System and method for improving heat exchange of internal combustion hot blast stove through flue gas reuse

Abstract

The invention belongs to the technical field of energy conservation in the iron and steel industry, and particularly relates to a system and method for improving heat exchange of an internal combustion hot blast stove through flue gas reuse. Comprising hot-blast stoves, smoke exhaust branch pipes, a smoke exhaust header pipe and a chimney, hot air pipelines of the hot-blast stoves are connected with blast furnaces, each hot-blast stove is connected with the smoke exhaust header pipe through the corresponding smoke exhaust branch pipe, and the smoke exhaust header pipe is connected with the chimney; a regulating valve and a check valve are arranged on the smoke exhaust branch pipe, a smoke recycling pipeline is led out between the regulating valve and the check valve, the smoke recycling pipeline is connected into the hot-blast stove, the connecting position is above the gas pipeline and the combustion-supporting air pipeline, and the smoke recycling pipeline is bent upwards to be the same as the flame direction after being connected into the hot-blast stove. The check valve is close to one side of the smoke exhaust header pipe. The problem that convective heat transfer of checker bricks of the hot blast stove is weakened due to reduction of the smoke amount in the arch crown heat preservation and heating stage of the internal combustion type hot blast stove is solved through smoke recycling, and the hot air temperature can be effectively increased by 5 DEG C or above.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy saving in the steel industry, and particularly relates to a system and method for improving heat exchange of an internal combustion hot blast stove through flue gas recycling. BACKGROUND

[0002] The hot blast stove of a blast furnace is the main user of blast furnace gas consumption, accounting for more than 40% of the total blast furnace gas consumption. Therefore, optimizing the operation of the hot blast stove, while ensuring the temperature, temperature difference and air volume requirements of the blast furnace hot blast, and minimizing the gas consumption, is the goal that the workers of the blast furnace hot blast have always pursued.

[0003] The traditional hot blast stove burning operation generally adopts a two-stage burning system, namely a rapid heating stage and an arch top temperature insulation heating stage. The rapid heating stage is to rapidly heat with the maximum gas flow and the best air-fuel ratio. When the hot blast stove arch top temperature reaches the temperature specified in the on-site technical operation procedure (1350℃-1400℃), the hot blast stove arch top temperature insulation heating stage is entered. This stage is to gradually reduce the gas flow and air volume until the hot blast stove exhaust gas temperature reaches the temperature specified in the on-site technical operation procedure (350℃-400℃), and then the burning is stopped, the stove is smothered, and the stove is replaced. The main problem of this traditional burning system is that in the arch top temperature insulation heating stage, due to the one-sided pursuit of the "best air-fuel ratio", the weakening of the convection heat transfer of the middle and lower checker bricks in the hot blast stove caused by the reduction of the flue gas volume is ignored, which reduces the heat storage capacity of the middle and lower checker bricks. At the same time, due to the reduction of the flue gas volume, the flue gas is not evenly distributed in the cross section of the hot blast stove, which further leads to uneven temperature of the checker bricks in the cross section, affecting the heat transfer of the checker bricks, and further affecting the hot blast temperature entering the blast furnace.

[0004] The invention patent document "A high-efficiency practical hot blast stove burning control method" (CN112795716A) discloses a method of dynamically determining an efficient and practical burning system and control method based on heat balance testing, analysis and calculation. In the heat storage period, the stable arch top target temperature and the rapid increase of the heat storage capacity of the middle and lower checker bricks in the heat storage chamber are taken as the control targets, and the combustion is organized with a relatively small stable gas flow, but the best air-fuel ratio is not pursued. Instead, the total flue gas volume is basically unchanged (after the flue gas volume is reduced, the flue gas cannot fill all the checker brick holes, and the flue gas flow rate becomes small, which will weaken the convection heat transfer of the middle and lower checker bricks in the hot blast stove), until the exhaust gas temperature reaches the lower limit of the exhaust gas temperature specified in the burning process (350℃). The feature of this operation is to strengthen the convection heat transfer of the middle and lower checker bricks in the hot blast stove, and rapidly increase the heat storage capacity thereof. This method indeed can strengthen the convection heat transfer of the middle and lower checker bricks in the hot blast stove, but since the air-fuel ratio is enlarged, the cold air increases more, which is not conducive to the high blast temperature.

[0005] Patent document "a blast furnace hot blast stove flue gas self-circulation combustion method and system" (CN201310067318), the method mixes air and flue gas to form hot blast stove combustion supporting gas, to realize high wind temperature and reduce the production of NOx, without considering the heat transfer efficiency of checker bricks, and without taking measures to improve the heat transfer of checker bricks.

[0006] Patent document "a blast furnace hot blast stove flue gas extraction system and control method" (CN202010484957) only considers how to extract flue gas from the hot blast stove system, and does not consider how to reuse the hot blast stove.

[0007] Therefore, for the weakening of the convection heat transfer of the middle and lower checker bricks in the hot blast stove caused by the reduction of flue gas amount in the vault temperature insulation heating stage, the existing technology either does not consider it or considers it from the perspective of increasing the air-fuel ratio, which is not conducive to reducing coal gas consumption and reducing cost and increasing efficiency. SUMMARY

[0008] The present application is directed to the problem of uneven distribution of flue gas in the cross section of the hot blast stove caused by the reduction of flue gas amount in the vault temperature insulation heating stage of the internal combustion hot blast stove, which weakens the convection heat transfer of the checker bricks in the hot blast stove. A system and method for improving the heat exchange of internal combustion hot blast stove by flue gas reuse are proposed, which utilizes flue gas reflux to improve the heat exchange, and is conducive to energy saving and consumption reduction of the hot blast stove system.

[0009] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0010] A system for improving the heat exchange of internal combustion hot blast stove by flue gas reuse, comprising a hot blast stove, a flue gas extraction branch pipe, a flue gas extraction main pipe and a chimney, the hot blast stove is connected to a blast furnace through a hot blast pipe, each hot blast stove is connected to the flue gas extraction main pipe through a respective flue gas extraction branch pipe, and the flue gas extraction main pipe is connected to the chimney; an adjusting valve and a check valve are provided on the flue gas extraction branch pipe, a flue gas reuse pipe is led between the adjusting valve and the check valve, the flue gas reuse pipe is connected to the hot blast stove, the connection position is above the coal gas pipe and the combustion air pipe, the flue gas reuse pipe is folded upward after being connected to the hot blast stove and has the same direction as the flame, and the check valve is close to the flue gas extraction main pipe side.

[0011] A swirl vane is provided at the outlet of the flue gas reuse pipe, and the angle of the swirl vane is 5°-20°.

[0012] A flue gas reuse adjusting valve, a flue gas reuse check valve and a flue gas reuse fan are provided on the flue gas reuse pipe, the flue gas reuse adjusting valve is provided close to the flue gas extraction branch pipe, and the flue gas reuse check valve is provided close to the inlet of the flue gas reuse pipe to the hot blast stove body.

[0013] The connection position is 8-20 meters above the coal gas pipe and the combustion air pipe.

[0014] The application discloses a method for improving heat exchange of an internal combustion hot blast stove by using flue gas, and is realized by using a system for improving heat exchange of an internal combustion hot blast stove by using flue gas.

[0015] 1) in the fast heating stage of the hot blast stove burning operation, the adjusting valve and the check valve on the flue gas branch pipe are opened, and the flue gas recycling adjusting valve and the flue gas recycling check valve on the flue gas recycling pipeline are closed, so that the flue gas is prevented from entering the hot blast stove through the flue gas recycling pipeline, meanwhile, the flue gas recycling check valve can also prevent the flue gas in the hot blast stove from being directly discharged to the flue gas main pipeline through the flue gas recycling pipeline; the flue gas flows through the flue gas branch pipe and the flue gas main pipeline and is discharged to the chimney.

[0016] 2) in the dome temperature maintaining and heating stage of the hot blast stove burning operation, when the gas flow is less than 90% of the full load gas flow of the hot blast stove, the adjusting valve and the check valve on the flue gas branch pipe and the flue gas recycling adjusting valve and the flue gas recycling check valve on the flue gas recycling pipeline are opened, and the flue gas recycling adjusting valve is adjusted, so that part of the flue gas flows through the flue gas recycling pipeline into the hot blast stove, mixes with the flue gas in the hot blast stove after the cyclone piece at the outlet of the flue gas recycling pipeline, and the uniformity of the flue gas distribution in the cross section of the hot blast stove is improved.

[0017] In the step 2), when the gas flow is 70% to 90% of the full load gas flow of the hot blast stove, including 70% and excluding 90%, the flue gas recycling adjusting valve is adjusted, so that 5% to 10% of the total flue gas volume flows through the flue gas recycling pipeline into the hot blast stove;

[0018] When the gas flow is 50% to 70% of the full load gas flow of the hot blast stove, including 50% and excluding 70%, the flue gas recycling adjusting valve is adjusted, so that 10% to 15% of the total flue gas volume flows through the flue gas recycling pipeline into the hot blast stove;

[0019] When the gas flow is less than 50% of the full load gas flow of the hot blast stove, the flue gas recycling adjusting valve is adjusted, so that 15% to 20% of the total flue gas volume flows through the flue gas recycling pipeline into the hot blast stove.

[0020] Compared with the prior art, the application has the beneficial effects that:

[0021] The application discloses a system and a method for improving heat exchange of an internal combustion hot blast stove by using flue gas recycling and increasing the total amount of flue gas, the increase of the total amount of flue gas can improve the uniformity of the flue gas distribution in the cross section of the hot blast stove, thereby improving the problem of weakening the convective heat transfer of the checker bricks of the hot blast stove caused by the reduction of the flue gas amount in the dome temperature maintaining and heating stage of the internal combustion hot blast stove, the hot blast temperature can be effectively increased by more than 5 DEG C, and the energy saving and consumption reduction of the hot blast stove system are facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1It is a kind of through smoke back use improves the plane view of internal combustion hot blast stove heat exchange system.

[0023] Fig. 2 It is a kind of through smoke back use improves the side view of internal combustion hot blast stove heat exchange system.

[0024] In the figure: 1, blast furnace; 2, hot blast stove; 3, chimney; 4, hot blast main pipe; 5, hot blast branch pipe; 6, gas pipeline; 7, combustion air pipeline; 8, regulating valve; 9, check valve; 10, smoke back use pipeline; 11, exhaust gas main pipe; 12, exhaust gas branch pipe; 13, smoke back use regulating valve; 14, smoke back use check valve; 15, smoke back use fan. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present application more clear, the specific embodiments of the present application are further described below in combination with examples, the following examples are used to specifically describe the present application, which are only general description of the present application and do not limit the present application.

[0026] As Figs. 1-2 shown, the present application aims to solve the problem of weakening the heat convection of hot blast stove checker bricks caused by the reduction of smoke quantity in the dome insulation heating stage of internal combustion hot blast stove, and proposes a system and method for improving the heat storage and exchange of hot blast stove checker bricks by using smoke back use.

[0027] A kind of through smoke back use improves the system of internal combustion hot blast stove heat exchange, including blast furnace 1, hot blast stove 2 and chimney 3, the hot blast pipe of hot blast stove 2 is connected blast furnace 1, each hot blast stove 2 is connected exhaust gas main pipe 11 by respective exhaust gas branch pipe 12, exhaust gas main pipe 11 is connected chimney 3 again;Regulating valve 8 and check valve 9 are provided on the exhaust gas branch pipe 12, smoke back use pipeline 10 is led between regulating valve 8 and check valve 9, smoke back use pipeline 10 is connected into the hot blast stove 2, and the access position is above gas pipeline 6 and combustion air pipeline 7, after smoke back use pipeline 10 is connected into hot blast stove 2, it is folded and upwards with the same direction of flame, and check valve 9 is close to one side of exhaust gas main pipe 11.

[0028] The outlet of the smoke back use pipeline 10 is provided with a swirl vane, and the angle of the swirl vane is 5°-20°.

[0029] Smoke back use regulating valve 13, smoke back use check valve 14 and smoke back use fan 15 are provided on the smoke back use pipeline 10, wherein smoke back use regulating valve 13 is arranged close to the exhaust gas branch pipe 12, and smoke back use check valve 14 is arranged close to the inlet of the hot blast stove 2.

[0030] The access position is 8-20 meters above the gas pipeline 6 and the combustion air pipeline 7.

[0031] A method for improving the heat exchange of an internal combustion hot blast stove by using flue gas is realized by using the system for improving the heat exchange of an internal combustion hot blast stove by using flue gas, and the specific method is as follows:

[0032] 1) In the rapid heating stage of the hot blast stove operation, open the regulating valve 8 and the check valve 9 on the flue gas branch pipe 12, close the flue gas recycling regulating valve 13 and the flue gas recycling check valve 14 on the flue gas recycling pipe 10, prevent the flue gas from entering the hot blast stove 2 through the flue gas recycling pipe 10, and the flue gas recycling check valve 14 can also prevent the flue gas in the hot blast stove 2 from being directly discharged to the flue gas main pipe 11 through the flue gas recycling pipe 10. The flue gas flows through the flue gas branch pipe 12 and the flue gas main pipe 11 into the chimney 3 for discharge.

[0033] 2) In the dome temperature insulation heating stage of the hot blast stove operation, when the gas flow is less than 90% of the full load gas flow of the hot blast stove, open the regulating valve 8 and the check valve 9 on the flue gas branch pipe 12 and the flue gas recycling regulating valve 13 and the flue gas recycling check valve 14 on the flue gas recycling pipe 10, and adjust the flue gas recycling regulating valve 13 to make part of the flue gas flow through the flue gas recycling pipe 10 into the hot blast stove 2, mix with the flue gas in the hot blast stove 2 after the cyclone piece at the outlet of the flue gas recycling pipe 10, and improve the uniformity of the flue gas distribution in the hot blast stove cross section.

[0034] In the step 2), when the gas flow is 70% to 90% of the full load gas flow of the hot blast stove, including 70% and excluding 90%, adjust the flue gas recycling regulating valve 13 to make 5% to 10% of the total flue gas volume flow through the flue gas recycling pipe 10 into the hot blast stove 2;

[0035] When the gas flow is 50% to 70% of the full load gas flow of the hot blast stove, including 50% and excluding 70%, adjust the flue gas recycling regulating valve 13 to make 10% to 15% of the total flue gas volume flow through the flue gas recycling pipe 10 into the hot blast stove 2;

[0036] When the gas flow is reduced to less than 50% of the full load gas flow of the hot blast stove, adjust the flue gas recycling regulating valve 13 to make 15% to 20% of the total flue gas volume flow through the flue gas recycling pipe 10 into the hot blast stove 2.

[0037] Example 1:

[0038] In the rapid heating stage of the hot blast stove operation, open the regulating valve 8 and the check valve 9 on the flue gas branch pipe 12, close the flue gas recycling regulating valve 13 and the flue gas recycling check valve 14, prevent the flue gas from entering the hot blast stove through the flue gas recycling pipe 10, and the flue gas recycling check valve 14 can also prevent the flue gas in the hot blast stove 2 from being directly discharged to the flue gas main pipe 11 through the flue gas recycling pipe 10. The flue gas flows through the flue gas branch pipe 12, the flue gas main pipe 11 into the chimney 3 for discharge.

[0039] In the arch temperature maintaining heating stage of the hot blast stove operation, when the gas flow is 80% of the full load gas flow of the hot blast stove, the regulating valve 8 and the check valve 9 on the flue gas branch pipe 12 and the flue gas recycling regulating valve 13 and the flue gas recycling check valve 14 are opened, the flue gas recycling regulating valve 13 is adjusted to make 5% of the flue gas flow through the flue gas recycling pipe 10 into the hot blast stove 2, mix with the flue gas in the hot blast stove 2 after the 5° flue gas recycling pipe 10 outlet swirl vane, improve the uniformity of the flue gas distribution in the cross section of the hot blast stove 2, and increase the hot blast temperature by 5°C. The flue gas recycling check valve 14 prevents the low-temperature flue gas in the flue gas main pipe 11 from being sucked into the flue gas recycling pipe 10.

[0040] Example 2:

[0041] In the rapid heating stage of the hot blast stove operation, the regulating valve 8 and the check valve 9 on the flue gas branch pipe 12 are opened, and the flue gas recycling regulating valve 13 and the flue gas recycling check valve 14 are closed to prevent the flue gas from entering the hot blast stove 2 through the flue gas recycling pipe 10. At the same time, the flue gas recycling check valve 14 also prevents the flue gas in the hot blast stove 2 from being directly discharged to the flue gas main pipe 11 through the flue gas recycling pipe 10. The flue gas flows through the flue gas branch pipe 12 and the flue gas main pipe 11 into the chimney 3 for discharge.

[0042] In the arch temperature maintaining heating stage of the hot blast stove operation, when the gas flow is 60% of the full load gas flow of the hot blast stove, the regulating valve 8 and the check valve 9 on the flue gas branch pipe 12 and the flue gas recycling regulating valve 13 and the flue gas recycling check valve 14 are opened, the flue gas recycling regulating valve 13 is adjusted to make 10% of the flue gas flow through the flue gas recycling pipe 10 into the hot blast stove 2, mix with the flue gas in the hot blast stove 2 after the 20° flue gas recycling pipe 10 outlet swirl vane, improve the uniformity of the flue gas distribution in the cross section of the hot blast stove 2, and increase the hot blast temperature by 10°C. The check valve 9 prevents the low-temperature flue gas in the flue gas main pipe 11 from being sucked into the flue gas recycling pipe 10.

[0043] Example 3:

[0044] In the rapid heating stage of the hot blast stove operation, the regulating valve 8 and the check valve 9 on the flue gas branch pipe 12 are opened, and the flue gas recycling regulating valve 13 and the flue gas recycling check valve 14 are closed to prevent the flue gas from entering the hot blast stove 2 through the flue gas recycling pipe 10. At the same time, the flue gas recycling check valve 14 also prevents the flue gas in the hot blast stove 2 from being directly discharged to the flue gas main pipe 11 through the flue gas recycling pipe 10. The flue gas flows through the flue gas branch pipe 12 and the flue gas main pipe 11 into the chimney 3 for discharge.

[0045] In the arch temperature maintaining and heating stage of the hot blast stove operation, when the gas flow is reduced to less than 40% of the full load gas flow of the hot blast stove, the regulating valve 8 and the check valve 9 on the exhaust gas branch pipe 12 and the exhaust gas recycling regulating valve 13 and the exhaust gas recycling check valve 14 are opened, 20% of the exhaust gas flows through the exhaust gas recycling pipe 10 into the hot blast stove 2, mixes with the exhaust gas in the hot blast stove 2 after the 15° exhaust gas recycling pipe 10 outlet swirl vane, improves the uniformity of the exhaust gas distribution in the cross section of the hot blast stove 2, and can increase the hot blast temperature by 20℃. The check valve 9 on the exhaust gas branch pipe 12 prevents the low temperature exhaust gas in the exhaust gas main pipe 11 from being sucked into the exhaust gas recycling pipe 10.

[0046] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A system for improving heat exchange in an internal combustion hot blast stove through flue gas reuse, comprising a hot blast stove, exhaust branch pipes, an exhaust main pipe, and a chimney, wherein the hot blast pipes of the hot blast stoves are connected to a blast furnace, each hot blast stove is connected to the exhaust main pipe via its own exhaust branch pipe, and the exhaust main pipe is then connected to the chimney, characterized in that, A regulating valve and a check valve are provided on the exhaust branch pipe. A flue gas reuse pipe is led out between the regulating valve and the check valve. The flue gas reuse pipe is connected to the hot blast stove of this unit. The connection position is above the gas pipe and the combustion air pipe. After the flue gas reuse pipe is connected to the hot blast stove, it turns upward and is in the same direction as the flame. The check valve is located on the side near the exhaust main pipe.

2. The system for improving heat exchange in an internal combustion hot blast stove by flue gas reuse according to claim 1, characterized in that, A swirl vane is installed at the outlet of the flue gas reuse duct, with an angle of 5° to 20°.

3. A system for improving heat exchange in an internal combustion hot blast stove by reusing flue gas, as described in claim 1, is characterized in that... The flue gas reuse pipeline is equipped with a flue gas reuse regulating valve, a flue gas reuse check valve, and a flue gas reuse fan. The flue gas reuse regulating valve is located near the exhaust branch pipe, and the flue gas reuse check valve is located near the inlet of the flue gas reuse pipeline to the hot blast stove body.

4. A system for improving heat exchange in an internal combustion hot blast stove by reusing flue gas according to claim 1, characterized in that, The connection point is 8 to 20 meters above the gas pipeline and the combustion air pipeline.

5. A method for improving heat exchange in an internal combustion hot blast stove by flue gas reuse, characterized in that, This is achieved using the system described in any one of claims 1-4, which improves the heat exchange of an internal combustion hot blast stove through flue gas reuse. The specific method is as follows: 1) During the rapid heating stage of the hot blast stove operation, open the regulating valve and check valve on the flue gas branch pipe, close the flue gas reuse regulating valve and flue gas reuse check valve on the flue gas reuse pipe, and the flue gas flows through the flue gas branch pipe and the flue gas main pipe into the chimney for discharge. 2) During the dome temperature preservation and heating stage of the hot blast stove operation, when the gas flow rate is less than 90% of the full load gas flow rate of the hot blast stove, open the regulating valve and check valve on the flue gas branch pipe and the flue gas reuse regulating valve and flue gas reuse check valve on the flue gas reuse pipe, and adjust the flue gas reuse regulating valve so that part of the flue gas flows into the hot blast stove through the flue gas reuse pipe. After passing through the swirl vane at the outlet of the flue gas reuse pipe, it mixes with the flue gas in the hot blast stove, thereby improving the uniformity of the distribution of the flue gas in the cross section of the hot blast stove.

6. A method for improving heat exchange in an internal combustion hot blast stove by flue gas reuse according to claim 5, characterized in that, In step 2), when the gas flow rate is 70% to 90% of the full-load gas flow rate of the hot blast stove (including 70% but excluding 90%), the flue gas reuse regulating valve is adjusted so that 5% to 10% of the total flue gas volume flows into the hot blast stove through the flue gas reuse pipe. When the gas flow rate is 50% to 70% of the full-load gas flow rate of the hot blast stove (including 50% but excluding 70%), adjust the flue gas reuse regulating valve so that 10% to 15% of the total flue gas volume flows into the hot blast stove through the flue gas reuse pipe. When the gas flow rate drops to less than 50% of the full-load gas flow rate of the hot blast stove, adjust the flue gas reuse regulating valve so that 15% to 20% of the total flue gas volume flows into the hot blast stove through the flue gas reuse pipe.

Images