SCR high temperature butterfly valve

Abstract

The application discloses an SCR high-temperature butterfly valve, which comprises a support rod, one end of which is rigidly connected with a butterfly plate, and the other end of which is a free end, and the free end is suspended on the upper surface of a bottom cover and leaves a thermal expansion gap, so that the support rod can be axially freely elongated at high temperature, and thermal extrusion on the butterfly plate is eliminated; an elastic groove is arranged on the outer periphery of a valve seat sealing ring, and the valve seat sealing ring is radially floatingly installed in a valve body sink hole, so that thermal expansion is absorbed, and dynamic automatic centering sealing is realized; a dustproof ring and a chip accommodating cavity are arranged between a driving rod and the valve body, the chip accommodating cavity is communicated with an injection gas blowing port, and the three parts cooperatively form a multi-stage dustproof system of "blocking - settling - blowing". The application is suitable for a high-temperature side block valve or a regulating valve of an SCR denitration system.

Description

Technical Field

[0001] This invention belongs to the field of butterfly valve technology, and specifically relates to an SCR high-temperature butterfly valve. Background Technology

[0002] When an SCR (Selective Catalytic Reduction) denitrification system operates on the high-temperature side between the economizer and the air preheater, the flue gas temperature can reach 600℃, containing high concentrations of fly ash dust and corrosive substances such as unreacted ammonia or ammonium bisulfate. Butterfly valves installed under these harsh conditions endure these conditions for extended periods. Existing butterfly valves suffer from the following main problems: fly ash particles easily intrude into the gaps between the valve stem and bushing, and the stuffing box, causing valve stem wear and jamming, and packing failure and leakage; ammonia corrodes the sealing surfaces and valve stem at high temperatures, accelerating surface damage; at 600℃, the inconsistent thermal expansion of the valve stem, butterfly plate, and valve body components easily leads to thermal compression of the butterfly plate by the bottom support structure, causing jamming or loss of control over the sealing gap; high-speed, dust-laden airflow continuously erodes the sealing surface, causing conventional hard-seal butterfly valves to exhibit significant leakage after only a few thousand openings and closings, resulting in a short sealing life. These problems are interconnected and difficult to solve simultaneously in existing butterfly valve structures. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides an SCR high-temperature butterfly valve, comprising a valve body, a butterfly plate, a drive rod, a support rod, a packing assembly, and a valve seat sealing ring. One end of the support rod is rigidly fixed to the butterfly plate, and the other end is a free end, which is suspended above the upper surface of the bottom cover and has a pre-reserved thermal expansion gap with the bottom cover. The valve seat sealing ring has an elastic groove on its outer circumference and is radially floatingly installed in the countersunk hole of the valve body. A dustproof ring and a chip cavity are provided between the drive rod and the valve body, and the chip cavity is connected to an injection air port.

[0004] Furthermore, the cross-section of the elastic groove is a symmetrical UVIR broken line combination structure, which includes a U-shaped segment, a V-shaped segment, an I-shaped straight segment and an R-shaped arc segment in sequence.

[0005] Furthermore, a support pad is provided between the free end of the support rod and the bottom cover, and the support pad is a steel wire reinforced graphite pad.

[0006] Furthermore, the injection port is located in the neck of the valve body, and the injection port is a self-sealing metal interface with a tapered sealing surface.

[0007] Furthermore, the dustproof ring is a fiber-woven dustproof ring.

[0008] Furthermore, the packing assembly includes at least 5 turns of fiber braided packing, with a spacer ring in the middle of the fiber braided packing.

[0009] Furthermore, the packing assembly also includes a packing pressure plate, a packing sleeve, and a packing pressure plate bolt. The packing pressure plate bolt has a waist-shaped structure and is equipped with a disc spring. The lower surface of the packing pressure plate is a conical surface, and the upper surface of the packing sleeve is a spherical surface.

[0010] Furthermore, the outer edge of the butterfly plate is provided with scraper-shaped corners; the drive rod and the butterfly plate are rigidly fixedly connected by double tensioning pins arranged along the flow channel direction.

[0011] Furthermore, the sealing surface of the butterfly plate is an integral rigid sealing surface, and the hardness of the sealing surface of the butterfly plate is higher than the hardness of the sealing surface of the valve seat sealing ring.

[0012] Furthermore, the valve body, butterfly plate, and drive rod are made of a high-temperature alloy resistant to ammonia corrosion.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: By setting a dustproof ring between the drive rod and the valve body to block dust intrusion, setting a chip-collecting cavity between the dustproof ring and the butterfly plate to reduce the medium flow rate and allow the dust to settle naturally, and periodically introducing compressed gas through the injection air port to blow away the deposited dust, a three-level synergistic dust prevention system of "blocking-settling-blowing" is constructed, which effectively prevents fly ash particles from entering the moving parts and overcomes the technical defects of existing butterfly valves caused by dust intrusion leading to valve rod wear and jamming and packing failure and leakage. By designing one end of the support rod as a free end suspended above the bottom cover and reserving a thermal expansion gap, and with the elastic buffer of the steel wire reinforced graphite support gasket, the support rod can freely extend axially at a high temperature of 600℃ without thermally compressing the butterfly plate; at the same time, the elastic groove on the outer periphery of the valve seat sealing ring absorbs radial and circumferential thermal expansion, and the disc spring of the packing pressure plate bolt continuously compensates for the relaxation of the packing preload, thus eliminating the risk of thermal expansion jamming as a whole and solving the technical problems of existing butterfly valves jamming or uncontrolled sealing gaps under large temperature difference conditions.

[0014] The valve seat sealing ring automatically centers by radial floating of the elastic groove, the rigid and flexible sealing pair dynamically coordinates deformation, and the outer edge of the butterfly plate continuously removes dust from the sealing area during rotation. The three factors work together to make the sealing pressure evenly distributed and suppress coking and jamming caused by dust accumulation, which significantly extends the sealing life and overcomes the technical defect of existing hard-seal butterfly valves that show obvious leakage after thousands of opening and closing cycles. By optimizing the triple eccentric parameters, the butterfly plate can quickly disengage from the valve seat seal ring when opening. Combined with the scraper-shaped edges and corners to reduce dust obstruction of the sealing powder, the switching torque is significantly reduced compared to conventional triple eccentric butterfly valves. At the same time, the optimized butterfly plate structure increases the flow channel area and reduces drive energy consumption. By using ammonia-resistant high-temperature alloys for the valve body, butterfly plate, and drive rod, and by treating the sealing surface with ammonia corrosion resistance, the valve's metal components are protected from chemical corrosion by high-temperature ammonia and ammonium bisulfate in the SCR denitrification system. This solves the technical problem of accelerated damage to the sealing surface and valve stem of existing butterfly valves in ammonia-corrosive environments. Attached Figure Description

[0015] Figure 1 This is a longitudinal sectional view of the overall structure of an SCR high-temperature butterfly valve according to a certain embodiment of the present invention; Figure 2 This is a partially enlarged cross-sectional view of the elastic groove on the outer periphery of the valve seat sealing ring according to a certain embodiment of the present invention; Figure 3 This is a partial sectional view of the assembly relationship between the free end of the support rod and the bottom cover in a certain embodiment of the present invention; Figure 4 This is a partial cross-sectional view of the injection port in a certain embodiment of the present invention. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0017] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are 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.

[0018] This application provides a high-temperature butterfly valve for SCR systems, suitable for high-temperature operation between the economizer and air preheater in SCR denitrification systems, where the flue gas temperature can reach up to 600℃ and contains high concentrations of fly ash and corrosive substances such as unreacted ammonia or ammonium bisulfate. This butterfly valve eliminates thermal compression jamming through a flexible free-end structure on the support rod, achieves dynamic sealing compensation through radial floating of the valve seat sealing ring's elastic groove, and forms a multi-stage dustproof system with a dustproof ring, chip chamber, and injection port. This collaboratively solves the coupled technical problems of dust intrusion into moving parts, ammonia corrosion, thermal expansion jamming, and short seal life.

[0019] Specifically as follows: Reference Figure 1In some embodiments of this application, the SCR high-temperature butterfly valve includes a valve body, a butterfly plate, a drive rod, a support rod, a packing assembly, a valve seat sealing ring, and a bottom cover. The butterfly plate is installed in the flow channel of the valve body. The drive rod passes through the upper neck of the valve body and connects to the butterfly plate. The support rod is located in the lower part of the valve body and connects to the bottom of the butterfly plate. The bottom cover seals the lower end of the valve body. The valve seat sealing ring is installed in a countersunk hole in the inner wall of the valve body, forming a sealing pair with the sealing surface of the butterfly plate. The packing assembly is located on the outer periphery of the drive rod in the neck of the valve body to prevent the medium from leaking outward along the drive rod. A bushing is provided between the drive rod and the valve body, and the bushing supports the rotation of the drive rod.

[0020] One end of the support rod is rigidly fixed to the bottom of the butterfly plate with an interference fit, while the other end is a free end that hangs directly above the upper surface of the bottom cover, with a pre-existing thermal expansion gap between it and the bottom cover. Under high-temperature conditions, the support rod extends freely downwards axially due to heat. Because of the sufficient thermal expansion gap between the free end and the bottom cover, the thermal expansion of the support rod will not exert an axial thrust on the butterfly plate, thus eliminating the risk of jamming caused by the support rod's thermal expansion locking the butterfly plate and ensuring flexible valve operation at high temperatures. A bottom cover gasket is installed between the bottom cover and the valve body. The bottom cover gasket uses a composite structure of expanded graphite and stainless steel to achieve a seal at the mating surfaces of the bottom cover and the valve body.

[0021] Combination Figure 3 In some embodiments of this application, a support gasket is provided between the free end of the support rod and the upper surface of the bottom cover. The support gasket is a steel wire reinforced graphite gasket. The steel wire reinforced graphite gasket has good compressibility and resilience, which can adjust the initial assembly gap between the free end of the support rod and the bottom cover and buffer axial loads, adapting to the thermal expansion deformation of the support rod under high temperature conditions of 600℃. Because the support gasket is compressible and resilient, it maintains flexible contact between the free end of the support rod and the bottom cover during temperature alternation, preventing radial swaying of the support rod due to excessive gap.

[0022] The valve seat seal ring is installed in a countersunk hole on the inner wall of the valve body. A radial clearance is maintained between the outer circumference of the valve seat seal ring and the inner wall of the countersunk hole, allowing the valve seat seal ring to float radially within the countersunk hole. The valve seat seal ring pressure plate is fixed to the valve body by several heat-resistant steel pressure plate screws, axially confining the valve seat seal ring within the countersunk hole while allowing it to float radially. A gasket is provided between the pressure plate screws and the valve body. The gasket is made of heat-resistant metal braided fiber material with a thickness of approximately 0.5 mm, used to compensate for the sealing of the mating surface between the valve seat seal ring pressure plate and the valve body. The butterfly plate sealing surface is an integral rigid structure, and its surface hardness is higher than that of the valve seat seal ring sealing surface. The two form a rigid-flexible sealing pair with a hard surface against a soft surface. Under the scouring of dusty airflow, the softer valve seat seal ring sealing surface preferentially experiences slight wear, while the valve seat seal ring automatically compensates for the wear through radial floating, continuously maintaining the sealing pressure with the butterfly plate sealing surface, thereby extending the sealing life.

[0023] Combination Figure 2 In some embodiments of this application, an elastic groove is formed on the outer periphery of the valve seat seal ring. The cross-section of the elastic groove is a symmetrical UVIR broken line combination structure, which includes a U-shaped segment, a V-shaped segment, an I-shaped straight segment, and an R-shaped arc segment along the cross-sectional contour. The U-shaped segment provides the main elastic deformation space, the V-shaped segment disperses the stress over a larger range, the I-shaped straight segment realizes the transition connection between the segments, and the R-shaped arc segment eliminates stress concentration at the corners of the cross-section. Under high-temperature conditions, the valve seat seal ring expands due to heat, and the segments of the elastic groove deform collaboratively to absorb the radial and circumferential thermal expansion of the valve seat seal ring, preventing excessive sealing pressure or extrusion of the valve seat seal ring from the countersunk hole due to thermal expansion, while maintaining a uniform distribution of sealing pressure along the circumference of the sealing surface. The radial floating and elastic deformation of the elastic groove work together to enable the valve seat seal ring to achieve dynamic automatic centering at high temperatures, always maintaining uniform contact with the butterfly plate sealing surface.

[0024] In some embodiments of this application, a dustproof ring and a chip-collecting cavity are provided between the drive rod and the valve body. The dustproof ring is located between the bushing and the drive rod near the butterfly plate. The chip-collecting cavity is located on the inner wall of the valve body between the dustproof ring and the butterfly plate. The chip-collecting cavity has an annular concave structure and is connected to an injection air port. The dustproof ring is fitted around the outer periphery of the drive rod, and its inner diameter matches the outer diameter of the drive rod, preventing dust-laden media from entering upwards along the gap between the drive rod and the bushing. The chip-collecting cavity reduces the flow velocity of the medium by suddenly expanding its cross-section, allowing fly ash particles flowing with the medium to naturally settle and accumulate in the chip-collecting cavity, reducing the amount of dust reaching the dustproof ring. The injection air port is connected to the chip-collecting cavity, allowing compressed gas to be periodically introduced into the chip-collecting cavity to blow away the deposited dust, preventing the dust from accumulating and being re-raised and intruding into the moving parts. The dustproof ring, the chip-collecting cavity, and the injection air port work together to form a multi-stage dust prevention system of "blocking-settling-blowing".

[0025] In some embodiments of this application, the dust ring is a fiber-woven dust ring made of high-temperature resistant ceramic fibers. The fiber-woven structure gives the dust ring a certain degree of elasticity, enabling it to maintain a stable contact fit with the outer periphery of the drive rod at high temperatures, effectively preventing fly ash particles from entering the gap between the drive rod and the bushing for a long period of time.

[0026] Combination Figure 4 In some embodiments of this application, the injection port is located in the neck of the valve body, i.e., the location where the packing assembly is installed. The injection port is a self-sealing metal interface with a conical sealing surface, and there is no one-way valve or other moving parts inside the interface. When an external air source is connected, the conical sealing surface mates with the conical surface of the air source connector to achieve automatic sealing, without the need for additional sealing elements. Compressed air or nitrogen can be periodically introduced, and the gas enters the chip chamber through the injection port to blow away the dust deposited in the chip chamber, preventing the dust from accumulating and re-entering the moving parts.

[0027] In some embodiments of this application, the packing assembly includes packing, a packing pad, a packing sleeve, a packing plate, and packing plate bolts. The packing pad is fitted around the outer periphery of the drive rod and located within the stuffing box of the valve body neck, consisting of six rings. Two rings are a combination of flexible graphite and wire-reinforced rings, one ring is a ceramic fiber braided spacer ring, and three rings are vermiculite fiber packing. The spacer ring is positioned in the middle of the packing, dividing it into upper and lower groups to prevent overall creep and relaxation of the single packing material under temperature fluctuations, maintaining a stable sealing preload. The packing pad, made of 316L stainless steel, is located below the packing and supports the packing, preventing it from being squeezed downwards. The packing sleeve is positioned above the packing, with its upper surface machined into a spherical shape with a radius of SR50, forming a spherical-conical mating contact with the conical surface of the lower surface of the packing plate. The cone angle of the lower surface of the packing plate is 120°. This ball-cone fit enables automatic alignment between the packing plate and the packing sleeve, ensuring uniform pressure on the packing along the circumference of the drive rod and preventing localized leakage due to uneven loading. The packing gland bolts pass through the packing gland and press it against the valve body neck. The packing gland bolts employ a waist-shaped structure, with a reduced cross-section in the middle and equipped with a disc spring. This waist-shaped structure allows for a certain amount of elastic elongation of the bolt, while the disc spring continuously provides axial preload. This automatically compensates for packing compression force when packing loosens due to temperature fluctuations, maintaining a stable packing seal. A 0.2mm gap is maintained between the packing gasket, packing sleeve, and drive rod to prevent the packing from being squeezed out and blocking the drive rod's rotation clearance under pressure.

[0028] In some embodiments of this application, the drive rod and the butterfly plate are rigidly connected by double-tensioning straight pins arranged along the flow channel direction. The two tensioning straight pins are arranged parallel to each other along the flow channel direction, passing through corresponding pin holes on the drive rod and the butterfly plate respectively, and are fixed together by tensioning. The double-pin arrangement along the flow channel direction ensures reliable transmission of the rotational torque of the drive rod. Even if the pin holes deform slightly due to thermal expansion at high temperatures, the double-pin structure can still maintain reliable torque transmission, preventing relative rotation between the drive rod and the butterfly plate due to loosening caused by thermal expansion in a single-pin connection. A bushing is provided between the drive rod and the valve body. The bushing is made of highly spheroidized wear-resistant cast iron, and the radial clearance between the drive rod and the bushing is 0.1mm to 0.15mm, ensuring flexible rotation of the drive rod while limiting its radial runout.

[0029] In some embodiments of this application, the outer edge of the butterfly plate is machined with a scraper-shaped edge, the cutting angle of which is 30° and the radius of the root arc is R0.5mm. During the opening or closing process of the butterfly plate, the scraper-shaped edge rotates with the butterfly plate, which can remove dust particles or ammonium salt crystals adhering to the sealing surface of the valve seat sealing ring, preventing dust and ammonium salt accumulation from causing coking and blockage on the sealing surface, reducing the operating torque required for butterfly plate opening and closing, and reducing wear on the sealing surface caused by dust accumulation, thereby extending the sealing life.

[0030] In some embodiments of this application, the valve body, butterfly plate, and drive rod are made of ammonia-resistant high-temperature alloys. These ammonia-resistant high-temperature alloys can resist the chemical corrosion of the valve's main pressure-bearing and moving parts by corrosive substances such as high-temperature ammonia and ammonium bisulfate in the SCR denitrification system. The butterfly plate sealing surface and the valve seat sealing ring sealing surface are treated with ammonia corrosion resistance hardening, for example, by using a PVD physical vapor deposition process to deposit a TiAlSiN coating. The coating hardness can reach HV2800 to 3800, making the butterfly plate sealing surface harder than the valve seat sealing ring sealing surface, forming a rigid-flexible sealing pair with a hard surface against a soft surface. Under the scouring of dusty airflow, the valve seat sealing ring sealing surface preferentially bears the wear, and continuous compensation through radial floating extends the overall sealing life.

[0031] In some embodiments of this application, for operating conditions where the temperature does not exceed 450°C and the dust contains ferromagnetic particles, the purging medium at the injection nozzle can be changed to nitrogen to prevent oxygen from entering the chip cavity and causing an oxidation reaction during purging. Simultaneously, a removable magnetic trapping grid can be added inside the chip cavity. This grid magnetically adsorbs the ferromagnetic dust particles deposited within the cavity, allowing for periodic disassembly and cleaning, further improving dust collection efficiency and preventing secondary intrusion of accumulated ferromagnetic dust into the moving parts. Under these conditions, the packing material can be entirely composed of flexible graphite rings reinforced with Inconel alloy wire, totaling seven rings, to meet sealing requirements at relatively low temperatures and improve the packing's corrosion resistance.

[0032] In summary, these are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the specification are within the scope of the present invention.

Claims

1. A high-temperature SCR butterfly valve, comprising a valve body, a butterfly plate, a drive rod, a support rod, a packing assembly, and a valve seat sealing ring, characterized in that: One end of the support rod is rigidly fixed to the butterfly plate, and the other end is a free end. The free end is suspended above the bottom cover and a thermal expansion gap is reserved between it and the bottom cover. The valve seat sealing ring has an elastic groove on its outer circumference and is radially floating in the countersunk hole of the valve body. A dustproof ring and a chip cavity are provided between the drive rod and the valve body. The chip cavity is connected to an injection air port.

2. The SCR high-temperature butterfly valve according to claim 1, characterized in that: The cross-section of the elastic groove is a symmetrical UVIR broken line combination structure, which includes a U-shaped segment, a V-shaped segment, an I-shaped straight segment and an R-shaped arc segment in sequence.

3. The SCR high-temperature butterfly valve according to claim 1, characterized in that: A support pad is provided between the free end of the support rod and the bottom cover. The support pad is a steel wire reinforced graphite pad.

4. The SCR high-temperature butterfly valve according to claim 1, characterized in that: The injection port is located in the neck of the valve body, and the injection port is a self-sealing metal interface with a tapered sealing surface.

5. The SCR high-temperature butterfly valve according to claim 1, characterized in that: The dustproof ring is a fiber-woven dustproof ring.

6. The SCR high-temperature butterfly valve according to claim 1, characterized in that: The packing assembly includes at least 5 turns of fiber braided packing, with a spacer ring in the middle of the fiber braided packing.

7. The SCR high-temperature butterfly valve according to claim 1, characterized in that: The packing assembly also includes a packing pressure plate, a packing sleeve, and a packing pressure plate bolt. The packing pressure plate bolt has a waist-shaped structure and is equipped with a disc spring. The lower surface of the packing pressure plate is a conical surface, and the upper surface of the packing sleeve is a spherical surface.

8. The SCR high-temperature butterfly valve according to claim 1, characterized in that: The outer edge of the butterfly plate is provided with scraper-shaped corners; the drive rod and the butterfly plate are rigidly fixedly connected by double tensioning pins arranged along the flow channel direction.

9. The SCR high-temperature butterfly valve according to claim 1, characterized in that: The sealing surface of the butterfly plate is an integral rigid sealing surface, and the hardness of the sealing surface of the butterfly plate is higher than that of the sealing surface of the valve seat sealing ring.

10. The SCR high-temperature butterfly valve according to claim 1, characterized in that: The valve body, butterfly plate, and drive rod are made of ammonia-resistant high-temperature alloy.

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