Coal powder ammonia-doped combustion device and method with steam preheating and tempering

Abstract

The present application belongs to the field of pulverized coal mixed ammonia combustion, and provides a pulverized coal mixed ammonia combustion device and method with steam preheating conditioning, wherein the device comprises a nozzle and a pipeline assembly connected with the nozzle; the pipeline assembly comprises an ammonia gas pipeline, and a water vapor channel, a pulverized coal and primary air channel, a rotational flow secondary air channel and a tertiary air channel are sequentially and outwardly arranged along the two sides of the ammonia gas pipeline in axial symmetry; the ammonia gas pipeline and the water vapor channel are both provided with a nozzle plate, and the nozzle plate is provided with a nozzle; ammonia gas in the ammonia gas pipeline and water vapor in the water vapor channel converge near the central axis of the burner and are fully mixed. The device can promote ammonia gas pre-decomposition, improve the furnace temperature distribution, and achieve the goal of coal-ammonia layered combustion.

Description

Technical Field

[0001] This invention belongs to the field of pulverized coal combustion with ammonia, and particularly relates to a steam preheating and conditioning device and method for pulverized coal combustion with ammonia. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Given that ammonia contains 82.35% nitrogen by mass, improper combustion methods can lead to a significant conversion of nitrogen into NOx, an atmospheric pollutant. To meet environmental requirements, these pollutants must undergo denitrification treatment using technologies such as SCR, substantially increasing the power generation costs of coal-fired power plants. Furthermore, the flue gas from ammonia-blended combustion contains a large amount of high-temperature water vapor, and direct emission of this vapor results in energy waste. Therefore, utilizing this high-temperature water vapor through ammonia-blended coal combustion with conditioning can synergistically reduce NOx emissions and improve combustion efficiency. However, current technologies primarily utilize water vapor to improve combustion performance under pure coal combustion conditions or for energy storage, without integrating steam extraction with ammonia-coal blending. They merely treat water vapor as an energy storage medium, failing to achieve the desired preheating and conditioning effect to promote complete combustion of ammonia and coal. Summary of the Invention

[0004] In order to solve the technical problems existing in the background art, the present invention proposes a coal powder ammonia-blended combustion device and method with steam preheating and conditioning, which can promote the pre-decomposition of ammonia, improve the furnace temperature distribution, and achieve the goal of coal-ammonia stratified combustion.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A steam preheating and conditioning pulverized coal ammonia-blended combustion device includes:

[0007] The nozzle and the piping assembly connected to the nozzle;

[0008] The pipeline assembly includes an ammonia pipeline, and a water vapor channel, a pulverized coal and primary air channel, a swirling secondary air channel and a tertiary air channel are arranged symmetrically outward along both sides of the ammonia pipeline.

[0009] Both the ammonia gas pipeline and the water vapor channel are equipped with nozzle plates, and the nozzle plates are provided with nozzles; the ammonia gas in the ammonia gas pipeline and the water vapor in the water vapor channel converge near the central axis of the burner and mix thoroughly.

[0010] In one embodiment, the nozzle plate is a showerhead shape.

[0011] As one implementation method, a baffle plate is provided in the tertiary air duct.

[0012] In one implementation method, the swirling secondary air channel has a swirling structure to allow the incoming air to swirl fully, forming swirling secondary air to promote the mixing of pulverized coal and air.

[0013] In one implementation method, the mixing zone of primary and secondary air at the outlet of the pulverized coal and primary air duct forms a high-temperature recirculation zone.

[0014] In one embodiment, the nozzles are evenly arranged on the nozzle plate.

[0015] In one implementation method, the ratio of pulverized coal to primary air in the primary air channel, secondary air in the swirl secondary air channel, and tertiary air in the tertiary air channel is 2:5:3.

[0016] In one implementation method, the wind speeds of the pulverized coal and the primary air in the primary air channel, the secondary air in the swirl secondary air channel, and the tertiary air in the tertiary air channel increase sequentially.

[0017] In one embodiment, the cross-sectional area of ​​the nozzle on the nozzle plate in the ammonia pipeline is larger than the cross-sectional area of ​​the nozzle on the nozzle plate in the steam channel.

[0018] A second aspect of the present invention provides a method for operating a steam preheating and conditioning coal powder ammonia-blended combustion device.

[0019] A method for operating a steam preheating and conditioning pulverized coal ammonia-blended combustion device includes:

[0020] Water vapor transfers some heat to the ammonia gas, a portion of the ammonia gas pre-decomposes to produce NH2 and NH, and the other portion of the pre-decomposed ammonia gas is injected into the burner from the nozzle of the nozzle plate.

[0021] Ammonia undergoes pre-combustion decomposition or oxygen-deficient combustion in the furnace. Water vapor surrounding the ammonia passes through a water vapor nozzle. At this time, the high-temperature water vapor acts to isolate the ammonia and pulverized coal, achieving the purpose of ammonia-coal stratified combustion.

[0022] Under the action of the funnel-shaped flare, the pulverized coal outside the steam pipe forms a local recirculation zone at the junction of the primary and secondary air outside the outlet, which entrains the high-temperature secondary air and promotes the pyrolysis and combustion of the pulverized coal.

[0023] Secondary air surrounding the pulverized coal reacts fully with the pulverized coal around the burner, forming a lean combustion zone to further reduce NO production; tertiary air is introduced at the outermost periphery to stabilize the flame shape and protect the inner wall of the burner.

[0024] The beneficial effects of this invention are:

[0025] (1) The present invention uses the heat exchange between water vapor and ammonia to cause partial pre-combustion decomposition of ammonia after it enters the combustion chamber, generating free NH2, NH and H free radicals, which reduces the difficulty of subsequent ammonia ignition and combustion, improves the poor combustion performance of ammonia, and improves the energy utilization efficiency of the system.

[0026] (2) This invention achieves the conditioning effect of water vapor. Water is a triatomic molecule with a large specific heat capacity, which makes the temperature distribution in the furnace more uniform and avoids local overheating zones. In addition, water vapor decomposes into free radicals such as H and OH at high temperatures. These free radicals can inhibit the conversion of key intermediates such as HCN and HNO into NO during the ammonia-coal blending combustion process. x Oxidation, thereby reducing NO x The amount of nitrogen generated reduces the cost of subsequent selective non-catalytic reduction denitrification processes and improves the economic efficiency of coal-fired power plants.

[0027] (3) This invention achieves stratified combustion of ammonia and coal through the isolation effect of water vapor. Ammonia pre-burns and decomposes near the central axis of the burner, while coal pyrolyzes and burns on the outer side. The two are separated by water vapor, avoiding the generation of a large amount of NO during the coupled combustion process. x The outermost pulverized coal burns first, and some of the heat released during combustion provides a reliable thermal atmosphere for the decomposition and combustion of ammonia through heat conduction. The outermost coal rapidly consumes oxygen in the secondary air, resulting in a lean combustion zone for ammonia. Under this condition, the nitrogen in ammonia tends to form non-toxic and harmless N2, rather than NO as in a rich combustion zone. x This design, while ensuring a reduction in CO2 emissions, further reduces NO emissions. x The generation of this technology, compared to direct ammonia-coal blending and combustion, has improved operational stability and flexibility.

[0028] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] 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.

[0030] Figure 1 This is a high-temperature steam preheating and conditioning coal powder ammonia-blended combustion device according to an embodiment of the present invention;

[0031] Figure 2 This is the cross-section of the nozzle in an embodiment of the present invention;

[0032] Figure 3 This is the cross-section of the swirl secondary air channel in an embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] It should be noted that the following detailed description is illustrative and intended to provide further explanation 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.

[0035] 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.

[0036] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0037] In this invention, terms such as "fixed connection," "connected," and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0038] according to Figure 1 This invention provides a steam preheating and conditioning coal powder ammonia-blended combustion device, comprising: a nozzle and a pipeline assembly connected to the nozzle;

[0039] The pipeline assembly includes an ammonia pipeline, and a water vapor channel, a pulverized coal and primary air channel, a swirling secondary air channel and a tertiary air channel are arranged symmetrically outward along both sides of the ammonia pipeline.

[0040] Both the ammonia gas pipeline and the water vapor channel are equipped with nozzle plates, and the nozzle plates are evenly distributed with nozzles.

[0041] The nozzle plate is in the shape of a shower head. A baffle is installed in the tertiary air duct.

[0042] In this embodiment of the invention, the ammonia gas pipeline is surrounded by a steam pipeline (the steam can originate from the exhaust steam of the low-pressure cylinder of the steam turbine, with a temperature of approximately 100℃-200℃). Small holes on the nozzle plate at the end of the steam pipeline improve the rigidity of the steam jet. Surrounding the steam pipeline is a pulverized coal pipeline through which coal enters the burner. Surrounding the pulverized coal pipeline are secondary air pipelines and tertiary air pipelines.

[0043] The cross-section of this device is a concentric circle, such as Figure 2 As shown, ammonia, steam, pulverized coal, and primary, secondary, and tertiary air are introduced from the inside out.

[0044] The combustion details of the material are as follows:

[0045] In the delivery pipeline, the water vapor surrounding the ammonia gas preheats it. The presence of a large amount of water vapor will form hydrogen bonds with the ammonia, thereby reducing the dissociation energy of the NH bond and improving the poor combustion characteristics of ammonia. After passing through the delivery pipeline, the ammonia and water vapor converge near the central axis of the burner and mix thoroughly.

[0046] Furthermore, due to the insulating effect of water vapor, the outer coal powder is not easily in contact with the inner ammonia gas. The heat generated by coal pyrolysis and combustion can provide a reliable thermal atmosphere for ammonia combustion through thermal conduction, thereby achieving the purpose of ammonia-coal stratified combustion and reducing the generation of nitrogen oxides.

[0047] Figure 3 This is the cross-section of the swirling secondary air nozzle. This cross-section design allows the incoming air to swirl fully, forming swirling secondary air to promote the mixing of fuel and air, and improves flame stability by establishing a high-temperature recirculation zone in the primary and secondary air mixing area at the outlet.

[0048] The outermost tertiary airflow serves to stabilize the flame shape and protect the inner wall of the burner.

[0049] In practice, the swirling secondary air channel has a swirling structure to ensure that the incoming air swirls fully, forming swirling secondary air that promotes the mixing of pulverized coal and air. The mixing zone between the primary and secondary air at the outlet of the primary air channel forms a high-temperature recirculation zone.

[0050] In this embodiment, the ratio of pulverized coal to primary air in the primary air channel, secondary air in the swirl secondary air channel, and tertiary air in the tertiary air channel is 2:5:3. The air velocities of pulverized coal to primary air in the primary air channel, secondary air in the swirl secondary air channel, and tertiary air in the tertiary air channel increase sequentially.

[0051] In this embodiment, the nozzles are evenly arranged on the nozzle plate. The cross-sectional area of ​​the nozzles on the nozzle plate in the ammonia gas pipeline is larger than that of the nozzles on the nozzle plate in the water vapor channel.

[0052] The detailed calculations of the proportions of each nozzle are as follows:

[0053] Taking a 600 MW coal-fired boiler as an example, with an ammonia blending ratio of 20 cal.%, a boiler thermal efficiency of 93%, ammonia lower heating value of 18.60 MJ / kg, coal lower heating value of 20.9 MJ / kg, excess air coefficient of 1.2, and primary air, secondary air and tertiary air accounting for 20%, 50% and 30% respectively, and water vapor calculated as 5% of the ammonia flow rate. Furthermore, to prevent pipeline corrosion caused by excessively rapid material flow and to ensure thorough mixing, based on empirical values, the injection velocity of ammonia into the furnace is approximately 30-60 m / s, steam approximately 25-35 m / s, pulverized coal and primary air approximately 15-25 m / s, secondary air approximately 40-60 m / s, and tertiary air approximately 60-80 m / s. Based on these empirical values ​​and the aforementioned primary, secondary, and tertiary air distribution ratios, the ammonia, steam, primary, secondary, and tertiary air nozzles can be designed. The total cross-sectional area of ​​the ammonia nozzle is estimated to be 0.149-0.298 m². 2 The total cross-sectional area of ​​the steam nozzle is 0.018-0.030 m². 2 The cross-sectional area of ​​the pulverized coal and primary air nozzle is 1.72-2.87 m². 2 The cross-sectional area of ​​the secondary air nozzle is 1.79-2.69 m². 2 The cross-sectional area of ​​the tertiary air nozzle is 0.806-1.075 m². 2 .

[0054] The operation process of the combustion device is as follows:

[0055] When the device is operating, steam transfers some heat to the ammonia, causing some ammonia to pre-decompose and produce NH2 and NH. The partially pre-decomposed ammonia is then injected into the burner through several small holes in the nozzle plate. These holes increase the jet velocity, thereby improving flame rigidity. The ammonia undergoes pre-combustion decomposition or oxygen-deficient combustion in the furnace. Steam surrounding the ammonia is injected into the furnace at a high velocity through steam nozzles. At this point, the high-temperature steam acts as a separator between the ammonia and pulverized coal, achieving stratified combustion of ammonia and coal. The pulverized coal outside the steam pipe, under the action of the flared nozzle, forms a local recirculation zone at the junction of the primary and secondary air at the outlet, entraining high-temperature secondary air and promoting the pyrolysis and combustion of the pulverized coal. The secondary air pipe surrounds the pulverized coal, where it reacts fully with the pulverized coal around the burner. Less oxygen enters near the central axis, creating a lean combustion zone that further reduces NO production. Tertiary air is introduced at the outermost edge of the pipe to stabilize the flame shape and protect the inner wall of the burner.

[0056] 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 steam preheating and conditioning coal pulverized with ammonia combustion device, characterized in that, include: The nozzle and the piping assembly connected to the nozzle; The pipeline assembly includes an ammonia pipeline, and a water vapor channel, a pulverized coal and primary air channel, a swirling secondary air channel and a tertiary air channel are arranged outward in the radial direction outside the ammonia pipeline, with each channel arranged coaxially. Both the ammonia gas pipeline and the water vapor channel are equipped with nozzle plates, and the nozzle plates are provided with nozzles; the ammonia gas in the ammonia gas pipeline and the water vapor in the water vapor channel converge near the central axis of the burner and mix thoroughly.

2. The steam preheating and conditioning coal pulverized with ammonia combustion device as described in claim 1, characterized in that, The nozzle plate is lotus-shaped.

3. The steam preheating and conditioning coal pulverized with ammonia combustion device as described in claim 1, characterized in that, A flow guide baffle is installed in the tertiary air duct.

4. The steam preheating and conditioning coal pulverized with ammonia combustion device as described in claim 1, characterized in that, The swirling secondary air channel has a swirling structure to allow the incoming air to swirl fully, forming swirling secondary air to promote the mixing of pulverized coal and air.

5. The steam preheating and conditioning coal pulverized with ammonia combustion device as described in claim 1, characterized in that, The primary and secondary air mixing zone at the outlet of the pulverized coal and primary air duct forms a high-temperature recirculation zone.

6. The steam preheating and conditioning coal pulverized with ammonia combustion device as described in claim 1, characterized in that, The nozzles are evenly arranged on the nozzle plate.

7. The steam preheating and conditioning coal pulverized with ammonia combustion device as described in claim 1, characterized in that, The ratio of pulverized coal to primary air in the primary air channel, secondary air in the swirl secondary air channel, and tertiary air in the tertiary air channel is 2:5:

3.

8. The steam preheating and conditioning coal pulverized with ammonia combustion device as described in claim 1, characterized in that, The wind speeds of the primary air in the pulverized coal and primary air channels, the secondary air in the swirl secondary air channels, and the tertiary air in the tertiary air channels increase sequentially.

9. The steam preheating and conditioning coal pulverized with ammonia combustion device as described in claim 1, characterized in that, The cross-sectional area of ​​the nozzles on the nozzle plate in the ammonia pipeline is larger than that of the nozzles on the nozzle plate in the steam channel.

10. A method for operating a pulverized coal combustion device with ammonia blending based on steam preheating and conditioning as described in any one of claims 1-9, characterized in that, include: Water vapor transfers some heat to the ammonia gas, a portion of the ammonia gas pre-decomposes to produce NH2 and NH, and the other portion of the pre-decomposed ammonia gas is injected into the burner from the nozzle of the nozzle plate. Ammonia undergoes pre-combustion decomposition or oxygen-deficient combustion in the furnace. Water vapor surrounding the ammonia passes through a water vapor nozzle. At this time, the high-temperature water vapor acts to isolate the ammonia and pulverized coal, achieving the purpose of ammonia-coal stratified combustion. Under the action of the funnel-shaped flare, the pulverized coal outside the steam pipe forms a local recirculation zone at the junction of the primary and secondary air outside the outlet, which entrains the high-temperature secondary air and promotes the pyrolysis and combustion of the pulverized coal. Secondary air surrounding the pulverized coal reacts fully with the pulverized coal around the burner, forming a lean combustion zone to further reduce NO production; tertiary air is introduced at the outermost periphery to stabilize the flame shape and protect the inner wall of the burner.

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