A high-efficiency heating furnace using flue gas plus pure oxygen to assist combustion and a combustion control method thereof

Abstract

The invention relates to a high-efficiency heating furnace adopting a flue gas plus pure oxygen combustion-supporting method, comprising a control system and a furnace, wherein a plurality of burners are arranged in the furnace, a hot smoke inlet of a rotary regenerative air preheater is connected with one end of a chimney side wall close to a smoke inlet through a hot smoke duct, a cold smoke outlet of the rotary regenerative air preheater is connected with an inlet of a flue gas induced draft fan through a cold smoke duct 1, an outlet of the flue gas induced draft fan is connected with one end of a chimney side wall close to a smoke outlet through a cold smoke duct 2, a hot air duct is connected with the hot air outlet of the rotary regenerative air preheater, a cold air inlet of the rotary regenerative air preheater is connected with an outlet of a blower through a cold air duct, an inlet of the blower is connected with an outlet of a mixer, an inlet of the mixer is connected with a second cold smoke duct through a circulating smoke duct, a circulating smoke duct is connected with an oxygen pipeline, a circulating smoke duct is connected with an air intake through a bronchus, and the second cold smoke duct is connected with an inlet of a dehydration tank through a carbon dioxide capture process pipeline.

Description

Technical Field

[0001] The invention relates to the field of heating furnaces, in particular to a high-efficiency heating furnace adopting a flue gas plus pure oxygen combustion-assisted method and a combustion control method thereof. Background Art

[0002] At present, most petrochemical heating furnaces use air as a combustion aid. The use of air as a combustion aid is very wasteful, mainly because 79% of the nitrogen in the air does not participate in the combustion when passing through the heating furnace, but absorbs a large amount of heat to form part of the flue gas, which is eventually discharged into the atmosphere; in addition, during the combustion process, in order to ensure the full combustion of the fuel, the combustion aid is generally given an excess coefficient of 1.05~1.15, and the excess combustion aid also takes away a large amount of heat, forming part of the flue gas and discharging it into the atmosphere; in addition, the heat dissipation loss on the surface of the heating furnace equipment is 1.5~3%, and all the wasted heat leads to the inability to further improve the thermal efficiency of the heating furnace. At present, the average thermal efficiency level of domestic petrochemical heating furnaces is about 91~92%.

[0003] Air is used as a combustion aid, and the nitrogen in the air is heated to a high temperature in the combustion area. Nitrogen and oxygen form high-temperature NOx during the combustion process, which is discharged into the atmosphere with the flue gas, causing environmental pollution. Therefore, in response to national and local environmental protection requirements, petrochemical heating furnaces use low NOx technology on burners to reduce pollutant emissions. The core of low NOx technology is to control the flame temperature and inhibit the large-scale generation of thermal NOx. The reduction in flame temperature has a certain impact on the radiation heat transfer efficiency, and the furnace temperature field moves backward, which will cause the overall heat transfer efficiency of the heating furnace to be slightly reduced.

[0004] At present, the exhaust gas temperature of heating furnaces in the petrochemical industry is generally between 110 and 160°C. Based on the 20°C air combustion, according to the empirical formula, the thermal efficiency of the heating furnace decreases by about 1% for every 20°C increase in exhaust gas temperature, which means that 1% more fuel is consumed. The heat taken away by the 79% nitrogen in the air contributes about 3.55% to 5.53% to the decrease in the thermal efficiency of the heating furnace. Excessive exhaust gas volume and high exhaust gas temperature are one of the main reasons why it is difficult to improve the thermal efficiency of the heating furnace. In view of this, we propose a high-efficiency heating furnace and a combustion control method thereof that adopts a flue gas plus pure oxygen combustion method. Summary of the invention

[0005] The purpose of the present invention is to provide a high-efficiency heating furnace using flue gas plus pure oxygen to assist combustion and a combustion control method thereof, so as to solve the problems raised in the above background technology. To achieve the above purpose, the present invention provides the following technical solutions: a high-efficiency heating furnace using flue gas plus pure oxygen to assist combustion, comprising a control system and a furnace with a chimney, wherein a plurality of burners are arranged in the furnace, and further comprising:

[0006] A rotary regenerative air preheater, a chimney baffle is arranged in the middle of the chimney, a hot smoke inlet of the rotary regenerative air preheater is connected to one end of the chimney side wall near the smoke inlet through a hot smoke duct, a cold smoke outlet of the rotary regenerative air preheater is connected to the inlet of a flue gas induced draft fan through a cold smoke duct 1, an outlet of the flue gas induced draft fan is connected to one end of the chimney side wall near the smoke outlet through a cold smoke duct 2, a burner is respectively connected to a fuel gas pipe and a hot air duct, and the hot air duct is connected to the hot air outlet of the rotary regenerative air preheater, a cold air inlet of the rotary regenerative air preheater is connected to the outlet of a blower through a cold air duct, and the inlet of the blower is connected to the outlet of a mixer;

[0007] A mixer, the inlet of the mixer is connected to the second cold flue through a circulating flue, the circulating flue is connected to the oxygen pipeline, and the circulating flue is connected to the air intake through a bronchus;

[0008] Dehydration tank, cold flue 2 is connected to the inlet of the dehydration tank through a carbon dioxide capture process pipeline, and the carbon dioxide capture process pipeline passes through the flue gas cooler.

[0009] Preferably, the hot flue is connected to a hot flue baffle, and the cold flue second is connected to a cold flue baffle.

[0010] Preferably, the oxygen pipeline is connected to an oxygen valve, the circulating flue is connected to a circulating flue baffle, and the bronchus is connected to a cold air baffle.

[0011] Preferably, one end of the carbon dioxide capture process pipeline close to the cold flue 2 is connected to a carbon dioxide valve.

[0012] Preferably, a spiral tube is fixed in the flue gas cooler, and a section of the carbon dioxide capture process pipeline located in the flue gas cooler is connected to the spiral tube.

[0013] Preferably, a bracket is fixed to the upper end wall of the flue gas cooler, and a water pump is fixed on the bracket. A cold water pipe is fixed to and connected to the side wall of the water pump. One end of the cold water pipe is connected to the cold water pool, and the other end is connected to the lower end of the side wall of the flue gas cooler. The upper end of the side wall of the flue gas cooler is connected to the hot water pipe.

[0014] Preferably, the upper end wall of the flue gas cooler is penetrated by and fixedly connected with a shaft sleeve, a sliding rod is inserted into and slidably connected to the shaft sleeve, a connecting rod is fixed to the lower end of the sliding rod, a tube shaft is rotatably connected to the connecting rod, bristles are evenly distributed and fixed on the outer peripheral wall of the tube shaft, and the tube shaft is located at the center of the spiral tube, and the tube shaft and the sliding rod are arranged parallel to each other.

[0015] Preferably, a lifting rod is fixed to the upper end of the slide rod, the lifting rod is connected to the upper end wall of the flue gas cooler through a spring, and a roller is rotatably connected to the lifting rod on a fixed axis.

[0016] Preferably, the upper end wall of the flue gas cooler passes through and is fixedly connected with a shaft sleeve 2, the shaft sleeve 2 is inserted and rotatably connected to the rotating shaft, the lower end of the rotating shaft is coaxially fixedly connected to a polygonal rod, the polygonal rod is inserted into the pipe shaft and can slide up and down in the pipe shaft, the upper end of the rotating shaft is coaxially fixedly connected to the inner side wall of the rotating drum through a frame rod, the upper end surface of the rotating drum is set at 30°-60° with the central axis of the rotating drum, the roller rolls on the upper end surface of the rotating drum, the outer side wall of the rotating drum is sleeved and fixedly connected to a gear ring, the impeller shaft of the water pump is coaxially fixedly connected to the gear, and the gear is meshingly connected to the gear ring.

[0017] A combustion control method for a high-efficiency heating furnace using a flue gas plus pure oxygen combustion-supporting method, comprising:

[0018] Combustion mode 1: air-assisted combustion mode, which is divided into two cases, namely air-assisted combustion mode + flue gas direct exhaust mode / air is not preheated, and air-assisted combustion mode + flue gas direct exhaust mode / air is preheated:

[0019] In the first case, air combustion-supporting mode + flue gas direct exhaust mode, the air is not preheated: the cold flue damper is closed, the hot flue damper is closed, and the chimney damper is opened. During operation, the valve plate opening is adjusted to the appropriate position according to the furnace load, pressure, etc. At this time, the circulating flue damper, the carbon dioxide valve and the oxygen valve are all closed, and the cold air damper is opened. Air is sucked in from the air inlet b of the air intake port, passes through the mixer, and is then sent to the rotary heat storage air preheater through the cold air duct by the blower. In this mode, the rotor of the rotary heat storage air preheater stops running, and the air does not exchange heat when passing through the heat storage body. The cold air is then transported to each burner through the hot air duct for combustion-supporting purposes. The fuel gas enters from the fuel gas inlet e and is sent to each burner for combustion. The flue gas after combustion rises in the furnace of the heating furnace. After radiation and convection heat exchange, the hot flue gas continues to rise and enters the chimney, and is discharged into the atmosphere from the flue gas outlet d at the top of the chimney;

[0020] The second case is air combustion mode + flue gas direct exhaust mode / air is preheated: the cold flue damper is opened, the hot flue damper is opened, and the chimney damper is completely closed. During operation, the opening of the hot flue damper valve plate is adjusted to the appropriate position according to the furnace load, pressure, etc. At this time, the circulating flue damper, carbon dioxide valve and oxygen valve are all closed, the cold air damper is opened, and air is sucked in from the air inlet b of the air intake port, passes through the mixer, and is then sent into the rotary heat storage air preheater by the blower through the cold air duct. The cold air passes through the heat storage body for exchange. The hot air is heated up, and then transported to each burner through the hot air duct to provide combustion support. The fuel gas enters from the fuel gas inlet e and is sent to each burner for combustion. The flue gas after combustion rises in the furnace of the heating furnace. After radiation and convection heat exchange, the hot flue gas continues to rise and enters the lower bypass of the chimney. After passing through the chimney hot flue baffle and the hot flue, it enters the rotary heat storage air preheater for heat exchange. The cooled flue gas passes through the cold flue 1, and then is sent back to the upper part of the chimney by the induced draft fan through the cold flue 2, and is discharged into the atmosphere from the top flue gas outlet d.

[0021] Combustion mode 2: Zero emission mode of carbon dioxide recovery and utilization with flue gas + pure oxygen combustion. This mode uses circulating flue gas mixed with pure oxygen to form a combustion aid with a certain oxygen concentration. The combustion aid is mainly composed of carbon dioxide (about 65-75%), oxygen (about 35-25), and water vapor (a small amount). The flue gas after combustion is mainly composed of carbon dioxide and water vapor; the flue gas after dehydration is mainly composed of carbon dioxide (generally more than 96%) and water vapor. Through capture and concentration for further deep processing, the flue gas is completely recycled and utilized to produce carbon dioxide products, achieving zero emissions.

[0022] The damper of the cold flue is closed, the damper of the hot flue is open, and the damper of the chimney is completely closed. During operation, the opening of the damper valve plate of the hot flue is adjusted to the appropriate position according to the furnace load, pressure, etc. At this time, the circulating flue damper, the carbon dioxide valve and the oxygen valve are all open, and the cold air damper is closed. After combustion, the high-temperature flue gas rises inside the furnace of the heating furnace and undergoes radiation and convection heat exchange. The hot flue gas rises until it is led out of the bypass hot flue at the bottom of the chimney, and then goes down to the rotary heat storage air preheater arranged on the ground for heat exchange. The temperature of the cold flue gas after cooling is generally below ℃. The cold flue gas enters the flue gas induced draft fan from the cold flue one, and is then sent to the cold flue two. The hot flue damper is used to adjust the hot flue gas flow rate and control the furnace pressure.

[0023] The cold flue gas in the second cold flue is divided into two routes. One route enters the circulating flue and is mixed with pure oxygen from the oxygen pipeline. The mixing amount is determined according to needs and adjusted by the oxygen valve. The cold flue gas and pure oxygen are homogenized in the mixer to form a combustion aid, which is then sent to the rotary regenerative air preheater through the cold air duct by the blower for heat exchange. The combustion aid passes through the air-side heat storage bricks of the rotary regenerative air preheater. The combustion aid that has absorbed heat and heated up is then transported to each burner through the hot air duct to supply combustion support. The other route enters the carbon dioxide capture process pipeline, is further cooled by the flue gas cooler, and then enters the dehydration tank to remove moisture. The dehydrated cold flue gas is then sent to the downstream carbon dioxide product capture and utilization process line through the high-concentration carbon dioxide gas outlet c for further processing. As a result, the flue gas and its waste heat from the heating furnace are basically fully recycled, achieving high efficiency, energy saving, and zero emissions.

[0024] Combustion mode three: Flue gas reflow low-nitrogen combustion mode during air-assisted combustion. This mode is to reduce the oxygen concentration of the combustion air appropriately (below 21%) to assist combustion by introducing a part of the flue gas to reflow and mix it into the combustion-supporting air, thereby slowing down the combustion intensity of the burner, reducing the flame temperature, and inhibiting the large-scale generation of thermal NOx, thus achieving flue gas reflow low-nitrogen combustion;

[0025] The damper of the cold flue is open, the damper of the hot flue is open, and the damper of the chimney is completely closed. During operation, the opening of the damper valve plate of the hot flue is adjusted to the appropriate position in real time according to the furnace load, pressure, etc. At this time, the damper of the circulating flue is opened, the carbon dioxide valve is closed, the oxygen valves are all closed, and the cold air damper is opened. Air is sucked in from the air inlet b of the air intake port, merged with the cold flue gas sent from the circulating flue, and then passes through the mixer, and then is sent to the rotary regenerative air preheater for heat exchange through the cold air duct by the blower. The hot air is then transported to each burner through the hot air duct for combustion support. The fuel gas enters from the fuel gas inlet e and is sent to each burner for combustion;

[0026] The flue gas after combustion rises in the furnace of the heating furnace. After radiation and convection heat exchange, the hot flue gas continues to rise and enters the lower bypass of the chimney. After passing through the hot flue baffle of the chimney and the hot flue, it enters the rotary regenerative air preheater for heat exchange. The cooled flue gas passes through the cold flue 1 and then through the cold flue 2 by the induced draft fan. The cold flue gas is divided into two parts. One part is sent back to the upper part of the chimney through the cold flue 2 and discharged into the atmosphere from the top flue gas outlet d. The other part of the cold flue gas passes through the circulating flue baffle and enters the circulating flue, and then is mixed into the cold air.

[0027] Combustion mode four: oxygen-enriched combustion mode of air + pure oxygen, which can also be divided into two cases, namely, oxygen-enriched combustion mode of air + pure oxygen / air without preheating, and oxygen-enriched combustion mode of air + pure oxygen / air passing through a preheater. This mode corresponds to the two cases of the air-assisted combustion mode described in the above combustion mode one. The difference is that during operation, these two cases will open the oxygen valve to a certain degree, so that a certain amount of pure oxygen is mixed into the air, thereby increasing the oxygen concentration in the combustion-assisted air, and the burner performs oxygen-enriched combustion. Under the same operating load conditions, oxygen-enriched combustion can reduce flue gas emissions, increase flame temperature, and achieve certain energy-saving and emission reduction effects.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] In the present invention, pure oxygen is added to the flue gas as a combustion aid, which can completely eliminate the heat dissipation loss of the flue gas formed by excess air and nitrogen in the air in the traditional air-assisted combustion method, thereby improving the thermal efficiency of the heating furnace and reducing fuel consumption; and the heat storage heat exchange technology is used to improve the level of waste heat recovery of low-temperature flue gas, reduce the flue gas to below 80°C for discharge, recover part of the latent heat of vaporization, further improve the thermal efficiency of the heating furnace, and reduce fuel consumption; the thermal efficiency of the heating furnace can be increased to more than 95%, complying with environmental protection policies, and having a strong energy-saving, emission-reduction and efficiency-enhancing effect.

[0030] The present invention adopts hydrocarbon fuel, flue gas plus pure oxygen as combustion aids. The main components of the flue gas after combustion are carbon dioxide and water. The carbon dioxide concentration in the flue gas after cooling and dehydration can reach more than 96%, which can be further recycled as a carbon dioxide product, achieving zero emissions in a certain sense.

[0031] The present invention can be used to transform old furnaces or directly applied to new furnaces. By setting up a process method, the heating furnace can have multiple working modes. It can flexibly maintain a relatively economical operating mode and a high level of energy conservation, emission reduction and efficiency improvement in response to various fuels, various loads and different needs of the heating furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of the present invention;

[0033] Figure 2 It is a schematic diagram of the cross-sectional structure of the flue gas cooler in the present invention;

[0034] Figure 3 for Figure 2 A in the figure is an enlarged structural diagram.

[0035] In the figure: 1. Heating furnace hearth; 2. Burner; 3. Hot air duct; 4. Chimney; 5. Chimney damper; 6. Cold flue damper; 7. Cold flue 2; 8. Control system; 9. Hot flue damper; 10. Hot flue; 11. Rotary regenerative air preheater; 12. Cold flue 1; 13. Flue gas induced draft fan; 14. Cold air damper; 15. Cold air duct; 16. Blower; 17. Mixer; 18. Oxygen valve; 19. Oxygen pipeline; 20. Air inlet; 21. Circulating flue; 22. Circulating flue damper; 23. Carbon dioxide capture process pipeline; 24. Carbon dioxide valve door; 25, flue gas cooler; 26, dehydration tank; 27, cold water pipe; 28, pipe shaft; 29, connecting rod 1; 30, sliding rod; 31, spiral tube; 32, hot water pipe; 33, spring; 34, lifting rod; 35, shaft sleeve 1; 36, shaft sleeve 2; 37, roller; 38, rotating shaft; 39, multi-faceted rod; 40, rack rod; 41, rotating drum; 42, gear ring; 43, bracket; 44, water pump; 45, gear;

[0036] a. Pure oxygen inlet; b. Air inlet; c. High concentration carbon dioxide gas outlet;

[0037] d. Smoke exhaust port e. Fuel gas inlet. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technical personnel in this field without creative work are within the scope of protection of the present invention.

[0039] See also Figures 1 to 3 , the present invention provides a technical solution: Example 1

[0040] A high-efficiency heating furnace using flue gas and pure oxygen to assist combustion, such as Figure 1 As shown, it includes a control system 8 and a furnace 1 with a chimney 4. The control system 8 used in the control of this application may be in the form of a control cabinet in practice, and the control system may also be coupled with a heating furnace DCS control system. A plurality of burners 2 are arranged in the furnace 1, and it also includes:

[0041] Rotary thermal storage air preheater 11, a chimney baffle 5 is arranged in the middle of the chimney 4, the hot smoke inlet of the rotary thermal storage air preheater 11 is connected with one end of the side wall of the chimney 4 close to the smoke inlet through the hot smoke duct 10, the cold smoke outlet of the rotary thermal storage air preheater 11 is connected with the inlet of the flue gas induced draft fan 13 through the cold smoke duct 12, the outlet of the flue gas induced draft fan 13 is connected with one end of the side wall of the chimney 4 close to the smoke outlet through the cold smoke duct 2 7, the burner 2 is connected to the fuel gas pipe and the hot air duct 3 respectively, and the hot air duct 3 is connected to the hot air outlet of the rotary thermal storage air preheater 11, the cold air inlet of the rotary thermal storage air preheater 11 is connected with the outlet of the blower 16 through the cold air duct 15, and the inlet of the blower 16 is connected with the outlet of the mixer 17, the hot smoke duct 10 is connected with the hot smoke duct baffle 9, and the cold smoke duct 2 7 is connected with the cold smoke duct baffle 6;

[0042] A mixer 17, the inlet of the mixer 17 is connected to the cold flue 27 through a circulating flue 21, the circulating flue 21 is connected to the oxygen pipeline 19, the circulating flue 21 is connected to the air inlet 20 through a bronchus, the oxygen pipeline 19 is connected to an oxygen valve 18, the circulating flue 21 is connected to a circulating flue baffle 22, and the bronchus is connected to a cold air baffle 14;

[0043] The dehydration tank 26 and the cold flue 2 7 are connected to the inlet of the dehydration tank 26 through a carbon dioxide capture process pipeline 23, and the carbon dioxide capture process pipeline 23 passes through a flue gas cooler 25. One end of the carbon dioxide capture process pipeline 23 close to the cold flue 2 7 is connected to a carbon dioxide valve 24.

[0044] In the above embodiment, the combustion aid and the fuel gas are respectively transported to each burner 2 through the hot air duct 3 and the fuel gas pipeline, so that the combustion aid and the fuel gas are mixed and burned in the burner 2. The high-temperature flue gas after combustion rises inside the furnace 1 of the heating furnace and undergoes radiation and convection heat exchange. The hot flue gas rises to the bottom of the chimney 4, that is, the lower part of the chimney baffle 5. When the chimney baffle 5 is closed, the hot flue gas is led out by the bypass hot flue 10 at the bottom of the chimney 4, and descends into the rotary heat storage air preheater 11 arranged on the ground for heat exchange. The hot flue gas descends through the heat storage body on the flue gas side of the rotary heat storage air preheater 11, and transfers heat to the heat storage body bricks. The temperature of the cold flue gas after cooling is generally below 80°C. The cold flue gas is sent to the flue gas induced draft fan 13 by the cold flue 12, and then sent to the cold flue 2 7. The hot flue baffle 9 is used to adjust the flow rate of the hot flue gas and control the furnace pressure.

[0045] The second pipe 7 of the cold flue is provided with two bypasses. When the damper 6 of the cold flue is opened, the cold flue gas is directly sent back to the upper part of the chimney 4 and discharged into the atmosphere through the chimney opening.

[0046] When the cold flue damper 6 is closed, the cold flue gas is divided into two paths, one path enters the circulating flue 21, and the other path enters the carbon dioxide capture process pipeline 23. At this time, the circulating flue damper 22 and the carbon dioxide valve 24 are opened, and the valve opening is reasonably adjusted according to needs.

[0047] Two bypass inlets are provided on the circulating flue 21, one is the cold air inlet bypass, and the other is the pure oxygen mixing inlet. The cold air damper 14 is generally in a closed state, and is only opened when the heating furnace adopts the air combustion-supporting mode or the air plus pure oxygen oxygen-enriched mode combustion-supporting operation. The cold flue gas entering the circulating flue 21 is mixed with pure oxygen from the oxygen pipeline 19. The mixing amount is determined according to needs and adjusted by the oxygen valve. The cold flue gas and pure oxygen are homogenized in the mixer 17 to form a combustion-supporting agent, which is then sent to the rotary regenerative air preheater 11 through the cold air duct 15 by the blower 16 for heat exchange. The combustion-supporting agent passes through the air side heat storage bricks of the rotary regenerative air preheater 11. The combustion-supporting agent after absorbing heat and heating is then transported to each burner 2 by the hot air duct 3 for combustion and combustion-supporting use. The cold flue gas entering the carbon dioxide capture process pipeline 23 enters the flue gas cooler 25 for further cooling, and then enters the dehydration tank 26 to remove moisture. The dehydrated cold flue gas is then sent to the downstream carbon dioxide product capture and utilization process line for further processing.

[0048] In this embodiment, the high-temperature flue gas after combustion is subjected to waste heat recovery. The main components of the flue gas after cooling are carbon dioxide and water vapor. A part of the flue gas enters the circulating flue 21, and pure oxygen is added to adjust it to a combustion aid with a suitable oxygen content. The combustion aid is preheated in the rotary regenerative air preheater 11 and then sent to the burner 2 for combustion; the other part of the flue gas after cooling is sent to the flue gas cooler 25 and the dehydration tank 26. The flue gas after dehydration is sent to the dry ice preparation process line. The flue gas is added with pure oxygen to adjust the combustion aid, which basically does not contain nitrogen. The flue gas volume is reduced by more than 75% compared with the air combustion method, which greatly reduces the heat dissipation loss of the flue gas, reduces the fuel consumption of the heating furnace, and improves the thermal efficiency of the heating furnace to more than 95%;

[0049] A dew point corrosion-resistant rotary heat storage air preheater 11 is used to recover the waste heat of the flue gas and preheat the prepared combustion aid, and the exhaust temperature is controlled to below 80°C so as to remove part of the moisture in the reflux flue gas. On the one hand, it is beneficial to recover the latent heat of vaporization and further improve the thermal efficiency of the heating furnace; on the other hand, the circulating flue gas after part of the moisture is removed is adjusted to the combustion aid by adding pure oxygen, which will not condense during transportation in the pipeline, causing dew point corrosion of the air duct or burner equipment. Example 2

[0050] This embodiment is implemented on the basis of embodiment 1, wherein, Figure 2 and Figure 3As shown, a spiral tube 31 is fixed in the flue gas cooler 25, and a section of the carbon dioxide capture process pipeline 23 located in the flue gas cooler 25 is connected to the spiral tube 31, a bracket 43 is fixed to the upper end wall of the flue gas cooler 25, and a water pump 44 is fixed on the bracket 43, a cold water pipe 27 is fixed on the side wall of the water pump 44 and connected, one end of the cold water pipe 27 is connected to the cold water pool, and the other end is connected to the lower end of the side wall of the flue gas cooler 25, and the upper end of the side wall of the flue gas cooler 25 is connected to the hot water pipe 32, and a shaft sleeve 35 is passed through and fixedly connected to the upper end wall of the flue gas cooler 25, and a sliding rod 30 is inserted and slidably connected in the shaft sleeve 35, and a connecting rod 29 is fixed to the lower end of the sliding rod 30, and a pipe shaft 28 is rotatably connected to the connecting rod 29, and bristles are evenly fixed on the outer peripheral wall of the pipe shaft 28, and the pipe shaft 28 is located at the center of the spiral tube 31, and the pipe shaft 28 and the sliding rod 30 are arranged parallel to each other. The upper end of the slide bar 30 is fixed with a lifting rod 34, which is connected to the upper end wall of the flue gas cooler 25 through a spring 33, and a roller 37 is rotatably connected to the lifting rod 34. The upper end wall of the flue gas cooler 25 is penetrated and fixedly connected with a shaft sleeve 26, and a rotating shaft 38 is inserted in the shaft sleeve 26 and rotatably connected with the rotating shaft 38. The lower end of the rotating shaft 38 is coaxially fixedly connected with a multi-faceted rod 39, which is inserted in the pipe shaft 28 and It can slide up and down in the pipe shaft 28. The upper end of the rotating shaft 38 is coaxially fixedly connected to the inner wall of the rotating drum 41 through the frame rod 40. The upper end surface of the rotating drum 41 is set at 30°-60° with the central axis of the rotating drum 41. The roller 37 rolls on the upper end surface of the rotating drum 41. The outer wall of the rotating drum 41 is sleeved and fixedly connected to the ring gear 42. The impeller shaft of the water pump 44 is coaxially fixedly connected to the gear 45, and the gear 45 is meshingly connected to the ring gear 42.

[0051] In the above embodiment, the flue gas enters the spiral tube 31 in the flue gas cooler 25 through the carbon dioxide capture process pipeline 23, and at the same time, the water pump 44 is started by the control system 8, so that the water pump 44 transports the cold water in the cold water pool to the lower end of the flue gas cooler 25 through the cold water pipe 27, and the cold water entering the flue gas cooler 25 increases in temperature after heat exchange with the flue gas in the spiral tube 31, thereby reducing the flue gas temperature and realizing the recovery of the waste heat of the flue gas. The heated hot water is discharged through the hot water pipe 32 and utilized. In this process, the impeller shaft of the water pump 44 drives The gear 45 rotates, causing the gear 45 to drive the drum 41 to rotate through the gear ring 42, thereby causing the drum 41 to drive the shaft 38 to rotate through the frame rod 40, and then causing the shaft 38 to drive the tube shaft 28 to rotate through the polygonal rod 39. The rotation of the tube shaft 28 drives the bristles on its outer peripheral wall to remove scale and the like adhered to the inner and outer walls of the spiral tube 31, thereby ensuring the heat exchange efficiency of the spiral tube 31, improving the efficiency of recovering the waste heat of the flue gas, and reducing the labor intensity of maintenance workers, so as to achieve real-time cleaning of the outer wall of the spiral tube 31 while recovering the heat of the flue gas, saving time and effort.

[0052] As the drum 41 rotates, the lifting rod 34 is driven upward through its upper end surface and the roller 37, so that the lifting rod 34 stretches the spring 33 to obtain a restoring force, and as the lifting rod 34 moves upward, the tube shaft 28 is driven upward through the slide bar 30 and the connecting rod 29. When the upper end of the drum 41 does not apply an upward force to the roller 37, the lifting rod 34 is driven downward and reset under the action of the restoring force of the spring 33, so that the lifting rod 34 drives the tube shaft 28 downward through the slide bar 30 and the connecting rod 29, and so on. The tube shaft 28 drives the bristles to clean the spiral tube 31 through rotation while also moving up and down in a reciprocating manner, so that the bristles also clean the scale and the like on the spiral tube 31 in the up and down directions, thereby greatly improving the cleaning effect and efficiency.

[0053] The combustion control method and advantages of the present invention: The control method of various combustion modes of the high-efficiency heating furnace using flue gas plus pure oxygen combustion-assisted method is as follows:

[0054] Combustion mode 1: air-assisted combustion mode, which is divided into two cases, namely air-assisted combustion mode + flue gas direct exhaust mode / air is not preheated, and air-assisted combustion mode + flue gas direct exhaust mode / air is preheated:

[0055] In the first case, air-assisted combustion mode + flue gas direct exhaust mode, the air is not preheated: the cold flue damper 6 is closed, the hot flue damper 9 is closed, and the chimney damper 5 is opened. During operation, the valve plate opening is adjusted to a suitable position in real time according to the furnace load, pressure, etc. At this time, the circulating flue damper 22, the carbon dioxide valve 24 and the oxygen valve 18 are all closed, the cold air damper 14 is opened, and the air is sucked in from the air inlet b of the air intake port 20, passes through the mixer 17, and then is blown by the blower 16 through the cold air duct. 15 is sent to the rotary regenerative air preheater 11. In this mode, the rotor of the rotary regenerative air preheater 11 stops running, and the air passes through the regenerative body without heat exchange. The cold air is then sent to each burner 2 through the hot air duct 3 to provide combustion support. The fuel gas enters from the fuel gas inlet e and is sent to each burner 2 for combustion. The flue gas after combustion rises in the furnace of the heating furnace. After radiation and convection heat exchange, the hot flue gas continues to rise and enters the chimney 4, and is discharged into the atmosphere from the flue gas outlet d at the top of the chimney 4;

[0056] In the second case, air combustion mode + flue gas direct exhaust mode / air is preheated: the cold flue damper 6 is opened, the hot flue damper 9 is opened, and the chimney damper 5 is completely closed. During operation, the opening of the hot flue damper 9 valve plate is adjusted to a suitable position in real time according to the furnace load, pressure, etc. At this time, the circulating flue damper 22, the carbon dioxide valve 24 and the oxygen valve 18 are all closed, the cold air damper 14 is opened, and air is sucked in from the air inlet b of the air intake 20, passes through the mixer 17, and is then sent into the rotary regenerative air preheater 11 by the blower 16 through the cold air duct 15. The cold air passes through the regenerative air preheater 11. The hot body is heated by heat exchange, and the hot air is then transported to each burner 2 through the hot air duct 3 to provide combustion support. The fuel gas enters from the fuel gas inlet e and is sent to each burner 2 for combustion. The flue gas after combustion rises in the furnace of the heating furnace. After radiation and convection heat exchange, the hot flue gas continues to rise and enters the lower bypass of the chimney 4, and passes through the chimney hot flue baffle 9 and the hot flue 10 to enter the rotary heat storage air preheater 11 for heat exchange. The cooled flue gas passes through the cold flue 1 12, and then is sent back to the upper part of the chimney 4 by the induced draft fan 13 through the cold flue 2 7, and is discharged into the atmosphere from the top flue gas outlet d;

[0057] Combustion mode 2: Zero emission mode of carbon dioxide recovery and utilization with flue gas + pure oxygen combustion. This mode uses circulating flue gas mixed with pure oxygen to form a combustion aid with a certain oxygen concentration. The combustion aid is mainly composed of carbon dioxide (about 65~75%), oxygen (about 35~25), and water vapor (a small amount), and the flue gas after combustion is mainly composed of carbon dioxide and water vapor; the flue gas after dehydration is mainly composed of carbon dioxide (generally more than 96%) and water vapor. Through capture and concentration for further deep processing, the flue gas is completely recycled and utilized to produce carbon dioxide products. Based on the zero emission of carbon dioxide recovery and the full recycling of flue gas waste heat to preheat the combustion aid, the latent heat of vaporization of water vapor in the flue gas is fully recovered, so that the thermal efficiency of the heating furnace is more than 95%, and it is energy-efficient and efficient, achieving "zero emission" in a certain sense;

[0058] The cold flue damper 6 is closed, the hot flue damper 9 is opened, and the chimney damper 5 is completely closed. During operation, the opening of the hot flue damper 9 valve plate is adjusted to a suitable position in real time according to the furnace load, pressure, etc. At this time, the circulating flue damper 22, the carbon dioxide valve 24 and the oxygen valve 18 are all opened, and the cold air damper 14 is closed. The high-temperature flue gas after combustion rises inside the furnace 1 of the heating furnace and undergoes radiation and convection heat exchange. The hot flue gas rises until it is led out of the bypass hot flue 10 at the bottom of the chimney 4, and then goes down to the rotary heat storage air preheater 11 arranged on the ground for heat exchange. The temperature of the cold flue gas after cooling is generally below 80°C. The cold flue gas enters the flue gas induced draft fan 13 from the cold flue 12, and is then sent to the cold flue 2 7. The hot flue damper 9 is used to adjust the hot flue gas flow rate and control the furnace pressure.

[0059] The cold flue gas in the cold flue 27 is divided into two paths. One path enters the circulating flue 21 and is mixed with pure oxygen from the oxygen pipe 19. The mixing amount is determined according to needs and adjusted by the oxygen valve. The cold flue gas and pure oxygen are homogenized in the mixer 17 to form a combustion aid, which is then sent to the rotary regenerative air preheater 11 through the cold air duct 15 by the blower 16 for heat exchange. The combustion aid passes through the air-side heat storage bricks of the rotary regenerative air preheater 11. The combustion aid after absorbing heat and heating is then transported to each burner 2 through the hot air duct 3 to supply combustion and combustion aid. The other path enters the carbon dioxide capture process pipeline 23, is further cooled by the flue gas cooler 25, and then enters the dehydration tank 26 to remove moisture. The dehydrated cold flue gas is then sent to the downstream carbon dioxide product capture and utilization process line through the high-concentration carbon dioxide gas outlet c for further processing. As a result, the flue gas and its residual heat from the heating furnace are basically completely recycled, achieving high efficiency, energy saving and zero emissions.

[0060] Combustion mode three: Flue gas reflow low-nitrogen combustion mode during air-assisted combustion. This mode is to reduce the oxygen concentration of the combustion air appropriately (below 21%) to assist combustion by introducing a part of the flue gas to reflow and mix it into the combustion-supporting air, thereby slowing down the combustion intensity of the burner, reducing the flame temperature, and inhibiting the large-scale generation of thermal NOx, thus achieving flue gas reflow low-nitrogen combustion;

[0061] The cold flue damper 6 is opened, the hot flue damper 9 is opened, and the chimney damper 5 is completely closed. During operation, the opening of the valve plate of the hot flue damper 9 is adjusted to a suitable position in real time according to the furnace load, pressure, etc. At this time, the circulating flue damper 22 is opened, the carbon dioxide valve 24 is closed, and the oxygen valve 18 is closed. The cold air damper 14 is opened, and air is sucked in from the air inlet b of the air intake 20, and merges with the cold flue gas sent from the circulating flue 21, and then passes through the mixer 17, and is then sent to the rotary regenerative air preheater 11 through the cold air duct 15 by the blower 16 for heat exchange. The hot air is then transported to each burner 2 through the hot air duct 3 for combustion support. The fuel gas enters from the fuel gas inlet e and is sent to each burner 2 for combustion.

[0062] The flue gas after combustion rises in the furnace of the heating furnace. After heat exchange by radiation and convection, the hot flue gas continues to rise and enters the lower bypass of the chimney 4. After passing through the chimney hot flue baffle 9 and the hot flue 10, it enters the rotary regenerative air preheater 11 for heat exchange. The cooled flue gas passes through the cold flue 1 12 and then through the cold flue 2 7 by the induced draft fan 13. The cold flue gas is divided into two parts. One part is sent back to the upper part of the chimney 4 through the cold flue 2 7 and discharged into the atmosphere from the top flue gas outlet d. The other part of the cold flue gas passes through the circulating flue baffle 22 and enters the circulating flue 21, and then is mixed into the cold air.

[0063] Combustion mode four: oxygen-enriched combustion mode of air + pure oxygen, which can also be divided into two cases, namely, oxygen-enriched combustion mode of air + pure oxygen / air without preheating, and oxygen-enriched combustion mode of air + pure oxygen / air passing through a preheater. This mode corresponds to the two cases of the air-assisted combustion mode described in the above-mentioned combustion mode one. The difference is that during operation, these two cases will open the oxygen valve 18 to a certain degree, so that a certain amount of pure oxygen is mixed into the air, thereby increasing the oxygen concentration in the combustion-assisted air, and the burner 2 performs oxygen-enriched combustion. Under the same operating load conditions, oxygen-enriched combustion can reduce flue gas emissions, increase flame temperature, and achieve certain energy-saving and emission reduction effects.

[0064] In the present invention, the fuel burned is generally fuel gas or fuel oil, and the main components of the flue gas after combustion are carbon dioxide and water. In addition, depending on the cleanliness of the fuel and the degree of complete combustion, the flue gas may also contain trace amounts of nitrogen, NOx, carbon monoxide, dust, and unburned hydrocarbons. The concentration of carbon dioxide in the flue gas after dehydration is generally above 96%, and can be captured and processed as a product.

[0065] Necessary valves and baffles are set in each branch of the flue and air duct to switch the working mode. According to the combustion-supporting method of the combustion-supporting agent, there are air combustion-supporting mode, flue gas + pure oxygen combustion mode, and air + pure oxygen oxygen-enriched combustion mode, a total of 3 combustion-supporting modes; according to whether the flue gas is recycled, there are flue gas direct discharge mode, zero emission mode with carbon dioxide recycling, and flue gas reflux low-nitrogen combustion mode during air combustion.

[0066] The cases provided in this manual involve the most basic configurations of valves, fans, heat exchangers, etc. In actual applications, there will be more configurations according to the requirements of safety, interlocking control, operation, and automation.

[0067] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0068] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0069] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Claims

1. A high-efficiency heating furnace using a flue gas plus pure oxygen combustion-supporting method, comprising a control system (8) and a furnace (1) with a chimney (4), wherein a plurality of burners (2) are arranged in the furnace (1), characterized in that: Also includes: A rotary regenerative air preheater (11), a chimney baffle (5) is arranged in the middle of the chimney (4), the hot smoke inlet of the rotary regenerative air preheater (11) is connected to an end of the chimney (4) side wall near the smoke inlet through a hot smoke duct (10), the cold smoke outlet of the rotary regenerative air preheater (11) is connected to the inlet of a smoke exhaust fan (13) through a cold smoke duct (12), and the outlet of the smoke exhaust fan (13) is connected to the inlet of a smoke exhaust fan (13) through a cold smoke duct (12). Flue duct 2 (7) is connected to an end of the side wall of the chimney (4) close to the smoke outlet, the burner (2) is respectively connected to the fuel gas pipe and the hot air duct (3), and the hot air duct (3) is connected to the hot air outlet of the rotary regenerative air preheater (11), the cold air inlet of the rotary regenerative air preheater (11) is connected to the outlet of the blower (16) through the cold air duct (15), and the inlet of the blower (16) is connected to the outlet of the mixer (17); A mixer (17), wherein the inlet of the mixer (17) is connected to the second cold flue (7) via a circulating flue (21), the circulating flue (21) is connected to the oxygen pipeline (19), and the circulating flue (21) is connected to the air intake port (20) via a bronchus; A dehydration tank (26), wherein the second cold flue (7) is connected to the inlet of the dehydration tank (26) via a carbon dioxide capture process pipeline (23), and the carbon dioxide capture process pipeline (23) passes through a flue gas cooler (25); A spiral tube (31) is fixed in the flue gas cooler (25), and a section of the carbon dioxide capture process pipeline (23) located in the flue gas cooler (25) is connected to the spiral tube (31). A bracket (43) is fixed to the upper end wall of the flue gas cooler (25), and a water pump (44) is fixed to the bracket (43). A cold water pipe (27) is fixed to the side wall of the water pump (44) and is connected to the side wall. One end of the cold water pipe (27) is connected to a cold water pool, and the other end is connected to the lower end of the side wall of the flue gas cooler (25). The flue gas cooler (25 ) is connected to a hot water pipe (32) at the upper end of the side wall, a shaft sleeve (35) is passed through and fixedly connected to the upper end wall of the flue gas cooler (25), a sliding rod (30) is inserted and slidably connected inside the shaft sleeve (35), a connecting rod (29) is fixed to the lower end of the sliding rod (30), a tube shaft (28) is rotatably connected to the connecting rod (29), bristles are evenly distributed and fixed on the outer peripheral wall of the tube shaft (28), and the tube shaft (28) is located at the center of the spiral tube (31), the tube shaft (28) and the sliding rod (30) are arranged parallel to each other, and the A lifting rod (34) is fixed to the upper end of the slide bar (30), and the lifting rod (34) is connected to the upper end wall of the flue gas cooler (25) through a spring (33). A roller (37) is rotatably connected to the lifting rod (34). A second shaft sleeve (36) passes through and is fixedly connected to the upper end wall of the flue gas cooler (25). A rotating shaft (38) is inserted into and rotatably connected to the second shaft sleeve (36). The lower end of the rotating shaft (38) is coaxially fixedly connected to a multi-faceted rod (39). The multi-faceted rod (39) is inserted into the pipe shaft (28) and is fixedly connected to the pipe shaft (28). The rotating shaft (38) can slide up and down in the pipe shaft (28); the upper end of the rotating shaft (38) is coaxially fixedly connected to the inner side wall of the rotating drum (41) through a frame rod (40); the upper end surface of the rotating drum (41) is arranged at an angle of 30°-60° with the central axis of the rotating drum (41); the roller (37) rolls on the upper end surface of the rotating drum (41); the outer side wall of the rotating drum (41) is sleeved and fixedly connected to a gear ring (42); the impeller shaft of the water pump (44) is coaxially fixedly connected to a gear (45); and the gear (45) is meshingly connected to the gear ring (42).

2. The high-efficiency heating furnace using flue gas plus pure oxygen combustion-supporting method according to claim 1 is characterized in that: The hot flue (10) is connected to a hot flue baffle (9), and the second cold flue (7) is connected to a cold flue baffle (6).

3. The high-efficiency heating furnace using flue gas plus pure oxygen combustion-supporting method according to claim 2 is characterized in that: The oxygen pipeline (19) is connected to an oxygen valve (18), the circulating flue (21) is connected to a circulating flue baffle (22), and the bronchial tube is connected to a cold air baffle (14).

4. The high-efficiency heating furnace using flue gas plus pure oxygen combustion-supporting method according to claim 3 is characterized in that: One end of the carbon dioxide capture process pipeline (23) close to the second cold flue (7) is connected to a carbon dioxide valve (24).

5. A combustion control method for a high-efficiency heating furnace using a flue gas plus pure oxygen combustion-assisted method according to any one of claim 4, characterized in that: Combustion mode 1: air-assisted combustion mode, which is divided into two cases, namely air-assisted combustion mode + flue gas direct exhaust mode / air is not preheated, and air-assisted combustion mode + flue gas direct exhaust mode / air is preheated: In the first case, air-assisted combustion mode + flue gas direct exhaust mode, the air is not preheated: the cold flue damper (6) is closed, the hot flue damper (9) is closed, and the chimney damper (5) is opened. During operation, the valve plate opening is adjusted to a suitable position according to the furnace load, pressure, etc. At this time, the circulating flue damper (22), the carbon dioxide valve (24) and the oxygen valve (18) are all closed, the cold air damper (14) is opened, and the air is sucked in from the air inlet (b) of the air inlet (20), passes through the mixer (17), and then is blown by the blower (16) through the cold air. The hot air is sent to the rotary regenerative air preheater (11) through the hot air duct (15). In this mode, the rotor of the rotary regenerative air preheater (11) stops running, and the air passes through the regenerative body without exchanging heat. The cold air is then sent to each burner (2) through the hot air duct (3) to provide combustion support. The fuel gas enters from the fuel gas inlet (e) and is sent to each burner (2) for combustion. The flue gas after combustion rises in the furnace of the heating furnace. After radiation and convection heat exchange, the hot flue gas continues to rise and enters the chimney (4), and is discharged into the atmosphere from the flue gas discharge port (d) at the top of the chimney (4); The second case is air-assisted combustion mode + flue gas direct exhaust mode / air is preheated: the cold flue damper (6) is opened, the hot flue damper (9) is opened, and the chimney damper (5) is completely closed. During operation, the opening of the hot flue damper (9) valve plate is adjusted to a suitable position according to the furnace load, pressure, etc. At this time, the circulating flue damper (22), the carbon dioxide valve (24) and the oxygen valve (18) are all closed, the cold air damper (14) is opened, and air is sucked in from the air inlet (b) of the air intake port (20), passes through the mixer (17), and is then sent to the rotary regenerative air preheater (11) through the cold air duct (15) by the blower (16). The cold air passes through The heat storage body is heated by heat exchange, and the hot air is then transported to each burner (2) through the hot air duct (3) to provide combustion support. The fuel gas enters from the fuel gas inlet (e) and is transported to each burner (2) for combustion. The flue gas after combustion rises in the furnace of the heating furnace. After radiation and convection heat exchange, the hot flue gas continues to rise and enters the lower bypass of the chimney (4). After passing through the chimney hot flue baffle (9) and the hot flue (10), it enters the rotary heat storage air preheater (11) for heat exchange. The cooled flue gas passes through the cold flue 1 (12) and is then sent back to the upper part of the chimney (4) by the induced draft fan (13) through the cold flue 2 (7) and discharged into the atmosphere from the top flue gas discharge port (d). Combustion mode 2: Zero emission mode of carbon dioxide recovery and utilization with flue gas + pure oxygen combustion. The cold flue damper (6) is closed, the hot flue damper (9) is opened, and the chimney damper (5) is completely closed. During operation, the opening of the hot flue damper (9) valve plate is adjusted to a suitable position in real time according to the furnace load, pressure, etc. At this time, the circulating flue damper (22), the carbon dioxide valve (24) and the oxygen valve (18) are all opened, and the cold air damper (14) is closed. The high-temperature flue gas after combustion is discharged into the combustion chamber. The hot flue gas rises inside the furnace (1) of the heating furnace and undergoes radiation and convection heat exchange. The hot flue gas rises until it is led out through the bypass hot flue (10) at the bottom of the chimney (4), and then goes down to enter the rotary heat storage air preheater (11) arranged on the ground for heat exchange. The temperature of the cooled flue gas is generally below 80°C. The cold flue gas enters the flue gas induced draft fan (13) from the cold flue 1 (12), and is then sent to the cold flue 2 (7). The hot flue damper (9) is used to adjust the hot flue gas flow rate and control the furnace pressure. The cold flue gas in the second cold flue (7) is divided into two paths. One path enters the circulating flue (21) and is mixed with pure oxygen from the oxygen pipe (19). The mixing amount is determined according to needs and is adjusted by the oxygen valve. The cold flue gas and pure oxygen are homogenized in the mixer (17) to form a combustion aid. The combustion aid is then sent to the rotary regenerative air preheater (11) through the cold air duct (15) by the blower (16) for heat exchange. The combustion aid passes through the air side heat storage bricks of the rotary regenerative air preheater (11) and absorbs heat to heat the combustion aid. The fuel is then transported to each burner (2) through the hot air duct (3) to provide combustion support. The other cold flue gas enters the carbon dioxide capture process pipeline (23), is further cooled by the flue gas cooler (25), and then enters the dehydration tank (26) to remove moisture. The dehydrated cold flue gas is then sent to the downstream carbon dioxide product capture and utilization process line through the high-concentration carbon dioxide gas outlet (c) for further processing. As a result, the flue gas and the remaining heat of the heating furnace are basically completely recycled and utilized, achieving high efficiency, energy saving and zero emissions. Combustion mode three: flue gas reflow low nitrogen combustion mode during air-assisted combustion, the cold flue damper (6) is opened, the hot flue damper (9) is opened, and the chimney damper (5) is completely closed. During operation, the opening of the valve plate of the hot flue damper (9) is adjusted to a suitable position in real time according to the furnace load, pressure, etc. At this time, the circulating flue damper (22) is opened, the carbon dioxide valve (24) is closed, and the oxygen valve (18) is closed. The cold air damper (14) is opened, and air is sucked in from the air inlet (b) of the air intake port (20), merged with the cold flue gas sent from the circulating flue (21), and then passes through the mixer (17), and is then sent to the rotary regenerative air preheater (11) through the cold air duct (15) by the blower (16) for heat exchange. The hot air is then transported to each burner (2) through the hot air duct (3) for combustion support. The fuel gas enters from the fuel gas inlet (e) and is sent to each burner (2) for combustion. The flue gas after combustion rises in the furnace of the heating furnace, and after heat exchange by radiation and convection, the hot flue gas continues to rise and enters the lower bypass of the chimney (4), and then passes through the chimney hot flue baffle (9) and the hot flue (10) to enter the rotary heat storage air preheater (11) for heat exchange. The cooled flue gas passes through the cold flue 1 (12), and then passes through the cold flue 2 (7) by the induced draft fan (13). The cold flue gas is split into two parts, one part is sent back to the upper part of the chimney (4) through the cold flue 2 (7), and is discharged into the atmosphere from the top flue gas discharge port (d), and the other part of the cold flue gas passes through the circulating flue baffle (22) into the circulating flue (21), and then is mixed with the cold air. Combustion mode 4: oxygen-enriched combustion mode of air + pure oxygen, which can also be divided into two cases, namely, oxygen-enriched combustion mode of air + pure oxygen / air without preheating, and oxygen-enriched combustion mode of air + pure oxygen / air passing through a preheater. This mode corresponds to the two cases of the air-assisted combustion mode described in the above combustion mode 1. The difference is that during operation, in both cases, the oxygen valve (18) is opened to a certain degree, so that a certain amount of pure oxygen is mixed into the air, thereby increasing the oxygen concentration in the combustion-assisted air, and the burner (2) performs oxygen-enriched combustion. Under the same operating load conditions, oxygen-enriched combustion can reduce smoke emissions, increase flame temperature, and achieve a certain energy-saving and emission reduction effect.

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