Method for stable operation of blast furnace under hydrogen-rich smelting condition

Abstract

The invention discloses a method for stable operation of a blast furnace under a hydrogen-rich smelting condition, and belongs to the technical field of iron-making blast furnace smelting. The method comprises the following steps: in the coke oven gas injection period of a blast furnace, in order to ensure the production of the blast furnace and the continuous and stable operation of an injection system, the control standard of ammonia in harmful impurities in the coke oven gas is within 10mg / Nm < 3 >, the tar content is within 15mg / Nm < 3 >, and the naphthalene content is within 105mg / Nm < 3 >. The invention aims to provide a method for stable operation of a blast furnace under a hydrogen-rich smelting condition so as to ensure stable operation of a hydrogen-rich injection system of the blast furnace.

Description

Technical Field

[0001] This invention belongs to the field of blast furnace smelting technology, and particularly relates to a method for stable operation of a blast furnace under hydrogen-rich smelting conditions. Background Technology

[0002] Coke oven gas is rich in hydrogen (approximately 55%–60%) and methane (approximately 23%–27%), and can serve as a hydrogen-rich reducing agent to partially replace expensive coke and pulverized coal, thereby reducing fuel costs. Furthermore, since its reduction products are primarily H2O, it plays a positive role in reducing CO2 emissions from blast furnaces. Therefore, injecting coke oven gas into blast furnaces is one of the important technological pathways for the steel industry to transition to a green and low-carbon model, possessing economic, environmental, and strategic significance.

[0003] This invention summarizes and categorizes the main problems encountered by Baogang blast furnace during coke oven gas injection (injection rate of 1000 Nm3 / h, equivalent to 4 Nm3 / tHM of iron). Based on this, it uses energy and mass balance calculations to improve the response direction and control measures for blast furnace production and smelting after increasing the coke oven gas injection rate, thereby laying a good foundation for the stable operation of the blast furnace hydrogen-rich injection system and energy conservation and emission reduction in the blast furnace. Summary of the Invention

[0004] The purpose of this invention is to provide a method for stable operation of a blast furnace under hydrogen-rich smelting conditions, so as to ensure the stable operation of the blast furnace hydrogen-rich injection system.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention discloses a method for stable operation of a blast furnace under hydrogen-rich smelting conditions, comprising, during the injection of coke oven gas into the blast furnace, controlling the ammonia content in the harmful impurities of the coke oven gas to 10 mg / Nm³ to ensure continuous and stable operation of blast furnace production and the injection system. 3 Within 15 mg / Nm³, the tar content is within 15 mg / Nm³. 3 Within 105 mg / Nm 3 Within.

[0007] Furthermore, it also includes a secondary purification system for the tar.

[0008] Furthermore, it also includes the addition of a coke oven gas tar removal system (i.e., a secondary purification system), a naphthalene removal system, and an ammonia removal system, in the order of tar removal, naphthalene removal, and ammonia removal. The tar system (i.e., the secondary purification system), the naphthalene removal system, and the ammonia removal system used are all conventional existing technologies in this field.

[0009] Furthermore, the tar removal system employs tubular electrostatic tar removal technology.

[0010] Furthermore, the naphthalene removal system employs temperature-switching adsorption separation technology.

[0011] Furthermore, the deammoniation system employs phosphoric acid solution absorption technology.

[0012] Furthermore, the injection flow rate is controlled at 10000 Nm. 3 / h, equivalent to 4 Nm of iron 3 / tHM.

[0013] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0014] In order to ensure the continuous and stable operation of blast furnace production and the injection system during the injection of coke oven gas, this invention controls the ammonia content in the harmful impurities of coke oven gas to 10 mg / Nm³. 3 Within 15 mg / Nm³, the tar content is within 15 mg / Nm³. 3 Within 105 mg / Nm 3 Within this range, it can effectively reduce the problems of clogging and corrosion in the injection system pipeline. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings.

[0016] Figure 1 The precipitate is the front end of the flame arrester for coke oven gas injection in a blast furnace of Baogang Steel.

[0017] Figure 2 XRD analysis of the precipitates. Detailed Implementation

[0018] Based on the actual problems encountered in the hydrogen-rich smelting process of blast furnaces and the results of the solutions, this paper provides technical support for long-term blast furnace injection. At the same time, considering that the "green" transformation of the traditional long-process smelting technology in the steel industry is imperative, this paper proposes control standards for stabilizing furnace conditions under the condition of increased hydrogen-rich gas volume in blast furnaces from the perspective of theoretical calculation.

[0019] The invention will be further illustrated below with examples.

[0020] In August 2024, a blast furnace at Baogang Steel began industrial trials of coke oven gas injection. The main purpose was to determine whether any problems such as blockages in the coke oven gas pipelines or blast furnace lances occurred during the trials. Two existing reciprocating piston compressors with a design flow rate of 1600 Nm³ were selected for this test. 3 The flow rate was initially set at 1000-1200 Nm³ / h, but later, due to high equipment failure rates and pipeline blockages, it stabilized at around 1000-1200 Nm³ / h. 3 / h.

[0021] During the test, the following phenomenon occurred: after the spraying equipment was repaired and spraying was resumed, the flow rate of one spray gun returned to normal, with an hourly flow rate of 550-600 Nm³. 3 / h, another flow meter was found to be malfunctioning. After investigation, a large number of transparent granular crystals were found at the front end of the flame arrester. A pungent odor was detected at close range, identified as ammonia. Upon testing, nitric acid was used to dissolve the crystals; the solid disappeared, and the liquid contained a large amount of vapor, indicating the substance was ammonium carbonate or ammonium bicarbonate. This substance slowly decomposes into ammonia and CO2 at room temperature, hence the pungent odor. Simultaneously, it was dissolved in water at room temperature and pressure; the granular crystals completely dissolved after 10 minutes. Specific morphology is as follows... Figure 1 As shown.

[0022] To further verify the accuracy of the judgment, XRD analysis was performed on the sample, and the results confirmed the correctness of the judgment. The analysis results are as follows: Figure 2 As shown.

[0023] The main reason for the shutdown was that during the period from September 3rd to 10th, 2024, the external temperature dropped significantly, and there was no circulating gas in the main and branch pipes of coke oven gas. The original coke oven gas was not discharged, and the branch pipe pressure was 0.7 MPa. However, the coke oven gas needs to be treated with ammonia water and solidified during the purification process of the coking plant to remove harmful impurities. Therefore, the coke oven gas ultimately supplied to users will contain a certain amount of ammonia. At the same time, the coke oven gas contains 2-4% CO2, which will cause ammonium bicarbonate to precipitate under high pressure and sudden temperature drop.

[0024] Therefore, during the injection of coke oven gas into the blast furnace, to ensure the continuous and stable operation of blast furnace production and the injection system, it is necessary to pay attention to the tar and H2S content in the coke oven gas, as well as the naphthalene and ammonia content. It is recommended that the control standard for ammonia in harmful impurities of coke oven gas be 10 mg / Nm³. 3 Within 15 mg / Nm³, the tar content is within 15 mg / Nm³. 3 Within 105 mg / Nm 3 Within this range, it can effectively reduce the problems of clogging and corrosion of the injection system pipeline. Specific data are shown in Table 1.

[0025] Table 1. Control Range of Coke Oven Gas Used in Blast Furnaces

[0026] <![CDATA[Ammonia (mg / Nm 3 )]]> <![CDATA[Naphthalene (mg / Nm 3 )]]> <![CDATA[Tar (mg / Nm 3 )]]> <![CDATA[H2S(mg / Nm 3 )]]> ≤10 ≤105 ≤15 ≤20

[0027] In summary, for enterprises that inject coke oven gas into blast furnaces, if the impurity content is high, a secondary tar purification system should be installed, along with a coke oven gas denaphthalene removal system and a deammoniation system, in the order of tar removal, denaphthalene removal, and deammoniation removal. All equipment should be installed at the front end of the compressor. The tar removal system (i.e., the secondary purification system) adopts tubular electrostatic tar removal technology, the denaphthalene removal system adopts temperature-switching adsorption separation technology, and the deammoniation removal system can adopt phosphoric acid solution absorption technology. None of these are existing technologies in this field.

[0028] Coke oven gas is a combustible gas rich in H2 and CH4, with both accounting for 75%-85% of its composition. Therefore, its combustion characteristics differ significantly from those of carbon-based fuels. Since H2 burns before the tuyeres, the resulting water vapor (H2O) undergoes endothermic decomposition at high temperatures. Similarly, CH4 cracking is an endothermic reaction. Therefore, increasing the injection rate to a certain extent significantly impacts the theoretical combustion temperature control of the blast furnace. Simultaneously, the combustion reactions of H2 and CH4 cause a certain volume expansion, further leading to a substantial increase in the amount of gas in the blast furnace belly. In summary, as the injection rate increases, parameters such as the theoretical combustion temperature and the amount of gas in the blast furnace belly change linearly.

[0029] Based on energy and mass balance calculations, it is estimated that the injection rate of a certain blast furnace at Baogang Steel increased to 10,000 Nm³. 3 When the injection rate is above a certain level, the influence range of the above two parameters and subsequent control measures should be considered. For a blast furnace at Baogang Steel, the theoretical combustion temperature is 2200℃ when no coke oven gas is injected, and the current injection rate is 1100 Nm³. 3 Approximately / h, equivalent to a flow rate of 4.4 Nm³ / ton of iron. 3 / t, the theoretical combustion temperature is 2192℃. Under the current injection conditions, the impact on the theoretical combustion is not significant, but the injection rate is 11000-15000 Nm 3 The design is based on a flow rate of 45-60 Nm³ / h, which is equivalent to a flow rate of 45-60 Nm³ / h. 3 / t, then the theoretical fuel temperature drops to 2130℃ and 2106℃ respectively, which are 70℃ and 94℃ lower than the uninjected coke oven gas. Therefore, under otherwise unchanged conditions, 1Nm 3 The effect of a coke oven per ton on the theoretical combustion temperature is approximately 1.5℃. To maintain the baseline theoretical combustion temperature, the hot blast temperature of the blast furnace needs to be increased to at least 1250℃ and the oxygen enrichment rate to 7%. However, most blast furnaces in the industry face difficulties in achieving these conditions. Therefore, from an applicability perspective, it is recommended that the injection flow rate be controlled at 10000 Nm³. 3 The temperature is reduced to approximately 100°C / h to minimize the impact of the drop in theoretical combustion temperature on the furnace condition.

[0030] In terms of the amount of gas in the blast furnace belly, under the baseline conditions, the amount of gas in the blast furnace belly is 5720 m³. 3 / min, the furnace gas index Vbg is 55-56 m / min, when the injection rate is 1100 Nm 3 At approximately / h, the gas volume in the furnace belly is 5748m³. 3 The above-mentioned injection rates ( / min) and furnace gas index are all within the normal fluctuation range. The injection rate is 11000-15000 Nm³. 3 When the gas flow rate in the furnace reaches approximately 6050-6200 m³ / h, the gas volume in the furnace belly increases to 6050-6200 m³ / h. 3 / min, the blast furnace gas index Vbg rises to 58-59.5m / min. When the blast furnace gas index deviates too much from the normal value, it is easy to cause: (1) Increased pressure difference in the furnace, increased gas volume leads to increased resistance to gas rise, and increased pressure difference (ΔP). (2) Decreased gas distribution and airflow stability, affecting the flow of molten iron and heat transfer. (3) Decreased heat exchange efficiency, shortened heat exchange time, resulting in increased gas temperature at the furnace top, and insufficient heat absorption. (4) Reduced reduction reaction efficiency. (5) Obstructed descent of furnace charge, deterioration of charge column permeability. (6) Increased fuel consumption and energy consumption, and increased fuel ratio. At this time, the above effects can be reduced by reducing air volume or air temperature, controlling oxygen enrichment rate, and optimizing charging system. However, in general, most of the above adjustments will have obvious conflicts with the control of theoretical combustion temperature. Therefore, the control of blast furnace gas volume can be achieved by appropriately reducing air volume by 50-150m. 3 The hot air pressure should be controlled to not exceed the upper limit, and the airflow at the center and edge can be appropriately developed in the fabric matrix.

[0031] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for stable operation of a blast furnace under hydrogen-rich smelting conditions, characterized in that: To ensure continuous and stable operation of the blast furnace and injection system during coke oven gas injection, the control standard for ammonia in harmful impurities of coke oven gas is set at 10 mg / Nm³. 3 Within 15 mg / Nm³, the tar content is within 15 mg / Nm³. 3 Within 105 mg / Nm 3 Within.

2. The method for stable operation of a blast furnace under hydrogen-rich smelting conditions according to claim 1, characterized in that: It also includes a secondary purification system for the tar.

3. The method for stable operation of a blast furnace under hydrogen-rich smelting conditions according to claim 1, characterized in that: It also includes the addition of a coke oven gas tar removal system, a naphthalene removal system, and an ammonia removal system, in the order of tar removal, naphthalene removal, and ammonia removal.

4. The method for stable operation of a blast furnace under hydrogen-rich smelting conditions according to claim 3, characterized in that: The tar removal system employs tubular electrostatic tar removal technology.

5. The method for stable operation of a blast furnace under hydrogen-rich smelting conditions according to claim 3, characterized in that: The naphthalene removal system employs temperature-switching adsorption separation technology.

6. The method for stable operation of a blast furnace under hydrogen-rich smelting conditions according to claim 3, characterized in that: The deammoniation system employs phosphoric acid solution absorption technology.

7. The method for stable operation of a blast furnace under hydrogen-rich smelting conditions according to claim 1, characterized in that: The jet flow rate is controlled at 10000 Nm 3 / h, equivalent to 4 Nm of iron 3 / tHM.

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