Split type pure hydrogen high-temperature electric heating device of hydrogen-based shaft furnace

Abstract

The invention relates to a design scheme suitable for hydrogen electric heating equipment of a hydrogen-based shaft furnace, belongs to the technical field of hydrogen metallurgy for directly reducing the hydrogen-based shaft furnace, and aims to solve the problems that the aging of a heating rod is influenced and the service life of a heating furnace is influenced due to reduction reaction between hydrogen and the heating rod at high temperature. The pure hydrogen high-temperature electric heating adopts a split type structural design, and a heating rod distribution cavity and a hydrogen heating cavity are isolated from each other, so that the surface of a silicon-molybdenum heating rod is prevented from being subjected to a reduction reaction with high-temperature hydrogen and water vapor; the heating rod distribution cavity is filled with nitrogen, the pressure of the heating rod distribution cavity is larger than that of the hydrogen heating cavity, hydrogen leakage of the hydrogen heating cavity is prevented, and the safety of the whole heating furnace is improved. The heating furnace adopts a three-section structural design, maintenance personnel can conveniently maintain the internal structure of the heating furnace and replace parts, and the service life and the safety performance of the pure hydrogen heating furnace are improved through the design mode of 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 pure hydrogen electric heating device for a hydrogen-based vertical furnace. Background Art

[0003] The steel industry has long been dominated by the blast furnace-converter long process, and its carbon emission intensity remains high. 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 direct reduction iron + electric furnace short process has significant 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 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 reducing pellets inside the 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. The heat supplement is circulated by heating the hydrogen to a higher temperature. At this time, the heated hydrogen temperature needs to reach 950-1050°C. The shell material of the heating furnace needs to have long-term high temperature resistance and hydrogen corrosion resistance. Hydrogen is flammable and explosive. The temperature and pressure need to be strictly controlled during the heating process to prevent hydrogen leakage and ensure good equipment sealing.

[0006] The hydrogen electric heating equipment does not produce open flames when working, reducing the risk of fire and explosion. The use of electric heating can realize the direct conversion of electrical energy into hydrogen thermal energy, avoiding the energy loss caused by electrolytic hydrogen production. In general, the energy consumption of heating hydrogen by electric heating can be reduced by about 20% compared with heating by hydrogen combustion. The use of electric heating can effectively improve energy utilization efficiency and reduce energy waste.

[0007] Electric heating generally uses silicon-molybdenum rods to heat hydrogen. When silicon-molybdenum rods are used in a high-temperature oxidizing atmosphere, the maximum operating temperature is 1700°C. A dense quartz (SiO2) glass film will quickly form on the surface. This film can protect the inner layer of the silicon-molybdenum rod from further oxidation, thereby extending its service life. However, in a reducing atmosphere such as hydrogen, this protective film may be destroyed, thus affecting its service life. In addition, there is a certain proportion of water vapor in the hydrogen-based vertical furnace top gas after being purified by cyclone dust removal, water spraying, pressurization and other processes. At high temperatures, water vapor will also react with silicon-molybdenum rods, accelerating their aging. Summary of the invention

[0008] The purpose of the present invention is to provide a design scheme suitable for hydrogen electric heating equipment of hydrogen-based vertical furnace, which is used to solve the reduction reaction between high-temperature hydrogen and heating rods, affecting the life of the heating rods and thus affecting the overall service life of the heating furnace.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] 1. The silicon-molybdenum heating rods of the hydrogen-based vertical furnace electric heating furnace are isolated from hydrogen to avoid the aging of the silicon-molybdenum rods caused by the reduction reaction between the silicon-molybdenum rods and hydrogen under high temperature conditions;

[0011] 2. The hydrogen-based vertical furnace heating furnace has a three-stage structure. The heating rod on one side can be quickly separated from the heating furnace shell, and the other side is located at the end of the heating pipe, which is convenient for personnel to regularly clean the scale inside the heating furnace;

[0012] 3. Add a spoiler device to the outer wall of the silicon-molybdenum rod heating tube cover of the heating furnace to increase the effective heat exchange area between the heat exchange tube and hydrogen, and improve the heat exchange efficiency of the heated hydrogen;

[0013] 4. The head of the heating rod of the hydrogen-based vertical furnace electric heating furnace is protected by nitrogen, which, on the one hand, reduces the temperature of the heating rod head and the connecting flange surface, and on the other hand, ensures the balance of internal pressure.

[0014] Compared with the prior art, the present invention has the following technical effects: the pure hydrogen electric heating furnace adopts a split structure to avoid the reduction reaction of the silicon-molybdenum rod when it comes into direct contact with hydrogen under high temperature conditions, thereby increasing the life of the heating rod; and adopts a three-stage structure to facilitate personnel to regularly clean the scale of the heating furnace and replace the heating rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Assembly drawing of hydrogen-based vertical furnace split pure hydrogen high temperature electric heating device

[0016] Figure 2 The structure diagram of the electric heating system for the hydrogen-based vertical furnace

[0017] Figure 3The main structure of the hydrogen-based vertical furnace is easy to disassemble.

[0018] Figure 4 Connection diagram of hydrogen-based vertical furnace heating furnace body and heating system

[0019] Figure 5 The hot hydrogen outlet pipeline structure diagram of the hydrogen-based vertical furnace DETAILED DESCRIPTION

[0020] 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.

[0021] The purpose of the present invention is to improve the service life of the heating rod and the safety of the equipment by adopting a split pure hydrogen electric heating furnace design, and at the same time adopt a three-stage electric heating furnace to facilitate the daily maintenance of the pure hydrogen electric heating equipment.

[0022] The iron ore flows from the preheating section to 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:

[0023]

[0024] This process is an endothermic reaction. The furnace must maintain a high reaction temperature and continuously introduce a large amount of high-temperature hydrogen to maintain the internal temperature balance so that the reduction reaction can proceed continuously and efficiently.

[0025] The use of electric heating can improve the heating safety of hydrogen and improve the overall energy utilization 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. There will be energy loss in the process of electrolysis of water. Direct use of electric heating can shorten the overall heating process and improve the comprehensive energy utilization rate.

[0026] Hydrogen-based vertical furnace split type pure hydrogen high temperature electric heating Figure 1 As shown, pure hydrogen can be heated from room temperature to 1050°C. It consists of three parts: an electric heating system, a heating furnace body, and a hot hydrogen outlet pipeline.

[0027] The heating system structure is as follows Figure 2 As shown, it includes an electric heating control system 101, a silicon-molybdenum rod heating body 102, a flange connecting plate 103, a nitrogen inlet 104, a nitrogen outlet 105, an outlet gas temperature detection 106, an outlet gas pressure detection 107 and other devices. The electrode is heated by a silicon-molybdenum rod, the melting point of the silicon-molybdenum rod is 2030°C, the heating power is adjusted to meet different heating temperature requirements, and the flange connecting plate 103 is connected to the heating furnace body by hard sealing bolts.

[0028] The heating furnace body structure is as follows Figure 3As shown, it includes a heating furnace shell 201, a refractory material guard plate 202, a hydrogen inlet pipe 203, a support frame 204, a spoiler device 205, a refractory material 206, a connecting flange 207, a heating pipe bottom plate 208, a heating pipe 209, a heating furnace support 210, an outlet gas pressure detection 211 and other devices. The heating pipe 209 is connected to the heating pipe bottom plate 208 by welding, so that the hydrogen is isolated from the silicon-molybdenum rod heating body 102, avoiding the occurrence of high-temperature reduction reaction. The heating pipe adopts a nickel-based alloy 2080 high-temperature alloy tube. The melting point range of the nickel-based alloy is 1357-1430°C. It performs well in a high-temperature environment and can be burned at a high temperature of 1200°C without oxidation or deformation. It has good stability and reliability and meets the requirements of hydrogen heating at 1050°C. The spoiler device 205 is connected to the heating tube 209 by welding. The spoiler will form small eddies and small bubbles, which increase the contact area between the gas and the surface. Therefore, the gas can contact the surface more fully and stay longer, thereby achieving efficient heat exchange and improving thermal efficiency. The refractory material adopts a three-layer castable structure (mullite, lightweight, fiber felt), which can reduce the temperature of the heating furnace shell 201 to below 100°C. The support frame 204 supports the heating tube 209. The support frame is a mesoporous structure that allows gas to pass through the middle of the support frame. There is a boss structure at the contact between the refractory guard plate 202 and the bottom plate 208 of the heating tube, forming the first seal, and then the brick guard plate and the bottom plate of the heating tube are connected by a bolt hard seal connection to form a second seal. The two seals ensure that hydrogen cannot enter the heating tube cavity, preventing high-temperature hydrogen from reacting with the silicon-molybdenum rod. The outlet gas pressure detection 211 detects the outlet pressure. If the pressure after heating is lower than the internal pressure of the vertical furnace, the pressure of the inlet hydrogen needs to be adjusted so that the high-temperature hydrogen can stably and smoothly enter the interior of the vertical furnace.

[0029] The heating furnace body is connected to the heating system as follows Figure 4 As shown, the connection flange 207 of the heating furnace body 2 is connected to the flange connection plate 103 of the heating system 1 by using hard sealing bolts, and there is a boss structure to isolate the heating rod distribution cavity from the outside air, thereby ensuring the airtightness of the heating rod distribution cavity. The internal pressure of the hydrogen heating cavity needs to be consistent with the internal pressure of the vertical furnace (0.4MPa). Normal temperature hydrogen enters the hydrogen heating cavity from the hydrogen inlet. Due to the presence of a turbulent device on the heating tube, the entering hydrogen exchanges heat with the heating tube to complete the heating of the hydrogen. At this time, the high-temperature hydrogen cannot enter the heating rod distribution cavity due to the obstruction of the heating tube wall to react with the silicon-molybdenum rod.

[0030] A small amount of nitrogen enters the heating rod distribution cavity from the nitrogen inlet and flows out of the heating rod distribution cavity from the nitrogen outlet. The pressure inside the heating rod distribution cavity is slightly higher than the pressure of the hydrogen heating cavity, generally 0.05MPa higher than the heating cavity pressure. If the heating tube leaks, the nitrogen will enter the hydrogen heating cavity due to the high pressure inside the heating rod distribution cavity, and will not cause high-temperature hydrogen to enter the heating rod distribution cavity. Since the gap between the silicon-molybdenum rod and the inner wall of the heating tube is small, during the heating process of the silicon-molybdenum rod, only a small part of the nitrogen in the gap between the heating tube and the silicon-molybdenum rod will flow out with the flow of nitrogen, which can improve the heating efficiency of the heating system. At the same time, the circulation of nitrogen in the heating rod distribution cavity can reduce the temperature of the flange connecting plate 103, the heating furnace shell 201, the refractory protective plate 202, the connecting flange 207, the heating tube bottom plate 208, etc., thereby improving the overall safety of the equipment. The nitrogen outlet is equipped with a thermocouple and a pressure gauge. The outlet gas temperature is measured by the thermocouple to adjust the nitrogen intake, and the outlet gas pressure is measured by the pressure gauge. If there is a leak in the hydrogen heating cavity and the heating rod distribution cavity, the pressure in the heating rod distribution cavity will decrease and be fed back to the pressure gauge, which is convenient for personnel to troubleshoot the heating furnace failure.

[0031] After the furnace top gas is purified by dust removal, dehydration and purification such as cyclone dust removal and water removal device, the circulating hydrogen will be accompanied by a certain amount of dust and water vapor. As the circulating hydrogen enters the heating furnace, some dust is enriched on the heating tube and the support frame, affecting the circulation speed of the heating hydrogen and reducing the amount of heating hydrogen in the heating furnace. As a result, the pellets in the vertical furnace cannot react with sufficient hot hydrogen, reducing the metallization rate of the sponge iron product. Further dust enrichment for a long time may block the hydrogen flow channel, causing the heating furnace to fail to work normally. The three-stage structure is convenient for personnel to disassemble the interior of the heating furnace. At the same time, bolts are used to connect the refractory guard plate and the bottom plate of the heating tube. After removing the connecting bolts, the heating tube can be directly pulled out from the gas inlet side, which is convenient for personnel to clean and maintain the heating tube wall and the spoiler device.

[0032] The hot hydrogen outlet pipe 3 is as follows Figure 5 As shown, it includes a connecting flange 301, a gas temperature detector 302, a heating furnace shell 303, a tapered refractory material 304 and other devices, which are connected to the heating furnace body through the connecting flange 301, and the interior is insulated by refractory materials. The gas temperature detector 302 monitors the temperature of the hot hydrogen at the outlet of the heating furnace, and adjusts the power of the heating rod to control the gas outlet temperature. The hot hydrogen outlet pipeline is connected to the expansion joint, and the interior of the pipeline is insulated with refractory materials, which directly leads to the interior of the vertical furnace body to avoid energy loss during the transmission of hot hydrogen caused by too long a pipeline.

[0033] The advantages of the split structure design of pure hydrogen high temperature electric heating are:

[0034] 1. The heating rod distribution cavity and the hydrogen heating cavity are isolated from each other to avoid the reduction reaction between the surface of the silicon-molybdenum heating rod and the high-temperature hydrogen and water vapor, thereby increasing the life of the silicon-molybdenum rod;

[0035] 2. Nitrogen is filled into the heating rod distribution cavity to reduce the temperature of the heating rod head and the connector. The pressure of the heating rod distribution cavity is greater than that of the hydrogen heating cavity, which prevents hydrogen leakage from the hydrogen heating cavity and improves the overall safety of the heating furnace.

[0036] 3. The heating furnace adopts a three-section structure design, which is convenient for maintenance personnel to repair the internal structure of the heating furnace and replace parts.

Claims

1. A design scheme for hydrogen electric heating equipment for hydrogen-based vertical furnaces, used to solve the problem of high-temperature hydrogen and heating rods undergoing reduction reactions that reduce their service life, characterized in that: 1) The hydrogen-based vertical furnace electric heating furnace adopts an isolated design method for the silicon-molybdenum heating rod and hydrogen to avoid the reduction reaction between the silicon-molybdenum rod and hydrogen under high temperature conditions, which may cause the aging of the silicon-molybdenum rod; 2) The three-stage structure of the hydrogen-based vertical furnace heating furnace. The heating rod on one side can be quickly separated from the heating furnace shell, and the other side is located at the end of the heating pipe, which is convenient for personnel to regularly clean the scale inside the heating furnace; 3) Add a spoiler device to the outer wall of the silicon-molybdenum rod heating tube cover of the heating furnace to increase the effective heat exchange area between the heat exchange tube and the hydrogen, and improve the heat exchange efficiency of the heated hydrogen; 4) The head of the heating rod of the hydrogen-based vertical furnace electric heating furnace is protected by nitrogen, which, on the one hand, reduces the temperature of the heating rod head and the connecting flange surface, and on the other hand, ensures the balance of internal pressure.

2. The detailed structural design of a split type pure hydrogen high temperature electric heating device according to claim 1 is characterized in that: The hydrogen-based vertical furnace split-type pure hydrogen high-temperature electric heating is shown in Figure 1. It can heat pure hydrogen from room temperature to 1050 degrees Celsius. It consists of three parts: electric heating system, heating furnace body, and hot hydrogen outlet pipeline. The structure of the heating system is shown in FIG2 , and includes an electric heating control system 101 , a silicon-molybdenum rod heating body 102 , a flange connecting plate 103 , a nitrogen inlet 104 , a nitrogen outlet 105 , an outlet gas temperature detection 106 , an outlet gas pressure detection 107 and other devices. The main structure of the heating furnace is shown in Figure 3, including a heating furnace shell 201, a refractory protective plate 202, a hydrogen inlet pipe 203, a support frame 204, a spoiler device 205, a refractory material 206, a connecting flange 207, a heating pipe bottom plate 208, a heating pipe 209, a heating furnace support 210, an outlet gas pressure detection 211 and other devices. The heating furnace body is connected to the heating system as shown in FIG4 . Nitrogen is filled into the heating rod distribution cavity to reduce the temperature of the heating rod head and the connector. The pressure of the heating rod distribution cavity is greater than that of the hydrogen heating cavity to prevent hydrogen leakage from the hydrogen heating cavity. The hot hydrogen outlet pipeline 3 is shown in FIG. 5 , and includes a connecting flange 301 , a gas temperature detector 302 , a heating furnace shell 303 , a variable-diameter cone-mouth refractory material 304 and other devices.

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