Hydrogen-rich or carbon monoxide and carbon-containing material external heating shaft furnace direct reduction iron system and method

Abstract

The invention relates to a system and a method for reducing iron ore by using external hot iron ore and carbon-containing materials by adding normal-temperature hydrogen and carbon monoxide from the upper part of a cooling section at the bottom of a shaft furnace. In the system, an iron ore and carbon-containing material distribution bin is arranged at the top of a shaft furnace; the shaft furnace structure is formed by arranging combustion chambers and reduction chambers at intervals; the combustion chamber provides heat by adopting an efficient combustion heating technology; the combustors are evenly distributed on the two sides of the combustion chamber. The upper section of the reduction chamber is an iron ore and carbon-containing material preheating section, the middle section is an iron ore reduction section, and the lower section is a reduced iron heat recovery section; the bottom of the shaft furnace is a reduced iron cooling system; a reduction tail gas collecting system is arranged at the top of the shaft furnace; smoke exhaust systems are arranged on the two sides of the shaft furnace combustion chamber.

Description

Technical Field

[0001] The invention relates to a non-blast furnace ironmaking technology in the metallurgical industry, and in particular to a system and method for direct iron reduction in a hydrogen-rich or carbon monoxide+carbon-containing material externally heated vertical furnace. Background Art

[0002] Non-blast furnace direct reduced iron does not require coke or high-temperature melting, and the product has few harmful impurities. It is a steelmaking raw material that replaces and is superior to scrap steel, and can dilute the impurity elements in scrap steel. Compared with blast furnace ironmaking, direct reduced iron has a much lower emission of carbon dioxide, nitrogen oxides, and sulfides, and is a technology urgently needed by the steel industry. In 2022, the Ministry of Science and Technology included the research and development and demonstration of hydrogen-rich gas iron reduction technology in the "Key Project".

[0003] At present, the world's non-blast furnace ironmaking technologies mainly include: 1. Tunnel kiln process: Since the process is relatively simple, low in technical content, raw materials, reducing agents and fuels are easy to solve, the process is practical, the initial investment is small, and it is suitable for small-scale production. It is a metallurgical reduction production process commonly used in the powder metallurgy industry. However, the tunnel kiln method has small single-machine capacity, low degree of automation, high labor intensity, high energy consumption, and great environmental pollution.

[0004] 2. Rotary kiln process: The most commonly used coal-based reduction technology in the world is rotary kiln equipment, that is, the reduction process of adding oxidized pellets or high-grade lump ore to the rotary kiln. India has more than 300 rotary kiln production lines with an annual output of 20,000 to 150,000 tons. This method has low thermal efficiency, small single-line production capacity, high coal consumption, and large carbon emissions, and is not suitable for large-scale promotion.

[0005] 3. Coal-based vertical furnace process: Coal-based vertical furnaces can expand their production and have scale advantages. The indicators of some pilot plants can meet the steelmaking standards. Many companies are conducting industrial trials on coal-based vertical furnaces, but their energy consumption is still higher than that of gas-based vertical furnaces.

[0006] 4. Gas-based vertical furnace: Gas-based vertical furnace direct reduction is the mainstream direct reduction process in the world today. The proportion of sponge iron produced by gas-based vertical furnace direct reduction process in the world is ≥75%. The key to the application of gas-based vertical furnace technology lies in the acquisition of low-cost gas sources, and my country lacks natural gas resources. In regions and enterprises where non-coking coal, natural gas and coke oven gas are relatively cheap, whether the cost of hydrogen-rich synthesis gas can be significantly reduced determines whether a large-scale vertical furnace direct reduction and coal-to-gas cokeless ironmaking combined process can be built.

[0007] 5. Smelting reduction process: The smelting reduction ironmaking process eliminates the two steps of sintering and coking, but its overall energy consumption and carbon emissions have no obvious advantages compared with blast furnace ironmaking. Summary of the invention

[0008] The present invention relates to an iron-making system and method, and in particular to a system and method for directly reducing iron by using an external heating vertical furnace with hydrogen-rich or carbon monoxide + carbon-containing materials.

[0009] The object of the present invention is to provide a non-blast furnace ironmaking system and method with low investment, low energy consumption, low pollution, easy operation, high degree of automation, reliable operation and convenient maintenance.

[0010] To achieve the above-mentioned purpose, the present invention is implemented through the following technical scheme: a system and method for direct reduction of iron using an externally heated vertical furnace with hydrogen-rich or carbon monoxide + carbon-containing materials, which adopts an externally heated vertical direct reduction furnace mainly composed of a material distribution bin installed on the furnace top, a reduction tail gas collection system, a furnace shell, a combustion chamber, a reduction chamber, a high-efficiency and energy-saving combustion heating system, a flue gas emission system, a reduced iron cooling system, and an adjustable special device for discharging.

[0011] The externally heated vertical direct reduction furnace of the present invention has a reduction chamber whose internal space height-to-width ratio is 17-32:1; the upper section of the reduction chamber is an iron ore and carbonaceous material preheating section, which is 20% of the height of the tank body; the middle section is an iron ore reduction section, which is 50% of the height of the tank body; the lower section is a reduced iron heat recovery section, which is 10% of the height of the tank body; and the bottom of the vertical furnace is a reduced iron cooling system, which is 20% of the height of the tank body.

[0012] Furthermore, the reduced iron heat recovery section is a preheating chamber in which hydrogen and carbon monoxide are heated by the reduced iron.

[0013] The externally heated direct reduction furnace described in the present invention has a heat storage wall between the combustion chamber and the reduction chamber, which is integrally rammed with silicon carbide, high thermal conductivity silicon or high alumina material with good air tightness, high heat transfer efficiency and strong overall firmness. The heat required for the reduction of the iron ore is supplied by the combustion chamber through the heat transfer wall.

[0014] The externally heated direct reduction furnace of the present invention may have only one reduction chamber and two groups of combustion chambers; or it may be constructed into a structure having multiple reduction chambers and multiple (one more than the number of reduction chambers) combustion chambers in order to expand its production capacity.

[0015] The externally heated direct reduction furnace of the present invention has a reduction tail gas collection system arranged on the top of the vertical furnace, which can collect the reduction tail gas in the reduction chamber and send it to cooling and separation through a collection pipeline. After cooling and separation, part of the reduction tail gas enters the combustion chamber as fuel gas, part enters the reduction chamber as reducing agent, and the remaining part is comprehensively utilized.

[0016] The externally heated direct reduction furnace of the present invention has an adjustable discharge device which is mainly composed of a group of variable speed rotating blades, a cam group and a mechanical sealing system.

[0017] Iron ore and carbon-containing materials enter the reduction chamber from the top bunker of the vertical furnace, exchange heat with the tail gas produced by the reduced iron to recover heat, and gradually move downward by natural gravity. They are heated by the heat transferred by the combustion chamber through the heat transfer wall. Under the action of the reducing agent and catalyst, the iron ore is reduced to metallic iron. The descending high-temperature reduced iron exchanges heat with the ascending carbon monoxide and hydrogen in countercurrent to cool down, and then goes down through the cooling section to about 100°C before being discharged.

[0018] The above structure is used in the external heat direct reduction iron vertical furnace, which will significantly increase the speed of iron reduction. The intermediate reactions of the vertical furnace iron reduction are mainly: C+CO2=2CO, Fe3O4+CO=3FeO+CO2, FeO+CO=Fe+CO2, 3H2+Fe2O3=2Fe+3H2O. The reaction speed depends on the concentration of CO and H2. Now, rich hydrogen and carbon monoxide (H2 and CO) are added in the heat recovery section of iron reduction, which can be directly used to reduce iron oxide, thereby increasing the speed of generating CO2. Under the action of fixed carbon, the generation of CO is further accelerated, and then acts on iron oxide, which speeds up the reaction speed of iron reduction and improves production efficiency; strengthens the degree of reaction of iron reduction and improves the metal conversion rate of iron reduction.

[0019] The beneficial effects of the present invention are: The present invention adopts a high furnace body structure, and adds hydrogen and carbon monoxide in the heat recovery section of the reduced iron for secondary reduction, with a high reduction rate and uniform reduction, and stable product quality; it strengthens the counterflow of the charge and the hot air flow in the furnace, increases the temperature of the preheating section, reduces the preheating time, and improves production efficiency.

[0020] The present invention effectively solves the problems of feeding and discharging in the traditional tunnel kiln process by arranging a material distribution bin and an adjustable special discharging device, thereby improving the degree of automation and continuity of production.

[0021] The furnace of the present invention has a simple structure, occupies a small space, is reliable in operation, has a low cost, requires little investment, and is convenient for early construction work and later maintenance and management work.

[0022] The present invention mixes the reducing agent and the catalyst in the pellets to provide a reduction contact point. The catalyst releases heat energy in the pellets and provides an oxygen-deficient reducing atmosphere to accelerate the reduction reaction.

[0023] The reduced iron heat recovery section and high-efficiency burner are set up to make heat recovery more complete, reduce energy consumption, increase thermal efficiency and reduce operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a schematic flow chart of a system and method for direct reduction of iron in a hydrogen-rich or carbon monoxide + carbon-containing material externally heated vertical furnace. DETAILED DESCRIPTION

[0025] The technical scheme in the embodiment of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described examples 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.

[0026] like Figure 1 As shown, a system and method for direct reduction of iron in a hydrogen-rich or carbon monoxide + carbon-containing material external heating vertical furnace comprises the following steps: S1. Processing of raw materials: stirring, sieving and drying the carbonaceous material for standby use; drying and sieving the iron ore for standby use; or granulating the iron ore powder and the catalyst for standby use; stirring the catalyst for standby use; S2. Mixing raw materials: The processed carbonaceous materials, iron ore and catalyst are stirred and fully mixed, and then made into pellets; S3. Feeding: The raw materials are placed into the tank through the material distribution bin arranged at the top of the vertical furnace; S4. Perform reduction reaction: heat is recovered by heat exchange with tail gas generated by reduced iron in the preheating section, and the raw material is gradually moved downward by natural gravity after being heated. In the reduction section, the heat transferred by the combustion chamber through the heat transfer wall is heated, and a reduction reaction is performed. Hydrogen and carbon monoxide enter the reduced iron heat recovery section, and heat is exchanged with the high-temperature reduced iron to complete the temperature rise. The raw material undergoes a secondary reduction reaction in the reduced iron heat recovery section; S5. Discharging: After the raw materials are cooled to about 100°C through the reduced iron cooling system, they are discharged through an adjustable special discharging device for storage or subsequent processing.

[0027] The carbon-containing materials described in the present invention include, but are not limited to, anthracite, long flame coal, lignite, coal slime, biomass and its carbonized products, carbon-containing organic waste, petroleum coke, coke powder, etc.

[0028] The catalyst described in the present invention is a mixture containing one or more of calcium, magnesium, sodium, potassium, nickel, titanium, zinc, manganese and the like.

[0029] The hydrogen and carbon monoxide described in the present invention can be a mixed gas or a single gas in any proportion.

[0030] Preferably, the iron content of the iron ore is 28-72%, the reduction temperature is 900-1200° C., and the reduction pressure is normal pressure.

[0031] Preferably, the content of hydrogen-rich and carbon monoxide gas is greater than 60-80%, and the content of water and carbon dioxide is less than 8%.

[0032] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Rich hydrogen and carbon monoxide enter the reduction system from the bottom of the external heat vertical furnace reduction chamber, including an adjustable discharge device, a reduced iron cooling section, a hydrogen and carbon monoxide inlet preheating section, a reduction section, a reduced tail gas heat recovery section and a high-efficiency energy-saving combustion heating system; The adjustable discharging device is mainly composed of a set of variable speed rotating blades, a cam set and a mechanical sealing system; The hydrogen and carbon monoxide preheating section is located from the upper part of the cooling section to the reduction section; The reduction section is a chamber where the iron ore reacts with the reducing agent; The reduction tail gas preheating section is a preheating chamber where cold iron ore and carbonaceous materials are heated by the reduction tail gas; The combustion chamber and the reduction chamber are isolated by high temperature resistant materials.

2. The hydrogen and carbon monoxide required by claim 1 can be a mixed gas or a single gas in any proportion.

3. According to claim 1, the inlet temperature of hydrogen and carbon monoxide is 20-80°C, which is used to recover the heat of the reduced iron at the furnace bottom outlet of 900-1200°C.

4. The inlet temperature of hydrogen and carbon monoxide required by right 1 is 20-80°C, which is used to recover the heat of the reduced iron at 900-1200°C at the furnace bottom outlet.

5. The carbon-containing materials claimed in claim 1 include but are not limited to anthracite, long flame coal, lignite, semi-coke, coal slime, biomass and its carbide, carbon-containing organic waste, petroleum coke, coke powder, etc.

6. The catalyst according to claim 1 is a mixture containing one or more of calcium, magnesium, sodium, potassium, nickel, titanium, zinc, manganese, etc.

7. The material used to isolate the combustion chamber and the reduction chamber according to claim 1 is silicon carbide, high thermal conductivity silicon or high aluminum.

8. The heat required for the reduction of the iron ore according to claim 1 is supplied by the combustion chamber through the heat transfer wall.

9. A system according to claims 1 to 8, a method for reducing iron using an externally heated vertical furnace with rich hydrogen and carbon monoxide + carbon-containing materials, characterized in that: Iron ore and carbon-containing materials enter the reduction chamber from the top bunker of the vertical furnace, exchange heat with the tail gas produced by the reduced iron to recover heat, and gradually move downward by natural gravity. They are heated by the heat transferred by the combustion chamber through the heat transfer wall. Under the action of the reducing agent and catalyst, the iron ore is reduced to metallic iron. The descending high-temperature reduced iron exchanges heat with the ascending carbon monoxide and hydrogen in countercurrent to cool down, and then passes through the cooling section to a temperature of about 100°C before being discharged.

10. The method according to claim 9, characterized in that The hydrogen-rich + carbon monoxide gas content is 60~80%, and the water + carbon dioxide is less than 8%.

11. The method according to claim 9, characterized in that The heat required for the reduction of iron ore is transferred to the iron ore and carbon-containing materials through the combustion chamber wall at 1100-1350°C.

12. The method according to claim 9, characterized in that The reduction temperature is 900-1200°C.

13. The method according to claim 9, characterized in that The iron content of iron ore is 28-72%.

14. The method according to claim 9, characterized in that The pressure in the reduction chamber is normal pressure.

15. The method according to claim 9, characterized in that The outlet temperature of the reduced tail gas is less than 200°C.

16. The method according to claim 9, characterized in that The exhaust temperature of the heated flue gas is less than 180°C.

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