A preheating pulverized coal burner based on flue gas backflow and application method thereof

Abstract

This invention discloses a preheating pulverized coal burner based on flue gas recirculation and its application method. The invention includes a guide pipe within the primary air duct, and within the guide pipe are a guide hood and a flue gas guiding ring arranged with gaps. A pulverized coal airflow transport channel is formed between the outer walls of the guide hood and the flue gas guiding ring, and the inner wall of the guide pipe. The interior of the flue gas guiding ring, as well as the gap between the guide hood and the flue gas guiding ring, connect to form a high-temperature flue gas recirculation channel connected to the pulverized coal airflow transport channel. This channel utilizes the negative pressure generated by the pulverized coal airflow in the pulverized coal airflow transport channel to drive the high-temperature flue gas in the furnace back through the high-temperature flue gas recirculation channel to the pulverized coal airflow transport channel, where it mixes with the pulverized coal airflow before entering the furnace combustion zone to participate in combustion. This invention aims to improve the burner's stable combustion capability, effectively reducing the probability of burner coking and burn-off while increasing pulverized coal concentration and preheating time.

Description

Technical Field

[0001] This invention relates to pulverized coal burners for thermal power units, and more specifically to a preheating pulverized coal burner based on flue gas recirculation and its application method. Background Technology

[0002] Pulverized coal burners organize pulverized coal gas flow under the heating effect of high-temperature flue gas to achieve continuous and stable combustion. Different pulverized coal burner structures have varying degrees of pulverized coal concentration and high-temperature flue gas entrainment, thus adapting to pulverized coal gas flow with different combustion characteristics. Concentrated pulverized coal gas flow requires less ignition heat and is therefore easier to ignite; the greater the entrainment of high-temperature flue gas, the more heat is provided for ignition, resulting in more stable combustion. Therefore, to improve the burner's stable combustion capability, the design of the pulverized coal gas flow structure usually focuses on increasing pulverized coal concentration and flue gas entrainment. However, increasing the flue gas entrainment shortens the ignition distance of the pulverized coal gas flow, increasing the probability of burner coking or burn-out, thereby affecting operational safety and burner lifespan. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a preheating pulverized coal combustion method, burner and application method based on flue gas recirculation, which addresses the above-mentioned problems of the prior art. The present invention aims to improve the stable combustion capability of the burner and effectively reduce the probability of coking and burn-off of the burner while increasing the pulverized coal concentration and preheating time.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A preheating pulverized coal burner based on flue gas recirculation includes a primary air duct with a guide pipe inside. The guide pipe contains a guide hood and a flue gas guiding ring arranged with gaps. A pulverized coal airflow conveying channel is formed between the outer walls of the guide hood and the flue gas guiding ring and the inner wall of the guide pipe. The interior of the flue gas guiding ring and the gap between the guide hood and the flue gas guiding ring form a high-temperature flue gas recirculation channel that communicates with the pulverized coal airflow conveying channel. This channel is used to drive the high-temperature flue gas in the furnace through the high-temperature flue gas recirculation channel back to the pulverized coal airflow conveying channel to mix with the pulverized coal airflow before entering the furnace combustion zone to participate in combustion.

[0006] Optionally, the guide tube is an annular cavity structure with an inlet diameter smaller than the outlet diameter.

[0007] Optionally, the flow guide hood has a smooth, protruding flow guide surface on the side facing the flow guide tube inlet, so that the coal powder gas delivery channel between the protruding flow guide surface and the inner wall of the flow guide tube is an annular structure; the flow guide hood has a recessed flow guide surface on the side facing the flue gas guide ring, so that the high-temperature flue gas return channel between the recessed flow guide surface and the outer wall of the flue gas guide ring is an annular structure that is inclined towards the flow guide tube inlet.

[0008] Optionally, the flue gas guiding ring is an annular structure with an inlet diameter larger than the outlet diameter, and the inlet side of the flue gas guiding ring faces the furnace side and the outlet side faces the concave guiding surface of the guide hood, so as to utilize the high-temperature flue gas in the furnace to return and mix the returned flue gas with the concentrated coal powder airflow before entering the furnace combustion zone to participate in combustion.

[0009] Optionally, at least one of the flow guide and the flue gas guide ring is mounted on a stroke adjustment mechanism, which is used to adjust the relative distance between the flow guide and the flue gas guide ring.

[0010] Optionally, a coal powder concentration ring is provided upstream of the pulverized coal airflow direction in the primary air duct for separating the coal powder airflow into a light-side coal powder airflow and a concentrated-side coal powder airflow. The cavity between the outer wall of the guide pipe and the inner wall of the primary air duct forms a light-side coal powder airflow channel, and the interior of the guide pipe forms a concentrated-side coal powder airflow channel.

[0011] Optionally, the coal powder concentration ring is an annular structure with an inlet diameter larger than the outlet diameter. It is used to separate the coal powder in the airflow into a light-side coal powder airflow and a concentrated-side coal powder airflow by having the inner wall of the annular structure, which is arranged at an inclination, collide with the coal powder airflow.

[0012] Optionally, the guide pipe is provided with a multi-stage coal powder concentration ring upstream of the coal powder airflow direction.

[0013] Optionally, the diameter of the multi-stage coal powder concentration rings gradually decreases along the coal powder airflow direction.

[0014] The present invention also provides an application method for the preheating pulverized coal burner based on flue gas recirculation, which includes adjusting the relative distance between the guide hood and the flue gas guide ring through a stroke adjustment mechanism according to different coal types, thereby changing the lead time of pulverized coal airflow preheating to adapt to the combustion characteristics of different coal types.

[0015] Compared with the prior art, the present invention has the following main advantages: The preheating pulverized coal burner based on flue gas recirculation has a guide pipe inside the primary air duct. The guide pipe contains a guide hood and a flue gas guiding ring arranged with gaps. A pulverized coal airflow conveying channel is formed between the outer walls of the guide hood and the flue gas guiding ring and the inner wall of the guide pipe. The interior of the flue gas guiding ring and the gap between the guide hood and the flue gas guiding ring form a high-temperature flue gas recirculation channel connected to the pulverized coal airflow conveying channel, for utilizing the pulverized coal airflow in the pulverized coal airflow conveying channel. The negative pressure generated by the flow drives the high-temperature flue gas in the furnace to flow back through the high-temperature flue gas return channel to the pulverized coal gas delivery channel, where it mixes with the pulverized coal gas before entering the combustion zone of the furnace to participate in combustion. By utilizing the guide pipe, guide hood, and flue gas guide ring, the heat of the flue gas is simply used to preheat the pulverized coal gas, thereby improving the stable combustion capability. Compared with traditional burners, the pulverized coal gas preheating of this invention is earlier. Because the mixing of the pulverized coal gas and the high-temperature return flue gas takes place in a high pulverized coal depth and low oxygen environment, the combustion rate is low, thus reducing the risk of coking. Therefore, by mixing the pulverized coal gas with the high-temperature flue gas in advance, this invention can achieve preheating in a high-temperature, low-oxygen environment, which can improve the stable combustion capability of the burner and effectively reduce the probability of coking and burn-off. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the burner's principle structure in Embodiment 1 of the present invention.

[0017] Figure 2 This is a partial cross-sectional view of the burner in Embodiment 1 of the present invention.

[0018] Figure 3 This is a schematic diagram of the burner's principle structure in Embodiment 2 of the present invention.

[0019] Legend: 1. Primary air duct; 10. Pulverized coal airflow conveying channel; 11. High-temperature flue gas return channel; 2. Pulverized coal concentration ring; 3. Guide pipe; 4. Guide hood; 41. Protruding guide surface; 42. Recessed guide surface; 5. Flue gas diversion ring. Detailed Implementation

[0020] Example 1:

[0021] like Figure 1 and Figure 2As shown, this embodiment provides a preheating pulverized coal burner based on flue gas recirculation, including a primary air duct 1, a guide pipe 3 inside the primary air duct 1, a guide hood 4 and a flue gas guiding ring 5 arranged with gaps inside the guide pipe 3, a pulverized coal airflow conveying channel 10 is formed between the outer walls of the guide hood 4 and the flue gas guiding ring 5 and the inner wall of the guide pipe 3, and the interior of the flue gas guiding ring 5 and the gap between the guide hood 4 and the flue gas guiding ring 5 form a high-temperature flue gas recirculation channel 11 connected to the pulverized coal airflow conveying channel 10, so as to use the negative pressure generated by the pulverized coal airflow in the pulverized coal airflow conveying channel 10 to drive the high-temperature flue gas in the furnace to recirculate through the high-temperature flue gas recirculation channel 11 back to the pulverized coal airflow conveying channel 10 to mix with the pulverized coal airflow before entering the furnace combustion zone to participate in combustion.

[0022] like Figure 1 and Figure 2 As shown, in this embodiment, the guide pipe 3 is an annular cavity structure with an inlet diameter smaller than the outlet diameter. The purpose is to gradually increase the pressure in the mixing zone between the outlet side of the guide pipe 3, the outer wall of the flue gas guiding ring 5, and the edge of the guide hood 4, thereby improving the mixing effect of the return flue gas and the concentrated pulverized coal flow. See also... Figure 1 As an optional implementation, in this embodiment, the diameter of the guide tube 3 gradually decreases after it reaches the edge of the guide shroud 4 from the inlet side.

[0023] like Figure 1 As shown, the guide hood 4 has a smooth protruding guide surface 41 on the inlet side of the guide pipe 3 so that the coal powder airflow conveying channel 10 between the protruding guide surface 41 and the inner wall of the guide pipe 3 is an annular structure; the guide hood 4 has a recessed guide surface 42 on the side facing the flue gas guiding ring 5 so that the high temperature flue gas return channel 11 between the recessed guide surface 42 and the outer wall of the flue gas guiding ring 5 is an annular structure that is inclined towards the inlet side of the guide pipe 3, so that the coal powder airflow and the high temperature flue gas are mixed more evenly.

[0024] like Figure 1 and Figure 2As shown, in this embodiment, the flue gas guiding ring 5 is an annular structure (trumpet-shaped) with an inlet diameter larger than the outlet diameter. The inlet side of the flue gas guiding ring 5 faces the furnace side, and the outlet side faces the concave guiding surface 42 of the guide hood 4. This allows the high-temperature flue gas in the furnace to recirculate and mix with the concentrated pulverized coal flow before entering the furnace combustion zone to participate in combustion. During operation, the guide pipe 3 further physically separates the concentrated and diluted pulverized coal flow obtained by the pulverized coal concentration ring 2. The diluted pulverized coal flow directly enters the furnace combustion zone along the area between the guide pipe 3 and the primary air duct 1 to participate in combustion. The concentrated pulverized coal flow enters the interior of the guide pipe 3 and continues to flow along the area between the guide pipe 3 and the guide hood 4 under the action of the guide hood 4. When leaving the guide hood 4, it mixes with the recirculated flue gas and flows out of the burner along the area between the flue gas guiding ring 5 and the guide pipe 3, entering the furnace combustion zone to participate in combustion. Under the action of the ejected airflow, a low-pressure area is formed inside the flue gas guide ring 5, thereby driving the high-temperature flue gas in the furnace to flow back. The annular structure allows the flue gas to continue to flow back into the interior of the guide shroud 4 and turn to flow out along the inner wall of the guide shroud 4, mix with the concentrated coal powder airflow, and return to the furnace.

[0025] Furthermore, as an optional implementation, in this embodiment, at least one of the flow guide 4 and the flue gas guiding ring 5 is mounted on the stroke adjustment mechanism, which is used to adjust the relative distance between the flow guide 4 and the flue gas guiding ring 5. Considering the high temperature of the flue gas, the stroke adjustment mechanism can be connected to the flow guide 4 / flue gas guiding ring 5 via a connector, and the stroke adjustment mechanism is placed in an area where the high-temperature flue gas does not come into contact with it to improve the safety of the stroke adjustment mechanism. The stroke adjustment mechanism is a conventional moving mechanism, which can be implemented electrically, hydraulically, pneumatically, or manually as needed.

[0026] like Figure 1 and Figure 2 As shown, in an optional implementation, in this embodiment, a pulverized coal concentration ring 2 is provided upstream of the pulverized coal airflow direction in the primary air duct 1, located in the guide pipe 3, to separate the pulverized coal airflow into a light-side pulverized coal airflow and a heavy-side pulverized coal airflow. The cavity between the outer wall of the guide pipe 3 and the inner wall of the primary air duct 1 forms a light-side pulverized coal airflow channel, and the interior of the guide pipe 3 forms a heavy-side pulverized coal airflow channel. The pulverized coal concentration ring 2 separates the pulverized coal airflow into a light-side pulverized coal airflow and a heavy-side pulverized coal airflow. The light-side pulverized coal airflow directly enters the combustion zone of the furnace to participate in combustion, while the heavy-side pulverized coal airflow mixes with the return flue gas from the furnace combustion zone before entering the furnace combustion zone to participate in combustion. The structure of the pulverized coal concentration ring enables the separation of the pulverized coal airflow in the early stage, improving stable combustion capability. Moreover, preheating is mainly concentrated in the heavy-side pulverized coal airflow, and the preheating in a low-oxygen environment further reduces the risk of burner coking.

[0027] In this embodiment, the coal powder concentration ring 2 is an annular structure with an inlet diameter larger than the outlet diameter. It is used to separate the coal powder in the airflow into a light-side coal powder airflow and a concentrated-side coal powder airflow by having the inner wall of the annular structure, which is arranged at an inclination, collide with the coal powder airflow.

[0028] In this embodiment, a multi-stage coal powder concentration ring 2 is provided upstream of the coal powder airflow direction in the guide pipe 3 to enhance the ability to separate the coal powder airflow into a light-side coal powder airflow and a concentrated-side coal powder airflow. For example, as an optional implementation, such as... Figure 1 and Figure 2 As shown, in this embodiment, the primary air duct 1 is equipped with two-stage coal powder concentration rings 2. In this embodiment, the diameter of the multi-stage coal powder concentration rings 2 gradually decreases along the coal powder airflow direction to enhance the impact effect between the inclined inner wall of the annular structure and the coal powder airflow, making the coal powder more uniform.

[0029] In addition, this embodiment also provides an application method for the preheating pulverized coal burner based on flue gas recirculation, which includes adjusting the relative distance between the guide hood 4 and the flue gas guiding ring 5 through a stroke adjustment mechanism according to different coal types, thereby changing the lead time of pulverized coal airflow preheating to adapt to the combustion characteristics of different coal types.

[0030] In summary, when using the preheating pulverized coal burner based on flue gas recirculation in this embodiment, the pulverized coal airflow in the primary air duct achieves rich-lean separation via the pulverized coal concentration ring 2. The lean side pulverized coal airflow directly enters the furnace for combustion, while the rich side pulverized coal airflow is guided into the guide pipe 3, mixes with the recirculated high-temperature flue gas, and enters the furnace for combustion after preheating. The high-temperature flue gas, under the action of the flue gas guiding ring 5, recirculates back into the burner, mixes with the rich side pulverized coal airflow, and returns to the furnace. Moreover, this preheating pulverized coal burner based on flue gas recirculation, in addition to achieving rich-lean pulverized coal separation, preheats the rich side pulverized coal airflow in advance, further improving the burner's stable combustion capability.

[0031] Example 2:

[0032] This embodiment is basically the same as Embodiment 1, with the main difference being that the preheating pulverized coal burner based on flue gas recirculation in Embodiment 1 includes a pulverized coal concentration ring 2, while the preheating pulverized coal burner based on flue gas recirculation provided in this embodiment does not include a pulverized coal concentration ring 2. Figure 3 As shown. Even without using the pulverized coal thickening ring 2, the preheating of the pulverized coal flow using the heat from the flue gas can be easily achieved by using the guide pipe 3, the guide hood 4, and the flue gas guiding ring 5, thereby improving the stable combustion capability. Compared with traditional burners, this allows for earlier preheating of the pulverized coal flow. Since the mixing of the pulverized coal flow with the high-temperature return flue gas occurs in a high pulverized coal depth and low oxygen environment, the combustion rate is low, thus reducing the risk of coking.

[0033] Example 3:

[0034] This embodiment is basically the same as embodiment two, the main difference being that: in embodiment two, the primary air duct 1 of the preheating pulverized coal burner based on flue gas recirculation contains a separate pulverized coal airflow channel between the outer wall of the primary air duct 1 and the inner wall of the guide pipe 3, while the primary air duct 1 of the preheating pulverized coal burner based on flue gas recirculation provided in this embodiment has a closed structure between the outer wall of the primary air duct 1 and the inner wall of the guide pipe 3, so that the pulverized coal airflow can only flow to the furnace through the inside of the guide pipe 3.

[0035] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A preheating pulverized coal burner based on flue gas recirculation, characterized in that, The system includes a primary air duct (1), a guide pipe (3) inside the primary air duct (1), a guide hood (4) and a flue gas guiding ring (5) arranged with gaps inside the guide pipe (3), and a pulverized coal airflow conveying channel (10) is formed between the outer walls of the guide hood (4) and the flue gas guiding ring (5) and the inner wall of the guide pipe (3). The flue gas guiding ring (5) and the gaps between the guide hood (4) and the flue gas guiding ring (5) form a high-temperature flue gas return channel (11) connected to the pulverized coal airflow conveying channel (10) to use the negative pressure generated by the pulverized coal airflow in the pulverized coal airflow conveying channel (10) to drive the high-temperature flue gas in the furnace to return to the pulverized coal airflow conveying channel (10) through the high-temperature flue gas return channel (11) to mix with the pulverized coal airflow before entering the furnace combustion area to participate in combustion. The guide pipe (3) is an annular tube with an inlet diameter smaller than the outlet diameter. The structure includes a smooth protruding guide surface (41) on the inlet side of the guide tube (3) so that the coal powder airflow conveying channel (10) between the protruding guide surface (41) and the inner wall of the guide tube (3) is an annular structure; the guide surface (4) on the side facing the flue gas guiding ring (5) has a recessed guide surface (42) so that the high temperature flue gas return channel (11) between the recessed guide surface (42) and the outer wall of the flue gas guiding ring (5) is an annular structure that is inclined towards the inlet side of the guide tube (3); the flue gas guiding ring (5) is an annular structure with an inlet diameter larger than the outlet diameter, and the inlet side of the flue gas guiding ring (5) faces the furnace side and the outlet side faces the recessed guide surface (42) side of the guide surface (4), so as to utilize the high temperature flue gas return in the furnace and mix the return flue gas with the concentrated coal powder airflow before entering the furnace combustion area to participate in combustion.

2. The preheating pulverized coal burner based on flue gas recirculation according to claim 1, characterized in that, At least one of the flow guide (4) and the flue gas guide ring (5) is installed on the stroke adjustment mechanism, which is used to adjust the relative distance between the flow guide (4) and the flue gas guide ring (5).

3. The preheating pulverized coal burner based on flue gas recirculation according to claim 1, characterized in that, The primary air duct (1) is provided with a coal powder concentration ring (2) located upstream of the coal powder airflow direction of the guide pipe (3) for separating the coal powder airflow into a light coal powder airflow and a concentrated coal powder airflow. The cavity between the outer wall of the guide pipe (3) and the inner wall of the primary air duct (1) forms a light coal powder airflow channel, and the interior of the guide pipe (3) forms a concentrated coal powder airflow channel.

4. The preheating pulverized coal burner based on flue gas recirculation according to claim 3, characterized in that, The coal powder concentration ring (2) is an annular structure with an inlet diameter larger than the outlet diameter. It is used to make the coal powder in the airflow focus towards the center of the airflow under the action of inertia by impacting the inner wall of the annular structure with the coal powder airflow, so as to separate the coal powder airflow into a light side coal powder airflow and a thick side coal powder airflow.

5. The preheating pulverized coal burner based on flue gas recirculation according to claim 3, characterized in that, The guide pipe (3) is provided with a multi-stage coal powder concentration ring (2) upstream of the coal powder airflow direction.

6. The preheating pulverized coal burner based on flue gas recirculation according to claim 5, characterized in that, The diameter of the multi-stage coal powder concentration rings (2) gradually decreases along the coal powder airflow direction.

7. A method for applying the preheating pulverized coal burner based on flue gas recirculation as described in claim 2, characterized in that, This includes adjusting the relative distance between the guide hood (4) and the flue gas guide ring (5) through the stroke adjustment mechanism according to different coal types, thereby changing the advance amount of coal powder airflow preheating to adapt to the combustion characteristics of different coal types.

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