen metallurgy, hot agglomeration and an electric furnace in an iron ore concentrate rotary kiln₂The metal block material and the metalized block material are added into an electric furnace together for reduction to obtain semi-molten steel.

A process for producing semisteel by using coal-based hydrogen metallurgy, hot agglomeration and an electric furnace in an iron ore concentrate rotary kiln comprises the following steps:

(1) screening high volatile coal with the granularity of 3-15mm into fine coal with the granularity of 3-8mm and coarse coal with the granularity of 8-15 mm; the high volatile coal is lignite, and the volatile content of the high volatile coal is 35-49% and the fixed carbon content of the high volatile coal is 44-55%.

(2) Mixing iron ore concentrate and a liquid-phase modifying agent according to the proportion of 100 (0.5-1), mixing, pelletizing to obtain pellets with the granularity of 3-15mm, and adding the pellets and carbon residue with the granularity of more than 1mm into a kiln from a rotary kiln feeding end; the liquid phase modifying agent is sodium carbonate or potassium carbonate;

the mixed material is continuously turned over in the rotary kiln along with the rotation process of the kiln body, and simultaneously flows from the feeding end to the discharging end; the mixed material is subjected to heat exchange with high-temperature flue gas which flows in a countercurrent manner in the flowing process of the rotary kiln, so that the temperature of the mixed material is increased, and the temperature of the flue gas is gradually reduced; mechanical H in iron ore concentrate when the temperature of the mixed material rises above 100 DEG C₂Removing O completely, and combining H when the temperature is raised to 200-300 DEG C₂Removing O; when the iron ore concentrate enters the front section of the hydrogen metallurgy roasting area of the rotary kiln, the temperature of the iron ore concentrate reaches about 800 ℃, the carbon in the carbon residue and the iron oxide in the iron ore concentrate start to perform reduction reaction, and the reaction productCO of₂The gas and carbon in the carbon residue are subjected to carbon gasification reaction to generate CO gas, and the CO is used as a reducing agent to reduce iron oxide in the iron ore concentrate, so that a coupling effect is formed, and the reduction reaction of the iron ore concentrate is continuously carried out; when the iron ore concentrate is added into the rotary kiln, a certain proportion of carbon residue is added, so that CO generated in the reduction process of the iron ore concentrate can be generated₂The CO content in the gas discharged from the material layer of the rotary kiln is up to 80-90%, and the gas can be used as the fuel of the rotary kiln to be combusted in the hearth.

When the reduction is carried out for 60-70min, the metallization rate of the reduction of the iron ore concentrate reaches about 70%, and the temperature of the mixed material reaches about 1000 ℃, respectively blowing 8-15mm coarse-grained coal and 3-8mm fine-grained coal from the discharge end of the rotary kiln to the front section and the middle section of a rotary kiln hydrometallurgy roasting area along the length direction of the kiln according to the process requirements by adopting compressed air, and rolling the high-temperature iron ore concentrate to enter a material layer and realize uniform mixing; controlling the reduction time of the iron ore concentrate in the rotary kiln to be 80-100min and the reduction temperature to be 1050-; when the mixed material sequentially passes through a drying preheating zone, a medium-temperature reducing zone, a high-temperature reducing zone and a hot agglomeration zone in the rotary kiln, the processes of reducing and agglomerating the iron ore concentrate are completed through drying and heating of the mixed material and reduction of the iron oxide.

The grade of iron ore concentrate is 50-65%, SiO₂The content is below 10 percent; the adding amount of the carbon residue with the granularity of more than 1mm is 10-20% of the mass of the pellet ore; the total adding amount of the coarse coal with the diameter of 8-15mm and the fine coal with the diameter of 3-8mm is 28-37 percent of the total amount of the iron ore concentrate.

(3) After being discharged from the discharge end of the rotary kiln, the high-temperature reduction material produced after the reduction of the iron ore concentrate enters an oxygen-free cooling device to carry out indirect heat exchange with normal-temperature air blown by a blower, so that the temperature of the reduction material is reduced to be below 150 ℃, the normal-temperature air blown by the blower is preheated to be 500-600 ℃, and the preheated air is blown from the kiln head of the rotary kiln to be used as combustion-supporting air of the rotary kiln for utilization;

(4) carrying out dry magnetic separation on the reduced materials discharged from the oxygen-free cooling device by using a dry magnetic separator to obtain magnetic materials and non-magnetic carbon residues; the non-magnetic carbon residue is subjected to particle size classification by adopting a vibrating screen, the particle size is divided into two particle size ranges of 0-1mm and more than 1mm, the carbon residue with the particle size of 0-1mm is discharged as coal ash, and the carbon residue with the particle size of more than 1mm is returned to a batching system for utilization; screening the magnetic material by a vibrating screen to obtain a magnetic material of 0-10mm and a metallized block material larger than 10 mm; after the magnetic material with the diameter of 0-10mm passes through a dry grinding and dry separation machine, tailings and metallized iron powder can be obtained, and the tailings are discharged; and briquetting iron powder by an iron powder cold press, adding the obtained metal lump material and the metallized lump material with the thickness of more than 10mm into an electric furnace, and deeply reducing and separating slag and iron by the electric furnace to obtain semisteel water and slag, wherein the slag is used as a building material, and the semisteel water is subjected to oxygen blowing smelting to obtain pure molten steel.

The high-temperature flue gas with the temperature of 600-700 ℃ discharged from the feeding end of the rotary kiln enters the waste heat boiler to indirectly exchange heat with normal-temperature water, so that water can be vaporized into high-temperature high-pressure steam while the temperature of the high-temperature flue gas is reduced to about 200 ℃, and the high-temperature high-pressure steam can be supplied to other users for utilization; the low-temperature smoke is purified by the dust removal system, and the clean smoke is pressurized by the smoke extractor and then discharged.

The invention arranges 2-4 kiln back fans at the front end and the middle end of the rotary kiln along the length direction of the kiln, the kiln back fans supply normal temperature air into the kiln along the length direction of the kiln according to the process requirements, and the blown combustion air can clean the combustible gas in the combustion space in the rotary kiln while adjusting the temperature in the kiln to be distributed along the length direction of the kiln.

The principle of the invention is as follows:

the mixed material consisting of the iron ore concentrate and the carbon residue is heated in the rolling process in the rotary kiln after being added into the rotary kiln, the temperature of the mixture rises continuously, when the mixture enters the middle section of the kiln body of the rotary kiln, the temperature of the mixture reaches over 1000 ℃, high volatile coal is sprayed from the discharge end of the rotary kiln, and the high volatile coal is distributed to the front section and the middle section of the kiln body along the length direction of the kiln according to the process requirement, the high volatile coal enters a material layer along with the material rolling and is uniformly mixed with other materials, at the moment, a material layer area formed by mixing iron ore concentrate, residual carbon and high volatile coal is formed in the rotary kiln, in the hot-state material layer of the area, a hydrogen metallurgy process which is mainly combined by oxygen element in iron ore concentrate, hydrogen element in high volatile coal and carbon element in stagnant carbon and is highly integrated by a coal full pyrolysis process, a water carbon gasification process and an iron oxide reduction process in a hot state can be generated.

H generated by fully pyrolyzing high volatile coal in the material bed of the hydro-metallurgical roasting area of the rotary kiln₂The produced high-temperature dead granular carbon with active granular carbon can roll along with the material layer and directly serve as a reducing agent for reducing iron oxide in a hot state. H₂H produced after reduction of iron oxides₂The O and the high-temperature stagnant granular carbon with the active granular carbon carry out carbon gasification reaction to generate H₂And CO, H₂Then used as a reducing agent to reduce iron oxide and generate new H₂Produce a severe coupling effect; due to the selectivity of the chemical reaction, most of CO overflows from the material layer and enters the combustion space of the rotary kiln to be used as fuel. Only when the volatile matter of high volatile coal in the material bed is completely separated out, the iron ore concentrate and high-temperature dead carbon are treated by CO₂A series of metallurgical reduction reactions taking carbon gasification reaction as a core.

After the pellet ore is fed into the kiln, the strength of the pellet ore is low, the pulverization phenomenon can be generated in the process that the material travels in the kiln, the heat transfer effect can be influenced after the material is pulverized, so that the reduction quality of the iron ore concentrate is influenced, and after the liquid-phase conditioning agent is added, the liquid phase can be generated in the material for secondary granulation.

Rotary kiln iron whisker agglomeration: when the rotary kiln directly reduces the iron ore concentrate on the coal base, the iron ore concentrate is added with carbon residue powder for granulation and then enters the rotary kiln, the iron ore concentrate is preheated, dried and pre-reduced in the process of advancing in the kiln, the reduction process of the iron ore concentrate is mainly the reduction of granular carbon base, granular iron oxide is continuously reduced into metallic iron, and a large amount of 'iron whiskers' is generated. In the front roasting stage, the low-temperature roasting reduction is realized by controlling the material temperature to be about 850 ℃; due to the heat transfer characteristic of the hot processing of the rotary kiln, the powdery material is heated in a high-temperature area directly from two aspects, namely the radiation heat transfer of flame to the surface of a material layer, and the radiation heat transfer of the kiln wall which is not covered with the material to the surface of the material layer, wherein the temperature of the surface of the material layer is far higher than the average material temperature, and a small amount of liquid phase is easily generated on the surface of the material layer; meanwhile, because a large amount of 'iron whiskers' are generated, the materials are mutually crossed and agglomerated in the roasting and rolling process to start secondary granulation, and carbon-containing metallized blocky materials with higher strength are formed.

In order to improve the granularity and strength of the metallized block material, the liquid phase conditioner is added before the pelletizing of the iron ore concentrate, after iron oxide in the iron ore concentrate is reduced into metallic iron in a rotary kiln, a large number of gaps can be generated in the material to reduce the strength, the strength of the material is improved, the agglomeration granularity of the material is increased, the gaps in the material can be contracted by the liquid phase generated after the liquid phase conditioner is liquefied at high temperature, the strength of the material is improved, and meanwhile, the liquid phase generated on the surface of the material can be adhered to powdery materials around the inside of the kiln, so that the agglomeration granularity of the material is increased.

Self-cleaning of the ring forming of the hydrogen metallurgy rotary kiln: adding excessive reducing coal into the iron ore concentrate in the reducing process in the rotary kiln, and remaining a part of carbon residue in the material after the reduction is finished, wherein when the reducing material is melted at high temperature in the kiln and is adhered to the inner surface of the rotary kiln to form hanging material, the hanging material contains a certain amount of carbon residue; when the hung material rotates to the kiln chamber space above the material along with the rotary kiln, the carbon residue contained in the material can be combusted under the action of high-temperature flue gas in the kiln, the temperature of the hung material around the carbon residue can be increased by the heat generated by the combustion of the carbon residue, the phenomenon of thermal stress generated in the material due to the difference of local expansion amount can occur in the hung material, and the hung material can drop when the thermal stress is accumulated to a certain degree.

According to the requirement of deep reduction of the carbon-containing metallized lump materials in the electric furnace, in order to ensure that 0.5-5% of carbon is remained in the carbon-containing metallized lump materials produced by the rotary kiln, high volatile coal with higher weight is sprayed in the reduction of the iron ore concentrate according to different iron grades of the iron ore concentrate.

The invention sprays excessive high volatile coal into the kiln from the kiln head through the spray gun in the reduction process of the iron ore concentrate, and a large amount of H is volatilized in the heating process of the high volatile coal₂And a higher reducing atmosphere concentration can be produced in the high-temperature reduction process of the iron ore concentrate. Due to H₂Of (a) a moleculeThe radius is much smaller than that of CO, the reduction capability and the gas penetration capability are better, and the iron oxide can be reduced without higher temperature in the reduction process. According to the condition that the energy consumption is larger when the reduction temperature of the iron ore concentrate is higher, the reduction temperature of 1050-1100 ℃ is adopted for reducing the energy consumption of the rotary kiln in the reduction process of the iron ore concentrate.

The invention has the beneficial effects that:

(1) the invention abandons the traditional high-temperature semisteel production process of sintering-coking-ironmaking-steelmaking of steel enterprises, adopts the short production process of direct reduction in a rotary kiln and deep reduction in an electric furnace, takes high-volatile coal as a reducing agent and fuel, takes iron ore concentrate as a raw material, produces a metallized block material by high-temperature roasting in the rotary kiln, and can produce high-temperature semisteel by deep reduction and slag-iron separation after the metallized block material is added into the electric furnace.

(2) In the process of reducing the iron ore concentrate in the rotary kiln, the reducing gas released by heating coal and the gas generated by carbon gasification reaction are used for reducing the iron ore concentrate, so that the concentration of the reducing gas in the process of reducing the iron ore concentrate can be improved, the reducing time of the iron ore concentrate is shortened, and the reducing quality of the iron ore concentrate is improved.

(3) When the rotary kiln directly reduces the iron ore concentrate on the coal base, the iron ore concentrate is added with carbon residue powder for granulation and then enters the rotary kiln, the iron ore concentrate is preheated, dried and pre-reduced in the process of advancing in the kiln, the reduction process of the iron ore concentrate is mainly the reduction of granular carbon base, granular iron oxide is continuously reduced into metallic iron, and a large amount of 'iron whiskers' is generated. Because of the generation of a large amount of 'iron whiskers', the materials are mutually crossed and agglomerated in the roasting and rolling process to start secondary granulation, and carbon-containing metallized blocky materials with higher strength are formed.

(4) A part of carbon residue is remained after the reduction of the iron ore concentrate, and when the kiln body is subjected to hanging, the hung material can be automatically cleaned by generating thermal stress through the combustion of the carbon residue contained in the hung material.

Drawings

FIG. 1 is a flow chart of a process of producing semisteel by using a rotary kiln coal-based hydrogen metallurgy, hot briquetting and an electric furnace for iron ore concentrate.

Detailed Description

The present invention is further illustrated by the following specific embodiments.

(1) Classifying the high volatile coal with the granularity of 3-15mm into 3-8mm fine coal and 8-15mm coarse coal by adopting a vibrating screen; the high volatile coal is lignite, and the volatile content of the high volatile coal is 35-49% and the fixed carbon content of the high volatile coal is 44-55%.

(2) Iron ore concentrate (the iron ore concentrate can be expanded into high-grade powdery iron ore, iron-containing dust mud and powdery iron slag) and a liquid-phase modifying agent (sodium carbonate) are subjected to batching, mixing and pelletizing according to the proportion of 100 (0.5-1), and the obtained pellets with the granularity of 3-15mm and carbon residue with the granularity of more than 1mm are added into a kiln from a rotary kiln feeding end; the grade of iron ore concentrate is 50-65%, SiO₂The content is below 10 percent; the adding amount of the carbon residue with the granularity of more than 1mm is 10-20% of the mass of the pellet ore.

(3) When the reduction is carried out for 60-70min, the metallization rate of the reduction of the iron ore concentrate reaches about 70%, and the temperature of the mixed material reaches about 1000 ℃, respectively blowing 8-15mm coarse-grained coal and 3-8mm fine-grained coal from the discharge end of the rotary kiln to the front section and the middle section of a rotary kiln hydrometallurgy roasting area along the length direction of the kiln according to the process requirements by adopting compressed air, and rolling the high-temperature iron ore concentrate to enter a material layer and realize uniform mixing; the adding amount of the carbon residue with the granularity of more than 1mm is 10-20% of the mass of the pellet ore; the total adding amount of the coarse coal with the diameter of 8-15mm and the fine coal with the diameter of 3-8mm is 28-37 percent of the total amount of the iron ore concentrate.

(4) After being discharged from the discharge end of the rotary kiln, the high-temperature reduction material produced after the reduction of the iron ore concentrate enters an oxygen-free cooling device to indirectly exchange heat with normal-temperature air blown by a blower, so that the temperature of the reduction material is reduced to below 150 ℃, the normal-temperature air blown by the blower is preheated to 500-600 ℃, and the preheated air is blown from the kiln head of the rotary kiln to be used as combustion-supporting air of the rotary kiln for utilization.

(5) Carrying out dry magnetic separation on the reduced materials discharged from the oxygen-free cooling device by using a dry magnetic separator to obtain magnetic materials and non-magnetic carbon residues; the non-magnetic carbon residue is subjected to particle size classification by adopting a vibrating screen, the particle size is divided into two particle size ranges of 0-1mm and more than 1mm, the carbon residue with the particle size of 0-1mm is discharged as coal ash, and the carbon residue with the particle size of more than 1mm is returned to a batching system for utilization; screening the magnetic material by a vibrating screen to obtain a magnetic material of 0-10mm and a metallized block material larger than 10 mm; after the magnetic material with the diameter of 0-10mm passes through a dry grinding and dry separation machine, tailings and metallized iron powder can be obtained, and the tailings are discharged; and briquetting iron powder by an iron powder cold press, adding the obtained metal lump material and the metallized lump material with the thickness of more than 10mm into an electric furnace, and deeply reducing and separating slag and iron by the electric furnace to obtain semisteel water and slag, wherein the slag is used as a building material, and the semisteel water is subjected to oxygen blowing smelting to obtain pure molten steel.

(6) High-temperature flue gas with the temperature of 600-700 ℃ discharged from the feeding end of the rotary kiln enters a waste heat boiler to indirectly exchange heat with normal-temperature water, so that water can be vaporized into high-temperature high-pressure steam while the temperature of the high-temperature flue gas is reduced to about 200 ℃, and the high-temperature high-pressure steam can be supplied to other users for utilization; the low-temperature smoke is purified by the dust removal system, and the clean smoke is pressurized by the smoke extractor and then discharged.