High-efficiency low-nitrogen combustion system of biomass grate furnace based on primary air through-hole transformation

Abstract

This invention discloses a high-efficiency, low-NOx combustion system for a biomass grate furnace based on modifications to the primary air vents. Belonging to the field of biomass combustion technology, it includes a vibrating grate. The grate unit is divided into a side grate unit and a central grate unit in the width direction, and the combustion zone of the grate unit is divided into three combustion zones in the length direction. This allows for optimized design of the dimensions of the primary air vents in both the width and length directions, fully utilizing the combustion characteristics of biomass fuel in the grate furnace to effectively ensure complete combustion of biomass fuel in all parts of the vibrating grate. The high-efficiency, low-NOx combustion system for a biomass grate furnace of this invention has a simple structure and convenient control. It can achieve high-efficiency, low-NOx combustion of biomass fuel in the grate furnace, improving combustion efficiency, reducing nitrogen oxide production, fully utilizing the heat of biomass fuel, reducing the use of fossil fuels, and is energy-saving and environmentally friendly. It has good practical value and application prospects.

Description

Technical Field

[0001] This invention belongs to the field of biomass combustion technology, specifically relating to a high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air passage modification. Background Technology

[0002] As the only renewable energy source that can be directly converted into fuel, direct combustion technology is the main way for biomass fuel to be used on a large scale at present. Grate furnace combustion has become the most important boiler combustion form for biomass direct combustion due to its good fuel flexibility.

[0003] However, due to the significant seasonal and regional fluctuations in biomass fuel types, coupled with the complexity of boiler operating systems, combustion often fails to achieve the desired results under existing air and fuel distribution parameters. Furthermore, the operation of existing combustion systems is typically manual, and operators are prone to errors and delays in adjusting air distribution parameters. This frequently results in low boiler combustion efficiency and severely excessive emissions, hindering the efficient operation of the entire combustion system and limiting the application and promotion of biomass fuels. Summary of the Invention

[0004] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a high-efficiency low-NOx combustion system for biomass grate furnaces based on the modification of primary air passages, which can effectively improve the combustion quality of biomass fuel in grate furnaces, increase the combustion efficiency of biomass fuel, and reduce NOx pollutants generated during the combustion of biomass fuel.

[0005] To achieve the above objectives, the present invention provides a high-efficiency, low-NOx combustion system for a biomass grate furnace based on the modification of the primary air passage, comprising a first furnace chamber for biomass fuel combustion, wherein a vibrating grate is provided at the bottom of the first furnace chamber, and a feeding assembly, a primary air supply assembly, and a secondary air supply assembly are provided on the chamber body corresponding to the vibrating grate.

[0006] The feeding assembly is located between the secondary air supply assembly and the vibrating grate, and is used to supply biomass fuel to the vibrating grate; the primary air supply assembly is located at the bottom of the first furnace chamber, and is used to supply air to the bottom of the biomass fuel supported on the vibrating grate through the vibrating grate; the secondary air supply assembly is located above the vibrating grate, and is used to supply air to the top of the biomass fuel.

[0007] The vibrating grate includes a plurality of grate units arranged sequentially in the width direction. The plurality of grate units include two lateral grate units located on both sides in the width direction and a central grate unit located between the two lateral grate units.

[0008] Each of the aforementioned grate units is divided into a first combustion zone, a second combustion zone, and a third combustion zone from one end closest to the feeding assembly to the other end, and each combustion zone is provided with multiple primary air passages; and

[0009] In the same combustion zone, the size of the primary air passage of the central grate unit is larger than that of the primary air passage of the side grate units; and

[0010] Within the same grate unit, the size of the primary air passage in the second combustion zone, the first combustion zone, and the third combustion zone decreases sequentially.

[0011] As a further improvement of the present invention, the feeding assembly includes multiple feeding ports, each corresponding to a grate unit; and

[0012] The feed inlet size of the side grate unit is smaller than the feed inlet size of the middle grate unit; and / or, the feeding rate in the feed inlet of the side grate unit is smaller than the feeding rate in the feed inlet of the middle grate unit.

[0013] As a further improvement of the present invention, the central grate unit consists of two units arranged side by side.

[0014] As a further improvement of the present invention, the primary air passages in the same combustion zone of each side grate unit are of equal size;

[0015] The primary air passages of each central grate unit located in the same combustion zone have the same size.

[0016] As a further improvement of the present invention, for the same grate unit, the size of the primary air passage in the second combustion zone is 1.3 to 1.8 times the size of the primary air passage in the first combustion zone; the size of the primary air passage in the first combustion zone is 1.2 to 1.8 times the size of the primary air passage in the third combustion zone.

[0017] As a further improvement of the present invention, for the same combustion zone, the size of the primary air passage in the middle grate unit is preferably 1.2 to 1.5 times that of the primary air passage in the side grate unit.

[0018] As a further improvement of the present invention, a furnace arch is provided in the middle of the first furnace chamber, which includes a first furnace arch and a second furnace arch connected at the ends and respectively in the shape of a trumpet.

[0019] The opening of the first furnace arch faces downwards, with the furnace wall facing the vibrating grate, and the secondary air supply assembly is installed on the first furnace arch; the opening of the second furnace arch faces upwards.

[0020] As a further improvement of the present invention, the angle between the inner wall surface of the first furnace arch and the horizontal section of the bottom of the first furnace arch is 30° to 60°.

[0021] And / or,

[0022] The angle between the inner wall of the second furnace arch and the cross-section at the connection between the two furnace arches is 100° to 120°.

[0023] As a further improvement of the present invention, the included angle between each grate unit and the horizontal plane is 4° to 10°, and an ash outlet is provided at the bottom of the first furnace chamber at the end of the vibrating grate away from the feeding assembly.

[0024] As a further improvement to the present invention, a second furnace chamber is also included;

[0025] Multiple heat exchangers are arranged sequentially along the flue gas transmission path in the second furnace chamber; and at least one heat exchanger is arranged on the top of the first furnace chamber.

[0026] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0027] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0028] (1) The biomass grate furnace high-efficiency low-NOx combustion system based on primary air passage modification of the present invention includes a vibrating grate. The grate unit is divided into a side grate unit and a middle grate unit in the width direction, and the combustion section of the grate unit is divided into three combustion sections in the length direction. The size of the primary air passage in the width and length directions is optimized and designed to fully combine the combustion characteristics of biomass fuel in the grate furnace, effectively ensure the full combustion of biomass fuel in all parts of the vibrating grate, avoid the occurrence of local oxygen-rich areas, improve the burnout rate of biomass fuel, and make full use of the heat of biomass fuel.

[0029] (2) The biomass grate furnace high-efficiency low-NOx combustion system based on primary air passage modification of the present invention, by setting a furnace arch in the middle of the first furnace chamber, and using the combination of the first furnace arch and the second furnace arch to form a central converging structure, can improve the heat radiation after the biomass fuel is fed and improve the drying efficiency of the biomass fuel in the first combustion zone; while the formation of the second furnace arch is also conducive to avoiding the formation of gas vortex at the top of the first furnace chamber, improving the efficiency and reliability of flue gas transportation, and thus making full use of the heat of biomass fuel.

[0030] (3) The biomass grate furnace high-efficiency low-NOx combustion system based on the modification of primary air passage of the present invention achieves non-uniform feeding in different areas by optimizing the size of primary air passage in different grate units and different combustion sections, coordinating the sequential setting of multiple feed ports in the feeding assembly, and controlling the amount of feed in different feed ports. Furthermore, combined with the actual situation of combustion of each grate unit of the vibrating grate, the combustion effect of biomass fuel is improved.

[0031] (4) The biomass grate furnace high-efficiency low-NOx combustion system based on the modification of the primary air passage of the present invention can make full use of the heat in the combustion flue gas by setting the flue gas conveying channels in the second and third furnace chambers and coordinating the corresponding setting of heat exchangers in each furnace chamber, thereby avoiding heat loss and improving the heat utilization effect.

[0032] (5) The present invention is a biomass grate furnace high-efficiency low-NOx combustion system based on the modification of the primary air passage. It has a simple structure and is easy to control. By optimizing the design of the primary air passage size in the length and width directions of the vibrating grate, and by optimizing the feed port size and / or feed rate in different areas of the feeding assembly, the biomass fuel can be efficiently and low-NOxedly combusted in the grate furnace, improving the combustion efficiency, reducing the generation of nitrogen oxides, making full use of the heat of biomass fuel, reducing the application of fossil energy, saving energy and protecting the environment. It has good practical value and application prospects. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the overall structure of the high-efficiency, low-NOx combustion system of the biomass grate furnace based on the modification of the primary air passage in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the vibrating grate structure of the biomass grate furnace high-efficiency low-NOx combustion system based on the modification of the primary air passage in an embodiment of the present invention.

[0036] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically:

[0037] 1. Primary air supply assembly; 2. Vibrating grate; 3. Feeding assembly; 4. Secondary air supply assembly; 5. Combustion air supply assembly; 6. First heat exchanger; 7. Second heat exchanger; 8. Fourth heat exchanger; 9. Third heat exchanger; 10. Economizer; 11. Flue gas cooler; 12. Flue gas outlet; 13. Ash and slag outlet; 14. Primary air vent; 15. First grate unit; 16. Second grate unit; 17. Third grate unit; 18. Fourth grate unit; 19. First combustion zone; 20. Second combustion zone; 21. Third combustion zone. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0043] Example:

[0044] Please see Figures 1-2 The high-efficiency low-NOx combustion system of biomass grate furnace based on primary air passage modification in the preferred embodiment of the present invention includes a first furnace chamber and a second furnace chamber arranged adjacent to each other, and a third furnace chamber is arranged corresponding to the second furnace chamber, and a flue gas outlet 12 is connected to the bottom of the third furnace chamber.

[0045] Specifically, in the preferred embodiment, the first furnace chamber is used for feeding and combustion of biomass fuel. A vibrating grate 2 is installed at the bottom of the chamber, and a primary air supply assembly 1, a feeding assembly 3, and a secondary air supply assembly 4 are provided corresponding to the vibrating grate 2. The primary air supply assembly 1 is located at the bottom of the vibrating grate 2 and supplies primary combustion air to the biomass material on the vibrating grate 2. The feeding assembly 3 is located on the chamber wall above the vibrating grate 2 and transports biomass fuel to the vibrating grate 2, ensuring that the biomass fuel is laid on the vibrating grate 2 at a certain thickness, thereby completing the combustion and heating process. The secondary air supply assembly 4 is located above the feeding assembly 3 and supplies secondary combustion air to the top of the material carried by the vibrating grate 2.

[0046] Meanwhile, in the preferred embodiment, the first furnace chamber is further specifically a water-cooled vibrating furnace chamber. A vibrating grate 2 is provided at the bottom of the first furnace chamber. One end of the vibrating grate 2 is connected to the wall of the first furnace chamber through a vibration mechanism. The vibrating mechanism can drive each grate unit to vibrate, thereby completing the continuous feeding of biomass materials on the vibrating grate 2.

[0047] More specifically, in the preferred embodiment, a water-cooled pipe is wrapped around the outer periphery of the first furnace chamber, through which a heat exchange substrate is introduced. In the preferred embodiment, the heat exchange substrate is water. By burning biomass fuel in the first furnace chamber, heat is generated, which is absorbed by the heat exchange substrate, causing the cold heat exchange substrate to evaporate into a gaseous state. The gaseous substrate completes the corresponding process and condenses back into the water-cooled pipe after releasing heat.

[0048] Further, in the preferred embodiment, the vibrating grate 2 is disposed at the bottom of the first furnace chamber, and includes multiple grate units arranged sequentially in a first direction (i.e., the width direction of the vibrating grate 2), preferably four in the preferred embodiment. Simultaneously, each grate unit extends along a second direction (i.e., the length direction of the vibrating grate 2), which forms a certain angle with the horizontal direction; that is, the vibrating grate 2 is inclined at a certain angle, preferably 4° to 10°, and extends from the end of the grate unit near the feeding assembly 3 to the end away from the feeding assembly 3, i.e., as shown... Figure 1 The tilt setting is shown.

[0049] Correspondingly, an ash outlet 13 is provided at the end of the vibrating grate 2 opposite to the feeding assembly 3, so that the ash formed after the biomass fuel is burned can be shaken off the vibrating grate 2 to the ash outlet 13, thereby completing the feeding of ash.

[0050] It is easy to see that, in actual setup, the vibrating grate 2 is positioned between the primary air supply assembly 1 and the secondary air supply assembly 4, respectively for supporting the material layered on the vibrating grate 2, while the primary air supply assembly 1 and the secondary air supply assembly 4 respectively supply the oxygen required for combustion to the upper and lower sides of the layered material (biomass fuel).

[0051] More specifically, a furnace arch is provided in the middle of the first furnace chamber, which includes a first furnace arch and a second furnace arch connected at their ends. The two furnace arches are respectively funnel-shaped structures and are connected to each other at the opening with the smallest inner diameter, so that the middle of the first furnace chamber forms a "constricted" shape.

[0052] More specifically, the inner wall surface of the first furnace arch faces the vibrating grate 2, that is, the flared end faces downwards; correspondingly, the inner wall surface of the second furnace arch faces the top of the first furnace chamber, that is, the flared end faces upwards. Preferably, the angle between the inner wall surface of the first furnace arch and the horizontal plane (the horizontal cross-section of the bottom of the first furnace arch) is preferably 30° to 60°, more preferably 45°; the angle between the inner wall surface of the second furnace arch and the cross-section at the connection between the two furnace arches is 100° to 120°.

[0053] like Figure 1 As shown, in the preferred embodiment, the feeding assembly 3 is located below the first furnace arch, and includes multiple feeding ports disposed on the furnace wall of the first furnace chamber. In the preferred embodiment, the number of feeding ports is the same as the number of grate units. For example, in the preferred embodiment, the number of grate units is 4, and correspondingly, the number of feeding ports is also 4, with the two numbers corresponding one-to-one.

[0054] Meanwhile, the feeding assembly 3 is located below the first furnace arch, allowing the material entering the first furnace chamber through each feed port to be dried by thermal radiation from the inner wall of the first furnace arch. This facilitates the rapid evaporation of moisture in the biomass fuel, contributing to improved combustion efficiency. Furthermore, the second furnace arch allows the hot gas passing through both arches to undergo a "compression followed by diffusion" jetting action. This prevents the flue gas from forming vortices at the top of the first furnace chamber, thus avoiding its accumulation there. Instead, the flue gas quickly enters the second furnace chamber through the flue gas passage at the junction of the first and second furnace chambers.

[0055] In addition, to ensure complete combustion of the fuel (partly combustible gases such as CO, H2, and CH4, produced by biomass pyrolysis or coke gasification, and partly unburned biomass pellets) in the flue gas above the second furnace arch, a burnout air supply assembly 5 is also installed on the second furnace arch. In actual installation, the preferred air supply ratio of primary air, secondary air, and gas-fired air is 0.75:0.2:0.05.

[0056] Accordingly, a first heat exchanger 6 is provided at the top of the first furnace chamber, through which a heat exchange medium is circulated, preferably water in the preferred embodiment. Meanwhile, a second heat exchanger 7, a third heat exchanger 9, and a fourth heat exchanger 8 are sequentially provided in the flue gas flow path of the second furnace chamber, each heat exchanger being circulated with a heat exchange medium, preferably water.

[0057] To facilitate the sequential arrangement of heat exchangers in the second furnace chamber, in the preferred embodiment, a partition extending downward from the top is provided in the second furnace chamber. The top of the partition is connected to the top of the second furnace chamber, and the bottom is spaced a certain distance from the bottom of the second furnace chamber. In this way, a "U-shaped" flow path can be formed in the second furnace chamber, which facilitates the settling and discharge of ash and slag in the flue gas.

[0058] More specifically, the second heat exchanger 7 extends vertically and is located at the front end of the flue gas passage in the second furnace chamber, i.e., on the side where the second furnace chamber connects to the first furnace chamber. The vertical arrangement of the second heat exchanger 7 effectively increases its contact time and contact area with the flue gas, thereby improving the heat exchange effect. Correspondingly, multiple third heat exchangers 9 are preferably arranged vertically at intervals, and are also vertically spaced from the fourth heat exchanger 8. Furthermore, the third heat exchangers 9 and the second heat exchangers 7 are located on opposite sides of the partition. This arrangement allows the flue gas entering the second furnace chamber to sequentially contact each heat exchanger and complete the heat exchange process.

[0059] Furthermore, an ash outlet 13 is provided at the bottom of the second furnace chamber, so that the ash in the second furnace chamber can be deposited to the bottom of the second furnace chamber under its own weight and discharged through the ash outlet 13.

[0060] like Figure 1As shown, a third furnace chamber is also provided on one side of the second furnace chamber. One end of the third furnace chamber is connected to the side of the second furnace chamber where the fourth heat exchanger 8 is provided, and the other end is connected to the flue gas outlet 12. Through the economizer 10 and the flue gas cooler 11 arranged at intervals in the third furnace chamber, the heat in the flue gas can be fully absorbed, thereby improving the utilization efficiency of biomass combustion heat.

[0061] In order to better improve the combustion rate of biomass fuel and further suppress the formation of NOx in the furnace, the preferred embodiment further designed the feeding form of the feeding assembly 3 and the structure of the vibrating grate 2.

[0062] Specifically, in the preferred embodiment, the vibrating grate 2 includes multiple grate units arranged sequentially along the width direction. The outermost lateral grate units are connected to the water-cooled wall sidewalls, and the heat released during combustion is carried away by the water-cooled wall, resulting in relatively poor combustion conditions in this area. In contrast, the combustion conditions of the middle grate units located between the lateral and lateral grate units are relatively better. Therefore, in actual installation, it is preferable to refer to the feed inlets located on both sides of the width direction as lateral feed inlets, and the feed inlets between the lateral and lateral feed inlets as middle feed inlets, with the cross-sectional area of ​​the middle feed inlets being larger than that of the lateral and lateral feed inlets.

[0063] By configuring the feed inlet as described above, less material can be distributed in the areas with poor combustion conditions at both ends of the vibrating grate 2 along its width, while more material can be distributed in the area with better combustion conditions in the middle of the vibrating grate 2 along its width. With the total feed amount remaining constant, the non-uniform distribution method can effectively improve the combustion efficiency of biomass fuel on the vibrating grate 2 and increase the burnout rate in each area.

[0064] It is understandable that the aforementioned scheme controls the material feed rate by changing the cross-sectional size of the feed inlet. In actual setup, the cross-sectional size of each feed inlet can also be kept the same, and the feed rate of each feed inlet can be controlled to control the feed rate of different areas. This will not be elaborated here.

[0065] Furthermore, in addition to the different combustion conditions in the width direction, there are also significant regional differences in the length direction of the vibrating grate 2 during actual operation. For example... Figure 2 As shown, from the side closest to the feed inlet, the feeding section of the vibrating grate 2 along its length can be divided into a first combustion section 19, a second combustion section 20, and a third combustion section 21. These three sections mainly correspond to the drying section, pyrolysis and coke oxidation section, and ash burnout section of biomass fuel. The oxygen requirements of the three stages are also different. Therefore, in the preferred embodiment, the size of the primary air passage 14 corresponding to each section of each grate unit has been further designed.

[0066] Specifically, the primary air vent in the second combustion zone 20 has the largest size, the primary air vent in the third combustion zone 21 has the smallest size, and the primary air vent in the first combustion zone 19 has a size between the two.

[0067] by Figure 2 The preferred embodiment shown is described below. The vibrating grate 2 includes four grate units: a first grate unit 15, a second grate unit 16, a third grate unit 17, and a fourth grate unit 18. Taking the first grate unit 15 as an example, the inner diameters of its primary air passages corresponding to the three sections are Φ1, Φ2, and Φ3, respectively, where Φ3 < Φ1 < Φ2. Similarly, the inner diameters of the primary air passages in the second grate unit 16 are related as follows: Φ... 33 <Φ 11 <Φ 22 .

[0068] In the specific design, the primary air passage size of different lateral grate units located in the same section is preferably the same. That is, the primary air passage size of the first grate unit 15 located in the first combustion section 19 is the same as that of the fourth grate unit 18 located in the same section. The same applies to other areas, which will not be elaborated here.

[0069] Furthermore, as the foregoing analysis shows, within the same combustion zone, the combustion conditions of the central grate unit are superior to those of the side grate units. Therefore, in a preferred embodiment, the size of the primary air vent of the central grate unit located within the same combustion zone is larger than the size of the primary air vent of the side grate units, i.e. Figure 2 In the middle, Φ1 < Φ 11 ,Φ2<Φ 22 ,Φ3<Φ 33 .

[0070] By optimizing the design of the primary air vents in each part of each grate unit, oxygen can be distributed on demand. Combined with the control of the feed rate on the feeding assembly 3, fuel can be distributed on demand, thereby ensuring the complete combustion of fuel in each grate unit, avoiding local oxygen-rich areas, and effectively suppressing the formation of NOx in the furnace.

[0071] More preferably, for the same grate unit, the size of the primary air passage in the second combustion zone 20 is 1.3 to 1.8 times the size of the primary air passage in the first combustion zone 19, and more preferably 1.5 times; the size of the primary air passage in the first combustion zone 19 is 1.2 to 1.8 times the size of the primary air passage in the third combustion zone 21.

[0072] Accordingly, for the same combustion zone, the size of the primary air passage in the middle grate unit is preferably 1.2 to 1.5 times that of the primary air passage in the side grate unit.

[0073] The following is a supplementary description of the preferred embodiment through a specific example.

[0074] In this embodiment, the rated evaporation capacity of the water-cooled vibrating grate furnace is 130 t / h, and the rated steam pressure and temperature are 9.2 MPa and 540 °C, respectively. A membrane water-cooled wall is used, and a water-cooled vibrating grate (4 grates, inclination angle 5°) is arranged at the furnace bottom. The two middle sections vibrate simultaneously, while the two side sections vibrate at 180° to the middle sections to maintain balance. A front-wall spiral feeding method is used, with materials fed into the four water-cooled vibrating grates through four independent feed ports, forming a stockbed on the grates. The material undergoes a series of physicochemical changes, mainly in the drying section, pyrolysis and coke oxidation section, and ash burnout section, with the ash and slag finally discharged through the slag discharge port. Primary air is arranged at the bottom of the grate, preheated to 190 °C, and then fed into the furnace through three air chambers to provide oxygen for biomass combustion.

[0075] Four independent feed inlets supply materials with different mass ratios to four water-cooled vibrating grate units. By adjusting the feed rates of the side grate units and the central grate unit from their respective feed inlets, the total feed rate of the boiler (24.96 t / h) is kept consistent. The corresponding feed rates for the four grate units are 3.75 t / h, 8.73 t / h, 8.73 t / h, and 3.75 t / h, respectively. This achieves a reasonable distribution of materials along the width of the furnace without increasing any modification costs, significantly improving the boiler's combustion efficiency.

[0076] Meanwhile, corresponding to the side grate unit and the middle grate unit, such as Figure 2 As shown, the primary air orifice diameter correspondence is Φ1 < Φ 11 ,Φ2<Φ 22 ,Φ3<Φ 33 Specifically, Φ1 = 6mm, Φ2 = 10mm, Φ3 = 4mm; Φ 11 =8mm, Φ 22 =12mm and Φ 33 =5mm. Meanwhile, different air volumes are required for different combustion stages along the grate length, which is achieved through primary air passages that are not uniformly distributed along the grate length, i.e., Φ 33 <Φ 11 <Φ 22 .

[0077] The high-efficiency, low-NOx combustion system for biomass grate furnaces based on primary air passage modification in this invention has a simple structure and is easy to control. By optimizing the size of the primary air passages in the length and width directions of the vibrating grate, and by optimizing the size of the feed inlets and / or the feed rate in different areas of the feeding assembly, high-efficiency, low-NOx combustion of biomass fuel in the grate furnace can be achieved, improving combustion efficiency, reducing the generation of nitrogen oxides, fully utilizing the heat of biomass fuel, reducing the use of fossil energy, saving energy and protecting the environment, and has good practical value and application prospects.

[0078] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements 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 high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification, comprising a first furnace chamber for biomass fuel combustion, wherein a vibrating grate is installed at the bottom of the first furnace chamber, and a feeding assembly, a primary air supply assembly, and a secondary air supply assembly are installed on the chamber body corresponding to the vibrating grate; characterized in that, The feeding assembly is located between the secondary air supply assembly and the vibrating grate, and is used to supply biomass fuel to the vibrating grate; the primary air supply assembly is located at the bottom of the first furnace chamber, and is used to supply air to the bottom of the biomass fuel supported on the vibrating grate through the vibrating grate; the secondary air supply assembly is located above the vibrating grate, and is used to supply air to the top of the biomass fuel. The vibrating grate includes a plurality of grate units arranged sequentially in the width direction. The plurality of grate units include two lateral grate units located on both sides of the width direction and a central grate unit located between the two lateral grate units. The feeding assembly includes a plurality of feeding ports, each feeding port corresponding to one of the grate units. The size of the feeding port corresponding to the lateral grate unit is smaller than the size of the feeding port corresponding to the central grate unit. And / or, the feeding rate in the feeding port corresponding to the lateral grate unit is smaller than the feeding rate in the feeding port corresponding to the central grate unit. Each grate unit is divided into a first combustion zone, a second combustion zone, and a third combustion zone from one end near the feeding assembly to the other end. Each combustion zone has multiple primary air vents. In the same combustion zone, the size of the primary air vent of the central grate unit is larger than that of the lateral grate units. In the same grate unit, the size of the primary air vent in the second combustion zone, the first combustion zone, and the third combustion zone decreases sequentially.

2. The high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification according to claim 1, characterized in that, The central grate unit consists of two units arranged side by side.

3. The high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification according to claim 1 or 2, characterized in that, The primary air vents in each lateral grate unit located in the same combustion zone are of equal size; the primary air vents in each central grate unit located in the same combustion zone are of equal size.

4. The high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification according to claim 3, characterized in that, For the same grate unit, the size of the primary air passage in the second combustion zone is 1.3 to 1.8 times the size of the primary air passage in the first combustion zone; the size of the primary air passage in the first combustion zone is 1.2 to 1.8 times the size of the primary air passage in the third combustion zone.

5. The high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification according to claim 3, characterized in that, For the same combustion zone, the size of the primary air passage in the middle grate unit is 1.2 to 1.5 times that of the primary air passage in the side grate unit.

6. The high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification according to claim 1, 2, 4, or 5, characterized in that, The first furnace chamber is provided with a furnace arch in the middle, which includes a first furnace arch and a second furnace arch connected at the ends and respectively in the shape of a trumpet; The opening of the first furnace arch faces downwards, with the furnace wall facing the vibrating grate, and the secondary air supply assembly is installed on the first furnace arch; the opening of the second furnace arch faces upwards.

7. The high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification according to claim 6, characterized in that, The angle between the inner wall of the first furnace arch and the horizontal section at the bottom of the first furnace arch is 30°~60°; And / or, The angle between the inner wall of the second furnace arch and the cross section at the connection between the two furnace arches is 100°~120°.

8. The high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification according to claim 1, 2, 4, 5, or 7, characterized in that, The angle between each grate unit and the horizontal plane is 4°~10°, and an ash outlet is provided at the bottom of the first furnace chamber at the end of the vibrating grate away from the feeding assembly.

9. The high-efficiency, low-NOx combustion system for a biomass grate furnace based on primary air vent modification according to claim 1, 2, 4, 5, or 7, characterized in that, It also includes a second furnace chamber; Multiple heat exchangers are arranged sequentially along the flue gas transmission path in the second furnace chamber; and at least one heat exchanger is arranged on the top of the first furnace chamber.

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