Gas-steam boiler with premixed water-cooled combustion and enhanced heat exchange

Abstract

The application discloses a gas-steam boiler with pipe coupling plate premixed water-cooled combustion and enhanced heat exchange, which comprises an air blower, a burner, a pipe coupling plate premixed water-cooled combustion pipe screen, a pipe coupling plate fin enhanced heat exchange pipe bundle, a membrane wall downcomer pipe screen, a spiral fin convection pipe bundle and an energy-saving condensing pipe bundle; air and natural gas sent by the air blower are mixed in a premixer, ignited after passing through the pipe coupling plate premixed water-cooled combustion pipe screen and surface combustion is completed, high-temperature flue gas after combustion flows through the gaps between the pipe coupling plate fin enhanced heat exchange pipe bundle, and then secondarily washes the spiral fin convection pipe bundle and the energy-saving condensing pipe bundle, is deeply cooled and condensed, and is discharged from a chimney; water in a lower header is heated into steam after passing through the heat exchange pipe bundle and is discharged from an exhaust port of an upper header. The application can greatly improve heat exchange efficiency, reduce pollutant emission, make the boiler structure more compact, reduce flow resistance, simplify the process and realize reduction of carbon emission in the whole supply chain of raw materials, production, processing and operation.

Description

Technical Field

[0001] This invention relates to the field of gas-fired boiler technology, specifically to a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate. Background Technology

[0002] Gas-fired steam boilers are characterized by high efficiency, energy saving, environmental friendliness, safety, stable operation, convenient maintenance, and strong adaptability. Industries such as textiles, chemicals, and food processing still require a large number of gas-fired steam boilers ranging from 0.1 to 10 tons as an energy source. Currently, there are many types of gas-fired steam boilers on the market. However, existing gas-fired steam boilers, such as those registered by Chongqing Yesen Thermal Energy Equipment Co., Ltd. (CN219177670U) and Shanghai Yangnuo Boiler Manufacturing Co., Ltd. (CN107781800A), suffer from low burner combustion efficiency, high combustion resistance, and nitrogen oxide emissions exceeding 30 mg / m³. 3 The process has high carbon emissions, which does not meet the national requirements for energy conservation and emission reduction. The traditional flue gas turbulence-enhanced heat transfer method has weak enhancement capabilities, requires a significant increase in the boiler heating surface area, and also increases the number of heat exchange tube bundles, material costs, and welding workload, resulting in a significant increase in process carbon emissions. Summary of the Invention

[0003] To address the problems existing in gas-fired steam boilers, the present invention aims to provide a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube-coupled plate. The boiler employs a tube-coupled plate premixed water-cooled combustion tube panel, where adjacent bare tubes of the heat exchange tube bundle are welded together with flat steel. Two rows of radial holes are formed on the flat steel, allowing the mixed gas to form a staggered flow outside the flat steel. After ignition and combustion, this improves flame stability, reduces flame length, lowers flame temperature, and ensures that nitrogen oxide emissions from the gas burner are less than 30 mg / m³. 3 The combustion efficiency is greater than 99.8%, reducing combustion resistance by 40% compared to traditional domestic burners and effectively reducing carbon emissions by 10% to 30% or more. It employs a tube-coupled plate-fin enhanced heat exchange tube bundle with "laminar flow enhancement" heat exchange. The tube bundles form gap channels, which eliminate the central high-temperature zone in traditional heat exchange processes. When flue gas passes through these gap channels, the entire channel is in a boundary layer region with strong heat and mass transfer, achieving a heat transfer coefficient of up to 130 W / m³. 2 ·℃ or above.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube-coupled plate, arranged vertically, including a burner, a tube-coupled plate premixed water-cooled combustion tube panel, a tube-coupled plate finned enhanced heat exchange tube bundle, a membrane wall downcomer tube panel, a spiral finned convection tube bundle, an energy-saving condensing tube bundle, an upper steam-water chamber, a lower water chamber, a boiler shell, and a chimney; the tube-coupled plate premixed water-cooled combustion tube panel, the tube-coupled plate finned enhanced heat exchange tube bundle, and the membrane wall downcomer tube panel are arranged concentrically from the inside out, and the tube-coupled plate premixed water-cooled combustion tube panel and the tube-coupled plate finned enhanced heat exchange tube bundle are arranged concentrically from the inside out. The annular space between the enhanced heat exchange tube bundles forms the furnace. The space between the tube-coupled plate-fin enhanced heat exchange tube bundles and the membrane wall downcomer tube screen forms the flue gas passage. The spiral finned convection tube bundles, energy-saving condensing tube bundles, and chimney are arranged on one side of the boiler shell along the flue gas flow direction. The upper steam-water chamber and the lower water chamber are annular headers. The tube-coupled plate premixed water-cooled combustion tube screen, the tube-coupled plate-fin enhanced heat exchange tube bundles, the membrane wall downcomer tube screen, and the spiral finned convection tube bundles connect the upper steam-water chamber and the lower water chamber. The tube-coupled plate-fin enhanced heat exchange tube bundles are equipped with slit-type flue gas passages. The burner is located at the top center position.

[0005] The spiral finned convection tube bundles are arranged in three rows. The upper and lower ends of the first row of spiral finned convection tube bundles extend into the bottom and top of the upper steam-water chamber and the lower water chamber, respectively. The base tubes of the second and third rows of spiral finned convection tube bundles are bent into a "C" shape. The upper and lower ends of the second and third rows of spiral finned convection tube bundles extend into the upper steam-water chamber and the lower water chamber from the outer side of the upper steam-water chamber and the lower water chamber, respectively. The upper and lower ends of the tube coupling plate premixed water-cooled combustion tube screen extend into the upper steam-water chamber and the lower water chamber from the inner side of the upper steam-water chamber and the lower water chamber, respectively.

[0006] The tube-coupled plate-fin enhanced heat exchange tube bundle adopts folded finned tubes, which include a base tube and fins. The base tube is a necked plain tube, and the fins include interconnected folded fins and front fins. The front fins are connected to the plain tube, and there is a bend angle between the folded fins and the front fins. The folded fins are suspended, and longitudinal ribs are provided on the surface of the fins. The angle of the fin bend is set so that the folded fin of the previous tube and the front fin of the next tube are parallel. The thickness of the fins is the largest at the beginning and gradually decreases along the airflow direction. The thickness of the folded fins remains unchanged along the airflow direction. A gap channel is formed between the folded fin of the previous tube and the front fin of the next tube. The width of the gap channel between the folded fin of the previous tube and the front fin of the next tube is 0.2 to 1 mm. The base tube and fins are beveled inside and out and connected by TIG welding, MIG welding or laser welding. The base tube is made of materials specified in the gas boiler standard, and the fins are made of materials with a thermal conductivity of not less than 200 W / (m·K).

[0007] The longitudinal ribs include rectangular or wavy longitudinal ribs set on the outer surface of the forewing and the inner surface of the folded wing. The rectangular and wavy longitudinal ribs are formed by laser cutting, stamping or etching processes.

[0008] The longitudinal ribs can be either cross-sectional or longitudinally intersecting. The cross-sectional ribs are cross-sectional and longitudinally intersecting turbulence column-shaped ribs. The longitudinal ribs on the outer surface of the forewing and the inner surface of the folded wing combine to form a "labyrinthine flue gas channel". The cross-sectional and longitudinally intersecting ribs are formed by laser cutting, stamping and etching processes.

[0009] The boiler shell and the membrane wall downcomer screen are lined with thermal insulation material. The annular space formed between the upper steam and water chamber inner side and the flow equalization plate is filled with refractory mortar. The columnar space enclosed by the lower water chamber inner side is filled with refractory mortar.

[0010] The tube coupling plate premixed water-cooled combustion tube screen includes multiple "C"-shaped heat exchange tubes. Adjacent heat exchange tubes are welded together with flat steel. Through holes are opened on the flat steel at a set angle, either sequentially or staggered. The through holes are circular, rhomboid, rectangular, or oblong. The heat exchange tubes are arranged vertically to form the tube coupling plate premixed water-cooled combustion tube screen. A flow equalization orifice plate is set on the inner side of the tube coupling plate premixed water-cooled combustion tube screen. The flow equalization orifice plate is cylindrical and ends at the sealing orifice plate at the top of the lower water chamber. The starting drilling position is below the sealing orifice plate of the upper steam-water chamber. The thickness of the flow equalization orifice plate is 10~15mm.

[0011] The upper steam chamber has two L-shaped folding plates on the inner side of its upper surface. The two L-shaped folding plates are arranged opposite each other, and the width and height of one L-shaped folding plate are smaller than the other L-shaped folding plate. The lower water chamber has a water inlet on its outer side and a sealing plate at the bottom. The upper steam chamber has a safety valve, a steam outlet, a pressure gauge and a pressure sensor at the top, and a water level gauge interface on its side.

[0012] The top of the boiler shell connects to the bottom of the upper steam-water chamber and the top outer edge of the lower water chamber, surrounding the spiral fin convection tube bundle and the energy-saving condenser tube bundle. The tail of the boiler is connected to a square-to-round structure flue shell, and the tail of the square-to-round structure flue shell is connected to the chimney, with a condensate drain hole at the bottom. A burner mounting panel is set at the center of the top of the upper steam-water chamber, and the burner is fixed on the burner mounting panel. The burner is connected to a blower, and a flow equalization plate is welded to the bottom of the burner mounting panel.

[0013] The upper steam-water chamber is equipped with an upper header, and the lower water chamber is equipped with a lower header. The base tube of the premixed water-cooled combustion tube screen of the pipe coupling plate adopts a vertical necked smooth tube. The upper and lower ends of the base tube extend into the bottom and top of the upper and lower headers, respectively. The upper surface of the upper steam-water chamber is a smooth plate.

[0014] The lower header contains an atomizer, whose inlet is connected to the lower water chamber.

[0015] The upper steam chamber and the upper header are connected by an elbow, and the lower water chamber and the lower header are connected by an elbow.

[0016] The membrane wall downcomer screen includes multiple heat exchange tubes, multiple heat exchange tube bundles are arranged vertically, and adjacent heat exchange tubes are sealed by welding flat steel. The membrane wall downcomer screen is arranged along a vortex line to form an equal pressure flue gas channel with gradually increasing width.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] This invention discloses a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube-coupled plate. It employs the concept of laminar flow enhanced heat exchange, eliminating the central high-temperature zone in the flue gas heat exchange process through slit channels. This allows the boiler flue gas to be cooled from above 1150℃ to below 280℃ in a mere 50mm to 200mm length, while simultaneously controlling the flue gas resistance below 1000Pa, reducing the boiler's steam consumption per ton of steel and water volume. Furthermore, this invention enables stable, fully premixed water-cooled combustion of natural gas, effectively reducing flame length and temperature, and ensuring that nitrogen oxide emissions from the gas burner are less than 30mg / m³. 3 With a combustion efficiency of over 99.8%, it can reduce combustion resistance by 40% compared to traditional burners, effectively reducing carbon emissions by 10% to 30% or more. At the same time, the built-in premixer makes the boiler structure more compact, further reducing the boiler volume.

[0019] Furthermore, this invention adopts a low-flow-rate, short-process design concept, with the energy-saving device being semi-integrated and the condenser being external, making full use of the waste heat of the flue gas to reduce the flue gas temperature to below 50°C and improve the boiler efficiency by more than 10%.

[0020] Furthermore, the core heat exchange element of the gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange of the present invention is a coupled finned evaporative heat exchange tube. A natural V-shaped bevel is formed between the base tube and the fins. The structure is simple and easy to process, produce and assemble on a large scale. The fins are bent and longitudinal ribs are added, which increases the heat exchange area and forms a stable gap channel between the front and rear heat exchange tube bundles, which greatly improves the effect of enhanced heat transfer.

[0021] Furthermore, the gas-fired steam boiler of the present invention with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate can adopt a type of burner that is detachable as a whole, which facilitates the maintenance and repair of the burner. Phase change occurs in the water-cooled combustion tube bundle to enhance heat transfer and reduce the metal wall temperature. Attached Figure Description

[0022] The invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1a This is a front cross-sectional view of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate, according to the present invention. Figure 1bThis is a top view of the furnace body of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate, according to the present invention. Figure 1c This is a right sectional view of an energy-saving condenser for a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate, according to the present invention. Figure 1d This is the upper right view of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate, according to the present invention.

[0024] Figure 2a This is a schematic diagram of a premixed water-cooled combustion tube panel with radially perforated flat steel for welding a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange using a tube coupling plate according to the present invention. Figure 2b A schematic diagram showing square holes at a certain angle on the flat steel of the premixed water-cooled combustion tube panel for the tube coupling plate. Figure 2c A schematic diagram of circular holes at a set angle on the flat steel of the premixed water-cooled combustion tube panel for the tube coupling plate. Figure 2d For the tube coupling plate, the premixed water-cooled combustion tube panel tube bundle flat steel is different from the flat steel. Figure 2c Schematic diagram of a circular hole at an angle; Figure 2e A schematic diagram showing diamond-shaped holes at a set angle on the flat steel of the premixed water-cooled combustion tube panel for the tube coupling plate.

[0025] Figure 3a This is a partial cross-sectional schematic diagram of the tube bundle 4, which is composed of folded finned tubes to form a jet, turbulent, and laminar flow enhanced heat transfer channel. Figure 3b This is a partial cross-sectional schematic diagram of the tube bundle 4, which is composed of folded finned tubes to form a laminar flow enhanced heat transfer channel. Figure 3c This is a schematic diagram of the tube-coupled plate-fin enhanced heat exchange tube bundle 4, which uses folded finned tubes and rectangular longitudinal ribs 431 and 432 to form a gap channel. Figure 3d This is a schematic diagram of the gap channel formed by the wavy longitudinal ribs 431 and 432 of the tube-coupled plate-fin enhanced heat exchange tube bundle 4. Figure 3e This is a perspective view of the slot channel formed by the cross-ribbed ribs of the tube coupling plate-fin enhanced heat exchange tube bundle 4. Figure 3f This is a perspective view of the slot channel formed by longitudinally staggered ribs in the tube-coupled plate-fin enhanced heat exchange tube bundle 4. Figure 3g This is a perspective view of the slot channel formed by the cross-sectional and longitudinal turbulent column-shaped ribs of the tube-coupled plate-fin enhanced heat exchange tube bundle 4.

[0026] Figure 4 This is a schematic diagram of the annular membrane wall downcomer screen 5 of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a pipe coupling plate according to the present invention.

[0027] Figure 5 This is a front sectional view of the upper steam-water chamber 8 of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate, according to the present invention.

[0028] Figure 6 This is a front sectional view of the lower water chamber 9 of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate, according to the present invention.

[0029] Figure 7 This is a schematic diagram of the flow equalization orifice plate and different orifice shapes of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate according to the present invention.

[0030] Figure 8 This is a schematic diagram of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate, which forms an isobaric flue gas channel by arranging a membrane wall downcomer screen along a vortex line.

[0031] Figure 9a This is a front sectional view of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange using a tube coupling plate, which outputs superheated steam with an integrally detachable burner. Figure 9b The upper right view shows the gas-fired steam boiler of the present invention, which adopts a burner with an integral detachable design and premixed water-cooled combustion and enhanced heat exchange via a tube coupling plate. Figure 9c This is the upper left rear view of the gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange using a tube coupling plate according to the present invention, which adopts an overall detachable burner design. Figure 9d This is an overall schematic diagram of a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange using a tube coupling plate and an integrally detachable burner to output saturated steam.

[0032] Figure 10 This is a schematic diagram of the atomizer 20 added when the gas-fired steam boiler of the present invention, which uses a premixed water-cooled combustion and enhanced heat exchange method with a tube coupling plate and outputs superheated steam with an integrally detachable burner, is used.

[0033] 1-Blower, 2-Burner, 3-Pipe-coupled plate premixed water-cooled combustion tube panel, 4-Pipe-coupled plate finned heat exchange tube bundle, 5-Membrane wall downcomer panel, 6-Helical finned convection tube bundle, 7-Energy-saving condenser tube bundle, 8-Upper steam-water chamber, 9-Lower water chamber, 10-Boiler shell, 11-Square to round structure, 12-Chimney, 13-Flow equalization orifice plate, 14-Safety valve, 15-Condensate drain hole, 16-Burner mounting panel, 18-Sealing plate, 19-"L" shaped folding plate, 171-First sealing orifice plate, 172-Second sealing orifice plate, 20-Atomizer, 21-Burner head, 22-Natural gas and air via premixer, 41-Base tube, 42-Fin, 43-Longitudinal rib, 431-Rectangular longitudinal rib, 432-Wave longitudinal rib, 81-Upper header, 91-Lower header Detailed Implementation

[0034] The invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] This invention proposes a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube-coupled plate. It also introduces a tube-coupled plate premixed water-cooled combustion tube panel, integrating the premixer into the gas-fired steam boiler. This reduces the overall boiler volume, making the structure more compact. The mixed gas, after secondary rectification, forms a crossflow behind the tube-coupled plate premixed water-cooled combustion tube panel, allowing high-temperature flue gas to recirculate onto the water-cooled tube bundle. This effectively reduces flame temperature, shortens flame length, increases combustion stability, and further reduces nitrogen oxide emissions. Simultaneously, it employs slotted microchannel laminar flow enhanced heat transfer technology, significantly improving heat exchange efficiency. The advantages of this technology lie in its compact structure, simple process flow, short flow path, and low resistance. It not only reduces carbon emissions from raw materials and manufacturing processes but, more importantly, directly reduces electricity consumption for power generation, lowering operating carbon emissions and operating costs, truly achieving the lowest possible carbon emissions across the entire product supply chain.

[0036] like Figure 1a and Figure 1bAs shown, the boiler is vertically arranged and includes a blower 1, a burner 2, a tube-coupled plate premixed water-cooled combustion tube panel 3, a tube-coupled plate finned heat exchange tube bundle 4, a membrane wall downcomer tube panel 5, a spiral finned convection tube bundle 6, an energy-saving condensing tube bundle 7, an upper steam-water chamber 8, a lower water chamber 9, a boiler shell 10, a chimney 12, and a safety valve 14. Three rings of annular tubes are arranged radially along the boiler. The inner ring tube bundle consists of multiple "C"-shaped heat exchange tubes with a spacing greater than 5mm. The heat exchange tubes are welded together using flat steel, with two rows of radial holes on the flat steel. The heat exchange tubes are arranged vertically to form the tube-coupled plate premixed water-cooled combustion tube panel 3. The middle ring tube bundle includes multiple coupled finned tubes, which are arranged vertically to form a slotted channel tube-coupled plate finned heat exchange tube bundle 4. Multiple heat exchange tube bundles are arranged vertically, with flat steel welded and sealed between adjacent heat exchange tubes to form a membrane wall downcomer screen 5, which is annular. Three rows of staggered, vertically arranged spiral finned convection tube bundles 6 are arranged in the middle and rear sections of the boiler. Four rows of energy-saving condensing tube bundles 7, each formed by bending a single water pipe, are arranged laterally at the tail end of the boiler. The upper and lower ends of the membrane wall downcomer screen 5, the tube-coupled plate-fin enhanced heat exchange tube bundle 4, and the first row of spiral finned convection tube bundles 6 extend into the bottom and top of the upper steam-water chamber 8 and the lower water chamber 9, respectively. The base tubes of the second and third rows of spiral finned convection tube bundles 6 are bent into a "C" shape. The upper and lower ends of the second and third rows of spiral finned convection tube bundles 6 extend from the outer sides of the upper steam-water chamber 8 and the lower water chamber 9, respectively. The lower water chamber 9 has its upper and lower ends extending from the inner sides of the upper steam-water chamber 8 and lower water chamber 9, respectively. The annular space between the premixed water-cooled combustion tube panel 3 and the tube-coupled plate finned heat exchange tube bundle 4 forms the furnace. The space between the tube-coupled plate finned heat exchange tube bundle 4 and the membrane wall downcomer tube panel 5 forms a flue gas passage. The upper steam-water chamber 8 and lower water chamber 9 are annular headers. The lower water chamber 9 has a water inlet on its outer side and a sealing plate 18 at its bottom. The upper steam-water chamber 8 has a safety valve 14, a steam outlet, a pressure gauge, a pressure sensor, and a burner mounting panel 16 at its top. It also has a water level gauge interface on its side. Below the steam outlet, two... An "L"-shaped folding plate 19; a sealing perforated plate is welded to the bottom surface of the upper steam-water chamber 8 and the top surface of the lower water chamber 9; the top of the boiler shell 10 is connected to the bottom of the upper steam-water chamber 8 and the outer edge of the top of the lower water chamber 9, surrounding all heat exchange tubes; the tail of the boiler is connected to a square-to-round structure 11 flue shell, the tail of the square-to-round structure 11 flue shell is connected to a chimney 12, and a condensate drain hole 15 is opened below it; the burner 2 is fixed on the burner mounting panel 16, which is located at the center of the top surface of the upper steam-water chamber 8; a cylindrical flow equalization perforated plate 13 is welded below the burner mounting panel 16; the boiler shell 10 of the present invention is lined with heat insulation material between the membrane wall downcomer screen 5 to greatly reduce the heat loss of the boiler.

[0037] like Figure 1bAs shown, after natural gas and air are fully mixed by the premixer 22, under the constraint of the first sealing orifice plate 171 and the burner mounting panel 16, the mixed gas first passes through the holes of the flow equalization orifice plate 13 radially, and then passes through the holes of the flat steel of the premixed water-cooled combustion tube screen 3 before being ignited and burned. The high-temperature flue gas formed after combustion undergoes laminar flow enhanced heat exchange along the gap between the tube coupling plate fin enhanced heat exchange tube bundle 4. After the flue gas heat exchange is completed, the temperature decreases and it enters the flue gas channel formed by the annular space between the tube coupling plate fin enhanced heat exchange tube bundle 4 and the membrane wall downcomer tube screen 5, moving towards the tail of the boiler. Under the constraint of the flat steel between the tube bundle of the membrane wall downcomer tube screen 5 and the tube coupling plate fin enhanced heat exchange tube bundle 4 at the tail, the flue gas scours the spiral fin convection tube bundle 6. The cooled flue gas continues to flow backward and scours the energy-saving condenser tube bundle 7. The flue gas temperature further decreases and condensation occurs. After condensation, it is discharged into the atmosphere through the chimney 12. The generated condensate is discharged through the condensate discharge hole 15.

[0038] like Figure 1c , Figure 1d and Figure 5 As shown, 20°C boiler feedwater enters the inlet below the energy-saving condenser and flows forward along the energy-saving condenser tube bundle 7. When it reaches the other side of the energy-saving condenser, it turns 180° horizontally and continues to flow along the energy-saving condenser tube bundle 7. When it reaches the inlet side, it turns 180° upward again. It flows meanderingly along the pipeline and finally gets 90°C boiler feedwater from the outlet above the energy-saving condenser. It then enters the lower water chamber 9 from the outlet header 24. After entering the lower water chamber 9, the high-temperature boiler feedwater is evenly distributed in the tube coupling plate premixed water-cooled combustion tube panel 3, the tube coupling plate finned heat exchange tube bundle 4, the membrane wall downcomer tube panel 5, and the spiral finned convection tube bundle 6. While flowing upward, the boiler feedwater absorbs heat and vaporizes into water vapor. After entering the upper steam-water chamber 8, the steam is constrained by the "L"-shaped baffle 19 and turns 90° four times before passing through the steam outlet above the upper steam-water chamber 8 to output saturated steam.

[0039] like Figure 2a , Figure 2b Figure 2c , Figure 2d and Figure 2e As shown, the tube-coupled plate premixed water-cooled combustion tube panel 3 includes multiple "C"-shaped heat exchange tubes. The heat exchange tubes are welded together with flat steel. Two through holes are opened on the flat steel at a set angle, either sequentially or staggered. The shape of the through holes can be circular, rhomboid, rectangular, or oblong. The heat exchange tubes are arranged vertically to form the tube-coupled plate premixed water-cooled combustion tube panel 3. The mixed gas passes through the holes on both sides of a single heat exchange tube to form an interlaced airflow, which allows the high-temperature flue gas after ignition and combustion to flow back to the water-cooled tube bundle, further reducing the flame temperature and flame length, thereby reducing NO. x concentration.

[0040] like Figures 3a to 3dAs shown, the tube-coupled plate-finned heat exchange tube bundle 4 adopts folded finned tubes, which include a base tube 41 and fins 42. The base tube 41 is a necked-down tube, which means that the diameter of the tube is reduced at both ends where it connects to the tube sheet. The fins 42 include interconnected folded fins and front fins. The front fins are connected to the tube, and there is a bend angle between the folded fins and the front fins. The folded fins are suspended in the air. The fins 42 are bent at a certain angle so that the folded fins of the previous tube and the front fins of the next tube are parallel. The outer side of the front fins and the inner side of the folded fins are formed by laser cutting, stamping, or etching to form rectangular longitudinal ribs 431 or wavy longitudinal ribs 432, so that the folded fins of the previous tube bundle and the front fins of the next tube bundle are parallel. A 0.2–1 mm wide gap channel is formed between the front fins of the subsequent tube bundle; the thickness of the fin 42 is greatest at the starting end and gradually decreases along the airflow direction, while the thickness of the folded fin remains unchanged along the airflow direction, in order to improve the strength and stability of the fin; the base tube 41 and the fin 42 are beveled inside and out, and TIG welding, MIG welding or laser welding are used to form a jet, turbulence and laminar flow enhanced heat transfer channel, or the space between the inner side of the fin and the base tube is filled after welding to form a laminar flow enhanced heat transfer channel; the base tube 41 uses the materials specified in the gas boiler standard, and the fin 42 is not a pressure-bearing component, and uses a material with a thermal conductivity of not less than 200 W / m·K;

[0041] like Figures 3e to 3g As shown, the longitudinal ribs 43 can also be formed by laser cutting, stamping and etching processes to form intersecting ribs and longitudinal ribs. The longitudinal ribs 43 on the outer surface of the forewing and the inner surface of the folded wing combine to form a "labyrinth-like flue gas channel", which allows more heat from the flue gas to be transferred to the water in the tube bundle, thus enhancing heat transfer.

[0042] like Figure 4 As shown, the membrane wall downcomer screen 5 uses necked light tubes, which are arranged along an arc, and flat steel is welded between adjacent heat exchange tubes for sealing.

[0043] like Figure 5 As shown, refractory mud is filled in the annular space formed by the burner mounting panel 16, the flow equalization orifice plate 13, the first sealing orifice plate 171 and the inner side of the upper steam-water chamber 8 to minimize the boiler heat loss.

[0044] like Figure 6 As shown, refractory mortar is filled in the cylindrical space formed between the second sealing plate 172 above the lower water chamber 9 and the sealing plate 18 below it to minimize boiler heat loss.

[0045] like Figure 5 , Figure 6 and Figure 7As shown, the flow equalization orifice plate 13 is welded below the burner mounting panel 16, ending at the second sealing orifice plate 172 above the lower water chamber 9. The starting drilling position is below the first sealing orifice plate 171 of the upper steam-water chamber 8. To achieve better flow rectification, the thickness of the flow equalization orifice plate 13 is approximately 10-15 mm. Figure 7 In the diagram, hole a is circular, hole b is rhomboid, and hole c is oblong. The shape of the hole can also be rectangular.

[0046] like Figure 8 As shown, the membrane wall downcomer screen 5 can also be arranged along the vortex line to form an isobaric flue gas channel with an ever-increasing width, making the flue gas distribution more uniform and the flue gas flow smoother.

[0047] like Figure 9a , Figure 9b and Figure 9cAs shown, the gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a pipe-coupled plate can also adopt a type where the burner 2 can be detachably output superheated steam. The difference when using this scheme is that an upper header 81 and a lower header 91 are added. The upper header 81 has an annular structure, and its upper and lower surfaces are flush with the upper and lower surfaces of the upper steam-water chamber 8, respectively. The lower header 91 also has an annular structure, and its upper and lower surfaces are flush with the lower water chamber 9, respectively. The outer surfaces of the upper header 81 and the lower header 91 are flush with the lower water chamber 9 of the upper steam-water chamber 8. The inner surface of the chamber is tightly fitted. The base tube of the premixed water-cooled combustion tube panel 3 of the tube coupling plate adopts a vertical necked tube. The upper and lower ends of the base tube extend into the bottom and top of the upper header 81 and the lower header 91, respectively. The upper steam-water chamber has a saturated steam outlet, a safety valve 14, a pressure gauge, and a pressure sensor. There is a water level gauge interface on the side. Below the steam outlet, the two "L"-shaped baffles 19 are no longer set on the inner side of the upper surface of the upper steam-water chamber 8. The top of the upper header 81 has a burner mounting panel and a superheated steam outlet. The lower header 91 contains an atomizer. Boiler feedwater at 20°C is introduced into the inlet below the energy-saving condenser and flows forward along the energy-saving condenser tube bundle 7. Upon reaching the other side of the energy-saving condenser, it turns horizontally by 180° and continues flowing along the energy-saving condenser tube bundle 7. Upon reaching the inlet side, it turns upward by 180° again, thus meandering along the pipeline. Finally, it reaches boiler feedwater at approximately 90°C at the outlet above the energy-saving condenser. The high-temperature boiler feedwater then flows through a pipe into the lower water chamber 9. After entering the lower water chamber 9, the high-temperature boiler feedwater is evenly distributed on the tube coupling plate premixed water-cooled combustion tube panel 3. In the tube coupling plate finned heat exchange tube bundle 4, membrane wall downcomer tube panel 5, and spiral finned convection tube bundle 6, the boiler feedwater absorbs heat and vaporizes into water vapor as it flows upward. The saturated steam generated in the upper steam-water chamber 8 is then piped into the lower header 91. At this time, the atomizer 20 vaporizes the water from the lower water chamber 9, increasing the water content of the saturated steam. The saturated steam with increased water content is evenly distributed in each tube coupling plate premixed water-cooled combustion tube bundle 3 and then flows upward. After being heated, it becomes superheated steam and is discharged from the superheated steam outlet.

[0048] like Figure 9d As shown, the gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a pipe coupling plate can also adopt a type where the burner 2 can be detached as a whole to output saturated steam. The upper steam-water chamber 8 and the upper header 81 are connected by an elbow, and the lower water chamber 9 and the lower header 91 are also connected by an elbow. The steam generated by the upper header 81 enters the upper steam-water chamber 8 through the elbow, and the saturated steam generated is discharged from the steam outlet above the upper steam-water chamber. No atomizer 20 is installed in the lower header 91.

[0049] like Figure 10 As shown, the atomizer 20 is annular and is placed in the lower header 91 to atomize the boiler feedwater from the lower water chamber 9, thereby increasing the humidity of the saturated steam.

[0050] In summary, this invention provides a gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube-coupled plate. It proposes a tube-coupled plate premixed water-cooled combustion tube panel. The heat exchange tube bundle of the water-cooled combustion tube panel uses bare tubes bent into "C" shapes. Flat steel is welded to the middle of adjacent "C"-shaped bare tubes and has two rows of radial holes. This allows the mixed gas to form a staggered flow on the outside of the flat steel, which improves flame stability, reduces flame length, and lowers flame temperature after ignition and combustion, resulting in nitrogen oxide emissions from the gas burner being less than 30 mg / m³. 3 The combustion efficiency is greater than 99.8%, reducing combustion resistance by 40% compared to traditional domestic burners and effectively reducing carbon emissions by 10% to 30% or more. A highly efficient "laminar flow enhancement" heat transfer element is proposed: a folded-fin tube. The heating surface uses trapezoidal straight fins bent into folded fins. The fins are bent at a certain angle so that the folded fins of the previous tube bundle are parallel to the front fins of the next tube bundle. Longitudinal ribs are welded to the outer side of the front fins and the inner side of the folded fins, forming a 0.2-1mm wide gap channel between the folded fins of the previous tube bundle and the front fins of the next tube bundle. The gap channel formed between adjacent coupled finned evaporative heat exchange tube bundles can eliminate the central high-temperature zone in the traditional heat exchange process. When the flue gas passes through the gap channel, the entire channel is in a boundary layer region with strong heat and mass transfer, and the heat transfer coefficient can reach 130W / m². 2 ·℃ or above.

Claims

1. A gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via a tube-coupled plate, characterized in that, The boiler adopts a vertical arrangement, including a burner (2), a tube-coupled plate premixed water-cooled combustion tube panel (3), a tube-coupled plate finned heat exchange tube bundle (4), a membrane wall downcomer tube panel (5), a spiral finned convection tube bundle (6), an energy-saving condenser tube bundle (7), an upper steam-water chamber (8), a lower water chamber (9), a boiler shell (10), and a chimney (12). The tube-coupled plate premixed water-cooled combustion tube panel (3), the tube-coupled plate finned heat exchange tube bundle (4), and the membrane wall downcomer tube panel (5) are arranged concentrically from the inside to the outside. The annular space between the tube screen (3) and the tube coupling plate-fin enhanced heat exchange tube bundle (4) is the furnace. The space between the tube coupling plate-fin enhanced heat exchange tube bundle (4) and the membrane wall downcomer tube screen (5) forms a flue gas passage. The spiral fin convection tube bundle (6), the energy-saving condenser tube bundle (7), and the chimney (12) are arranged on one side of the boiler shell (10) along the flue gas flow direction. The upper steam-water chamber (8) and the lower water chamber (9) are annular headers. The tube coupling plate premixed water-cooled combustion tube screen (3), the tube coupling plate-fin enhanced heat exchange tube bundle (4), and the membrane wall downcomer tube screen (5) form a flue gas passage. The tube panel (5) and the spiral finned convection tube bundle (6) connect the upper steam-water chamber (8) and the lower water chamber (9); the tube-coupled plate-finned heat exchange tube bundle (4) is provided with a slotted flue gas passage; the burner (2) is located at the top center; the tube-coupled plate-finned heat exchange tube bundle (4) adopts folded finned tubes, which include a base tube (41) and fins (42). The base tube (41) adopts a necked bare tube, and the fins (42) include interconnected folded fins and front fins. The front fin is connected to the bare tube, and there is a bend angle between the folded fin and the front fin. The fins are suspended in the air, and longitudinal ribs (43) are provided on the surface of the fins (42); the fins (42) are bent at a set angle so that the folded fins of the previous tube and the front fins of the next tube are parallel. The thickness of the fins (42) is the largest at the beginning and gradually decreases along the airflow direction. The thickness of the folded fins remains unchanged along the airflow direction. A gap channel is formed between the folded fins of the previous tube and the front fins of the next tube; the tube coupling plate premixed water-cooled combustion tube screen (3) includes multiple "C"-shaped heat exchange tubes. Flat steel is used to weld between adjacent heat exchange tubes. Through holes are opened on the flat steel in a set angle, either sequentially or staggeredly.

2. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate as described in claim 1, characterized in that, The spiral fin convection tube bundle (6) is arranged in three rows. The upper and lower ends of the first row of spiral fin convection tube bundle (6) extend into the bottom and top of the upper steam-water chamber (8) and the lower water chamber (9), respectively. The base tubes of the second and third rows of spiral fin convection tube bundle (6) are bent into a "C" shape. The upper and lower ends of the second and third rows of spiral fin convection tube bundle (6) extend into the upper steam-water chamber (8) and the lower water chamber (9) from the outer side of the upper steam-water chamber (8) and the lower water chamber (9), respectively. The upper and lower ends of the tube coupling plate premixed water-cooled combustion tube screen (3) extend into the upper steam-water chamber (8) and the lower water chamber (9) from the inner side of the upper steam-water chamber (8) and the lower water chamber (9), respectively.

3. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate as described in claim 1, characterized in that, The gap between the folded fin of the front tube and the front fin of the rear tube is 0.2 to 1 mm wide; the base tube (41) and the fin (42) are beveled inside and out and connected by TIG welding, MIG welding or laser welding. The base tube (41) is made of the material specified in the standard for gas boilers, and the fin (42) is made of the material with a thermal conductivity of not less than 200 W / (m·K).

4. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate as described in claim 3, characterized in that, The longitudinal ribs (43) include rectangular longitudinal ribs (431) or wavy longitudinal ribs (432) provided on the outer surface of the forewing and the inner surface of the folded wing. The rectangular longitudinal ribs (431) and the wavy longitudinal ribs (432) are formed by laser cutting, stamping or etching processes. The longitudinal ribs (43) are either cross-ribs or longitudinally intersecting ribs. The cross-ribs are cross-ribs with alternating flow and columnar shape. The longitudinal ribs (43) on the outer surface of the forewing and the inner surface of the folded wing combine to form a "maze-like flue gas channel". The cross-ribs and longitudinally intersecting ribs are formed by laser cutting, stamping and etching processes.

5. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate as described in claim 1, characterized in that, The through hole is circular, rhomboid, rectangular or oblong, and the heat exchange tubes are arranged vertically to form a tube coupling plate premixed water-cooled combustion tube screen (3); a flow equalization plate (13) is provided on the inner side of the tube coupling plate premixed water-cooled combustion tube screen (3). The flow equalization plate (13) is cylindrical and ends at the sealing plate at the top of the lower water chamber (9). The starting drilling position is below the sealing plate of the upper steam-water chamber (8). The thickness of the flow equalization plate (13) is 10-15mm.

6. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate as described in claim 5, characterized in that, The boiler shell (10) and the membrane wall downcomer screen (5) are lined with thermal insulation material. The annular space formed between the inner side of the upper steam and water chamber (8) and the flow equalization plate (13) is filled with refractory mud. The columnar space enclosed by the inner side of the lower water chamber (9) is filled with refractory mud.

7. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate according to claim 1, characterized in that, The upper steam chamber (8) has two "L"-shaped baffles (19) on the inner side of its upper surface. The two "L"-shaped baffles (19) are arranged opposite each other. The width and height of one "L"-shaped baffle (19) are smaller than the other "L"-shaped baffle (19). The lower water chamber (9) has a water inlet on its outer side and a sealing plate (18) at the bottom. The upper steam chamber (8) has a safety valve (14), a steam outlet, a pressure gauge and a pressure sensor at the top, and a water level gauge interface on its side.

8. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate according to claim 1, characterized in that, The top of the boiler shell (10) is connected to the bottom of the upper steam-water chamber (8) and the top outer edge of the lower water chamber (9), surrounding the spiral fin convection tube bundle (6) and the energy-saving condenser tube bundle (7). The tail of the boiler is connected to the flue shell of the square-to-round structure (11), and the tail of the flue shell of the square-to-round structure (11) is connected to the chimney (12), with a condensate drain hole (15) below. A burner mounting panel (16) is set at the top center of the upper steam-water chamber (8), and the burner (2) is fixed on the burner mounting panel (16). The burner (2) is connected to the blower (1), and the flow equalization plate (13) is welded to the bottom of the burner mounting panel (16).

9. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange via tube coupling plate according to claim 1, characterized in that, The upper steam chamber (8) is equipped with an upper header (81) in the inner ring, and the lower water chamber (9) is equipped with a lower header (91) in the inner ring. The base tube of the premixed water-cooled combustion tube screen (3) of the pipe coupling plate adopts a vertical necked smooth tube. The upper end and lower end of the base tube are respectively inserted into the bottom and top of the upper header (81) and the lower header (91). The upper surface of the upper steam chamber (8) is a smooth plate.

10. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange according to claim 9, characterized in that, The lower header (91) contains an atomizer (20), and the inlet of the atomizer (20) is connected to the lower water chamber (9).

11. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange according to claim 9, characterized in that, The upper steam chamber (8) and the upper header (81) are connected by an elbow, and the lower water chamber (9) and the lower header (91) are connected by an elbow.

12. The gas-fired steam boiler with premixed water-cooled combustion and enhanced heat exchange according to claim 1, characterized in that, The membrane wall downcomer screen (5) includes multiple heat exchange tubes, multiple heat exchange tube bundles are arranged vertically, and flat steel is used to weld and seal between adjacent heat exchange tubes. The membrane wall downcomer screen (5) is arranged along the vortex line to form an equal pressure flue gas channel with gradually increasing width.

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