Combustion system

Abstract

The present invention discloses a combustion system, which comprises a fluidized bed furnace, a distributor plate, a plurality of tuyeres, a plurality of pipes, a first header, a second header and a plurality of tuyeres. The distributor plate is arranged at the bottom of the fluidized bed furnace. The plurality of tuyeres are arranged on the distributor plate and located inside the fluidized bed furnace. The plurality of tuyeres are arranged in multiple rows at intervals along the width direction of the fluidized bed furnace. Each row includes several tuyeres arranged at intervals along the length direction of the fluidized bed furnace. The tuyeres are adapted to introduce primary air. A pipe is arranged between every two adjacent rows of tuyeres. The pipe has a first pipe and a second pipe that are communicated along its extending direction. The cross-sectional area of the inner peripheral surface of the first pipe gradually increases in a direction away from the second pipe. The cross-sectional area of the inner peripheral surface of the second pipe gradually increases in a direction away from the first pipe. The plurality of tuyeres are arranged on the pipe at intervals along the extending direction of the pipe, and the plurality of tuyeres are communicated with the pipe. The combustion system of the present invention has the advantages of simple structure, low cost, high combustion efficiency, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of clean energy, and specifically relates to a combustion system. Background Art

[0002] Ammonia belongs to a carbon-free energy source. Its large-scale application will strongly promote the low-carbon transformation of the energy system. Compared with hydrogen, which is also a carbon-free energy source, ammonia has a higher volumetric energy density, is more convenient for storage and transportation, and has a more mature industrial chain, showing a bright development prospect.

[0003] In related technologies, the combustion efficiency of ammonia is low and the combustion is unstable. Summary of the Invention

[0004] The present invention is made based on the inventor's discovery and recognition of the following facts and problems:

[0005] In related technologies, considering that directly burning pure ammonia requires overcoming many challenges such as low laminar flame speed of ammonia, difficult ignition, poor combustion stability, and low combustion efficiency, some related technologies choose to co-fire ammonia with fossil fuels that have better combustion performance and more mature equipment design to try to overcome these problems. For example, the invention patent CN115596561A discloses a diesel-ignited high-pressure direct injection liquid ammonia internal combustion engine injection control method and combustion system, which uses diesel flame to ignite liquid ammonia, can improve the problems of difficult ammonia fuel combustion and insufficient reaction, and at the same time allows the internal combustion engine to set a higher compression ratio, thereby improving the power density and thermal efficiency of the internal combustion engine; the invention patent CN113217937A discloses a system and method for reducing carbon dioxide emissions from coal-fired power units by using ammonia combustion, which realizes a certain proportion of coal powder substitution based on ammonia-coal co-firing, thereby reducing the carbon dioxide emission level of coal-fired power units; the invention patent CN217763522U discloses a natural gas-ammonia co-firing combustion system coupled with green hydrogen production of ammonia, which can realize natural gas-ammonia oxygen-enriched carbon reduction and low-nitrogen combustion.

[0006] However, in the long run, to further reduce carbon emissions, using pure ammonia as a fuel for combustion is the future trend. Using a circulating fluidized bed boiler to achieve fluidized bed combustion of ammonia has the characteristics of good heat and mass transfer effects, high combustion stability, low temperature, low pollutant emissions and easy control. Moreover, under the condition of bed material fluidization, the reaction activity may be further enhanced, which can better solve the above challenges of ammonia combustion and is an ideal technology for future pure ammonia combustion. At present, most patents focus on the application of ammonia in fluidized beds for removing NOx pollutants, rather than paying much attention to the application of ammonia as a fuel. At the same time, to enable the stable and efficient fluidized bed combustion of ammonia, it is necessary for ammonia and air in the fluidized bed furnace to contact the bed material surface more fully and evenly to better achieve heterogeneous catalytic reactions. Therefore, it is necessary to scientifically design relevant air distribution systems and methods. However, the descriptions of air distribution in related patents for circulating fluidized bed boilers are mostly about direct mixing, or they are omitted without discussion of layout details, or only discuss the ammonia feeding systems and methods for removing NOx, without considering the differences in air distribution methods when ammonia is used as a fuel for combustion.

[0007] The present invention aims to solve at least one of the technical problems in the related art to a certain extent.

[0008] To this end, an embodiment of the present invention provides a combustion system with high ammonia combustion efficiency, stable combustion and low NOx emissions.

[0009] The combustion system according to an embodiment of the present invention includes: a fluidized bed furnace; a wind distribution plate and a plurality of tuyeres. The wind distribution plate is arranged at the bottom of the fluidized bed furnace, and the plurality of tuyeres are arranged on the wind distribution plate and located inside the fluidized bed furnace. The plurality of tuyeres are arranged in multiple rows at intervals along the width direction of the fluidized bed furnace, and each row includes several tuyeres arranged at intervals along the length direction of the fluidized bed furnace. The tuyeres are adapted to introduce primary air so that the primary air flows into the fluidized bed furnace through the tuyeres; a plurality of pipes. The plurality of pipes extend along the length direction of the fluidized bed furnace and are arranged at intervals along the width direction of the fluidized bed furnace. One pipe is arranged between every two adjacent rows of tuyeres. The pipe has a first pipe and a second pipe that are communicated along its extending direction. The cross-sectional area of the inner peripheral surface of the first pipe gradually increases in a direction away from the second pipe, and the cross-sectional area of the inner peripheral surface of the second pipe gradually increases in a direction away from the first pipe. One end of the first pipe away from the second pipe has a first air inlet, and one end of the second pipe away from the first pipe has a second air inlet. Both the first air inlet and the second air inlet are adapted to introduce ammonia; a first header and a second header. The first header and the second header are arranged at intervals along the length direction of the fluidized bed furnace outside the fluidized bed furnace. Both the first header and the second header extend along the width direction of the fluidized bed furnace. The first air inlet of the first pipe is communicated with the first header, and the second air inlet of the second pipe is communicated with the second header. Both the first header and the second header are adapted to introduce ammonia so that the ammonia is introduced into the pipe through the first header and the second header; a plurality of nozzles. The plurality of nozzles are arranged at intervals along the extending direction of the pipe on the pipe, and the plurality of nozzles are communicated with the pipe so that the ammonia is sprayed into the fluidized bed furnace through the nozzles.

[0010] The combustion system of the embodiment of the present invention is provided with a circulating fluidized bed furnace, pipes and nozzles, so that ammonia can be evenly sent into the furnace and fully mixed with the primary air, thereby creating conditions for the efficient and stable combustion of ammonia fuel in the fluidized bed boiler and low NOx emissions, and improving the combustion efficiency of ammonia.

[0011] In some embodiments, in a projection plane orthogonal to the width direction of the fluidized bed furnace, the projection of the top of the pipe is a horizontal line, and the nozzle is arranged adjacent to the upper end of the pipe.

[0012] In some embodiments, the tuyere includes a first tuyere and a second tuyere. The first tuyere is provided on one side of the pipeline and communicated with the pipeline, so that ammonia in the pipeline flows out through the first tuyere. The second tuyere is provided on the other side of the pipeline and communicated with the pipeline, so that the ammonia in the pipeline flows out through the second tuyere. The first tuyere and the second tuyere are arranged opposite to each other at intervals along the width direction of the fluidized bed furnace.

[0013] In some embodiments, both the first tuyere and the second tuyere extend away from the pipeline and incline downward. The extension direction of the first tuyere and the extension direction of the second tuyere intersect with the horizontal direction and form an angle, and the value range of the angle is 0° to 30°.

[0014] In some embodiments, the first tuyere is located between two adjacent wind caps, and the second tuyere is located between two adjacent wind caps.

[0015] In some embodiments, at least one of the wind cap and the tuyere includes an air outlet pipe and an end cover. The air outlet pipe extends in the vertical direction, and one end of the air outlet pipe is provided at the upper end of the pipeline and communicated with the pipeline. The end cover includes a top and a side surface. The end cover is sleeved on the other end of the air outlet pipe. The top of the end cover is spaced from the other end of the air outlet pipe in the vertical direction, and the side surface of the end cover is spaced from the outer peripheral surface of the air outlet pipe in the inner and outer direction.

[0016] In some embodiments, the combustion system further includes a liquid ammonia tank and a vaporization buffer tank. The liquid ammonia tank is communicated with the vaporization buffer tank, so that liquid ammonia flows into the vaporization buffer tank through the liquid ammonia tank. The vaporization buffer tank is respectively communicated with the first header and the second header, so that ammonia flowing out of the vaporization buffer tank flows into the first header and the second header respectively.

[0017] In some embodiments, the distance between the tuyere and the air distribution plate in the vertical direction is 200 mm to 1000 mm.

[0018] In some embodiments, one pipeline is provided between two adjacent rows of the wind caps, and two adjacent rows of the wind caps are axially symmetric about the pipeline. The distance between the axis of the pipeline and the adjacent wind cap in the width direction of the fluidized bed furnace is 300 mm to 800 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of the combustion system according to the first embodiment of the present invention.

[0020] Figure 2 is a schematic structural diagram of the pipeline of the combustion system according to the first embodiment of the present invention.

[0021] Figure 3 It is a schematic structural diagram of the combustion system according to the second embodiment of the present invention.

[0022] Figure 4 It is a schematic structural diagram of the pipeline of the combustion system according to the second embodiment of the present invention.

[0023] Figure 5 It is a schematic structural diagram of the combustion system according to the third embodiment of the present invention.

[0024] Figure 6 It is a schematic structural diagram of the pipeline of the combustion system according to the third embodiment of the present invention.

[0025] Combustion system 100;

[0026] Air distribution plate 1;

[0027] Air cap 2; Outlet pipe 21; End cover 22;

[0028] Pipeline 3; First pipe 31; Second pipe 32;

[0029] Air nozzle 4; First air nozzle 41; Second air nozzle 42; Liquid ammonia tank 5; Gasification buffer tank 6; First header 7; Second header 8; Fan 9. Detailed implementation manners

[0030] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0031] The combustion system according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0032] As Figures 1-6 shown, the combustion system 100 according to an embodiment of the present invention includes a fluidized bed furnace (not shown in the figure), an air distribution plate 1, a plurality of air caps 2, a plurality of pipelines 3, and a plurality of air nozzles 4.

[0033] The air distribution plate 1 is provided at the bottom of the fluidized bed furnace, and a plurality of air caps 2 are provided on the air distribution plate 1 and are located in the fluidized bed furnace. The plurality of air caps 2 are arranged in multiple rows at intervals in the width direction of the fluidized bed furnace (such as Figure 1 the left - right direction shown), and each row includes several air caps 2 arranged at intervals in the length direction of the fluidized bed furnace (such as Figure 1 the front - back direction shown). The air caps 2 are adapted to introduce primary air so that the primary air flows into the fluidized bed furnace through the air caps 2. Specifically, as Figures 1-6As shown, the air distribution plate 1 is formed at the bottom of the fluidized bed furnace. A plurality of air caps 2 are arranged in multiple rows at equal intervals in the left-right direction, and each row includes several air caps 2 arranged at intervals in the front-back direction. The primary air can flow into the fluidized bed furnace through the air caps 2.

[0034] A plurality of pipes 3 extend along the length direction of the fluidized bed furnace and are arranged at intervals in the width direction of the fluidized bed furnace. One pipe 3 is provided between every two adjacent rows of air caps 2. The pipe 3 has a communicating first pipe 31 and second pipe 32 along its extending direction. The cross-sectional area of the inner peripheral surface of the first pipe 31 gradually increases in the direction away from the second pipe 32, and the cross-sectional area of the inner peripheral surface of the second pipe 32 gradually increases in the direction away from the first pipe 31. One end of the first pipe 31 away from the second pipe 32 has a first air inlet, and one end of the second pipe 32 away from the first pipe 31 has a second air inlet. Both the first air inlet and the second air inlet are adapted to introduce ammonia. Specifically, as Figure 1 、 Figure 3 and Figure 5 shown, a plurality of pipes 3 are arranged at equal intervals in the left-right direction and all extend in the front-back direction. At least one pipe 3 is provided between two adjacent rows of air caps 2, and the pipe 3 is arranged at equal intervals in the left-right direction with the adjacent two rows of air caps 2. The pipe 3 has a communicating first pipe 31 and second pipe 32 along the front-back direction. The rear end surface of the first pipe 31 is communicated with the front end surface of the second pipe 32, and the cross-sectional area of the inner peripheral surface of the first pipe 31 gradually decreases from front to back, and the cross-sectional area of the inner peripheral surface of the second pipe 32 gradually increases from front to back. The front end portion of the first pipe 31 is the first air inlet, and the rear end portion of the second pipe 32 is the second air inlet. By introducing fuel (the proportion of ammonia in the fuel is 100%, that is, it does not burn in mixture with other types of fuel) into the first air inlet and the second air inlet respectively, thus, it can ensure that the pressure of the gas introduced into the first pipe 31 and the second pipe 32 is constant.

[0035] Both the first header 7 and the second header 8 are arranged outside the fluidized bed furnace. The first header 7 and the second header 8 are both arranged at intervals in the length direction of the fluidized bed furnace. The first header 7 and the second header 8 extend in the width direction of the fluidized bed furnace. The first air inlet of the first pipe 31 is communicated with the first header 7, and the second air inlet of the second pipe 32 is communicated with the second header 8. Both the first header 7 and the second header 8 are adapted to introduce ammonia so that ammonia can be introduced into the pipe 3 through the first header 7 and the second header 8. Specifically, as Figure 1 、 Figure 3 and Figure 5 shown, the first header 7 and the second header 8 extend in the left-right direction and are arranged at intervals in the front-back direction. The first pipe 31 is communicated with the first header 7, and the second pipe 32 is communicated with the second header 8, so that ammonia can be transported to a plurality of first pipes 31 and a plurality of second pipes 32 through the first header 7 and the second header 8.

[0036] A plurality of tuyeres 4 are arranged on the pipeline 3 at intervals along the extending direction of the pipeline 3. The plurality of tuyeres 4 are communicated with the pipeline 3 so that ammonia gas is sprayed into the fluidized bed furnace through the tuyeres 4. Specifically, as Figures 1~6 shown, a plurality of tuyeres 4 are provided on each pipeline 3. The plurality of tuyeres 4 are arranged at intervals in the front-rear direction. Since the ammonia gas pressure in the first pipeline 31 and the second pipeline 32 is equal everywhere, the ammonia gas ejected from each tuyere 4 can also be made equal, so that the ammonia gas in the furnace can be in full and uniform contact with the surface of the bed material in the furnace to better realize the heterogeneous catalytic reaction. In other words, the bed material in the furnace is fluidized under the action of ammonia gas and air, providing a large amount of bed material surfaces that can catalyze the ammonia oxidation reaction and further react with NOx, thereby realizing the heterogeneous catalytic effect on ammonia combustion, which can greatly improve the combustion characteristics of ammonia.

[0037] In the combustion system 100 of the embodiment of the present invention, a fluidized bed furnace is provided. Since there are a large number of solid bed materials in a fluidized state in the fluidized bed furnace under the fluidized bed environment, the heat transfer and mass transfer in the ammonia combustion process are strengthened, and the surfaces of these bed materials may have significant catalytic activity for ammonia oxidation and NOx reduction, which significantly promotes the ignition and burnout of ammonia within a limited residence time, and at the same time realizes low NOx emissions. Therefore, pure ammonia gas can be introduced into the circulating fluidized bed furnace for full combustion. By setting the pipeline 3 and the tuyeres 4, good mixing of ammonia gas and primary air before combustion is realized, and the flow field and temperature field in the fluidized bed furnace are better organized, thereby laying a foundation for realizing stable and efficient combustion of ammonia, improving the combustion characteristics of ammonia gas, and increasing the combustion efficiency of ammonia gas.

[0038] In some embodiments, in the projection plane orthogonal to the width direction of the fluidized bed furnace, the projection of the top of the pipeline 3 is a horizontal line, and the tuyere 4 is arranged adjacent to the upper end of the pipeline 3. Specifically, as Figure 2 、 Figure 4 and Figure 6 shown, the cross-sectional area of the inner peripheral surface of the pipeline 3 first decreases and then increases from front to back with its top as the reference. In other words, the pipeline 3 is scaled around its upper end surface, and the tuyere 4 is arranged adjacent to the upper end of the pipeline 3. It is necessary to ensure that the tuyere 4 ports are at the same height, and further ensure that the ammonia gas pressures ejected from the pipeline 3 are equal. Therefore, scaling the pipeline 3 around the lower end surface can more conveniently set the tuyere 4 ports without lengthening or shortening the tuyeres 4 of the pipeline 3, thereby reducing the manufacturing cost of the pipeline 3.

[0039] In some embodiments, the tuyere 4 includes a first tuyere 41 and a second tuyere 42. The first tuyere 41 is arranged on one side of the pipeline 3 and communicated with the pipeline 3 so that the ammonia gas in the pipeline 3 flows out through the first tuyere 41. The second tuyere 42 is arranged on the other side of the pipeline 3 and communicated with the pipeline 3 so that the ammonia gas in the pipeline 3 flows out through the second tuyere 42. The first tuyere 41 and the second tuyere 42 are arranged opposite to each other at intervals in the width direction of the fluidized bed furnace. Specifically, asFigure 2 , Figure 4 and Figure 6 As shown in Figure 6 , the first air nozzle 41 is provided at the upper left end of the duct 3, and the second air nozzle 42 is provided at the upper right end of the duct 3. Moreover, the first air nozzle 41 and the second air nozzle 42 are symmetric about the axis of the duct 3. Thus, ammonia gas is sprayed onto the air cap 2 on the left side of the duct 3 through the first air nozzle 41, and ammonia gas is sprayed onto the air cap 2 on the right side of the duct 3 through the second air nozzle 42, making the distribution of ammonia gas in the furnace more uniform.

[0040] In some embodiments, both the first air nozzle 41 and the second air nozzle 42 extend in a direction away from the duct 3 and incline downward. The extending directions of the first air nozzle 41 and the second air nozzle 42 intersect with the horizontal direction and form an angle, and the value range of the angle is 0° to 30°. Specifically, as shown in Figure 2 and Figure 6 shown, the first air nozzle 41 extends toward the lower left, and the second air nozzle 42 extends toward the lower right. The angles between the first air nozzle 41 and the second air nozzle 42 and the horizontal line can be any one of 0°, 10°, 20°, 30°, etc. If the angles between the first air nozzle 41 and the second air nozzle 42 and the horizontal line are less than 0°, it will cause the first air nozzle 41 and the second air nozzle 42 to incline upward, making the ammonia gas and the primary air sprayed into the fluidized bed furnace almost in the same direction, resulting in difficulty in promoting the mixing of ammonia gas and the primary air. When the angles between the first air nozzle 41 and the second air nozzle 42 and the horizontal line are greater than 30°, it will cause the ammonia gas and the air to collide and then react violently, resulting in damage to the duct 3 and the air cap 2. Therefore, when the value range of the angle is between 0° and 30°, the best mixing effect and combustion performance of ammonia gas and the primary air can be obtained.

[0041] In some embodiments, the first air nozzle 41 is located between two adjacent air caps 2, and the second air nozzle 42 is located between two adjacent air caps 2. Specifically, as shown in Figure 4 and Figure 6 shown, the first air nozzle 41 on the duct 3 is staggeredly arranged with the air cap 2 on the left side of the duct 3 in the front-back direction, and the second air nozzle 42 on the duct 3 is staggeredly arranged with the air cap 2 on the right side of the duct 3 in the front-back direction, thereby improving the uniformity of the mixing of ammonia gas and the primary air and ensuring the feeding of ammonia gas under a relatively high flow rate.

[0042] In some embodiments, at least one of the air cap 2 and the air nozzle 4 includes an air outlet pipe 21 and an end cap 22. The air outlet pipe 21 extends in the up-down direction, and one end of the air outlet pipe 21 is provided at the upper end of the duct 3 and communicated with the duct 3. The end cap 22 includes a top and a side surface. The end cap 22 is sleeved on the other end of the air outlet pipe 21. The top of the end cap 22 is spaced from the other end of the air outlet pipe 21 in the up-down direction, and the side surface of the end cap 22 is spaced from the outer peripheral surface of the air outlet pipe 21 in the in-out direction. Specifically, as shown in Figure 2 , Figure 4 and Figure 6As shown, the outlet pipe 21 extends in the vertical direction, and the lower end of the outlet pipe 21 is connected to the upper end of the pipe 3 and is in communication with the pipe 3, so that ammonia flows out through the upper end of the outlet pipe 21. The end cap 22 covers the upper end of the outlet pipe 21, and the inner peripheral surface of the end cap 22 is spaced from the outer peripheral surface of the outlet pipe 21 to form an air outlet channel. Ammonia or primary air can flow out through the air outlet channel. The setting of the end cap 22 can cause ammonia or primary air to diffuse circumferentially along the outlet pipe 21, so that ammonia and primary air flow into the furnace evenly, thereby enabling the primary air and ammonia to be fully mixed.

[0043] It should be noted that the end cap 22 and the outlet pipe 21 can be connected by a rib plate (not shown in the figure). One end of the rib plate is welded to the outer peripheral surface of the outlet pipe 21, and the other end of the rib plate is welded to the side surface of the end cap 22. The present invention will not be described in detail.

[0044] In some embodiments, the combustion system 100 further includes a liquid ammonia tank 5 and a vaporization buffer tank 6. The liquid ammonia tank 5 is in communication with the vaporization buffer tank 6 so that liquid ammonia can flow from the liquid ammonia tank 5 into the vaporization buffer tank 6. The vaporization buffer tank 6 is respectively in communication with the first header 7 and the second header 8 so that ammonia flowing out of the vaporization buffer tank 6 can flow into the first header 7 and the second header 8 respectively. Specifically, as Figure 1 、 Figure 3 and Figure 5 shown, the outlet of the liquid ammonia tank 5 is connected to the inlet of the vaporization buffer tank 6, so that ammonia can flow from the liquid ammonia tank 5 into the vaporization buffer tank 6. The liquid ammonia is vaporized by the vaporization buffer tank 6, and the vaporized ammonia flows into the first header 7 and the second header 8, and flows into the first pipe 31 and the second pipe 32 through the first header 7 and the second header 8. Thus, the pressure of ammonia in the first pipe 31 and the second pipe 32 is further ensured to be equal.

[0045] In some embodiments, the distance between the tuyere 4 and the air distribution plate 1 in the vertical direction is 200 mm to 1000 mm. Specifically, the vertical distance between the tuyere 4 and the air distribution plate 1 can be one of 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1000 mm, etc. If the distance is too large, that is, the tuyere 4 is too far from the air distribution plate 1, it will waste the fluidized bed furnace space and bring high material costs at the same time. If the distance is too small, ammonia and air may react violently quickly after leaving the tuyere 4, burning out the wind cap 2 and the tuyere 4. Therefore, the distance between the tuyere 4 and the air distribution plate 1 in the vertical direction is 200 mm to 1000 mm, which can make the combustion system 100 more reasonably arranged.

[0046] In some embodiments, a pipe 3 is provided between two adjacent exhaust hoods 2, and the two adjacent exhaust hoods 2 are axially symmetric about the pipe 3. The distance between the axis of the pipe 3 and the adjacent exhaust hood 2 in the width direction of the fluidized bed furnace is 300 mm to 800 mm. Specifically, as Figure 2 , Figure 4 and Figure 6 shown, only one pipe 3 is provided between two adjacent exhaust hoods 2, and the exhaust hood 2 on the left side of the pipe 3 and the exhaust hood 2 on the right side of the pipe 3 are symmetric about the axis of the pipe 3. The distance between the exhaust hood 2 on the left side and the axis of the pipe 3 in the left-right direction is 300 mm to 800 mm, and the distance between the exhaust hood 2 on the right side and the axis of the pipe 3 in the left-right direction is 300 mm to 800 mm. If the distance is too large, it will be difficult for ammonia and primary air to be effectively mixed, and the space on the air distribution plate 1 will be wasted. If the distance is too small, the flow resistance of ammonia and primary air will increase, and at the same time, it also means an increase in the combustion cost of the combustion system 100. Therefore, the distance between the tuyere 4 and the air distribution plate 1 in the up-down direction is 300 mm to 800 mm, which can make the combustion system 100 more reasonably arranged.

[0047] The combustion system 100 of the embodiments of the present invention will be specifically described below.

[0048] Embodiment 1:

[0049] As Figures 1-2 shown, the present invention provides a combustion system 100. The system includes a liquid ammonia tank 5, a vaporization buffer tank 6, a first header 7, a second header 8, an air distribution plate 1, an exhaust hood 2, a pipe 3, a tuyere 4, a blower 9, etc.

[0050] In this embodiment, an ammonia combustion fluidized bed air distribution method based on the above system includes the following steps: Liquid ammonia starts from the liquid ammonia tank 5, is converted into a gaseous state after passing through the vaporization buffer tank 6, and is sent into the furnace bottom through the first header 7 or the second header 8 and the pipe 3 in sequence, and is blown into the fluidized bed furnace through the tuyere 4, and is mixed and burned with the primary air blown from the blower 9 through the exhaust hood 2 on the air distribution plate 1. The bed material in the furnace fluidizes under the action of ammonia and air, providing a large number of bed material surfaces that can catalyze the ammonia oxidation reaction and further react with NOx, thereby realizing the heterogeneous catalytic effect on ammonia combustion, which can greatly improve the combustion characteristics of ammonia.

[0051] The core of the present invention is to realize the combustion of pure ammonia fuel under fluidized conditions, ensure that the fuel is 100% ammonia, and does not co-fire with other fuels, truly realizing zero carbon emissions.

[0052] In the method of the present invention, to further promote the adsorption, heterogeneous catalysis, and desorption of ammonia and air on the surface of the bed material, there are relatively high requirements for the flow field and concentration field of ammonia and air in the fluidized bed furnace. This requires ammonia to be fed into the fluidized bed furnace as evenly as possible and fully mixed with air. Therefore, to achieve the spatial uniformity of ammonia feeding, the system adopts multiple pipes 3. Each pipe 3 extends along the length direction of the fluidized bed furnace and is arranged at intervals along the width direction of the fluidized bed furnace. A pipe 3 is provided between every two adjacent rows of air caps 2. At the same time, referring to the arrangement of the air caps 2 in the fluidized bed furnace of a traditional circulating fluidized bed boiler, the distance between the axis of the pipe 3 and the adjacent air cap 2 in the width direction of the fluidized bed furnace is set to be 300 mm to 800 mm. If the distance is too large, it will lead to difficulty in effectively mixing ammonia and primary air, and waste the space on the air distribution plate 1. If the distance is too small, it will cause an increase in the flow resistance of ammonia and primary air, and at the same time, it also means an increase in the combustion cost of the combustion system 100. Thus, the distance between the air nozzle 4 and the air distribution plate 1 in the up and down direction is 300 mm to 800 mm, which can make the combustion system 100 more reasonably arranged. In addition, the pipe 3 has a first pipe 31 and a second pipe 32 that are connected along its extending direction. The cross-sectional area of the inner peripheral surface of the first pipe 31 gradually increases in the direction away from the second pipe 32, and the cross-sectional area of the inner peripheral surface of the second pipe 32 gradually increases in the direction away from the first pipe 31. One end of the first pipe 31 away from the second pipe 32 has a first air inlet, and one end of the second pipe 32 away from the first pipe 31 has a second air inlet. Both the first air inlet and the second air inlet are suitable for introducing ammonia. Thus, it can be ensured that the pressure of the gas introduced into the first pipe 31 and the second pipe 32 is a constant. The specifications of the pipe 3 depend on data such as the feeding pressure of ammonia, the size and spacing of the air nozzles 4, and the internal roughness of the pipe, and need to be further determined and adjusted according to the boiler load and the experience during the actual operation process.

[0053] In the method of the present invention, the air nozzle 4 is used to spray ammonia from the pipe 3 into the fluidized bed furnace. Referring to the design of the air caps 2 in the fluidized bed furnace of a traditional circulating fluidized bed boiler, the shape of this air nozzle 4 is similar to the air caps 2 on the air distribution plate 1 and is arranged parallel to these air caps 2. On the one hand, it prevents the bed material in the fluidized bed furnace from leaking into the pipe 3, and on the other hand, it can also ensure the uniformity of ammonia feeding. The distance between the air nozzle 4 and the air distribution plate 1 in the up and down direction is 200 mm to 1000 mm. If the distance is too large, that is, the air nozzle 4 is too far from the air distribution plate 1, it will waste the space in the fluidized bed furnace and bring high material costs. If the distance is too small, ammonia and air may react rapidly and violently after leaving the air nozzle 4, burning out the air caps 2 and the air nozzle 4.

[0054] Example 2:

[0055] As Figures 3-4As shown, further, based on the above-mentioned Embodiment 1, the present invention also provides an improved combustion system 100. In addition to the components in Embodiment 1, in Embodiment 2, the original air nozzle 4 is changed to a horizontal air nozzle 4, which includes a first air nozzle 41 and a second air nozzle 42.

[0056] In this embodiment, to ensure the uniformity of the ammonia and air mixture and ensure the ammonia feed at a relatively high flow rate, the first air nozzle 41 and the second air nozzle 42 are arranged opposite to each other at intervals along the width direction of the fluidized bed furnace. The first air nozzle 41 is arranged at the upper left end of the pipeline 3, and the second air nozzle 42 is arranged at the upper right end of the pipeline 3. Moreover, the first air nozzle 41 and the second air nozzle 42 are symmetric about the axis of the pipeline 3. The first air nozzle 41 is located between two adjacent air caps 2, and the second air nozzle 42 is located between two adjacent air caps 2. Both the first air nozzle 41 and the second air nozzle 42 extend in a direction away from the pipeline 3 and incline downward. The extending directions of the first air nozzle 41 and the second air nozzle 42 intersect with the horizontal direction and form an angle, and the value range of the angle is 0° to 30°. If the angle between the first air nozzle 41 and the second air nozzle 42 and the horizontal line is less than 0°, it will cause the first air nozzle 41 and the second air nozzle 42 to incline upward, so that ammonia gas and the primary air are almost sprayed into the fluidized bed furnace in the same direction, making it difficult for ammonia gas and the primary air to promote mixing. When the angle between the first air nozzle 41 and the second air nozzle 42 and the horizontal line is greater than 30°, it will cause ammonia gas and air to collide and then react violently, resulting in damage to the pipeline 3 and the air cap 2. Therefore, when the value range of the angle is between 0° and 30°, the best mixing effect and combustion performance of ammonia gas and the primary air can be obtained.

[0057] Same as Embodiment 1, the distance between the air nozzle 4 and the air distribution plate 1 in the vertical direction is 200 mm to 1000 mm.

[0058] Embodiment 3:

[0059] As Figures 5-6 shown, further, based on the above-mentioned Embodiment 2, the present invention also provides an improved combustion system 100. In addition to the components in Embodiment 2, in Embodiment 3, the air nozzle 4 in System 1 and the original horizontal air nozzle 4 in Embodiment 2 are used simultaneously, which can adapt to a higher ammonia feed flow rate and boiler load; same as Embodiment 1, the distance between each air nozzle 4 and the air distribution plate 1 in the vertical direction is 200 mm to 1000 mm.

[0060] The combustion system of the present invention utilizes the advantages of good heat and mass transfer and high combustion stability in the combustion of a circulating fluidized bed boiler. At the same time, there may be a heterogeneous catalytic effect on the reaction on the surface of the bed material, so as to solve the problems of low laminar flame speed of ammonia combustion, difficult ignition, poor combustion stability, and low combustion efficiency. However, the improvement of ammonia combustion performance by this effect depends on the concentration distribution of ammonia gas and primary air, and thus depends on the ammonia feeding method to ensure the uniform distribution of ammonia gas and primary air in the furnace, thereby overcoming the problems of low laminar flame speed of ammonia, difficult ignition, and poor combustion stability.

[0061] In summary, in the combustion system of the embodiment of the present invention, liquid ammonia is set to start from the liquid ammonia tank 5, be converted into gas after passing through the gasification buffer tank 6, and then be sent into the furnace bottom through the first header 7 or the second header 8 and the pipeline 3 in sequence, and blown into the fluidized bed furnace through the tuyere 4, and mixed and burned with the primary air blown from the blower 9 through the air cap 2 on the air distribution plate 1. At the same time, the flue gas fluidizes the bed material in the furnace. While strengthening the heat and mass transfer process in the furnace and improving the combustion stability, the heterogeneous catalytic effect on ammonia combustion can be realized. By controlling the ammonia feeding site, direction, flow rate, pressure, equivalence ratio, etc., good mixing of ammonia gas and air can be achieved, which is beneficial to the ignition, burnout, and stable combustion of ammonia. At the same time, the internal flow field and temperature field in the furnace can be better organized, thereby effectively reducing the NOx emission of ammonia combustion. The present invention takes into account high combustion efficiency, high uniformity of the flow field and temperature field, and low NOx emission, thus laying a foundation for the circulating fluidized bed boiler system for pure ammonia combustion, strongly promoting the large-scale utilization of ammonia fuel and the ammonia combustion transformation of the traditional coal-fired circulating fluidized bed boiler system, and promoting the transformation and upgrading of the energy system to reduce emissions and carbon.

[0062] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0063] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0064] In the present invention, unless otherwise clearly defined or limited, terms such as "installed", "connected", "joined", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0065] In the present invention, unless otherwise clearly defined or limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature is at a higher level than the second feature in terms of horizontal height. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature is at a lower level than the second feature in terms of horizontal height.

[0066] In the present invention, terms such as "one embodiment", "some embodiments", "example", "specific example" or "some examples", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0067] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A combustion system, characterized in that, Comprising: Fluidized bed furnace; Air distribution plate and a plurality of tuyeres, the air distribution plate is arranged at the bottom of the fluidized bed furnace, and the plurality of tuyeres are arranged on the air distribution plate and located inside the fluidized bed furnace. The plurality of tuyeres are arranged in multiple rows at intervals along the width direction of the fluidized bed furnace, and each row includes several tuyeres arranged at intervals along the length direction of the fluidized bed furnace. The tuyeres are adapted to introduce primary air so that the primary air flows into the fluidized bed furnace through the tuyeres; A plurality of pipes, the plurality of pipes extend along the length direction of the fluidized bed furnace and are arranged at intervals along the width direction of the fluidized bed furnace. One pipe is arranged between every two adjacent rows of tuyeres. The pipe has a first pipe and a second pipe that are connected along its extending direction. The cross-sectional area of the inner peripheral surface of the first pipe gradually increases in the direction away from the second pipe, and the cross-sectional area of the inner peripheral surface of the second pipe gradually increases in the direction away from the first pipe. One end of the first pipe away from the second pipe has a first air inlet, and one end of the second pipe away from the first pipe has a second air inlet. Both the first air inlet and the second air inlet are adapted to introduce ammonia; A first header and a second header, the first header and the second header are arranged at intervals along the length direction of the fluidized bed furnace outside the fluidized bed furnace. The first header and the second header both extend along the width direction of the fluidized bed furnace. The first air inlet of the first pipe is communicated with the first header, and the second air inlet of the second pipe is communicated with the second header. Both the first header and the second header are adapted to introduce ammonia so that the ammonia is introduced into the pipe through the first header and the second header; A plurality of nozzles, the plurality of nozzles are arranged at intervals along the extending direction of the pipe on the pipe, and the plurality of nozzles are communicated with the pipe so that the ammonia is sprayed into the fluidized bed furnace through the nozzles.

2. The combustion system according to claim 1, wherein In the projection plane orthogonal to the width direction of the fluidized bed furnace, the projection of the top of the pipe is a horizontal line, and the nozzles are arranged adjacent to the upper end of the pipe.

3. The combustion system according to claim 1, characterized in that, The nozzle includes a first nozzle and a second nozzle. The first nozzle is arranged on one side of the pipe and is communicated with the pipe so that the ammonia in the pipe flows out through the first nozzle. The second nozzle is arranged on the other side of the pipe and is communicated with the pipe so that the ammonia in the pipe flows out through the second nozzle. The first nozzle and the second nozzle are arranged opposite to each other at intervals along the width direction of the fluidized bed furnace.

4. The combustion system according to claim 3, wherein Both the first nozzle and the second nozzle extend in a direction away from the pipe and are inclined downward. The extending direction of the first nozzle and the extending direction of the second nozzle intersect with the horizontal direction and form an angle, and the value range of the angle is 0° to 30°.

5. The combustion system according to claim 3, characterized in that, The first nozzle is located between two adjacent tuyeres, and the second nozzle is located between two adjacent tuyeres.

6. The combustion system according to any one of claims 1-5, characterized in that, At least one of the tuyere and the nozzle includes an air outlet pipe and an end cover. The air outlet pipe extends in the vertical direction, and one end of the air outlet pipe is arranged at the upper end of the pipe and is communicated with the pipe. The end cover includes a top and a side surface. The end cover is sleeved on the other end of the air outlet pipe. The top of the end cover is spaced from the other end of the air outlet pipe in the vertical direction, and the side surface of the end cover is spaced from the outer peripheral surface of the air outlet pipe in the inner and outer direction.

7. The combustion system according to claim 1, characterized in that, It further includes an ammonia tank and a vaporization buffer tank. The ammonia tank is communicated with the vaporization buffer tank so that ammonia flows into the vaporization buffer tank through the ammonia tank. The vaporization buffer tank is respectively communicated with the first header and the second header so that ammonia flowing out of the vaporization buffer tank flows into the first header and the second header respectively.

8. The combustion system according to claim 1, characterized in that, The distance between the air nozzle and the air distribution plate in the vertical direction is 200 mm to 1000 mm.

9. The combustion system according to claim 1, characterized in that, One such pipe is provided between two adjacent rows of the air caps, and the two adjacent rows of the air caps are axially symmetric about the pipe. The distance between the axis of the pipe and the adjacent air cap in the width direction of the fluidized bed furnace is 300 mm to 800 mm.

Images