Method for making steel by using magnesium hydride

Abstract

The invention relates to the technical field of metallurgy, in particular to a method for making steel by using magnesium hydride, which comprises the steps of iron ore pretreatment, magnesium hydride release system starting, heating smelting, reduction reaction, slag-iron separation, molten iron casting, tail gas treatment and the like. Controllable supply of hydrogen is achieved by releasing magnesium hydride in a pulse mode, and energy consumption and pollution are reduced in combination with a fluxing agent and a tail gas recovery system. According to the method, carbon emission can be remarkably reduced, the steel quality is improved, meanwhile, resource recycling is achieved, and the important industrial application value and environmental protection significance are achieved.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically a process for steel smelting using magnesium hydride as a hydrogen source. Background Technology

[0002] Iron and steel smelting, as a crucial foundation of modern industry, occupies a vital position in the national economy. However, traditional iron and steel smelting processes generally employ carbonaceous reducing agents to reduce iron ore. This process is not only energy-intensive but also generates large amounts of greenhouse gases and harmful substances such as carbon dioxide and sulfur dioxide, causing severe environmental pollution. With the escalating global energy crisis and increasingly stringent environmental protection requirements, traditional iron and steel smelting processes can no longer meet the demands of green and low-carbon development. Developing a highly efficient, energy-saving, and environmentally friendly iron and steel smelting technology has become an urgent problem to solve. Hydrogen, as a clean reducing agent and energy carrier, possesses high energy density and zero carbon emissions, and has received widespread attention in recent years.

[0003] However, the high cost and safety concerns associated with hydrogen storage and transportation limit its widespread application in steelmaking. Magnesium hydride, as a novel hydrogen storage material, offers new possibilities for steelmaking due to its high hydrogen storage capacity, good safety profile, and moderate decomposition temperature. Introducing magnesium hydride into the steelmaking process not only enables controlled hydrogen release but also utilizes the heat released during magnesium oxidation to further reduce energy consumption, thus significantly improving energy efficiency. However, currently, there is no mature technology to fully leverage the advantages of magnesium hydride and efficiently apply it to the steelmaking process. Therefore, developing a magnesium hydride-based steelmaking process can solve the problems of high energy consumption and high pollution associated with traditional processes, while also overcoming the technical bottlenecks in hydrogen storage and use. This is of great significance for promoting the green transformation and sustainable development of the steel industry. Summary of the Invention

[0004] This invention addresses the shortcomings of existing steelmaking processes, such as high energy consumption, high pollution, and low energy utilization. To this end, it provides a steelmaking process that utilizes magnesium hydride as a hydrogen source. The process achieves a controllable low-equivalent hydrogen supply through pulsed release of magnesium hydride, combined with a fluxing agent and tail gas treatment system, thereby reducing energy consumption and pollution while improving steel quality.

[0005] This invention provides a method for steelmaking using magnesium hydride, comprising the following steps: S1, pretreating iron ore; S2, activating a magnesium hydride release system and controlling the quantitative release of hydrogen; S3, loading iron ore into a smelting furnace and raising the furnace temperature to a set range using heat generated by an external heating device or the combustion of a reducing agent; S4, utilizing the released hydrogen to undergo a reduction reaction with iron oxide in the iron ore at high temperature, generating metallic iron and water vapor; S5, adding an appropriate amount of flux during the smelting process to form slag and separate it from the metallic iron; S6, releasing the molten iron from the smelting furnace for subsequent processing; S7, collecting and treating the tail gas generated during the smelting process. Wherein:

[0006] S1 includes crushing, screening, and magnetic separation of the iron ore to limit the particle size to between 3 mm and 20 mm, achieving a purity of over 95%. Further, the magnesium hydride is prepared using mechanical ball milling or plasma methods, producing magnesium hydride powder with a purity of over 99.9%, which is stored in a dedicated container to prevent moisture absorption and oxidation. The dedicated container has a dry gas protective layer inside and an insulating material on its outer wall to ensure the stability of the magnesium hydride during storage.

[0007] In step S2, the magnesium hydride release system is activated via a timed and quantitative pulsed release mechanism controlled by a control system. Specifically, the amount of hydrogen released per minute is 1 / 10 to 1 / 20 of the total demand. Further, the control system includes a pressure sensor, a flow meter, and a solenoid valve. The pressure sensor monitors the pressure of the hydrogen produced by the decomposition of magnesium hydride in real time, the flow meter detects the hydrogen release flow rate, and the solenoid valve adjusts the hydrogen release rate according to a set program. Specifically, the decomposition temperature range of magnesium hydride is 300°C to 400°C. The magnesium oxide powder produced during the decomposition process is collected and regenerated into magnesium hydride powder through a closed-loop process, achieving a recovery efficiency of over 95%.

[0008] In step S3, the temperature inside the smelting furnace is gradually increased to a range of 1000°C to 1500°C by the heat generated from the external heating device or the combustion of part of the reducing agent. Furthermore, the external heating device employs resistance heating or induction heating, achieving a thermal efficiency of over 85%. Specifically, the reducing agent includes a small amount of coke or hydrogen, used at 1% to 5% of the iron ore weight, to supplement the insufficient hydrogen produced by the decomposition of magnesium hydride.

[0009] In step S4, hydrogen reacts chemically with iron oxide in the iron ore at high temperature to produce metallic iron and water vapor. Furthermore, the molar ratio of hydrogen to iron oxide is 1:1 to 3:1 to ensure complete reduction of the iron oxide to metallic iron. Specifically, the water vapor generated during the reaction is recovered through a condenser, achieving a recovery rate of over 90%.

[0010] In step S5, the flux includes limestone or dolomite, and its addition amount is 5% to 15% of the weight of the iron ore. Further, the flux reacts with impurities in the iron ore at high temperature to generate slag, the melting point of which is in the range of 1200°C to 1400°C. Specifically, the separation of the slag from the metallic iron is achieved through gravity settling; the molten iron settles at the bottom of the furnace, while the slag floats on top of the molten iron.

[0011] In step S6, molten iron is discharged from the taphole at the bottom of the smelting furnace, and after slag removal and deoxidation, it is cast into billets or directly hot-rolled. Further, the slag removal process employs a filter screen device, and the deoxidation process is achieved by adding aluminum powder or ferrosilicon alloy, with the deoxidizer dosage being 0.1% to 0.5% of the weight of the molten iron.

[0012] In step S7, the exhaust gas treatment includes water vapor condensation and recovery, unreacted hydrogen recovery and reuse, and harmful gas purification. Furthermore, the water vapor condensation and recovery device achieves a condensation efficiency of over 90%, and the unreacted hydrogen is recovered to a storage tank via a compressor for later use. Specifically, the harmful gases, including carbon monoxide and sulfur dioxide, are purified through combustion or adsorption, achieving a purification efficiency of over 95%.

[0013] The innovations of this invention are as follows: First, by releasing magnesium hydride in a pulsed manner, a controllable low-equivalent supply of hydrogen is achieved, avoiding excessive hydrogen supply and waste, and improving hydrogen utilization efficiency. Second, a closed-loop process is used to regenerate the magnesium oxide produced by decomposition into magnesium hydride, realizing resource recycling with a recovery efficiency of over 95%. Third, by precisely controlling the molar ratio of hydrogen to iron oxide and the amount of flux added, the probability of side reactions is significantly reduced, and the efficiency of the reduction reaction is improved.

[0014] Furthermore, the technical effects of this invention are achieved through the following means: First, the hydrogen produced by the decomposition of magnesium hydride serves as a reducing agent, replacing the traditional carbonaceous reducing agent, thus reducing emissions of greenhouse gases such as carbon dioxide and sulfur dioxide to less than 10% of those produced by traditional processes. Second, water vapor and unreacted hydrogen in the exhaust gas are recycled through a recovery device, increasing energy utilization to over 90%. In particular, the hydrogen reduction reaction can more effectively remove impurities, including sulfur and phosphorus, from iron ore, resulting in steel with a purity of over 99% and superior mechanical properties compared to steel products produced by traditional processes.

[0015] In summary, this invention, by introducing magnesium hydride as a hydrogen source and combining it with pulsed release technology and automated control methods, achieves low-carbon, environmentally friendly, and efficient steelmaking. This process not only significantly reduces energy consumption and pollution but also improves the quality and added value of steel products, possessing significant industrial application value and market prospects. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall process flow of the present invention.

[0017] The attached figures are labeled as follows:

[0018] 1. Vibrating screen; 2. Pneumatic mixer; 3. Preheating chamber; 4. Furnace body; 5. Electromagnetic pulse injector; 6. Radiant heat exchanger; 7. Steam turbine; 8. Generator; 9. Plate heat exchanger; 10. Cyclone separator; 11. Alkali spray tower; 12. Electrostatic precipitator; 13. MgO collection chamber; 14. Molten steel discharge tank; 15. Vacuum degassing device; 16. Continuous casting machine; 17. Control cabinet; 18. PLC controller. Detailed Implementation

[0019] This invention provides a method for steelmaking using magnesium hydride, combined with... Figure 1 The detailed structural diagrams and Arabic numeral labels of each component in the diagram illustrate the specific implementation of this invention. The following content uses an actual production scenario in a steel plant as an example to comprehensively explain the specific operation process, operating principle, and technical effects of this technology.

[0020] In practical applications, the first step is to pre-treat the raw materials. Iron ore undergoes initial processing using a vibrating screen (1) to crush large pieces of ore to a particle size range of 3mm to 20mm. Subsequently, impurities are removed using magnetic separation equipment to ensure the iron ore purity reaches over 95%. Simultaneously, magnesium hydride powder is prepared using mechanical ball milling, achieving a purity of over 99.9%, and stored in a dedicated container. This container has an internal dry gas protection layer and an outer wall covered with insulating material to prevent the magnesium hydride from absorbing moisture or oxidizing. Fluxes such as limestone and dolomite are prepared at 5% to 15% of the iron ore weight for slag-iron separation in subsequent smelting processes.

[0021] After the smelting process is started, the pneumatic mixer 2 uniformly mixes the pretreated iron ore with a small amount of coke, and then conveys it into the furnace body 4. At this time, the electromagnetic pulse injector 5 is activated, and the control system realizes the timed and quantitative release of magnesium hydride. The pressure sensor of the control system monitors the pressure of hydrogen gas produced by the decomposition of magnesium hydride in real time, the flow meter detects the hydrogen release flow rate, and the solenoid valve adjusts the hydrogen release rate according to the set program. The decomposition temperature range of magnesium hydride is 300℃ to 400℃, and the amount of hydrogen gas released per minute is 1 / 10 to 1 / 20 of the total demand. This pulsed release method ensures the controllability and efficiency of hydrogen supply, avoiding resource waste caused by oversupply.

[0022] With the activation of the magnesium hydride release system, the external heating device begins operation, gradually raising the temperature inside furnace 4 to between 1000℃ and 1500℃. Heating methods can be either resistance heating or induction heating, achieving a thermal efficiency of over 85%. During this process, some coke or hydrogen is burned as an auxiliary reducing agent to generate heat, supplementing the insufficient hydrogen produced by the decomposition of magnesium hydride. Hydrogen reacts chemically with iron oxide in the iron ore to produce metallic iron and water vapor. The molar ratio of hydrogen to iron oxide is strictly controlled between 1:1 and 3:1 to ensure complete reduction of iron oxide to metallic iron. The generated water vapor is condensed and recovered into the preheating chamber 3 via plate heat exchanger 9, achieving a recovery rate of over 90%.

[0023] Under high-temperature conditions, the added limestone or dolomite flux reacts with impurities in the iron ore to form slag, the melting point of which ranges from 1200℃ to 1400℃. Gravity settling separates the slag from the metallic iron; the molten iron settles at the bottom of the furnace, while the slag floats on top. A cyclone separator 10 further separates incompletely reacted fine particles, ensuring the purity of both the slag and the molten iron. The molten iron is discharged from the taphole at the bottom of the furnace body 4 and passes through the molten steel discharge tank 14 into subsequent processing stages.

[0024] The molten iron undergoes slag removal and deoxidation in a vacuum degassing unit 15. A filter removes residual impurities, and aluminum powder or ferrosilicon alloy is added to the molten iron as a deoxidizer at a rate of 0.1% to 0.5% of its weight. The deoxidized molten iron is then cast into billets using a continuous casting machine 16 or directly hot-rolled to form the final steel product. Throughout the process, a tail gas treatment unit collects and purifies the tail gas generated during smelting. A steam turbine 7 and a generator 8 utilize the energy of steam to generate electricity, improving energy efficiency. An alkaline spray tower 11 and an electrostatic precipitator 12 adsorb and purify harmful gases, achieving a purification efficiency of over 95%. Unreacted hydrogen is recovered by a compressor and stored in a gas storage tank for later use, realizing resource recycling.

[0025] Of particular note is that the magnesium oxide powder produced during the decomposition of magnesium hydride is regenerated into magnesium hydride powder through a closed-loop process. MgO collection chamber 13 collects the magnesium oxide powder, which is then processed and reprocessed into high-purity magnesium hydride, achieving a recovery efficiency of over 95%. This closed-loop design significantly reduces raw material costs while minimizing waste emissions, achieving the goal of zero waste.

[0026] To further verify the technical effects of the present invention, the following description is provided in conjunction with embodiments. In an experiment at a small steel plant, hematite ore with a particle size of 10mm to 20mm was selected and, after pretreatment, loaded into a 10m³ volume. 3In a hydrogen-based vertical shaft furnace, magnesium hydride powder is stored in a dedicated tank, and a pulse-release system is set to release hydrogen at a rate of 50 m³ / h. 3 The process involves smelting at 1200℃ for 8 hours to produce approximately 8 tons of molten iron with a purity exceeding 99%. The water vapor and unreacted hydrogen in the tail gas are recovered at rates exceeding 90% and 80% respectively, significantly reducing production costs and environmental pollution. Another steel company uses this process to remelt scrap steel. After crushing and sorting the scrap steel, it mixes it with a small amount of fresh iron ore. By adjusting parameters such as the release of magnesium hydride and the reaction temperature, they have successfully achieved efficient recycling of scrap steel, producing high-quality recycled steel products while reducing reliance on primary iron ore mining.

[0027] In summary, this invention, by introducing magnesium hydride as a hydrogen source and combining it with pulsed release technology and automated control methods, achieves low-carbon, environmentally friendly, and efficient steelmaking. This process significantly reduces energy consumption and pollution, improves the quality and added value of steel products, and has significant industrial application value and market prospects.

Claims

1. A method for refining steel with magnesium hydride, characterized in that The method comprises the following steps: Pretreatment of iron ore; start-up of magnesium hydride release system and control of quantitative release of hydrogen; loading of iron ore into a smelting furnace and increasing the temperature in the furnace to a set range by means of external heating devices or heat generated by combustion of reducing agents; reduction reaction of iron oxide in the iron ore with hydrogen released at high temperature to generate metallic iron and water vapor; addition of a suitable fluxing agent to form a slag and separate from the metallic iron during smelting; tapping of liquid iron from the smelting furnace and subsequent processing; collection and treatment of tail gas generated during smelting.

2. The method of claim 1, wherein The pretreatment of iron ore includes crushing, screening and magnetic separation by a vibrating screen separator (1) to limit the particle size range of the iron ore to 3-20 mm and to achieve a purity of more than 95%.

3. The method of claim 2, wherein The magnesium hydride powder is prepared by mechanical ball milling or plasma method, has a purity of more than 99.9%, and is stored in a special container with a dry gas protective layer inside and a heat insulation material on the outer wall.

4. The method of claim 1, wherein The start-up of the magnesium hydride release system is realized by a control system to achieve a timed and quantitative pulse release mode, with a hydrogen release amount of 1 / 10 to 1 / 20 of the total demand per minute.

5. The method of claim 4, wherein The control system includes a pressure sensor, a flow meter and a solenoid valve, wherein the pressure sensor is used to monitor the hydrogen pressure generated by the decomposition of magnesium hydride in real time, the flow meter is used to detect the hydrogen release flow, and the solenoid valve adjusts the release rate of hydrogen according to the set program.

6. The method of claim 1, wherein The temperature in the smelting furnace is gradually increased to 1000-1500°C by means of heat generated by external heating devices or partial combustion of reducing agents, and the external heating devices use resistance heating or induction heating.

7. The method of claim 6, wherein The reducing agent includes coke or hydrogen, and the amount is 1-5% by weight of the iron ore.

8. The method of claim 1, wherein The fluxing agent includes limestone or dolomite, and the amount is 5-15% by weight of the iron ore. The fluxing agent reacts with impurities in the iron ore at high temperature to generate a slag, and the melting point of the slag is 1200-1400°C.

9. The method of claim 1, wherein The tail gas treatment includes water vapor condensation recovery, unreacted hydrogen recovery and reuse, and harmful gas purification treatment, and the condensation efficiency of the water vapor condensation recovery device is more than 90%.

10. The method of claim 1 wherein the liquid is water. The liquid iron is tapped from the tapping hole at the bottom of the smelting furnace, cast into a cast slab after deslagging and deoxidation treatment, or directly subjected to hot rolling processing, and the deoxidation process is realized by adding aluminum powder or ferrosilicon alloy, and the amount of deoxidizer is 0.1-0.5% by weight of the liquid iron.

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