Multi-stage rotational flow staged oxygen-enriched combustion system capable of achieving low NOx emission

Abstract

The invention provides a multi-stage rotational flow staged oxygen-enriched combustion system capable of realizing low NOx emission, which comprises an oxygen-enriched combustion boiler, and a recirculation fan, a flue gas purification device, a desulfurization tower and a combustor which are respectively connected with the oxygen-enriched combustion boiler, the combustor comprises a primary air channel and a secondary air channel which are sequentially arranged in a sleeved mode from inside to outside, an outlet of the primary air channel and an outlet of the secondary air channel face the oxygen-enriched combustion boiler, and the secondary air channel has a double-rotational-flow adjusting function. The cyclone secondary air channel has the beneficial effects that the cyclone strength of air flow at the outlet of the secondary air channel is ensured through the gradual shrinking structure and the cyclone blades of the cyclone secondary air channel, the fullness of the boiler can be improved, high-temperature flue gas can be entrained, the mixing of coal and surrounding gas can be enhanced, the gasification effect of pulverized coal can be enhanced, in addition, the temperature field distribution can be uniform, and the generation of thermal NOx can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of oxygen-enriched combustion, in particular to a method for achieving low NO x Emission multi-stage swirl graded oxygen-enriched combustion system. Background Art

[0002] Oxygen-enriched combustion technology changes the oxidant air in traditional combustion to a mixture of oxygen and recycled flue gas, achieving CO2 capture during the combustion process, and is considered one of the most commercially promising carbon dioxide capture technologies. In addition, oxygen-enriched combustion technology, with its unique combustion mechanism, changes the traditional O2 / N2 combustion atmosphere to an O2 / CO2 combustion atmosphere, achieving efficient carbon dioxide enrichment in the exhaust gas while also actively suppressing nitrogen oxide emissions. By reducing the amount of nitrogen introduced during the combustion process, thermal NO x At the same time, the high concentration of CO2 in the O2 / CO2 atmosphere reacts with H to generate CO, which will change the O / H / OH composition ratio, enhance the reducing property of the reaction atmosphere, and inhibit the formation of NOx during coal combustion. x emissions.

[0003] Under current technical conditions, although there are oxygen-enriched combustion devices that can achieve flue gas recirculation, given that thermal power generation units are in a state of high pressure and low energy consumption, the x In order to further improve the combustion efficiency, achieve clean and stable combustion, and significantly reduce NO in the thermal power field, the existing oxygen-enriched combustion device still has room for improvement. x Therefore, the technical personnel in this field are committed to providing a multi-stage swirl graded oxygen-enriched combustion system, which can effectively control NO in the combustion process while maintaining efficient burnout. x At the same time, it can also achieve high-concentration CO2 enrichment in the flue gas and reduce the cost of carbon capture by condensation and compression of the tail flue gas. Summary of the Invention

[0004] In order to overcome the above problems in the prior art, the present invention provides a method for achieving low NO x Emission multi-stage swirl graded oxygen-enriched combustion system.

[0005] The present invention discloses a method for achieving low NO xThe multi-stage swirl graded oxygen-enriched combustion system for emission includes an oxygen-enriched combustion boiler and a recirculation fan, flue gas purification equipment, a desulfurization tower and a burner respectively connected thereto. The oxygen-enriched combustion boiler is provided with an array injection device. The burner includes a primary air channel and a secondary air channel sequentially arranged from the inside out. The outlets of the primary air channel and the secondary air channel face the oxygen-enriched combustion boiler. The secondary air channel has a dual swirl regulation function. The flue gas purification equipment is respectively connected to the primary air channel, the secondary air channel and the array injection device through pipelines. The coal bunker is connected to the primary air channel. A coal powder metering device is provided on the coal bunker. The pure oxygen channel is respectively connected to the array injection device, the primary air channel and the secondary air channel through pipelines.

[0006] On this basis, the secondary air channel is divided into a swirl secondary air channel and a DC secondary air channel, into which oxygen, circulating flue gas from an oxygen-enriched combustion boiler, or a mixture of oxygen and circulating flue gas from an oxygen-enriched combustion boiler is introduced to maintain oxygen deficiency at the burner outlet, thereby forming a coal gasification reaction or a low-oxygen combustion atmosphere; and a swirl blade is arranged at the end of the channel, and a swirl adjusting rod is provided on the swirl blade. The inlet section of the swirl secondary air channel adopts a tapered tube design, aiming to ensure that the airflow entering the swirl secondary air channel is in a swirl state, and the first-level swirl intensity is adjustable by adjusting the swirl secondary air inlet flow rate and the DC secondary air inlet flow rate; the second-level swirl intensity is adjustable by adjusting the axial swirl blade angle through the swirl adjusting rod.

[0007] On this basis, the cross sections of the primary air channel and the secondary air channel are circular.

[0008] On this basis, the primary air pulverized coal airflow formed by the mixture of the pulverized coal flowing down from the coal bunker and the primary air from the primary air channel and the injection gas of the array injection device come from a mixture of oxygen and the circulating flue gas of the oxygen-enriched combustion boiler, and the swirl secondary air and the direct current secondary air are introduced into the mixture of oxygen, the circulating flue gas of the oxygen-enriched combustion boiler or the circulating flue gas of oxygen and the oxygen-enriched combustion boiler.

[0009] On this basis, when the burner equivalence ratio is greater than 1, a low-oxygen pulverized coal gasification reaction atmosphere is formed in the burner outlet area; when the array injection device equivalence ratio is less than 1, an oxygen-rich coke combustion atmosphere is formed in the boiler burnout area, ensuring efficient burnout of coke; the array injection device can provide 3*3, 4*4 or 5*5 array injection holes, oxygen or boiler circulating flue gas is uniformly gradient-fed, and the temperature field of the burnout area is uniformly graded to avoid nitrogen oxide emissions caused by local excessive temperature.

[0010] On this basis, the outlet of the flue gas purification equipment is respectively connected to the primary air channel, the swirl secondary air channel, the DC secondary air channel and the array injection device.

[0011] On this basis, an air preheater is provided between the oxygen-enriched combustion boiler and the dust collector, a recirculation fan is provided between the dust collector and the flue gas purification equipment, and the outlet of the dust collector is connected to the desulfurization tower.

[0012] On this basis, the desulfurization tower is connected to the recirculation fan and the chimney through pipelines.

[0013] On this basis, the coal-oxygen combustion boiler is equipped with a low-temperature superheater, an economizer and a denitrification device.

[0014] On this basis, the oxygen-enriched combustion boiler is further provided with a platen superheater, a final stage superheater and a high-temperature reheater.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The present invention ensures the swirl intensity of the airflow at the outlet of the secondary air channel through the tapered structure of the swirl secondary air channel and the swirl blades, thereby improving the boiler filling degree, sucking in high-temperature flue gas, strengthening the mixing of coal and surrounding gas, and enhancing the coal powder gasification effect. In addition, it can also evenly distribute the temperature field and reduce thermal NO x generate;

[0017] (2) In the present invention, a high-temperature mixed gas of oxygen and circulating flue gas is introduced into the primary air inlet, swirl secondary air inlet, and DC secondary air inlet of the burner. By regulating the ratio of oxygen and circulating flue gas, an oxygen-deficient atmosphere is achieved, which is beneficial for the gasification of pulverized coal before combustion, and reduces NO x The oxygen-enriched combustion boiler array injection device is located on the side wall of the burnout zone, providing a mixed gas with a higher oxygen concentration, forming an oxygen-enriched condition, uniform temperature field distribution, promoting complete combustion of coal, and reducing nitrogen oxide emissions;

[0018] (3) The present invention adopts a segmented air supply method, firstly using low-oxygen primary air and strong turbulent secondary air to strengthen coal pulverization and reduce combustion NO x The present invention can achieve high-concentration CO2 enrichment in flue gas, reduce the carbon capture cost of tail flue gas condensation and compression, and effectively control NO in the combustion process while ensuring the burnout effect. x emission. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of the multi-stage swirl graded oxygen-enriched combustion system of the present invention;

[0020] Figure 2 It is a schematic diagram of the burner structure of the present invention;

[0021] Figure 3 This is a schematic diagram of the axial structure of the swirl blade of the present invention;

[0022] Figure 4 Schematic diagram of the structure of the array injection device of the present invention;

[0023] Figure 5 It is the tapered structure of the swirl secondary air channel of the present invention.

[0024] In the figure: 1-platen superheater, 2-final superheater, 3-high-temperature reheater, 4-low-temperature superheater, 5-economizer, 6-denitrification device, 7-air preheater, 8-dust collector, 9-desulfurization tower, 10-chimney, 11-recirculation fan, 12-flue gas purification equipment, 13-burner, 14-array injection device, 15-primary air duct, 16-swirl secondary air duct, 17-DC secondary air duct, 18-swirl blade, 19-swirl adjustment lever, 20-coal bunker, 21-pulverized coal metering device, 22-pure oxygen duct. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] The present invention discloses a method for achieving low NO x Emission multi-stage swirl staged oxygen-enriched combustion system, reference Figure 1-Figure 5 , including an oxygen-enriched combustion boiler and a recirculation fan 11, a flue gas purification device 12, a desulfurization tower 9 and a burner 13 respectively connected thereto. The oxygen-enriched combustion boiler is provided with an array injection device 14. The burner 13 includes a primary air channel 15 and a secondary air channel sequentially arranged from the inside to the outside. The outlets of the primary air channel 15 and the secondary air channel face the oxygen-enriched combustion boiler. The secondary air channel has a double swirl adjustment function. The flue gas purification device 12 is respectively connected to the primary air channel 15, the secondary air channel and the array injection device 14 through pipelines. The coal bunker 20 is connected to the primary air channel 15. A pulverized coal metering device 21 is provided on the coal bunker 20. The pure oxygen channel 22 is respectively connected to the array injection device 14, the primary air channel 15 and the secondary air channel through pipelines.

[0027] The secondary air channel is divided into a swirl secondary air channel 16 and a DC secondary air channel 17 , and swirl blades 18 are arranged at the ends of the channels.

[0028] The cross sections of the primary air channel 15 and the secondary air channel are circular.

[0029] The primary air pulverized coal flow and the injection gas of the array injection device 14 come from a mixture of oxygen and circulating flue gas from an oxygen-enriched combustion boiler, and the swirl secondary air and the direct current secondary air are fed with oxygen, circulating flue gas from an oxygen-enriched combustion boiler or a mixture of oxygen and circulating flue gas from an oxygen-enriched combustion boiler.

[0030] When the equivalence ratio of the burner 13 is greater than 1, a low-oxygen pulverized coal gasification reaction atmosphere is formed in the outlet area of the burner 13. When the equivalence ratio of the array injection device 14 is less than 1, an oxygen-rich coke combustion atmosphere is formed in the boiler burnout area.

[0031] The outlet of the flue gas purification device 12 is connected to the primary air channel 15, the swirl secondary air channel 16, the DC secondary air channel 17 and the array injection device 14 respectively.

[0032] An air preheater 7 is provided between the oxygen-enriched combustion boiler and the dust collector 8 , a recirculation fan 11 is provided between the dust collector 8 and the flue gas purification equipment 12 , and the outlet of the dust collector 8 is connected to the desulfurization tower 9 .

[0033] The desulfurization tower 9 is connected to the recirculation fan 11 and the chimney 10 through pipelines.

[0034] The coal-oxygen combustion boiler is provided with a low-temperature superheater 4 , an economizer 5 and a denitrification device 6 .

[0035] The oxygen-enriched combustion boiler is also provided with a platen superheater 1, a final stage superheater 2 and a high-temperature reheater 3.

[0036] The working principle of the present invention is: when the multi-stage swirl graded oxygen-enriched combustion system operates normally, the primary air carries the coal powder from the primary air channel 15 into the burner 13, and the secondary air enters the burner 13 and the boiler combustion chamber from the swirl secondary air channel 16 and the DC secondary air channel 17; the coal is gasified in an oxygen-deficient environment and then completely burned in the oxygen-rich atmosphere created by the array injection device 14, and the generated gas passes through the screen superheater 1, the final superheater 2 and the high-temperature reheater 3 in the oxygen-enriched combustion boiler in sequence, and then passes through the low-temperature superheater 4 and the economizer 5, and then enters the denitrification device 6, and the flue gas after denitrification enters the air preheater 7.

[0037] The obtained tail gas first passes through the dust collector 8 for electrostatic dust removal, and then passes through the desulfurization tower 9 to obtain relatively pure flue gas, and 10%-20% of the high-temperature flue gas is extracted for recycling.

[0038] After this part of high-temperature flue gas passes through the recirculation fan 11 and the flue gas purification equipment 12, 30% is passed into the primary air channel 15, carrying coal powder into the furnace, and at the same time it can also preheat the coal and promote the pyrolysis and gasification of the coal; 70% is passed into the swirl secondary air channel 16 and the DC secondary air channel 17, and the remaining recycled flue gas enters the boiler through the array injection device 14; the remaining flue gas is discharged into the atmosphere after passing through the chimney 10.

[0039] In this way, not only the emission of pollutants is reduced, but also the efficiency of energy utilization is improved.

[0040] A mixture of coal, oxygen and circulating flue gas from an oxygen-enriched combustion boiler is introduced into the primary air channel 15. The coal is preheated by the high-temperature flue gas, which is beneficial to the pre-decomposition of the coal. An oxygen-deficient atmosphere can also be achieved by regulating the ratio of oxygen and circulating flue gas, thereby suppressing the formation of thermal NO. x and fuel-type NO x At the same time, it further promotes the coal gasification reaction, is beneficial to the decomposition of complex organic pollutants in coal (such as tar, phenols, polycyclic aromatic hydrocarbons, etc.), avoids the formation of incomplete combustion products (such as coke or sticky tar), reduces the risk of boiler coking and slagging, and improves operational safety.

[0041] The secondary air channel is connected to the swirl secondary air channel 16, the DC secondary air channel 17, the swirl blade 18 and the swirl adjustment rod 19 in sequence. Oxygen, recycled flue gas from the oxygen-enriched combustion boiler, or a mixture of oxygen and recycled flue gas from the oxygen-enriched combustion boiler can be introduced from the inlet pipe to maintain oxygen deficiency at the burner outlet to form a coal gasification reaction or low-oxygen combustion atmosphere. Figure 5 The swirl secondary air utilizes the tapered structure of the swirl secondary air channel 16 to achieve swirl, and then mixes with the DC secondary air introduced into the DC secondary air channel 17. By adjusting the ratio of the swirl secondary air and the DC secondary air, a first-level swirl is formed. At the same time, the swirl blade 18 can be regulated by the swirl regulating rod 19 to adjust its swirl intensity, which can further adjust the swirl intensity of the airflow at the outlet of the secondary air channel to form a second-level swirl. The enhanced swirl wind can achieve the entrainment and mixing of high-temperature flue gas. On the one hand, it can fully mix the gasification products with the combustion-supporting materials to improve the subsequent combustion efficiency. On the other hand, it can evenly distribute the temperature field in the oxygen-poor combustion zone and reduce thermal NO. x generate.

[0042] In this embodiment, the array injection device 14 is located on the side wall of the burnout zone, with the front and rear walls facing each other. This ensures a stable flame shape and uniform furnace temperature distribution, promotes mixing of fuel and combustion aids, avoids localized oxygen deficiency or fuel-rich zones, and improves combustion efficiency. The gas injected by the array injection device 14 is a mixture of oxygen and circulating flue gas from the oxy-combustion boiler, creating an oxygen-rich environment, ensuring complete coke burnout, uniform temperature distribution, and reducing nitrogen oxide emissions.

[0043] The multi-stage cyclone graded oxygen-enriched combustion system uses oxygen and recycled flue gas from the oxygen-enriched combustion boiler as the combustion support. The recycled flue gas carries a certain amount of heat, and as a high-temperature combustion support, it helps reduce fuel consumption and promotes coal gasification and decomposition. The recycled flue gas comes from the exhaust gas generated by the oxygen-enriched combustion boiler. The exhaust gas first passes through the denitrification device 6 to remove nitrogen oxides from the flue gas. The denitrified flue gas then passes through the air preheater 7 and enters the dust collector 8 for electrostatic dust removal. After passing through the desulfurization tower 9, a relatively pure high-temperature flue gas is obtained. Part of the flue gas is extracted and recirculated into the combustion system, reducing particulate matter, heavy metals, and SO in the recycled flue gas. x and NO xcontent, reducing the new sulfur pollution and fuel-type NO during cyclic combustion x The CO2 and H2O in the recycled flue gas help maintain furnace temperature uniformity, especially when the wall flame fluctuates or extinguishes during low-load operation.

[0044] In the description of the present invention, it should be understood that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0045] In the present invention, unless otherwise clearly stipulated and limited, the terms "install", "set", "connect", "fix", "screw", "place" and other terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0046] The foregoing description shows and describes preferred embodiments of the present invention. As previously mentioned, it should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the inventive concept described herein by the teachings above or by techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims

1. A method to achieve low NO x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: The invention comprises an oxygen-enriched combustion boiler and a recirculation fan (11), a flue gas purification device (12), a desulfurization tower (9) and a burner (13) respectively connected thereto. The oxygen-enriched combustion boiler is provided with an array injection device (14). The burner (13) comprises a primary air channel (15) and a secondary air channel which are sequentially arranged from the inside to the outside. The outlets of the primary air channel (15) and the secondary air channel face the oxygen-enriched combustion boiler. The secondary air channel has a double swirl regulating function. The flue gas purification device (12) is respectively connected to the primary air channel (15), the secondary air channel and the array injection device (14) through pipelines. A coal bunker (20) is connected to the primary air channel (15). A pulverized coal metering device (21) is provided on the coal bunker (20). A pure oxygen channel (22) is respectively connected to the array injection device (14), the primary air channel (15) and the secondary air channel through pipelines.

2. Achieving low NO according to claim 1 x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: The secondary air channel is divided into a swirl secondary air channel (16) and a DC secondary air channel (17), and a swirl blade (18) is arranged at the end of the channel. A swirl regulating rod (19) is provided on the swirl blade (18).

3. Achieving low NO according to claim 1 x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: The cross sections of the primary air channel (15) and the secondary air channel are circular.

4. The method of claim 1 for achieving low NO x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: The primary air pulverized coal airflow formed by the mixture of the pulverized coal flowing down from the coal bunker (20) and the primary air from the primary air channel (15) and the injection gas from the array injection device (14) comes from a mixture of oxygen and circulating flue gas from an oxygen-enriched combustion boiler, and the swirl secondary air and the direct current secondary air are introduced with oxygen, circulating flue gas from an oxygen-enriched combustion boiler or a mixture of oxygen and circulating flue gas from an oxygen-enriched combustion boiler.

5. The method for achieving low NO according to claim 1 x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: When the burner (13) equivalence ratio is greater than 1, a low-oxygen coal powder gasification reaction atmosphere is formed in the burner (13) outlet area, and when the array injection device (14) equivalence ratio is less than 1, an oxygen-rich coke combustion atmosphere is formed in the boiler burnout area.

6. The method for achieving low NO according to claim 2 x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: The outlet of the flue gas purification device (12) is respectively connected to the primary air channel (15), the swirl secondary air channel (16), the DC secondary air channel (17) and the array injection device (14).

7. The method for achieving low NO according to claim 1 x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: An air preheater (7) is provided between the oxygen-enriched combustion boiler and the dust collector (8), a recirculation fan (11) is provided between the dust collector (8) and the flue gas purification equipment (12), and the outlet of the dust collector (8) is connected to the desulfurization tower (9).

8. The method for achieving low NO according to claim 7 x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: The desulfurization tower (9) is connected to a recirculation fan (11) and a chimney (10) through pipelines.

9. The method for achieving low NO according to claim 1 x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: The coal-oxygen-combustion boiler is provided with a low-temperature superheater (4), an economizer (5) and a denitrification device (6).

10. The method for achieving low NO according to claim 1 x The multi-stage swirl graded oxygen-enriched combustion system is characterized by: The oxygen-enriched combustion boiler is further provided with a platen superheater (1), a final superheater (2) and a high-temperature reheater (3).

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