Primary air pulverized coal semi-gasification stable combustion device and pulverized coal semi-gasification method

Abstract

This invention provides a primary air pulverized coal semi-gasification stable combustion device, belonging to the field of combustion technology. The device includes a first tube, a second tube, and a heat storage body; the first tube is sleeved on the outside of the second tube. The first tube includes a variable diameter structure with gradually increasing diameter, followed by an outer cylinder with a constant diameter. The second tube includes a pulverized coal ignition cone, followed by a swirl structure. On the cone surface, there is a primary pulverized coal concentration ring opening, its opening facing the central axis of the cone; at a position where the pipe diameter is larger than the primary pulverized coal concentration ring opening, there is a secondary pulverized coal concentration ring opening, its opening direction parallel to the central axis of the cone. The heat storage body is located inside the second tube. This invention enables primary air to enter the furnace for secondary combustion, achieving rapid and complete combustion, advancing the combustion reaction time in the boiler, and making the physical space of combustion more concentrated. This allows for stable operation of coal-fired boilers at ultra-low loads, meeting the low NOx emission requirements for coal-fired boilers operating at ultra-low loads.

Description

Technical Field

[0001] This invention belongs to the field of combustion technology, specifically relating to a primary air pulverized coal semi-gasification stable combustion device and a semi-gasification method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The power generation from renewable energy sources is characterized by fluctuations and intermittency, often necessitating the peak-shaving function of coal-fired power units to ensure a more stable power output from the grid. Specifically, this involves reducing the output of coal-fired power units when renewable energy generation increases, and increasing their output when renewable energy generation decreases. However, frequent ignition and shutdown of coal-fired power units for peak shaving would severely impact boiler lifespan. Therefore, the primary principle of peak shaving is stable combustion technology at low loads, enabling stable combustion even at 30-40% of the rated load. In actual operation, when the boiler operates at low loads, the denitrification system does not operate under rated conditions, resulting in low denitrification efficiency and high NOx emissions.

[0004] In boiler combustion, primary air refers to the air carrying pulverized coal into the burner. Its main function is to transport the pulverized coal and meet the oxygen requirement in the initial stage of combustion. Since the pulverized coal introduced by the primary air is the initial combustion point in the boiler, accompanying ignition, its stable combustion is crucial for low-load operation and burnout. Commonly used stable combustion technologies include micro-oil stable combustion, natural gas stable combustion, and plasma ignition, but these all require the addition of other types of fuel or complex ignition devices, resulting in higher costs and more difficult maintenance. Furthermore, in actual operation, power plants may encounter deep peak-shaving demands as low as 20% of rated load, lower than the 30-40% rated load range of existing low-load stable combustion technologies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a primary air pulverized coal semi-gasification stable combustion device and a pulverized coal semi-gasification method. The stable combustion device can advance the physical space and reaction timing of combustion, enabling boilers operating at low loads to maintain stable combustion at high temperatures, and can achieve stable operation of coal-fired boilers at ultra-low loads (minimum 20% of rated load).

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] Firstly, a primary air pulverized coal semi-gasification stable combustion device includes a first pipe body, a second pipe body, and a heat storage body; the first pipe body is sleeved on the outside of the second pipe body, and a primary air channel is formed between the first pipe body and the second pipe body.

[0008] The first pipe body includes a variable diameter structure with a gradually increasing pipe diameter, followed by an outer cylinder with a constant pipe diameter, and then a variable diameter outlet with a gradually decreasing pipe diameter.

[0009] The second tube includes a coal powder ignition cone with a gradually increasing diameter. The coal powder ignition cone is located inside the variable diameter structure, and a swirl structure is connected after the coal powder ignition cone.

[0010] The swirling structure is used to create a swirling flow from the primary air.

[0011] On the conical surface of the pulverized coal ignition cone, there is a primary pulverized coal concentration ring, the opening of which faces the central axis of the pulverized coal ignition cone; at a position on the conical surface with a pipe diameter larger than that of the primary pulverized coal concentration ring, there is a secondary pulverized coal concentration ring, the opening direction of which is parallel to the central axis of the pulverized coal ignition cone.

[0012] The heat storage body is a rotating body with the central axis of the pulverized coal ignition cone as its rotation axis, located inside the second tube.

[0013] Optionally, the front end of the first pipe body is a bend for introducing primary air, and there is a flow equalization plate in the bend; the rear of the bend is a variable diameter structure.

[0014] Optionally, the front end of the second tube is an ignition channel, with an igniter connected in front of the ignition channel and a pulverized coal ignition cone connected behind the ignition channel.

[0015] Optionally, the front part of the heat storage body is a cone with a gradually increasing diameter, the middle part is a cylinder with a constant diameter, and the rear part is a cone with a gradually decreasing diameter.

[0016] The cone of the heat storage body is made of ceramic or heat-resistant metal.

[0017] The rear part of the heat storage body extends beyond the second tube but within the range of the first tube.

[0018] The heat storage body is fixed by heat-resistant support rods connected to the outer swirl structure and / or the outer cylinder wall.

[0019] Optionally, the swirling structure includes a multi-stage swirling structure, which is distributed front and back within the outer cylinder, with the diameter of the rear swirling structure being larger than that of the front swirling structure.

[0020] Optionally, the cross-sectional area of ​​the gas channel formed between the conical rear part of the heat storage body and the variable diameter outlet is the same as the cross-sectional area of ​​the gas channel formed between the central column of the heat storage body and the outer cylinder, so that the area of ​​the airflow channel is consistent before and after.

[0021] Secondly, the coal gasification method based on the aforementioned primary air coal pulverized semi-gasification stable combustion device.

[0022] A portion of the primary air flowing between the first and second pipes enters the inner side of the second pipe along the primary pulverized coal concentration ring and is ignited in front of the cone at the front of the heat storage body, forming ignited primary air.

[0023] A portion of the primary air flowing between the first and second pipes enters the inner side of the second pipe along the secondary coal powder concentration ring, forming a vortex on the outer side of the cone at the front of the heat storage body, which is the vortex primary air.

[0024] The remaining portion of the primary air between the first and second tubes forms a swirling flow on the outside of the heat storage body through the swirling structure, which is called swirling primary air.

[0025] The ignited primary air, the vortex primary air, and the swirl primary air come into contact with each other and undergo semi-gasification pre-combustion to obtain semi-gasified primary air containing strong reducing gases.

[0026] The heat storage body maintains a high temperature, and the pulverized coal around the heat storage body can undergo a semi-gasification process.

[0027] The primary air outside the heat storage body is in a swirling state with a small radial velocity difference, resulting in uniform flame propagation, uniform semi-gasification pre-combustion, and complete semi-gasification reaction.

[0028] Optionally, the primary air containing pulverized coal is diverted at the bend of the flow equalization plate and remixed at the end of the flow equalization plate.

[0029] Thirdly, boilers containing the aforementioned primary air pulverized coal semi-gasification stable combustion device.

[0030] The primary air pulverized coal semi-gasification and stable combustion device is located on the primary air bypass branching off from the primary air main line, and then rejoins the primary air main line, connecting to the primary air inlet of the boiler.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. The present invention achieves uniform flow of primary air by arranging a pulverized coal flow equalization device at the front end of the pulverized coal semi-gasification device, preventing pulverized coal from concentrating on the outside of the bend due to inertia, so that the distribution of pulverized coal entering the variable diameter area remains uniform.

[0033] 3. This invention enables the primary air to undergo semi-gasification pre-combustion in advance, increasing the temperature of the fuel (primary air pulverized coal). When the boiler is running at low load, the primary air enters the furnace for secondary combustion, burning completely as soon as possible. This advances the reaction time of combustion in the boiler. Since a portion of the fuel changes from powder to combustible gas compared to pulverized coal, the physical space where combustion occurs is more concentrated, enabling stable operation of coal-fired boilers at ultra-low loads (minimum 20% of rated load).

[0034] 2. This invention enables primary air to undergo semi-gasification in the primary air bypass via a pulverized coal semi-gasification device. Through incomplete combustion, it generates a strong reducing gas, creating a localized strong reducing atmosphere within the boiler. This facilitates the reduction of NOx to N2, thus achieving the low NOx emission requirements for coal-fired boilers operating at ultra-low loads.

[0035] 4. In the pulverized coal semi-gasification device of the present invention, the entire airflow is in a swirling state. The oxygen content is relatively sufficient and the temperature is high at the center of the swirling flow, making it easy to ignite and resulting in good semi-gasification effect. The radial velocity difference is small, which is the main path for flame propagation, enabling the pulverized coal to be fully semi-gasified, increasing the temperature, and thus facilitating stable combustion and burnout of the boiler at low load. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0037] Figure 1 This is a schematic diagram of the primary air pulverized coal semi-gasification and stable combustion device in Example 1.

[0038] Figure 2 This is a schematic diagram of the coal powder ignition cone in Example 1.

[0039] Figure 3 This is a schematic diagram of the bent pipe in Example 1.

[0040] Figure 4 This is a schematic diagram of the swirl structure in Example 1.

[0041] Figure 5 This is a schematic diagram of the primary air semi-gasification process in Example 2.

[0042] Figure 6 This is a schematic diagram of the boiler structure in Example 3.

[0043] Figure 7 This is a schematic diagram of the primary air pulverized coal semi-gasification and stable combustion device in Example 4.

[0044] Among them, 1. Igniter, 2. Igniting channel, 3. Bend, 4. Diverter plate, 5. Variable diameter structure, 6. Pulverized coal ignition cone, 6.1. Primary pulverized coal concentration ring, 6.2. Secondary pulverized coal concentration ring, 7. Outer cylinder, 7.1. Variable diameter outlet, 8. Primary swirl structure, 8.1. Swirl blades, 8.2. Straight cylinder, 9. Secondary swirl structure, 10. Heat storage body, 11. Ignition zone, 12. Vortex primary air, 13. Swirl primary air, 14. Furnace, 15. Primary air main path, 16. Primary air bypass, 17. Primary air pulverized coal semi-gasification stable combustion device, 18. Ignition device. Detailed Implementation

[0045] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0046] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0047] Example 1

[0048] like Figure 1 As shown, the primary air pulverized coal semi-gasification stable combustion device includes a first tube body, a second tube body, and a heat storage body 10.

[0049] The first pipe is fitted over the second pipe, and a primary air passage is formed between the first pipe and the second pipe.

[0050] The primary air is air mixed with a certain proportion of pulverized coal, and the pulverized coal flows with the air in the primary air channel.

[0051] The first pipe body includes a variable diameter structure 5 with a gradually increasing pipe diameter, followed by an outer cylinder 7 with a constant pipe diameter, and then a variable diameter outlet 7.1 with a gradually decreasing pipe diameter.

[0052] The second tube includes a coal powder ignition cone 6 with a gradually increasing diameter. The coal powder ignition cone 6 is located inside the variable diameter structure 5. The coal powder ignition cone 6 is connected to a first-stage swirl structure 8, which ends within the outer cylinder 7.

[0053] The primary swirl structure 8 is used to create a swirl in the primary airflow.

[0054] like Figure 2 As shown, on the cone surface of the pulverized coal ignition cone 6, there are multiple primary pulverized coal concentration rings 6.1, and multiple elongated primary pulverized coal concentration rings 6.1 are distributed on the cross section of the cone surface perpendicular to the cone axis.

[0055] The opening of the primary coal powder concentration ring 6.1 faces the central axis of the coal powder ignition cone 6, allowing a portion of the primary air to pass through the primary coal powder concentration ring 6.1 and enter the inner side of the second pipe body.

[0056] On the cone surface of the pulverized coal ignition cone 6, at a position where the diameter is larger than that of the primary pulverized coal concentration ring 6.1, there are multiple elongated secondary pulverized coal concentration rings 6.2. The cross-sections of the multiple secondary pulverized coal concentration rings 6.2 are parallel to the cross-sections of the primary pulverized coal concentration rings 6.1 on the cone surface; the opening direction of the secondary pulverized coal concentration rings 6.2 is parallel to the central axis of the pulverized coal ignition cone 6.

[0057] like Figure 1 As shown, the heat storage body 10 is a rotating body with the central axis of the pulverized coal ignition cone 6 as its rotation axis, and is located inside the second tube.

[0058] The front end of the first pipe body is a bend 3 for primary air intake. The arrow below the bend 3 indicates the flow direction of the primary air. There is a flow equalization plate 4 in the bend 3. The flow equalization plate 4 divides the bend 3 into inner and outer parts along the pipe diameter. The bending radius of the outer part is larger than that of the inner part. After the bend 3 is a variable diameter structure 5.

[0059] The front end of the second tube is an ignition channel 2, with an igniter 1 connected in front of the ignition channel 2 and a pulverized coal ignition cone 6 connected behind the ignition channel 2.

[0060] like Figure 3 As shown, the ignition channel 2 passes through the bend 3 at the front end of the first pipe body and is connected to the pulverized coal ignition cone 6 in the second pipe body.

[0061] like Figure 1 As shown, the front part of the heat storage body 10 is a cone with a gradually increasing diameter, the middle part is a cylinder with a constant diameter, and the rear part is a cone with a gradually decreasing diameter.

[0062] The cone of the heat storage body 10 is made of ceramic or heat-resistant metal. Its function is to maintain the internal high temperature so that the coal powder around the heat storage body can be semi-gasified.

[0063] The rear part of the heat storage body 10 extends beyond the second tube body but within the range of the first tube body.

[0064] The first-stage swirl structure 8 is connected to the pulverized coal ignition cone 6.

[0065] The first-stage swirl structure 8 includes a straight cylinder 8.2 and multiple swirl blades 8.1 outside the straight cylinder. The swirl blades 8.1 are perpendicular to the outer surface of the straight cylinder 8.2, and the outer edge of the swirl blades 8.1 is connected to the inner surface of the outer cylinder 7.

[0066] like Figure 4 As shown, the front section of the swirl blade 8.1 is perpendicular to the cross-section of the straight cylinder 8.2, and the rear section is inclined at a certain angle to the front section. The angle between the rear section and the front section is 115° to 125°. Multiple swirl blades 8.1 block each other, and the degree of blocking is 1.2 to 1.3.

[0067] The tilt angle of the swirl blades is selected mainly to meet the requirements of swirl intensity.

[0068] The cross-sectional area of ​​the gas passage formed between the rear cone of the concave heat storage body 10 and the variable diameter outlet 7.1 is the same as the cross-sectional area of ​​the gas passage formed between the middle column of the heat storage body 10 and the outer cylinder 7, so that the area of ​​the airflow passage is consistent from front to back.

[0069] Example 2

[0070] The coal gasification method based on the primary air coal powder semi-gasification stable combustion device in Example 1.

[0071] like Figure 5 As shown, a portion of the primary air between the first and second pipes enters the inner side of the second pipe along the primary coal powder concentration ring 6.1, and is ignited by the igniter 1 in front of the cone at the front of the heat storage body 10, forming ignited primary air.

[0072] Because the opening at this location faces the central axis of the pulverized coal ignition cone 6, the pulverized coal accumulates near the central axis of the pulverized coal ignition cone 6, forming an over-rich area, which facilitates ignition and keeps the flame alive. The primary airflow in the ignition zone 11 flows backward and disperses to the surrounding area along the conical tip of the heat storage body 10.

[0073] A portion of the primary air between the first and second pipes enters the inner side of the second pipe along the secondary coal powder concentration ring 6.2, forming a vortex on the outer side of the cone at the front of the heat storage body 10, which is the vortex primary air 12.

[0074] Pulverized coal rotates in the vortex zone, prolonging its residence time in this position, thus increasing the pulverized coal concentration in the vortex zone and making it easier to burn stably.

[0075] Since the opening direction at this location is parallel to the central axis of the pulverized coal ignition cone 6, this portion of the primary air, after entering the inner side of the second pipe, does not approach the ignition zone 11. There is a region with lower air pressure between it and the ignition zone 11. At the same time, due to the cone-shaped part of the heat storage body 10, the cross-sectional area of ​​the inner channel of the pulverized coal ignition cone 6 gradually decreases, which hinders the primary air. Under the action of changes in flow velocity and friction, a vortex is formed on the outer side of the cone at the front of the heat storage body 10 behind the ignition zone 1.

[0076] The remaining portion of the primary air between the first tube and the second tube forms a swirling flow on the outside of the heat storage body through the first-stage swirling structure 8, which is the swirling primary air 13.

[0077] The ignited primary air, the vortex primary air 12, and the swirling primary air 13 come into contact with each other and undergo semi-gasification pre-combustion to obtain semi-gasified primary air containing strong reducing gases.

[0078] The heat storage body 10 maintains a high temperature, so that the coal powder around the heat storage body 10 can undergo a semi-gasification process.

[0079] The space between the heat storage body and the outer tube is the primary air channel. The primary air channel makes the primary air swirling, with a small radial velocity difference, uniform flame propagation, uniform semi-gasification pre-combustion, and complete semi-gasification reaction.

[0080] At the bend 3, the primary air containing pulverized coal is split into two streams of primary air with the same pulverized coal concentration by the flow equalization plate 4 at the bend. This prevents the pulverized coal from concentrating in the larger turning radius of the bend 3 due to inertia, thus avoiding uneven pulverized coal concentration on the inner and outer sides. The pulverized coal is then mixed at the end of the flow equalization plate 4 and enters the range of the diameter reducing device 5.

[0081] Example 3

[0082] like Figure 6 As shown, the primary air pulverized coal semi-gasification stable combustion device differs from Example 1 in that a secondary swirl structure 9 is present after the primary swirl structure 8. The outer edge of the blades 8.1 of the primary swirl structure is connected to the inner surface of the straight cylinder of the secondary swirl structure, and the outer edge of the blades of the secondary swirl structure is connected to the inner surface of the cylinder 7.

[0083] The angle between the rear and front sections of the secondary swirl blades is consistent with the structure of the blade 8.1 of the primary swirl structure. The rear and front sections are tilted at a certain angle, with an angle of 115° to 125°. Multiple swirl blades block each other, with a blocking degree of 1.2 to 1.3.

[0084] To address the issue of the difficulty in semi-gasification of anthracite pulverized coal, a secondary swirl structure 9 is added. Since the pulverized coal rotates in the swirl zone, the additional secondary swirl structure 9 prolongs the time the pulverized coal remains in the swirl state, making it easier to achieve stable combustion.

[0085] Example 4

[0086] like Figure 7 As shown, the boiler containing the pulverized coal semi-gasification device in Example 1 has a vertical dimension of furnace 14 that is larger than its horizontal dimension, and the airflow in furnace 14 flows from bottom to top.

[0087] The primary air main road 15 is located below the boiler, and the primary air inlet is horizontal.

[0088] A primary air bypass 16 is branched off from the primary air main duct 15. A primary air pulverized coal semi-gasification stable combustion device 17 is installed on the primary air bypass 16. The semi-gasified primary air enters the furnace and is ignited by the ignition device 18. It can be fully burned in a small area below the furnace. In the atmosphere of the combustion local area, the concentration of strong reducing gas is high, which is conducive to the reduction of NOx to N2. This can achieve the low NOx emission requirements of coal-fired boilers when operating at ultra-low load.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A primary air pulverized coal semi-gasification and stable combustion device, characterized in that, include: The first tube body, the second tube body, and the heat storage body; the first tube body is sleeved on the outside of the second tube body, and a primary air channel is formed between the first tube body and the second tube body. The first pipe body includes a variable diameter structure with a gradually increasing pipe diameter, followed by an outer cylinder with a constant pipe diameter, and followed by a variable diameter outlet with a gradually decreasing pipe diameter. The second tube includes a coal powder ignition cone with a gradually increasing diameter. The coal powder ignition cone is located inside the variable diameter structure, and a swirl structure is connected behind the coal powder ignition cone. On the cone surface of the pulverized coal ignition cone, there is a primary pulverized coal concentration ring, with the opening facing the central axis of the pulverized coal ignition cone; The conical surface of the pipe with a diameter larger than that of the primary pulverized coal concentration ring has a secondary pulverized coal concentration ring, with the opening direction parallel to the central axis of the pulverized coal ignition cone; The heat storage body is a rotating body with the central axis of the pulverized coal ignition cone as its rotation axis, located inside the second tube.

2. The primary air pulverized coal semi-gasification and stable combustion device as described in claim 1, characterized in that, The front end of the first pipe is a bend that allows primary air to enter, and there is a flow equalization plate in the bend; the rear of the bend is a variable diameter structure.

3. The primary air pulverized coal semi-gasification and stable combustion device as described in claim 1, characterized in that, The front end of the second tube is an ignition channel, with an igniter connected in front of the ignition channel and a pulverized coal ignition cone connected behind the ignition channel.

4. The primary air pulverized coal semi-gasification and stable combustion device as described in claim 1, characterized in that, The front part of the heat storage body is a cone with a gradually increasing diameter, the middle part is a cylinder with a constant diameter, and the rear part is a cone with a gradually decreasing diameter. The heat storage element is made of ceramic or heat-resistant metal. The rear part of the heat storage body extends beyond the second tube but within the range of the first tube. The heat storage body is fixed by heat-resistant support rods connected to the outer swirl structure and / or the outer cylinder wall.

5. The primary air pulverized coal semi-gasification and stable combustion device as described in claim 1, characterized in that, The swirling structure includes a multi-stage swirling structure, which is distributed front and back within the outer cylinder, with the diameter of the rear swirling structure being larger than that of the front swirling structure.

6. The primary air pulverized coal semi-gasification and stable combustion device as described in claim 1, characterized in that, The cross-sectional area of ​​the gas channel formed between the conical rear part of the conical heat storage body and the variable diameter outlet is the same as the cross-sectional area of ​​the gas channel formed between the central column of the heat storage body and the outer cylinder, so that the area of ​​the airflow channel is consistent from front to back.

7. A method for primary air pulverized coal semi-gasification based on the primary air pulverized coal semi-gasification and stable combustion device according to any one of claims 1-6, characterized in that, A portion of the primary air flowing between the first and second pipes enters the inner side of the second pipe along the primary coal powder concentration ring and is ignited in front of the cone at the front of the heat storage body, forming the ignited primary air. A portion of the primary air flowing between the first and second pipes enters the inner side of the second pipe along the secondary coal powder concentration ring, forming a vortex on the outer side of the cone at the front of the heat storage body, which is the vortex primary air. The remaining portion of the primary air between the first tube and the second tube forms a swirling flow on the outside of the heat storage body through the swirling structure, which is called swirling primary air; The ignited primary air, the vortex primary air, and the swirling primary air come into contact with each other and undergo semi-gasification pre-combustion to obtain semi-gasified primary air containing strong reducing gases.

8. The primary air pulverized coal semi-gasification method as described in claim 7, characterized in that, The heat storage body maintains a high temperature, and the pulverized coal around the heat storage body undergoes a semi-gasification process.

9. The primary air pulverized coal semi-gasification method as described in claim 7, characterized in that, The primary air outside the heat storage body is in a swirling state, and the flame spreads evenly.

10. A boiler comprising a primary air pulverized coal semi-gasification stable combustion device as described in any one of claims 1-6, characterized in that, The primary air pulverized coal semi-gasification and stable combustion device is located on the primary air bypass branching off from the primary air main line, and then rejoins the primary air main line, connecting to the primary air inlet of the boiler.

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