Hydrogen-based shaft furnace heating and shaft furnace internal thermal cycle process design scheme

Abstract

The invention discloses a hydrogen-based shaft furnace heating furnace device and a hydrogen internal thermal cycle process method, and belongs to the technical field of hydrogen metallurgy of a hydrogen-based shaft furnace for directly reducing iron oxide. The method comprises the following steps: (1) the hydrogen-based shaft furnace adopts double heating channels, so that a relatively large high-temperature constant-temperature area in the shaft furnace can be ensured, and the reduction efficiency of oxidized pellets in the hydrogen-based shaft furnace is effectively improved; and (2) the preheating section is arranged above the reduction section of the hydrogen-based shaft furnace, and gas exhausted from the cooling section is introduced into the preheating section, so that the energy waste is reduced, and the pellet reduction efficiency of the reduction section is improved. And (3) the heating furnace of the hydrogen-based shaft furnace adopts stone ball electric heating, so that the heat exchange area and the safety of hydrogen heating are improved, the energy loss in the hydrogen production link is avoided, and meanwhile, the energy utilization rate is improved by hot hydrogen introduced from the heating and cooling section. And (4) due to the three-section type heating furnace structure of the hydrogen-based shaft furnace, the heat conduction effect in the furnace is poor due to the scale deposition phenomenon in the heater, the three-section type heating furnace structure is adopted, internal stone balls can be conveniently and regularly replaced, and therefore the heating efficiency is improved. The double heating channels of the shaft furnace are additionally arranged, and gas exhausted by the cooling section is introduced into the preheating section, so that the hydrogen-based shaft furnace is compact in design structure, and energy waste is reduced. And meanwhile, the heating furnace adopts a three-section electric heating structure, so that the heating safety of hydrogen is improved, and workers can conveniently and regularly clean scale deposited on the heating furnace.

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 particularly relates to a hydrogen-based vertical furnace heating furnace device and a hydrogen internal heat circulation process method. 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. As a high-energy-consuming and high-emission industry, the steel industry's carbon emissions 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 from the entire steel production process. In the context of the "dual carbon" era, energy efficiency has become an important factor in measuring a country's competitiveness. Compared with the traditional "blast furnace + converter" smelting process, the direct reduction iron + electric furnace short process has obvious advantages in carbon emission reduction. 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.

[0004] Hydrogen metallurgy, which replaces carbon with hydrogen, is becoming a strategic technology option for the green and low-carbon development of the domestic and international steel industry. 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, hydrogen metallurgy technology uses hydrogen as a reducing agent instead of carbon reduction, which is a good way to reduce CO in long-process steelmaking. 2 Emissions are one of the important ways to ensure the green and sustainable development of the steel industry. Summary of the invention

[0005] The purpose of the present invention is to provide a design scheme suitable for hydrogen circulation process and equipment of hydrogen-based vertical furnace, so as to improve the reduction efficiency and heating efficiency of hydrogen-based vertical furnace by improving the traditional process.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] 1. The hydrogen-based vertical furnace adopts double heating channels, which can ensure that there is a large high-temperature constant temperature area inside the vertical furnace, effectively improving the reduction efficiency of oxidized pellets inside the hydrogen-based vertical furnace.

[0008] 2. A preheating section is set above the reduction section of the hydrogen-based vertical furnace, and the gas discharged from the cooling section is passed into the preheating section to reduce energy waste and improve the reduction efficiency of pellet ore in the reduction section.

[0009] 3. The hydrogen-based vertical furnace heating furnace adopts electric heating of heat storage body, which improves the heat exchange area and the safety of hydrogen heating, avoids energy loss in the hydrogen production link, and at the same time, the hot hydrogen passed through the heating and cooling section improves energy utilization.

[0010] 4. The three-stage structure of the hydrogen-based vertical furnace heating furnace. Due to the fouling inside the heater, the heat conduction effect in the furnace is poor. The three-stage heating furnace structure is adopted to facilitate the regular replacement of the internal heat storage body, thereby improving the heating efficiency.

[0011] Compared with the prior art, the present invention has the following technical effects: by adding a double heating channel of the vertical furnace and introducing the gas discharged from the cooling section into the preheating section, the hydrogen-based vertical furnace design structure is made compact and energy waste is reduced. At the same time, the heating furnace adopts a three-stage electric heating structure of a heat storage body, which improves the heating safety of hydrogen and facilitates personnel to regularly clean the scale of the heating furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Process flow chart for producing sponge for hydrogen-based shaft furnace

[0013] Figure 2 The main structure diagram of the hydrogen-based vertical furnace

[0014] Figure 3 Gas cycle flow chart for hydrogen-based shaft furnace

[0015] Figure 4 The structure diagram of hydrogen-based vertical furnace heating furnace DETAILED DESCRIPTION

[0016] 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.

[0017] The purpose of the present invention is to improve the energy utilization rate of the hydrogen-based vertical furnace reduction process by designing the main structure of the hydrogen-based vertical furnace, and at the same time adopt an electrically heated three-stage heating furnace to facilitate personnel to clean the equipment scale.

[0018] The process flow of hydrogen-based vertical furnace reduction of iron oxide is as follows Figure 1 As shown, it includes a loading system (elevator, raw material bin, etc.), a vertical furnace body (reaction bin, dust removal and dehumidification system, compressor, heating system, etc.), and a unloading system (screw unloading, unloading bin, etc.), and can produce products such as HDRI and CDRI.

[0019] The interior of the vertical furnace is divided into preheating section, reduction section, transition section and cooling section. Figure 2 shown.

[0020] The iron ore enters the shaft furnace through the upper inlet, and first enters the preheating section during the downward movement of the shaft furnace. The hot hydrogen (400°C) after heat exchange at the cooling section outlet enters the lower part of the preheating section through the channel 6. The preheating gas exchanges heat with the iron ore in the preheating section to increase its temperature. The hydrogen (≤200°C) after heat exchange enters the dust removal and dehumidification system through the exhaust gas channel 5, and the exhaust gas is recycled and reused.

[0021] The iron ore moves downward from the preheating section into the reduction section, where it undergoes a thermal reduction reaction with high-temperature hydrogen to generate sponge iron. The chemical reaction formula for this reduction reaction is:

[0022]

[0023] This reduction reaction process is an endothermic reaction. It is impossible to maintain an excessively high reaction temperature in the furnace. High-temperature hydrogen needs to be continuously introduced to maintain the internal temperature balance so that the reduction reaction can proceed continuously and efficiently. High-temperature hydrogen (1000°C) is introduced through channels 3 and 4 to form a self-sealed high-temperature area, and the area of ​​the high-temperature reaction area becomes larger. A large area of ​​constant high-temperature area can improve the metal reduction rate and reaction efficiency of the vertical furnace.

[0024] The sponge iron moves downward from the reduction section into the transition section. The main function of the transition section is to prevent the hot reduction hydrogen from communicating with the cooling hydrogen. However, this process cannot be completely avoided, so part of the heat will be taken away by the hydrogen at the outlet of the cooling section and then flow back to the interior of the vertical furnace through channel 2, which can effectively reduce the waste of heat.

[0025] The sponge iron moves downward from the transition section into the cooling section, and room temperature hydrogen (25°C) is introduced through channel 1 to the bottom of the cooling section to exchange heat with the descending sponge iron, so that the hot sponge iron is cooled to 80°C and then discharged from the discharge port to the outside of the vertical furnace. The hot hydrogen (≤400°C) after heat exchange is discharged from the cooling section through channel 2 to preheat the room temperature iron ore. Generally, the waste hydrogen after heat exchange is directly introduced into the dust removal and dehumidification system to recycle and reuse the waste gas, but the waste hot hydrogen (≤400°C) needs to be cooled and dehydrated after entering the dust removal and dehumidification system, and the heat of the hot hydrogen is wasted.

[0026] The present invention can divide the hot waste hydrogen discharged through the cooling section channel 2 into three circulation methods, such as Figure 3 The gas circulation flow chart shown in the figure, the specific circulation method is as follows:

[0027] Method 1: The hot waste hydrogen is introduced into the lower part of the preheating section through channel 6 to complete the preheating of the sponge iron in the preheating section, which helps to quickly carry out the high-temperature reduction of the pellets in the reduction section. Figure 2 shown.

[0028] Method 2: Hot waste hydrogen is introduced into the heating furnace 1 through the channel 7. Since the pellets in the cooling section have been reduced to sponge iron, the dust carried is relatively low. After the hot waste hydrogen is introduced into the heating furnace 1 and heated to 1000°C, it is introduced into the preheating section to complete the preheating of the sponge iron, which helps to quickly carry out the high-temperature reduction of the pellets in the reduction section.

[0029] Method 3: Part of the hot waste hydrogen is introduced into the bottom of the preheating section through channel 6, and the other part is introduced into the heating furnace 1 through channel 7 and heated to 1000°C to enter the reduction section to reduce iron oxide. By adjusting the flux of channels 6 and 7, the amount of gas used in the reduction process can be effectively adjusted to achieve thermal balance in the furnace.

[0030] The heating system includes two heaters, namely electric heating furnace 1 and electric heating furnace 2. Figure 2 As shown, the electric heating furnace 1 is the main heating furnace, and a large amount of high-temperature (1000°C) hydrogen is introduced into the reduction section of the vertical furnace through the channel 3. The electric heating furnace 2 is the auxiliary heating furnace, and a small amount of high-temperature hydrogen (1000°C) is introduced into the reduction section of the vertical furnace through the channel 4, thereby forming a constant temperature and high temperature area to ensure that the reduction reaction inside the vertical furnace can be carried out efficiently and stably.

[0031] The difficulties in heating furnace design are as follows:

[0032] 1. The recycled hydrogen will carry a certain amount of dust. The amount of recycled hydrogen is 2.5 times the amount of newly charged hydrogen. Therefore, during the heating process, scaling will occur inside the heating furnace, and a large amount of dust will reduce the heating efficiency inside the heating furnace.

[0033] 2. Hydrogen heating absorbs less heat than carbon monoxide. The energy required to heat each mole of hydrogen from 25°C to 1000°C is 29226J, while carbon monoxide requires 30830J, so the heating furnace needs to heat more hydrogen.

[0034] 3. Under high temperature conditions, the internal substances of refractory materials will undergo a series of reactions with hydrogen, causing corrosion of the refractory materials. Therefore, the corrosion resistance of materials in contact with high temperature and high pressure hydrogen is required to be extremely high.

[0035] The electric heating furnace adopts a three-stage electric heating form, the structure is as follows Figure 4 shown.

[0036] Hydrogen enters the heating furnace from one side, passes through the heating box, and the high-temperature hydrogen is discharged from the other side of the electric heating furnace. It enters the reduction section of the hydrogen-based vertical furnace through a channel filled with refractory materials to react with iron oxide to generate sponge iron. The hydrogen channel in the furnace is equipped with a thermocouple to feedback control the power of the electric heater to adjust the temperature of the hot hydrogen entering the reduction section.

[0037] The heating furnace adopts a cylindrical structure design, and the two sides are connected by flange surfaces, which is convenient for personnel to disassemble and clean the internal dust. The interior is filled with low-iron mullite castable, and a heating heat storage body and hydrogen heating channel are reserved. The pressure in the furnace must be kept consistent with the pressure of the reduction section of the vertical furnace to ensure that the hot hydrogen can enter the reduction section through the pipeline to react with the pelletized ore.

[0038] The heating regenerator is placed in the hydrogen heating channel, and the heat exchange area with the hydrogen is increased through the regenerator, thereby improving the heat exchange efficiency with the hydrogen, thereby improving the heating efficiency of the hydrogen. A heating rod is provided in the middle of the regenerator to heat the regenerator.

[0039] The hydrogen passing through the channel 7 into the heating furnace 1 will carry a small amount of dust, which will adhere to the heat storage body after entering the heating furnace and even block the hydrogen heating channel. The heat storage body can play a certain filtering role on the hydrogen passing through the channel 7. At the same time, the heating furnace adopts a three-stage structure to facilitate the disassembly and removal of the heat storage body for replacement.

[0040] The heating rod is heated by silicon carbon rod. The temperature after hydrogen heating is 1000℃. The use temperature of silicon carbon rod is between 1000 and 1400℃, which fully meets the heating requirements. The various connection methods of silicon carbon rod make installation more convenient. Considering the economy, silicon carbon rod heating is adopted. The cold end of silicon carbon rod is equipped with water cooling jacket to cool the silicon carbon rod, which can effectively increase the service life of silicon carbon rod.

[0041] The use of electric heating can improve the heating safety of hydrogen and improve the overall energy utilization rate of the system. As a carbon-free heating furnace, if hydrogen is ignited to heat hydrogen, the preparation of hydrogen mainly adopts the method of electrolysis of water. In this way, there is energy loss in the process of electrolysis of water. Direct use of electric heating can shorten the overall heating process and improve utilization rate.

Claims

1. The purpose of the present invention is to provide a design scheme suitable for hydrogen circulation process and equipment of hydrogen-based vertical furnace, and to improve the reduction efficiency and heating efficiency of hydrogen-based vertical furnace by improving the traditional process. To achieve the above purpose, the present invention provides the following technical solutions: 1) The hydrogen-based vertical furnace adopts double heating channels, which can ensure that there is a large high-temperature constant temperature area inside the vertical furnace, effectively improving the reduction efficiency of oxidized pellets inside the hydrogen-based vertical furnace; 2) A preheating section is set above the reduction section of the hydrogen-based vertical furnace, and the gas discharged from the cooling section is passed into the preheating section to reduce energy waste and improve the reduction efficiency of pellet ore in the reduction section; 3) The hydrogen-based vertical furnace heating furnace adopts heat storage body electric heating, which increases the heat exchange area and the safety of hydrogen heating, avoids energy loss in the hydrogen production link, and at the same time heats the hot hydrogen passing through the cooling section to improve energy utilization; 4) The three-stage structure of the hydrogen-based vertical furnace heating furnace. Due to the fouling inside the heater, the heat conduction effect in the furnace is poor. The three-stage heating furnace structure is adopted to facilitate the regular replacement of the internal heat storage body, thereby improving the heating efficiency.

2. A design scheme for hydrogen circulation process and equipment for hydrogen-based vertical furnace according to claim 1, characterized in that: Three hydrogen circulation methods are used to improve heat utilization, including: Method 1: The hot waste hydrogen is introduced into the lower part of the preheating section through the channel 6 to complete the preheating of the sponge iron in the preheating section, which helps to quickly carry out the high-temperature reduction of the pellets in the reduction section; Method 2: The hot waste hydrogen is introduced into the heating furnace 1 through the channel 7. Since the pellets in the cooling section have been reduced to sponge iron, the dust carried is relatively low. After the hot waste hydrogen is introduced into the heating furnace 1 and heated to 1000°C, it is introduced into the preheating section to complete the preheating of the sponge iron, which is conducive to the rapid high-temperature reduction of the pellets in the reduction section. Method 3: Part of the hot waste hydrogen is introduced into the bottom of the preheating section through channel 6, and the other part is introduced into the heating furnace 1 through channel 7 and heated to 1000°C to enter the reduction section to reduce iron oxide. By adjusting the flux of channels 6 and 7, the amount of gas used in the reduction process can be effectively adjusted to achieve thermal balance in the furnace.

3. According to claim 1, a design scheme for hydrogen circulation process and equipment for hydrogen-based vertical furnace, characterized in that: The heating system includes two heaters, namely electric heating furnace 1 and electric heating furnace 2. Electric heating furnace 1 is the main heating furnace, and a large amount of high-temperature (1000°C) hydrogen is introduced into the reduction section of the vertical furnace through channel 3. Electric heating furnace 2 is the auxiliary heating furnace, and a small amount of high-temperature hydrogen (1000°C) is introduced into the reduction section of the vertical furnace through channel 4, thereby forming a constant temperature and high temperature area to ensure that the reduction reaction inside the vertical furnace can be carried out efficiently and stably. Hydrogen enters the heating furnace from one side, passes through the heating box, and the high-temperature hydrogen obtained is discharged from the electric heating furnace from the other side. It enters the reduction section of the hydrogen-based vertical furnace through the insulated pipe filled with refractory materials to react with iron oxide to generate sponge iron. The insulated pipe is equipped with a thermocouple to feedback control the power of the electric heater to adjust the temperature of the hot hydrogen entering the reduction section. The heating furnace adopts a cylindrical structure design, and the two sides are connected by flange surfaces, which is convenient for personnel to disassemble and clean the internal dust. The interior is filled with low-iron mullite castable, and a heating heat storage body and hydrogen heating channel are reserved. The pressure in the furnace must be kept consistent with the pressure of the reduction section of the vertical furnace to ensure that the hot hydrogen can enter the reduction section through the pipeline to react with the pelletized ore. The heating regenerator is placed in the hydrogen heating channel, and the heat exchange area with the hydrogen is increased through the regenerator, thereby improving the heat exchange efficiency with the hydrogen, thereby improving the heating efficiency of the hydrogen. A heating rod is provided in the middle of the regenerator to heat the regenerator. The hydrogen passing through the channel 7 into the heating furnace 1 will carry a small amount of dust, which will adhere to the heat storage body after entering the heating furnace and even block the hydrogen heating channel. The heat storage body can play a certain filtering role on the hydrogen passing through the channel 7. At the same time, the heating furnace adopts a three-stage structure to facilitate the disassembly and removal of the heat storage body for replacement. The heating rod is heated by a silicon carbon rod. The temperature after hydrogen heating is 1000℃. The cold end of the silicon carbon rod is equipped with a water cooling jacket to cool the silicon carbon rod, which can effectively increase the service life of the silicon carbon rod. The use of electric heating can improve the heating safety of hydrogen. The present invention improves the energy utilization rate of the circulating gas of the hydrogen-based vertical furnace through the above-mentioned equipment design. The heating furnace adopts a three-stage electric heating structure of a heat storage body, which improves the heating safety of hydrogen and facilitates personnel to regularly clean the scale of the heating furnace.

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