Center cylinder device with adjustable separation efficiency for circulating fluidized bed boiler

Abstract

The invention discloses a central cylinder device with adjustable separation efficiency for a circulating fluidized bed boiler, which comprises an annular support ring beam connected to a boiler body steel frame, a cyclone separator and a central cylinder, the central cylinder is arranged at the top end of the separator, the lower end of the central cylinder is inserted into a straight cylinder section of the separator, and a flue gas outlet is formed in the top of the central cylinder. A mounting plate protruding outwards in the radial direction of the center cylinder is arranged at the upper end of the center cylinder, the mounting plate is in lap joint with the annular supporting ring beam to suspend the center cylinder in the cyclone separator, and a positioning adjusting device is arranged between the annular supporting ring beam and the mounting plate. The position of the central cylinder in the separator can be conveniently adjusted, so that the central cylinder and the cyclone separator are eccentrically arranged, the separation efficiency of the separator can be adjusted, and the problem that the material circulation ratio is not matched with the separation efficiency of the cyclone separator when the load and the fuel of the existing circulating fluidized bed boiler are changed is solved; the adaptability of boiler fuel combustion is improved, and the boiler heat efficiency and economic benefits are improved.

Description

Technical Field

[0001] This invention relates to a gas-solid separation component for flue gas in a circulating fluidized bed boiler, particularly a central cylinder of a cyclone separator, belonging to the technical field of circulating fluidized bed boilers. Background Technology

[0002] Circulating fluidized bed (CFB) boilers have experienced rapid development due to their advantages such as wide fuel adaptability, large load adjustment ratio, and superior environmental benefits. The cyclone separator is a crucial component of a CFB boiler. Its main function is to separate unburned solid particles from the boiler flue gas and return them to the combustion chamber via a return system for continued circulation and combustion. The separator's separation efficiency and operational performance determine the particle circulation ratio and material balance within the circulating fluidized bed, making it key to establishing stable circulation and crucial for stable combustion in the boiler furnace. An improperly designed separator structure will directly affect the stability and continuous circulation of solid particles, leading to decreased boiler combustion and desulfurization efficiency, increased wear on the tail-end heating surfaces, and compromised boiler safety and reliability.

[0003] Cyclone separators mainly consist of a cylindrical upper section, a funnel-shaped lower section, and a central cylinder. Currently, commonly used cyclone separator structures include... Figure 1 As shown in the figure, 1 is the inlet flue, 2 is the central cylinder with the flue gas outlet at its top, 3 is the cylindrical body, 4 is the ash collection pipe, and 5 is the funnel-shaped conical body. The working principle of the cyclone separator is to achieve gas-solid separation using centrifugal force. When the mixed flue gas containing unburned coal particles and dust from the boiler furnace enters the cylindrical body 3 tangentially through the inlet flue 1, the mixed flue gas containing unburned coal particles forms a rotating vortex in the cyclone separator under the action of centrifugal force. During the flow of air, the particles are subjected to the dual action of centrifugal force and gravity, and can follow the airflow in a spiral motion. The smaller the particle size, the better the following of the airflow. The larger the mass, the greater the centrifugal force and gravity, and will gradually move outward with the airflow, eventually being thrown to the wall and falling off the flue gas under its own gravity into the ash pipe 4. It is then sent back to the furnace through the return device to achieve fuel recycling. Particles with a density less than air are subjected to less centrifugal force than the airflow resistance and will enter the central cylinder 2 from the bottom with the flue gas, and then leave the cyclone separator from the flue gas outlet at the top of the central cylinder 2. In this way, the cyclone separator separates most of the unburned coal particles and dust from the flue gas, achieving gas-solid separation. Therefore, the separation efficiency of the cyclone separator determines the ash recycling rate, which directly affects the combustion efficiency and dust emissions of the boiler.

[0004] The central cylinder 2, located at the top of the cyclone separator, is a key component. It extends beyond the top of the cylinder 3 and is inserted into the inner cavity of the separator body. Its main function is to prevent short-circuiting of the flue gas in the furnace, improve the separator's separation efficiency, and ensure that as much dust containing unburned coal particles as possible is separated from the mixed flue gas. In existing technologies, the structure and dimensions of cyclone separators are usually determined through empirical formulas or CFD simulations, and once determined, they are not adjusted. With fixed separator dimensions, optimal separation efficiency is often not achieved when fuel composition or boiler load changes. This can easily lead to excessively high or low separation efficiency. Excessively high efficiency results in overly fine fly ash particles at the boiler tail, causing ash blockage on the convective heating surface, poor heat transfer, and high boiler exhaust temperature. Insufficient separation efficiency leads to insufficient circulating material, unstable combustion in the furnace, excessive nitrogen oxide emissions, and high carbon content in fly ash. The central cylinder of the separator is also fixed, typically using a hanging method. The central cylinder is secured to a hanger on the separator body using hooks, or supported by multiple brackets on the cyclone separator's protective plate. However, due to thermal stress, the central cylinder and the hangers or brackets can undergo significant deformation. Deformation or even breakage of the hangers or brackets can lead to changes in the separator's installation dimensions, and there have even been accidents where the central cylinder has fallen off. Clearly, once the central cylinder is installed, its structure is fixed and cannot be rotated or adjusted. Consequently, the separation efficiency of both the fixed-structure central cylinder and the fixed-structure cyclone separator is also unadjustable. In my country, however, circulating fluidized bed incineration technology, as a highly efficient and clean combustion technology, has been increasingly widely applied in recent years to various fuels, such as coal, biomass, waste, solid waste, and waste liquids and gases. Once the separator's structural dimensions are fixed, in actual production, when fuel composition or boiler load changes, the optimal separation efficiency is often not achieved. This can easily lead to either excessively high or low separation efficiency. Excessively high efficiency results in overly fine fly ash particles in the boiler tail gas, causing ash buildup on convective heating surfaces, ash blockage, poor heat transfer, and high boiler exhaust temperatures. Conversely, excessively low efficiency leads to excessive nitrogen oxide emissions, high carbon content in fly ash, insufficient circulating ash in the furnace, unstable combustion in the combustion chamber, impacting boiler operation, and larger fly ash particles, exacerbating wear on the tail heating surfaces. Therefore, to adapt to diverse fuels and wide load ranges, and to achieve better combustion, environmental performance, and safe and stable boiler unit operation, the separator's separation efficiency needs to be flexibly adjustable. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a central cylinder device with adjustable separation efficiency for a circulating fluidized bed boiler, so as to solve the problems existing in the background art.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows: A central cylinder device for adjustable separation efficiency in a circulating fluidized bed boiler includes an annular support beam, a cyclone separator, and a central cylinder connected to the boiler body steel frame. The cyclone separator includes a separator straight section, a separator conical section, and a separator ash discharge pipe connected sequentially from top to bottom. A flue gas inlet is provided on the side wall near the top of the separator straight section, and the upper part of the separator straight section is connected to and sealed to the annular support beam. The central cylinder is located at the top of the separator straight section, and the lower end of the central cylinder is inserted into the separator straight section. A flue gas outlet is provided at the top of the central cylinder. The central cylinder is characterized in that: an mounting plate protruding radially outward along the central cylinder is provided at the upper end of the central cylinder, and the mounting plate overlaps the annular support beam to suspend the central cylinder in the cyclone separator. A positioning adjustment device is provided between the annular support beam and the mounting plate.

[0007] In the aforementioned adjustable separation efficiency central cylinder device of the circulating fluidized bed boiler, the straight cylinder section, conical cylinder section, and ash discharge pipe of the cyclone separator are coaxially arranged on the separator axis; the central cylinder is eccentrically arranged with respect to the cyclone separator, and the positioning adjustment device can adjust the eccentricity between the separator axis and the central cylinder axis.

[0008] By adopting the above technical solution, the annular support ring beam is connected to the boiler body steel frame. The positioning holes on the annular ring beam are designed with oval holes, which can absorb the thermal expansion stress of the central cylinder. A positioning adjustment device is set between the annular support ring beam and the mounting plate. By horizontally rotating the central cylinder, its installation position on the support ring beam can be adjusted, so that the central cylinder and the cyclone separator are eccentrically set. This can adjust the separation efficiency of the separator, solve the problem of mismatch between the material circulation ratio and the separation efficiency of the cyclone separator when the load and fuel change in the existing circulating fluidized bed boiler. This improves the adaptability of boiler fuel combustion, reduces boiler environmental emissions, improves boiler thermal efficiency, and significantly improves economic benefits.

[0009] In the aforementioned adjustable separation efficiency central cylinder device of the circulating fluidized bed boiler, the positioning adjustment device includes at least two sets of adjustment holes and bolt connection pairs. The bolt connection pairs are inserted into the adjustment holes to fix the central cylinder to the annular support beam to prevent the central cylinder from falling off. Each set of adjustment holes has at least 4 pairs, and each pair of adjustment holes includes a first vertical through hole set on the annular support beam and a corresponding second vertical through hole set on the mounting plate.

[0010] By adopting the above technical solution, multiple sets of adjustment holes are set on the annular support beam and the mounting plate. By rotating the central cylinder horizontally, the position of the central cylinder in the separator can be easily adjusted so that the axis of the central cylinder deviates from the axis of the separator. The magnitude of the eccentricity and the relative position of the central cylinder and the flue gas inlet can be calculated by comprehensively considering data such as fuel characteristics, boiler operating parameters, separator resistance level and overall boiler layout.

[0011] In the central cylinder device of the above-mentioned circulating fluidized bed boiler with adjustable separation efficiency, the flue gas inlet is connected to the inlet flue, and the inlet flue and the straight section of the separator form a volute structure.

[0012] Furthermore, the cross-section of the inlet flue is rectangular, with its outer side tangent to the side of the straight section of the separator, and its inner side gradually narrowing towards the outer side, with an angle α of 10-30 degrees with the tangent of the straight section of the separator, so that the cross-section of the inlet flue gradually decreases along the flue gas flow direction; the upper and lower sides of the inlet flue are inclined downward along the flue gas flow direction, with an angle β of 5-10 degrees with the horizontal plane.

[0013] By adopting the above technical solution, the inlet flue is designed to slope downwards, which facilitates the flow of flue gas and dust, avoids large-area ash accumulation and coking, and easily achieves self-cleaning. The inner side of the inlet flue gradually narrows towards the outer side, causing the cross-section of the inlet flue to gradually decrease along the flue gas flow direction, thereby increasing the flow velocity of the flue gas. The inlet flue and the straight section of the separator form a volute structure, which can give the flue gas a large initial velocity through annular acceleration, so that the flue gas can be separated faster in the cyclone separator, improving separation efficiency. The upper and lower sides of the inlet flue are sloped downwards along the flue gas flow direction, so that the solid particles have a downward component velocity when they enter the separator with the flue gas, which is conducive to the solid particles reaching the bottom of the separator, further improving separation efficiency. After the flue gas enters the separator from the inlet flue, it first flows downwards in the outer ring, and then flows upwards in the inner ring, so that the flue gas flows in a nested double helix flow field state inside the cyclone separator, and finally flows out of the separator system through the central cylinder of the separator. Beneficial effects

[0014] This invention features multiple sets of adjustment holes between the annular support beam and the mounting plate, allowing for convenient adjustment of the central cylinder's position within the separator. This allows the central cylinder's axis to deviate from the separator's axis. The magnitude of this eccentricity and the relative position of the central cylinder to the flue gas inlet can be calculated based on a comprehensive consideration of fuel characteristics, boiler operating parameters, separator resistance levels, and the overall boiler layout. By horizontally rotating the central cylinder to adjust its installation position on the support beam, an eccentric setting between the central cylinder and the cyclone separator can be achieved, thus regulating the separator's separation efficiency. This solves the problem of mismatch between the material circulation ratio and the cyclone separator's separation efficiency in existing circulating fluidized bed boilers when load and fuel changes occur. It improves the boiler's adaptability to fuel combustion, expands the boiler's operating load range, improves environmental emissions, increases thermal efficiency, and significantly enhances economic benefits. The downward-sloping inlet flue facilitates flue gas flow, prevents large-area ash accumulation and coking, and promotes self-cleaning. The gradually decreasing cross-section of the inlet flue along the flue gas flow direction accelerates the flue gas velocity, resulting in faster separation of flue gas within the cyclone separator and improved separation efficiency. The downward slope of the upper and lower sides of the inlet flue along the flue gas flow direction allows solid particles to have a downward velocity as they enter the separator with the flue gas, which helps the solid particles reach the bottom of the separator and further improves the separation efficiency. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of an existing cyclone separator.

[0016] Figure 2 This is a front view schematic diagram of Embodiment 1 of the present invention.

[0017] Figure 3 yes Figure 2 AA section view diagram.

[0018] Figure 4 This is a schematic diagram of Embodiment 2 of the present invention.

[0019] Figure 5 This is a schematic diagram of Embodiment 3 of the present invention.

[0020] Figure 6 This is a top view schematic diagram of the annular support beam in this invention.

[0021] Figure 7 This is a top view of the central cylinder in this invention.

[0022] In the diagram: 1. Inlet flue, 1-1 upper side, 1-2 lower side, 1-3 outer side, 1-4 inner side, 2. Central cylinder, 2-1 mounting plate, 2-1-1 second vertical through hole, 3. Separator straight cylinder section, 3-1 bottom of the cylinder, 3-2 connecting cylinder, 4. Separator ash discharge pipe, 5. Separator conical cylinder section, 6. Annular support ring beam, 6-1 first vertical through hole, 7. Bolt connection pair. Detailed Implementation

[0023] To clearly illustrate the technical features of this solution, the invention will be further described below through non-limiting embodiments and in conjunction with the accompanying drawings. Example 1:

[0024] Please see Figure 2 , Figure 3The adjustable separation efficiency central cylinder device of the circulating fluidized bed boiler includes an annular support beam 6, a cyclone separator, and a central cylinder 2 connected to the boiler body steel frame. The cyclone separator includes a separator straight cylinder section 3, a separator conical section 5, and a separator ash discharge pipe 4 connected sequentially from top to bottom. A flue gas inlet is provided on the side wall near the top of the separator straight cylinder section 3. An inlet flue duct 1 is connected to the flue gas inlet. The inlet flue duct 1 and the separator straight cylinder section 3 form a volute structure. The cross-section of the inlet flue duct 1 is... It is rectangular, enclosed by outer side 1-3, inner side 1-4, upper side 1-1, and lower side 1-2. Its outer side 1-3 is tangent to the side of the straight section 3 of the separator, and the inner side 1-4 gradually contracts towards the outer side 1-3, with an angle α of 20 degrees with the tangent of the straight section 3 of the separator, so that the longitudinal section of the inlet flue 1 gradually decreases along the flue gas flow direction; the upper side 1-1 and lower side 1-2 of the inlet flue 1 slope downward along the flue gas flow direction, with an angle β of 8 degrees with the horizontal plane. The upper part of the straight section 3 of the separator is connected to and sealed with the annular support beam 6. Specifically, the top of the straight section 3 of the separator has a barrel bottom 3-1 with a central hole. The diameter of the central hole corresponds to the inner diameter of the annular support beam 6. A connecting cylinder 3-2 extends upward from the central hole and is welded and fixed to the inner hole of the annular support beam 6. Support beams / support columns are also provided on the straight section 3, the conical section 5, and the ash discharge pipe 4 of the separator. The support beams / support columns are connected to the boiler body steel frame to distribute and classify the load of the separator to the boiler body steel frame. This is existing technology and will not be described in detail. The central cylinder 2 is located at the top of the straight section 3 of the separator. The lower end of the central cylinder 2 is inserted into the straight section 3 of the separator. The top of the central cylinder 2 is provided with a flue gas outlet, which is connected to the outlet flue. The outlet flue is connected to the tail flue of the boiler. The upper end of the central cylinder 2 is provided with a mounting plate 2-1 that protrudes outward along the radial direction of the central cylinder 2. The mounting plate 2-1 overlaps the annular support beam 6 to suspend the central cylinder 2 inside the cyclone separator. A positioning adjustment device is provided between the annular support beam 6 and the mounting plate 2-1. The positioning adjustment device can adjust the eccentricity between the separator axis and the central cylinder axis. Specifically, the positioning adjustment device includes at least three sets of adjustment holes and bolt connection pairs 7. The bolt connection pairs 7 are inserted into the adjustment holes to fix the central cylinder 2 to the annular support beam 6 and prevent the central cylinder 2 from falling off. Each set of adjustment holes is provided with 4 pairs. Each pair of adjustment holes includes a first vertical through hole 6-1 provided on the annular support beam 6 and a corresponding second vertical through hole 2-1-1 provided on the mounting plate 2-1. In this embodiment, the separator straight section 3, separator conical section 5, separator ash discharge pipe 4, and annular support beam 6 of the cyclone separator are coaxially arranged on the separator axis; the central cylinder 2 is eccentrically arranged with respect to the cyclone separator. Figure 3 , Figure 3 In the diagram, point B1 is located at the centerline of the separator, while point B2 is located at the centerline of the central cylinder 2. Figure 3 As can be seen, the separator and the central cylinder 2 are not coaxial. In this embodiment, in the horizontal projection, point B2 is located on the side closer to the flue gas inlet, at the diameter of the tangent point between the outer side 1-3 of the inlet flue duct 1 and the straight section 3 of the separator. After offset, the central cylinder 2 is closer to the flue gas inlet, and the separator has a higher separation efficiency. When the boiler is cold, loosen the bolt connection pair 7, rotate the central cylinder 2 horizontally to align the other pair of adjustment holes between the annular support beam 6 and the central cylinder mounting plate 2-1, and then tighten the bolt connection pair 7. The adjustment is relatively convenient. Example 2:

[0025] Please see Figure 4 , Figure 4 In the diagram, point B1 is located at the centerline of the separator, while point B2 is located at the centerline of the central cylinder 2. Figure 4 As can be seen, the separator and the central cylinder 2 are not coaxial. In the horizontal projection, point B2 is located on the diameter of the tangent point between the outer side 1-3 of the inlet flue duct 1 and the straight section 3 of the separator, and is on the side away from the flue gas inlet. After the offset, the central cylinder 2 is far away from the flue gas inlet, and the separator has the highest separation efficiency. The cross-section of the inlet flue duct 1 is rectangular, formed by the outer side 1-3, the inner side 1-4, the upper side 1-1, and the lower side 1-2. Its outer side 1-3 is tangent to the side of the straight section 3 of the separator, and the inner side 1-4 gradually contracts towards the outer side 1-3, with an angle α of 30 degrees with the tangent of the straight section 3 of the separator, so that the longitudinal section of the inlet flue duct 1 gradually decreases along the flue gas flow direction; the upper side 1-1 and the lower side 1-2 of the inlet flue duct 1 slope downward along the flue gas flow direction, with an angle β of 10 degrees with the horizontal plane. The rest of the structure is the same as in Embodiment 1. Example 3:

[0026] Please see Figure 5 , Figure 5 In the diagram, point B1 is located at the centerline of the separator, while point B2 is located at the centerline of the central cylinder 2. Figure 5 As can be seen, the separator and the central cylinder 2 are not coaxial. In the horizontal projection, point B2 is located on the diameter of the tangent point between the outer side 1-3 of the inlet flue duct 1 and the straight section 3 of the separator, and is closer to the flue gas inlet. After the offset, the central cylinder 2 is closer to the flue gas inlet, and the separation efficiency of the separator is the lowest. The cross-section of the inlet flue duct 1 is rectangular, formed by the outer side 1-3, the inner side 1-4, the upper side 1-1, and the lower side 1-2. Its outer side 1-3 is tangent to the side of the straight section 3 of the separator, and the inner side 1-4 gradually contracts towards the outer side 1-3, with an angle α of 10 degrees with the tangent of the straight section 3 of the separator, so that the longitudinal section of the inlet flue duct 1 gradually decreases along the flue gas flow direction; the upper side 1-1 and the lower side 1-2 of the inlet flue duct 1 slope downward along the flue gas flow direction, with an angle β of 5 degrees with the horizontal plane. The rest of the structure is the same as in Embodiment 1.

[0027] In general, when the above-described Example 1 is applied to the actual production of a circulating fluidized bed boiler, the boiler's environmental performance is poor when the furnace combustion temperature is too high, and the boiler's load-carrying capacity is also limited. In this case, it is necessary to improve the separator's separation efficiency. The position of the central cylinder 2 can be rotated to the position described in Example 2. Figure 4 This moves the central cylinder 2 away from the separator inlet, reducing the possibility of material being directly drawn away, increasing the material circulation ratio, and increasing the heat transfer coefficient of the water-cooled wall, thereby reducing the furnace combustion temperature. When the furnace combustion temperature is low, the boiler combustion efficiency is low, and there is a risk of flameout. In this case, it is necessary to reduce the separator efficiency. The position of the central cylinder 2 can be rotated to the position in Example 3, see... Figure 5 This brings the central cylinder 2 closer to the separator inlet, increasing the possibility of material being directly drawn away, reducing the material circulation ratio, and decreasing the heat transfer coefficient of the water-cooled wall, which can achieve the effect of increasing the combustion temperature in the furnace.

[0028] Except for the technical features described in the specification, all other technologies are known to those skilled in the art.

[0029] The embodiments listed above are for understanding the present invention only and are not intended to limit the technical solutions described in the present invention. Those skilled in the art can make various changes or modifications based on the technical solutions described in the claims, and all equivalent changes or modifications should be covered within the scope of protection of the claims of the present invention.

Claims

1. A central cylinder device for adjustable separation efficiency in a circulating fluidized bed boiler, comprising an annular support beam, a cyclone separator, and a central cylinder connected to the boiler body steel frame, wherein the cyclone separator comprises a separator straight section, a separator conical section, and a separator ash discharge pipe connected sequentially from top to bottom, a flue gas inlet is provided on the side wall near the top of the separator straight section, and the upper part of the separator straight section is connected to and sealed to the annular support beam; the central cylinder is located at the top of the separator straight section, the lower end of the central cylinder is inserted into the separator straight section, and a flue gas outlet is provided at the top of the central cylinder, characterized in that: The upper end of the central cylinder is provided with a mounting plate that protrudes outward along the radial direction of the central cylinder. The mounting plate overlaps the annular support beam to suspend the central cylinder inside the cyclone separator. A positioning adjustment device is provided between the annular support beam and the mounting plate.

2. The central cylinder device for adjustable separation efficiency of a circulating fluidized bed boiler according to claim 1, characterized in that: The straight section, conical section, and ash discharge pipe of the cyclone separator are coaxially arranged on the separator axis; the central cylinder is eccentrically arranged with respect to the cyclone separator, and the positioning adjustment device can adjust the eccentricity between the separator axis and the central cylinder axis.

3. The central cylinder device for adjustable separation efficiency of a circulating fluidized bed boiler according to claim 2, characterized in that: The positioning and adjusting device includes at least two sets of adjusting holes and bolt connection pairs. The bolt connection pairs pass through the adjusting holes to fix the central cylinder to the annular support beam. Each set of adjusting holes has at least 4 pairs. Each pair of adjusting holes includes a first vertical through hole set on the annular support beam and a corresponding second vertical through hole set on the mounting plate.

4. The central cylinder device for adjustable separation efficiency of a circulating fluidized bed boiler according to claim 1, 2, or 3, characterized in that: The flue gas inlet is connected to the inlet flue, and the inlet flue and the straight section of the separator form a volute structure.

5. The central cylinder device for adjustable separation efficiency of a circulating fluidized bed boiler according to claim 4, characterized in that: The inlet flue has a rectangular cross-section, with its outer side tangent to the side of the straight section of the separator, and its inner side gradually narrowing towards the outer side. The angle α between the inner side and the tangent of the straight section of the separator is 10-30 degrees, so that the cross-section of the inlet flue gradually decreases along the flue gas flow direction. The upper and lower sides of the inlet flue slope downward along the flue gas flow direction, with an angle β between the inner side and the horizontal plane of 5-10 degrees.

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