Flue gas waste heat utilization system and method for hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace

Abstract

The invention belongs to the technical field of blast furnace ironmaking, and particularly discloses a flue gas waste heat utilization system and method for a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace, and the method comprises the following steps: firstly, injecting medium oil into a flue gas heat exchanger, and then starting a circulating pump; then the flue gas enters a flue gas heat exchanger to heat medium oil; then the decarburized coal gas is introduced into a coal gas heat exchanger for heat exchange, and the decarburized coal gas can be preheated; afterheat of the flue gas after preheating of the decarburized coal gas is utilized to preheat combustion-supporting air and furnace-burning coal gas; then the combustion-supporting air and the furnace-burning gas are introduced into the gas heating furnace; and finally, the flue gas bypass valve is opened to discharge the residual flue gas. In order to solve the problem of high energy consumption of a hydrogen-rich carbon circulating oxygen blast furnace due to the fact that flue gas waste heat is not recycled, a hot oil pipe indirect heat exchange technology is adopted, decarburized coal gas is heated through medium oil, meanwhile, the flue gas waste heat obtained after the decarburized coal gas is heated further preheats furnace burning air and coal gas, flue gas waste heat utilization is achieved, and the utilization efficiency is higher.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnace ironmaking, and in particular to a system and method for utilizing waste heat of flue gas from a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace. Background Art

[0002] The hydrogen-rich carbon circulating oxygen blast furnace uses an extrusion air compressor to pre-treat the air and finally obtain hydrogen-rich carbon circulating gas. Then, the hydrogen-rich carbon circulating gas enters the oxygen generation device to produce hydrogen and oxygen by electrolysis of water, in which the hydrogen will enter the furnace together with a part of the coal gas to form hydrogen-rich gas. Then, the generated oxygen is subjected to a series of cooling, purification and other treatments to react with the slag in the blast furnace to produce reducing gas. During the smelting process, the presence of hydrogen-rich gas is conducive to providing sufficient oxygen and increasing the combustion rate and combustion temperature of the combustion materials in the furnace. At the same time, the hydrogen in the hydrogen-rich gas can also undergo chemical reactions, thereby promoting the process of reducing iron oxide ore. Throughout the process, the introduction of hydrogen-rich carbon circulating gas not only improves the reduction efficiency, optimizes the blast furnace combustion process, but also improves the production efficiency and output of the blast furnace.

[0003] The gas heating furnace is a large hot blast furnace that uses blast furnace gas as fuel. It is mainly used to heat the combustion air and continuously provide the blast furnace with high-temperature hot air of more than 1000 degrees. This heating furnace is one of the main supporting equipment for the blast furnace in the ironmaking plant to ensure the efficient operation of the blast furnace. When the gas heating furnace is running, the flue gas temperature can reach up to 350℃ and the flue gas volume is large, 2500m 3 The blast furnace flue gas volume exceeds 200,000 cubic meters per hour. If the flue gas waste heat is not recovered or is not recovered sufficiently, the energy consumption of the hydrogen-rich carbon cycle oxygen blast furnace process will increase. Therefore, in order to improve the energy efficiency of the hydrogen-rich carbon cycle oxygen blast furnace and reduce the operating cost, it is necessary to design a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace flue gas waste heat utilization system and method, through the medium oil indirect heat exchange, to achieve flue gas preheating of decarbonized coal gas, and after heating the decarbonized coal gas, the flue gas waste heat is further used to preheat the combustion air and furnace gas, so as to improve the process energy efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a system and method for utilizing waste heat from flue gas in a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace, so as to solve the problem of increased energy consumption in the hydrogen-rich carbon circulating oxygen blast furnace process due to failure to recover waste heat from flue gas in the gas heating furnace.

[0005] To achieve the above-mentioned purpose, the basic scheme provided by the present invention is: a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace flue gas waste heat utilization system, comprising a decarbonized gas heat exchanger, a flue gas heat exchanger, a furnace gas heat exchanger, a combustion air heat exchanger and a flue gas inlet pipe, the decarbonized gas heat exchanger is connected to the decarbonized gas inlet pipe, the flue gas heat exchanger, the furnace gas heat exchanger and the combustion air heat exchanger are all connected to the flue gas inlet pipe, the flue gas inlet pipes of the flue gas heat exchanger, the furnace gas heat exchanger and the combustion air heat exchanger are respectively provided with a medium oil waste heat control valve, a furnace gas preheating control valve and a combustion air preheating control valve, the flue gas inlet pipe is provided with a flue gas bypass valve, the low-temperature end of the flue gas heat exchanger is connected to a chimney, and the flue gas heat exchanger and the chimney are connected. A flue gas outlet valve is provided on the connected pipeline, the flue gas inlet pipe is connected to the chimney, the flue gas heat exchanger is connected to the decarbonized coal gas heat exchanger, a circulating pump is provided on the pipeline connecting the flue gas heat exchanger and the decarbonized coal gas heat exchanger, the outlet pipe of the decarbonized coal gas heat exchanger is connected to the gas heating furnace, the furnace gas outlet pipe and the combustion air outlet pipe are both connected to the gas heating furnace, the furnace gas outlet pipe is connected to the outlet pipe of the decarbonized coal gas heat exchanger, a steam control valve is provided on the pipeline connecting the furnace gas outlet pipe and the decarbonized coal gas heat exchanger outlet pipe, the low-temperature end of the flue gas heat exchanger is connected to the flue gas inlet pipe, a series preheating control valve is provided on the pipeline connecting the low-temperature end of the flue gas heat exchanger and the flue gas inlet pipe, and a blast furnace is connected to the gas heating furnace.

[0006] The working principle and beneficial effects of the present invention are as follows: when it is necessary to utilize the flue gas waste heat of the gas heating furnace, first open the oil injection pump to allow the medium oil to enter the flue gas heat exchanger, then open the circulation pump to allow the medium oil to circulate in the flue gas heat exchanger and the decarbonized coal gas heat exchanger, then open the valve of the decarbonized coal gas to allow the decarbonized coal gas to enter the heat exchange pipe of the decarbonized coal gas heat exchanger, so that the decarbonized coal gas absorbs the heat of the medium oil in the decarbonized coal gas heat exchanger, and the decarbonized coal gas can be heated, and then open the valves of the combustion air and the furnace gas to allow the combustion air and the furnace gas to enter the combustion air heat exchanger and the furnace gas heat exchanger respectively. In the process, the series preheating control valve, the combustion air preheating control valve and the furnace gas preheating control valve are opened, so that the flue gas of the gas heating furnace enters the combustion air heat exchanger and the furnace gas heat exchanger respectively, and the combustion air and the furnace gas are heated. Finally, the flue gas outlet valve is opened, and the remaining flue gas is discharged into the chimney through the pipe to complete the utilization of the waste heat of the gas heating furnace flue gas. The method of indirect heat exchange of medium oil to heat the decarbonized coal gas can effectively ensure the safe and stable operation of the system, and the waste heat of the flue gas after heating the decarbonized coal gas can be further used to preheat the combustion air and the furnace gas, thereby improving the utilization efficiency of the waste heat of the flue gas.

[0007] Option 2, which is the preferred option of the basic option, is provided with a parallel preheating control valve on the flue gas inlet pipe; the parallel preheating control valve can be opened according to demand, and the waste heat of the flue gas from the gas heating furnace can be used to preheat the decarbonized gas, furnace gas and combustion air at the same time.

[0008] Scheme 3, a method for utilizing waste heat from flue gas of a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace, comprising the following steps:

[0009] S1: When the waste heat of flue gas from the gas heating furnace needs to be utilized, the staff in the control room first remotely turns on the oil injection pump to inject medium oil into the flue gas heat exchanger, and then turns off the oil injection pump;

[0010] S2: Then the staff in the control room starts the circulation pump, so that the medium oil in the flue gas heat exchanger enters the decarbonized coal gas heat exchanger through the pipeline, and then enters the flue gas heat exchanger again through the circulation pump, forming a closed cycle;

[0011] S3: When the medium oil circulates between the flue gas heat exchanger and the decarbonized coal gas heat exchanger, the staff in the control room opens the medium oil preheating control valve to allow the flue gas to enter the flue gas heat exchanger through the pipeline to heat the medium oil;

[0012] S4: When the medium oil is heated to 180℃-250℃, the staff in the control room opens the valve of the decarbonized coal gas, allowing the decarbonized coal gas to enter the heat exchange tube of the decarbonized coal gas heat exchanger. The decarbonized coal gas absorbs the heat of the medium oil in the decarbonized coal gas heat exchanger, and the decarbonized coal gas can be preheated;

[0013] S5: When the decarbonized coal gas is preheated to 150°C-180°C, the preheated decarbonized coal gas is introduced into the coal gas heating furnace for further heating;

[0014] S6: Then the staff in the control room opens the valves of the combustion air and the furnace gas, so that the combustion air and the furnace gas enter the combustion air heat exchanger and the furnace gas heat exchanger respectively, and then opens the series preheating control valve, the combustion air preheating control valve and the furnace gas preheating control valve, so that the flue gas after preheating the decarbonized coal gas enters the combustion air heat exchanger and the furnace gas heat exchanger respectively, so as to heat the combustion air and the furnace gas;

[0015] S7: When the combustion air and furnace gas are preheated to 100℃-200℃, the preheated combustion air and furnace gas are introduced into the gas heating furnace, and finally the flue gas bypass valve is opened to discharge the remaining flue gas into the chimney through the pipeline.

[0016] The method of heating the decarbonized coal gas by indirect heat exchange with medium oil can effectively ensure the safe and stable operation of the system; if the decarbonized coal gas is directly heated by the flue gas of the gas heating furnace, gas leakage is likely to occur due to the large difference in pressure between the flue gas of the heating furnace and the decarbonized coal gas; and the waste heat of the flue gas after heating the decarbonized coal gas is used to further preheat the combustion air and the furnace gas, thereby improving the utilization efficiency of the waste heat of the flue gas; at the same time, the steam is connected to the preheated decarbonized coal gas pipeline, which can not only humidify the decarbonized coal gas but also further heat the decarbonized coal gas.

[0017] Option 4 is the preferred option of the basic option. In S1, the medium oil is Great Wall L-QB300 heat transfer oil; Great Wall L-QB300 heat transfer oil has good oxidation stability, long service life, low volatility, good thermal conductivity and good low-temperature fluidity, and is suitable for closed heat transfer systems.

[0018] Scheme 5 is the preferred basic scheme. In S1, the pressure of the medium oil is 0.3MPa-0.5MPa; the pressure of the medium oil is maintained at 0.3MPa-0.5MPa, thereby ensuring safe and stable operation of the system.

[0019] Option six, which is the preferred option of the basic option, each of the heat exchangers is a shell and tube heat exchanger; the shell and tube heat exchanger is made of stainless steel, which is not only corrosion-resistant, but also has the characteristics of good pressure bearing capacity and high heat exchange efficiency.

[0020] Option seven is the preferred basic option. In S4, the pressure of the decarbonized gas is higher than 0.25 MPa, which enables the system to operate safely and stably and prevents gas leakage caused by the decarbonized gas pressure being too low.

[0021] Scheme 8 is the preferred basic scheme. In S4, the pressure of the medium oil is 0.05MPa-0.1MPa higher than the pressure of the decarbonized coal gas. The pressure of the medium oil is always higher than that of the decarbonized coal gas, which can effectively prevent the occurrence of gas leakage.

[0022] Option nine is the preferred option of the basic option. In S5, when the preheated decarbonized coal gas is heated to 1200° C. in the coal gas heating furnace, the decarbonized coal gas is introduced into the blast furnace.

[0023] Scheme 10 is the preferred basic scheme. In S7, when the preheated furnace gas enters the gas heating furnace, the control room staff opens the steam control valve to spray steam into the pipe of the decarbonized gas outlet. The flue gas temperature discharged from the gas heating furnace is below 60°C. Opening the steam control valve can humidify the preheated decarbonized gas and further heat the decarbonized gas. The temperature of the final gas heating furnace flue gas is controlled below 60°C, making the flue gas waste heat utilization more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace flue gas waste heat utilization system of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below through specific embodiments:

[0026] The figure marks in the drawings of the specification include: 1. Decarbonized coal gas heat exchanger; 2. Flue gas heat exchanger; 3. Boiler gas heat exchanger; 4. Combustion air heat exchanger; 5. Medium oil preheating control valve; 6. Parallel preheating control valve; 7. Boiler gas preheating control valve; 8. Combustion air preheating control valve; 9. Series preheating control valve; 10. Flue gas bypass valve; 11. Flue gas outlet valve; 12. Circulation pump; 13. Decarbonized coal gas inlet pipe; 14. Flue gas inlet pipe; 15. Steam control valve; 16. Chimney; 17. Gas heating furnace; 18. Blast furnace.

[0027] like Figure 1 As shown: a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace flue gas waste heat utilization system, including a decarbonized gas heat exchanger 1, a flue gas heat exchanger 2, a furnace gas heat exchanger 3, a combustion air heat exchanger 4 and a flue gas inlet pipe 14, the decarbonized gas heat exchanger 1 is connected with a decarbonized gas inlet pipe 13, the flue gas heat exchanger 2, the furnace gas heat exchanger 3 and the combustion air heat exchanger 4 are all connected with the flue gas inlet pipe 14, the flue gas heat exchanger 2, the furnace gas heat exchanger 3 and the combustion air heat exchanger 4 are respectively provided with a medium oil waste heat control valve 5, a furnace gas preheating control valve 7 and a combustion air preheating control valve 8 on the flue gas inlet pipe, a flue gas bypass valve 10 is provided on the flue gas inlet pipe 14, the low temperature end of the flue gas heat exchanger 2 is connected with a chimney 16, and the pipeline connecting the flue gas heat exchanger 2 and the chimney 16 is provided with a flue gas Outlet valve 11, flue gas inlet pipe 14 is connected with chimney 16, flue gas heat exchanger 2 is connected with decarbonized coal gas heat exchanger 1, a circulating pump 12 is arranged on the pipeline connecting flue gas heat exchanger 2 and decarbonized coal gas heat exchanger 1, the outlet pipe of decarbonized coal gas heat exchanger 1 is connected with gas heating furnace 17, the outlet pipe of furnace gas and combustion air outlet pipe are both connected with gas heating furnace 17, the outlet pipe of furnace gas and the outlet pipe of decarbonized coal gas heat exchanger 1 are connected, a steam control valve 15 is arranged on the pipeline connecting furnace gas outlet pipe and decarbonized coal gas heat exchanger 1 outlet pipe, the low temperature end of flue gas heat exchanger 2 is connected with flue gas inlet pipe 14, a series preheating control valve 9 and a parallel preheating control valve 6 are arranged on the pipeline connecting low temperature end of flue gas heat exchanger 2 and flue gas inlet pipe 14, a blast furnace 18 is connected to gas heating furnace 17.

[0028] Example 1

[0029] like Figure 1 As shown, a method for utilizing waste heat from flue gas of a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace comprises the following steps:

[0030] S1: When the waste heat of the flue gas of the gas heating furnace needs to be utilized, the staff in the control room first remotely turns on the oil injection pump to inject medium oil into the flue gas heat exchanger 2. The medium oil is Great Wall L-QB300 heat transfer oil, and the pressure of the medium oil is 0.3MPa-0.5MPa. Then the oil injection pump is turned off;

[0031] S2: Then the staff in the control room starts the circulation pump 12, so that the medium oil in the flue gas heat exchanger 2 enters the decarbonized coal gas heat exchanger 1 through the pipeline, and then enters the flue gas heat exchanger 2 again through the circulation pump 12, forming a closed cycle;

[0032] S3: When the medium oil circulates between the flue gas heat exchanger 2 and the decarbonized coal gas heat exchanger 1, the staff in the control room opens the medium oil preheating control valve 5, so that the flue gas enters the flue gas heat exchanger 2 through the pipeline to heat the medium oil;

[0033] S4: When the medium oil is heated to 180℃-250℃, the staff in the control room opens the valve of the decarbonized coal gas, allowing the decarbonized coal gas to enter the heat exchange tube of the decarbonized coal gas heat exchanger 1. The pressure of the decarbonized coal gas is higher than 0.25MPa. The pressure of the medium oil in the decarbonized coal gas heat exchanger 1 is 0.05MPa-0.1MPa higher than the pressure of the decarbonized coal gas. The decarbonized coal gas absorbs the heat of the medium oil in the coal gas heat exchanger 1, and the decarbonized coal gas can be preheated.

[0034] S5: When the decarbonized coal gas is preheated to 150° C.-180° C., the preheated decarbonized coal gas is introduced into the coal gas heating furnace 17 for further heating. When the preheated decarbonized coal gas is heated to 1200° C. in the coal gas heating furnace 17, the decarbonized coal gas is introduced into the blast furnace 18;

[0035] S6: Then the staff in the control room opens the valves of the combustion air and the furnace gas, so that the combustion air and the furnace gas enter the combustion air heat exchanger 4 and the furnace gas heat exchanger 3 respectively, and then opens the series preheating control valve 9, the combustion air preheating control valve 8 and the furnace gas preheating control valve 7, so that the flue gas after preheating the decarbonized coal gas enters the combustion air heat exchanger 4 and the furnace gas heat exchanger 3 respectively, so as to heat the combustion air and the furnace gas;

[0036] S7: When the combustion air and the furnace gas are preheated to 100℃-200℃, the preheated combustion air and furnace gas are introduced into the gas heating furnace 17, and finally the flue gas bypass valve 10 is opened to discharge the remaining flue gas through the pipeline into the chimney 16, and the flue gas temperature is below 60℃. When it is necessary to humidify the preheated decarbonized gas, the staff in the control room opens the steam control valve 15 to spray steam into the pipeline of the preheated decarbonized gas, thereby humidifying the decarbonized gas; if it is not necessary to humidify the preheated decarbonized gas, the staff in the control room closes the steam control valve 15.

[0037] The decarbonized coal gas is first preheated by the above-mentioned series preheating method, and then the waste heat of the flue gas after heating the decarbonized coal gas is further used to preheat the combustion air and the furnace gas. This method can heat the decarbonized coal gas to 180°C, and finally make the exhaust flue gas temperature below 60°C, so that the utilization efficiency of the waste heat of the flue gas is higher.

[0038] Example 2

[0039] like Figure 1 As shown, a method for utilizing waste heat from flue gas of a hydrogen-rich carbon circulating oxygen blast furnace gas heating furnace comprises the following steps:

[0040] S1: When the waste heat of the flue gas of the gas heating furnace needs to be utilized, the staff in the control room first remotely turns on the oil injection pump to inject medium oil into the flue gas heat exchanger 2. The medium oil is Great Wall L-QB300 heat transfer oil, and the pressure of the medium oil is 0.3MPa-0.5MPa. Then the oil injection pump is turned off;

[0041] S2: Then the staff in the control room starts the circulation pump 12, so that the medium oil in the flue gas heat exchanger 2 enters the decarbonized coal gas heat exchanger 1 through the pipeline, and then enters the flue gas heat exchanger 2 again through the circulation pump 12, forming a closed cycle;

[0042] S3: When the medium oil circulates between the flue gas heat exchanger 2 and the decarbonized coal gas heat exchanger 1, the staff in the control room opens the medium oil preheating control valve 5, the parallel preheating control valve 6, the combustion air preheating control valve 8 and the furnace gas preheating control valve 7, and then the flue gas enters the decarbonized coal gas heat exchanger 1, the combustion air heat exchanger 4 and the furnace gas heat exchanger 3 respectively to preheat the decarbonized coal gas, the combustion air and the furnace gas at the same time;

[0043] S4: Finally, open the flue gas bypass valve 10 and the flue gas outlet valve 11, and discharge the remaining flue gas through the pipe into the chimney 16. If the preheated decarbonized coal gas needs to be humidified, the staff in the control room opens the steam control valve 15 to spray steam into the pipeline of the preheated decarbonized coal gas, thereby humidifying the decarbonized coal gas.

[0044] When the decarbonized coal gas, combustion air and furnace gas are preheated at the same time by the above-mentioned parallel preheating method, the decarbonized coal gas can only be heated to 150°C, and the final exhaust flue gas temperature is greater than 60°C, failing to fully utilize the flue gas waste heat.

[0045] In summary, in Example 1, the medium oil is first heated by flue gas through a series preheating method, and then the decarbonized coal gas is preheated by the medium oil. Since the pressure difference between the decarbonized coal gas and the flue gas of the gas heating furnace is large, the decarbonized coal gas is heated by indirect heat exchange with the medium oil, thereby ensuring the safe and stable operation of the system; then the flue gas waste heat after heating the decarbonized coal gas is further used to preheat the combustion air and the furnace gas. This method can heat the decarbonized coal gas to 180°C, so that the final exhaust flue gas temperature is below 60°C; in Example 2, The parallel preheating method uses flue gas to heat the medium oil, and then preheats the decarbonized coal gas through the medium oil. At the same time, the flue gas is introduced into the combustion air heat exchanger and the furnace gas heat exchanger to preheat the combustion air and the furnace gas at the same time. In this way, the decarbonized coal gas can be heated to a maximum of 150°C, and the final flue gas temperature emitted by the gas heating furnace is greater than 60°C, and the full utilization of the flue gas waste heat of the gas heating furnace is not achieved. However, Example 1 maximizes the utilization of the flue gas waste heat of the gas heating furnace, making the utilization efficiency of the flue gas waste heat of the gas heating furnace higher.

[0046] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace flue gas waste heat utilization system, characterized in that: The invention comprises a decarbonized coal gas heat exchanger (1), a flue gas heat exchanger (2), a furnace gas heat exchanger (3), a combustion air heat exchanger (4) and a flue gas inlet pipe (14), wherein the decarbonized coal gas heat exchanger (1) is connected to the decarbonized coal gas inlet pipe (13), the flue gas heat exchanger (2), the furnace gas heat exchanger (3) and the combustion air heat exchanger (4) are all connected to the flue gas inlet pipe (14), and the flue gas heat exchanger (2), the furnace gas heat exchanger (3) and the combustion air heat exchanger (4) are connected to the flue gas inlet pipe (14). A medium oil preheating control valve (5), a furnace gas preheating control valve (7) and a combustion air preheating control valve (8) are respectively provided on the flue gas inlet pipe (14) of the combustion air heat exchanger (4); a flue gas bypass valve (10) is provided on the flue gas inlet pipe (14); a chimney (16) is connected to the low-temperature end of the flue gas heat exchanger (2); a flue gas outlet valve (11) is provided on the pipeline connecting the flue gas heat exchanger (2) and the chimney (16); The flue gas inlet pipe (14) is connected to the chimney (16), the flue gas heat exchanger (2) is connected to the decarbonized coal gas heat exchanger (1), a circulating pump (12) is provided on the pipeline connecting the flue gas heat exchanger (2) and the decarbonized coal gas heat exchanger (1), the outlet pipe of the decarbonized coal gas heat exchanger (1) is connected to the coal gas heating furnace (17), the furnace gas outlet pipe and the combustion air outlet pipe are both connected to the coal gas heating furnace (17), and the furnace gas outlet pipe The flue gas heat exchanger (2) is connected to the outlet pipe of the decarbonized coal gas heat exchanger (1), and a steam control valve (15) is provided on the pipeline connecting the outlet pipe of the furnace gas and the outlet pipe of the decarbonized coal gas heat exchanger (1). The low-temperature end of the flue gas heat exchanger (2) is connected to the flue gas inlet pipe (14), and a series preheating control valve (9) is provided on the pipeline connecting the low-temperature end of the flue gas heat exchanger (2) and the flue gas inlet pipe (14). The coal gas heating furnace (17) is connected to a blast furnace (18).

2. A hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace flue gas waste heat utilization system according to claim 1, characterized in that: The flue gas inlet pipe (14) is provided with a parallel preheating control valve (6).

3. A method for utilizing waste heat from flue gas of a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace, characterized in that: The following steps are involved: S1: When it is necessary to utilize the flue gas waste heat of the gas heating furnace, the staff in the control room first remotely turns on the oil injection pump to inject medium oil into the flue gas heat exchanger (2), and then turns off the oil injection pump; S2: Then, the staff in the control room starts the circulation pump (12), so that the medium oil in the flue gas heat exchanger (2) enters the decarbonized coal gas heat exchanger (1) through the pipeline, and then enters the flue gas heat exchanger (2) again through the circulation pump (12), forming a closed cycle; S3: When the medium oil circulates between the flue gas heat exchanger (2) and the decarbonized coal gas heat exchanger (1), the staff in the control room opens the medium oil preheating control valve (5) to allow the flue gas to enter the flue gas heat exchanger (2) through the pipeline to heat the medium oil; S4: When the medium oil is heated to 180°C-250°C, the staff in the control room opens the valve of the decarbonized coal gas, allowing the decarbonized coal gas to enter the heat exchange tube of the decarbonized coal gas heat exchanger (1). The decarbonized coal gas absorbs the heat of the medium oil in the decarbonized coal gas heat exchanger (1), thereby preheating the decarbonized coal gas. S5: When the decarbonized coal gas is preheated to 150° C.-180° C., the preheated decarbonized coal gas is introduced into the coal gas heating furnace (17) for further heating; S6: Then the staff in the control room opens the valves of the combustion air and the furnace gas, so that the combustion air and the furnace gas enter the combustion air heat exchanger (4) and the furnace gas heat exchanger (3) respectively, and then opens the series preheating control valve (9), the combustion air preheating control valve (8) and the furnace gas preheating control valve (7), so that the flue gas after preheating the decarbonized coal gas enters the combustion air heat exchanger (4) and the furnace gas heat exchanger (3) respectively, so as to heat the combustion air and the furnace gas; S7: When the combustion air and the furnace gas are preheated to 100°C-200°C, the preheated combustion air and the furnace gas are introduced into the gas heating furnace (17), and finally the flue gas bypass valve (10) is opened to allow the remaining flue gas to enter the chimney (16) through the pipeline for discharge.

4. A method for utilizing waste heat from flue gas of a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace according to claim 3, characterized in that: In S1, the medium oil is Great Wall L-QB300 heat transfer oil.

5. The method for utilizing waste heat from flue gas of a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace according to claim 3, characterized in that: In S1, the pressure of the medium oil is 0.3MPa-0.5MPa.

6. The method for utilizing waste heat from flue gas of a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace according to claim 3, characterized in that: Each of the heat exchangers is a shell and tube heat exchanger.

7. The method for utilizing waste heat from flue gas of a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace according to claim 3, characterized in that: In S4, the pressure of the decarbonized coal gas is higher than 0.25 MPa.

8. The method for utilizing waste heat from flue gas of a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace according to claim 3, characterized in that: In S4, the pressure of the medium oil is 0.05MPa-0.1MPa higher than the pressure of the decarbonized coal gas.

9. The method for utilizing waste heat from flue gas of a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace according to claim 3, characterized in that: In S5, the preheated decarbonized coal gas is heated to 1200°C in the coal gas heating furnace (17), and then the decarbonized coal gas is introduced into the blast furnace (18).

10. The method for utilizing waste heat from flue gas of a hydrogen-rich carbon cycle oxygen blast furnace gas heating furnace according to claim 3, characterized in that: In S7, when the preheated combustion gas enters the gas heating furnace (17), the staff in the control room opens the steam control valve (15) to spray steam into the pipe of the decarbonized gas outlet, and the temperature of the flue gas discharged from the gas heating furnace is below 60°C.

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