Double-core hood and double-medium composite fluidized bed
By designing a dual-core wind cap and a dual-medium composite fluidized bed, the problems of increased fan power consumption and uneven co-firing of green ammonia under high load in fluidized bed boilers are solved. Stable distribution of fluidized media and efficient combustion are achieved, reducing energy consumption and increasing the proportion of gas co-firing, thus achieving energy saving and carbon reduction.
Patent Information
- Application Number
- CN202511378921.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-25
- Publication Date
- 2026-01-13
AI Technical Summary
Existing fluidized bed boilers experience increased fan power consumption and significantly increased flow resistance of the fluidizing medium at high loads. Furthermore, when co-firing with green ammonia or other fuels, the fuel gas cannot penetrate the gas-solid two-phase fluid evenly, leading to incomplete combustion and increased chemical heat loss.
It adopts a dual-core wind cap and a dual-medium composite fluidized bed, and independently delivers the mainstream medium and the secondary fluidized medium through an inner and outer coaxial air duct structure. Combined with sealing components and an "n"-shaped flow channel design, it ensures that the media flow independently. Mainstream medium and secondary fluidized medium air chambers are set in the fluidized bed to control the medium flow rate separately, thereby reducing fan energy consumption and improving combustion efficiency.
It reduced fan energy consumption, improved the uniform distribution and combustion efficiency of the fluidized medium, enhanced the operational stability and safety of the fluidized bed, increased the co-firing ratio of green ammonia or other fuels, and achieved the boiler's energy-saving and carbon-reduction goals.
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Figure CN121322940A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of fluidized bed boilers, in particular to a double-core air cap and a double-medium composite fluidized bed. BACKGROUND
[0002] Fluidized bed boilers are widely used in coal-fired boiler fields due to their wide fuel adaptability, wide load regulation, and good environmental friendliness (low-temperature combustion, suitable for in-furnace desulfurization and nitrogen suppression). Current fluidized bed boilers are single fluidized wind chamber structures. Fluidized medium (air) is sent into the wind chamber by a fan, and then is sent into the boiler furnace through the air cap on the air distribution plate. The fluidized material participates in combustion. For fluidized bed boilers, the most important adjustment means for the working state is to adjust the fluidized wind volume. Generally, the fluidized wind volume is reduced at low load and increased at high load. In order to ensure the stability of the fluidized combustion on the bed, the wind pressure of the fluidized wind chamber cannot be too small and must be maintained above a certain value. The air cap is required to have a certain medium flow resistance through the flow passage design to maintain the wind chamber pressure. For the air cap, the medium flow resistance is mainly the friction resistance and the local resistance, both of which are proportional to the square of the medium flow velocity. This leads to a large increase in the flow resistance of the fluidized medium through the air cap at high load compared to low load due to the increase in the flow velocity of the fluidized medium. For example, if the air cap resistance is 3 kPa at 50% of the rated fluidized wind volume, the air cap resistance will increase to 12 kPa at 100% of the rated fluidized wind volume. The power consumption of the fan will increase accordingly, which not only increases the production cost but also increases the construction cost of the fan and the electrical system.
[0003] In addition, the current country vigorously advocates energy saving, carbon reduction, and green development. Coal-fired boilers, as the largest energy consumption and carbon emission equipment in China, naturally become the target of attack. Because the combustion products of ammonia gas are water and nitrogen, without carbon dioxide, and have the advantages of easy storage and transportation, etc., mixed burning of green ammonia has become an important technical means for coal-fired boilers to reduce emissions and carbon reduction. In the "Coal-fired Power Low-carbon Transformation Implementation Plan (2024-2027)", mixed burning of green ammonia has been included as one of the important technical routes for coal-fired power low-carbon transformation. For fluidized bed coal-fired boilers, because the furnace is a high-concentration gas-solid two-phase fluid, when mixed burning of green ammonia or other gas fuels, the gas is injected into the furnace from the side wall of the furnace through the burner or nozzle, and it is difficult to uniformly penetrate the gas-solid two-phase fluid, so only a small amount of mixed burning can be achieved. Otherwise, it will lead to incomplete combustion of the gas, increase of chemical heat loss, local over-temperature of the furnace, coking, and increase of the original emission concentration of nitrogen oxides in the flue gas, etc., which seriously restricts the application and development of the mixed burning of green ammonia technology for fluidized bed boilers.
[0004] In view of the above two problems existing in the fluidized bed boiler, a double-core air cap and a double-medium composite fluidized bed are proposed.
[0005] To address this, we propose a dual-core wind cap and a dual-medium composite fluidized bed. Summary of the Invention
[0006] This invention provides a dual-core windproof cap, comprising:
[0007] The core tube of the fluidized bed is welded from high-temperature resistant stainless steel pipes and plates, employing a coaxial inner and outer duct structure. The inner core duct houses the mainstream fluidized medium flow channel, while the space between the outer and inner core ducts forms the secondary fluidized medium flow channel. The high-temperature resistant stainless steel material ensures the structural stability and corrosion resistance of the core tube under high-temperature conditions. The coaxial inner and outer duct structure allows for the independent transport of the mainstream and secondary fluidized media without interference, guaranteeing the stable operation of the fluidized bed.
[0008] The vent cap is a bell-shaped structure, cast from a heat-resistant and wear-resistant alloy material. The lower circumference is evenly distributed with ventilation holes for both mainstream and secondary fluidizing media. The heat-resistant and wear-resistant alloy material allows the vent cap to withstand the high-speed scouring and high-temperature environment of the materials inside the furnace. The bell-shaped structure and evenly distributed ventilation holes ensure uniform distribution of the fluidizing media, improving the quality of material fluidization.
[0009] The sealing assembly includes a sealing cover and a conical guide plate evenly distributed along the circumference of the outer duct, used to isolate the mainstream fluidizing medium from the secondary fluidizing medium and guide the airflow. The sealing cover and guide plate effectively prevent the premixing of the two fluidizing media, ensuring that the fluidizing medium flows along the set path, avoiding fluid turbulence, and improving the operational stability of the fluidized bed.
[0010] The core tube and outer cover of the air cap are fixed by spot welding. The two fluidizing media channels run independently and in parallel without pre-mixing, both using a bottom-in, bottom-out "n"-shaped flow channel. Spot welding ensures the relative position stability of the core tube and outer cover, preventing misalignment of the air holes. The "n"-shaped flow channel design effectively prevents the fluidizing media from "back-suctioning" fine materials in the furnace, avoiding air cap blockage and improving the operational reliability of the fluidized bed.
[0011] In other embodiments, a positioning plate is vertically welded between the inlet end of the outer duct and the inner core duct to improve the structural rigidity of the core duct and ensure coaxiality. The positioning plate can effectively limit the relative displacement between the outer duct and the inner core duct, ensure the uniformity of the secondary fluidizing medium flow channel, improve the distribution effect of the fluidizing medium, and thus improve the fluidization quality of the material.
[0012] In other embodiments, the upper end of the sealing cover corresponds to the air outlet of the outer duct, and the lower end opening corresponds to the ventilation hole of the secondary fluidized medium on the outer cover of the hood, ensuring the isolation of the two fluidized media. This correspondence ensures that the secondary fluidized medium can accurately enter the corresponding ventilation hole of the outer cover of the hood, avoiding premixing with the mainstream fluidized medium and ensuring the safe and effective delivery and utilization of the fluidized medium.
[0013] In other embodiments, the outer cover of the wind cap and the annular support plate of the wind cap core tube are fixed by spot welding to prevent the outer cover of the wind cap from rotating, ensure that the corresponding air holes are always aligned, avoid premixing of the fluidizing medium, maintain smooth flow of the medium, ensure the stability of material fluidization, and improve the reliability of the entire fluidized bed system.
[0014] Another aspect of the present invention provides a dual-medium composite fluidized bed, which includes the aforementioned dual-core wind cap, and further includes:
[0015] The mainstream medium air chamber is formed by extending and bending the membrane water-cooled wall of the boiler rear wall. It is closed on both sides by the boiler side wall water-cooled walls and lined with refractory and heat-insulating materials inside. It is used for the flow equalization and pressure stabilization of the mainstream medium.
[0016] Refractory insulation materials reduce heat loss, maintain the high temperature of the mainstream medium, ensure the smooth progress of the ignition process, and protect the membrane water-cooled wall.
[0017] The secondary fluidizing medium air chamber is located directly above the main fluidizing medium air chamber. It is a rectangular cross-section air chamber formed by a three-way tube structure through the membrane water-cooled wall of the boiler rear wall. The two sides are closed by the boiler side wall water-cooled walls, and the interior is a bare tube structure. It is used for flow equalization and pressure stabilization of the secondary fluidizing medium.
[0018] The secondary fluidizing medium air chamber, with a rectangular cross-section formed by a three-pronged tube structure, forms an integrated structure with the main fluidizing medium air chamber. The internal working fluid (boiler water) flow is clearly defined, and hydrodynamic safety is reliably guaranteed. The bare tube structure facilitates the preheating of the secondary fluidizing medium by the working fluid inside the tube, which can effectively improve combustion efficiency and also facilitates inspection and maintenance of the air chamber.
[0019] The ignition device is located at the rear end of the mainstream medium air chamber and ignites the material in the furnace by heating the mainstream medium.
[0020] The heating medium can quickly ignite the materials in the furnace and start the boiler's combustion process.
[0021] The dual-core air cap is arranged on the air distribution plate above the secondary fluidized medium air chamber. The inner core air duct is connected to the main fluidized medium air chamber, and the outer air duct is connected to the secondary fluidized medium air chamber.
[0022] This structure ensures that the two fluidizing media can smoothly enter the double-core wind cap from the two wind chambers respectively, and be evenly distributed into the furnace to achieve material fluidization and combustion.
[0023] In other embodiments, the fluidizing medium inlets of the mainstream fluidizing medium air chamber and the secondary fluidizing medium air chamber are located on the left and right sides or the rear side of the boiler, with channels provided by membrane water-cooled wall bends and allowances. This design is beneficial for the overall layout of the boiler unit, allowing for the selection of appropriate inlet positions based on actual site conditions, avoiding interference with other equipment, and ensuring the structural integrity and safety of the boiler.
[0024] In other embodiments, the main fluidizing medium air chamber and the secondary fluidizing medium air chamber are an integral structure, formed by extending the boiler membrane water-cooled wall, with the internal working fluid (boiler water) interconnected. This integral structure enhances the structural integrity and stability of the air chambers, saves floor space, and improves the reliability of the entire fluidized bed system.
[0025] In other embodiments, for conventional solid fuel fluidized bed boilers, the fluidizing medium introduced into the mainstream fluidizing medium air chamber and the secondary fluidizing medium air chamber is air. Both are independently fed into the furnace through a double-core air cap. By changing the ratio of the mainstream fluidizing medium and the secondary fluidizing medium according to the boiler load adjustment needs, the power consumption of the blower can be controlled while ensuring efficient fuel combustion, thus achieving the goal of energy saving.
[0026] In other embodiments, for fluidized bed boilers that co-fire ammonia or other fuel gases, the secondary fluidizing medium air chamber is supplied with fuel gas, and the mainstream fluidizing medium air chamber is supplied with air. Both are independently fed into the furnace through a double-core air cap, realizing independent delivery of fuel gas and air and uniform mixing in the furnace, which improves the combustion efficiency and safety of the fuel and significantly increases the co-firing ratio of ammonia or other fuel gases.
[0027] In other embodiments, the ignition device is an ignition burner that ignites the material in the furnace by heating the mainstream medium (air) during the boiler start-up phase.
[0028] In other embodiments, when the fluidized bed boiler co-fires green ammonia or other fuel gases, the secondary fluidized medium air chamber must be purged with nitrogen before the fuel gas is introduced or after the fuel gas supply is stopped. This eliminates the safety hazard of deflagration in the secondary fluidized medium air chamber and ensures the safety and reliability of the boiler start-up and shutdown processes. Attached Figure Description
[0029] Figure 1 This is a schematic diagram of the structure of the present invention.
[0030] Figure 2 for Figure 1 A magnified view of part I and the corresponding sectional view along direction A.
[0031] Figure 3 for Figure 2 A magnified view of a section II.
[0032] Figure 4 forFigure 3 Sectional views along lines B and C.
[0033] Figure 5 for Figure 4 A sectional view along the D direction.
[0034] Among them: 10. Mainstream fluidized medium air chamber; 11. Refractory insulation material; 20. Secondary fluidized medium air chamber; 30. Double-core air cap; 31. Air cap core tube; 311. Inner core air duct; 312. Outer air duct; 313. Sealing cover; 314. Guide plate; 315. Annular support plate; 316. Positioning plate; 32. Air cap outer cover; 321. Mainstream fluidized medium ventilation hole; 322. Secondary fluidized medium ventilation hole; 40. Rear wall membrane water-cooled wall; 50. Side wall membrane water-cooled wall; 60. Ignition burner; 70. Furnace chamber. Detailed Implementation
[0035] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.
[0036] Example 1
[0037] like Figures 3-5 As shown, this embodiment discloses a dual-core wind cap 30, including a wind cap core tube 31, a wind cap outer cover 32, and a sealing assembly (including a sealing cover 313 and a guide plate 314).
[0038] Specifically, in this embodiment, the double-core wind cap 30 consists of a wind cap core tube 31 and a wind cap outer cover 32. During assembly, after aligning the inner and outer air holes of both, the lower edge of the wind cap outer cover 32 needs to be spot-welded to the annular support plate 315 of the wind cap core tube 31 to prevent the wind cap outer cover 32 from rotating and affecting the air outlet of the wind cap core tube 31. During the operation of the fluidized bed, the inside and outside of the wind cap will be impacted by the two-phase flow of the fluidizing medium and fluidized material. If the wind cap outer cover 32 rotates, it will cause the inner and outer air holes to misalign, changing the flow channel of the fluidizing medium and affecting the distribution and flow characteristics of the fluidizing medium. This will not only reduce the fluidization effect, but may also lead to uneven fluidization of local materials, or even dead zones, affecting the combustion efficiency and combustion stability of the boiler. By spot-welding, the relative position of the wind cap outer cover 32 and the wind cap core tube 31 can be fixed, ensuring that the air holes are always aligned, thereby maintaining good fluidization performance and improving the reliability of the entire fluidized bed system.
[0039] In this embodiment, the core tube 31 of the double-core air cap 30 adopts an inner and outer coaxial air duct structure, which is welded from high-temperature resistant stainless steel pipe and steel plate. During the operation of the fluidized bed boiler, the air cap core tube 31 will come into contact with the high-temperature fluidizing medium and the high-temperature environment inside the furnace. The high-temperature resistant stainless steel can maintain good mechanical properties at high temperatures and will not experience significant strength reduction or deformation due to temperature rise, thus ensuring the structural stability of the air cap core tube 31.
[0040] The inner core duct 311 and the outer duct 312 are respectively connected to the mainstream fluidized medium chamber 10 and the secondary fluidized medium chamber 20. The inner core duct 311 is the mainstream fluidized medium flow channel, and the outer duct 312 and the inner core duct 311 are the secondary fluidized medium flow channel.
[0041] For conventional solid fuel fluidized bed boilers, air is introduced only into the main fluidized medium air chamber at low loads, and simultaneously into both the main and secondary fluidized medium air chambers at high loads. By controlling the flow rates of the main and secondary fluidized media separately under varying boiler load conditions, the variation in wind velocity within a single flow channel of the double-core wind cap 30 can be effectively reduced. This significantly reduces the corresponding flow resistance at high loads, ensuring the relative stability of the fan's air supply pressure, reducing fan energy consumption, and allowing for a smaller fan size, thus saving construction costs. For fluidized bed boilers co-firing with ammonia or other fuels, air and fuel are introduced into the furnace through the main and secondary fluidized medium flow channels respectively. This allows for independent control of air and fuel, improving the uniformity and timeliness of their mixing with materials, ensuring efficient and safe combustion, and significantly increasing the co-firing ratio of ammonia or other fuels, thereby achieving the goal of reducing carbon emissions from the boiler.
[0042] At the inlet end of the outer duct 312, a positioning plate 316 is vertically welded between it and the inner core duct 311. This improves the rigidity of the duct core 31 structure, ensures the concentricity of the outer duct 312 and the inner core duct 311, and achieves uniformity in the flow path of the secondary fluidized medium. During fluidized bed operation, the duct core 31 is subjected to various forces, such as the impact force of the fluidized medium and thermal stress caused by high temperature. These forces may cause relative displacement between the outer duct 312 and the inner core duct 311, disrupting concentricity. The vertical welding of the positioning plate 316 effectively limits this relative displacement, ensuring that the outer duct 312 and the inner core duct 311 always maintain good concentricity. This results in more uniform flow of the secondary fluidized medium within the flow path, avoiding turbulence and blockage caused by uneven flow path, improving the uniformity of fluidized medium distribution, and thus enhancing the overall fluidization quality of the fluidized bed.
[0043] In this embodiment, the sealing cover 313 is evenly distributed around the circumference of the outer duct 312 and is made of high-temperature resistant stainless steel plate. It can adapt to the high-temperature environment inside the fluidized bed, ensuring that the sealing cover 313 will not be damaged at high temperatures and maintaining its sealing performance. The lower end plate of the sealing cover 313 is composed of a guide plate 314 welded to the outer duct 312. The guide plate 314 is conical and inclined downwards, guiding the secondary fluidizing medium inside the sealing cover 313 and the mainstream fluidizing medium outside the sealing cover 313, preventing fine materials from depositing inside the double-core air cap 30. During the flow of the fluidizing medium, the guide plate 314 can guide the flow direction of the secondary fluidizing medium and the mainstream fluidizing medium, making them flow along a predetermined path and reducing flow resistance. Fine materials may enter the air cap during the fluidization process due to the "breathing" effect caused by pressure fluctuations in the fluidizing medium. The presence of the guide plate 314 can effectively prevent the deposition of fine materials, making them easier to be carried out of the air cap by the fluidizing medium, maintaining the cleanliness inside the air cap and the smooth flow of the fluidizing medium channel, ensuring that the normal operation of the air cap is not affected.
[0044] The upper end of the sealing cover 313 corresponds to the air outlet of the outer duct 312, and the lower opening corresponds to the secondary fluidizing medium ventilation hole 322 of the outer cover 32, ensuring that the two fluidizing media are isolated from each other and do not premix within the core tube 31 of the air cap. This correspondence ensures that the secondary fluidizing medium can accurately flow out from the air outlet of the outer duct 312 and enter the secondary fluidizing medium ventilation hole 322 of the outer cover 32 through the lower opening of the sealing cover 313, while avoiding premixing with the mainstream fluidizing medium. If the mainstream and secondary fluidizing media have different properties, premixing them will alter their properties, affecting not only material fluidization and combustion but also posing safety hazards. For example, when co-firing with ammonia or other fuel gases, if the fuel gas and air are premixed within the outer cover 32, unnecessary chemical reactions may occur before entering the furnace, potentially leading to deflagration.
[0045] In this embodiment, the outer cover 32 of the dual-core wind cap 30 is a bell-shaped structure, cast from a heat-resistant and wear-resistant alloy material. The fluidized material within the fluidized bed will exert strong scouring and abrasion on the outer cover 32, and the high-temperature environment also places high demands on the material's performance. The heat-resistant and wear-resistant alloy material can maintain high hardness and wear resistance at high temperatures, effectively resisting material wear and extending the service life of the outer cover 32.
[0046] Meanwhile, the lower circumference of the outer cover 32 of the vent cap is evenly distributed with mainstream fluidizing medium ventilation holes 321 and secondary fluidizing medium ventilation holes 322. During assembly, these holes correspond to the mainstream fluidizing medium outlet holes and secondary fluidizing medium outlet holes on the vent cap core tube 31, respectively. This ensures that the fluidizing medium can smoothly enter the vent cap outer cover 32 from the vent cap core tube 31 and be discharged through the corresponding ventilation holes. If the ventilation holes do not correspond, it will cause the mainstream and secondary fluidizing media to be premixed prematurely, affecting operational safety and increasing the resistance of the fluidizing medium through the vent cap, thus affecting the material fluidization effect of the entire fluidized bed.
[0047] The two fluidizing media channels within the double-core air cap 30 are independent and parallel, isolated from each other. Both enter from below the air cap core tube 31, flow out through their respective air distribution holes at the top of the core tube 31, and then turn downwards into a downward flow channel before exiting through ventilation holes 321 / 322 below the air cap outer cover 32. Both fluidizing media within the double-core air cap 30 utilize a bottom-in, bottom-out "n"-shaped flow channel. This channel design effectively prevents the fluidizing media from "back-suctioning" fine materials from the furnace. During fluidized bed operation, fine materials in the furnace may be sucked into the air cap due to pressure fluctuations. The "n"-shaped flow channel's turning design, by changing the flow direction of the fluidizing media, increases the counter-current resistance, preventing the fine materials from being sucked in. Even if some are sucked in, gravity will prevent them from flowing upwards back into the air ducts 311 / 312, and they will be blown out of the double-core air cap 30 by the fluidizing media. Furthermore, the "n"-shaped flow channel allows the fluidizing media to flow fully within the air cap, ensuring sufficient contact time between the fluidizing media and the air cap, which is beneficial for the uniform distribution and stable flow of the fluidizing media. Furthermore, this flow channel design can reduce dead zones in the fluidizing medium within the air cap, preventing localized excessively low or high fluidizing medium velocities and improving the overall fluidization quality of the fluidized bed. This air cap structure can effectively prevent the fluidizing medium from "back-suctioning" fine materials from the furnace.
[0048] Example 2
[0049] like Figures 1-5 As shown, this embodiment discloses a dual-medium composite fluidized bed, which includes a dual-core air cap 30 as in Embodiment 1, and also includes a mainstream fluidized medium air chamber 10, a secondary fluidized medium air chamber 20, and a plurality of dual-core air caps 30 arranged on the two air chambers 10 / 20.
[0050] For conventional fuel fluidized bed boilers, a composite dual-chamber fluidized bed is used to divide the material fluidizing air (air) into two streams. These streams are supplied to the two fluidizing chambers by fans, and then fed into the furnace 70 through dual-core air caps 30 connected to each chamber to fluidize the material and participate in combustion. The two fluidizing air streams flow in closed parallel channels with independent flow rate control. This effectively reduces the variation in air velocity within a single flow channel during boiler load adjustments, ensuring the relative stability of the fan's air supply pressure, thereby reducing fan energy consumption and saving construction costs. (In conventional fluidized bed boilers, the boiler load...) Changes in load will cause changes in the demand for fluidizing air volume. If there is only a single air chamber and duct, an increase in load requires an increase in fluidizing air volume, which will increase the air velocity within the duct. Since the flow resistance of a fluid is proportional to the square of its velocity, the fan resistance will increase significantly, leading to a substantial increase in fan energy consumption. However, with a composite dual-air chamber structure, the fluidizing air is divided into two streams, controlled by the main fluidizing medium air chamber 10 and the secondary fluidizing medium air chamber 20, respectively. At low loads, only the main fluidizing medium air chamber 10 is open, while the secondary fluidizing medium air chamber 20... Chamber 20 is basically closed. Under high load, the main fluidizing medium chamber 10 and the secondary fluidizing medium chamber 20 are opened simultaneously. By controlling and adjusting the flow rates of the two fluidizing air streams, the air velocity variation in each flow channel is relatively small, thereby ensuring relatively stable fan supply pressure and reducing fan energy consumption. Because it is not necessary to equip excessively powerful fans to meet the air pressure requirements under high load, construction costs can also be reduced. For fluidized bed boilers that co-fire green ammonia or other fuel gases, by setting up a composite dual-chamber structure, the main fluidizing air stream (…) Air and fuel gas are supplied to two fluidizing air chambers respectively, and then sent into the furnace 70 through the double-core air caps 30 connected to them to fluidize the material and participate in combustion. The air and fuel gas channels are closed and run in parallel, and the flow rates are independently controlled. The fuel gas, as the secondary fluidizing air, enters the furnace 70 directly from the bottom of the boiler fluidized bed together with the air, which is the main fluidizing air. This can greatly improve the uniformity and timeliness of the mixing of fuel gas with materials and air, ensure the high efficiency and safety of fuel gas combustion, and thus greatly increase the proportion of green ammonia or other fuel gas co-firing, achieving the goal of reducing carbon emissions in the boiler.
[0051] In fluidized bed boilers that co-fire ammonia or other fuel gases, the traditional method of injecting ammonia into the furnace sidewall presents several problems. Because the furnace contains a high-concentration gas-solid two-phase fluid, the injected fuel gas cannot penetrate uniformly, leading to a highly uneven fuel gas concentration field within the furnace. Excessively high local concentrations result in incomplete combustion, causing chemical heat loss, and can also lead to localized furnace overheating and coking. However, by employing a composite dual-chamber structure, the fuel gas is used as a secondary fluidizing air, which, along with the main fluidizing air (air), is directly introduced into the furnace 70 from the bottom of the boiler fluidized bed through a double-core air cap 30. This method ensures uniform distribution of fuel gas and air upon entering the furnace 70, facilitating thorough mixing of air, fuel gas, and materials during fluidization. This guarantees a balanced concentration and temperature field within the furnace cross-section, improving the timeliness and efficiency of fuel combustion. At the same time, the independent control of air and gas flow can adjust the combustion state according to the actual situation, ensuring the high efficiency and safety of gas combustion, thereby significantly increasing the blending ratio of green ammonia or other gases, reducing coal consumption, and achieving the goal of reducing carbon emissions in boilers.
[0052] Specifically, such as Figure 1 As shown, in this embodiment, the secondary fluidizing medium air chamber 20 is located at the bottom of the boiler furnace 70 and is a rectangular cross-section air chamber formed by the boiler rear wall membrane water-cooled wall 40 through a three-way pipe structure. The three-way pipe structure allows the boiler rear wall membrane water-cooled wall 40 to form a suitable space at a specific location to arrange the secondary fluidizing medium air chamber 20. The rectangular structure can better cooperate with the surrounding boiler structure, facilitate installation and maintenance, and at the same time provide a larger air chamber volume to meet the pressure stabilization and distribution requirements of the secondary fluidizing medium.
[0053] The main fluidized medium air chamber 10 is located directly below the secondary fluidized medium air chamber 20, and is formed by extending and bending the boiler rear wall membrane water-cooled wall 40 that constitutes the secondary fluidized medium air chamber 20. This layout helps ensure the airtightness of the secondary fluidized medium air chamber, reduces the risk of gas leakage, and facilitates the placement of the ignition burner 60 at the rear end of the main fluidized medium air chamber 10. Simultaneously, being formed by extending and bending the same boiler rear wall membrane water-cooled wall 40 ensures the structural integrity and stability of the two air chambers, saving structural space and improving the reliability of the entire fluidized bed system. Both sides of the main fluidized medium air chamber 10 and the secondary fluidized medium air chamber 20 are sealed by the downward extension of the boiler side wall membrane water-cooled wall 50. The downward extension of the boiler side wall membrane water-cooled wall 50 to seal the sides of the air chambers ensures their airtightness and prevents fluidized medium leakage. At the same time, this sealing method integrates with the overall boiler structure, enhancing the boiler's structural strength, enabling the air chambers to withstand the pressure of the fluidized medium, and ensuring the reliability of the overall fluidized bed structure.
[0054] The rear wall membrane water-cooled wall 40 on the upper surface of the secondary fluidized medium air chamber 20 forms the boiler fluidized bed air distribution plate. Several double-core air caps 30 are arranged on it, with the air cap core tube 31 inserted into the two fluidized medium air chambers 10 / 20 below. The fluidized medium pressure in the air chambers 10 / 20 forces the fluidized medium through the double-core air caps 30 into the boiler furnace 70, fluidizing the material and enabling combustion. The air distribution plate formed by the rear wall membrane water-cooled wall 40 has good thermal conductivity and structural strength, enabling it to adapt to the high-temperature environment inside the furnace while ensuring its own stability. Wear-resistant castable is applied to the upper surface of the air distribution plate, effectively protecting the rear wall membrane water-cooled wall 40 from material erosion and wear, and preventing the horizontal tubes from overheating and failing due to the high-intensity heat load inside the furnace.
[0055] like Figure 1 As shown, in this embodiment, the fluidizing medium inlets of the main fluidizing medium air chamber 10 and the secondary fluidizing medium air chamber 20 can be located on the left and right sides or the rear side of the boiler, respectively, according to the overall layout requirements of the boiler unit. The fluidizing medium channels are created by using bends and relief pipes at the rear wall membrane water-cooled wall 40 and the side wall membrane water-cooled wall 50, which is beneficial to the overall layout of the boiler unit. In actual boiler installation and use, since other equipment and pipelines may exist around the boiler, placing the fluidizing medium inlets on the left and right sides or the rear side of the boiler allows for the selection of the most suitable location based on the actual site conditions, avoiding interference with other equipment. The use of bends and relief pipes at the rear wall membrane water-cooled wall 40 and the side wall membrane water-cooled wall 50 to create fluidizing medium channels ensures smooth delivery of the fluidizing medium without adversely affecting the overall structure of the boiler, thus guaranteeing the structural integrity and safety of the boiler.
[0056] The ignition burner 60 is located behind the mainstream medium air chamber 10. Boiler ignition begins in the mainstream medium air chamber, heating the mainstream medium (air) to ignite the material inside the boiler furnace 70. The ignition burner 60 is positioned behind the mainstream medium air chamber 10 because the mainstream medium air chamber 10 is the pressure stabilization and distribution area for the mainstream medium. Heating the mainstream medium allows for direct and rapid heat transfer to the furnace 70 using its flow characteristics. During ignition, heating the mainstream medium (air) increases the air temperature. When the high-temperature air enters the furnace 70, it rapidly heats the material inside, bringing it to its ignition point and igniting the material, thus initiating the boiler's combustion process.
[0057] The inner side of the rear wall membrane water-cooled wall 40 and the side wall membrane water-cooled wall 50 of the mainstream fluidized medium air chamber 10 is covered with refractory insulation material 11. During boiler ignition, this material maintains the high temperature of the fluidized medium within the air chamber 10, preventing heat loss, and also protects the rear wall membrane water-cooled wall 40 and the side wall membrane water-cooled wall 50 from overheating. During boiler ignition, a high temperature is required to ignite the materials. The refractory insulation material 11 effectively reduces heat loss within the air chamber 10, maintaining the high temperature of the fluidized medium and ensuring a smooth ignition process. Simultaneously, it protects the rear wall membrane water-cooled wall 40 and the side wall membrane water-cooled wall 50 from direct exposure to high temperatures, preventing deformation and damage due to excessive heat, and extending their service life.
[0058] The inner sides of the rear membrane water-cooled wall 40 and side membrane water-cooled wall 50 of the secondary fluidized medium air chamber 20 are bare tube structures, and no refractory insulation material is laid inside the air chamber 20. In this embodiment, the secondary fluidized medium air chamber 20 adopts a bare tube structure and is not covered with refractory insulation material because the temperature inside the secondary fluidized medium air chamber 20 is relatively lower than that of the mainstream fluidized medium air chamber 10, and no additional insulation measures are needed to maintain the temperature. At the same time, the bare tube structure facilitates the preheating of the secondary fluidized medium by the working fluid inside the tube, which can effectively improve combustion efficiency and also facilitates inspection and maintenance of the air chamber interior.
[0059] For conventional fuel fluidized bed boilers, this invention can significantly reduce fan energy consumption during boiler operation. For example, when the wind cap resistance is designed to be 3 kPa at 50% of the rated fluidized air volume, at 100% of the rated air volume, the wind velocity in a conventional boiler wind cap, due to its single air duct, will double, and the flow resistance will reach 12 kPa. However, for the dual-medium composite fluidized bed boiler using this invention, only the main fluidized medium air chamber 10 is opened at 50% of the rated fluidized air volume, while at 100% of the rated fluidized air volume, both the main fluidized medium air chamber 10 and the secondary fluidized medium air chamber 20 are opened simultaneously. The wind velocity in the flow channel of the dual-core wind cap 30 is the same as at 50% of the rated fluidized air volume, and the resistance remains at 3 kPa. The comparison shows that, in overcoming wind cap resistance, the fan energy saving can reach 75%. For fluidized bed boilers that use green ammonia or other fuels for carbon reduction, the fuels can be mixed and burned in a timely and sufficient manner with air and materials in the furnace. The uniformity of the material concentration field and temperature field in the cross-section of the furnace is reliably guaranteed. The proportion of fuels co-fired (heat ratio) can be increased from less than 10% to more than 50%, and the carbon reduction effect is significantly improved. This makes the technical prospects for carbon reduction retrofitting of coal-fired boilers by using green ammonia or other fuels very promising, which is of great significance to my country's timely achievement of the "dual carbon" target.
[0060] In addition, the present invention also has the following advantages:
[0061] 1. Compared with using independent air caps for two fluidizing air chambers, the use of a sleeve-type double-core air cap makes the boiler air distribution more uniform and the material fluidization more complete. This can effectively avoid the problem of coking caused by poor material fluidization, which affects safe operation.
[0062] 2. The main and secondary fluidizing medium channels inside the double-core air cap both adopt an anti-backflow structure, which can effectively prevent material backflow and blockage of the air cap, ensuring the reliability of boiler operation.
[0063] 3. For fluidized bed boilers that co-fire green ammonia or other fuel gases, a composite fluidized bed structure with two independent air chambers can be adopted to avoid the risk of deflagration caused by pre-mixing of fuel gas and air, thus ensuring the safety of boiler operation.
[0064] 4. The two fluidizing chambers of the composite fluidized bed are both formed by the extension of the boiler membrane water-cooled wall, forming a whole. The structure is simple, which is not only easy to manufacture, but also easy to carry out technical transformation of conventional single-chamber fluidized bed boilers.
[0065] 5. For conventional fuel fluidized bed boilers, the fluidizing medium in both fluidized air chambers is air, and the pressure in the air chambers is basically the same. They can share one blower for air supply, and the air volume of the two streams can be adjusted through the air duct valves. The system is simple and saves construction costs.
[0066] 6. This invention is fully applicable to the renovation or new construction projects of fluidized bed boilers that co-fire other combustible gases, and can significantly increase the proportion of co-fired gas.
[0067] In this embodiment, the specific working process mainly includes the following steps:
[0068] (1) The fluidizing medium in the mainstream fluidizing medium air chamber 10 is always the combustion air required for boiler combustion. When the boiler starts, the air entering the mainstream fluidizing medium air chamber 10 is first heated by the ignition burner 60. The high-temperature air, as the mainstream fluidizing medium, enters the double-core air cap 30 through the inner core air duct 311 and is then sent into the furnace 70 to heat and fluidize the material in the furnace and gradually raise the temperature of the material until the material is ignited.
[0069] (2) For fluidized bed boilers using conventional fuels, the secondary fluidizing medium is also combustion air. Whether the boiler is ignited and started up or enters the normal operation stage, the secondary fluidizing medium air chamber 20 needs to be properly ventilated and kept at an appropriate pressure (slightly higher than the pressure at the bottom of the furnace) to prevent the double-core air cap 30 from being blocked by ash.
[0070] (3) For fluidized bed boilers that co-fire green ammonia or other gas, the secondary fluidizing medium is ammonia or other gas. During the boiler ignition and start-up stage or when the boiler is not co-fired with gaseous fuel, the secondary fluidizing medium air chamber 20 needs to be properly purged with nitrogen (or other inert gas) and kept at an appropriate pressure (slightly higher than the pressure at the bottom of the furnace) to prevent the double-core air cap 30 from being blocked by ash.
[0071] (4) For fluidized bed boilers using conventional fuels, when the fluidizing air volume required for boiler combustion is no more than 50% of the rated fluidizing air volume, the fluidizing medium (air) can be supplied to the furnace 70 through the main fluidizing medium air chamber 10 to meet the needs of material fluidization and combustion. When the fluidizing air volume required for boiler combustion is more than 50% of the rated fluidizing air volume, the air supply systems of the main fluidizing medium air chamber 10 and the secondary fluidizing medium air chamber 20 need to be opened simultaneously, and the pressure of the two air chambers 10 / 20 needs to be adjusted to a balanced state. The air required for material combustion and fluidization is supplied to the furnace 70 through the double-core air cap 30.
[0072] (5) For fluidized bed boilers that co-fire ammonia or other fuel gases, once the boiler has been successfully started up and the furnace temperature has stabilized above 800℃ while burning solid fuel, the gas supply system can be turned on. The co-fired gaseous fuel is supplied to the furnace 70 through the secondary fluidizing medium air chamber 20 and the double-core air cap 30. The gas and the mainstream medium (air) fed into the furnace 70 through the mainstream fluidizing medium air chamber 10 and the double-core air cap 30 fluidize the material and perform combustion and heat release. The amount of gas supplied to the secondary fluidizing medium air chamber 20 must be increased or decreased slowly. When the amount of gas increases, the air supply to the boiler combustion should be increased first. When the amount of gas decreases, the air supply to the boiler combustion should be decreased later. The boiler operation should be adjusted and controlled according to the relevant data of the flue gas analyzer and the boiler parameters.
[0073] (6) For fluidized bed boilers using conventional fuels, when the boiler is shut down, the air supply to the two fluidized medium air chambers 10 / 20 is stopped simultaneously. Other operating procedures are exactly the same as those for current single-chamber fluidized bed boilers.
[0074] (7) For fluidized bed boilers that co-fire ammonia or other fuel gases, when shutting down the boiler, the fuel gas supply to the secondary fluidized medium air chamber 20 must be stopped first. The specific procedure is as follows: open the nitrogen replacement switch valve on the gas supply pipeline of the secondary fluidized medium air chamber 20, and at the same time shut off the fuel gas supply; after the ammonia or other fuel gas in the secondary fluidized medium air chamber 20 has been completely replaced by nitrogen, stop the air supply and nitrogen supply to both fluidized medium air chambers 10 / 20 simultaneously. Other operating procedures are exactly the same as those for current single-chamber fluidized bed boilers.
[0075] In summary, this invention provides a dual-core air cap and a dual-medium composite fluidized bed. Through the dual-medium fluidizing air chamber and dual-medium flow channel air cap structure, conventional fuel fluidized bed boilers can achieve staged air supply of the fluidizing medium according to load requirements, significantly reducing the energy consumption of the boiler's blowers. For fluidized bed boilers co-firing with ammonia or other fuel gases, it can leverage the fluidizing medium effect of the fuel gas, greatly increasing the co-firing ratio. This invention provides a new avenue for the innovative development of fluidized bed boiler technology and is of great significance for energy conservation and carbon reduction in the boiler industry.
[0076] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.
Claims
1. A double-core windproof cap, characterized in that, include: The hood core tube is made of high-temperature resistant stainless steel pipe and steel plate welded together. It adopts an inner and outer coaxial duct structure. The inner core duct is the mainstream medium flow channel, and the outer duct and the inner core duct are the secondary fluidized medium flow channel. The windproof hood has a bell-shaped structure and is made of heat-resistant and wear-resistant alloy material. The lower circumference is evenly distributed with mainstream medium ventilation holes and secondary medium ventilation holes. The sealing assembly includes a sealing cover and a conical guide plate evenly distributed along the circumference of the outer duct. The wind cap core tube and the wind cap outer cover are fixed by spot welding. The two fluidizing medium channels are independent and parallel and do not premix with each other. Both adopt an "n" shaped flow channel with bottom inlet and bottom outlet.
2. A dual-core windproof cap according to claim 1, characterized in that, A positioning plate is vertically welded between the inlet end of the outer duct and the inner core duct.
3. A dual-core windproof cap according to claim 1, characterized in that, The upper end of the sealing cover corresponds to the air outlet of the outer duct, and the lower end opening corresponds to the secondary fluidized medium ventilation hole of the outer cover of the hood, ensuring that the two media are isolated.
4. A dual-core windproof cap according to claim 1, characterized in that, The outer cover of the wind cap and the annular support plate of the wind cap core tube are fixed by spot welding.
5. A dual-media composite fluidized bed, characterized in that, It includes a dual-core windproof cap as described in any one of claims 1-4, and further includes: The mainstream medium air chamber is formed by extending and bending the membrane water-cooled wall of the boiler rear wall, and is closed on both sides by the boiler side wall water-cooled wall, with refractory and heat-insulating materials laid inside. The secondary fluidized medium air chamber is located directly above the main fluidized medium air chamber. It is a rectangular cross-section air chamber formed by the boiler rear wall membrane water-cooled wall through a three-way tube structure. The two sides are closed by the boiler side wall water-cooled walls, and the interior is a bare tube structure. The ignition device, namely the ignition burner, is located at the rear end of the mainstream medium air chamber and ignites the material in the furnace by heating the mainstream medium. The dual-core air cap is arranged on the air distribution plate above the secondary fluidized medium air chamber. The inner core air duct is connected to the main fluidized medium air chamber, and the outer air duct is connected to the secondary fluidized medium air chamber.
6. A dual-media composite fluidized bed according to claim 5, characterized in that, The fluidizing medium inlets of the main fluidizing medium air chamber and the secondary fluidizing medium air chamber are located on the left and right sides or the rear side of the boiler, and are provided through the membrane water-cooled wall bends and the allowance pipes.
7. A dual-media composite fluidized bed according to claim 5, characterized in that, The main fluidized medium air chamber and the secondary fluidized medium air chamber are an integrated structure, which is formed by the extension of the membrane water-cooled wall of the boiler rear wall, and the internal working medium (boiler water) is interconnected.
8. A dual-media composite fluidized bed according to claim 5, characterized in that, For conventional solid fuel fluidized bed boilers, the fluidizing medium introduced into both the main fluidizing medium air chamber and the secondary fluidizing medium air chamber is air.
9. A dual-media composite fluidized bed according to claim 8, characterized in that, For fluidized bed boilers that co-fire ammonia or other fuel gases, air is introduced into the main fluidizing medium air chamber, and ammonia or other fuel gases are introduced into the secondary fluidizing medium air chamber.
10. A dual-media composite fluidized bed according to claim 5, characterized in that, When the fluidized bed boiler is co-fired with green ammonia or other fuel gas, the secondary fluidized medium air chamber must be purged with nitrogen before the fuel gas is introduced or after the fuel gas supply is stopped.