Reducing gas injection method of blast furnace top gas circulation system

Abstract

The invention discloses a reducing gas injection method of a blast furnace top gas circulation system. The reducing gas injection method comprises the following steps: heating oxygen-enriched air to 1100-1300 DEG C through a hot blast stove, and conveying the heated oxygen-enriched air to a tuyere through a bustle pipe; reducing gas is pressurized to 1.8 MPa through a compressor, is input into an annular pipe of the reducing gas bustle pipe and then is shunted through branch pipes; the flow of the reducing gas is adjusted through electromagnetic valves on branch pipes of the reducing gas bustle pipe, so that the reducing gas is conveyed to a reducing gas spray gun through a pressure-resistant hose; a reducing gas spray gun and a pulverized coal injection spray gun are oppositely arranged on the two sides of the tuyere, and the reducing gas spray gun injects reducing gas to the convolution area in a sequence pulse or continuous mode to supplement the tuyere air quantity of the convolution area. According to the method, the reducing gas is pressurized to 1.8 MPa, so that the blast kinetic energy is improved, the air volume of a convolution area is quickly supplemented, and the problem of air volume atrophy of the blast furnace caused by the increase of the oxygen content of the oxygen-enriched air is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of blast furnace ironmaking, and particularly to a method for injecting reducing gas in a blast furnace top gas recycling system. Background Art

[0002] In the iron and steel industry, the blast furnace process accounts for 70% - 90% of the total iron and steel emissions. Due to its mature process technology, large production capacity, and high efficiency, the blast furnace will still be the mainstream ironmaking equipment to support the huge demand for steel materials for a considerable period in the future. Therefore, for energy conservation, emission reduction, and low-carbon blast furnace technology is the path that the iron and steel industry needs to explore. The top gas recycling technology is one of the current mainstream technologies. Its technical route is to process the blast furnace top gas, extract reducing gases such as CO, and inject them into the blast furnace through the furnace shaft or hearth to increase the reduction potential inside the furnace, promote the development of indirect reduction, reduce the proportion of direct reduction, thereby reducing the consumption of coke or fixed carbon in blast furnace smelting, and achieving low-carbon smelting of the blast furnace.

[0003] When the blast furnace adopts the top gas recycling technology, in order to ensure the theoretical combustion temperature of the blast furnace, the oxygen enrichment rate is usually increased. However, the increase in the oxygen enrichment rate will lead to the shrinkage of the blast furnace air volume, thereby reducing the blast kinetic energy, affecting the gas distribution in the blast furnace and the smooth operation of the furnace condition. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for injecting reducing gas in a blast furnace top gas recycling system, which overcomes the fluctuations of the blast furnace condition caused by the increase in the oxygen enrichment rate, ensures energy conservation and carbon reduction of the blast furnace, and at the same time does not affect the smooth operation and efficiency of the furnace condition.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A method for injecting reducing gas in a blast furnace top gas recycling system, comprising the following steps:

[0007] Oxygen-enriched hot air supply: Heating oxygen-enriched air to 1100 - 1300 °C through a hot blast stove and then transporting it to the tuyere through a hot blast manifold;

[0008] Reducing gas pressurization and distribution: Pressurizing the reducing gas to 1.8 MPa through a compressor and then inputting it into the annular pipe of the reducing gas manifold, and then shunting through branch pipes;

[0009] Dynamic injection control: Adjusting the reducing gas flow rate through the solenoid valves on each branch pipe of the reducing gas manifold, so that the reducing gas is transported to the reducing gas lance through a pressure-resistant hose;

[0010] Coordinated injection operation: Arranging the reducing gas lance and the pulverized coal injection lance oppositely on both sides of the tuyere, and injecting the reducing gas into the raceway in a sequence pulse or continuous manner through the reducing gas lance to supplement the tuyere air volume in the raceway.

[0011] Furthermore, the method further includes:

[0012] Real-time monitoring of the temperature, pressure and gas composition in the raceway, and dynamically adjusting at least one of the following parameters through a controller:

[0013] a. The opening degree of the solenoid valve to control the flow rate of the reducing gas;

[0014] b. The output pressure of the compressor to adjust the injection speed of the reducing gas;

[0015] c. The ratio of the pulverized coal injection rate to the reducing gas injection rate.

[0016] Furthermore, the method further includes: setting a pressure sensor in the reducing gas pipeline for real-time monitoring of the reducing gas pressure;

[0017] The compressor dynamically adjusts the output pressure according to the real-time monitored reducing gas pressure value, and controls the reducing gas pressure between 1.8 and 2.0 MPa.

[0018] Furthermore, the reducing gas is obtained by purifying the top gas of the furnace through a gas separation device, and the purification steps include: cooling and dust removal, desulfurization and decarbonization.

[0019] Furthermore, the reducing gas manifold is located directly above the hot air manifold, and the branch pipes are evenly spaced circumferentially along the annular pipe and extend obliquely downward from the annular pipe.

[0020] Furthermore, the included angle between the reducing gas lance and the pulverized coal injection lance and the axis of the air duct is 10° to 90°. 。

[0021] In this embodiment, by pressurizing the reducing gas to 1.8 MPa (far exceeding the conventional 0.3 - 0.6 MPa), the blast kinetic energy is increased, the air volume in the raceway is quickly replenished, and the problem of the shrinkage of the blast furnace air volume caused by the increase in oxygen enrichment is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a system block diagram of the blast furnace top gas circulation system of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] To further illustrate the embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, mainly used to illustrate the embodiments, and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0024] The present invention will be further described in conjunction with the accompanying drawings and specific embodiments.

[0025] As Figure 1 shown, the present invention provides a blast furnace top gas recycling system, including a gas separation system 2, a compressor 3, a reducing gas circumferential pipe, and a reducing gas lance. The arrangement of the reducing gas circumferential pipe and the reducing gas lance in the blast furnace is as follows: The reducing gas circumferential pipe is arranged above the hot air circumferential pipe at the bottom 12 of the blast furnace, including an annular pipe and a plurality of branch pipes extending downward from the annular pipe at an inclination angle of 15° to 45°. The branch pipes are evenly spaced circumferentially along the annular pipe (the spacing is 0.5 to 2 meters) and are communicated with the annular pipe; solenoid valves 4 are arranged on each branch pipe and are connected to the reducing gas lance through a hose with a pressure resistance ≥ 2.5 MPa; the reducing gas lance and the pulverized coal injection lance are arranged oppositely on both sides of the tuyere, and the angles between the reducing gas lance, the pulverized coal injection lance and the axis of the air pipe are 10° to 90°, and the nozzle of the reducing gas lance is inclined downward by 5° to 15°.

[0026] The top gas at the top 11 of the blast furnace is purified and recovered through the gas separation system 2. The gas separation system 2 removes substances such as dust, CO2, and SO2 in the top gas through processes such as cooling and dust removal, desulfurization, and decarbonization, and obtains a reducing gas mainly composed of CO (carbon monoxide).

[0027] The compressor 3 is connected to the gas separation system 2 through a pipeline, and the reducing gas is pressurized and then input into the reducing gas circumferential pipe; the hot blast stove inputs oxygen-enriched air through a pipeline, connects to an external oxygen source such as an oxygen station, the oxygen-enriched air uses pure oxygen output from the oxygen production station, or is generated by mixing pure oxygen with the air output from the blower, and the oxygen-enriched air is heated to 1100 to 1300 °C by the hot blast stove and then transported to the corresponding tuyere through each branch pipe of the hot air circumferential pipe.

[0028] The present invention also provides a reducing gas injection method based on the above blast furnace top gas recycling system, including the following steps:

[0029] Oxygen-enriched hot air supply: The oxygen-enriched air is heated to 1100 to 1300 °C by the hot blast stove and then transported to the tuyere through the hot air circumferential pipe;

[0030] Reducing gas pressurization and distribution: The reducing gas is pressurized to 1.8 MPa by the compressor and then input into the annular pipe of the reducing gas circumferential pipe, and then shunted through the branch pipes;

[0031] Dynamic injection control: The flow rate of the reducing gas is adjusted through the solenoid valves on each branch pipe, so that the reducing gas is transported to the reducing gas lance through the pressure-resistant hose;

[0032] Coordinated injection operation: The reducing gas lance and the pulverized coal injection lance are arranged oppositely on both sides of the tuyere, and the reducing gas lance injects the reducing gas into the raceway in a sequence pulse or continuous manner to quickly supplement the blast volume of the blast furnace in the raceway region.

[0033] In this reducing gas injection method, it is necessary to monitor in real time parameters such as the temperature, pressure and gas composition in the raceway, and dynamically adjust at least one of the following parameters through a controller for injection control:

[0034] a. The opening degree of the solenoid valve to control the flow rate of the reducing gas;

[0035] b. The output pressure of the compressor to adjust the injection speed of the reducing gas;

[0036] c. The ratio of the pulverized coal injection rate to the reducing gas injection rate to adjust the combustion rate.

[0037] In this reducing gas injection method, pressure monitoring can be achieved in the following way: A pressure sensor is set in the reducing gas pipeline to monitor the reducing gas pressure in real time. The compressor then dynamically adjusts the output pressure according to the real-time monitored reducing gas pressure value, and controls the reducing gas pressure between 1.8 and 2.0 MPa.

[0038] In this embodiment, it is mainly applied to oxygen-enriched air with a high oxygen concentration (oxygen content ≥ 31%). Breaking through the conventional limit of the reducing gas pressure value of 0.3 - 0.6 MPa, by pressurizing the reducing gas to 1.8 MPa and directly injecting it into the tuyere raceway, the blast kinetic energy is increased, the air volume in the raceway is quickly supplemented, and the problem of the shrinkage of the blast furnace air volume caused by the increase in the oxygen content of the oxygen-enriched air is solved.

[0039] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes can be made to the present invention in terms of form and details without departing from the spirit and scope of the present invention defined by the appended claims, and all of them are within the protection scope of the present invention.

Claims

1. A method for injecting reducing gas in a blast furnace top gas recycling system, characterized in that, It includes the following steps: Oxygen-enriched hot air supply: Heat the oxygen-enriched air to 1100 - 1300 °C in a hot blast stove and then transport it to the tuyere through a hot air manifold; Reducing gas pressurization and distribution: Pressurize the reducing gas to 1.8 MPa with a compressor and then input it into the annular pipe of the reducing gas manifold, and then shunt it through branch pipes; Dynamic injection control: Adjust the flow rate of the reducing gas through the solenoid valves on each branch pipe of the reducing gas manifold, and transport the reducing gas to the reducing gas lance through a pressure-resistant hose; Cooperative injection operation: Arrange the reducing gas lance and the pulverized coal injection lance oppositely on both sides of the tuyere, and inject the reducing gas into the raceway in a sequence pulse or continuous manner to supplement the tuyere air volume in the raceway.

2. The method according to claim 1, characterized in that, It also includes: Real-time monitor the temperature, pressure and gas composition in the raceway, and dynamically adjust at least one of the following parameters through a controller: a. The opening degree of the solenoid valve to control the flow rate of the reducing gas; b. The output pressure of the compressor to adjust the injection speed of the reducing gas; c. The ratio of the pulverized coal injection rate to the reducing gas injection rate.

3. The method according to claim 1, characterized in that, It also includes: Install a pressure sensor in the reducing gas pipeline to monitor the reducing gas pressure in real time; The compressor dynamically adjusts the output pressure according to the real-time monitored reducing gas pressure value, and controls the reducing gas pressure between 1.8 - 2.0 MPa.

4. The method according to claim 1, characterized in that It also includes: The reducing gas is obtained by purifying the top gas of the furnace through a gas separation device, and the purification steps include: cooling and dust removal, desulfurization and decarbonization.

5. The method according to claim 1, wherein The reducing gas manifold is located directly above the hot air manifold, and the branch pipes are evenly spaced circumferentially along the annular pipe and extend obliquely downward from the annular pipe.

6. The method according to claim 1, characterized in that, The included angles between the reducing gas spray gun, the pulverized coal injection spray gun and the axis of the air duct are 10° to 90° 。

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