A gas condensing boiler with large turndown ratio, water-cooled premixed combustion and high-intensity heat exchange

Abstract

A gas condensing boiler with large regulation ratio, water-cooled premixed combustion and high-intensity heat exchange comprises a burner and a heat exchanger. The full premixed burner installed at the center of the boiler top plate comprises a booster fan, a premixing chamber and a water-cooled combustion head. The flame-stabilizing tube and the anti-backfire column of the water-cooled combustion head can realize large regulation ratio, water-cooled premixed combustion. The heat exchanger comprises a circle of water-cooled walls and a circle or several circles of fins, which are evenly arranged circumferentially through bent folded finned tubes. The blower sends air into the premixing chamber and fully mixes it with the gas into the cavity in the orifice plate of the combustion head, flows out of the fire hole and sprays out through the narrow gap between the water-cooled tubes distributed in the circumferential direction, ignites after the flame-stabilizing tube, burns evenly in the circumferential and axial directions and radiates heat to the inner tube ring. The flue gas flushes the base tubes and fins of the inner and outer ring finned tubes in turn, strengthens heat exchange, flows downward into the dew receiving plate through the gap between the outer shell and the outer finned tube, and is discharged into the atmosphere from the flue gas outlet. The combustion load regulation ratio of the present invention is large, the heat exchange is compact, the nitrogen emission is low, and the thermal efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of integral condensing boilers, and in particular to a gas condensing boiler with large regulation ratio, water cooling, premixed combustion and high-intensity heat exchange. Background Art

[0002] At present, conventional commercial gas water heaters and other thermal power equipment have the problem of low utilization efficiency. On the one hand, it is necessary to continuously improve the combustion efficiency of natural gas, and on the other hand, it is necessary to further reduce the exhaust temperature of natural gas utilization equipment and improve the equipment conversion efficiency. The exhaust temperature of conventional natural gas hot water boilers is generally above 130°C, and that of steam boilers is above 200°C, sometimes even as high as 300°C. This temperature is much higher than the water dew point temperature of natural gas flue gas (usually 55-60°C). The exhaust not only takes away a large amount of sensible heat of the flue gas, but more importantly, the latent heat of water vapor in the flue gas cannot be fully utilized. Reducing the boiler exhaust temperature is very important for improving the efficiency of natural gas boilers and reducing operating costs.

[0003] Condensing boilers use efficient full premixed combustion technology to effectively reduce the excess air coefficient of combustion, improve the combustion efficiency of natural gas, and reduce the generation and emission of pollutants such as NOx. At the same time, they use flue gas deep cooling technology to reduce the exhaust temperature of heat energy utilization equipment to below the flue gas dew point temperature (or water dew point). It can not only fully absorb the sensible heat of flue gas, but also utilize the condensation and heat release of water vapor generated during natural gas combustion, greatly improving the conversion efficiency of natural gas energy in heat energy utilization equipment and saving energy. Therefore, the development and application of gas condensing hot water boilers is one of the effective ways to reduce environmental pollution and efficiently utilize gas. At present, the structural forms of condensing boilers on the market mainly include split type and integral type. The former is to add a condensing section heat exchanger after a conventional boiler, with a low condensation rate and a small improvement in the overall thermal efficiency of the boiler; the latter is to design a conventional boiler and a condensing heat exchanger as an integral structure. The integral condensing boilers currently launched on the market mainly include cast aluminum silicon magnesium modular commercial gas condensing hot water boilers and commercial gas stainless steel coil condensing hot water boilers. Although cast aluminum silicon magnesium modular commercial gas condensing water heaters are highly efficient and compact in structure, the molds and materials are expensive, domestic production capacity is extremely limited, and the core technology is controlled by foreign countries; commercial gas stainless steel coil condensing water heaters are large and bulky, and the coil process is complex and costly. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a gas condensing boiler with high-intensity heat exchange of water-cooled premixed combustion and large adjustment ratio. The radiation-convection heat exchanger of the boiler is composed of folded fin tubes with bent fins. The combustion chamber composed of folded fin tubes is conducive to giving full play to the advantages of strong radiation heat exchange capacity of the full premixed burner. At the same time, the flue heat exchange area between adjacent folded fin tubes is larger than that of the light tube, and it is simpler to manufacture than the corn-shaped straight tube. The fins bent on both sides make the high-temperature flue gas first flush the base tube and then be diverted and cooled on both sides. The water in the base tube strongly cools the flue gas, and the heat exchange coefficient is large. The boiler has a simple structure, low cost and high thermal efficiency. When the return water temperature is 30°C, the boiler thermal efficiency can reach more than 106%.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:

[0006] A gas condensing boiler with large adjustment ratio, water-cooled premixed combustion and high-intensity heat exchange, comprises a shell 3, a heat exchanger 1 of the gas condensing boiler in the shell 3 is composed of a circle of water-cooled wall tubes 1-6 and one or more circles of annularly arranged folded fin tubes 1-1 outside the water-cooled wall tubes 1-6, the folded fin tubes 1-1 are fin tubes with fins subjected to bending treatment, the water-cooled wall tubes 1-6 are surrounded to form a radiation heat exchange space in the furnace of the gas condensing boiler, and the radiation heat exchange space in the furnace is a full premixed burner head 2 composed of a perforated plate 2-2, an anti-flashback column 2-7, a water-cooled tube 2-1 and a flame stabilizing tube 2-6 from the inside to the outside; the folded fin tubes 1-1 are fin tubes with fins subjected to bending treatment, and the water-cooled wall tubes 1-6 are surrounded to form a radiation heat exchange space in the furnace of the gas condensing boiler, and the radiation heat exchange space in the furnace is a full premixed burner head 2 composed of a perforated plate 2-2, an anti-flashback column 2-7, a water-cooled tube 2-1 and a flame stabilizing tube 2-6 from the inside to the outside; , water-cooled wall tubes 1-6, water-cooled tubes 2-1 and flame-stabilizing tubes 2-6 are arranged between the water inlet header 1-2, the water outlet header 1-4 and the lower header 1-3; the full premixed burner is installed on the outer shell 3, and the head 2 of the full premixed burner penetrates into the radiation heat exchange space in the furnace to burn and release heat, and the flue gas flows through the gaps between the water-cooled wall tubes 1-6 and one or more circles of folded fin tubes 1-1, and enters the dew receiving tray 3-2 at the bottom of the condensing boiler through the gaps between the outer shell 3 and the outer circle of folded fin tubes 1-1-1, and flows out from the flue gas outlet 3-4 at the bottom of the dew receiving tray 3-2; the condensed water generated by the flue gas flows out from the drain outlet 3-3 at the bottom of the dew receiving tray 3-2.

[0007] The folded fin tube 1-1 is a spiral fin tube composed of a base tube and an additional spiral fin, or a round fin tube composed of a base tube and an additional flat fin; the absolute value of the angle between the folded fin surface of the fin bending part and the original fin plane is 0° to 90°, and each circle of fins has two folded fin surfaces with symmetrical folds, one side of the folded fin surface is bent upward, that is, the angle with the original fin plane is 0° to 90°, and the other side of the folded fin surface is bent downward, that is, the angle with the original fin plane is 0° to -90°, and the angle between the two folds of the fin bending part is 0° to 180°. When arranged in the boiler, the adjacent folded fin surfaces are arranged in a boiler. The fins of the folded fin tube 1-1 are arranged alternately, and the vertices of the two fold lines are the windward surfaces; the two ends of the base tube of the folded fin tube 1-1 are necked, and the size of the base tube after necking is smaller. A circle of circular iron blocks is welded near the end to compress the sealing gaskets of the folded fin tube 1-1 and the water inlet header 1-2, the lower header 1-3 and the water outlet header 1-4; the folded fin tube 1-1 includes an outer circle folded fin tube 1-1-1 and an inner circle folded fin tube 1-1-2, which have the same structure, and the specific size should be different according to the circumferential position where they are arranged and the size of the base tube and the fin.

[0008] One end of the outer ring folded fin tube 1-1-1, the inner ring folded fin tube 1-1-2, the water-cooled wall tube 1-6, the water-cooled tube 2-1 and the flame-stabilizing tube 2-6 is connected to the lower header 1-3 by plugging or welding, the other end of the outer ring folded fin tube 1-1-1 is connected to the water inlet header 1-2 by plugging or welding, and the other ends of the inner ring folded fin tube 1-1-2, the water-cooled wall tube 1-6, the water-cooled tube 2-1 and the flame-stabilizing tube 2-6 are connected to the water outlet header 1-4 by plugging or welding, countersunk holes are provided at the connecting through holes to place sealing gaskets to ensure the sealing of the water channel, and the connection is covered with refractory material 3-5; if it is a plug-in connection, there are three in the cylindrical tube bundle composed of the outer ring folded fin tube 1-1-1 One or more than three folded fin tubes are fastened folded fin tubes 1-1-3, and the fastened folded fin tubes 1-1-3 are evenly arranged along the circumferential direction; the structure of the heated part of the fastened folded fin tubes 1-1-3 is consistent with that of the folded fin tubes 1-1, and the pipe section after necking passes through the water inlet header 1-2 and the lower header 1-3 and is fixed by the fastening nut 1-5, and the upper and lower bottom surfaces of the base tube are sealed, and the two ends of the base tube outside the water inlet header 1-2 and the lower header 1-3 are provided with threads, and the base tube section inside the water inlet header 1-2 and the lower header 1-3 is provided with a plurality of flow holes to ensure the normal flow of feed water in the fastened folded fin tubes 1-1-3; if it is a welding connection, the fastened folded fin tubes 1-1-3 are not required in the outer ring tube bundle of the heat exchanger;

[0009] The water inlet header 1-2, the water outlet header 1-4 and the lower header 1-3 are all formed by welding two upper and lower disc surfaces with the inner and outer wall surfaces, wherein there is a circular wall surface between the water inlet header 1-2 and the water outlet header 1-4 to completely separate them into two independent spaces; at the connection with the fastened folded fin tube 1-1-3, in addition to the connection holes opened on the wall surfaces of the water outlet header 1-4 and the lower header 1-3 close to the furnace side, connection holes are also opened on the wall surface away from the furnace side, and countersunk holes are arranged on the outside to place sealing gaskets, so as to ensure the sealing of the water channel under the extrusion of the fastening nut 1-5.

[0010] The water inlet header 1-2 is provided with a water inlet 1-2-1, and the water outlet header 1-4 is provided with a water outlet 1-4-1; the feed water enters the water inlet header 1-2 through the water inlet 1-2-1, and enters the lower header 1-3 through the outer circle folded fin tube 1-1-1 and the fastened folded fin tube 1-1-3. The lower header 1-3 supplies water to the inner circle folded fin tube 1-1-2, the water-cooled wall tube 1-6, the water-cooled tube 2-1 and the flame-stabilizing tube 2-6 at the same time, and the hot water is collected in the water outlet header 1-4 and flows out from the water outlet 1-4-1.

[0011] The shell 3 is divided into an upper and lower end cover, which are tightly connected by fastening screws 3-1; the space between the upper and lower end covers is filled with sealing material, and the shell is sealed by a plurality of fastening screws 3-1 arranged equidistantly along the circumference; when the furnace is shut down, the shell 3 is disassembled, and the fastening nuts 1-5 at both ends of the fastened folded fin tubes 1-1-3 are loosened, that is, the outer circle folded fin tubes 1-1-1, the inner circle folded fin tubes 1-1-2, the fastened folded fin tubes 1-1-3, the water-cooled wall tubes 1-6, the water-cooled tubes 2-1, the flame-stabilizing tubes 2-6, the water inlet header 1-2, the water outlet header 1-4 and the lower header 1-3 are disassembled, thereby greatly reducing the welding workload of the boiler.

[0012] The full premix burner is placed on the top or bottom of the shell 3. The full premix burner is composed of a burner head 2, a premix chamber 2-3 and a booster fan 2-4 connected in sequence. The premix chamber 2-3 is a cylindrical or rectangular space. A plurality of gas mixing plates 2-3-1 are arranged inside the space. A symmetrical gas header 2-3-2 is arranged on the periphery. A gas inlet 2-5 is arranged on the side of the gas header 2-3-2. A gas outlet hole 2-3-3 is opened on the gas mixing plate 2-3-1. Swirl blades are added downstream of the premix chamber 2-3, that is, below the gas mixing plate 2-3-1 to enhance the mixing effect. The air enters the premixing chamber 2-3 through the booster fan 2-4, and is fully mixed with the gas that enters the premixing chamber 2-3 through the gas inlet 2-5 and the gas mixing plate 2-3-1 in sequence. In the downstream of the premixing chamber 2-3, the air passes through the gas mixing plate 2-3-1 and then passes through the swirl blades to enhance the mixing effect. The mixed gas then enters the cylindrical space formed by the orifice plate 2-2. The mixed gas flows into the gap of the water-cooling tube 2-1 through the fire hole 2-2-1 opened on the orifice plate 2-2, and then sprays to the flame stabilizing tube 2-6 after passing through the water-cooling tube 2-1. After being disturbed by the flame stabilizing tube 2-6, it enters the furnace and burns.

[0013] The water-cooling tube 2-1 is a bare tube. Multiple water-cooling tubes 2-1 are closely arranged in a circle to form a circle of water-cooling tube bundles. Anti-flashback columns 2-7 are arranged near the inner side of the circle in the gaps between the water-cooling tubes 2-1, and flame-stabilizing tubes 2-6 are arranged near the outer side of the circle in the gaps. The flame-stabilizing tubes 2-6 are bare tubes, finned tubes, or folded finned tubes.

[0014] A plurality of gas mixing plates 2-3-1 are welded on the inner walls of both sides of the gas header 2-3-2. The gas mixing plates 2-3-1 on the same side are arranged in parallel. The gas mixing plates 2-3-1 on both sides are independent of each other and arranged relative to each other or staggered. The gas mixing plates 2-3-1 are circular or hexagonal, rectangular or oval straight pipes with a straight section in the middle. A plurality of rows of sequential or staggered gas outlet holes 2-3-3 are opened on the side of the straight section. Each gas outlet hole 2-3-3 is shaped as a conical protrusion, a triangular protrusion, a semi-circular protrusion, or a conical protrusion arranged upstream. Three-dimensional holes with circular protrusions, diamond-shaped protrusions, rectangular protrusions, hemispherical protrusions or spherical protrusions, or circular, triangular, diamond-shaped, semicircular, elliptical, trapezoidal or rectangular plane outflow holes arranged without protrusions upstream and perpendicular to the air flow direction, or a combination of the above three-dimensional holes and plane outflow holes; air flows into the premixing chamber 2-3 and is divided into multiple thin airflows by the mixing sheet 2-3-1. When the airflow flows through the protrusions, a low-pressure area is formed at the gas outflow hole 2-3-3, so that the gas and air are evenly mixed in the low-pressure area.

[0015] The anti-backfire column 2-7 is a solid column with a triangular or arc-edged triangular or hump-shaped cross section, and its boundaries are tangent to the inner orifice plate 2-2 and the two outer water-cooling tubes 2-1, respectively, so that the triangular gap between the orifice plate 2-2 and the two adjacent water-cooling tubes 2-1 is filled into two arc-shaped narrow channels to increase the narrow gap length of the cold wall effect, thereby effectively preventing backfire;

[0016] The space between the anti-flashback columns 2-7 is the outlet of the fire hole 2-2-1 of the orifice plate 2-2. The mixed gas flows out from the fire hole 2-2-1 group, is diverted when encountering the water cooling tube 2-1, flows out through the narrow gap channel between the anti-flashback column 2-7 and the water cooling tube 2-1, merges with the mixed gas diverted from the adjacent fire hole group and sprays to the flame stabilizing tube 2-6, and burns after the flame stabilizing tube 2-6.

[0017] A cylindrical space is formed inside the plurality of anti-flashback columns 2-7, in which a perforated plate 2-2 is placed. The anti-flashback columns 2-7 and the perforated plate 2-2 fit tightly together, so that the mixed gas cannot flow out from the outlet of the fire hole 2-2-1 blocked by the anti-flashback columns 2-7.

[0018] The orifice plate 2-2 is provided with a plurality of rows of long slit-type, small hole-type, petal-type, or a combination of the above three types of fire holes 2-2-1, each row or each plurality of rows of fire holes having different areas, so that the fire holes are divided into two or more types of fire holes with different areas;

[0019] The portion of the fire hole 2-2-1 blocked by the anti-backfire column 2-7 is called a blocking hole, and the portion not blocked by the anti-backfire column 2-7 is called an outflow hole; the areas of the fire holes 2-2-1 in multiple groups of outflow hole regions are exactly the same, and the areas of the fire holes 2-2-1 in multiple groups of blocking hole regions are also exactly the same, while the areas of the fire holes 2-2-1 in the outflow hole region and the blocking hole region are different in size.

[0020] A plurality of said anti-tempering columns 2-7 are welded together at their upper and lower ends by a circular wall, and one or more positioning pins 2-7-1 are arranged on the outer side of the circular wall to ensure that the anti-tempering columns 2-7 are placed and fixed at the required angle;

[0021] The orifice plate 2-2 fits tightly with the multiple anti-backfire columns 2-7 and can be rotated manually or electrically controlled. By adjusting the angle of the rotating orifice plate 2-2, the area of ​​the fire hole 2-2-1 in the outflow hole area is changed; when the orifice plate 2-2 is rotated under the highest load condition, the area of ​​the fire hole 2-2-1 in the outflow hole area is maximized, and the outlet flow rate of the mixture fire hole is reduced. Under the joint action of the flame stabilizing tube 2-6, the maximum heat load of the burner is greatly increased; when the orifice plate 2-2 is rotated under the lowest load condition, the area of ​​the fire hole 2-2-1 in the outflow hole area is minimized, the outlet flow rate of the mixture fire hole is increased, and the minimum heat load of the burner is greatly reduced, thereby increasing the load adjustment range of the burner.

[0022] The gas-fired condensing boiler can also be used as a steam boiler, and the flue gas outlet of the gas-fired condensing boiler is additionally connected to an economizer;

[0023] The heat transfer medium in the gas condensing boiler is water or heat transfer oil.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The heat exchanger structure of the condensing boiler of the present invention adopts fin-bending folded-edge fin tubes to form a radiation-convection heating surface. The combustion chamber is compact and can fully absorb the radiation heat exchange of high-temperature flue gas. The bent fin flue flow effectively enhances the convection heat exchange between the flue gas and the base tube.

[0026] 2. The finned tube adopts folded fin tube, which increases the heat transfer coefficient between flue gas and folded fin tube compared with the traditional finned tube without folded fins; compared with the circular cross-section plain tube, it increases the convection heat transfer area between flue gas tubes, strengthens the heat transfer, and has a better heat transfer effect than the traditional finned tube and plain tube; compared with the corn kernel-shaped straight tube, it is simpler to manufacture and has lower cost.

[0027] 3. The inner and outer rings of the folded fin tube are concentrically arranged. The high-temperature flue gas flows through the inner and outer rings in turn through the combustion chamber. The inner tube ring cools the flue gas temperature by radiation and convection, and the outer ring tube condenses the flue gas for heat exchange, which has high thermal efficiency. At the same time, the fin tube is made of stainless steel or cast aluminum silicon alloy to effectively improve the oxidation resistance and corrosion resistance, and the smooth heat exchange surface can be automatically cleaned, which greatly extends the service life of the heat exchanger and makes maintenance easier.

[0028] 4. The water-cooled fully premixed burner adopted in the condensing boiler of the present invention has a short flame length and a strong radiation capacity compared with the traditional diffusion burner; compared with the traditional metal fiber burner, the risk of flashback can be eliminated due to the safety of the water-cooled cooling capacity and the structure of the narrow slit-type fire holes of the anti-flashback column and the orifice plate, and the minimum heat load of combustion can be greatly reduced by adjusting the coordination mode of the orifice plate and the anti-flashback column, so as to achieve safe, stable and efficient combustion, and can fully burn at an extremely low excess air coefficient, which not only reduces the heat loss of smoke exhaust, but also increases the condensation rate of water vapor in the smoke; a circle of flame-stabilizing tube bundles is arranged around the slit-type fire holes so that the mixed gas forms a reflux around the flame-stabilizing tubes, which can form an effective ignition source and stabilize the combustion.

[0029] 5. The mixer of the present invention mixes more evenly than the traditional mixer, and adopts the air stratification method to eliminate the air dense area and realize the complete mixing of air and gas.

[0030] 6. The present invention has the advantages of simple structure and simplified manufacturing process. The condensing heat exchanger does not require welding. At the same time, the laminar convection and condensation heat exchange on the flue gas side are enhanced, making the entire heat exchanger very compact. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of the gas condensing boiler of the present invention.

[0032] Figure 2 This is a schematic diagram of the tube bundle arrangement of the gas condensing boiler of the present invention.

[0033] Figure 3a This is a schematic diagram of the arrangement of the water-cooled tube burner of the present invention. Figure 3b It is a partially enlarged schematic diagram of the water-cooled tube burner of the present invention.

[0034] Figure 4a This is a schematic diagram of the anti-tempering column structure. Figure 4b is a schematic diagram of the orifice plate structure. Figure 4c Schematic diagram of the combination of anti-tempering column and orifice plate.

[0035] Figure 5a This is a schematic diagram of the orifice plate and anti-tempering column under high load. Figure 5b This is a schematic diagram of the orifice plate and anti-tempering column under medium load. Figure 5c Schematic diagram of the orifice plate and anti-tempering column under low load.

[0036] Figure 6 Schematic diagram of the folded fin tube structure.

[0037] Figure 7 It is a schematic diagram of the structure of the fastened folded fin tube of the present invention.

[0038] Figure 8a Isometric view of spiral fin tube folding treatment. Figure 8b This is the top view of the spiral fin tube folding process. Figure 8c This is a side view of the spiral fin tube folding process.

[0039] Figure 9a This is the isometric view of the folded fin treatment of a flat circular fin tube. Figure 9b This is a top view of the folded fin treatment of a flat circular fin tube. Fig.9c It is the side view of the flat circular fin tube after folding fins.

[0040] Fig.10a This is the isometric view of the mixing plate structure. Fig.10b It is the top cross-sectional view of the mixing plate structure. Fig.10c It is the left sectional view of the mixing plate structure.

[0041] Fig.11 The gas mixing plate of the present invention is a schematic diagram of the structure of a gas mixing plate unit. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0043] like Figure 1 and Figure 2 As shown, the present invention is a gas condensing boiler with large adjustment ratio, water-cooled premixed combustion and high-intensity heat exchange, comprising a shell 3, a heat exchanger 1 of the gas condensing boiler in the shell 3 is composed of a circle of water-cooled wall tubes 1-6 and one or more circles of annularly arranged folded fin tubes 1-1 outside the water-cooled wall tubes 1-6, the water-cooled wall tubes 1-6 surround the radiation heat exchange space in the furnace of the gas condensing boiler, the radiation heat exchange space in the furnace is a full premixed burner head 2 composed of a perforated plate 2-2, anti-backfire columns 2-7, water-cooled tubes 2-1 and flame stabilizing tubes 2-6; the full premixed burner is installed on the shell 3, and the full premixed burner head 2 goes deep into the radiation heat exchange space in the furnace to burn and release heat; air enters the premixing chamber 2-3 from the booster fan 2-4, and mixes with the mixed air in the premixing chamber 2-3 The gas coming out of the plate 2-3-1 is mixed, and the fully mixed gas enters the cylindrical cavity formed by the orifice plate 2-2, and is sprayed to the water-cooled tube 2-1 from the fire hole 2-2-1 in the outflow area of ​​the orifice plate 2-2, and a reflux area is formed behind the flame-stabilizing tube 2-6. The mixed gas is ignited at the periphery of the flame-stabilizing tube 2-6 and forms a stable ignition area, forming a stable ignition source. The flue gas generated by the combustion flows through the gap between the inner layer folded fin tube 1-1-2 and the outer layer folded fin tube 1-1-1, is fully cooled, and enters the dew tray 3-2 at the bottom of the condensing boiler through the gap between the outer shell 3 and the outer ring folded fin tube 1-1-1, and flows out from the flue gas outlet 3-4 at the bottom of the dew tray 3-2; the condensed water generated by the flue gas flows out from the drain port 3-3 at the bottom of the dew tray 3-2;

[0044] The feed water in the boiler enters the water inlet header 1-2 from the water inlet 1-2-1, is distributed to the water and flows downward, enters the lower header 1-3 through the outer circle folded fin tube 1-1-1 and the fastened folded fin tube 1-1-3, turns at the bottom of the lower header 1-3, flows upward through the inner circle folded fin tube 1-1-2, the water cooling tube 2-1 and the flame stabilizing tube 2-6 into the water outlet header 1-4, and the heated hot water flows out through the water outlet 1-4-1.

[0045] like Figure 3a and Figure 3bAs shown, the head 2 of the full premix burner of the present invention is composed of four parts: an orifice plate 2-2, an anti-flashback column 2-7, a water-cooling tube 2-1 and a flame-stabilizing tube 2-6. The orifice plate 2-2 is provided with a slit-type or round hole-type or petal-type or the above-mentioned combined fire hole. The fire hole slit width is extremely small, preferably less than 2 mm. The gap between the water-cooling tubes 2-1 and the gap between the water-cooling tube 2-1 and the anti-flashback column 2-7 are also not greater than 2 mm. After the mixed gas flows out from the fire hole 2-2-1 in the outflow area of ​​the orifice plate, it passes through the gap channel between the water-cooling tube 2-1 and the anti-flashback column 2-7, the gap channel between the water-cooling tube 2-1 and the gap channel between the water-cooling tube 2-1 and the flame-stabilizing tube 2-6 in sequence and then burns. The flame-stabilizing tube 2-6 causes the mixed gas to reflux after flowing through it, effectively increasing the flameout limit and the maximum heat load of the burner. The water-cooling tube 2-1 and the anti-flashback column 2-7 can increase the distance of the cold wall effect and effectively reduce the risk of flashback.

[0046] like Figure 4a , Figure 4b and Figure 4c As shown, the ends of several anti-backfire columns 2-7 are welded on a circular wall surface, and several positioning pins 2-7-1 are arranged on the outer side of the circular wall surface to fix the position of the anti-backfire column 2-7. A tightly fitting orifice plate 2-2 is installed inside the anti-backfire column 2-7. The area between adjacent anti-backfire columns 2-7 is the outflow area, and the area blocked by the anti-backfire column 2-7 is the blocking area. The areas of the fire holes 2-2-1 in the outflow area of ​​the orifice plate 2-2 are consistent to achieve the balance of the heat load in the furnace. The areas of the fire holes 2-2-1 in the blocking area of ​​the orifice plate 2-2 are also consistent, but the areas of the fire holes in the outflow area and the blocking area are different. The rectangular fire holes are used as an example for explanation. In the two areas, the fire hole area of ​​the outflow area is twice that of the blocking area. The fire hole area of ​​the outflow area can be adjusted by rotating the orifice plate 2-2 manually or electrically controlled. Reducing the fire hole area in the outflow area under low load can greatly reduce the minimum heat load for normal combustion.

[0047] like Figure 5a , Figure 5b and Figure 5c As shown, by adjusting the rotation angle of the orifice plate 2-2, the fire hole area of ​​the outflow area between adjacent anti-flashback columns 2-7 can be adjusted. Figure 5a This is a schematic diagram under high load. The fire hole area in the outflow area is the largest. Figure 5b This is a schematic diagram under medium load. The area of ​​the fire hole in the outflow area is second. Figure 5c This is a schematic diagram under low load, and the fire hole area in the outflow area is the smallest.

[0048] like Figure 6As shown, the folded fin tube 1-1 of the present invention is a spiral fin tube composed of a base tube and an additional spiral fin, or a round fin tube composed of a base tube and an additional flat fin, wherein the fins are bent, and the absolute value of the angle between the folded fin surface of the fin bending part and the original fin plane is 0° to 90°, and each circle of fins has two folded fin surfaces with symmetrical folds, one side of the folded fin surface is bent upward, that is, the angle with the original fin plane is 0° to 90°, and the other side of the folded fin surface is bent downward, that is, the angle with the original fin plane is 0° to -90°, and the angle between the two folds of the fin bending part is 0° to 180°. When arranged in the boiler, the vertex of the two folds is the windward side. ; The folded fin tube 1-1 is arranged between the water inlet header 1-2, the water outlet header 1-4 and the lower header 1-3, and the two ends of the base tube are necked. The size of the base tube after necking is smaller, and a circle of circular iron blocks are welded near the end position to compress the sealing gaskets of the folded fin tube 1-1 and the water inlet header 1-2, the lower header 1-3 and the water outlet header 1-4; the outer circle folded fin tube 1-1-1, the inner circle folded fin tube 1-1-2, the fastened folded fin tube 1-1-3 and the water-cooled fin tube 2-1 all belong to the folded fin tube 1-1, and their structures are similar. The specific sizes should be different according to the circumferential position where they are arranged and the sizes of the base tube and the fins.

[0049] like Figure 7 As shown, the fastened folded fin tubes 1-1-3 are evenly arranged along the circumferential direction; the structure of the heated part of the fastened folded fin tubes 1-1-3 is consistent with that of the folded fin tubes 1-1, the necked pipe section passes through the outlet water header 1-4 and the lower header 1-3 and is fixed by the fastening nut 1-5, the upper and lower bottom surfaces of the base tube are sealed, and the two ends of the base tube outside the outlet water header 1-4 and the lower header 1-3 are provided with threads, and the base tube sections inside the outlet water header 1-4 and the lower header 1-3 are opened with a number of flow holes to ensure the normal flow of water in the fastened folded fin tubes 1-1-3.

[0050] like Figure 8a , Figure 8b and Figure 8c As shown, the top view of the folded fin tube formed by bending the fins of the traditional spiral fin tube is a small arc on the windward side, a large arc on the leeward side, and a drop shape with a large radius of curvature on both sides. One side of the fins on both sides is bent upward and the other side is bent downward. This bending method can make the two folded fin tubes connected more tightly.

[0051] like Figure 9a , Figure 9b and Fig.9c As shown, the folded fin tube formed by bending the fins of the conventional round fin tube is the same as the fin bending method of the spiral fin tube.

[0052] like Fig.10a , Fig.10b and Fig.10cAs shown, taking the premixing chamber 2-3 as a cylindrical space as an example, a plurality of gas mixing sheets 2-3-1 are arranged inside the space, and a symmetrical gas header 2-3-2 is arranged on the periphery. The gas headers 2-3-2 on both sides are welded with a plurality of gas mixing sheets 2-3-1, and the gas mixing sheets 2-3-1 on the same side are arranged in parallel. The gas mixing sheets 2-3-1 on both sides are independent of each other and can be arranged relative to each other or staggered. A gas inlet 2-5 is arranged on the side of the gas header 2-3-2; the gas mixing sheet 2-3-1 is a circular or hexagonal, rectangular or oval straight pipe with straight sections on both sides, and the side of the straight section is opened with a plurality of rows of sequential or staggered There are a series of gas outlet holes 2-3-3, each of which is in the shape of a three-dimensional hole with a conical, triangular, semicircular, diamond, rectangular, hemispherical or spherical protrusion arranged upstream, or a circular, triangular, diamond, semicircular, elliptical, trapezoidal or rectangular plane outlet hole arranged upstream without protrusion and perpendicular to the air flow direction, or a combination of the above three-dimensional holes and plane outlet holes; air flows into the premixing chamber 2-3 and is separated into multiple thin airflows by the mixing sheet 2-3-1. When the airflow flows through the protrusion, a low-pressure area is formed at the gas outlet hole 2-3-3, so that the gas and air are evenly mixed in the low-pressure area.

[0053] like Fig.11 As shown, a plurality of rows of gas outlet holes 2-3-3 are formed on the gas mixing plate 2-3-1, and a protrusion is arranged upstream of each gas outlet hole. The figure takes a hemispherical shape as an example.

[0054] The heat transfer medium in the folded fin tube of the present invention can be water or an organic heat carrier such as heat transfer oil.

[0055] The position of the full premix burner head 2 can be the position for inputting other high-temperature heat sources, which can be high-temperature flue gas, low-temperature waste heat flue gas or solar energy. Therefore, it can not only be used as a heat exchanger for a natural gas boiler, but also as a photothermal absorber.

[0056] As a preferred embodiment of the present invention, the inner surface of the shell 3 and the smoke outlet 3-4 are made of carbon steel supplemented with surface chemical plating or thermal spraying anti-corrosion treatment materials, or directly use ND steel, Corten steel, 316L austenitic stainless steel or cast aluminum silicon alloy materials that are resistant to sulfuric acid dew point corrosion, or use PVC, ABS, PP or PE.

Claims

1. A gas condensing boiler with large turndown ratio, water-cooled premixed combustion and high-intensity heat exchange, comprising a shell (3), Features: The heat exchanger (1) of the gas condensing boiler in the shell (3) is composed of a circle of water-cooled wall tubes (1-6) and one or more circles of annularly arranged folded fin tubes (1-1) outside the water-cooled wall tubes (1-6), wherein the folded fin tubes (1-1) are fin tubes with fins subjected to bending treatment, and the water-cooled wall tubes (1-6) are surrounded to form a radiation heat exchange space in the furnace of the gas condensing boiler, wherein the radiation heat exchange space in the furnace is a full premixed burner head (2) composed of a perforated plate (2-2), a flashback column (2-7), a water-cooled tube (2-1) and a flame stabilizing tube (2-6) from the inside to the outside; the folded fin tubes (1-1), the water-cooled wall tubes (1-6), the water-cooled tubes (2-1) and The flame stabilizing tube (2-6) is arranged between the water inlet header (1-2), the water outlet header (1-4) and the lower header (1-3); the full premix burner is installed on the outer shell (3), and the head (2) of the full premix burner penetrates into the radiation heat exchange space in the furnace to burn and release heat, and the flue gas flows through the gap between the water-cooled wall tube (1-6) and one or more circles of folded fin tubes (1-1), and enters the dew tray (3-2) at the bottom of the condensing boiler through the gap between the outer shell (3) and the outer circle of folded fin tubes (1-1-1), and flows out from the flue gas outlet (3-4) at the bottom of the dew tray (3-2); the condensed water generated by the flue gas flows out from the drain outlet (3-3) at the bottom of the dew tray (3-2); The folded fin tube (1-1) is a spiral fin tube composed of a base tube and an additional spiral fin, or a round fin tube composed of a base tube and an additional plane fin; the absolute value of the angle between the folded fin surface of the fin bending part and the original fin plane is 0° to 90°, each circle of fins has two folded fin surfaces with symmetrical folds, one side of the folded fin surface is bent upward, that is, the angle between the folded fin surface and the original fin plane is 0° to 90°, and the other side of the folded fin surface is bent downward, that is, the angle between the folded fin surface and the original fin plane is 0° to -90°, and the angle between the two folds of the fin bending part is 0° to 180°. When arranged in a boiler, adjacent folded fin tubes (1-1 ) fins are arranged in a staggered manner, and the vertices of the two fold lines are the windward surfaces; the two ends of the base tube of the folded fin tube (1-1) are necked, and the size of the base tube after necking is smaller. A circle of annular iron blocks is welded near the end to compress the sealing gaskets of the folded fin tube (1-1) and the water inlet header (1-2), the lower header (1-3) and the water outlet header (1-4); the folded fin tube (1-1) includes an outer circle folded fin tube (1-1-1) and an inner circle folded fin tube (1-1-2), which have the same structure, and the specific size should be different according to the circumferential position at which they are arranged and the size of the base tube and the fins; The fully premixed burner is placed on the top or bottom of the shell (3). The fully premixed burner is composed of a burner head (2), a premixing chamber (2-3) and a booster fan (2-4) connected in sequence. The premixing chamber (2-3) is a cylindrical or rectangular space. A plurality of gas mixing plates (2-3-1) are arranged inside the space. A symmetrical gas header (2-3-2) is arranged on the periphery. A gas inlet (2-5) is arranged on the side of the gas header (2-3-2). A gas outlet hole (2-3-3) is opened on the gas mixing plate (2-3-1). Swirl blades are added downstream of the premixing chamber (2-3), i.e., below the gas mixing plate (2-3-1) to enhance the mixing effect. ; The air enters the premixing chamber (2-3) through the booster fan (2-4), and is fully mixed with the gas that enters the premixing chamber (2-3) through the gas inlet (2-5) and the gas mixing plate (2-3-1) in sequence. Downstream of the premixing chamber (2-3), the air passes through the gas mixing plate (2-3-1) and then passes through the swirl blades to enhance the mixing effect. The mixed gas then enters the cylindrical space formed by the orifice plate (2-2). The mixed gas flows into the gap of the water cooling tube (2-1) through the fire hole (2-2-1) provided on the orifice plate (2-2), and then passes through the water cooling tube (2-1) and is sprayed toward the flame stabilizing tube (2-6). After being disturbed by the flame stabilizing tube (2-6), the mixed gas enters the furnace and burns. The water-cooling tube (2-1) is a smooth tube. A plurality of water-cooling tubes (2-1) are closely arranged in a circle to form a water-cooling tube bundle. Anti-flashback columns (2-7) are arranged in the gaps between the water-cooling tubes (2-1) near the inner side of the circle. Flame-stabilizing tubes (2-6) are arranged in the gaps near the outer side of the circle. The flame-stabilizing tubes (2-6) are smooth tubes or finned tubes.

2. According to claim 1, a large turndown ratio water-cooled premixed combustion high-intensity heat exchange gas condensing boiler, Features: One end of the outer ring folded fin tube (1-1-1), the inner ring folded fin tube (1-1-2), the water-cooled wall tube (1-6), the water-cooled tube (2-1) and the flame-stabilizing tube (2-6) is connected to the lower header (1-3) by plugging or welding, the other end of the outer ring folded fin tube (1-1-1) is connected to the water inlet header (1-2) by plugging or welding, and the other ends of the inner ring folded fin tube (1-1-2), the water-cooled wall tube (1-6), the water-cooled tube (2-1) and the flame-stabilizing tube (2-6) are all connected to the water outlet header (1-4) by plugging or welding, countersunk holes are provided at the connection through holes to place sealing gaskets to ensure the sealing of the water channel, and the connection is covered with refractory material (3-5); If the connection is plug-in, three or more folded fin tubes in the cylindrical tube bundle composed of the outer ring folded fin tubes (1-1-1) are fastened folded fin tubes (1-1-3), and the fastened folded fin tubes (1-1-3) are evenly arranged along the circumferential direction; the structure of the heated part of the fastened folded fin tubes (1-1-3) is consistent with that of the folded fin tubes (1-1), and the tube section after necking passes through the water inlet header (1-2) and the lower header (1-3) and passes through the water inlet header (1-2) and the lower header (1-3). The base tube is fixed by a fastening nut (1-5), and the upper and lower bottom surfaces of the base tube are sealed. The two ends of the base tube outside the water inlet header (1-2) and the lower header (1-3) are provided with threads, and the base tube sections inside the water inlet header (1-2) and the lower header (1-3) are provided with a plurality of flow holes to ensure the normal flow of feed water in the fastened folded fin tube (1-1-3); if the connection is welded, the fastened folded fin tube (1-1-3) is not required in the outer ring tube bundle of the heat exchanger; The water inlet header (1-2), the water outlet header (1-4) and the lower header (1-3) are all formed by welding two upper and lower disc surfaces to inner and outer wall surfaces, wherein a circular wall surface is provided between the water inlet header (1-2) and the water outlet header (1-4) to completely separate them into two independent spaces; at the connection with the fastened folded edge fin tube (1-1-3), in addition to connection holes provided on the wall surfaces of the water outlet header (1-4) and the lower header (1-3) close to the furnace, connection holes are also provided on the wall surface away from the furnace, and a countersunk hole is provided on the outer side to place a sealing gasket, so as to ensure the sealing of the water channel under the extrusion of the fastening nut (1-5).

3. A large turndown ratio water-cooled premixed combustion high-intensity heat exchange gas condensing boiler according to claim 2, Features: The water inlet header (1-2) is provided with a water inlet (1-2-1), and the water outlet header (1-4) is provided with a water outlet (1-4-1); the feed water enters the water inlet header (1-2) through the water inlet (1-2-1), and enters the lower header (1-3) through the outer circle folded fin tube (1-1-1) and the fastened folded fin tube (1-1-3); the lower header (1-3) simultaneously supplies water to the inner circle folded fin tube (1-1-2), the water-cooled wall tube (1-6), the water-cooled tube (2-1) and the flame-stabilizing tube (2-6); the hot water is collected in the water outlet header (1-4) and flows out from the water outlet (1-4-1).

4. A large turndown ratio water-cooled premixed combustion high-intensity heat exchange gas condensing boiler according to claim 1, Features: The shell (3) is divided into an upper and lower end cover, which are tightly connected by fastening screws (3-1); a sealing material is used to fill the space between the upper and lower end covers, and the shell is sealed by a plurality of fastening screws (3-1) arranged equidistantly along the circumference; when the furnace is shut down, the shell (3) is disassembled, and the fastening nuts (1-5) at both ends of the fastening folded fin tubes (1-1-3) are loosened, that is, the outer circle folded fin tubes (1-1-1), the inner circle folded fin tubes (1-1-2), the fastening folded fin tubes (1-1-3), the water-cooled wall tubes (1-6), the water-cooled tubes (2-1), the flame-stabilizing tubes (2-6), the water inlet header (1-2), the water outlet header (1-4) and the lower header (1-3) are disassembled, thereby greatly reducing the welding workload of the boiler.

5. A gas condensing boiler with large turndown ratio, water-cooled premixed combustion and high-intensity heat exchange according to claim 1, Features: A plurality of gas mixing plates (2-3-1) are welded on the inner walls of both sides of the gas header (2-3-2), the gas mixing plates (2-3-1) on the same side are arranged in parallel, and the gas mixing plates (2-3-1) on both sides are independent of each other and arranged relative to each other or staggered; the gas mixing plates (2-3-1) are circular or hexagonal, rectangular or oval straight pipes with a straight section in the middle, and the side of the straight section is provided with a plurality of gas outlet holes (2-3-3) arranged in sequence or staggered, and each gas outlet hole (2-3-3) is shaped as a conical protrusion, a triangular protrusion or a protruding groove arranged upstream. A three-dimensional hole with a protrusion, a semicircular protrusion, a diamond protrusion, a rectangular protrusion, a hemispherical protrusion or a spherical protrusion, or a circular, triangular, diamond, semicircular, elliptical, trapezoidal or rectangular plane outflow hole arranged upstream without a protrusion and perpendicular to the air flow direction, or a combination of the above three-dimensional holes and the plane outflow hole; air flows into the premixing chamber (2-3) and is divided into a plurality of thin air flows by the mixing sheet (2-3-1), and a low-pressure area is formed at the gas outflow hole (2-3-3) when the air flows through the protrusion, so that the gas and air are evenly mixed in the low-pressure area.

6. A large turndown ratio water-cooled premixed combustion high-intensity heat exchange gas condensing boiler according to claim 1, Features: The anti-flashback column (2-7) is a solid column with a triangular or arc-edged triangular or hump-shaped cross section, and its boundaries are respectively tangent to the inner orifice plate (2-2) and the two outer water-cooling tubes (2-1), so that the triangular gap between the orifice plate (2-2) and the two adjacent water-cooling tubes (2-1) is filled into two arc-shaped narrow channels, thereby increasing the narrow gap length of the cold wall effect, thereby effectively preventing flashback; The space between the anti-flashback columns (2-7) is the outlet of the fire hole (2-2-1) of the orifice plate (2-2), and the mixed gas flows out from the group of fire holes (2-2-1), is diverted when encountering the water cooling tube (2-1), flows out through the narrow gap channel between the anti-flashback columns (2-7) and the water cooling tube (2-1), merges with the mixed gas diverted from the adjacent fire hole group, and is sprayed toward the flame stabilizing tube (2-6), and burns behind the flame stabilizing tube (2-6); A cylindrical space is formed inside the plurality of anti-flashback columns (2-7), in which a perforated plate (2-2) is placed. The anti-flashback columns (2-7) and the perforated plate (2-2) are tightly fitted together, so that the mixed gas cannot flow out from the outlet of the fire hole (2-2-1) blocked by the anti-flashback columns (2-7).

7. A large turndown ratio water-cooled premixed combustion high-intensity heat exchange gas condensing boiler according to claim 1, Features: The orifice plate (2-2) is provided with a plurality of rows of fire holes (2-2-1) in the form of long slits, small holes, petal-shaped holes, or a combination of the above three forms, and each row or a plurality of rows of fire holes have different areas, so that the fire holes are divided into two or more types of fire holes with different areas; The portion of the fire hole (2-2-1) blocked by the anti-backfire column (2-7) is called a blocking hole, and the portion not blocked by the anti-backfire column (2-7) is called an outflow hole; the areas of the fire holes (2-2-1) in the multiple groups of outflow hole regions are completely the same, and the areas of the fire holes (2-2-1) in the multiple groups of blocking hole regions are also completely the same, while the areas of the fire holes (2-2-1) in the outflow hole region and the blocking hole region are different in size.

8. A large turndown ratio water-cooled premixed combustion high-intensity heat exchange gas condensing boiler according to claim 7, Features: A plurality of anti-flashback columns (2-7) are welded together at their upper and lower ends by a circular wall surface, and one or more positioning pins (2-7-1) are arranged on the outer side of the circular wall surface to ensure that the anti-flashback columns (2-7) are placed and fixed at a required angle; The orifice plate (2-2) is tightly fitted with the plurality of anti-backfire columns (2-7) and can be rotated manually or electrically controlled. By adjusting the angle of the rotating orifice plate (2-2), the area of ​​the fire hole (2-2-1) in the outflow hole region is changed. Under the highest load condition, the orifice plate (2-2) is rotated to maximize the area of ​​the fire hole (2-2-1) in the outflow hole region, reduce the outlet flow rate of the mixed gas fire hole, and greatly increase the maximum heat load of the burner under the joint action of the flame stabilizing tube (2-6); under the lowest load condition, the orifice plate (2-2) is rotated to minimize the area of ​​the fire hole (2-2-1) in the outflow hole region, increase the outlet flow rate of the mixed gas fire hole, and greatly reduce the minimum heat load of the burner, thereby increasing the load adjustment range of the burner.

9. A large turndown ratio water-cooled premixed combustion high-intensity heat exchange gas condensing boiler according to claim 1, Features: The gas-fired condensing boiler can also be used as a steam boiler, and the flue gas outlet of the gas-fired condensing boiler is additionally connected to an economizer; the heat transfer medium in the gas-fired condensing boiler is water or heat transfer oil.

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