Double Venturi flue gas internal circulation low nitrogen combustion device and combustion method

Abstract

The present invention discloses a dual-Venturi flue gas internal circulation low-nitrogen combustion device and a combustion method. The device comprises a multi-layer throat, a flue gas internal circulation suction port is provided on the outer wall of the multi-layer throat, a flue gas internal circulation device is arranged in the multi-layer throat cavity, the flue gas internal circulation device is docked with the flue gas internal circulation suction port, the outlet of the multi-layer throat is a high-speed mixed gas channel, the combustion-supporting air channel and the fuel gas channel are arranged in the multi-layer throat cavity, and the front end of the fuel gas channel is a spray gun extending out of the outlet of the multi-layer throat. Therefore, a flue gas internal circulation type low-nitrogen combustion device is realized, which can suck the peripheral flue gas near the throat into the throat internal / external air delivery area, mix with the combustion-supporting air and then participate in the combustion function, so as to achieve low-nitrogen combustion and reduce the generation of NOx.

Description

Technical Field

[0001] The invention relates to the field of gas combustion, and in particular to a double-Venturi flue gas internal circulation low-nitrogen combustion device and a combustion method. Background Art

[0002] Nitrogen oxides (NOx) contained in the exhaust gas emitted by boilers that use fossil resources such as natural gas, coal, and oil as fuel are a recognized air pollutant. For this reason, functional departments have formulated increasingly stringent exhaust gas emission standards to strictly control it. Now, standard requirements have been introduced that natural gas NOx emissions must be reduced to 60mg or even below 30mg / Nm3.

[0003] The industry generally adopts the method of installing low-nitrogen combustion technology devices on existing boilers and carrying out low-nitrogen transformation to meet standards, and has found that appropriately reducing the flame temperature during fuel combustion and the oxygen content of the combustion gas can significantly reduce the amount of NOx generated. For gas boilers that use high calorific value gases such as natural gas as fuel, a low-nitrogen route of low-nitrogen burner + flue gas external circulation is currently adopted, in which the flue gas external circulation is achieved by guiding part of the flue gas with relatively low temperature and oxygen content to be discharged from the tail of the boiler back to the furnace to participate in mixed combustion.

[0004] However, it is found in practice that when the boiler adopts external circulation of flue gas, external circulation components including smoke circulation fans and smoke circulation pipes must be added to the boiler in order to guide part of the flue gas to be discharged to specific positions of the burner and boiler-related components. The installation is relatively troublesome and the modification cost is also high. In addition, due to the temperature difference between the relatively low-temperature flue gas and the normal-temperature combustion air during the working process, condensed water will be produced when mixed. In addition to the extra energy loss when the water evaporates, it will also cause corrosion to the surrounding components, and also lead to the disadvantages of large daily maintenance workload and high daily use costs. Therefore, from the perspective of practicality and economy, it is not ideal. Summary of the invention

[0005] The purpose of the present invention is to provide a double-Venturi flue gas internal circulation low-nitrogen combustion device and a combustion method to reduce the emission of easily polluting nitrogen oxides.

[0006] In order to solve the above technical problems, according to a first aspect of the present invention, a dual-Venturi flue gas internal circulation low-nitrogen combustion device is provided, comprising:

[0007] A multi-layer throat, wherein a smoke internal circulation suction port is provided on the outer wall of the multi-layer throat, a smoke internal circulation device is arranged in the multi-layer throat cavity, and the smoke internal circulation device is connected to the smoke internal circulation suction port, the outlet of the multi-layer throat is a high-speed mixed gas channel, the combustion-supporting air channel and the fuel gas channel are arranged in the multi-layer throat cavity, and the front end of the fuel gas channel is a spray gun, which extends out of the outlet of the multi-layer throat.

[0008] Optionally, the gas channel further includes a connected gas pipe and a commingled air inlet end, the spray gun includes a central spray gun and a peripheral spray gun, and the commingled air inlet end connects the central spray gun and the peripheral spray gun.

[0009] Optionally, the multi-level throat includes an inner throat at the front end of the throat, a middle throat located near the front end of the throat, and an outer throat located near the rear end of the throat.

[0010] Optionally, the main body of the inner throat port is cylindrical, and an inner end surface of the inner throat port is provided at the front end; the main body of the middle throat port is in the shape of a shrinking cylinder, and a middle inner end surface is provided at the front end; the main body of the outer throat port is cylindrical, and a shrinking inner end surface of the outer throat port is provided at the front end, and the smoke internal circulation suction port is provided on the outer wall of the main body of the outer throat port; the middle throat port is matched and arranged between the inner throat port and the outer throat port.

[0011] Optionally, the area between the outer wall of the main body of the external throat and the gas channel serves as a combustion-supporting air channel.

[0012] Optionally, the high-speed mixed gas channel includes a first high-speed mixed gas channel formed by a gap between an inner end surface of the outer throat and an inner end surface of the middle throat, and a second high-speed mixed gas channel formed by a gap between an inner end surface of the middle throat and an inner end surface of the inner throat.

[0013] Optionally, a flame stabilizing device is provided on the inner end surface of the inner throat, the main body of the flame stabilizing device is disc-shaped, and a flame stabilizing wind channel and cooling wind through holes are provided on the flame stabilizing device.

[0014] Optionally, the flue gas internal circulation device is fixed on the external throat, and includes: a smoke channel whose main body is composed of a horizontal smoke gas inlet ring and a longitudinal smoke gas outlet ring connected and interconnected, and a Venturi-type combustion-supporting air duct composed of a tapered pipe and a straight pipe interspersed and fixed on the smoke channel.

[0015] Optionally, the smoke channel has an L-shaped cross-section, and is composed of two upper and lower circular plates, and the upper and lower circular plates are in a contracted shape.

[0016] According to a second aspect of the present invention, there is provided a combustion method, comprising:

[0017] The spray gun sprays fuel gas, and the combustion air channel sprays combustion air;

[0018] The smoke internal circulation inlet generates negative pressure, sucking the peripheral smoke into the multi-layer throat cavity;

[0019] The high-speed mixed gas channel generates negative pressure, sucking the peripheral smoke back to the nozzle;

[0020] The combustion air in the combustion-supporting air channel is mixed with the peripheral flue gas sucked in during the forward process, and the high-speed mixed flue gas is diverged and sprayed at the outlet of the multi-level throat to become oxygen-poor combustion gas, which enters the furnace and participates in low-nitrogen combustion.

[0021] In the dual-Venturi flue gas internal circulation low-nitrogen combustion device and combustion method provided by the present invention, the device includes a multi-layer throat, a flue gas internal circulation suction port is opened on the outer wall of the multi-layer throat, a flue gas internal circulation device is arranged in the multi-layer throat cavity, the flue gas internal circulation device is docked with the flue gas internal circulation suction port, the outlet of the multi-layer throat is a high-speed mixed gas channel, the combustion-supporting air channel and the fuel gas channel are arranged in the multi-layer throat cavity, and the front end of the fuel gas channel is a spray gun extending out of the outlet of the multi-layer throat. Therefore, a flue gas internal circulation low-nitrogen combustion device is realized, which can suck the peripheral flue gas near the throat into the throat internal / external air delivery area, mix with the combustion-supporting air, and then participate in the combustion function, so as to achieve low-nitrogen combustion and reduce the generation of NOx. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of a dual venturi flue gas internal circulation low nitrogen combustion device according to an embodiment of the present invention Figure 1 ;

[0023] Figure 2 for Figure 1 AA cross section diagram Figure 2 ;

[0024] Figure 3 A schematic diagram of a flue gas internal circulation device according to an embodiment of the present invention;

[0025] Figure 4 for Figure 3 Schematic diagram of the A direction;

[0026] Figure 5 Schematic diagram of the combustion process of an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following will be described in more detail with reference to the schematic diagram of the dual venturi flue gas internal circulation low nitrogen combustion device and the combustion method of the present invention, wherein the preferred embodiment of the present invention is shown, and it should be understood that those skilled in the art can modify the present invention described herein and still achieve the advantageous effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation of the present invention.

[0028] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to facilitate and clearly assist in illustrating the purpose of the embodiments of the present invention.

[0029] In the following description, it should be understood that the reference about 'inside' and 'outside' of each structure may be made based on the drawings.

[0030] Example 1

[0031] This embodiment 1 provides a dual Venturi flue gas internal circulation low nitrogen combustion device. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Figure 1 As shown, the dual-Venturi flue gas internal circulation low-nitrogen combustion device comprises:

[0032] A multi-layer throat, wherein a flue gas internal circulation suction port 132 is provided on the outer wall of the multi-layer throat, a flue gas internal circulation device 6 is arranged in the multi-layer throat cavity, and the flue gas internal circulation device 6 is connected to the flue gas internal circulation suction port 132, the outlet of the multi-layer throat is a high-speed mixed gas channel, the combustion-supporting air channel 4 and the gas channel 3 are arranged in the multi-layer throat cavity, and the front end of the gas channel 3 is a spray gun 2, which extends out of the outlet of the multi-layer throat.

[0033] The embodiment of the present invention is a flue gas internal circulation low-nitrogen combustion device with the function of sucking peripheral flue gas near the throat into the inner / outer air delivery area of ​​the throat and mixing it with combustion-supporting air to participate in combustion.

[0034] Example 2

[0035] This embodiment 2 provides a dual-Venturi flue gas internal circulation low-nitrogen combustion device, which can be further optimized or improved on the basis of embodiment 1. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention. Please continue to refer to Figure 1-Figure 5 As shown, this embodiment 2 includes:

[0036] The gas channel 3 further includes a connected gas pipe 31 and a commutated gas inlet end, and the spray gun 2 includes a central spray gun 21 and a peripheral spray gun 22, and the commutated gas inlet end connects the central spray gun and the peripheral spray gun.

[0037] The commutated air inlet end may include a plurality of “L” shaped structures, one end of which is connected together and connected to the gas pipe 31 , and the other end is connected to the spray paint 2 .

[0038] The spray holes of the peripheral spray gun 22 can be set as needed, and can be set to spray axially or radially.

[0039] The gas pipe 31 can be a gas pipe connected to a gas supply main.

[0040] The multi-level throat includes an inner throat 11 at the front end of the throat, a middle throat 12 near the front end of the throat, and an outer throat 13 near the rear end of the throat. Figure 5 , the outer throat 13 is close to the furnace wall 7.

[0041] In this embodiment, the main body of the inner throat port 11 is cylindrical, and an inner throat inner end face 111 is provided at the front end; the main body of the middle throat port 12 is in the shape of a shrinking cylinder, and a middle throat inner end face 121 is provided at the front end; the main body of the outer throat port 13 is cylindrical, and an outer throat contraction inner end face 131 is provided at the front end, and the smoke internal circulation suction port 132 is provided on the outer wall of the main body of the outer throat port 13; the middle throat port 12 is matched and arranged between the inner throat port 11 and the outer throat port 13.

[0042] Preferably, the inner throat opening 11, the middle throat opening 12 and the outer throat opening 13 are coaxially arranged.

[0043] The gas channel 3 is fixedly arranged at the axial center position of the multi-layer throat.

[0044] The area between the outer wall of the main body of the external throat 13 and the gas channel 3 serves as the combustion-supporting air channel 4 , that is, it is performed by the throat cavity ring 41 located at the periphery of the gas pipe 31 .

[0045] A flame stabilizing device 5 is provided at the front end of the inner throat 11. The flame stabilizing device 5 is disc-shaped, and is provided with a flame stabilizing air passage 51 and a cooling air through hole 52. The flame stabilizing air passage 51 is in the shape of a straight hole or a swirl with a certain inclination. The flame stabilizing air passage 51 and the cooling air through hole 52 can be evenly arranged.

[0046] The high-speed mixed gas passage 8 includes a first high-speed mixed gas passage 81 formed by a gap between the inner end surface 131 of the outer throat and the inner end surface 121 of the middle throat, and a second high-speed mixed gas passage 82 formed by a gap between the inner end surface 121 of the middle throat and the inner end surface 111 of the inner throat.

[0047] Furthermore, the middle throat inner end surface 121 and the outer throat inner end surface 131 may be configured as a telescopic structure, so that the sizes of the first high-speed mixed gas passage 81 and the second high-speed mixed gas passage 82 can be adjusted.

[0048] The smoke internal circulation device 6 is fixed on the outer throat 13, please refer to Figure 3 and Figure 4 ,in, Figure 3 For along Figure 1 The partial cross-sectional view of BB includes: a smoke channel 61 whose main body is formed by the intersection and interconnection of a horizontal smoke inlet ring 611 and a longitudinal smoke outlet ring 612, and a Venturi-type combustion-supporting air duct 62 which is coaxially interconnected by a tapered pipe 621 and a straight pipe 622 inserted and fixed on the smoke channel 61.

[0049] Preferably, the smoke channel 61 has an L-shaped cross-section, and is composed of two upper and lower circular plates 631 and 632 , and the upper and lower circular plates 631 and 632 are in a contracted shape.

[0050] The straight-through pipe 622 may be arranged on the cavity wall where the horizontal smoke inlet ring 611 and the longitudinal smoke outlet ring 612 are interconnected.

[0051] Example 3

[0052] This embodiment 3 provides a combustion method, which can be based on the device described in any one of embodiments 1 or 2, and may not be limited to such devices. The embodiments described below are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention. This embodiment 3 includes:

[0053] A combustion method, comprising:

[0054] The spray gun sprays fuel gas, and the combustion air channel sprays combustion air;

[0055] The smoke internal circulation inlet generates negative pressure, sucking the peripheral smoke into the multi-layer throat cavity;

[0056] The high-speed mixed gas channel generates negative pressure, sucking the peripheral smoke back to the nozzle;

[0057] The combustion air in the combustion-supporting air channel is mixed with the peripheral flue gas sucked in during the forward process, and the high-speed mixed flue gas is diverged and sprayed at the outlet of the multi-level throat to become oxygen-poor combustion gas, which enters the furnace and participates in low-nitrogen combustion.

[0058] This embodiment can significantly reduce the oxygen content in the combustion gas, and is beneficial to the uniform distribution of the combustion flame in the furnace and reduces the probability of generating local high-temperature points, thereby ensuring the realization of low-oxygen and low-nitrogen combustion that effectively suppresses the generation of NOx, and providing technical guarantee for the boiler to meet the standard transformation.

[0059] Example 4

[0060] This embodiment 4 provides a combustion method, which can be an optimization or improvement based on embodiment 3. The embodiments described below are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention. Figure 1-5 , this embodiment 3 includes:

[0061] During operation, fuel gas is delivered by the fuel gas pipe 31 and supplied to each spray gun 2; combustion-supporting air enters from the rear end of the outer throat 13 and flows forward in the combustion-supporting air channel 4, most of which is gradually accelerated forward at the periphery of the flue gas internal circulation device 6, and a small part is aligned with the port of the tapered tube 621 of the Venturi-type combustion-supporting air duct 62, flows in, is accelerated by the contraction flow of the tapered tube 621 to become a high-speed airflow, and then flows out through the straight pipe 622 and enters the longitudinal flue gas outlet ring 612. A negative pressure is generated in the longitudinal flue gas outlet ring 612, which can generate suction for the horizontal flue gas inlet ring 611, and the flue gas around the outer throat 13 is sucked into the longitudinal flue gas outlet ring 612, mixed with the high-speed combustion-supporting air from the straight pipe 622, and then enters the combustion-supporting air channel 4, where it converges with the majority of the gradually accelerated combustion-supporting air to form a preliminary mixed flue gas flow with a certain flow rate.

[0062] Most of the combustion-supporting air flows through the periphery of the flue gas internal circulation device 6, that is, after being guided by the contraction of the lower contraction ring plate 632, this part of the air is rapidly accelerated and flows out axially at high speed at the outlet end face of the lower contraction ring plate 632, thereby forming a negative pressure for the longitudinal flue gas outlet ring channel 612, sucking in the flue gas outside the external throat 13, and mixing with it.

[0063] The preliminary mixed flue gas flow with a certain flow rate continues to flow forward, most of which enters the middle throat 12 section, and a small part enters the first high-speed mixed gas channel 81 and is ejected at high speed, forming a negative pressure zone near the nozzle, so that the flue gas outside the outer throat 13 of the combustion device is sucked back to the vicinity of the front end face 131 of the outer throat, and mixed with the small part of the preliminary mixed flue gas flow ejected from the first high-speed mixed gas channel 81, and then low-oxygen and low-nitrogen combustion is carried out. Most of the preliminary mixed flue gas flows that enter the middle throat port 12 section are further accelerated and moved forward when passing through the expanding and contracting cylinder of the middle throat port 12. A part of the flue gas flows that enter the second high-speed mixed gas channel 82 are ejected at high speed, forming a negative pressure zone near the nozzle, so that the flue gas outside the middle throat port 12 of the combustion device is sucked back to the vicinity of the front end surface 121 of the middle throat port, and after mixing with the preliminary mixed flue gas flow ejected from the second high-speed mixed gas channel 82, low-oxygen and low-nitrogen combustion is carried out; another part of the flue gas flows that enter the inner throat port 11 section continue to move forward to the inner side of the flame stabilizing device 5 and is blocked Flow limiting, when flowing through the flame stabilizing wind channel 51 and the cooling wind through hole 52 with smaller flow area, a mixed flue gas flow is ejected to form; since the outlet area of ​​the flame stabilizing device 5 is large, but the amount of air passing through the flame stabilizing device 5 is small, and the high-speed wind flowing out of the second high-speed mixer channel 82 outside the flame stabilizing device 5 forms a negative pressure zone with stronger suction and entrainment ability at the outlet of the flame stabilizing device 5, the flue gas and mixed gas outside the inner throat 11 are sucked and reflowed to the vicinity of the front end face 111 of the inner throat, and after mixing with another part of the preliminary mixed flue gas flow ejected from the flame stabilizing device 5, low-oxygen and low-nitrogen combustion is carried out.

[0064] The combustion-supporting air entering the combustion-supporting air channel 4 is repeatedly sucked and mixed into the oxygen-depleted flue gas at different positions of the throat area of ​​the combustion device in the flue gas internal circulation device 6, the first high-speed mixed gas channel 81, the second high-speed mixed gas channel 82 and the flame stabilizing device 5 arranged at the front end surface 111 of the inner throat during the forward process, and the high-speed mixed flue gas is diverged and sprayed into the furnace at different positions, which not only significantly reduces the oxygen content in the gas participating in the combustion, but also is beneficial to the uniform distribution of the combustion flame in the furnace and reduces the probability of generating local high-temperature points, thereby ensuring the realization of low-nitrogen combustion that effectively suppresses the generation of NOx and providing technical guarantee for the boiler to meet the standard transformation.

[0065] As can be seen from the above, the technical solution of the present invention has a reasonable and scientific structure, reliable operation and a high degree of automation. It has the function of internal circulation of flue gas, which can make a large amount of oxygen-depleted flue gas flow back to the inner and outer areas of the burner throat, and inject it into the furnace in multiple directions after mixing, and participate in oxygen-depleted and low-nitrogen combustion. It can achieve the substantial effect of reducing NOx emissions through internal circulation of flue gas, fills the gap in the industry, and has strong practicality and broad market application prospects.

[0066] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A dual-Venturi flue gas internal circulation low-nitrogen combustion device, characterized in that: include: A multi-layer throat, wherein a smoke internal circulation inlet is provided on the outer wall of the multi-layer throat, a smoke internal circulation device is provided in the multi-layer throat cavity, the smoke internal circulation device is connected to the smoke internal circulation inlet, the outlet of the multi-layer throat is a high-speed mixed gas channel, the combustion-supporting air channel and the fuel gas channel are provided in the multi-layer throat cavity, and the front end of the fuel gas channel is a spray gun extending out of the outlet of the multi-layer throat; The flue gas internal circulation device is fixed on the outer throat, and comprises: a flue gas passage formed by the intersection and interconnection of a horizontal flue gas inlet ring and a longitudinal flue gas outlet ring, and a venturi-type combustion-supporting air duct formed by the coaxial interconnection of a tapered pipe and a straight pipe inserted and fixed on the flue gas passage; The multi-level throat includes an inner throat at the front end of the throat, a middle throat located near the front end of the throat, and an outer throat located near the rear end of the throat; the flue gas internal circulation suction port is arranged on the outer wall of the main body of the outer throat; the area between the outer wall of the main body of the outer throat and the gas channel is used as a combustion-supporting air channel; the cross-section of the flue gas channel is L-shaped, including two upper and lower circular plates, and the upper and lower circular plates are in a contracted shape.

2. The double Venturi flue gas internal circulation low nitrogen combustion device according to claim 1, characterized in that: The gas channel also includes a connected gas pipe and a commutated air inlet end, the spray gun includes a central spray gun and a peripheral spray gun, and the commutated air inlet end connects the central spray gun and the peripheral spray gun.

3. The double-Venturi flue gas internal circulation low-nitrogen combustion device according to claim 1, characterized in that: The main body of the inner throat port is cylindrical, and an inner end surface of the inner throat port is arranged at the front end; the main body of the middle throat port is in the shape of a shrinking cylinder, and an inner end surface of the middle throat port is arranged at the front end; the main body of the outer throat port is cylindrical, and an outer throat port shrinking inner end surface is arranged at the front end, and the middle throat port is matched and arranged between the inner throat port and the outer throat port.

4. The double Venturi flue gas internal circulation low nitrogen combustion device according to claim 3, characterized in that: The high-speed mixed gas passage includes a first high-speed mixed gas passage formed by a gap between the contraction inner end surface of the outer throat and the inner end surface of the middle throat, and a second high-speed mixed gas passage formed by a gap between the inner end surface of the middle throat and the inner end surface of the inner throat.

5. The double-Venturi flue gas internal circulation low-nitrogen combustion device according to claim 4, characterized in that: A flame stabilizing device is arranged on the inner end surface of the inner throat. The main body of the flame stabilizing device is disc-shaped. A flame stabilizing wind channel and a cooling wind through hole are arranged on the flame stabilizing device.

6. The combustion method of the double venturi flue gas internal circulation low nitrogen combustion device according to any one of claims 1 to 5, characterized in that: The steps include: The spray gun sprays fuel gas, and the combustion air channel sprays combustion air; The smoke internal circulation inlet generates negative pressure, sucking the peripheral smoke into the multi-layer throat cavity; The high-speed mixed gas channel generates negative pressure, sucking the peripheral smoke back to the nozzle; The combustion air in the combustion-supporting air channel is mixed with the peripheral flue gas sucked in during the forward process, and the high-speed mixed flue gas is diverged and sprayed at the outlet of the multi-level throat to become oxygen-poor combustion gas, which enters the furnace and participates in low-nitrogen combustion.

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