Method for producing low-sulfur molten iron by spraying hydrogen into blast furnace

Abstract

The invention discloses a method for producing low-sulfur molten iron by spraying hydrogen into a blast furnace. Firstly, a blast furnace hydrogen-hot air mixed pulse injection device is provided, hot air is introduced into an inner pipe of a coaxial double-channel air inlet pipe, hydrogen-rich gas is introduced into an outer pipe of the coaxial double-channel air inlet pipe, the hot air and the hydrogen-rich gas are mixed in a mixing booster cavity under the action of a dynamic spiral flow deflector, and the mixed gas enters a pulse spray pipe; and injecting into the lower part of the blast furnace or a hearth through the multistage microporous ceramic nozzle in a pulse injection manner by virtue of the pulse electromagnetic valve group. The hydrogen-rich gas can be selected from green hydrogen or chemical byproduct hydrogen, the injection pressure is 0.8-1.2 MPa, the volume ratio of hydrogen to hot air in the mixed gas is (1: 3)-(1: 5), the hot air temperature is 1200-1300 DEG C, the oxygen content is less than or equal to 5%, and the pulse injection parameters are as follows: the frequency is 1-10Hz, the pulse width is 50-200ms, and the duty ratio is 30-80%. And the sprayed hydrogen-rich gas and sulfur in the molten iron form H2S to realize desulfurization. According to the method, the decomposition rate of FeS2 and the migration rate of a sulfur interface can be increased, the hydrogen utilization rate is increased, the energy consumption per ton of iron is reduced, and CO2 emission is reduced.

Description

Technical Field

[0001] The present invention relates to the technical fields of ironmaking and hydrogen technology, and particularly to a method for producing low-sulfur hot metal by injecting hydrogen into a blast furnace. Background Art

[0002] In the process of blast furnace ironmaking, the quality of hot metal, especially the contents of S, P, and Si in hot metal, directly affects the quality of the final steel products in a steel plant. Sulfur is an impurity brought into steel by pig iron and fuel. In the solid state, the solubility of sulfur in iron is extremely small, and it exists in hot metal in the form of FeS and then enters the steel subsequently. Sulfur is a harmful element in most steels. Compounds of sulfur can precipitate between crystal grains, destroying the continuity of the steel and reducing the plasticity of the steel. Secondly, FeS and Fe can form a eutectic with a low melting point (985 °C), which is distributed at the grain boundaries of austenite, reducing the high-temperature properties and hot working process properties of the steel and causing the phenomenon of "hot brittleness". Sulfides are non-metallic inclusions, which will reduce the mechanical properties of the steel and form a hot working fiber structure during the rolling process. Therefore, the content of sulfur in steel should be strictly restricted, which makes reducing the sulfur content in hot metal a key task in the production of high-quality steel.

[0003] Traditional desulfurization of hot metal in a blast furnace mainly reduces the sulfur content in hot metal by optimizing the slag composition and reaction conditions to promote the transfer of sulfur from hot metal to slag. The following methods are mainly used: increasing the slag basicity, optimizing MgO / Al 2 O 3 , and selecting low-sulfur coke. However, too high basicity will lead to a decrease in slag fluidity, and the improvement of sulfur capacity is limited. At the same time, the cost of low-sulfur raw materials is relatively high, and the environmental protection treatment of high-sulfur slag is difficult.

[0004] Therefore, technicians in this field are committed to developing a method for producing low-sulfur hot metal. Summary of the Invention

[0005] To achieve the above object, the present invention provides a method for producing low-sulfur hot metal by injecting hydrogen into a blast furnace, including the following steps:

[0006] (1) Provide a hydrogen-hot air hybrid pulse injection device for a blast furnace. This device first includes a coaxial double-channel air inlet pipe, which includes an inner pipe for passing hot air and an outer pipe for passing hydrogen-rich gas. The inner pipe passes the hot air from the hot blast stove of the blast furnace, while the outer pipe passes the hydrogen-rich gas; the coaxial double-channel air inlet pipe is connected to a mixing and pressurizing chamber. At the entrance of the mixing and pressurizing chamber, a dynamic spiral guide vane is installed on the chamber wall of the mixing and pressurizing chamber through a bearing. The dynamic spiral guide vane rotates under the impact of the high-speed hot air in the inner pipe of the coaxial double-channel air inlet pipe, inhaling the low-speed hydrogen-rich gas in the outer pipe and accelerating it, so that the hot air and the hydrogen-rich gas are mixed in the mixing and pressurizing chamber;

[0007] (2) The mixed hot air and hydrogen-rich gas enter the pulse nozzle. A pulse solenoid valve group is arranged on the pulse nozzle, so that the mixed gas of hot air and hydrogen-rich gas is sprayed into the lower part or the hearth of the blast furnace in the form of pulse injection; the nozzle of the pulse nozzle adopts a multi-stage microporous ceramic nozzle;

[0008] (3) The hydrogen-rich gas sprayed into the blast furnace reacts with sulfur in the hot metal to form H 2 S, completing the desulfurization of hot metal.

[0009] Furthermore, the hydrogen-rich gas is green hydrogen (purity ≥ 99.9%) or by-product hydrogen from chemical industry (H 2 ≥ 95%), and the injection pressure is 0.8 - 1.2 MPa.

[0010] Furthermore, the volume ratio of hydrogen to hot air in the mixed gas is 1:3 - 1:5, the temperature of hot air is 1200 - 1300 °C, and the oxygen content ≤ 5%.

[0011] Furthermore, the pulse injection parameters are: frequency 1 - 10 Hz, pulse width 50 - 200 ms, and duty cycle 30% - 80%.

[0012] Furthermore, the nozzle of the pulse nozzle is of multi-stage microporous ceramic structure, with pore diameter 50 - 200 μm, porosity 40% - 60%, and compressive strength ≥ 200 MPa.

[0013] In the present invention, by injecting hydrogen into the blast furnace, hot metal desulfurization is achieved. Through the mixing of hot air and hydrogen-rich gas, the active oxygen free radicals carried by the hot air and hydrogen act synergistically to increase the decomposition rate of FeS 2 ; Pulse injection (5 - 10 Hz) is used to destroy the local concentration gradient and increase the sulfur interface migration rate. Through the dynamic spiral guide vane, using the self-impulse of the hot air, the hot air velocity in the inner tube is reduced and the hydrogen velocity of the hydrogen in the outer tube is increased, improving the mixing rate and mixing efficiency of hot air and hydrogen in the mixing and pressurizing chamber.

[0014] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the drawings to fully understand the purpose, features and effects of the present invention. Description of the Drawings

[0015] Figure 1 It is the equipment and process diagram in a preferred embodiment of the present invention; Detailed Embodiments

[0016] The following introduces multiple preferred embodiments of the present invention with reference to the accompanying drawings of the specification to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0017] In the accompanying drawings, components with the same structure are denoted by the same numerical reference signs, and components with similar structures or functions everywhere are denoted by similar numerical reference signs. The dimensions and thicknesses of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustration clearer, the thicknesses of some components in the drawings are appropriately exaggerated in some places.

[0018] In view of the limited ability of traditional blast furnaces to reduce coke consumption and control the sulfur content in pig iron while maintaining the reduction conditions inside the blast furnace, the present invention proposes an innovative method, that is, by injecting hydrogen into the blast furnace, using hydrogen as a part of the reducing agent to replace part of the coke and pulverized coal, and at the same time using the reduction effect of hydrogen to promote the conversion of solid-phase sulfides to gas-phase sulfides, thereby obtaining low-sulfur hot metal.

[0019] The technical solution adopted by the present invention is to inject hydrogen-rich gas into the lower part of the blast furnace shaft or the blast furnace hearth. Among them, the hydrogen-rich gas is not just pure hydrogen, but refers to a mixed gas with a relatively high content of hydrogen (H 2 ). Depending on the source and application scenario, the hydrogen-rich gas may also include various types such as coke oven gas, natural gas reforming, and syngas. Green hydrogen (pure hydrogen) or chemical by-product hydrogen (high purity, low impurities) is preferably selected, and coke oven gas or natural gas reformed gas can also be selected considering economic factors.

[0020] When injecting hydrogen-rich gas into the blast furnace, the gas flow rate in the center of the blast furnace will increase, making the central gas flow of the blast furnace more stable. Because a relatively large gas flow must pass through the central burden column, that is, the so-called "active center", to ensure that the center of the blast furnace hearth is conducive to the smooth desulfurization of hot metal. After injecting hydrogen into the blast furnace, the burden descends evenly, the contact area between slag and iron increases, and sulfur is more likely to transfer from hot metal to slag through interfacial reactions.

[0021] Due to different properties of different hydrogen-rich gases, the appropriate injection amounts are also different. Under the condition that the theoretical combustion temperature is 1900 °C, the maximum injection amounts that can be selected for blast furnace coal injection + natural gas, blast furnace coal injection + coke oven gas, and blast furnace coal injection + pure H 2 are 128, 359, and 500 m 3 / t respectively.

[0022] In terms of the selection of the injection position, it is preferred to inject into the blast furnace hearth. If injecting hydrogen-rich gas into the lower part of the blast furnace shaft, the heat of the blast furnace hearth cannot be guaranteed, and the desulfurization reaction will be affected to a certain extent. When injecting into the lower part of the blast furnace shaft, the gas needs to be preheated in advance. Injecting hydrogen-rich gas into the blast furnace hearth can directly generate H 2 S gas and discharge it during the decomposition stage of sulfides, reducing the sulfur entering the slag and hot metal, and the sulfur content of hot metal can be reduced by 10% - 20%.

[0023] The reduction of sulfur already starts in the lump zone. The main sulfur form in the lump zone is solid sulfide (FeS2 , CaS)

[0024] and the organic sulfur in coke mainly undergoes the following reactions:

[0025] Pyrite (FeS 2 ) decomposes (>500 °C):

[0026] FeS 2 + H 2 (g) = FeS + H 2 S(g)

[0027] FeS + H 2 (g) = Fe + H 2 S(g)

[0028] The thiophene sulfur (C 4 H 4 S) in coke cracks at high temperature:

[0029] C 4 H 4 S + H 2 → CH 4 + H 2 S(g) + carbon residue

[0030] At high temperature (>1000 °C), the reaction proceeds forward, and the increase in H 2 concentration promotes the formation of H 2 S.

[0031] In the cohesive zone, the main sulfur forms are liquid sulfur (dissolved in hot metal) and sulfide ions (S 2- dissolved in slag), and the following reactions mainly occur:

[0032] The equilibrium reaction of sulfur migration from hot metal to slag:

[0033] [S]hot metal + (O 2- )slag = (S 2- )slag + [O]hot metal

[0034] In the hearth area, the main sulfur forms are dissolved sulfur [S] in hot metal, S 2- in slag 2 and gaseous H

[0035] S.

[0036] [S] + CaO = CaS + [O]

[0037] H 2 's direct desulfurization effect:

[0038] H 2 + [S] → H 2 S

[0039] In the gas system of the entire furnace area, H 2 Direct reduction reaction of sulfides

[0040] Unremoved H 2 S and COS rise with the gas and will react with calcium oxide (CaO) and ferrous oxide (FeO) in the low-temperature zone, being re-adsorbed by the burden to form calcium sulfide and ferrous sulfide, resulting in the cyclic enrichment of sulfur:

[0041] CaO + H 2 S → CaS + H 2 O

[0042] FeO + H 2 S → FeS + H 2 O

[0043] FeO + COS → FeS + CO 2

[0044] When injecting into the blast furnace, the hydrogen-rich gas enters the blast furnace through the injection channel. When placing it at the lance position, attention should be paid to leaving a certain distance between the hydrogen lance and the pulverized coal lance. If the distance between the two lance positions is too close, the hydrogen-rich gas will interact with the pulverized coal, resulting in a decrease in the combustion rate of the pulverized coal and an increase in the content of unburned pulverized coal, thereby affecting the stable and smooth operation of the blast furnace production.

[0045] After injecting hydrogen-rich gas into the blast furnace, hydrogen desulfurization produces H 2 S gas, which can be directly discharged from the molten steel without residue of inclusions, enabling the smelting of ultra-low sulfur hot metal. Similar to hydrogen decarburization and denitrification, gaseous hydrogen cannot react with sulfur in the hot metal. The fine and dispersed hydrogen bubbles formed by blowing hydrogen not only increase the content of dissolved hydrogen in the steel but also accelerate the reaction of sulfur with locally dissolved hydrogen. The reaction product H 2 S can float up and be removed with the hydrogen bubbles, thereby achieving desulfurization.

[0046] According to the above principle, as shown in the present invention Figure 1 A hydrogen-hot air mixed pulse injection device for a blast furnace is first provided. The device first includes a coaxial double-channel air inlet pipe 10. The coaxial double-channel air inlet pipe 10 includes an inner pipe 4 for passing hot air and an outer pipe 3 for passing hydrogen. The heat pipe 4 is connected to the hot air from the hot blast stove of the blast furnace, and the outer pipe 3 for passing hydrogen is connected to the hydrogen source 5. Among them, the hot blast stove: outputs low-oxygen hot air (O 2 <5%) at 1200 - 1300 °C, with a flow rate of 1000 - 1500 Nm 3 / t of iron; the hydrogen source: green hydrogen (purity ≥ 99.9%) or chemical by-product hydrogen (H 2 ≥ 95%), with a pressure of 0.8 - 1.2 MPa.

[0047] The coaxial dual-channel air inlet pipe 10 is connected to the hybrid supercharging chamber 20. At the inlet of the hybrid supercharging chamber 20, a dynamic spiral deflector 7 is installed on the chamber wall of the hybrid supercharging chamber 20 through a bearing 71. It rotates under the impact of the high-speed hot air in the inner pipe of the coaxial dual-channel air inlet pipe 10, sucks in the low-speed hydrogen from the outer pipe, and accelerates it, so that the hot air and hydrogen are mixed in the hybrid supercharging chamber 20 at a volume ratio of hydrogen to hot air of 1:3 to 1:5 (the oxygen content in the hot air at 1200 °C is <5%), and the uniformity of the mixed gas is ≥98%.

[0048] The mixed hot air and hydrogen enter the pulse nozzle 30. A pulse solenoid valve group 9 is arranged on the pulse nozzle 30. Pulse parameters: frequency 1 - 10 Hz, pulse width 50 - 200 ms, duty cycle 30% - 80%; Flow control: base flow mode (400 - 600 Nm 3 / h) and peak mode (800 - 1200 Nm 3 / h) are switched to force sulfur to desorb from the interface.

[0049] The nozzle 8 of the pulse nozzle 30 adopts a multi-stage microporous ceramic nozzle with a pore diameter of 50 - 200 μm, a porosity of 40% - 60%, and a compressive strength ≥200 MPa.

[0050] Example 1: 3200 m 3 Blast furnace application

[0051] Device parameters

[0052] Spray gun specifications: 6 groups, Φ120 mm, material SiC;

[0053] Gas parameters:

[0054] Green hydrogen: purity 99.9%, injection volume 450 Nm 3 / t of iron;

[0055] Hot air: 1250 °C, 1200 Nm 3 / t of iron, O 2 = 3%;

[0056] Pulse mode: frequency 5 Hz, pulse width 100 ms, duty cycle 50%;

[0057] Nozzle configuration: secondary microporous array (pore diameter 100 μm).

[0058] Operating results

[0059] Molten iron sulfur content: stabilized at 0.022 - 0.028% (traditional process 0.035 - 0.045%);

[0060] Hydrogen utilization rate: 88% (traditional hydrogen injection 70%);

[0061] Energy consumption per ton of iron: reduced by 18% (12% contributed by waste heat recovery and 6% by hydrogen reduction replacing coke);

[0062] Gas composition: H 2 S concentration reduced from 0.8% to 0.5%, and CO 2 emission reduced by 12%.

[0063] Example 2: Dynamically regulate the test for sulfur fluctuation response

[0064] When [S] suddenly increases from 0.025% to 0.042%, the system automatically switches to high-frequency pulse (10 Hz, duty cycle 80%), and [S] drops to 0.028% within 30 minutes;

[0065] Response time: <5 minutes (traditional manual intervention takes 30 minutes).

[0066] Fault tolerance test

[0067] When a single solenoid valve fails, the standby valve is activated within 500 ms, and the flow rate fluctuation <3%;

[0068] Maintenance cycle: 8000 hours (3000 hours for traditional spray guns).

[0069] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. A method for producing low-sulfur molten iron by injecting hydrogen into a blast furnace, characterized in that: The steps include: (1) A blast furnace hydrogen-hot air mixed pulse injection device is provided, the device first comprising a coaxial double-channel air inlet pipe, the coaxial double-channel air inlet pipe comprising an inner pipe for passing hot air and an outer pipe for passing hydrogen-rich gas, the inner pipe is passed with hot air from the hot blast furnace of the blast furnace, and the outer pipe is passed with hydrogen-rich gas; the coaxial double-channel air inlet pipe is connected to a mixing and boosting chamber, a dynamic spiral guide vane mounted on the chamber wall of the mixing and boosting chamber through a bearing is provided at the entrance of the mixing and boosting chamber, the dynamic spiral guide vane rotates under the impact of the high-speed hot air from the inner pipe of the coaxial double-channel air inlet pipe, sucks in the low-speed hydrogen-rich gas from the outer pipe, and accelerates it, so that the hot air and the hydrogen-rich gas are mixed in the mixing and boosting chamber; (2) The mixed hot air and hydrogen-rich gas enter the pulse nozzle, which is provided with a pulse solenoid valve group, so that the mixed gas of the hot air and hydrogen-rich gas is sprayed into the lower part or the furnace of the blast furnace in the form of pulse blowing; the nozzle of the pulse nozzle adopts a multi-stage microporous ceramic nozzle; (3) The hydrogen-rich gas injected into the blast furnace and the sulfur in the molten iron form H2S, completing the desulfurization of the molten iron.

2. The method for producing low-sulfur molten iron by injecting hydrogen into a blast furnace as claimed in claim 1, wherein: The hydrogen-rich gas is green hydrogen or chemical by-product hydrogen, and the injection pressure is 0.8 to 1.2 MPa.

3. The method for producing low-sulfur molten iron by injecting hydrogen into a blast furnace as claimed in claim 1, wherein: The volume ratio of hydrogen to hot air in the mixed gas is 1:3-1:5, the hot air temperature is 1200-1300°C, and the oxygen content is ≤5%.

4. The method for producing low-sulfur molten iron by injecting hydrogen into a blast furnace as claimed in claim 1, wherein: The pulse jet parameters are: frequency 1-10 Hz, pulse width 50-200 ms, duty cycle 30%-80%.

5. The method for producing low-sulfur molten iron by injecting hydrogen into a blast furnace as claimed in claim 1, wherein: The nozzle of the pulse nozzle is a multi-stage microporous ceramic structure with a pore size of 50 to 200 μm, a porosity of 40% to 60%, and a compressive strength of ≥200 MPa.

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