A plasma-assisted ammonia direct reduction smelting system and method

Abstract

The present invention discloses a plasma-assisted ammonia direct reduction smelting system and method, which belongs to the field of gas-based vertical furnace reduction technology. The system includes a gas supply unit, a cracking hydrogen production unit, a hydrogen-based vertical furnace smelting unit, and a tail gas treatment and heat exchange unit; the gas outlet of the gas supply unit is connected to the plasma torch of the cracking hydrogen production unit, and the gas outlet of the cracking tube is connected to the reducing gas inlet of the hydrogen-based vertical furnace unit. Advantages: Plasma-assisted combustion technology is used to make the difficult-to-burn ammonia burn more fully, without CO2 emissions, and achieve the purpose of energy conservation and emission reduction; plasma-assisted ammonia combustion is used to provide heat for ammonia cracking, and the hydrogen-rich reducing gas is heated to 850-900°C, which not only reduces the dependence of the hydrogen production process on electrical energy, but also realizes direct reduction smelting of hydrogen vertical furnaces, and realizes a full-chain clean smelting technical approach; at the same time, the overall device is allowed to operate at a higher working gas pressure. The process of the present invention is simple, the structure is clear, the layout is reasonable, and the energy-saving and emission-reduction effects are obvious.

Description

Technical Field

[0001] The invention relates to the fields of industrial metallurgy, plasma and ammonia application, and in particular to a plasma-assisted ammonia direct reduction smelting system and method. Background Art

[0002] As the foundation of national economic construction, the metallurgical industry provides the materials and products needed by various industries such as machinery, energy, chemical industry, transportation, construction, aerospace, and national defense industry. At present, blast furnace ironmaking technology is very mature and is the main production method for ironmaking. Except for a small amount of iron produced by direct reduction method using H2+ CO or natural gas as heat energy and reducing agent, the vast majority of iron is produced by blast furnace using coal as fuel and reducing agent. The biggest pollution in the steel industry is the large amount of CO2 emissions.

[0003] The method of using carbon as a reducing agent for blast furnace smelting is already very mature. With the increasing pressure on carbon emission reduction in the steel industry, traditional blast furnace smelting can no longer meet the current dual carbon goals. If the goal of low-carbon production is to be achieved while ensuring production, the application of hydrogen metallurgical technology is the only choice. The vertical furnace direct reduction-electric furnace short process based on hydrogen metallurgy is currently the most concerned area in the steel industry. It has the advantages of low carbon emissions, clean reduction products, and efficient reduction reactions. It has been widely promoted and applied abroad. Among them, technologies represented by Midrex and HYL have been built and scaled up all over the world.

[0004] The direct reduction process is a process that reduces iron oxides at a temperature below the melting point to obtain metallic iron. Its product is direct reduced iron. Direct reduced iron is used in electric furnace steelmaking and has the advantages of pure texture, stable chemical composition, low content of harmful impurities, and easy control of steel composition. It is an ideal raw material for replacing scrap steel and smelting high-quality steel and special steel. The development of electric furnace steelmaking in China is relatively slow, far below the world average. The gas-based direct reduction technology has the advantages of pure products, low cost, energy conservation and emission reduction, and simplified processes. The development of gas-based direct reduction technology has good prospects.

[0005] Compared with the traditional blast furnace ironmaking method that uses carbon monoxide gas as a reducing agent to remove oxygen from iron ore, hydrogen reduction technology uses hydrogen as a reducing agent. Hydrogen molecules are much smaller than carbon monoxide molecules and can easily penetrate into the interior of iron ore. Its penetration rate is about 5 times that of carbon monoxide molecules. The reduction potential of hydrogen is much higher than that of carbon monoxide, and rapid reduction can be achieved in theory. The direct reduction ironmaking reaction formula based on the principle of hydrogen metallurgical reaction is as follows: Fe2O3 + 3H2 = 2Fe + 3H2O. In addition, when hydrogen is used to reduce iron oxide, its main products are metallic iron and water vapor. The tail gas has no adverse effect on the environment and can significantly reduce the load on the environment. Therefore, hydrogen is the cleanest.

[0006] At present, the main gas sources used for hydrogen-based reduction are natural gas and coke oven gas. However, natural gas and coke oven gas do not meet the composition requirements of reducing gas. In order to convert natural gas without reducing ability into gas with reducing ability, natural gas is generally reformed, which cannot achieve the carbon reduction effect. Due to the scarcity of natural gas resources and the high cost of electrolytic gas production, the development of hydrogen direct reduction technology is slow. In the long run, the provision of large-scale cheap hydrogen will strongly promote the rapid development of gas-based direct reduction. Summary of the invention

[0007] The technical problem of the present invention is: in view of the carbon emission problem of using carbon-containing reducing gas as a gas source, and the problems of short equipment life and difficult control of process parameters in plasma metallurgy technology, the present invention provides a plasma-assisted ammonia direct reduction smelting system and method, which selects ammonia as the gas source of reducing gas, and uses plasma to directly crack ammonia into hydrogen-based reducing gas of hydrogen or a hydrogen-ammonia mixture, and simultaneously uses plasma-assisted ammonia combustion to provide heat for direct reduction smelting, thereby changing the traditional smelting of metallic iron's dependence on fossil fuels and avoiding the pollution of the surrounding environment by CO2 and polluting gases generated during the smelting process.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is as follows: first, air plasma is generated by a plasma torch to assist combustion of ammonia, and the heat generated is used to heat the cracking tube, and the ammonia is cracked into hydrogen and nitrogen under the action of a catalyst, and heated to 850-900°C, and the iron ore is reduced with hydrogen as a reducing agent to obtain direct reduced iron; the second set of technical schemes adopted by the present invention is as follows: first, air plasma is generated by a plasma torch, ammonia is introduced downstream of the plasma, and the ammonia is rapidly reformed with the plasma. The high-energy electrons generated by the plasma discharge can break the chemical bonds of the ammonia molecules, decomposing them into atomic hydrogen atoms and nitrogen atoms, and the two hydrogen atoms combine to generate hydrogen. The microwave plasma can heat the hydrogen-rich reducing gas to 1000-1500°C, and the iron ore is reduced with hydrogen as a reducing agent to obtain direct reduced iron.

[0009] The technical solution adopted by the present invention is: a plasma-assisted ammonia direct reduction smelting system, including a gas supply unit, a cracking hydrogen production unit, a hydrogen-based vertical furnace smelting unit, and a tail gas treatment and heat exchange unit;

[0010] The gas supply unit includes a liquid ammonia storage tank, a liquid ammonia pump, a gasification chamber, a mixing chamber, a main fan, a scrubber, and a compressor, and is used to deliver ammonia and combustion-supporting air into the reformer of the cracking hydrogen production unit;

[0011] The cracking hydrogen production unit comprises a plasma torch, a cracking tube and a converter. The plasma torch and the cracking tube are installed on the converter. Part of the ammonia is burned by plasma-assisted combustion to provide heat for the cracking of the ammonia sent into the cracking tube. At the same time, the hydrogen and nitrogen generated by the cracking of the ammonia are heated to 850-900° C. The cracking tube is connected to the reducing gas inlet of the reducing section of the hydrogen-based vertical furnace smelting unit.

[0012] The hydrogen-based vertical furnace smelting unit comprises a hopper, an upper gas seal, a reduction section, a cooling section, a lower gas seal, a reduced iron outlet, a reducing gas inlet, a furnace top gas outlet, a cooling gas outlet, a cooling gas inlet, a scrubber and a pressurizer. The hopper is arranged above the reduction section, the oxidized pellets are fed into the reduction section through the hopper, the hydrogen-rich reducing gas fed into the reduction gas inlet enters the reduction section and reacts with the oxidized pellets through the reduction gas inlet, and a scrubber and a pressurizer are arranged outside the cooling section below the reduction section, which are connected to the cooling gas outlet and the cooling gas inlet, respectively.

[0013] The exhaust gas treatment and heat exchange unit includes a heat exchanger, a scrubber, a compressor and a chimney. The high-temperature combustion exhaust gas is connected to the heat exchanger through the combustion exhaust gas outlet, and the waste heat is recovered to preheat the combustion air and the raw gas ammonia. The heat exchanger outlet is respectively connected to the chimney and the upper gas seal and lower gas seal of the hydrogen-based vertical furnace smelting unit.

[0014] Furthermore, the liquid ammonia storage tank, the liquid ammonia pump, and the vaporization chamber are sealed and connected by corrosion-resistant metal pipes such as stainless steel and carbon steel. Liquid ammonia is pumped out from the liquid ammonia storage tank by the liquid ammonia pump. After being pumped out by the liquid ammonia pump, the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve and enters the vaporization chamber through the corrosion-resistant metal pipe.

[0015] Furthermore, the gasified ammonia is divided into two paths and respectively sent into two mixing chambers. A gas flow control valve is provided at the entrance of the mixing chamber to control the flow of ammonia entering the mixing chamber. One path of ammonia is sent into the plasma torch through a corrosion-resistant metal pipe, and the other path of ammonia is sent into a cracking tube for cracking to produce hydrogen.

[0016] Furthermore, the main fan provides combustion-supporting air, and the combustion-supporting air is sent into the plasma torch through a compressor to provide circulation power;

[0017] Furthermore, after the combustion-supporting air and ammonia are fed into the plasma torch, they are burned by plasma-assisted combustion technology to heat the cracking tube;

[0018] Furthermore, the plasma torch may be a sliding arc plasma, a microwave plasma, a DC arc plasma, or a radio frequency plasma, and the operating mode may be a continuous wave mode or a pulse mode, wherein the pulse frequency in the pulse mode is 1 Hz-100 kHz, and the duty cycle is 1%-99%;

[0019] Furthermore, the combustion exhaust gas is sent to the heat exchanger through the combustion exhaust gas outlet to recover the waste heat;

[0020] Furthermore, after the combustion tail gas is discharged from the heat exchanger, a part of it is sent to the chimney through a compressor and discharged into the atmosphere, and the rest of it is sent to the upper gas seal of the furnace top and the lower gas seal of the furnace bottom as sealing gas after passing through the scrubber and the compressor;

[0021] Furthermore, the combustion-supporting air and the fuel ammonia gas need to be preheated in the heat exchanger before being fed into the plasma torch to increase the combustion temperature;

[0022] Furthermore, a heat exchange fin is welded and fixed in the cracking tube to increase the occurrence of ammonia cracking reaction in the cracking tube; a catalyst bed is placed in the cracking tube; the plasma torch heats the catalyst bed and the ammonia staying in the cracking tube by burning ammonia, and the ammonia is heated to 850-900° C. under the joint action of the cracking tube and the catalyst to produce a cracked mixed gas, and part of the ammonia is cracked into hydrogen and nitrogen in the cracking tube; the cracked mixed gas is a hydrogen-rich reducing gas, a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen;

[0023] Further, the catalyst bed is 10-30%wt nickel-alumina, 10-30%wt cobalt-alumina, 10-30%wt ruthenium-alumina, iron catalyst, manganese catalyst, palladium catalyst, lanthanum catalyst, molybdenum catalyst, or any combination thereof;

[0024] Furthermore, the upper gas seal is a relatively thin pipe provided below the hopper, which guides the charge into the reduction section, and part of the combustion tail gas is sent to the upper gas seal on the furnace top as sealing gas after passing through the scrubber and the compressor;

[0025] Furthermore, a reducing gas inlet is provided at the lower end of the reducing section, and a furnace top gas outlet is provided at the upper end. The hydrogen-rich reducing gas is fed into the reducing section of the shaft furnace through the reducing gas inlet, and an airflow from bottom to top is formed in the reducing section. The charge completes the preheating process in the reducing gas airflow. As the temperature rises, the reduction reaction of the charge gradually accelerates, and finally direct reduced iron is formed. The temperature of the reducing section is mainly determined by the reducing gas temperature.

[0026] Furthermore, the reducing gas forms a top gas after passing through the charge, and the top gas is discharged from the reducing stage through the top gas outlet. The top gas contains residual H2, which is cleaned and cooled by the scrubber to condense excess water vapor, thereby reducing the degree of oxidation.

[0027] Further, a portion of the cleaned top gas is sent to the mixing chamber to be mixed with ammonia, and then passed into a plasma torch for combustion, and the combustion temperature can reach 1000-1500°C; the remaining cleaned top gas is sent to the mixing chamber through a compressor to be mixed with ammonia, passed into the heat exchanger for preheating, and then passed into the cracking tube for cracking to prepare hydrogen reduction gas;

[0028] Furthermore, a cooling section is provided below the reduction section, a cooling gas outlet is provided at the upper end of the cooling section, and a cooling gas inlet is provided at the lower end of the cooling section. The scrubber completes the cleaning and cooling process of the reduction gas to prepare cooling gas, and the cooling gas is provided with circulation power by the compressor to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section, it is cooled to ambient temperature in the cooling airflow;

[0029] Furthermore, after the direct reduced iron is cooled to ambient temperature, it is discharged through the lower gas seal and the reduced iron outlet;

[0030] Furthermore, the present invention provides a second device for preparing hydrogen-rich reducing gas, which does not require a cracking tube and a catalyst when preparing hydrogen reducing gas. Combustion-supporting air is fed into the plasma torch to generate air plasma, and ammonia is introduced downstream thereof. The plasma is used to crack the ammonia to prepare reducing gas hydrogen. The cracked mixed gas is hydrogen-rich reducing gas, which is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen.

[0031] Furthermore, the present invention provides a third device for preparing hydrogen-rich reducing gas. When preparing hydrogen reducing gas, no cracking tube, catalyst and air are required. Ammonia is directly fed into the plasma torch to generate plasma, and the ammonia is cracked to prepare reducing gas hydrogen. The cracked mixed gas is hydrogen-rich reducing gas, which is a mixture of ammonia, hydrogen and nitrogen, or a mixture of nitrogen and hydrogen.

[0032] The present invention also discloses a plasma-assisted ammonia direct reduction smelting method, comprising: the liquid ammonia storage tank, the liquid ammonia pump, and the gasification chamber are sealed and connected by corrosion-resistant metal pipes such as stainless steel and carbon steel; the liquid ammonia is pumped out from the liquid ammonia storage tank through the liquid ammonia pump; the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve after being pumped out by the liquid ammonia pump, and enters the gasification chamber through the corrosion-resistant metal pipe; the gasified ammonia is divided into two paths and respectively sent to two mixing chambers; a gas flow control valve is provided at the entrance of the mixing chamber to control the flow of ammonia entering the mixing chamber, one path of ammonia is sent to the plasma torch through the corrosion-resistant metal pipe, and the other path of ammonia is sent to the cracking tube The main fan provides combustion-supporting air, and the combustion-supporting air is sent to the plasma torch through the compressor to provide circulation power; after the combustion-supporting air and ammonia are sent to the plasma torch, they are burned through the plasma-assisted combustion technology to heat the cracking tube; the combustion tail gas is sent to the heat exchanger through the combustion tail gas outlet to recover the waste heat; after the combustion tail gas is discharged from the heat exchanger, a part of it is sent to the chimney through a compressor and discharged into the atmosphere, and the rest is sent to the upper gas seal on the top of the furnace and the lower gas seal on the bottom of the furnace as sealing gas after passing through the scrubber and the compressor; before the combustion-supporting air and the fuel ammonia are sent to the plasma torch, they need to be heated in the heat exchanger. The invention relates to a method for preheating the cracking tube to increase the combustion temperature; a heat exchange fin is welded and fixed in the cracking tube to increase the occurrence of ammonia cracking reaction in the cracking tube; a catalyst bed is placed in the cracking tube; the plasma torch heats the catalyst bed and the ammonia remaining in the cracking tube by burning ammonia, and the ammonia is heated to 850-900°C under the joint action of the cracking tube and the catalyst to undergo a cracking reaction to produce a cracked mixed gas, and part of the ammonia is cracked into hydrogen and nitrogen in the cracking tube; the cracked mixed gas is a hydrogen-rich reducing gas, a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen; the hydrogen-based vertical furnace smelting unit is provided at the top with The hopper is used to receive the charge and guide the charge into the upper gas seal; the upper gas seal is a thinner pipe arranged below the hopper, which guides the charge into the reduction section, and part of the combustion tail gas is sent to the upper gas seal on the top of the furnace as sealing gas after passing through the scrubber and the compressor; the lower end of the reduction section is provided with a reducing gas inlet, and the upper end is provided with a furnace top gas outlet. The hydrogen-rich reducing gas is sent into the reduction section of the vertical furnace through the reducing gas inlet, and an airflow from bottom to top is formed in the reduction section. The charge completes the preheating process in the reducing gas airflow. As the temperature rises, the reduction reaction of the charge is gradually accelerated, and finally direct reduced iron is formed. Its chemical reaction equation is as follows: Fe2O3 + 3H2 = 2Fe + 3H2O, the temperature of the reduction stage is mainly determined by the temperature of the reducing gas; the reducing gas forms top gas after passing through the charge, and the top gas is discharged from the reduction stage through the top gas outlet. The top gas contains residual H2, which is cleaned and cooled by the scrubber to condense excess water vapor, thereby reducing the degree of oxidation; a portion of the cleaned top gas is sent to the mixing chamber to mix with ammonia, and then passed into the plasma torch for combustion, and the combustion temperature can reach 1000-1500°C;The remaining cleaned furnace top gas is sent to the mixing chamber through the compressor to mix with ammonia, passed into the heat exchanger for preheating, and then passed into the cracking tube for cracking to prepare hydrogen reduction gas; the cooling section is below the reduction section, the upper end of the cooling section is provided with a cooling gas outlet, and the lower end of the cooling section is provided with a cooling gas inlet. The scrubber completes the cleaning and cooling process of the reduction gas to prepare cooling gas, and the cooling gas is provided with circulation power by the compressor to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section, it is cooled to the ambient temperature in the cooling airflow and discharged through the lower gas seal and the reduced iron outlet. ;

[0033] The present invention provides a second method for preparing hydrogen-rich reducing gas. When preparing hydrogen reducing gas, no cracking tube and catalyst are required. Air is fed into the plasma torch to generate air plasma, and ammonia is introduced downstream thereof. The plasma is used to crack the ammonia to prepare reducing gas hydrogen. The cracked mixed gas is hydrogen-rich reducing gas, which is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen.

[0034] The present invention provides a third device for preparing hydrogen-rich reducing gas. When preparing hydrogen reducing gas, no cracking tube, catalyst and air are required. Ammonia is directly sent into the plasma torch to generate plasma, and the ammonia is cracked to prepare reducing gas hydrogen. The cracked mixed gas is hydrogen-rich reducing gas, which is a mixture of ammonia, hydrogen and nitrogen, or a mixture of nitrogen and hydrogen.

[0035] The advantages of the present invention are:

[0036] The present invention utilizes plasma technology, selects ammonia as the gas source of reducing gas, utilizes plasma to directly crack ammonia into hydrogen or hydrogen-ammonia mixture of hydrogen-based reducing gas, and utilizes plasma to assist ammonia combustion to provide heat for direct reduction ironmaking, thereby changing the traditional smelting of metallic iron's dependence on fossil fuels, avoiding the pollution of the surrounding environment by CO2 and polluting gases generated during the smelting process, and utilizing electricity to replace fuel heating, thereby greatly reducing the fuel cost per unit product. The cost of producing hydrogen by plasma cracking ammonia is much lower than that of traditional technologies, thereby greatly reducing the cost of hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of a plasma-assisted ammonia cracking hydrogen-based vertical furnace direct reduction system according to Example 1 of the present invention.

[0038] Figure 2 This is a schematic diagram of a plasma-assisted ammonia cracking hydrogen-based vertical furnace direct reduction system according to Example 2 of the present invention.

[0039] Figure 3 This is a schematic diagram of a plasma-assisted ammonia cracking hydrogen-based vertical furnace direct reduction system according to Example 3 of the present invention.

[0040] In the figure, 1-liquid ammonia storage tank, 2-liquid ammonia pump, 3-gasification chamber, 4-first mixing chamber, 5-second mixing chamber, 6-main fan, 7-first compressor, 8-heat exchanger, 9-converter, 10-plasma torch, 11-cracking tube, 12-hydrogen vertical furnace, 13-hopper, 14-upper gas seal, 15-reduction section, 16-cooling section, 17-lower gas seal, 18-reduced iron outlet, 19-reduction gas inlet, 20-furnace top gas outlet, 21-first scrubber, 22-second compressor, 23-cooling gas outlet, 24-second scrubber, 25-third compressor, 26-cooling gas inlet, 27-combustion tail gas outlet, 28-third scrubber, 29-fourth compressor, 30-fifth compressor, 31-chimney, 32-ammonia inlet. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention are described clearly and completely below in conjunction with the accompanying drawings and embodiments. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] like Figure 1 As shown, the plasma-assisted ammonia direct reduction smelting system provided by the present invention includes a gas supply unit, a cracking hydrogen production unit, a hydrogen-based vertical furnace smelting unit, and a tail gas treatment and heat exchange unit.

[0044] The gas supply unit includes a liquid ammonia storage tank 1, a liquid ammonia pump 2, a gasification chamber 3, a first mixing chamber 4, a second mixing chamber 5, a main fan 6, a first compressor 7, a first scrubber 21, and a second compressor 22; the liquid ammonia storage tank 1, the liquid ammonia pump 2 and the gasification chamber 3 are connected in sequence through corrosion-resistant metal pipes. Liquid ammonia is pumped out from the liquid ammonia storage tank 1 through the liquid ammonia pump 2. After being pumped out by the liquid ammonia pump 2, the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve and enters the gasification chamber 3 through a corrosion-resistant metal pipe; the gasification chamber 3 is respectively connected to the first mixing chamber 4 and the second mixing chamber 5 through a corrosion-resistant metal three-way pipe, and the gasified ammonia is divided into two paths and sent to the first mixing chamber 4 and the second mixing chamber 5 respectively. The inlets of the first mixing chamber 4 and the second mixing chamber 5 are provided with gas flow control valves to control the flow of ammonia entering the first mixing chamber 4 and the second mixing chamber 5. The first mixing chamber 4 and the cracking tube 11 are connected through corrosion-resistant metal The second mixing chamber 5 is connected with the plasma torch 10 of the cracking hydrogen production unit through a corrosion-resistant metal pipeline, wherein one ammonia gas flows out of the second mixer 5 and is sent to the plasma torch 10 through a corrosion-resistant metal pipe, and the other ammonia gas flows out of the first mixer 4 and is heat exchanged by a heat exchanger 8, and then sent to the cracking tube 11 of the cracking hydrogen production unit for cracking and hydrogen production; the main fan 6 is connected with the first compressor 7 and the plasma torch 10 in sequence through metal pipelines, and the main fan 6 provides combustion-supporting air, and the combustion-supporting air is sent to the plasma torch 10 of the cracking hydrogen production unit through the first compressor 7 to provide circulation power. The upper limit of the pressure resistance of the corrosion-resistant metal pipe is 75MPa.

[0045] The cracking hydrogen production unit comprises a reforming furnace 9, a plasma torch 10 and a cracking tube 11. The combustion tail gas outlet 27 is arranged on the side wall of the reforming furnace 9. The plasma torch 10 is installed on the converter 9, and the cracking tube 11 is installed in the converter 9; after the combustion-supporting air and ammonia are fed into the plasma torch 10, they are burned by plasma-assisted combustion technology to heat the cracking tube 11; heat exchange fins are welded and fixed in the cracking tube 11 to increase the occurrence of ammonia cracking reaction in the cracking tube; the catalyst bed is placed in the cracking tube 11; the plasma torch 10 heats the catalyst bed and the ammonia staying in the cracking tube 11 by burning ammonia, and the ammonia is heated to 850-900° C. under the joint action of the cracking tube 11 and the catalyst to undergo a cracking reaction to produce a cracked mixed gas, and part of the ammonia is cracked into hydrogen and nitrogen in the cracking tube 11; the cracked mixed gas is hydrogen-rich reducing gas, that is, a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen; the cracking tube 11 is connected to the reducing gas inlet 19 of the reducing section 15 of the hydrogen-based vertical furnace smelting unit.

[0046] The catalyst bed is 10-30%wt nickel-alumina, 10-30%wt cobalt-alumina, 10-30%wt ruthenium-alumina, iron catalyst, manganese catalyst, palladium catalyst, lanthanum catalyst, molybdenum catalyst, or any combination thereof.

[0047] The plasma torch can be sliding arc plasma, microwave plasma, DC arc plasma, or radio frequency plasma, and the working mode can be a continuous wave mode or a pulse mode. In the pulse mode, the pulse frequency is 1 Hz-100 kHz, and the duty cycle is 1%-99%.

[0048] The hydrogen-based vertical furnace smelting unit comprises a hydrogen vertical furnace 12, a hopper 13, an upper gas seal 14, a reduction section 15, a cooling section 16, a lower gas seal 17, a reduced iron outlet 18, a reduction gas inlet 19, a furnace top gas outlet 20, a cooling gas outlet 23, a second scrubber 24, a third compressor 25 and a cooling gas inlet 26; the hopper 13 is located at the top of the hydrogen vertical furnace 12, and the hopper 13 is connected to the reduction section 15 through the upper gas seal 14. The hopper 13 is used to receive the furnace charge and introduce the furnace charge into the upper gas seal 14; the upper gas seal 14 is a thinner pipe arranged below the hopper to transfer the furnace charge to the upper gas seal 14. The material is introduced into the reduction section 15, and part of the combustion tail gas is divided into two paths after passing through the third scrubber 28 and the fourth compressor 29, one path is sent to the upper gas seal 14 of the furnace top as sealing gas, and the other path is sent to the lower gas seal 17 of the furnace bottom as sealing gas; the lower end of the side wall of the reduction section 15 is provided with a reduction gas inlet 19, and the upper end is provided with a furnace top gas outlet 20, and the furnace top gas outlet 20 of the hydrogen vertical furnace 12 is connected to the first scrubber 21, and the first scrubber 21 is connected to the second mixing chamber 5 and the second compressor 22 through metal pipes, and the second compressor 22 is connected to the first mixing chamber 4 through metal pipes. The reduction section 15 is provided with a reduction gas inlet 19 at the lower end and a furnace top gas outlet 20 at the upper end.The hydrogen-rich reducing gas from the cracking tube 11 is fed into the vertical furnace reduction section 15 through the reducing gas inlet 19, and a bottom-up airflow is formed in the reducing section 15. The charge is preheated in the reducing gas flow. As the temperature rises, the reduction reaction of the charge is gradually accelerated, and finally direct reduced iron is formed. The chemical reaction equation is as follows: Fe2O3 + 3H2 = 2Fe + 3H2O, the temperature of the reduction section is mainly determined by the temperature of the reducing gas; the reducing gas forms a top gas after passing through the charge, and the top gas is discharged from the reducing section 15 through the top gas outlet 20. The top gas contains residual H2, which is cleaned and cooled by the first scrubber 21 to condense excess water vapor to reduce the degree of oxidation; a portion of the cleaned top gas is sent to the second mixing chamber 5 to mix with ammonia, and is passed into the plasma torch 10 for combustion, and the combustion temperature can reach 1000-1500°C; the remaining cleaned top gas is sent to the first mixing chamber 4 through the second compressor 22 to mix with ammonia, passed into the heat exchanger 8 for preheating, and then passed into the cracking tube 11 for cracking to prepare hydrogen reducing gas; the cooling section 16 is located below the reducing section 15, and the upper end of the side wall of the cooling section 16 is provided with A cooling gas outlet 23 and a cooler inlet 26 are provided at the lower end; the cooling gas outlet 23, the second scrubber 24, the third pressurizer 25, and the cooling gas inlet 26 are connected in sequence through stainless steel pipes; the lower air seal 17 is located below the cooling section 16, and a reduced iron outlet 18 is provided at the bottom of the lower air seal 17. The cooling section 16 is below the reduction section 15, and a cooling gas outlet 23 is provided at the upper end of the cooling section 16, and a cooling gas inlet 26 is provided at the lower end of the cooling section 16. The second scrubber 24 completes the cleaning and cooling process of the reduction gas to prepare cooling gas, and the cooling gas is provided with a circulation power by the pressurizer 26 to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section 16, it is cooled to ambient temperature in the cooling airflow and discharged through the lower air seal 17 and the reduced iron outlet 18.

[0049] The tail gas treatment and heat exchange unit includes a heat exchanger 8, a combustion tail gas outlet 27, a third scrubber 28, a fourth compressor 29, a fifth compressor 30 and a chimney 31; the combustion tail gas outlet 27 is connected to the heat exchanger 8 through a metal pipe, and the combustion tail gas is sent to the heat exchanger 8 through the combustion tail gas outlet 27 to recover the waste heat; the heat exchanger 8 is connected to the fifth compressor 30 and the chimney 31 in sequence through metal pipes, and the heat exchanger 8 is connected to the third scrubber 28 and the fourth compressor 29 in sequence through metal pipes, and the fourth compressor 29 is respectively connected to the upper gas seal 14 and the lower gas seal 17 of the hydrogen-based vertical furnace smelting unit through metal pipes. The combustion tail gas generated by the combustion of ammonia in the plasma torch 10 is sent to the heat exchanger 8 through the combustion tail gas outlet 27 to recover the waste heat. After the combustion exhaust gas is discharged from the heat exchanger 8, a part of it is sent to the chimney 31 through the fifth compressor 30 and discharged into the atmosphere, and the rest is sent to the upper gas seal 14 of the furnace top and the lower gas seal 17 of the furnace bottom as sealing gas after passing through the third scrubber 28 and the fourth compressor 29. Before the combustion air and the fuel ammonia are sent to the plasma torch 10, they need to be preheated in the heat exchanger 8 to increase the combustion temperature.

[0050] Example 2

[0051] The present invention provides a second method for preparing hydrogen-rich reducing gas. When preparing hydrogen reducing gas, no cracking tube and catalyst are required. Air is fed into the plasma torch to generate air plasma, and ammonia is introduced downstream thereof. The plasma is used to crack the ammonia to prepare reducing gas hydrogen. The cracked mixed gas is hydrogen-rich reducing gas, which is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen.

[0052] like Figure 2 As shown, the plasma-assisted ammonia direct reduction smelting system provided by the present invention includes a gas supply unit, a cracking hydrogen production unit, a hydrogen-based vertical furnace smelting unit, and a tail gas treatment and heat exchange unit.

[0053] The gas supply unit includes a liquid ammonia storage tank 1, a liquid ammonia pump 2, a gasification chamber 3, a first mixing chamber 4, a main blower 6, a first compressor 7, a first scrubber 21, and a second compressor 22; the liquid ammonia storage tank 1, the liquid ammonia pump 2 and the gasification chamber 3 are connected in sequence through a corrosion-resistant metal pipe, and the liquid ammonia is pumped out from the liquid ammonia storage tank 1 through the liquid ammonia pump 2, and the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve after being pumped out by the liquid ammonia pump 2, and enters the gasification chamber 3 through a corrosion-resistant metal pipe; the gasification chamber 3 is connected to the first mixing chamber 4 through a corrosion-resistant metal pipe, and the gasified ammonia is sent to the first mixing chamber 4, and a gas flow control valve is provided at the entrance of the first mixing chamber 4 to control the flow of ammonia entering the first mixing chamber 4; the main blower 6 is connected to the first compressor 7 through a metal pipe, and the first compressor 7 is connected to the plasma torch 10 through a corrosion-resistant metal pipe, and the main blower 6 provides air, and the air is sent to the plasma torch 10 of the cracking hydrogen production unit to generate air plasma through the first compressor 7 to provide circulation power.

[0054] The cracking hydrogen production unit includes a converter 9, a plasma torch 10 and an ammonia gas inlet 32; the plasma torch 10 is installed on the converter 9, the ammonia gas inlet 32 ​​is arranged on the side wall of the converter, the first mixing chamber 4 is connected to the ammonia gas inlet 32 ​​arranged on the side wall of the converter 9 through a corrosion-resistant metal pipe, ammonia is introduced downstream of the plasma, the ammonia is cracked by the plasma to prepare reducing gas hydrogen, and the reducing gas temperature is heated to 850-900°C, the cracked mixed gas is hydrogen-rich reducing gas, a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen.

[0055] The hydrogen-based vertical furnace smelting unit comprises a hydrogen vertical furnace 12, a hopper 13, an upper gas seal 14, a reduction section 15, a cooling section 16, a lower gas seal 17, a reduced iron outlet 18, a reduction gas inlet 19, a furnace top gas outlet 21, a cooling gas outlet 23, a second scrubber 24, a third compressor 25 and a cooling gas inlet 26; the hopper 13 is located at the top of the hydrogen vertical furnace 12, and the hopper 13 is connected to the reduction section 15 through the upper gas seal 14. The hopper 13 is used to receive the charge and introduce the charge into the upper gas seal 14; the upper gas seal 14 is a thinner pipe arranged below the hopper 13 to introduce the charge into the reduction section 15. 5; A reducing gas inlet 19 is provided at the lower end of the side wall of the reduction section 15, and a furnace top gas outlet 20 is provided at the upper end. The reformer 9 is connected to the reducing gas inlet 19 of the reduction section 12 of the hydrogen-based vertical furnace smelting unit. The reducing gas inlet 19 is provided at the lower end of the reducing section 15, and a furnace top gas outlet 20 is provided at the upper end. The hydrogen-rich reducing gas flows out of the reformer 9 and is sent into the vertical furnace reduction section 15 through the reducing gas inlet 19, forming a bottom-up airflow in the reducing section 15. The charge completes the preheating process in the reducing gas airflow. As the temperature rises, the reduction reaction of the charge is gradually accelerated, and finally direct reduced iron is formed. The chemical reaction equation is as follows: 6NH3 + 3O2 + Fe2O3 = 2Fe + 3N2 + 9H2O, the temperature of the reduction section is mainly determined by the temperature of the reducing gas; the top gas outlet 20 of the hydrogen vertical furnace 12 is connected to the first scrubber 21, and the first scrubber 21 is connected to the second compressor 22 and the first mixing chamber 4 in sequence through metal pipes. The reducing gas passes through the charge to form the top gas, and the top gas is discharged from the reduction section 15 through the top gas outlet 20. The top gas contains residual H2. A part of the cleaned top gas is sent to the first mixing chamber 4 to mix with ammonia and passed into the plasma torch for combustion and cracking. The combustion temperature can reach 1000-1500°C; the cooling section 16 is located below the reduction section 15; the upper end of the side wall of the cooling section 16 is provided with a cooling gas outlet 23, and the lower end is provided with a cooler inlet 26; The cooling gas outlet 23, the second scrubber 24, the third compressor 25, and the cooling gas inlet 26 are connected in sequence through stainless steel pipes; the lower air seal 17 is located below the cooling section 16, and a reduced iron outlet 18 is provided at the bottom of the lower air seal 17. The cooling section 16 is below the reducing section 15, and a cooling gas outlet 23 is provided at the upper end of the cooling section 16, and a cooling gas inlet 26 is provided at the lower end of the cooling section 16. The second scrubber 24 completes the cleaning and cooling process of the reducing gas to prepare cooling gas, and the cooling gas is provided with a circulation power by the third compressor 25 to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section 16, it is cooled to ambient temperature in the cooling airflow and discharged through the lower air seal 17 and the reduced iron 18 outlet.

[0056] The tail gas treatment and heat exchange unit includes a heat exchanger 8, a third scrubber 28 and a fourth compressor 29; the furnace top gas outlet 20 is connected to the heat exchanger 8 through a stainless steel pipe, and the heat exchanger 8 is connected to the third scrubber 28 and the fourth compressor 29 in sequence through metal pipes, and the fourth compressor 29 is respectively connected to the upper gas seal 14 and the lower gas seal 17 of the hydrogen-based vertical furnace smelting unit through metal pipes, and the remaining furnace top gas is passed into the heat exchanger 8 to recover waste heat for preheating, and then cleaned and cooled by the third scrubber 28 to condense excess water vapor to reduce the degree of oxidation, and then sent to the upper gas seal 14 on the furnace top and the lower gas seal 17 on the furnace bottom as sealing gas after passing through the fourth compressor 29; before air and ammonia are sent to the plasma torch 10 and the converter 9, they need to be preheated in the heat exchanger 8 to increase the combustion temperature.

[0057] The plasma torch can be sliding arc plasma, microwave plasma, DC arc plasma, or radio frequency plasma, and the working mode can be a continuous wave mode or a pulse mode. In the pulse mode, the pulse frequency is 1 Hz-100 kHz, and the duty cycle is 1%-99%.

[0058] Example 3

[0059] The present invention provides a third device for preparing hydrogen-rich reducing gas. When preparing hydrogen reducing gas, no cracking tube, catalyst and air are required. Ammonia is directly sent into the plasma torch to generate plasma, and the ammonia is cracked to prepare reducing gas hydrogen. The cracked mixed gas is hydrogen-rich reducing gas, which is a mixture of ammonia, hydrogen and nitrogen, or a mixture of nitrogen and hydrogen.

[0060] like Figure 3 As shown, the plasma-assisted ammonia direct reduction smelting system provided by the present invention includes a gas supply unit, a cracking hydrogen production unit, a hydrogen-based vertical furnace smelting unit, and a tail gas treatment and heat exchange unit.

[0061] The gas supply unit includes a liquid ammonia storage tank 1, a liquid ammonia pump 2, a gasification chamber 3, a first mixing chamber 4, a first scrubber 21, and a second compressor 22; the liquid ammonia storage tank 1, the liquid ammonia pump 2 and the gasification chamber 3 are connected in sequence through a corrosion-resistant metal pipe, and liquid ammonia is pumped out from the liquid ammonia storage tank 1 through the liquid ammonia pump 2. After being pumped out by the liquid ammonia pump 2, the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve and enters the gasification chamber 3 through a corrosion-resistant metal pipe; the gasification chamber 3 is connected to the first mixing chamber 4 through a corrosion-resistant metal pipe, and the gasified ammonia is sent to the first mixing chamber 4. A gas flow control valve is provided at the entrance of the first mixing chamber 4; the first mixing chamber 4 is connected to the plasma torch 10 through a corrosion-resistant metal pipe, and ammonia is sent to the plasma torch 10 through the corrosion-resistant metal pipe.

[0062] The cracking hydrogen production unit includes a converter 9 and a plasma torch 10; the plasma torch 10 is installed on the converter 9, ammonia is fed into the plasma torch 10 through a corrosion-resistant metal pipe as a working gas to generate plasma, the ammonia is cracked to prepare reducing gas hydrogen and the reducing gas temperature is heated to 850-900°C, the cracked mixed gas is hydrogen-rich reducing gas, a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen; the converter 9 is connected to the reducing gas inlet 19 of the reduction section 15 of the hydrogen-based vertical furnace smelting unit.

[0063] The hydrogen-based vertical furnace smelting unit includes a hydrogen vertical furnace 12, a hopper 13, an upper gas seal 14, a reduction section 15, a cooling section 16, a lower gas seal 17, a reduced iron outlet 18, a reduction gas inlet 19, a furnace top gas outlet 21, a cooling gas outlet 23, a second scrubber 24, a third compressor 25 and a cooling gas inlet 26; the hopper 13 is located at the top of the hydrogen vertical furnace 12, the hopper 13 is connected to the reduction section 15 through the upper gas seal 14, and the hopper 13 is used to receive the furnace charge and introduce the furnace charge into the upper gas seal 14; the upper gas seal 14 is a relatively thin pipe arranged below the hopper 13, which guides the charge into the reduction section 15; the side wall of the reduction section 15 is provided with a reducing gas inlet 19 at the lower end, and a furnace top gas outlet 20 at the upper end. The hydrogen-rich reducing gas is fed into the vertical furnace reduction section 15 through the reducing gas inlet 19, and a bottom-up airflow is formed in the reduction section 15. The charge completes the preheating process in the reducing gas airflow. As the temperature rises, the reduction reaction of the charge is gradually accelerated, and finally direct reduced iron is formed. The chemical reaction equation is as follows: Fe2O3 +3H2 = 2Fe + 3H2O, the temperature of the reduction section is mainly determined by the temperature of the reducing gas; the top gas outlet 20 of the hydrogen vertical furnace 12 is connected to the first scrubber 21, and the first scrubber 21 is connected to the second compressor 22 and the first mixing chamber 4 in sequence through metal pipes. The reducing gas passes through the charge to form the top gas, and the top gas is discharged from the reduction section 15 through the top gas outlet 20. The top gas contains residual H2. A part of the cleaned top gas is sent to the first mixing chamber 4 to mix with ammonia and passed into the plasma torch for combustion and cracking. The combustion temperature can reach 1000-1500°C; the cooling section 16 is located below the reduction section 15; the upper end of the side wall of the cooling section 16 is provided with a cooling gas outlet 23, and the lower end is provided with a cooler inlet 26; The cooling gas outlet 23, the second scrubber 24, the third compressor 25, and the cooling gas inlet 26 are connected in sequence through stainless steel pipes; the lower air seal 17 is located below the cooling section 16, and a reduced iron outlet 18 is provided at the bottom of the lower air seal 17. The cooling section 16 is below the reducing section 15, and a cooling gas outlet 23 is provided at the upper end of the cooling section 16, and a cooling gas inlet 26 is provided at the lower end of the cooling section 16. The second scrubber 24 completes the cleaning and cooling process of the reducing gas to prepare cooling gas, and the cooling gas is provided with a circulation power by the third compressor 25 to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section 16, it is cooled to ambient temperature in the cooling airflow and discharged through the lower air seal 17 and the reduced iron 18 outlet.

[0064] The tail gas treatment and heat exchange unit includes a heat exchanger 8, a third scrubber 28 and a fourth compressor 29; the furnace top gas outlet 20 is connected to the heat exchanger 8 through a stainless steel pipe, and the heat exchanger 8 is connected to the third scrubber 28 and the fourth compressor 29 in sequence through metal pipes, and the fourth compressor 29 is respectively connected to the upper gas seal 14 and the lower gas seal 17 of the hydrogen-based vertical furnace smelting unit through metal pipes; the remaining furnace top gas is passed into the heat exchanger 8 to recover waste heat for preheating, and then cleaned and cooled by the third scrubber 28 to condense excess water vapor to reduce the degree of oxidation, and then sent to the upper gas seal 14 of the furnace top and the lower gas seal 17 of the furnace bottom as sealing gas after passing through the compressor 29; air and ammonia need to be preheated in the heat exchanger 8 before being sent to the plasma torch 10 and the converter 9 to increase the combustion temperature.

[0065] The plasma torch can be sliding arc plasma, microwave plasma, DC arc plasma, or radio frequency plasma, and the working mode can be a continuous wave mode or a pulse mode. In the pulse mode, the pulse frequency is 1 Hz-100 kHz, and the duty cycle is 1%-99%.

[0066] The present invention does not elaborate on some of the common technologies of those skilled in the art. The above-described embodiments are only descriptions of preferred implementations of the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementations described. Without departing from the design spirit of the present invention, various modifications and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A plasma-assisted ammonia direct reduction smelting system, characterized in that: The system includes a gas supply unit, a cracking hydrogen production unit, a hydrogen-based vertical furnace smelting unit, and a tail gas treatment and heat exchange unit; The gas supply unit includes a liquid ammonia storage tank, a liquid ammonia pump, a gasification chamber, a first mixing chamber, a second mixing chamber, a main fan, a first compressor, a first scrubber and a second compressor; the liquid ammonia storage tank, the liquid ammonia pump and the gasification chamber are connected in sequence through metal pipes, and the upper limit of the pressure resistance of the metal pipe is 75MPa; the gasification chamber is connected to the first mixing chamber and the second mixing chamber respectively through a metal three-way pipe; the main fan is connected to the first compressor through a metal pipe; the top gas is passed into the first scrubber through the top gas outlet of the hydrogen vertical furnace, and the first scrubber is connected to the second mixing chamber and the second compressor respectively through metal pipes; the second compressor is connected to the first mixing chamber through a metal pipe; the first compressor and the second mixing chamber are respectively connected to the plasma torch through metal pipes, and combustion-supporting air and ammonia are respectively passed into the plasma torch; the first mixing chamber is connected to the cracking tube through a metal pipe for feeding ammonia into the cracking tube; The cracking hydrogen production unit comprises a plasma torch, a cracking tube and a converter; the plasma torch is installed on the converter, the cracking tube is installed in the converter, part of the ammonia is introduced into the plasma torch to provide heat for the ammonia introduced into the cracking tube through plasma-assisted combustion, and the hydrogen and nitrogen generated by the cracking of the ammonia are heated to 850-900° C., and the cracking tube is connected to the reducing gas inlet of the reducing section of the hydrogen-based vertical furnace smelting unit; The hydrogen-based vertical furnace smelting unit comprises a hydrogen vertical furnace, a hopper, an upper gas seal, a reduction section, a cooling section, a lower gas seal, a reduced iron outlet, a reduced gas inlet, a furnace top gas outlet, a cooling gas outlet, a cooling gas inlet, a second scrubber and a third pressurizer; the hopper is located at the top of the hydrogen vertical furnace, and the hopper is connected to the reduction section through the upper gas seal; a reduced gas inlet is provided at the lower end of the side wall of the reduction section, and a furnace top gas outlet is provided at the upper end; the cooling section is located below the reduction section; a cooling gas outlet is provided at the upper end of the side wall of the cooling section, and a cooler inlet is provided at the lower end; the cooling gas outlet, the second scrubber, the third pressurizer and the cooling gas inlet are connected in sequence through stainless steel pipes; the lower gas seal is located below the cooling section, and a reduced iron outlet is provided at the bottom of the lower gas seal; The exhaust gas treatment and heat exchange unit includes a heat exchanger, a combustion exhaust gas outlet, a third scrubber, a fourth compressor, a fifth compressor and a chimney; the high-temperature combustion exhaust gas is connected to the heat exchanger through a metal pipe via the combustion exhaust gas outlet, and the waste heat is recovered to preheat the combustion air and fuel ammonia; the heat exchanger is connected to the third scrubber and the fourth compressor in sequence through metal pipes, and the fourth compressor is respectively connected to the upper gas seal and the lower gas seal of the hydrogen-based vertical furnace smelting unit through metal pipes; the heat exchanger is connected to the fifth compressor and the chimney in sequence through metal pipes to discharge the combustion exhaust gas.

2. The system according to claim 1, characterized in that: The liquid ammonia storage tank, the liquid ammonia pump, and the vaporization chamber are sealed and connected by a stainless steel or carbon steel metal pipe. The liquid ammonia is pumped out from the liquid ammonia storage tank by the liquid ammonia pump. After being pumped out by the liquid ammonia pump, the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve and enters the vaporization chamber through the metal pipe. The gasified ammonia is divided into two paths and respectively sent into the first mixing chamber and the second mixing chamber. A gas flow control valve is provided at the gas inlet of the mixing chamber to control the flow of ammonia entering the mixing chamber. One path of ammonia passes through the second mixing chamber and is sent to the plasma torch via a metal pipe, and the other path of ammonia passes through the first mixing chamber and is sent to the cracking tube via a metal pipe for cracking and hydrogen production. The main fan provides combustion-supporting air, and the combustion-supporting air is supplied to the plasma torch through the first compressor to provide circulation power; After the combustion-supporting air and ammonia are fed into the plasma torch, they are burned by plasma-assisted combustion technology to heat the cracking tube; The plasma torch is a sliding arc plasma, a microwave plasma, a DC arc plasma or a radio frequency plasma, and the working mode is a continuous wave mode or a pulse mode. In the pulse mode, the pulse frequency is 1 Hz-100 kHz, and the duty cycle is 1%-99%; The combustion tail gas is sent to the heat exchanger through the combustion tail gas outlet to recover the residual heat; After the combustion tail gas is discharged from the heat exchanger, a part of it is sent to the chimney through the fifth compressor and discharged into the atmosphere, and the rest of it is sent to the upper gas seal of the top of the hydrogen vertical furnace and the lower gas seal of the furnace bottom as sealing gas after passing through the third scrubber and the fourth compressor; The combustion-supporting air and the fuel ammonia gas need to be preheated in the heat exchanger before being fed into the plasma torch; Heat exchange fins are welded and fixed in the cracking tube; the catalyst bed is placed in the cracking tube; the plasma torch heats the catalyst bed and the ammonia remaining in the cracking tube by burning ammonia, and the ammonia is heated to 850-900° C. under the joint action of the cracking tube and the catalyst to produce a cracked mixed gas, and part of the ammonia is cracked into hydrogen and nitrogen in the cracking tube; the cracked mixed gas is hydrogen-rich reducing gas; the hydrogen-rich reducing gas is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen; The catalyst bed is one or any combination of 10-30%wt nickel-alumina, 10-30%wt cobalt-alumina, 10-30%wt ruthenium-alumina, iron catalyst, manganese catalyst, palladium catalyst, lanthanum catalyst, and molybdenum catalyst; The hopper is provided at the top of the hydrogen vertical furnace of the hydrogen-based vertical furnace smelting unit, which is used to receive the furnace charge and guide the furnace charge into the upper gas seal; the upper gas seal is a pipeline provided below the hopper, which guides the furnace charge into the reduction section, and part of the combustion tail gas is sent to the upper gas seal on the furnace top as sealing gas after passing through the third scrubber and the fourth compressor; A reducing gas inlet is provided at the lower end of the reduction section, and a furnace top gas outlet is provided at the upper end. The hydrogen-rich reducing gas is fed into the reduction section of the vertical furnace through the reducing gas inlet, forming an airflow from bottom to top in the reduction section. The charge completes the preheating process in the reducing gas airflow. As the temperature rises, the reduction reaction of the charge is gradually accelerated, and finally direct reduced iron is formed. The temperature of the reduction section is mainly determined by the reducing gas temperature.

3. The system according to claim 1, characterized in that: The reducing gas forms a top gas after passing through the charge, and the top gas is discharged from the reducing stage through the top gas outlet. The top gas contains residual H2, which is cleaned and cooled by the first scrubber to condense excess water vapor, thereby reducing the degree of oxidation; A portion of the cleaned top gas is sent to the second mixing chamber to be mixed with ammonia, and then passed into a plasma torch for combustion, with the combustion temperature reaching 1000-1500°C; the rest of the cleaned top gas is sent to the first mixing chamber through a second compressor to be mixed with ammonia, passed into the heat exchanger for preheating, and then passed into the cracking tube for cracking to prepare hydrogen reduction gas; The cooling section is below the reduction section, the upper end of the cooling section is provided with a cooling gas outlet, and the lower end of the cooling section is provided with a cooling gas inlet. The second scrubber completes the cleaning and cooling process of the reduction gas to prepare cooling gas, and the cooling gas is provided with circulation power by the third compressor to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section, it is cooled to ambient temperature in the cooling airflow; After the direct reduced iron is cooled to ambient temperature, it is discharged through the lower gas seal and the reduced iron outlet.

4. A plasma-assisted ammonia direct reduction smelting system, characterized in that: When preparing hydrogen reducing gas, no cracking tube and catalyst are needed. Air is fed into the plasma torch to generate air plasma, and ammonia is introduced downstream thereof. The plasma is used to crack the ammonia to prepare reducing gas hydrogen. The cracked mixed gas is hydrogen-rich reducing gas. The hydrogen-rich reducing gas is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen. The system includes a gas supply unit, a cracking hydrogen production unit, a hydrogen-based vertical furnace smelting unit, and a tail gas treatment and heat exchange unit; The gas supply unit includes a liquid ammonia storage tank, a liquid ammonia pump, a gasification chamber, a first mixing chamber, a main fan, a first compressor, a first scrubber and a second compressor; the liquid ammonia storage tank, the liquid ammonia pump and the gasification chamber are connected in sequence through a metal pipe, and the upper pressure limit of the corrosion-resistant metal pipe is 75MPa; the gasification chamber is connected to the first mixing chamber through a metal pipe; the main fan is connected to the first compressor through a metal pipe; the top gas is passed into the first scrubber through the top gas outlet of the hydrogen vertical furnace, and the first scrubber is connected to the second compressor and the first mixing chamber in sequence through metal pipes; the first compressor is connected to the plasma torch through a metal pipe to pass air into the plasma torch; the first mixing chamber is connected to the ammonia gas inlet arranged on the side wall of the converter through a metal pipe, which is used to feed ammonia into the converter; The cracking hydrogen production unit comprises a plasma torch, a converter and an ammonia gas inlet; the plasma torch is installed on the converter, the ammonia gas inlet is arranged on the side wall of the converter, and is used to feed ammonia gas into the converter, air is passed into the plasma torch to generate plasma, ammonia gas is cracked into hydrogen gas and nitrogen gas, and hydrogen gas and nitrogen gas are heated to 850-900° C., and the converter is connected to the reducing gas inlet of the reducing section of the hydrogen-based vertical furnace smelting unit; The hydrogen-based vertical furnace smelting unit comprises a hydrogen vertical furnace, a hopper, an upper gas seal, a reduction section, a cooling section, a lower gas seal, a reduced iron outlet, a reduced gas inlet, a furnace top gas outlet, a cooling gas outlet, a cooling gas inlet, a second scrubber and a third pressurizer; the hopper is located at the top of the hydrogen vertical furnace, and the hopper is connected to the reduction section through the upper gas seal; a reduced gas inlet is provided at the lower end of the side wall of the reduction section, and a furnace top gas outlet is provided at the upper end; the cooling section is located below the reduction section; a cooling gas outlet is provided at the upper end of the side wall of the cooling section, and a cooler inlet is provided at the lower end; the cooling gas outlet, the second scrubber, the third pressurizer and the cooling gas inlet are connected in sequence through stainless steel pipes; the lower gas seal is located below the cooling section, and a reduced iron outlet is provided at the bottom of the lower gas seal; The tail gas treatment and heat exchange unit includes a heat exchanger, a third scrubber and a fourth compressor; the furnace top gas outlet is connected to the heat exchanger through a stainless steel pipe to recover waste heat to preheat the air and ammonia; the heat exchanger is connected to the third scrubber and the fourth compressor in sequence through metal pipes, and the fourth compressor is respectively connected to the upper gas seal and the lower gas seal of the hydrogen-based vertical furnace smelting unit through metal pipes.

5. The system according to claim 4, characterized in that: The liquid ammonia storage tank, the liquid ammonia pump, and the vaporization chamber are sealed and connected by a stainless steel or carbon steel metal pipe. The liquid ammonia is pumped out from the liquid ammonia storage tank by the liquid ammonia pump. After being pumped out by the liquid ammonia pump, the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve and enters the vaporization chamber through the metal pipe. The gasified ammonia is sent to the first mixing chamber. The air inlet of the mixing chamber is provided with a gas flow control valve to control the flow of ammonia entering the mixing chamber. After passing through the first mixing chamber, the ammonia is sent to the ammonia air inlet on the side wall of the converter through a metal pipe. The main fan provides air, and the air is sent to the plasma torch as a working medium to generate plasma through the first compressor to provide circulation power; After the ammonia is fed into the converter, the temperature is raised to 850-900°C under the action of plasma, a cracking reaction occurs to produce a cracked mixed gas, and part of the ammonia is cracked into hydrogen and nitrogen in the cracking tube; the cracked mixed gas is a hydrogen-rich reducing gas; the hydrogen-rich reducing gas is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen; The plasma torch may be a sliding arc plasma, a microwave plasma, a DC arc plasma, or a radio frequency plasma, and the working mode may be a continuous wave mode or a pulse mode. In the pulse mode, the pulse frequency is 1 Hz-100 kHz, and the duty cycle is 1%-99%; Before the air and ammonia are fed into the plasma torch, they need to be preheated in the heat exchanger to increase the combustion temperature; The hopper is provided at the top of the hydrogen vertical furnace of the hydrogen-based vertical furnace smelting unit, which is used to receive the furnace charge and guide the furnace charge into the upper gas seal; the upper gas seal is a pipeline provided below the hopper, which guides the furnace charge into the reduction section; The reducing section is provided with a reducing gas inlet at the lower end and a furnace top gas outlet at the upper end. The hydrogen-rich reducing gas is fed into the vertical furnace reducing section through the reducing gas inlet, and an airflow from bottom to top is formed in the reducing section. The charge completes the preheating process in the reducing gas airflow. As the temperature rises, the reduction reaction of the charge gradually accelerates, and finally forms direct reduced iron. The temperature of the reducing section is mainly determined by the reducing gas temperature. The reducing gas forms top gas after passing through the charge, and the top gas is discharged from the reducing section through the top gas outlet. The top gas contains residual H2, and part of the top gas is cleaned and cooled by the first scrubber to condense excess water vapor to reduce the degree of oxidation; the other part of the top gas is passed into the heat exchanger to recover waste heat to preheat the air and ammonia; Part of the cleaned top gas is sent to the first mixing chamber to be mixed with ammonia and then sent to the reformer for cracking; the top gas that has passed through the heat exchanger is sent to the upper gas seal of the top of the hydrogen vertical furnace and the lower gas seal of the bottom of the furnace as sealing gas after passing through the third scrubber and the fourth compressor; The cooling section is below the reduction section, the upper end of the cooling section is provided with a cooling gas outlet, and the lower end of the cooling section is provided with a cooling gas inlet. The second scrubber completes the cleaning and cooling process of the reduction gas to prepare cooling gas, and the cooling gas is provided with circulation power by the third compressor to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section, it is cooled to ambient temperature in the cooling airflow; After the direct reduced iron is cooled to ambient temperature, it is discharged through the lower gas seal and the reduced iron outlet.

6. A plasma-assisted ammonia direct reduction smelting system, characterized in that: When preparing hydrogen reducing gas, no cracking tube, catalyst and air are required. Ammonia is directly fed into the plasma torch to generate plasma, and the ammonia is cracked to prepare reducing gas hydrogen. The cracked mixed gas is hydrogen-rich reducing gas; the hydrogen-rich reducing gas is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen; The system includes a gas supply unit, a cracking hydrogen production unit, a hydrogen-based vertical furnace smelting unit, and a tail gas treatment and heat exchange unit; The gas supply unit comprises a liquid ammonia storage tank, a liquid ammonia pump, a gasification chamber, a first mixing chamber, a first scrubber, and a second compressor; the liquid ammonia storage tank, the liquid ammonia pump and the gasification chamber are connected in sequence through a metal pipe, and the upper limit of the pressure resistance of the metal pipe is 75MPa; the gasification chamber is connected to the first mixing chamber through a metal pipe; the top gas is introduced into the first scrubber through the top gas outlet of the hydrogen vertical furnace, and the first scrubber is connected to the second compressor and the first mixing chamber in sequence through metal pipes; the first mixing chamber is connected to the plasma torch through a metal pipe; The cracking hydrogen production unit comprises a plasma torch and a converter; the plasma torch is installed on the converter, ammonia is introduced into the plasma torch to generate plasma, the ammonia is cracked into hydrogen and nitrogen, and the hydrogen and nitrogen are heated to 850-900°C, the converter is connected to the reducing gas inlet of the reducing section of the hydrogen-based vertical furnace smelting unit; The hydrogen-based vertical furnace smelting unit comprises a hydrogen vertical furnace, a hopper, an upper gas seal, a reduction section, a cooling section, a lower gas seal, a reduced iron outlet, a reduced gas inlet, a furnace top gas outlet, a cooling gas outlet, a cooling gas inlet, a second scrubber and a third pressurizer; the hopper is located at the top of the hydrogen vertical furnace, and the hopper is connected to the reduction section through the upper gas seal; a reduced gas inlet is provided at the lower end of the side wall of the reduction section, and a furnace top gas outlet is provided at the upper end; the cooling section is located below the reduction section; a cooling gas outlet is provided at the upper end of the side wall of the cooling section, and a cooler inlet is provided at the lower end; the cooling gas outlet, the second scrubber, the third pressurizer and the cooling gas inlet are connected in sequence through stainless steel pipes; the lower gas seal is located below the cooling section, and a reduced iron outlet is provided at the bottom of the lower gas seal; The tail gas treatment and heat exchange unit includes a heat exchanger, a third scrubber and a fourth compressor; the furnace top gas outlet is connected to the heat exchanger through a stainless steel pipe to recover waste heat to preheat the ammonia; the heat exchanger is connected to the third scrubber and the fourth compressor in sequence through metal pipes, and the fourth compressor is connected to the upper gas seal and the lower gas seal of the hydrogen-based vertical furnace smelting unit through metal pipes.

7. The system according to claim 6, characterized in that: The liquid ammonia storage tank, the liquid ammonia pump, and the vaporization chamber are sealed and connected by a stainless steel or carbon steel metal pipe. The liquid ammonia is pumped out from the liquid ammonia storage tank by the liquid ammonia pump. After being pumped out by the liquid ammonia pump, the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve and enters the vaporization chamber through the metal pipe. The gasified ammonia is sent into the first mixing chamber. A gas flow control valve is provided at the gas inlet of the mixing chamber to control the flow of ammonia entering the mixing chamber. After passing through the first mixing chamber, the ammonia is sent into the plasma torch via a metal pipe to generate plasma. After the ammonia gas is fed into the plasma torch to generate plasma, the temperature is raised to 850-900° C. to generate a cracking reaction to generate a cracking mixed gas, and part of the ammonia is cracked into hydrogen and nitrogen in the cracking tube; the cracking mixed gas is a hydrogen-rich reducing gas; the hydrogen-rich reducing gas is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen; The plasma torch is a sliding arc plasma, a microwave plasma, a DC arc plasma or a radio frequency plasma, and the working mode is a continuous wave mode or a pulse mode. In the pulse mode, the pulse frequency is 1 Hz-100 kHz, and the duty cycle is 1%-99%; The ammonia gas needs to be preheated in the heat exchanger before being fed into the plasma torch; The hopper is provided at the top of the hydrogen vertical furnace of the hydrogen-based vertical furnace smelting unit, which is used to receive the furnace charge and guide the furnace charge into the upper gas seal; the upper gas seal is a pipeline provided below the hopper, which guides the furnace charge into the reduction section; The reducing section is provided with a reducing gas inlet at the lower end and a furnace top gas outlet at the upper end. The hydrogen-rich reducing gas is fed into the vertical furnace reducing section through the reducing gas inlet, and an airflow from bottom to top is formed in the reducing section. The charge completes the preheating process in the reducing gas airflow. As the temperature rises, the reduction reaction of the charge gradually accelerates, and finally forms direct reduced iron. The temperature of the reducing section is mainly determined by the reducing gas temperature. The reducing gas forms top gas after passing through the charge, and the top gas is discharged from the reducing section through the top gas outlet. The top gas contains residual H2, and part of the top gas is cleaned and cooled by the first scrubber to condense excess water vapor to reduce the degree of oxidation; the other part of the top gas is passed into the heat exchanger to recover waste heat to preheat the air and ammonia; Part of the cleaned top gas is sent to the first mixing chamber to be mixed with ammonia and then sent to the reformer for cracking; the top gas that has passed through the heat exchanger is sent to the upper gas seal of the top of the hydrogen vertical furnace and the lower gas seal of the bottom of the furnace as sealing gas after passing through the third scrubber and the fourth compressor; The cooling section is below the reduction section, the upper end of the cooling section is provided with a cooling gas outlet, and the lower end of the cooling section is provided with a cooling gas inlet. The second scrubber completes the cleaning and cooling process of the reduction gas to prepare cooling gas, and the cooling gas is provided with circulation power by the third compressor to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section, it is cooled to ambient temperature in the cooling airflow; After the direct reduced iron is cooled to ambient temperature, it is discharged through the lower gas seal and the reduced iron outlet.

8. A plasma-assisted ammonia direct reduction smelting method, characterized in that: Using the system described in any one of claims 1 to 3, the method comprises: the liquid ammonia storage tank, the liquid ammonia pump, and the vaporization chamber are sealed and connected by a stainless steel or carbon steel metal pipe, the liquid ammonia is pumped out from the liquid ammonia storage tank by the liquid ammonia pump, the liquid ammonia is decompressed and output through the liquid phase pressure reducing valve after being pumped out by the liquid ammonia pump, and enters the vaporization chamber through the metal pipe; the vaporized ammonia is divided into two paths and respectively sent to the first mixing chamber and the second mixing chamber, a gas flow control valve is provided at the entrance of the mixing chamber to control the flow of ammonia entering the mixing chamber, one path of ammonia is sent to the plasma torch through the metal pipe, and the other path of ammonia is sent to the cracking tube for cracking and hydrogen production; the main fan provides combustion-supporting air, and the combustion-supporting air is sent to the plasma through the first compressor to provide circulation power torch; after the combustion-supporting air and ammonia are fed into the plasma torch, they are burned by plasma-assisted combustion technology to heat the cracking tube; the combustion exhaust gas is fed into the heat exchanger through the combustion exhaust gas outlet to recover the waste heat; after the combustion exhaust gas is discharged from the heat exchanger, a part of it is fed into the chimney through the fifth compressor and discharged into the atmosphere, and the rest of it is fed into the upper gas seal on the top of the furnace and the lower gas seal on the bottom of the furnace as sealing gas after passing through the third scrubber and the fourth compressor; the combustion-supporting air and the fuel ammonia need to be preheated in the heat exchanger before being fed into the plasma torch; heat exchange fins are welded and fixed in the cracking tube to increase the occurrence of ammonia cracking reaction in the cracking tube; the catalyst bed is placed in the cracking tube; the plasma torch heats the The catalyst bed and the ammonia gas staying in the cracking tube, the ammonia gas is heated to 850-900°C under the joint action of the cracking tube and the catalyst to undergo a cracking reaction to produce a cracked mixed gas, and part of the ammonia is cracked into hydrogen and nitrogen in the cracking tube; the cracked mixed gas is a hydrogen-rich reducing gas; the hydrogen-rich reducing gas is a mixed gas of ammonia, hydrogen and nitrogen, or a mixed gas of nitrogen and hydrogen; the hopper is provided at the top of the hydrogen-based vertical furnace smelting unit, which is used to receive the furnace charge and guide the furnace charge into the upper gas seal; the upper gas seal is a pipeline provided below the hopper, which guides the furnace charge into the reduction section, and part of the combustion tail gas is sent to the upper gas seal on the top of the furnace as sealing gas after passing through the third scrubber and the fourth compressor; the reduction section is provided with a reducing gas inlet at the lower end and a reducing gas inlet at the upper end The top gas outlet, the hydrogen-rich reducing gas is sent into the reduction section of the vertical furnace through the reducing gas inlet, and a bottom-up airflow is formed in the reduction section. The charge completes the preheating process in the reducing gas airflow. As the temperature rises, the reduction reaction of the charge gradually accelerates, and finally forms direct reduced iron. The temperature of the reduction section is mainly determined by the reducing gas temperature; the reducing gas forms top gas after passing through the charge, and the top gas is discharged from the reduction section through the top gas outlet. The top gas contains residual H2, which is cleaned and cooled by the first scrubber to condense excess water vapor to reduce the degree of oxidation; a part of the top gas cleaned by the first scrubber is sent to the second mixing chamber to mix with ammonia, and then passed into the plasma torch for combustion, and the combustion temperature can reach 1000-1500°C;The remaining cleaned furnace top gas is sent to the first mixing chamber through the second compressor to mix with ammonia, passed into the heat exchanger for preheating, and then passed into the cracking tube for cracking to prepare hydrogen reduction gas; the cooling section is below the reduction section, the upper end of the cooling section is provided with a cooling gas outlet, and the lower end of the cooling section is provided with a cooling gas inlet. The second scrubber completes the cleaning and cooling process of the reduction gas to prepare cooling gas, and the cooling gas is provided with circulation power by the third compressor to form a cooling airflow from bottom to top. After the direct reduced iron enters the cooling section, it is cooled to ambient temperature in the cooling airflow and discharged through the lower gas seal and the reduced iron outlet. ; 9. A plasma-assisted ammonia direct reduction smelting method, characterized in that: Using the system described in any one of claims 4-5, the method includes: when preparing hydrogen reducing gas, no cracking tube and catalyst are required, air is sent into the plasma torch to generate air plasma, ammonia is introduced downstream, and the ammonia is cracked by plasma to prepare reducing gas hydrogen, and the cracked mixed gas is hydrogen-rich reducing gas; the hydrogen-rich reducing gas is a mixture of ammonia, hydrogen and nitrogen, or a mixture of nitrogen and hydrogen.

10. A plasma-assisted ammonia direct reduction smelting method, characterized in that: Using the system described in any one of claims 6-7, the method includes: when preparing hydrogen reducing gas, no cracking tube, catalyst and air are required, ammonia is directly sent into the plasma torch to generate plasma, and the ammonia is cracked to prepare reducing gas hydrogen, and the cracked mixed gas is hydrogen-rich reducing gas; the hydrogen-rich reducing gas is a mixture of ammonia, hydrogen and nitrogen, or a mixture of nitrogen and hydrogen.

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