CN116949236A - Method and system for producing steel by reducing non-blast furnace step by step - Google Patents

Abstract

The present invention belongs to the technical field of metallurgical processing, and more specifically, relates to a method and system for step-by-step reduction of non-blast furnace steel production. First, iron ore powder is mixed with non-metallurgical coke reducing substances and solvents to form mixed raw materials, and then low-temperature pre-reduction is performed in a tubular fluidized bed reducer to reduce the oxygen content in the iron oxide and increase its metallization rate. A solid pre-reduction product is obtained; then, the pre-reduction product-iron concentrate with an increased metallization rate is heated in the melting furnace for high-temperature reduction. In the reaction product after high-temperature reduction, almost all carbon has been consumed, so the carbon content is extremely low. Therefore, after the reduction is completed, when the solid iron is continued to be converted into molten iron, there is no carbon source for carburization, which can make the carbon content of the molten iron fall within the range of the carbon content of steel, thereby achieving direct conversion from iron ore. The purpose of smelting target steel products.

Description

A method and system for step-by-step reduction of non-blast furnace steel production

Technical field

The present invention belongs to the technical field of metallurgical processing, and more specifically, relates to a method and system for step-by-step reduction of non-blast furnace steel production.

Background technique

Steel smelting is currently taking place around the world. It mainly relies on the process of blast furnace ironmaking, converter or electric furnace steelmaking, which is a process with a monopoly. But blast furnace ironmaking has its own shortcomings that are difficult to overcome. First of all, the iron ore raw materials used in the blast furnace, except for extremely high-grade lump ore, which can be directly smelted in the furnace, must be made into pellets in advance, and then sintered and hardened to reach 1,200 Newtons per ball before they can be used. This can ensure that when the raw material pellets are in a nearly molten state in the lower part of the blast furnace, they still have enough strength to ensure smooth ventilation inside the blast furnace. Fine powder with a particle size less than five millimeters cannot enter the blast furnace for smelting. They will block the ventilation gaps in the blast furnace and cause serious smelting accidents.

Secondly, in the lower part of the blast furnace, in order to maintain gas permeability, even if the molten iron drips on the reducing agent, the reducing agent still needs to have sufficient strength. Therefore, the reducing agent used in blast furnaces is expensive metallurgical coke. The coking process is a high energy consumption and high pollution process. The coking plant is also a unit with a large investment. Generally speaking, the investment in the coking plant accounts for about 1/4 of the investment in the entire iron plant.

Thirdly, blast furnace ironmaking has very high requirements on the grade of ore. If the grade of the iron ore fed into the furnace is too low, not only the economic benefits cannot be guaranteed, but it may also make it difficult to separate slag and iron. Theoretically, when the grade of the ore reaches a certain lower limit, the slag and iron cannot be separated. Therefore, lean ore cannot be directly smelted in the blast furnace.

Finally, there are some minerals that are difficult to smelt and cannot be smelted in a blast furnace. For example, the well-known vanadium-titanium magnetite cannot be smelted in a blast furnace. Under the smelting conditions of a blast furnace, titanium dioxide in iron ore will form titanium carbide with carbon in the reducing agent, and will also form titanium nitride with nitrogen in the air. These are substances with very high melting points. They cannot dissolve in the slag, but are suspended in the slag as tiny particles, causing the slag to be very viscous. These slags will block the ventilation gaps of the blast furnace, causing the blast furnace to pressurize, and even cause a catastrophic accident such as a blast furnace explosion!

There is another problem, which is also a helpless move that has led to the current two-step process of ironmaking and steelmaking: in the lower part of the blast furnace (mainly in the soft melt zone and dripping zone), the melted molten iron and the hot coke, Make close contact. This causes the smelted molten iron to be passively carburized, making its carbon content as high as 3% to 4.5%. Such a high carbon content limits its range of use. That's why people use oxygen to oxidize the carbon. This is the so-called steelmaking.

In order to solve the above-mentioned series of disadvantages of blast furnace ironmaking, the state clearly stipulates that non-blast furnace ironmaking is an encouraged project. Despite this, to this day, progress in non-blast furnace ironmaking is still not very obvious. Some methods other than blast furnaces can also be used to make iron. However, looking at various methods, there are either technical problems or economic problems, and they cannot be promoted on a large scale. Most of the patents make the ore and reducing agent into balls in advance to meet the conditions of "internal carbon". In fact, the term "internal carbon" itself leads people into a misunderstanding, "external carbon" It can fully meet the needs of reduction reaction. Some technologies will deliberately hot-press the materials into balls during the preheating process of non-blast furnace ironmaking, thereby increasing the strength of individual balls. This is closer to the blast furnace ironmaking process of pelletizing and sintering.

So the task before us is how to find a way to completely replace blast furnace ironmaking. The prerequisite is that the economic and technical indicators are better than blast furnace ironmaking.

Contents of the invention

The purpose of the present invention is to provide a method and system for step-by-step reduction of non-blast furnace steel production to solve the problem of severe carburization reaction, too long reduction time, and steel-making converter or electric furnace in the existing non-blast furnace ironmaking. problems, and overcomes technical problems such as complex processes and high steelmaking costs.

In order to achieve the above object, the present invention provides a step-by-step reduction method for non-blast furnace steel production, which includes the following steps:

(1) Mix iron ore powder, reducing agent and solvent to form mixed raw materials; the reducing agent is a non-metallurgical coke type carbonaceous reducing agent;

(2) The mixed raw materials are reduced for the first time in the dilute phase zone of the fluidized bed; during the first reduction process, the iron oxides in the iron ore powder are partially reduced by the reducing agent to obtain the first Sub-reduction solid products;

(3) The solid product of the first reduction is reduced for the second time in the dense phase zone of the fluidized bed; the iron oxide in the solid product of the first reduction is further reduced by the reducing agent, Obtain an iron concentrate in which the oxygen element is further reduced, but the iron still mainly exists in the form of oxide;

(4) The iron concentrate is sent to a melting furnace for smelting, the melting furnace is heated, and the remaining reducing agent during the heating process reduces the iron concentrate for the third time, and the iron concentrate is The iron oxide is reduced to solid iron particles; the temperature continues to be raised until the iron particles are converted into molten iron, and the scum in the upper layer of the melting furnace is discharged to obtain crude steel or crude iron products.

Preferably, the reducing agent in step (1) is biomass, coal, petroleum or natural gas; the solvent is calcium carbonate and/or fluorite.

Preferably, the mixed raw materials in step (1) are mixed powder; the size of the mixed powder is greater than or equal to 0.18mm, and more preferably 0.18-5mm.

Preferably, the first reduction process and the second reduction process are carried out in a fluidized bed, and the reduction temperature is 700-790°C; the fluidized bed includes an upper dilute phase zone and a lower dense phase zone, and the fuel Gas is introduced from the bottom of the dilute phase zone, so that the mixed raw materials undergo the first reduction in the dilute phase state of the fluidized bed, and the reduction time of the first reduction is less than or equal to 2 minutes; the dense phase zone Without passing the fuel gas, the solid product of the first reduction falls into the dense phase zone to perform the second reduction. The heat required for the second reduction process is provided by the waste heat of the first reduction. Provided that the restoration time of the second restoration is 1-30 minutes.

Preferably, the height-to-diameter ratio of the fluidized bed is 2-10.

Preferably, the melting furnace in step (4) is a gas-fired melting furnace or an electric melting furnace, more preferably an electric melting furnace, and the electric melting furnace is a medium frequency induction furnace or an electric arc furnace, even more preferably a medium frequency induction furnace.

Preferably, the residence time of the iron concentrate in the melting furnace in step (4) is 0.5-1 hour.

Preferably, the reduction furnace gas generated during the process of forming molten iron in step (4) is supplied to the fluidized bed as part of the fuel after being processed by the gas recovery system.

Preferably, the molar ratio of the C element in the reducing agent in step (1) to the O element in the iron ore powder is 1.05-1.15:1; step (4) continues to increase the temperature until the iron particles are converted into molten iron, and At this time, after the carbon content reaches the carbon content range required for the target steel product, the scum in the upper layer of the melting furnace is discharged, and the molten iron is contacted with the air to undergo a desulfurization, dephosphorization, and decarburization reaction to obtain a crude steel product.

Preferably, the method further includes the steps:

(5) Refining the crude steel product described in step (4) in a refining furnace or a refining ladle to obtain a target steel product, and using the target steel product directly as a casting raw material in a foundry; or use step (4) 4) The crude steel or crude iron products are directly used as casting raw materials in foundries.

According to another aspect of the present invention, a system for producing steel using the method is provided, including a fluidized bed and a melting furnace, wherein,

The fluidized bed includes an upper dilute phase section and a lower dense phase section. The top of the fluidized bed is provided with a mixed raw material inlet and a flue gas outlet of the fluidized bed. There is a gap between the upper dilute phase section and the lower dense phase section. fuel gas inlet;

The iron concentrate outlet provided at the bottom of the fluidized bed is connected to the iron concentrate inlet of the melting furnace. A melting furnace flue gas outlet is provided at the top of the melting furnace. The melting furnace flue gas outlet is connected to the flue gas. The treatment system is connected, and the flue gas treatment system is connected with the fuel gas inlet; the upper side of the melting furnace is also provided with a slag outlet, and the bottom is provided with a molten steel or molten iron outlet.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

(1) The invention proposes a step-by-step reduction method for producing steel without a blast furnace. First, before pre-reduction, the reducing agent, iron ore powder and various solvents are mixed and entered into a tubular pre-reduction reactor with a delayed reduction reaction section (fluidized bed dense phase section). This approach will bring the following benefits:

The first one is to contact the reducing agent with the iron ore in advance under the same conditions of providing reducing gas, which increases the carbon concentration of the reactants. It is known from the mechanism of chemical reactions that this is beneficial to the acceleration of the reduction reaction.

Second, after the reaction in the "dilute phase zone" in the upper part of the tubular reactor is completed, the reaction product will fall into the delayed reaction zone ("dense phase zone") in the lower part of the tubular reactor. Since the reactants also contain carbon and have a higher temperature, the reactants will continue to undergo reduction reactions while remaining in the "dense phase zone" of the delayed reaction section. As we all know: reaction temperature and reaction time are the two most important parameters of chemical reactions. Under the same temperature conditions, extending the reaction time will be beneficial to the progress of the chemical reaction. Raw materials without pre-prepared carbon cannot achieve this delayed reduction process. In the existing technology, the "fluidization method" is used for non-blast furnace ironmaking. Without exception, carbon is mixed in the final reduction reactor, without carbon being mixed in advance.

Third, the large height-to-diameter ratio of the tubular reactor reduces the degree of "back-mixing" of materials. In other words, the highly oxidized ore that initially enters the reactor meets the reducing agent with a higher carbon concentration, which increases the "driving force" of the reduction reaction, causing the reduction reaction to proceed quickly after the temperature is reached. When the reaction in the "dilute phase zone" of the tubular reactor ends, the carbon concentration in the reactants will decrease to a certain extent. The invention cleverly retains them in the "dense phase zone" of the delayed reduction section to continue reaction. Use extended time to compensate for lower carbon concentration and lower reduction temperatures.

Fourth, in the upper part of the tubular reactor, the flue gas fully preheats the reaction materials, so that the heat energy in the flue gas is fully utilized. The final exhaust gas temperature can be reduced to below 200 degrees Celsius.

Fifth, in the existing non-blast furnace ironmaking process, high-temperature, flammable, explosive and toxic reducing gases such as carbon monoxide are generally produced in the final reduction reactor. However, in the present invention, the fluidized bed tube is first Two-step pre-reduction is carried out in the reactor. The carbon monoxide and other reducing gases generated during the two-step reduction process can be used as fuel gas in the fluidized bed. Compared with the reducing gas generated by direct reduction in the final reduction reactor, the amount of reducing gas generated by the third reduction in the final reduction reactor after two-step pre-reduction in the present invention is greatly reduced, and the amount of reducing gas generated in the final reduction reactor is reduced. Producing a large amount of these high-temperature, flammable, explosive and toxic reducing gases places a burden on the reducing gas treatment system.

Sixth, the fluidized bed of the pre-reduction tubular reactor and the melting furnace of the final reduction reactor of the present invention jointly bear the task of reducing iron ore. Since the tubular reactor takes on more reduction tasks than the usual pre-reduction reactor, the subsequent electric melting furnace needs to take on a smaller reduction reaction task, so that low-value fuel can be used to replace expensive electricity.

(2) The present invention performs low-temperature (lower than 800 degrees Celsius) pre-reduction of iron ore. First, the first reduction is performed in the dilute phase section of the fluidized bed to reduce the oxygen content in the iron oxide of the iron ore and increase its metallization rate; Then a second reduction is performed in the delayed reduction section (dense phase section) to further reduce the carbon content and oxygen content. Finally, in the intermediate frequency electric furnace, after the final reduction of the iron ore is completed, the reducing agent carbon has been exhausted. When the molten iron is turned into molten iron, there is no carburizing agent, so that the carbon content of the molten iron reaches the carbon content range of the smelting target steel product. After appropriate removal of impurities, the target steel product can be obtained directly. The carbonaceous reducing agent of non-metallurgical coke is used as the reducing agent in the first and second pre-reduction steps, and the reducing agent carbon is completely consumed in the final reduction process of the third step in the melting furnace. In the method for step-by-step reduction of non-blast furnace steel production of the present invention, a "carbon starvation" strategy is adopted when mixing raw materials with carbon (C/O molar ratio in mixed raw materials = 1.05-1.15), so that when the pre-reduction reaction ends, the carbon content in the reducing agent Significantly reduced. Iron oxides in iron ores are partially reduced. Since they are not directly reduced to elemental iron in the pre-reduction step, they are still iron oxides (for example, they may be reduced from ferric oxide to ferric tetroxide or ferrous oxide), so they will not Carburizing reaction occurs. In the third reduction process, the pre-reduction product completes the third reduction during the heating process, and then after its reduction is completely converted into iron, it is converted into molten iron. At this time, the carbon content is very low and no leakage will occur. Carbon reacts, and at this time the carbon content is within the carbon content range of the steel product, and does not need to be supplemented by oxygen blowing. Therefore, the step-by-step reduction non-blast furnace ironmaking method of the present invention can directly obtain steel products.

(3) The present invention uses non-metallurgical coke as the reducing agent for pre-reduction. On the one hand, it can greatly save electric energy and save costs. On the other hand, the pre-reduction process can consume the carbon in the reducing agent and avoid the carburization reaction in the iron-making process. happened.

(4) For blast furnace ironmaking, iron ore powder must first be made into pellets, and the pellets must be sintered to make their strength reach 1200 Newtons per ball. In order to ensure the strength of the sintered pellets, reducing agents cannot be added to the pellets. The non-blast furnace step-by-step reduction method of the present invention directly adds the reducing agent, and does not need to sinter and harden the iron ore powder. The iron ore raw material used in the low-temperature pre-reduction of the present invention is powdery material, and its particle size is greater than 0.18mm and less than 5mm. Or you can select a certain granularity range within this range.

(5) Blast furnace ironmaking can only use expensive metallurgical coke as the reducing agent, and coking is also a highly energy-consuming and highly polluting process. The step-by-step reduction non-blast furnace ironmaking method of the present invention does not have any requirements on the strength of the reducing agent. Theoretically speaking, as long as it can be cracked and burned and the impurities are not too high, it can be used as a reducing agent. Therefore, the selection of reducing agents in the present invention is relatively broad. In the present invention, biomass is mixed with iron ore powder as a reducing agent, and the biomass is cracked and carbonized. The combustion of cracked gas can provide fuel for the pre-reduction reactor, and the carbon produced by carbonization is used as a reducing agent, which can fully utilize the functions of the biomass.

(6) Blast furnace ironmaking has high requirements on the taste of iron ore. The iron ore grade requirement of the present invention is very low and can reach below 40% or even lower. The method of the present invention can smelt vanadium-titanium magnetite, but the blast furnace cannot.

(7) The carbon content of blast furnace ironmaking is as high as 3% to 4.5%, and the carburization in the blast furnace is severe, which requires oxygen blowing for decarburization during further steelmaking. However, the present invention consumes almost all the reducing agent carbon before iron is transformed into molten iron, which means that we cut off the carbon source for "carburization" of iron. This means that the iron we smelt contains enough carbon to fall within the range of the carbon content of steel. This has truly achieved a leap from the two-step method of iron-making and steel-making to the one-step method of direct steel-making! Of course, conventional electric arc furnace steelmaking requires a refining furnace at the rear. The present invention can also routinely equip a refining furnace after the intermediate frequency electric furnace, and some individual element adjustments are left to the refining furnace to complete. This is a common steelmaking and refining method.

(8) The pre-reduction process of the present invention is a low-temperature reduction process, the temperature is lower than 800 degrees Celsius, and the fire resistance requirements of the equipment are low. The pre-reduction can be carried out in a protected stainless steel reactor, that is to say, it can be carried out in a hot wall reactor. .

Description of the drawings

Figure 1 is a flow chart of the method for step-by-step reduction of non-blast furnace steel production according to the present invention.

Figure 2 is a schematic diagram of the system for step-by-step reduction of non-blast furnace steel production according to the present invention.

Figure 3 is a picture of the third reduction process of the iron concentrate in the medium frequency induction furnace in Example 5 of the present invention.

Figure 4 is a photograph of the crude steel product obtained in Example 5 of the present invention.

Figure 5 is a photo of iron (steel) ingots obtained by cooling crude steel products obtained under different conditions in different embodiments of the present invention.

Throughout the drawings, the same reference numbers refer to the same elements or structures, wherein:

1-dilute phase section; 2-dense phase section; 3-mixed raw material inlet; 4-fuel gas inlet; 5-fluidized bed flue gas outlet; 6-iron concentrate outlet; 7-iron concentrate inlet; 8-melting furnace; 9-melting furnace flue gas outlet; 10-flue gas treatment system; 11-slag outlet; 12-molten steel or molten iron outlet.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

The invention provides a step-by-step reduction method for non-blast furnace steel production, as shown in Figure 1, including the following steps:

(1) Mix iron ore powder, reducing agent and solvent to form mixed raw materials; the reducing agent is a carbonaceous reducing agent for non-metallurgical coke;

(2) The mixed raw materials are reduced for the first time in the dilute phase zone of the fluidized bed; during the first reduction process, the iron oxides in the iron ore powder are partially reduced by the reducing agent to obtain the first Sub-reduction solid products;

(3) The first reduction solid product is subjected to a second reduction in the dense phase zone of the fluidized bed; during the second reduction process, the iron oxide is further reduced by the reducing agent to obtain iron concentrate , the oxygen element in the iron concentrate is further reduced, but the iron still mainly exists in the form of oxide;

(4) The iron concentrate is sent to a melting furnace for smelting, the melting furnace is heated, and the remaining reducing agent during the heating process reduces the iron concentrate for the third time, and the iron is The iron oxides in the concentrate are reduced to solid iron particles; the temperature continues to rise until the iron particles are converted into molten iron, and the scum in the upper layer of the melting furnace is discharged to obtain crude steel or crude iron products.

In some embodiments, the reducing agent in step (1) is biomass, coal, petroleum or natural gas; the solvent is one or more of calcium carbonate and fluorite.

The iron ore powders applicable to the non-blast furnace steel production method of the present invention include but are not limited to iron ore powders, and can also be other metal oxides that can be reduced by blast furnaces or electric furnaces, such as vanadium iron ore powder, vanadium titanium magnetite powder, Hematite powder, manganite powder, etc. can all fall within the scope of the present invention. The reducing agent can be non-metallurgical coke such as biomass, coal, petroleum or natural gas. The biomass can be rice husk, sawdust, plant straw, coconut shell, cassava residue, etc. During use, these biomass can be first compressed into blocks and then crushed to obtain biomass powder of suitable particle size, and then mixed with the iron ore powder. In a preferred embodiment, the particle size of the powder in the mixed raw materials is 0.18-5 mm.

Using the step-by-step reduction non-blast furnace production method of the present invention, the produced product can be controlled to be steel or iron by regulating the carbon-oxygen ratio in the mixed raw materials. When the carbon-to-oxygen ratio is high, molten iron can be obtained. In some embodiments, the molar ratio of the C element in the reducing agent in the mixed raw material of the present invention to the O element in the iron ore powder (abbreviated as C/O ratio in the present invention) is 1.05-1.15:1, preferably 1.05-1.12:1. Here, the molar amount of the C element refers to the fixed carbon content in the reducing agent, which can be obtained by pyrolysis analysis of the reducing agent; while the molar amount of the O element is obtained by analyzing the Fe grade in the iron ore powder, and then converting the iron element content After becoming Fe ₃ O ₄ , 4/3 times the Fe element is the oxygen element content, and finally this C/O ratio is obtained. Under this C/O ratio, experiments found that crude steel products can be obtained directly. In existing blast furnace or other non-blast furnace ironmaking methods, this C/O ratio is greater than 1.2. Therefore, the strategy adopted in the present invention's non-blast furnace one-step method of producing steel products is called the "carbon starvation" strategy.

The mixed raw materials of the present invention are also mixed with a solvent, and the solvent may contain calcium carbonate. During the partial reduction of iron ore powder in the fluidized bed of the present invention, the calcium carbonate decomposes to produce calcium oxide that can be used as a slagging agent, thereby saving energy. In addition, the present invention uses biomass reducing agent, and the carbon produced by pyrolysis and carbonization in the fluidized bed is used as a reducing agent to reduce iron ore powder. The combustion of the cracked gas generated during the cracking process can also provide heat for the reduction process.

In some embodiments, the mixed raw materials in step (1) are mixed powder; the size of the mixed powder is greater than or equal to 0.18mm, preferably 0.18-5mm. Experiments have found that the particle size of the mixed raw materials should not be less than 0.18mm, otherwise it will easily splash out during smelting in the melting furnace.

In some embodiments, the first reduction process and the second reduction process of the present invention are performed in a fluidized bed, and the reduction temperature is 700-790°C; the fluidized bed includes an upper dilute phase zone and a lower dense phase zone. Phase zone, the fuel gas is introduced from the bottom of the dilute phase zone, so that the mixed raw materials are reduced for the first time in the dilute phase state of the fluidized bed. The reduction time of the first reduction is based on the height-to-diameter ratio of the fluidized bed and the fuel Determined by the gas flow rate, it depends on the time for the material to fall, which is generally less than or equal to 2 minutes; the fuel gas is not introduced into the dense phase zone, and the solid product of the first reduction falls into the dense phase zone for the second reduction. The heat required for the second reduction process is provided by the waste heat of the first reduction, and the reduction time for the second reduction is 1-30 minutes. When used, the mixed raw materials are first placed in the dilute phase zone for a rapid first reduction, and the reduction time is less than or equal to 2 minutes, preferably controlled within 30 seconds; the first time obtained after the first reduction is completed The reduced solid product falls into the dense phase zone and continues reduction to obtain iron concentrate. One of the important reasons why the present invention chooses to perform pre-reduction in the fluidized bed at a temperature within 800 degrees Celsius is to control the pre-reduction product to be iron concentrate containing iron oxides rather than iron particles, so as to facilitate the unloading to the next reduction reactor melting furnace. Therefore, in the actual production process, the metallization rate of iron ore powder can also be judged based on the form of the solid product of the second reduction. If the degree of pre-reduction is too high and it is reduced to iron particles, the pre-reduction product may be bonded, resulting in The material cannot be released.

In some embodiments, the fluidized bed has an aspect ratio of 2-10. The total height of the fluidized bed is divided into a dense phase section (also called a dense phase zone) and a dilute phase section (also called a dilute phase zone). The total height of the fluidized bed is the sum of the heights of the dense phase section and the dilute phase section. In the present invention, the mixed raw materials are subjected to two-step reduction in the temperature range of 700-790°C. The purpose of the temperature being lower than 800°C is to control the reduction products from adhesion and facilitate smooth discharge to the melting furnace for the third reduction; the first time The reduction is a reduction process in a fluidized bed dilute phase state. At this time, the carbon content and oxygen content in the iron ore powder are high, and the reduction efficiency is high. The first reduction time can be controlled within 2 minutes; the second reduction is It is carried out in the dense phase fluidized bed at the lower part of the fluidized bed. In order to make up for the lack of reduction temperature, the second reduction increases the degree of reduction by extending the reduction time. At the end of the second reduction, the metallization rate of the iron ore powder increases to 60-80% and becomes iron concentrate, but the iron in the iron concentrate still exists in the form of oxides.

In some embodiments, the present invention performs the first reduction in the dilute phase section. By controlling the flow rate of the fuel gas and the amount of mixed raw materials, the amount of solid material per cubic meter (dilute phase reactor volume) in the dilute phase section is reduced. Within 100 kg, 30-60kg/m ³ is preferred, and 30-50kg/m ³ is more preferred. The material after the first reduction falls into the dense phase section for the second reduction. No fuel gas is blown into the dense phase section, and its solid material density is 800-1800kg/m ³ .

The present invention uses a tubular fluidized bed reactor containing an upper dilute phase zone and a lower dense phase zone with a "height to diameter ratio" of 2-10 to perform two-step pre-reduction, which has the following advantages: (1) The tubular reactor The large aspect ratio reduces the degree of "back-mixing" of materials. (2) The first reduction is carried out in the upper dilute phase fluidized bed. At this time, the carbon content and oxygen content in the iron ore powder are high, the reduction reaction rate is fast, the reduction efficiency is high, and the first reduction time is short and can be controlled. Within 2 minutes; (3) In the same tubular fluidized bed reactor, the upper dilute phase zone and the lower dense phase zone share a heating system, and the solid product of the first reduction falls directly into the dense phase fluidized bed. Carry out the second step of reduction and use the waste heat of the dilute phase fluidized bed to carry out the second reduction to save energy consumption.

In some embodiments, the melting furnace in step (4) is a gas-fired melting furnace or an electric melting furnace, preferably an electric melting furnace. The electric melting furnace includes but is not limited to a medium frequency induction furnace or an electric arc furnace, and is preferably a medium frequency induction furnace. . Gas-fired melting furnaces can use coal, liquefied gas, petroleum, etc. as fuel.

In the present invention, the iron concentrate obtained after two-step pre-reduction is sent to the melting furnace for smelting, the iron concentrate is heated in the melting furnace, and the remaining reducing agent reduces the iron concentrate for the third time during the heating process. , and reduce the iron oxides in the iron concentrate into solid iron particles; in some embodiments, the temperature continues to rise until the iron particles are converted into molten iron, and at this time the carbon content reaches the carbon content range required for the target steel product ; At this time, the upper scum is discharged to obtain crude steel products. The surface of the molten iron can also be brought into contact with the air in the melting furnace after slag discharge as needed. The oxidation reaction between the sulfur, phosphorus and carbon elements in the molten iron and the oxygen in the air can remove part of the sulfur, phosphorus and carbon in the molten iron. The process can be considered as a preliminary steelmaking operation to obtain crude steel products. The invention cleverly realizes two completely different reaction processes in the same furnace body of the melting furnace. The first is the reduction process of reducing iron concentrate and converting it into molten iron. The formation of upper scum maintains the reduction process; then the scum is discharged. The molten iron is exposed to the air to oxidize and remove sulfur, phosphorus, carbon, etc. in the molten iron. This process is the preliminary steelmaking process. Therefore, the present invention can realize the process of first making iron and then making steel in the same furnace body of the melting furnace.

In some embodiments, the residence time of the iron concentrate in step (4) in the melting furnace is 30-60 minutes. Among them, the third reduction to molten iron generally takes 25-50 minutes, and the slag removal and preliminary steelmaking processes generally take 5-10 minutes.

In some embodiments, the reduction furnace gas generated during the process of forming molten iron in step (4) is processed by the gas recovery system and then supplied to the fluidized bed as part of the fuel.

In some embodiments, the crude steel product described in step (4) is refined in a refining furnace or a refining ladle to obtain a target steel product, and the target steel product is directly used as a casting raw material in a foundry; or The crude steel or crude iron products described in step (4) are directly used as casting raw materials in foundries.

The present invention also provides a system for producing steel by applying the method. As shown in Figure 2, in the following embodiments of the present invention, a system for producing steel by a step-by-step reduction non-blast furnace one-step process includes a fluidized bed and a melting furnace, wherein The fluidized bed includes an upper dilute phase section 1 and a lower dense phase section 2. The top of the fluidized bed is provided with a mixed raw material inlet 3 and a fluidized bed flue gas outlet 5. The upper dilute phase section 1 and the lower dense phase section are provided. A fuel gas inlet 4 is provided between sections 2; the iron concentrate outlet 6 provided at the bottom of the fluidized bed is connected to the iron concentrate inlet 7 of the melting furnace 8, and a melting furnace smoke is provided at the top of the melting furnace 8 Gas outlet 9, the melting furnace flue gas outlet 9 is connected to the flue gas treatment system 10, the flue gas treatment system 10 is connected to the fuel gas inlet 4; the upper side of the melting furnace 8 is also provided with The slag outlet 11 is provided with a molten steel or molten iron outlet 12 at the bottom.

When this system is used, the mixed raw materials enter the dilute phase section 1 of the fluidized bed from the mixed raw material inlet 3 provided at the top of the fluidized bed, and the fuel gas required for the fluidized bed reduction process flows from the dilute phase in the upper section The fuel gas inlet 4 between section 1 and the lower dense phase section 2 enters the fluidized bed, so that the mixed raw material becomes a dilute phase state in the dilute phase section 1, and the first reduction is performed in the dilute phase section Process; the first reduction solid product falls into the dense phase section 2 after reduction, and the second reduction process is performed in the dense phase section to obtain iron concentrate; the smoke generated by low-temperature pre-reduction in the fluidized bed The gas flows out from the fluidized bed flue gas outlet 5. The iron concentrate obtained by the second reduction is transported from the iron concentrate outlet 6 at the bottom of the fluidized bed to the iron concentrate inlet 7 at the top of the melting furnace, where it is heated in the melting furnace and completed in sequence. After the third reduction of the iron concentrate, molten iron and slag removal, the crude steel product obtained is discharged from the molten steel or molten iron discharge port 12 at the bottom of the melting furnace; wherein the scum is discharged from the molten steel discharging port 12 provided on the melting furnace. The slag discharge port 11 is discharged; the flue gas generated by reduction in the melting furnace enters the flue gas treatment system 10 from the flue gas outlet 9 of the melting furnace, where it is removed, cooled, and compressed in the flue gas treatment system 10. The fuel gas is delivered to the inlet 4 of the fluidized bed and supplied to the fluidized bed as part of the fuel.

The fuel gas introduced into the fuel gas inlet 4 of the present invention is a mixture of combustible gas and air. Part of the combustible gas comes from the combustible gas containing carbon monoxide and the like flowing out of the melting furnace flue gas outlet 9, and is treated by the flue gas treatment system. Gas; the other part can be external supplementary gas such as gas produced by biomass fuel cracking, natural gas, liquefied petroleum gas, coal gas, etc. The fuel gas generated by the cracking of biomass fuel can be collected according to the existing conventional cracking and collection methods and used as the combustible gas for the fluidized bed reduction fuel gas of the present invention.

Since the present invention can directly smelt iron ore into steel by controlling the amount of carbon, it can also smelt iron ore into iron by increasing the amount of carbon. In other words: this invention can decide whether to make iron or steel according to our needs. In addition, since the present invention can use iron ore to directly refine iron or steel, there is no need to use iron or steel as raw material in the foundry. Iron ore can be directly used as raw material, and the iron ore obtained according to the production method of the present invention can be used. Crude steel products are used directly as raw material in foundries.

The step-by-step reduction method for non-blast furnace production of steel in some embodiments of the present invention is actually a step-by-step reduction method for non-blast furnace smelting of steel using iron ore powder. The iron ore powder and reducing agent powder are directly mixed as raw materials. In particular, a "thin and tall" fluidized bed is used as a low-temperature pre-reduction reactor, combined with the "carbon starvation" strategy. First, the first rapid reduction is performed in the dilute phase zone of the fluidized bed, and then the waste heat in the dilute phase zone is used in the lower flow The second reduction is carried out in the dense phase area of the bed, and the iron concentrate obtained after reduction is sent to the melting furnace. In the same furnace body, the third reduction, molten iron melting, slag removal and partial desulfurization are completed sequentially along with the temperature rise process. In the steelmaking operation of dephosphorization and decarburization, the crude molten steel obtained in some embodiments has met the requirements of medium carbon steel and even low carbon steel products, and the iron (steel) yield can be as high as more than 96% in most cases, achieving Unexpected technical effects. In some embodiments, in order to obtain lower carbon content, the C/O ratio is small. It seems that the carbon starvation strategy affects the iron yield, making the iron yield only 91%. However, it should be pointed out that for the blast furnace For example, even if the carbon content is reduced and part of the iron yield is sacrificed, steel cannot be smelted in one step as in the method of the present invention. The iron-making principle of the blast furnace determines that once molten iron is generated, carburization reaction will inevitably occur.

The invention proposes a step-by-step reduction method for producing steel without a blast furnace. Specifically, first, the metal oxide is pre-reduced at low temperature to reduce the oxygen content and increase the metallization rate, which is suitable for the smelting process of medium-frequency induction furnace to smelt iron and then produce metals such as steel. As we all know, the entire ironmaking process is a process in which the ore gradually loses oxygen. As the ore gradually loses oxygen, its metallization rate is also increased. The advantage of pre-reducing iron ore at a low temperature stage is that lower value fuels can be used for heating, and we can even use biomass fuel for heating. The low-temperature reduction process allows us to save expensive electricity. This pre-reduction process is also a preheating process of raw materials. And when we use biomass fuel, we can achieve zero carbon emissions. Because when we burn biomass fuel, the carbon dioxide released is exactly the same amount of carbon dioxide absorbed from the atmosphere through photosynthesis during their growth.

Then, in the low-temperature pre-reduction stage, the oxygen content in the iron ore drops significantly and the metallization rate increases significantly. In our experiment, the solid material obtained in the low-temperature pre-reduction stage in the fluidized bed was weighed. Their weight is not only lower than the original input weight, but also lower than the individual weight of the input iron ore. This means that the carbon and oxygen in the reactants form carbon monoxide and carbon dioxide, which are discharged into the air. Resulting in a reduction in overall solid matter weight. It is precisely because the oxygen content in the iron ore is reduced that its metallization rate increases to the point where an induction furnace can be used to melt iron. Before the iron-forming process, as the temperature in the furnace increases, the concentrate powder and remaining reducing agent continue to reduce. All concentrates have completed the reduction process before turning into molten iron. This is the process of converting iron, ingeniously realizing the two production processes of final reduction of concentrate and converting iron.

Finally, the induction furnace uses electric current to apply a magnetic field to the induced metals or low-oxidation minerals, causing them to heat up. This process saves electricity. Today's general steel smelting uses electric arc furnaces, which we often call submerged arc furnaces. This kind of electric furnace does not rely on the induction of metal to heat, but relies on the discharge between electrodes to trigger an arc to heat the raw materials. The temperature of the arc reaches more than 3,000 degrees Celsius. Making steel using an electric arc furnace consumes more electricity than using an induction furnace. Moreover, at high temperatures, the electrode consumption of electric arc furnaces is also an expense that cannot be ignored. The method of stepwise reduction of non-blast furnace-generated steel according to the present invention has greatly improved the metallization rate in the iron ore powder in the first two steps of pre-reduction. Therefore, a medium-frequency induction furnace with lower energy consumption can be used for the third step. Reduction greatly saves energy consumption compared to the existing electric arc furnace or submerged arc furnace.

The invention first mixes iron ore with non-metallurgical coke reducing substances and additives to form a mixture and then performs low-temperature pre-reduction to reduce the oxygen content in the iron oxide, increase its metallization rate, and obtain a solid pre-reduction product; then, metallization The pre-reduction product with increased efficiency, iron ore concentrate, is heated in the melting furnace for high-temperature reduction. In the reaction product after high-temperature reduction, almost all carbon has been consumed, so the carbon content is extremely low. Therefore, after the reduction is completely completed, when the solid iron is continued to be converted into molten iron, there is no carbon source for carburization, so that the carbon content of the molten iron has fallen within the range of the carbon content of steel, thus achieving the goal of transforming the solid iron into molten iron. The purpose of the ore is to directly smelt target steel products.

The production of steel in the following examples is carried out in the production system as shown in Figure 2. The step-by-step reduction of non-blast furnace steel produced by the present invention is a partially discontinuous and overall continuous production method. The mixed raw materials are continuously fed from the raw material inlet at the top of the fluidized bed into the dilute phase section for the first reduction. After the reduction is completed, it falls into the dense phase section for the second reduction. Secondary reduction. After the reduction is completed, the iron concentrate that reaches the required reduction level is taken out in batches from the iron ore concentrate outlet at the bottom of the fluidized bed and sent to the medium frequency induction furnace for smelting. Of course, it can also be used with multiple medium frequency induction furnaces to meet production requirements. Require.

The following are examples:

Example 1

To magnetite with a grade of 67wt% (meaning Fe content is 67wt%), add 18wt% of anthracite coal with a calorific value of 5500 kcal (the amount added is 18wt% of the total mass of the magnetite, the same below) and 10wt% of straw. , add 9wt% calcium carbonate and 6wt% fluorite. The C/O molar ratio in the mixed raw materials is 1.11. The above raw materials are mixed in a mixer, sieved to obtain powder raw materials with a particle size in the range of 1-3 mm, and added from the upper mixed raw material inlet of a tubular reduction reactor with a height-to-diameter ratio of 4. The mixed raw materials first undergo the first reduction in the dilute phase section of the tubular reduction reactor, and then fall into the dense phase section for the second solid state reduction. A mixture of liquefied petroleum gas and air (volume ratio 1:50) is introduced into the fuel gas inlet of the reduction reactor, and the furnace temperature is controlled at 700-750 degrees Celsius (the furnace temperature is controlled within this range by controlling the feed and fuel gas volume). The average reduction reaction time in the "dilute phase section" is 15 seconds, and the solid material density in the dilute phase section is 35kg/m ³ . In the dense phase delayed reduction section, the average reduction time is 20 minutes, and the solid material density in the dense phase section is 1000kg/m ³ . The iron concentrate produced by the reaction is taken out from the lower part of the reactor. The product of the pre-reduction reaction directly enters the medium frequency induction furnace and is heated to the temperature of molten iron (1400-1450 degrees Celsius). During the heating process, the third reduction is completed and transformed into molten iron. The slag is discharged. S, P, C and S in the molten iron are The oxygen in the air undergoes a desulfurization and dephosphorization reaction for 8 minutes to obtain crude steel products. In the test, the iron conversion rate was 96.45%, and the carbon content of the molten iron was: 0.94%.

Comparative example 1

Other conditions are the same as in Example 1, except that the mixed raw materials are sieved to have a particle size of less than 80 mesh (0.18 mm). The mixed raw materials are solid-state reduced in the reduction reactor. The fuel gas of the reduction reactor is a mixture of liquefied petroleum gas and air (volume ratio 1:50), and the furnace temperature is controlled at 700-750 degrees. The average reduction reaction time in the "dilute phase section" is 15 seconds, and the solid material density in the dilute phase section is 35kg/m ³ . In the delayed reduction section, the average reduction time is 20 minutes, and the solid material density in the dense phase section is 1000kg/m ³ . The concentrate produced by the reaction is taken out from the lower part of the reactor. The product of this pre-reduction reaction directly enters the induction electric furnace. During the process of converting iron, the material splashes out from the crucible of the intermediate frequency furnace. It can be seen that iron ore with too small particle size, especially iron ore with less than 80 mesh, will have certain difficulties in processing by this method if it does not agglomerate.

Example 2

In order to confirm the effect of the "carbon starvation" strategy, we deliberately added additional carbon to the experiment. Let’s see how the carbon content of the molten iron obtained according to the method of Example 1 will change without providing “carbon starvation”.

Other conditions are the same as Example 1, except that the added amount of straw is replaced from 10wt% in Example 1 to 15wt%, and the C/O molar ratio in the mixed raw materials is 1.2. The final product was tested and found to have an iron conversion rate of 96.88% and a carbon content of molten iron of 3.57%. It can be fully seen from this example: "Carbon starvation" is indeed an effective way to reduce the carbon content of molten iron. In other words, the present invention can either directly smelt iron ore into steel or smelt them into iron.

Example 3

The fine powder of vanadium-titanium magnetite with a grade of 50wt% and a particle size of 0.18-1 mm is added with 16.5wt% of carbonized coconut shell, 6wt% of fluorite and 6wt% of calcium carbonate. The C/O molar ratio in the mixed raw materials is 1.09. The above-mentioned raw materials are mixed in a mixer and sieved to obtain a powder mixture with a particle size in the range of 0.8-5 mm. The raw materials are added from the top of a tubular reduction reactor with a height-to-diameter ratio of 3. The mixed raw materials are solid-state reduced in the reduction reactor. The fuel gas of the reduction reactor is a mixture of straw gas produced by carbonization and cracking of biomass fuel and air (volume ratio 1:40). The furnace temperature is controlled at 750-790 degrees Celsius. The average reduction reaction time in the "dilute phase section" is After 10 seconds, the density of the solid material in the dilute phase section is 40kg/m ³ . In the delayed reduction section, the average reduction time is 25 minutes, and the solid material density in the dense phase section is 1200kg/m ³ . The iron concentrate produced by the reaction is taken out from the lower part of the reactor. The product of the pre-reduction reaction directly enters the medium frequency induction electric furnace and is heated to the temperature of molten iron (1400-1450 degrees Celsius). During the heating process, the third reduction is completed and transformed into molten iron, slag is discharged, and S, P, C and air in the molten iron are mixed with each other. The oxygen in the steel undergoes desulfurization, dephosphorization and decarburization reactions for 10 minutes to obtain crude steel products. The iron conversion rate was tested to be 96.01%. The carbon content of iron (steel) water is 0.45%. This carbon content is the carbon content of medium carbon steel (such as No. 45 steel).

Example 4

For magnetite with a grade of 67%, 21wt% of carbonized coconut shells, 9wt% of calcium carbonate and 6wt% of fluorite are added. The above raw materials are mixed in a mixer, sieved to obtain mixed powder raw materials with a particle size of 0.18-2 mm, and added from the upper part of a tubular pre-reduction reactor with a height-to-diameter ratio of 6. The C/O molar ratio in the mixed raw materials is 1.03. The raw materials are solid-state pre-reduced in the pre-reduction reactor. The average reduction reaction time in the "dilute phase section" is 20 seconds, and the solid material density in the dilute phase section is 45kg/m ³ . In the delayed reduction section, the average reduction time is 30 minutes, and the solid material density in the dense phase section is 1200kg/m ³ . The fuel gas in the pre-reduction reactor is a mixture of liquefied petroleum gas and air (volume ratio 1:50), and the furnace temperature is controlled at 750-790 degrees Celsius. When the reduction reaction ends, the solid concentrate generated by the reaction is taken out from the lower part of the reactor. The product of the pre-reduction reaction directly enters the medium frequency induction electric furnace and is heated to the temperature of molten iron (1400-1450 degrees Celsius). During the heating process, the third reduction is completed and transformed into molten iron, slag is discharged, and S, P, C and air in the molten iron are mixed with each other. The oxygen in the steel undergoes desulfurization, dephosphorization and decarburization reactions for 10 minutes to obtain crude steel products. The iron (steel) yield reaches 91.74%, and the carbon content is as low as 0.05%, which is close to the national carbon content requirements for ultra-low carbon steel.

Example 5

For iron ore with a grade of 40wt%, 15wt% of carbonized coconut shells, 5wt% of fluorite and 5wt% of calcium carbonate are added. The above raw materials are mixed in a mixer, sieved to obtain powder mixed raw materials with a particle size range of 1-5 mm, and added from the upper part of the reduction reactor. The C/O molar ratio in the mixed raw materials is 1.08. The raw materials are solid-state pre-reduced in a tubular pre-reduction reactor with a height-to-diameter ratio of 6. The fuel of the pre-reduction reactor is a mixture of liquefied petroleum gas and air (volume ratio 1:50), and the furnace temperature is controlled at 700-750 degrees Celsius. The average reduction reaction time in the "dilute phase section" is 20 seconds, and the solid material density in the dilute phase section is 45kg/m ³ . In the delayed reduction section, the average reduction time is 30 minutes, and the solid material density in the dense phase section is 1200kg/m ³ . The solid concentrate produced by the reaction is taken out from the lower part of the reactor. The product of the pre-reduction reaction directly enters the medium frequency induction electric furnace and is heated to the temperature of molten iron (1400-1450 degrees Celsius). During the heating process, the third reduction is completed and transformed into molten iron. The photo of the third reduction process is shown in Figure 3 , flames can be observed during the reduction process, indicating that flammable carbon monoxide and other gases are produced during the reduction process. After being fully transformed into molten iron, the slag is discharged. S, P, and C in the molten iron undergo desulfurization, dephosphorization, and decarburization reactions with oxygen in the air for 5 minutes to obtain crude steel products, as shown in Figure 4. The iron (steel) yield reaches 95.18%, and the carbon content is as low as 0.2%, which meets the carbon content requirements of low carbon steel. In addition, it was also measured that the S content was 0.028%, the P content was 0.030%, the Si content was 0.639%, and the Mn content was 0.345%.

The iron (steel) ingot obtained by cooling the crude steel product during the experiment of the present invention is shown in Figure 5. In the actual production process, the crude steel product obtained in the embodiment can be directly sent to the refining furnace for refining to obtain the final target steel product.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements, etc., made within the spirit and principles of the present invention, All should be included in the protection scope of the present invention.

Claims (10)

1. A method for step-by-step reduction of non-blast furnace steel production, characterized in that it includes the following steps: (1) Mix iron ore powder, reducing agent and solvent to form mixed raw materials; the reducing agent is a non-metallurgical coke type carbonaceous reducing agent; (2) The mixed raw materials are reduced for the first time in the dilute phase zone of the fluidized bed; during the first reduction process, the iron oxides in the iron ore powder are partially reduced by the reducing agent to obtain the first Sub-reduction solid products; (3) The solid product of the first reduction is reduced for the second time in the dense phase zone of the fluidized bed; the iron oxide in the solid product of the first reduction is further reduced by the reducing agent, Obtain an iron concentrate in which the oxygen element is further reduced, but the iron still mainly exists in the form of oxide; (4) The iron concentrate is sent to a melting furnace for smelting, and the melting furnace is heated. The remaining reducing agent during the heating process reduces the iron concentrate for the third time, so that the iron concentrate is The iron oxide is reduced to solid iron particles; the temperature continues to rise until the iron particles are turned into molten iron, and the scum in the upper layer of the melting furnace is discharged to obtain crude steel or crude iron products. 2. The method of claim 1, wherein the reducing agent in step (1) is biomass, coal, petroleum or natural gas; the solvent is calcium carbonate and/or fluorite. 3. The method of claim 1, wherein the mixed raw materials in step (1) are mixed powder; the size of the mixed powder is greater than or equal to 0.18mm, preferably 0.18-5mm. 4. The method of claim 1, wherein the first reduction process and the second reduction process are carried out in a fluidized bed, and the reduction temperature is 700-790°C; the fluidized bed includes an upper part The dilute phase zone and the lower dense phase zone, the fuel gas is introduced from the bottom of the dilute phase zone, so that the mixed raw material undergoes the first reduction in the dilute phase state of the fluidized bed, and the reduction of the first reduction The time is less than or equal to 2 minutes; the fuel gas is not introduced into the dense phase zone, and the solid product of the first reduction falls into the dense phase zone to perform the second reduction. The required heat is provided by the waste heat of the first reduction, and the reduction time of the second reduction is 1-30 minutes. 5. The method of claim 1, wherein the fluidized bed has an aspect ratio of 2-10. 6. The method of claim 1, wherein the melting furnace in step (4) is a gas-fired melting furnace or an electric melting furnace. 7. The method of claim 1, wherein the molar ratio of the C element in the reducing agent to the O element in the iron ore powder in step (1) is 1.05-1.15:1. 8. The method of claim 1, wherein step (4) continues to heat up until the iron particles are converted into molten iron, and at this time the carbon content reaches the carbon content range required for the target steel product, and the melting furnace is After the scum in the upper inner layer is discharged, the molten iron is contacted with air to undergo desulfurization, dephosphorization and decarburization reactions to obtain crude steel products. 9. The method of claim 8, further comprising the steps of: (5) Refining the crude steel product described in step (4) in a refining furnace or a refining ladle to obtain a target steel product, and using the target steel product directly as a casting raw material in a foundry; or use step (4) 4) The crude steel or crude iron products are directly used as casting raw materials in foundries. 10. A system for producing steel using the method according to any one of claims 1 to 9, characterized in that it includes a fluidized bed and a melting furnace, wherein, The fluidized bed includes an upper dilute phase section (1) and a lower dense phase section (2). The top of the fluidized bed is provided with a mixed raw material inlet (3) and a fluidized bed flue gas outlet (5). The upper section A fuel gas inlet (4) is provided between the dilute phase section (1) and the lower dense phase section (2); The iron concentrate outlet (6) provided at the bottom of the fluidized bed is connected with the iron concentrate inlet (7) of the melting furnace (8), and a melting furnace flue gas outlet (8) is provided at the top of the melting furnace (8). 9), the melting furnace flue gas outlet (9) is connected to the flue gas treatment system (10), and the flue gas treatment system (10) is connected to the fuel gas inlet (4); the melting furnace The upper side of the furnace (8) is also provided with a slag outlet (11), and the bottom is provided with a molten steel or molten iron outlet (12); When the system is used, the mixed raw materials enter the dilute phase section (1) of the fluidized bed from the mixed raw material inlet (3) provided at the top of the fluidized bed, and the fuel gas required for the fluidized bed reduction process flows from the mixed raw material inlet (3) provided at the top of the fluidized bed. The fuel gas inlet (4) between the upper dilute phase section (1) and the lower dense phase section (2) enters the fluidized bed, so that the mixed raw material becomes a dilute phase state in the dilute phase section (1) , the first reduction process is carried out in the dilute phase section; the solid state product of the first reduction falls into the dense phase section (2) after reduction, and the second reduction process is carried out in the dense phase section to obtain iron essence ore; the iron concentrate is transported from the iron concentrate outlet (6) at the bottom of the fluidized bed to the iron concentrate inlet (7) at the top of the melting furnace, and is heated in the melting furnace, and is completed in sequence In the third reduction, molten iron and slag removal operations of the iron concentrate, the crude steel or crude iron product obtained is discharged from the molten steel or molten iron outlet (12) at the bottom of the melting furnace; wherein the scum is discharged from the molten steel or molten iron outlet (12). The slag discharge port (11) provided on the melting furnace is discharged; the flue gas generated by reduction in the melting furnace (8) enters the flue gas treatment system (10) from the flue gas outlet (9) of the melting furnace. The flue gas treatment system (10) is transported to the fuel gas inlet (4) of the fluidized bed after impurity removal, cooling and compression, and is supplied to the fluidized bed as part of the fuel.