Steel smelting system and method based on hydrogen-rich reducing gas injection

Abstract

Disclosed in the present invention are a steel smelting system and method based on hydrogen-rich reducing gas injection. The steel smelting system comprises a blast furnace and a hydrogen-rich reducing gas pre-production furnace; hydrogen-rich reducing gas from the hydrogen-rich reducing gas pre-production furnace and pure hydrogen are injected into the blast furnace; generated blast furnace top gas is directed into the hydrogen-rich reducing gas pre-production furnace for decarburization; the hydrogen-rich reducing gas pre-production furnace contains nut coke, biomass particles and waste plastic particles; additionally, dry coal powder and pure oxygen are also injected into the hydrogen-rich reducing gas pre-production furnace to prepare hydrogen-rich reducing gas.

Description

A steel smelting system and method based on hydrogen-rich reducing gas injection Technical Field

[0001] The present invention relates to steel smelting, and in particular to a steel smelting system and method based on hydrogen-rich reducing gas injection. Background Art

[0002] In 2022, China's crude steel output reached 1.013 billion tons. The blast furnace-converter (BOF) process, based on carbon metallurgy and iron ore, accounts for approximately 90% of this output. Blast furnace ironmaking, after centuries of technological development and innovation, boasts mature technology, high production capacity, and high efficiency. Combined with China's abundant coal, low oil, and limited natural gas resources, the blast furnace is expected to remain the mainstream ironmaking equipment supporting China's massive demand for steel for decades to come.

[0003] However, due to the limitations of its own process, technology and equipment conditions, the blast furnace ironmaking method has the following two prominent problems. First, the coal and coke required for blast furnace ironmaking are used as energy and reducing agents to assist in the reduction and melting of iron ore (the carbon element fuel ratio of the national blast furnace ironmaking process in 2022 is 527.09 kg / t), which leads to a high carbon emission per ton of iron in the molten iron product. At present, the carbon emissions of the long process per ton of steel are about 1.8-2.5 tons. It is the process with the largest CO2 emissions in the steel production process, accounting for about 70%-90% of the total CO2 emissions of the entire steel production. Therefore, in order to respond to global climate change and achieve the policy goals of "carbon neutrality and carbon peak" in the steel industry, the development of low-carbon smelting technology, especially for the blast furnace process with the largest CO2 emissions, has become an important path to achieve substantial emission reductions in the steel manufacturing process.

[0004] Currently, coke is the primary fuel, backbone, and reducing agent used in blast furnace iron production. Coke is produced by dry distilling coal at temperatures of approximately 1000°C. The coking process produces a large amount of harmful chemical pollutants and is costly. To ensure the air permeability of the blast furnace, the coke fragments and coke dicing produced during the coking process are generally not allowed to enter the blast furnace directly.

[0005] Reducing the coke ratio in blast furnaces is key to energy conservation. Traditional blast furnace smelting primarily involves injecting pulverized coal (PFC) into the blast furnace to partially replace coke. However, large amounts of PFC can negatively impact blast furnace performance. For example, PFC undergoes a series of physical and chemical changes within the blast furnace, including heating, decomposition, combustion, and slagging. This complicates reactions within the raceway and makes operation difficult. Increasing the amount of PFC increases the soft melting zone, severely damaging the coke, limiting PFC quality. Increased levels of unburned PFC further deteriorate the working conditions of the soft melting and slagging zones. Furthermore, large amounts of oxygen-rich PFC can cause the blast furnace to be "cold at the top and hot at the bottom."

[0006] Blast furnace smelting also produces blast furnace top gas, which contains CO and CO₂. To recover the CO from the gas, the gas is injected back into the blast furnace. However, before this process can be completed, the CO₂ must be removed from the gas, which is a challenge.

[0007] Hydrogen boasts the advantages of being green, renewable, highly reducible, and clean, pollution-free. Large-scale use of hydrogen as a fuel and reducing agent in metallurgical processes, replacing carbon with water as the reaction product, can fundamentally reduce carbon emissions compared to traditional carbon metallurgy, achieving the goal of clean production.

[0008] Compared with coal, the H2 / CO ratio in the gasification products of waste plastics is much greater than that when pulverized coal is injected, which is more conducive to the high-temperature reduction of iron oxides. However, the direct injection of plastics into blast furnaces is still in the research stage.

[0009] Biomass pellets, another clean and renewable energy source, possess a high calorific value and are carbon neutral. Injecting them into a blast furnace can offset the heat loss in the lower furnace caused by hydrogen, conserve coal resources, reduce the potential for unburned coal to affect blast furnace permeability, and eliminate excess carbon emissions. However, existing traditional tuyere systems cannot achieve mixed injection of gas and biomass pellets.

[0010] Summary of the Invention

[0011] In view of the above-mentioned defects of the prior art, the present invention provides a steel smelting system based on hydrogen-rich reducing gas injection, comprising a blast furnace and a hydrogen-rich reducing gas prefabrication furnace; hydrogen-rich reducing gas and pure hydrogen from the hydrogen-rich reducing gas prefabrication furnace are injected into the blast furnace; the generated blast furnace top gas is circulated into the hydrogen-rich reducing gas prefabrication furnace for decarbonization; the material column in the hydrogen-rich reducing gas prefabrication furnace includes coke, biomass particles and waste plastic particles, and dry coal powder and pure oxygen are also injected into the hydrogen-rich reducing gas prefabrication furnace to prepare hydrogen-rich reducing gas.

[0012] Furthermore, the blast furnace includes an ironmaking blast furnace, a pig iron casting blast furnace, and a ferroalloy blast furnace.

[0013] Furthermore, the dry pulverized coal is hydrogen-rich pulverized coal.

[0014] Furthermore, pure hydrogen is green electricity produced through blast furnace and converter gas power generation, photovoltaic, wind, nuclear, hydropower and grid valley electricity, produced by water electrolysis, or produced by reforming and purifying hydrogen-rich gases such as coke oven gas and natural gas.

[0015] Furthermore, the molten iron produced in the blast furnace is supplied to primary steelmaking furnaces including converters and electric arc furnaces to produce carbon structural steel, alloy structural steel, low-alloy high-strength structural steel, carbon tool steel, alloy tool steel, high-speed tool steel, high-carbon steel castings, high-carbon iron castings and stainless steel, as well as special-purpose steels with the addition of specific alloying elements including rare earths; the special-purpose steels include marine corrosion-resistant steel; and profiles, plates, pipes, bars and wires rolled from the above-mentioned steels.

[0016] Furthermore, a double-cylinder spiral distributor is used at the feed inlet of the hydrogen-rich reducing gas prefabrication furnace, including an outer cylinder; the upper part of the outer cylinder is a spiral material channel, and the lower part is an inner cylinder; the inner cylinder extends downward from under the outer cylinder, and the length of the inner cylinder is set so that its outlet is immersed in the material column in the hydrogen-rich reducing gas prefabrication furnace, and a plurality of pressure equalizing holes are provided in the part of the inner cylinder extending beyond the outer cylinder to balance the pressure in the inner cylinder and the furnace.

[0017] The present invention also provides a steel smelting method based on hydrogen-rich reducing gas injection, comprising the steps of:

[0018] (1) adding chopped coke, biomass particles and waste plastic particles into a hydrogen-rich reducing gas prefabrication furnace, and simultaneously spraying dry coal powder and pure oxygen into the furnace to burn and produce hydrogen-rich reducing gas;

[0019] (2) mixing the hydrogen-rich reducing gas from the hydrogen-rich reducing gas prefabrication furnace with pure hydrogen and spraying the mixture into the blast furnace;

[0020] (3) introducing the generated blast furnace top gas into a hydrogen-rich reducing gas prefabrication furnace for decarburization;

[0021] (4) simultaneously injecting pure oxygen into the blast furnace;

[0022] (5) The molten iron produced in the blast furnace is supplied to primary steelmaking furnaces including converters and electric arc furnaces to produce carbon structural steel, alloy structural steel, low alloy high strength structural steel, carbon tool steel, alloy tool steel, high speed tool steel, high carbon steel castings, high carbon iron castings and stainless steel.

[0023] Furthermore, the dry pulverized coal is hydrogen-rich pulverized coal.

[0024] Furthermore, pure hydrogen is green electricity produced through blast furnace and converter gas power generation, photovoltaic, wind, nuclear, hydropower and grid valley electricity, produced by water electrolysis, or produced by reforming and purifying hydrogen-rich gases such as coke oven gas and natural gas.

[0025] Furthermore, a double-cylinder spiral distributor is used at the feed inlet of the hydrogen-rich reducing gas prefabrication furnace, including an outer cylinder; the upper part of the outer cylinder is a spiral material channel, and the lower part is an inner cylinder; the inner cylinder extends downward from below the outer cylinder, and the length of the inner cylinder is set so that its outlet is immersed in the material column in the hydrogen-rich reducing gas prefabrication furnace, and at the same time, a plurality of pressure equalizing holes are provided on the part of the inner cylinder extending beyond the outer cylinder to balance the pressure in the inner cylinder and the furnace; the mixture of chopped coke, biomass particles and waste plastic particles enters the spiral material channel from above, and in the process of falling along the spiral material channel, due to the high density of chopped coke, its movement trajectory is closer to the outer cylinder under the action of inertia, while the biomass particles and waste plastic particles have low density and their movement trajectory is closer to the inner cylinder; in this way, after passing through the spiral material channel, most of the chopped coke enters the furnace through the shorter outer cylinder and participates in the reaction in the furnace earlier, while most of the biomass particles and waste plastic particles enter the furnace through the longer inner cylinder and participate in the reaction in the furnace later.

[0026] The present invention adopts a hydrogen-rich reducing gas prefabrication furnace, which can prefabricate resources such as coal powder, coke, biomass particles and waste plastic particles that are not suitable for direct entry into the blast furnace but are beneficial to reducing the energy consumption of the blast furnace into hydrogen-rich reducing gas, which can then be sprayed into the blast furnace together with hydrogen. Among them, prefabricating coal powder into hydrogen-rich reducing gas can eliminate the adverse effects of coal injection on the blast furnace condition; prefabricating coke, biomass particles and waste plastic particles into hydrogen-rich reducing gas can make the resources fully utilized and recycled. By introducing blast furnace gas into the hydrogen-rich reducing gas prefabrication furnace, the decarbonization of blast furnace gas can be conveniently achieved. More importantly, the comprehensive treatment of the above-mentioned various resources by the hydrogen-rich reducing gas prefabrication furnace is uniformly converted into hydrogen-rich reducing gas, which can be achieved when mixed with pure hydrogen in the subsequent injection. The ratio of CO and H2 can be dynamically adjusted by the control system according to the changes in the components in the hydrogen-rich reducing gas, thereby achieving control of the blast furnace reducing atmosphere and heat, thereby controlling the furnace ore in a replaceable manner. In summary, through the unified recycling, conversion, and utilization of resources, this invention reduces blast furnace energy consumption, thereby reducing carbon emissions from steelmaking. The present invention also provides a twin-tube spiral distributor that can equalize the consumption rates of faster-burning biomass and waste plastic particles with slower-burning coke. This allows for more uniform distribution of raw materials within the furnace column and a more balanced temperature within the furnace during the pre-production of hydrogen-rich reducing gas.

[0027] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic diagram of a steelmaking system based on hydrogen-rich reducing gas injection in a preferred embodiment of the present invention;

[0029] FIG2 is a schematic diagram of a hydrogen-rich reducing gas prefabrication furnace in a preferred embodiment of the present invention;

[0030] FIG3 is a schematic diagram of a double-tube spiral distributor in a preferred embodiment of the present invention;

[0031] FIG4 is a schematic diagram of a hydrogen-rich reducing gas prefabrication furnace using the double-tube spiral distributor in FIG3 . DETAILED DESCRIPTION

[0032] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0033] A preferred embodiment of the present invention utilizes a hydrogen-rich reducing gas injection-based steelmaking system, as shown in Figure 1. The system comprises a blast furnace 2 and a hydrogen-rich reducing gas pre-making furnace 1. Hydrogen-rich reducing gas from the hydrogen-rich reducing gas pre-making furnace 1, hydrogen obtained through green electricity electrolysis, and pure oxygen are injected into the blast furnace 2 to smelt molten iron. The molten iron produced in the blast furnace 2 then enters the steelmaking process and is supplied to primary steelmaking furnaces such as converters and electric arc furnaces for the production of carbon structural steel, alloy structural steel, low-alloy high-strength structural steel, carbon tool steel, alloy tool steel, high-speed tool steel, high-carbon steel castings, high-carbon iron castings, and stainless steel.

[0034] To preform hydrogen-rich reducing gas, diced coke, biomass pellets, and waste plastic pellets are added from the top of the hydrogen-rich reducing gas preformation furnace 1. Dry coal powder and industrial pure oxygen are sprayed from the furnace body of the hydrogen-rich reducing gas preformation furnace 1. Simultaneously, blast furnace gas from blast furnace 2 is also introduced into the hydrogen-rich reducing gas preformation furnace 2. The dry coal powder is preferably hydrogen-rich coal powder.

[0035] A hydrogen-rich reducing gas prefabrication furnace 1 in a preferred embodiment of the present invention is shown in FIG2 . The lower portion of the furnace body is ash 13, and the middle portion is coke 11 and biomass particles and waste plastic particles 12. Coal powder and industrial pure oxygen are simultaneously injected into the furnace body for combustion, generating hydrogen-rich reducing gases such as CO and H2, which are discharged from the upper portion of the furnace body of the hydrogen-rich reducing gas prefabrication furnace 1 and injected into the blast furnace 2.

[0036] The CO2 in the blast furnace gas introduced into the hydrogen-rich reducing gas prefabrication furnace 1 reacts with the coke in the furnace and is reduced to CO.

[0037] The present invention adopts a hydrogen-rich reducing gas prefabrication furnace, which can prefabricate resources such as coal powder, coke, biomass particles and waste plastic particles that are not suitable for direct entry into the blast furnace but are beneficial to reducing the energy consumption of the blast furnace into hydrogen-rich reducing gas, which can then be sprayed into the blast furnace together with hydrogen. Among them, prefabricating coal powder into hydrogen-rich reducing gas can eliminate the adverse effects of coal injection on the blast furnace condition; prefabricating coke, biomass particles and waste plastic particles into hydrogen-rich reducing gas can make the resources fully utilized and recycled. By introducing blast furnace gas into the hydrogen-rich reducing gas prefabrication furnace, the decarbonization of blast furnace gas can be conveniently achieved. More importantly, the comprehensive treatment of the above-mentioned various resources by the hydrogen-rich reducing gas prefabrication furnace is uniformly converted into hydrogen-rich reducing gas, which can be achieved when mixed with pure hydrogen in the subsequent injection. The ratio of CO and H2 can be dynamically adjusted by the control system according to the changes in the components in the hydrogen-rich reducing gas, thereby achieving control of the blast furnace reducing atmosphere and heat, thereby controlling the furnace ore in a replaceable manner.

[0038] Compared with diced coke, biomass particles and waste plastic particles have a lower density and burn faster. If the three are evenly distributed, it is easy to cause diced coke to accumulate in the material column in the hydrogen-rich reducing gas prefabrication furnace, resulting in uneven temperature inside the furnace, causing fluctuations in furnace conditions, and even safety accidents. In a further embodiment of the present invention as shown in Figures 4 and 5, a double-cylinder spiral distributor is used at the feed port of the hydrogen-rich reducing gas prefabrication furnace 1, including an outer cylinder 2. The upper part of the outer cylinder 2 is a spiral material channel 3, and the lower part is an inner cylinder 4. The inner cylinder 4 extends downward from under the outer cylinder 2, and its length makes its outlet immersed in the material column in the hydrogen-rich reducing gas prefabrication furnace. A plurality of pressure-equalizing holes 5 are provided on the portion of the inner cylinder 4 extending beyond the outer cylinder 2 to balance the pressure in the inner cylinder 4 and the furnace to avoid poor material discharge. The mixture of chopped coke, biomass particles, and waste plastic particles in the inner barrel 4 enters the spiral channel 3 from above. As it descends along the spiral channel, the chopped coke, due to its high density, moves closer to the outer barrel due to inertia, while the biomass particles and waste plastic particles, due to their low density, move closer to the inner barrel. Thus, after passing through the spiral channel, the majority of the chopped coke enters the furnace through the shorter outer barrel and participates in the furnace reaction earlier, while the majority of the biomass particles and waste plastic particles enter the furnace through the longer inner barrel. The outlet of the inner barrel is submerged in the material column, and as the material column is consumed, they naturally descend into the material column and participate in the furnace reaction later. This ensures that although they enter the furnace simultaneously, the different starting times of their participation in the reaction allow the consumption rates of the faster-burning biomass particles and waste plastic particles and the slower-burning chopped coke to converge. This ensures a more uniform distribution of raw materials within the furnace column and a more balanced temperature within the furnace during the pre-production of hydrogen-rich reducing gas.

[0039] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A steel smelting system based on hydrogen-rich reducing gas injection, characterized in that: It includes a blast furnace and a hydrogen-rich reducing gas prefabrication furnace; hydrogen-rich reducing gas and pure hydrogen from the hydrogen-rich reducing gas prefabrication furnace are sprayed into the blast furnace; the generated blast furnace top gas is circulated into the hydrogen-rich reducing gas prefabrication furnace for decarbonization; the material column in the hydrogen-rich reducing gas prefabrication furnace includes coke, biomass particles and waste plastic particles, and dry coal powder and pure oxygen are also sprayed into the hydrogen-rich reducing gas prefabrication furnace to prepare hydrogen-rich reducing gas.

2. The steel smelting system based on hydrogen-rich reducing gas injection according to claim 1, wherein: Blast furnaces include iron-making blast furnaces, blast furnaces for casting pig iron, and blast furnaces for ferroalloys.

3. The steel smelting system based on hydrogen-rich reducing gas injection according to claim 1, wherein: The dry pulverized coal is hydrogen-rich pulverized coal.

4. The steel smelting system based on hydrogen-rich reducing gas injection according to claim 1, wherein: Pure hydrogen is green electricity produced through blast furnace, converter gas power generation, photovoltaic, wind, nuclear, hydropower and grid valley electricity. It is produced by electrolysis of water, or by reforming and purifying hydrogen-rich gases such as coke oven gas and natural gas.

5. The steel smelting system based on hydrogen-rich reducing gas injection according to claim 1, wherein: The molten iron produced in the blast furnace is supplied to primary steelmaking furnaces including converters and electric arc furnaces to produce carbon structural steel, alloy structural steel, low-alloy high-strength structural steel, carbon tool steel, alloy tool steel, high-speed tool steel, high-carbon steel castings, high-carbon iron castings and stainless steel, as well as special-purpose steels with specific alloy elements including rare earths; the special-purpose steels include marine corrosion-resistant steel; and profiles, plates, pipes, bars and wires rolled from the above-mentioned steels.

6. The steel smelting system based on hydrogen-rich reducing gas injection according to claim 1, wherein: A double-cylinder spiral distributor is used at the feed inlet of the hydrogen-rich reducing gas prefabrication furnace, including an outer cylinder; the upper part of the outer cylinder is a spiral material channel, and the lower part is an inner cylinder; the inner cylinder extends downward from under the outer cylinder, and the length of the inner cylinder is set so that its outlet can be immersed in the material column in the hydrogen-rich reducing gas prefabrication furnace, and at the same time, a plurality of pressure equalizing holes are provided in the part of the inner cylinder extending beyond the outer cylinder to balance the pressure in the inner cylinder and the furnace.

7. A steel smelting method based on hydrogen-rich reducing gas injection, characterized in that: Includes steps: (1) adding chopped coke, biomass particles and waste plastic particles into a hydrogen-rich reducing gas prefabrication furnace, and simultaneously spraying dry coal powder and pure oxygen into the furnace to burn and prepare hydrogen-rich reducing gas; (2) mixing the hydrogen-rich reducing gas from the hydrogen-rich reducing gas prefabrication furnace with pure hydrogen and spraying the mixture into the blast furnace; (3) introducing the generated blast furnace top gas into a hydrogen-rich reducing gas prefabrication furnace for decarburization; (4) simultaneously injecting pure oxygen into the blast furnace; (5) The molten iron produced in the blast furnace is supplied to primary steelmaking furnaces including converters and electric arc furnaces to produce carbon structural steel, alloy structural steel, low alloy high strength structural steel, carbon tool steel, alloy tool steel, high speed tool steel, high carbon steel castings, high carbon iron castings and stainless steel.

8. The iron and steel smelting method based on hydrogen-rich reducing gas injection according to claim 7, wherein: The dry pulverized coal is hydrogen-rich pulverized coal.

9. The steelmaking method based on hydrogen-rich reducing gas injection according to claim 7, wherein: Pure hydrogen is green electricity produced through blast furnace, converter gas power generation, photovoltaic, wind, nuclear, hydropower and grid valley electricity. It is produced by electrolysis of water, or by reforming and purifying hydrogen-rich gases such as coke oven gas and natural gas.

10. The iron and steel smelting method based on hydrogen-rich reducing gas injection according to claim 7, wherein: A double-cylinder spiral distributor is used at the inlet of the hydrogen-rich reducing gas prefabrication furnace, which includes an outer cylinder; the upper part of the outer cylinder is a spiral material channel, and the lower part is an inner cylinder; the inner cylinder extends downward from below the outer cylinder, and the length of the inner cylinder is set so that its outlet can be immersed in the material column in the hydrogen-rich reducing gas prefabrication furnace, and at the same time, a plurality of pressure equalizing holes are set in the part where the inner cylinder extends beyond the outer cylinder to balance the pressure in the inner cylinder and the furnace; the mixture of chopped coke, biomass particles and waste plastic particles enters the spiral material channel from above, and in the process of falling along the spiral material channel, due to the large density of chopped coke, its movement trajectory is closer to the outer cylinder under the action of inertia, while the biomass particles and waste plastic particles have small densities and their movement trajectories are closer to the inner cylinder; in this way, after passing through the spiral material channel, most of the chopped coke enters the furnace through the shorter outer cylinder and participates in the reaction in the furnace earlier, and most of the biomass particles and waste plastic particles enter the furnace through the longer inner cylinder and participate in the reaction in the furnace later.

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