Structural design scheme of induction self-heating hydrogen-based shaft furnace

Abstract

According to the structural design scheme of the induction self-heating hydrogen-based shaft furnace, the problem that heat compensation in the furnace is difficult through external heating of high-temperature hydrogen is particularly solved, the induction self-heating structural design is adopted in the hydrogen-based shaft furnace, a transition section in a traditional shaft furnace is omitted, and the overall height of the shaft furnace is reduced by reducing a cooling section; the overall lifting height of the materials in the whole process is reduced, and the production period is shortened. The hydrogen-based shaft furnace adopts a single-channel hydrogen inlet, a cooling section waste gas outlet and a reduction section hot air inlet are omitted, hydrogen exchanges heat with reduced high-temperature sponge iron in a cooling section for preheating, and meanwhile the temperature of the sponge iron is reduced to the discharging temperature after heat exchange. Materials are subjected to a reduction reaction in a heat accumulator channel in the shaft furnace to generate sponge iron, heat is directly compensated through electromagnetic induction in the shaft furnace, the hydrogen introduction amount is reduced, the equipment treatment amount of a furnace top waste gas circulation system is reduced, a cooling section waste gas circulation system is omitted, and the aim of reducing the production energy consumption of the sponge iron is achieved through the structural design scheme.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen metallurgy of a hydrogen-based vertical furnace for direct reduction of iron oxide, and in particular relates to a design scheme of a magnetic induction self-heating hydrogen-based vertical furnace. Background Art

[0002] In 2023, my country's crude steel output reached 1.019 billion tons, accounting for 54% of the world's crude steel output. The steel industry is one of the high-energy-consuming and high-emission industries. Carbon emissions from the steel industry account for about 15% of the country's total carbon emissions, making it the industry with the largest carbon emissions among the 31 categories of manufacturing.

[0003] my country's steel industry has long been dominated by the blast furnace-converter long process, and its carbon emission intensity remains high. Iron produced by blast furnace ironmaking still accounts for more than 95% of my country's total iron production. Blast furnace ironmaking is the process with the largest carbon dioxide emissions, accounting for about 70% to 90% of the total carbon dioxide emissions of the entire steel production process. In the context of the "dual carbon" era, compared with the traditional "blast furnace + converter" smelting process, the carbon emission reduction advantage of the direct reduction iron + electric furnace short process is significant. The hydrogen metallurgical process uses hydrogen instead of coke as a reducing agent, which significantly reduces the production of carbon dioxide and helps to achieve low-carbon and green steel production in my country.

[0004] Hydrogen metallurgy, which uses hydrogen instead of carbon, is becoming a strategic technology option for the green and low-carbon development of the steel industry at home and abroad. Hydrogen-based vertical furnaces use hydrogen to reduce iron oxide, and its main products are metallic iron and water vapor, without other carbon-containing reducing gases such as CO, so low-carbon and green steel production can be achieved. With the accelerated popularization and utilization of green electricity such as photovoltaics and wind power and the rapid decline in the cost of water electrolysis hydrogen production technology, the advantages of hydrogen metallurgy technology using hydrogen as a reducing agent instead of carbon reduction are gradually emerging. It is an essential option for reducing CO2 emissions from ironmaking and one of the important ways to ensure the green and sustainable development of the steel industry.

[0005] The reaction of hydrogen reduction of pelletized ore inside a hydrogen-based vertical furnace is an endothermic reaction. In order to maintain the high-temperature reduction conditions inside the vertical furnace, a large amount of heat supplement is required inside the vertical furnace. At present, an external heating furnace is generally used to heat the hydrogen, and the heating hydrogen temperature needs to reach 950-1050°C, which puts higher requirements on the high temperature resistance and hydrogen corrosion resistance of the heating furnace shell material. Nickel-based alloys are usually used for the heat exchange tubes inside the heating furnace. Due to the high price of nickel-based alloys, the manufacturing cost of hydrogen-based vertical furnace heating furnaces is relatively high.

[0006] Induction heating uses electromagnetic induction to generate eddy currents on the surface of the heated part, and relies on the eddy currents to achieve the purpose of heating. As an efficient and environmentally friendly heating method, induction heating technology has shown great potential in energy conservation and pollution reduction, and has become one of the important technologies for all walks of life to pursue sustainable development. Electromagnetic induction is used to heat the interior of the vertical furnace to meet the heat demand for reducing iron ore inside the vertical furnace, so that the reduction process in the furnace can be carried out efficiently and stably. Summary of the invention

[0007] The purpose of the present invention is to provide an induction self-heating hydrogen-based vertical furnace structure design scheme, especially for solving the problem that it is difficult to supplement heat in the furnace by external heating of high-temperature hydrogen. The hydrogen-based vertical furnace adopts an induction self-heating structure design, eliminates the transition section in the traditional vertical furnace, and reduces the height of the cooling section to reduce the overall height of the vertical furnace, so that the overall lifting height of the material in the whole process is reduced, shortening the production cycle. The hydrogen-based vertical furnace adopts a single-channel hydrogen inlet, eliminates the exhaust gas outlet of the cooling section and the hot air inlet of the reduction section. The hydrogen is preheated by heat exchange with the reduced high-temperature sponge iron DRI in the cooling section, and the temperature of the sponge iron is reduced to the furnace discharge temperature after heat exchange. The material undergoes a reduction reaction in the heat storage channel inside the vertical furnace to generate sponge iron. The heat is directly compensated by electromagnetic induction inside the vertical furnace, reducing the amount of hydrogen introduced, reducing the processing capacity of the exhaust gas circulation system equipment on the top of the furnace, and eliminating the exhaust gas circulation system in the cooling section, so as to reduce the energy consumption of sponge iron production.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] 1. Electromagnetic induction is used to directly heat the interior of the vertical furnace. Compared with traditional gas chemical energy heating, it can reduce heat loss and improve the comprehensive energy utilization rate. At the same time, there is no CO2 emission, which prevents greenhouse gas emissions from aggravating the greenhouse effect.

[0010] 2. A heat storage body is placed inside the hydrogen-based vertical furnace, which is heated by electromagnetic induction. The convective hydrogen and materials are directly heated by the heat storage body, which improves the heat exchange efficiency compared with the external gas heating furnace.

[0011] 3. The hydrogen inlet of the reduction section of the hydrogen-based vertical furnace is cancelled, and the transition section of the vertical furnace body is cancelled to reduce the overall height of the furnace body, shortening the entire material flow process. At the same time, the exhaust gas circulation system of the cooling section is cancelled, reducing the overall energy consumption of sponge iron production.

[0012] 4. The cooling section of the hydrogen-based vertical furnace is equipped with a single hydrogen inlet. Hydrogen is introduced into the cooling section to exchange heat with the reduced hot sponge iron for preheating. At the same time, the temperature of the sponge iron is reduced to the furnace outlet temperature after heat exchange. The heat is directly compensated by electromagnetic induction inside the vertical furnace, which can reduce the amount of hydrogen introduced, reduce the processing capacity of the circulation system equipment, and reduce the energy consumption of sponge iron production.

[0013] Compared with the prior art, the present invention has the following technical effects: the heat exchange efficiency is improved by heating the vertical furnace with electromagnetic induction, the overall height of the vertical furnace is reduced by eliminating the vertical furnace body transition section, the reduction section hydrogen inlet, and the cooling section waste gas outlet, the cooling section waste gas circulation system is eliminated, and the processing capacity of the furnace top gas circulation purification system is reduced, thereby reducing the energy consumption per ton of sponge iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Structural design of induction self-heating hydrogen-based vertical furnace

[0015] In the figure, 1-feed port; 2-furnace top gas outlet; 3-distribution plate; 4-heat storage body; 5-inductance coil; 6-refractory material; 7-cold hydrogen inlet; 8-internal hydrogen channel; 9-hydrogen nozzle; 10-discharge port. DETAILED DESCRIPTION

[0016] Aiming at the problem of difficult heat compensation inside a vertical furnace, the present invention carries out a full-process design from aspects such as heating method, furnace structure, gas circulation, etc., and provides a novel hydrogen-based vertical furnace structure.

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] like Figure 1 As shown, the material enters the vertical furnace from the feed port 1, exchanges heat with the exhaust gas at the top of the furnace, so that the material temperature reaches 100-200°C, and enters the material channel in the heat storage body 4 through the distribution plate 3. Heat exchange is achieved in the material channel and the heat storage body, and the material temperature can reach 800-950°C. The material reacts with hydrogen in the reduction section to generate sponge iron. The chemical reaction equation of this reduction reaction is:

[0019]

[0020] This process is an endothermic reaction, and a large amount of heat needs to be compensated in the vertical furnace to ensure high-temperature reaction conditions, so that the reduction reaction can proceed continuously and efficiently and meet the requirement that the metallization rate of the sponge iron product is ≥ 90%.

[0021] After the material is reduced, sponge iron is generated. The sponge iron falls into the cooling section from the material channel of the heat storage body, and exchanges heat with the hydrogen introduced from the cold hydrogen inlet 7 of the cooling section, so that the temperature of the high-temperature sponge iron is reduced to ≤80°C, and then discharged from the vertical furnace from the vertical furnace discharge port 10.

[0022] Cold hydrogen is introduced from the cold hydrogen inlet 7 of the cooling section, and is blown into the hydrogen nozzle 9 through the hydrogen channel 8 inside the vertical furnace and the gas annular channel in the refractory material 6. The hydrogen nozzle is designed to be a ring-shaped uniformly arranged structure, and the nozzle is blown obliquely at an angle of 45° to the central axis to prevent sponge iron from entering the hydrogen channel through the hydrogen nozzle and blocking the normal flow of hydrogen.

[0023] Hydrogen enters the vertical furnace from the hydrogen nozzle 9 and exchanges heat with the high-temperature sponge iron in the cooling section to realize the preheating process of hydrogen. The preheating process can heat the cold hydrogen to 300-500°C, and then enters the reduction section of the hydrogen-based vertical furnace. Here, the hydrogen exchanges heat with the heat storage body 4 and the hot material. This process can realize a high-temperature hydrogen reduction process of 800-950°C. The reduced exhaust gas enters the preheating section through the distribution plate 3 and exchanges heat with the newly input material. The exhaust gas temperature drops below 400°C and is discharged from the vertical furnace body through the furnace top gas outlet 2, and enters the furnace top gas circulation system for purification.

[0024] The furnace top gas circulation system includes cyclone dust removal, water washing tower, gas-water separator, filter, press, heat exchanger, and gas-water separator before entering the furnace. This design eliminates the hydrogen heating furnace heating link and directly allows cold hydrogen to enter the furnace.

[0025] Hydrogen has a low specific heat capacity and absorbs less heat during the heating process. It is also more difficult to heat than other reducing gases. Hydrogen heating furnaces generally use combustion or electric heating. In order to compensate for the reaction heat consumption in the hydrogen-based vertical furnace, the hydrogen needs to be heated to 1050°C, which places extremely high demands on the stability of the structure and materials of the heating furnace, resulting in high overall manufacturing costs for hydrogen heating furnaces. Currently, there are few heating furnace manufacturers on the market that can achieve stable output of 1050°C high-temperature hydrogen, resulting in a high price for hydrogen heating furnaces, which increases the price share of heating furnaces in the entire vertical furnace process equipment.

[0026] The distribution plate 3 is located directly above the heat storage body, the center of the funnel is consistent with the center of the heat storage body channel, the funnel outlet is smaller than the channel diameter, and a triangular structure is adopted above the distribution plate to prevent the material from aggregating on the distribution plate, so that the material can smoothly enter the heat storage body channel. On the other hand, the cross-sectional area of ​​the funnel is much smaller than the direct diameter of the vertical furnace, so that the newly entered material and the high-temperature exhaust gas after reduction can fully undergo gas-solid heat exchange, thereby improving the heat exchange coefficient of the preheating section and further reducing the exhaust gas temperature at the furnace top gas outlet.

[0027] The electromagnetic induction furnace is used for heating. The induction coil 5 is placed in the reduction section of the refractory material 6. Cooling water is introduced to cool the magnetic induction coil. The induction coil 5 generates eddy currents in the heat storage body through the changing alternating magnetic field, and heats the heat storage body to 900-1000°C. The refractory material adopts a three-layer castable structure (mullite, light weight, fiber felt), which has wear resistance, high temperature resistance and good thermal insulation performance. The thermal insulation function of the refractory material makes the temperature of the furnace shell ≤100°C.

[0028] The heat storage body adopts a honeycomb structure to increase the heat exchange area of ​​the heat storage body. The bottom of the heat storage body is connected to the furnace body for fixation and insulated by refractory masonry. The outer side of the top of the heat storage body is in contact with the refractory material and fixed. The heat storage body acts as a heat source to transfer heat to the convective materials and hydrogen, realizing the high-temperature reduction process in the furnace.

[0029] Traditional vertical furnaces use independent hydrogen heating furnaces to supplement heat in the furnace. Hot hydrogen is introduced into the hydrogen-based vertical furnace. The hydrogen consumption for reduction reaction is only 20% to 30% of the introduced amount. Most of the hydrogen is cooled to a low temperature through the furnace top gas circulation system and then continues to flow back to the heating furnace for heating. The heat of the furnace top gas is consumed through the circulation system, resulting in a waste of heat energy in the gas circulation system.

[0030] This design adopts the hydrogen-based vertical furnace electromagnetic induction furnace heating method, which can improve the utilization rate of the hydrogen introduced, reduce the amount of waste gas introduced into the furnace top gas circulation system, and reduce the waste gas treatment volume of the furnace top gas circulation system.

[0031] The traditional vertical furnace structure generally consists of a preheating section, a reduction section, a transition section, and a cooling section. The function of the transition section is to highly isolate the hot hydrogen from the cooling hydrogen, thereby affecting the metallization rate of the sponge iron.

[0032] This design adopts a single hydrogen inlet structure, and there is no need to isolate hot hydrogen from cold hydrogen. Therefore, the transition section of the vertical furnace body can be eliminated, and the height of the cooling section can be reduced to reduce the overall height of the vertical furnace.

[0033] For the traditional vertical furnace structure, there is a separate gas purification device in the cooling section. Cold hydrogen is introduced into the cooling section to cool down the high-temperature sponge iron generated after reduction. The outlet temperature of the sponge iron is ≤50°C. After the cold hydrogen passes through the heat exchange in the cooling section, the gas temperature at the gas outlet of the cooling section is ≥300°C. It returns to the system again through the gas purification device, which will cause energy waste.

[0034] This design adopts a structure in which hydrogen is introduced into the cooling section of the hydrogen-based vertical furnace through a single channel. After the cold hydrogen is introduced, it directly enters the cooling section to complete the heat exchange with the sponge iron. There is no need to purify the heat exchange gas. At the same time, the preheating process of the hydrogen is completed, so that the hydrogen enters the reduction section more easily to react with the material for reduction. This process is carried out inside the vertical furnace, reducing energy loss and thus reducing the production cost per ton of sponge iron. The advantages of the induction self-heating hydrogen-based vertical furnace structure design are:

[0035] 1. The use of electromagnetic induction to heat the interior of the vertical furnace can shorten the hydrogen heating process, improve the overall energy utilization rate of the hydrogen-based vertical furnace, directly heat the hydrogen and materials through the heat storage body, improve the heating efficiency, and there is no expensive heating furnace device, so the equipment cost is effectively controlled;

[0036] 2. Electromagnetic induction is used to directly heat the interior of the vertical furnace, and hydrogen and materials are heated through the heat storage body, which can reduce the amount of hydrogen introduced into the vertical furnace, reduce the amount of exhaust gas on the top of the furnace, and reduce the amount of exhaust gas treated by the purification system, thereby reducing the energy loss of the overall process and the production and operation costs of the equipment.

[0037] 3. Electromagnetic induction is used to heat the interior of the vertical furnace, the internal transition section of the vertical furnace is eliminated, and the height of the cooling section is reduced. The structure of introducing hydrogen through a single channel is adopted, making the vertical furnace structure more compact, the overall height of the vertical furnace is effectively reduced, and the energy consumption of material transportation is reduced. The cooling section purification system is eliminated, which reduces the manufacturing cost and energy consumption of the equipment, thereby reducing the production cost per ton of sponge iron.

Claims

1. A structural design scheme suitable for hydrogen-based vertical furnace induction self-heating hydrogen, used to solve the problem of difficulty in supplementing heat in the furnace by external heating of high-temperature hydrogen, characterized by: 1) Electromagnetic induction heating is used to directly heat the interior of the vertical furnace. Compared with traditional gas chemical energy heating, it can reduce heat loss and comprehensive energy utilization. At the same time, there is no CO2 emission, preventing greenhouse gas emissions from aggravating the greenhouse effect. 2) A magnetic heat storage body is placed inside the hydrogen-based vertical furnace, which is heated by electromagnetic induction. The reducing gas hydrogen and materials are directly heated by the heat storage body, which improves the heat exchange efficiency compared with an external gas heating furnace. 3) The hydrogen inlet of the reduction section of the hydrogen-based vertical furnace is eliminated, and the transition section of the vertical furnace body is eliminated to reduce the overall height of the furnace body, shortening the entire material flow process. At the same time, the exhaust gas circulation system of the cooling section is eliminated, reducing the overall energy consumption of sponge iron production. 4) The cooling section of the hydrogen-based vertical furnace is equipped with a single hydrogen inlet. Hydrogen is introduced into the cooling section to exchange heat with the reduced hot sponge iron for preheating. At the same time, the temperature of the sponge iron is reduced to the furnace outlet temperature after heat exchange. The heat is directly compensated by electromagnetic induction inside the vertical furnace, which can reduce the amount of hydrogen introduced, reduce the processing capacity of the circulation system equipment, and reduce the energy consumption of sponge iron production.

2. According to the structural design drawing of a hydrogen-based vertical furnace induction self-heating hydrogen-based vertical furnace according to claim 1, it is characterized in that: As shown in FIG1 , the material enters the vertical furnace from the feed port 1 , exchanges heat with the exhaust gas at the furnace top, enters the material channel in the heat storage body 4 through the distribution plate 3 , and exchanges heat with the heat storage body in the material channel. The electromagnetic induction furnace is used for heating, and the induction coils 5 are placed inside the reduction section of the refractory material 6. Cooling water is introduced to cool the magnetic induction coils. The induction coils 5 generate eddy currents in the heat storage body through the changing alternating magnetic field. Cold hydrogen is introduced from the cold hydrogen inlet 7 of the cooling section, and is blown into the hydrogen nozzle 9 through the hydrogen channel 8 inside the vertical furnace and the gas annular channel in the refractory material 6. The hydrogen nozzle is designed to be a ring-shaped uniformly arranged structure, and the nozzle is blown obliquely at an angle of 45° to the central axis to prevent sponge iron from entering the hydrogen channel through the hydrogen nozzle and blocking the normal flow of hydrogen.

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