A swirl burner for industrial use plasma assisted combustion

Abstract

The application relates to an industrial plasma-assisted combustion swirl burner, belonging to the technical field of gas burners. The swirl burner comprises coaxial circular composite gas conveying pipes formed by a plurality of pipe bodies nested from outside to inside, and a combustion pipe arranged at the exhaust port of the outermost pipe body; a plurality of coaxial annular channels are formed in the composite gas conveying pipe; the annular channels are each provided with a swirl vane; an electrode assembly is arranged in the composite gas conveying pipe; a flow guide assembly is arranged at the exhaust port of the composite gas conveying pipe; and a microwave generating assembly is arranged on the combustion pipe. The low-calorific-value gas and air are fed to the combustion area through the composite gas conveying pipe, the low-calorific-value gas at the center of the burner is ionized through the electrode assembly to generate plasma, the plasma is radially rotated and diffused along the combustion pipe through the flow guide assembly, and the flame is enhanced through the microwave generating assembly, so that the combustion stability is improved and the nitrogen oxide emission amount is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas burners, and particularly relates to a swirl burner for industrial plasma-assisted combustion. BACKGROUND

[0002] Traditional swirl burners are widely used in gas turbines, industrial boilers and combustion furnaces and the like, and the core design thereof is to induce air and fuel to rotate by means of swirl vanes, so as to form a staged combustion mode of a central premixed combustion zone and a peripheral diffusion combustion zone. In the central premixed combustion zone, fuel and air are premixed and then rapidly combusted to release high-temperature heat, and in the diffusion combustion zone, the swirl action is used to realize the full mixing of fuel and combustion-supporting gas. Such a burner performs excellently in the clean combustion of conventional fuels such as natural gas and diesel, and has become the mainstream technology in the field of industrial combustion.

[0003] However, when the traditional swirl burner is applied to low-calorific-value fuels such as ammonia, its performance is significantly limited. The volumetric heat value of ammonia is only 1 / 5 of that of natural gas, which leads to a high ignition temperature, a low combustion rate and weak flame propagation ability, and it is difficult to realize stable combustion under conventional combustion conditions. Specifically, the traditional burner has a low combustion temperature and it is difficult to stabilize the flame. During the combustion process, there are unburned ammonia and intermediate products, which cause fuel waste. In addition, the ammonia combustion process is prone to produce a large amount of NO x x, and it is difficult to control the emission. Although the prior art improves the ammonia combustion performance by optimizing the swirl intensity, adjusting the staged fuel injection or the premixing ratio, etc., it is still limited by the slow chemical kinetic characteristics of ammonia itself, and it is difficult to break through the bottleneck of combustion efficiency and emission. SUMMARY

[0004] The application aims to provide a swirl burner for industrial plasma-assisted combustion to solve the above problems.

[0005] The application achieves the above-mentioned purpose by the following technical solutions:

[0006] The application discloses a swirl burner for industrial plasma-assisted combustion, which comprises a coaxial circular composite gas delivery pipe formed by a plurality of pipe bodies nested from outside to inside, and a combustion pipe arranged at the gas outlet of the outermost pipe body, wherein a plurality of coaxial annular channels are formed in the composite gas delivery pipe, each of which is provided with swirl vanes, the annular channels are used for delivering low-calorific value fuel gas or combustion-supporting gas, and the innermost annular channel is used for delivering low-calorific value fuel gas; an electrode assembly is arranged in the composite gas delivery pipe, and a flow guide assembly is arranged at the gas outlet of the electrode assembly, wherein a circular ring opening is formed between the flow guide assembly and the innermost annular channel; the electrode assembly is used for ionizing the low-calorific value fuel gas in the innermost annular channel to generate plasma; the flow guide assembly is used for making the plasma diffuse radially along the circular ring opening; and a microwave generating assembly for enhancing flame is arranged on the combustion pipe.

[0007] As a further optimization scheme of the application, the pipe bodies are sequentially divided into an outer peripheral air pipe, an outer peripheral fuel gas pipe, a central air pipe and a central fuel gas pipe from outside to inside, the annular channels are divided into an outer peripheral air channel, an outer peripheral fuel gas channel, a central air channel and a central fuel gas channel, the outer peripheral air channel is located between the outer peripheral air pipe and the outer peripheral fuel gas pipe, the outer peripheral fuel gas channel is located between the outer peripheral fuel gas pipe and the central air pipe, the central air channel is located between the central air pipe and the central fuel gas pipe, and the central fuel gas channel is located inside the central fuel gas pipe.

[0008] As a further optimization scheme of the application, the combustion pipe comprises a flame stabilizing expansion pipe and a furnace, the small-diameter end of the flame stabilizing expansion pipe is fixedly arranged at the gas outlet of the outer peripheral air pipe, the large-diameter end of the flame stabilizing expansion pipe is fixedly arranged at the gas inlet of the furnace, and the microwave generating assembly comprises a microwave generator, a microwave antenna one arranged outside the flame stabilizing expansion pipe and a microwave antenna two arranged outside the furnace.

[0009] As a further optimization scheme of the application, the flow guide assembly comprises a positioning column arranged at the center of the gas outlet of the central fuel gas pipe and a flow guide fin arranged at one end of the positioning column, and the electrode assembly comprises an electrode one arranged at the other end of the positioning column and an electrode two arranged on the wall of the central fuel gas pipe.

[0010] As a further optimization scheme of the application, the electrode assembly further comprises an electrode three arranged on the wall of the central air pipe, the electrode two is a high-voltage electrode, an insulating medium layer is arranged outside the high-voltage electrode, and the electrode one and the electrode three are low-voltage electrodes.

[0011] As a further optimization scheme of the application, the flow guide fin is in an inverted conical shape, and the circular ring opening is located between the flow guide fin and the central fuel gas pipe.

[0012] As a further optimization scheme of the present application, the flow guide assembly further comprises a positioning rod penetrating through the electrode one, and a support frame fixedly arranged inside the central gas pipe, and the positioning rod is fixedly arranged between the support frame and the positioning column.

[0013] As a further optimization scheme of the present application, the flow guide assembly further comprises a rotating shaft penetrating through the electrode one and the positioning column, one end of the rotating shaft is fixedly arranged at the axis of the flow guide piece, and a driving blade is arranged outside the rotating shaft, and a turbulence blade is arranged outside the flow guide piece.

[0014] As a further optimization scheme of the present application, the turbulence blade comprises a blade body, a through hole is arranged on the blade body, and a turbulence tooth is arranged inside the through hole.

[0015] As a further optimization scheme of the present application, an electrically conductive ring is fixedly arranged inside the gas inlet of the central gas pipe, the electrically conductive ring and the electrode one are both in rotational connection with the rotating shaft, and an electrically conductive roller is arranged between the rotating shaft and the electrically conductive ring and the electrode one.

[0016] The present application has the following beneficial effects:

[0017] 1) In the present application, the electrode assembly ionizes ammonia, and ionizes and splits ammonia and air in the central gas pipe, so as to generate free radicals such as NH, NH2, H, O, O3 and various excited state substances, which can accelerate the energy exchange between plasma active substances and fuel, accelerate the chemical kinetics process of combustion, stabilize the combustion of ammonia, and improve the combustion temperature and combustion efficiency;

[0018] 2) The microwave generator of the flared outer periphery generates microwave discharge, which is focused by the antenna and acts on the central flame, so that the ammonia which is difficult to burn completely is fully burned, and the microwave emitted by the microwave generating device of the outer periphery of the furnace uniformly acts on the combustion tail gas, thereby reducing the NOx emissions caused by incomplete combustion; x

[0019] 3) The present application forms a central stable combustion zone and a peripheral diffusion combustion zone at the outlet area of the burner through two-stage air and ammonia grading, the central stable combustion zone adopts fuel-rich combustion to provide a stable stable flame, and the peripheral diffusion combustion zone relies on the swirling vanes to realize stable combustion. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of the overall structure of the swirling burner of the first embodiment of the present application;

[0021] Figure 2 is a schematic diagram of the internal structure of the swirling burner of the first embodiment of the present application;

[0022] Figure 3 is Figure 2 an enlarged view of position A in FIG. 1; ​

[0023] Figure 4 is Figure 2 is an enlarged view of B in FIG. 1;

[0024] Figure 5 is a schematic diagram of a split structure of a composite gas conveying pipe of the first embodiment of the present application;

[0025] Figure 6 is a schematic diagram of an overall structure of a swirl burner of the second embodiment of the present application;

[0026] Figure 7 is a schematic diagram of an internal structure of a swirl burner of the second embodiment of the present application;

[0027] Figure 8 is Figure 7 is an enlarged view of C in FIG. 2;

[0028] Figure 9 is a schematic diagram of a split structure of a composite gas conveying pipe of the second embodiment of the present application;

[0029] Figure 10 is Figure 9 is an enlarged view of D in FIG. 3.

[0030] In the figure: 1, composite gas conveying pipe; 2, combustion pipe; 3, swirl vane; 4, electrode assembly; 5, flow guide assembly; 6, microwave generating assembly; 7, driving vane; 8, turbulence vane; 11, peripheral air pipe; 12, peripheral gas pipe; 13, central air pipe; 14, central gas pipe; 21, stable combustion expansion pipe; 22, furnace; 23, waveguide; 31, vane one; 32, vane two; 33, vane three; 34, vane four; 41, electrode one; 42, electrode two; 43, electrode three; 51, positioning column; 52, flow guide fin; 53, positioning rod; 54, support frame; 55, rotating shaft; 56, conductive ring; 57, conductive roller; 61, microwave antenna one; 62, microwave antenna two; 81, vane body; 82, through hole; 83, turbulence tooth; O, circular ring opening. DETAILED DESCRIPTION

[0031] It is necessary to point out here that the following detailed description is only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0032] First embodiment

[0033] As Figures 1-5The embodiment relates to a swirl burner for industrial plasma-assisted combustion, which comprises four tubes arranged from outside to inside, the four tubes are an outer peripheral air tube 11, an outer peripheral gas tube 12, a central air tube 13 and a central gas tube 14 arranged coaxially, and the four tubes jointly form a coaxial circular composite gas conveying tube 1. The composite gas conveying tube 1 is internally provided with multiple coaxial annular channels, the annular channels are divided into an outer peripheral air channel, an outer peripheral gas channel, a central air channel and a central gas channel. The outer peripheral air channel is located between the outer peripheral air tube 11 and the outer peripheral gas tube 12, the outer peripheral gas channel is located between the outer peripheral gas tube 12 and the central air tube 13, the central air channel is located between the central air tube 13 and the central gas tube 14, and the central gas channel is located inside the central gas tube 14. A combustion tube 2 is fixedly arranged at an exhaust port of the outer peripheral air tube 11, the combustion tube 2 comprises a stable combustion expansion tube 21 in the shape of a bell mouth and a hearth 22, a small-diameter end of the stable combustion expansion tube 21 is fixedly arranged at the exhaust port of the outer peripheral air tube 11, and a large-diameter end of the stable combustion expansion tube 21 is fixedly arranged at an air inlet of the hearth 22. An angle between the expansion opening of the stable combustion expansion tube 21 and the axis of the outer peripheral air tube 11 ranges from 30° to 60°. A swirl vane 3 is arranged in each annular channel, an electrode assembly 4 is arranged inside the composite gas conveying tube 1, and a flow guide assembly 5 is arranged at an exhaust port of the electrode assembly 4, a circular ring opening O is formed between the flow guide assembly 5 and the central gas channel, and a microwave generating assembly 6 is arranged outside the combustion tube 2.

[0034] When the burner works, low-calorific value gas is combusted in a two-stage combustion mode. The low-calorific value gas is introduced into the outer peripheral gas channel and the central gas channel, and air is introduced into the outer peripheral air channel and the central air channel. The low-calorific value gas in the central gas channel is ionized by the electrode assembly 4 to generate plasma. In the embodiment, the low-calorific value gas is ammonia, and the plasma generated after the ammonia is ionized contains NH2, NH, H, O, O3 and other free radicals and various excited state substances, which promote the combustion reaction kinetics process.

[0035] The center of the stable combustion expansion tube 21 is a central stable combustion zone of a central flame, the outer side of the central stable combustion zone is a diffusion combustion zone of a diffusion flame, air is introduced into the burner through the outer peripheral air channel and the central air channel, the ammonia introduced into the central gas channel generates plasma, the plasma is mixed with the air introduced into the central air channel and combusted to form the central flame, the ammonia introduced into the outer peripheral gas channel is mixed with the air introduced into the outer peripheral air channel to form the diffusion flame, and part of the plasma is added to the diffusion combustion zone of the diffusion flame to improve the combustion effect of the diffusion flame. The plasma in the central flame and the diffusion flame is enhanced by the microwave generating assembly 6, so that the ammonia is stably combusted. The plasma is diffused along the circular ring opening O in the radial direction by the flow guide assembly 5, so that the plasma is fully mixed with the air and the ammonia.

[0036] Specifically, the flow guide assembly 5 includes a positioning column 51 arranged at the center of the exhaust port of the central gas pipe 14, and a flow guide vane 52 arranged at one end of the positioning column 51. A plurality of vane I 31 are arranged in the outer peripheral air passage, and the two ends of the vane I 31 are fixedly arranged on the inner wall of the outer peripheral air pipe 11 and the outer wall of the outer peripheral gas pipe 12, respectively. A plurality of vane II 32 are arranged in the outer peripheral gas passage, and the two ends of the vane II 32 are fixedly arranged on the inner wall of the outer peripheral gas pipe 12 and the outer wall of the central air pipe 13, respectively. A plurality of vane III 33 are arranged in the central air passage, and the two ends of the vane III 33 are fixedly arranged on the inner wall of the central air pipe 13 and the outer wall of the central gas pipe 14, respectively. The two ends of the vane IV 34 are fixedly arranged on the inner wall of the central gas pipe 14 and the outer wall of the positioning column 51, respectively. The number of vanes of the vane I 31 is 12-16, the deflection angle of the vane I 31 relative to the axis of the outer peripheral air pipe 11 is between 30°-50°, the number of vanes of the vane II 32 is 12-18, the deflection angle of the vane II 32 relative to the axis of the outer peripheral gas pipe 12 is between 35°-50°, the number of vanes of the vane III 33 is 10-16, the deflection angle of the vane III 33 relative to the axis of the central air pipe 13 is between 30°-60°, the number of vanes of the vane IV 34 is 10-18, and the deflection angle of the vane IV 34 relative to the axis of the central gas pipe 14 is between 35°-60°.

[0037] The flow guide vane 52 is inverted conical, and a circular ring opening O is located between the flow guide vane 52 and the central gas pipe 14. The electrode assembly 4 includes an electrode I 41 fixedly arranged at the other end of the positioning column 51, and an electrode II 42 fixedly arranged on the pipe wall of the central gas pipe 14. The electrode I 41 is a low-voltage electrode, and the electrode II 42 is a high-voltage electrode. An insulating medium layer is sleeved outside the high-voltage electrode, the material of the insulating medium layer is quartz glass, and the thickness of the insulating medium layer is 0.5 mm. The flow guide assembly 5 further includes a positioning rod 53 penetrating the electrode I 41, and a support frame 54 fixedly arranged inside the central gas pipe 14. The positioning rod 53 is fixedly arranged between the support frame 54 and the positioning column 51, the electrode I 41 and the positioning column 51 are fixedly arranged relative to each other, the materials of the positioning rod 53 and the positioning column 51 are high-temperature-resistant and insulating silicon nitride ceramics, and the electrode I 41 is made of stainless steel material.

[0038] Further, the electrode assembly 4 further includes an electrode III 43 fixedly arranged on the pipe wall of the central air pipe 13, and the electrode III 43 is a low-voltage electrode. The discharge action between the electrode II 42 and the electrode III 43 can ionize the air between the central air pipe 13 and the central gas pipe 14, further increase the free radicals and various excited state substances in the burner, and make the combustion more sufficient. The nanosecond pulse power supply provides power support for the high-voltage electrode and the low-voltage electrode, the output voltage of the nanosecond pulse power supply is 0-32 kV, the maximum discharge frequency is 50 kHz, and the pulse width is 12 ns.

[0039] The microwave generating assembly 6 comprises a microwave generator, a microwave antenna one 61 arranged outside the stable combustion expansion pipe 21, and a microwave antenna two 62 arranged outside the furnace 22. The microwave antenna one 61 is preferably a parabolic antenna, which can focus microwave energy on the center flame root with an action diameter of about several centimeters, and generate energy to make the center flame more stable, thereby achieving the purpose of stable combustion of ammonia. The microwave antenna two 62 is used to dissociate the NOx generated after the ammonia is burned in the furnace 22. x The microwave frequency of the microwave power supply is 2.45 GHz, and the microwave plasma energy wave can provide 0-1000 W.

[0040] The stable combustion expansion pipe 21 is made of a material that is resistant to high temperature, heat-insulating, and microwave-transparent. The angle between the flared end of the stable combustion expansion pipe 21 and the axis of the outer peripheral air pipe 11 is between 30° and 60°, and the length of the flared end of the stable combustion expansion pipe 21 is 1-3 times the length of the outer peripheral air pipe 11. In addition, the stable combustion expansion pipe 21 and the side wall of the furnace 22 are provided with waveguides 23 corresponding to the microwave antenna one 61 and the microwave antenna two 62, respectively. The waveguides 23 are made of a material that is resistant to high temperature, heat-insulating, and microwave-transparent, and are in the shape of a column, arranged vertically to the axis of the outer peripheral air pipe 11, thereby reducing microwave loss.

[0041] Second embodiment

[0042] As shown in Figures 6-10 , the present embodiment discloses another swirl burner for industrial plasma-assisted combustion. The difference between the present embodiment and the previous embodiment is that the flow guide assembly 5 is composed of a positioning column 51, a flow guide sheet 52, a rotating shaft 55, a conductive ring 56, and a conductive roller 57. The flow guide sheet 52 of the present embodiment is the same as that of the previous embodiment. The positioning column 51 is hollow. The rotating shaft 55 is made of a conductive material. The rotating shaft 55 penetrates the electrode one 41 and the positioning column 51, and is fixedly arranged at the axis of the flow guide sheet 52 at one end. The outer side of the rotating shaft 55 is provided with a driving blade 7, and the outer side of the flow guide sheet 52 is provided with a turbulence blade 8. The turbulence blade 8 comprises a blade body 81, a through hole 82 is formed in the blade body 81, and a turbulence tooth 83 is arranged on the inner side of the through hole 82. The conductive ring 56 is fixedly arranged on the inner side of the gas inlet of the center gas pipe 14. The conductive ring 56 and the electrode one 41 are both in rotational connection with the rotating shaft 55, and the rotating shaft 55 is provided with the conductive roller 57 between the conductive ring 56 and the electrode one 41. The rotating shaft 55 connects the electrode two 42 and the conductive ring 56 in an electrically conductive manner through the conductive roller 57, thereby ensuring that the electrode assembly 4 can continuously and stably ionize ammonia.

[0043] When the center gas passage is connected to the ammonia gas, the ammonia gas drives the rotating shaft 55 to rotate through the driving blades 7, so that the rotating shaft 55 drives the guide vanes 52 and the turbulence blades 8 to rotate, and the turbulence blades 8 increase the turbulence and vortex in the plasma, so that the plasma is fully mixed with the air and the ammonia gas. The through holes 82 and the turbulence teeth 83 are arranged on the turbulence blades 8, which reduces the weight of the blade body 81, further increases the turbulence and vortex, and improves the effect of the plasma-assisted ammonia gas combustion.

[0044] The above-described embodiments only express several embodiments of the present application, which are described in a more specific and detailed manner, but cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which are within the protection scope of the present application.

Claims

1. A swirl burner for industrial use of plasma assisted combustion, comprising a coaxial circular composite gas delivery tube (1) formed by a plurality of tube bodies nested one inside the other from the outside, and a combustion tube (2) provided at the exhaust port of the outermost tube body, characterized in that: The composite gas conveying pipe (1) is internally formed with a plurality of coaxial annular channels, each of which is provided with a cyclone vane (3), and the annular channels are used for conveying low-calorific-value fuel gas or combustion-supporting gas, and the innermost annular channel is used for conveying low-calorific-value fuel gas. The composite gas conveying pipe (1) is internally provided with an electrode assembly (4), and the exhaust port thereof is provided with a flow guide assembly (5), and a circular ring opening is formed between the flow guide assembly (5) and the innermost annular channel, the electrode assembly (4) is used for ionizing the low-calorific-value fuel gas in the innermost annular channel to generate plasma, and the flow guide assembly (5) is used for making the plasma radially diffuse along the circular ring opening, and the combustion pipe (2) is provided with a microwave generating assembly (6) for enhancing the flame.

2. The plasma-assisted combustion swir! burner for industrial use according to claim 1, characterized in that: The pipe body is sequentially divided into an outer peripheral air pipe (11), an outer peripheral fuel gas pipe (12), a central air pipe (13) and a central fuel gas pipe (14) from outside to inside.

3. The plasma-assisted combustion swir! burner for industrial use according to claim 2, characterized in that: The combustion pipe (2) comprises a flame stabilizing expansion pipe (21) and a hearth (22), the small-diameter end of the flame stabilizing expansion pipe (21) is fixedly arranged at the exhaust port of the outer peripheral air pipe (11), and the large-diameter end of the flame stabilizing expansion pipe (21) is fixedly arranged at the air inlet of the hearth (22), and the microwave generating assembly (6) comprises a microwave generator, a microwave antenna one (61) arranged outside the flame stabilizing expansion pipe (21) and a microwave antenna two (62) arranged outside the hearth (22).

4. The plasma-assisted combustion swir! burner for industrial use according to claim 2, characterized in that: The flow guide assembly (5) comprises a positioning column (51) arranged at the center of the exhaust port of the central fuel gas pipe (14) and a flow guide vane (52) arranged at one end of the positioning column (51), and the electrode assembly (4) comprises an electrode one (41) arranged at the other end of the positioning column (51) and an electrode two (42) arranged on the pipe wall of the central fuel gas pipe (14).

5. The plasma-assisted combustion swir! burner for industrial use according to claim 4, characterized in that: The electrode assembly (4) further comprises an electrode three (43) arranged on the pipe wall of the central air pipe (13), the electrode two (42) is a high-voltage electrode, and an insulating medium layer is arranged outside the high-voltage electrode, and the electrode one (41) and the electrode three (43) are low-voltage electrodes.

6. The plasma-assisted combustion swir! burner for industrial use according to claim 4, characterized in that: The flow guide vane (52) is in an inverted conical shape, and the circular ring opening is located between the flow guide vane (52) and the central fuel gas pipe (14).

7. The plasma-assisted combustion swir! burner for industrial use according to claim 4, characterized in that: The flow guide assembly (5) further comprises a positioning rod (53) penetrating through the electrode one (41) and a support frame (54) fixedly arranged inside the central fuel gas pipe (14), and the positioning rod (53) is fixedly arranged between the support frame (54) and the positioning column (51).

8. The plasma-assisted combustion swir! burner for industrial use according to claim 4, characterized in that: The flow guide assembly (5) further comprises a rotating shaft (55) penetrating through the electrode one (41) and the positioning column (51), one end of the rotating shaft (55) is fixedly arranged at the axis of the flow guide vane (52), a driving vane (7) is arranged outside the rotating shaft (55), and a turbulence vane (8) is arranged outside the flow guide vane (52).

9. The plasma-assisted combustion swir! burner for industrial use according to claim 8, characterized in that: The turbulence vane (8) comprises a vane body (81), a through hole (82) is formed in the vane body (81), and a turbulence tooth (83) is arranged inside the through hole (82).

10. The plasma-assisted combustion swir! burner for industrial use according to claim 8, characterized in that: The center gas pipe (14) is provided with a conductive ring (56) inside the air inlet, the conductive ring (56) and the electrode (41) are both connected with the rotating shaft (55), and the rotating shaft (55) is provided with a conductive roller (57) between the conductive ring (56) and the electrode (41).

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