CN111853747A - A cylindrical low-nitrogen energy-saving pressurized water tube boiler - Google Patents

Abstract

The invention discloses a cylindrical low-nitrogen energy-saving pressure-bearing water pipe boiler which comprises an upper end enclosure, a shell, a burner distribution head, a water-cooled wall tube bundle, a water-cooled flame tube bundle, a radiation tube bundle, a high-temperature convection tube bundle, a low-temperature convection tube bundle, a descending tube bundle, a lower end enclosure, an external condenser, a premixer, a matched fan, a water feed pump, a gas valve group, a controller and the like. The side surface of the combustor is used for air inlet, and pipes, metal pore plates, ceramic pore plates and the like which are arranged in a close-packed manner are used for preventing backfire and stabilizing flame; the burner is detachably designed, so that the maintenance is convenient; the water-cooled flame tube bundle of the burner distribution head is arranged in a plane or a convex manner, so that the hearth space is utilized to the maximum extent; the water-cooling flame tube bundle on the boiler body is adopted to cool the flame, so that the problem of heat distribution of the water-cooling combustor is solved. The invention realizes the machine-furnace integration of the plane and curved surface burners, has compact structure, realizes low-nitrogen and ultra-low-nitrogen combustion under lower excess air coefficient, and breaks through the technical monopoly of foreign low-nitrogen burner manufacturers in the field of steam boilers.

Description

A cylindrical low-nitrogen energy-saving pressurized water tube boiler

technical field

The invention relates to the technical field of gas-fired boilers, in particular to a cylindrical low-nitrogen energy-saving pressurized water-tube boiler.

Background technique

According to my country's energy plan, the proportion of natural gas in primary energy will increase to more than 15% by 2035, and the annual consumption will reach more than 640 billion cubic meters. In 2019, my country's natural gas consumption was 306.7 billion cubic meters. In the next 15 years, the annual consumption of natural gas will increase rapidly. my country's industrial fuel gas accounts for about 30% of the total natural gas consumption. The boilers required in the industrial field are mostly low-pressure and small-capacity boilers with a pressure lower than 2.45MPa, including low-pressure hot water boilers and low-pressure steam boilers. At present, coal-fired boilers below 35 steam tons have been basically eliminated, and the market segment of low-pressure and small-capacity boilers has been monopolized by gas-fired boilers. With the development of industry and the continuous increase of natural gas supply, the gas-fired low-pressure boilers under 35 steam tons will increase by more than 5% per year in the next 15 years, and the low-pressure gas-fired boilers have bright prospects.

At present, the mainstream pressure steam boilers on the market are water tube type and fire tube type. Fire tube boilers include vertical horizontal smoke tube boilers, horizontal internal combustion wet back boilers (WNS), etc., and water tube boilers include tubular boilers, D-type boilers, angle tube boilers, etc. The matching burners of mainstream steam boilers are mostly diffusion burners and cylindrical surface burners, all of which have huge furnace space. In recent years, the technology of flat/curved burners has developed rapidly. Water-cooled burners, porous ceramic plate burners, and metal fiber/wire mesh burners have uniform and stable flames, with a regulation ratio of more than 1:5, and a flame temperature below 1100 °C. The nitrogen oxide emission is less than 30mg, which is in line with the latest environmental protection standards. It is widely used in small gas boilers such as gas hot water boilers and gas wall-hung boilers, but has not yet entered the pressure gas boiler market. The flat/curved burner is a surface burner, the flame is suspended in the space of 200mm above the panel, no huge furnace space is needed, and the burner can be arranged only by using one furnace wall of the boiler, and a brand new furnace needs to be designed for this purpose. type to match flat/curved burners. To reduce the furnace space, strengthen heat exchange, reasonably arrange the heating surfaces at different temperatures, and at the same time ensure the boiler's pressure bearing capacity and the convenience of maintenance, it is necessary to develop a compact and high-efficiency boiler matching flat/curved burners.

CN201821004317.2 discloses a low-nitrogen stainless steel condensing hot water boiler. The furnace is arranged from top to bottom, and the flame passes through the primary heat exchanger and the secondary condensing heat exchanger in sequence. The water between the turns is connected through the front and rear water chambers. This type of boiler is a hot water boiler adapted to a flat burner. The furnace space is small and the heat exchange elements are compact, but it has no pressure bearing capacity and cannot generate steam. CN201621007598.8 discloses a low-nitrogen combustion steam boiler, which is composed of a furnace, upper and lower boiler chambers, burners, etc. The furnace includes a water-cooled wall, a first water-cooled tube for reducing the flame temperature, and a second water-cooled for radiant heat exchange. tube, the third water-cooled tube for convection heat transfer. Multiple rows of staggered light tubes are used inside, and it is difficult to clean the flue gas side once it is fouled. The water-cooled tube bundles used to cool the flame are easy to be blocked by carbon deposits, and also need to be cleaned regularly, which is inconvenient to maintain the furnace body.

At present, there is a lack of easy-to-maintain pressure gas-fired boilers suitable for flat/curved burners on the market, so a new type of vertical water-tube boiler is developed for this purpose.

SUMMARY OF THE INVENTION

In order to realize the machine-furnace integration of the plane/curved surface burner, develop a pressurized natural gas boiler that is easy to repair and maintain, compact in size, and realizes low nitrogen condensation, the purpose of the present invention is to provide a cylindrical low nitrogen high efficiency pressurized water tube boiler , adopts the boiler body structure of the upper and lower heads, the middle vertical water pipe, and the cylindrical shell, with detachable flat/curved burners and external condensing heat exchangers. The vertical water pipe in the middle includes five sections: water-cooled wall tube bundle, water-cooled flame tube bundle, radiant tube bundle, high-temperature convection tube bundle and low-temperature convection tube bundle; the outer shell connects the upper and lower ellipsoid/spherical heads and covers the water-cooled wall tube bundle; the boiler body is reduced. Heat dissipation loss; heat exchange in all water pipes, and the arrangement of water pipes is optimized with the change of flue gas temperature to improve the average heat transfer coefficient.

In order to achieve the above-mentioned purpose, this patent adopts the following technical scheme:

A cylindrical low-nitrogen energy-saving pressurized water-tube boiler, comprising an upper head 1, a casing 2, a burner distribution head 3, a membrane-type water-cooled wall tube bundle 4, a water-cooled flame tube bundle 5, a radiant tube bundle 6, a high-temperature convection tube bundle 7, and a low-temperature convection tube bundle. Tube bundle 8, descending tube bundle 9, lower head 10, external condenser 11, premixer 12 and supporting fans, feed water pumps, gas valve groups, and controllers; the membrane-type water-cooled wall tube bundles 4, water-cooled flame tube bundles 5 , radiant tube bundle 6, high temperature convection tube bundle 7, low temperature convection tube bundle 8, descending tube bundle 9 are all connected between the upper head 1 and the lower head 10; 7 and the low-temperature convection tube bundle 8 are connected with the left and right end tubes of the water-cooled flame tube bundle 5 through the flat steel, and the membrane-type water-cooled wall tube bundle 4 and the upper head 1 and the lower head 10 together form a wall surface that restricts the flow of flue gas; shell 2 The boiler body formed by covering all parts except the external condenser 11 and the premixer 12, only the inlet part of the burner distribution head 3 and the connection part between the boiler body and the external condenser 11 are exposed; membrane type water wall tube bundle 4. The upper and lower ends of the water-cooled flame tube bundle 5, the radiant tube bundle 6, the high temperature convection tube bundle 7, the low temperature convection tube bundle 8 and the descending tube bundle 9 are respectively communicated with the upper head 1 and the lower head 10; the outlet of the premixer 12 is connected to the burner distribution The inlet of the head 3, the burner distribution head 3 is close to the water-cooled flame tube bundle 5; the external condenser 11 is connected to the outlet flue of the boiler body and the tube side outlet of the external condenser 11 is connected to the water supply port of the boiler drum 1; The mixed gas of natural gas and air at the outlet of the mixer 12 first enters the burner distribution head 3, and is evenly distributed from the burner distribution head 3 into the water-cooled flame tube bundle 5, where it is ignited and burned on the front surface of the water-cooled flame tube bundle 5, and the generated high-temperature flue gas is sequentially After passing through the radiant tube bundle 6, the high temperature convection tube bundle 7, and the low temperature convection tube bundle 8, it finally enters the external condenser 11; the boiler feed water first enters the external condenser 11 for preheating on the tube side, and then enters the water replenishment port of the upper sealing head 1. The head 1 is allocated to each tube bundle area and enters the lower head 10; the water in the tube bundle is heated to generate steam, and the steam flows upward from the upper head 1 and leaves the boiler; the upper area of the upper head 1 is the steam space, and the lower area is the water space. The lower head is the water space.

The upper head 1 and the lower head 10 are used as pressure-bearing parts, and two types of spherical head and ellipsoidal head are used; the spherical head includes three parts: spherical head, cylindrical section and tube sheet; The ellipsoid head type includes three parts: an ellipsoid head, a cylindrical section and a tube sheet; the lower head 10 has the same main structure as the upper head 1; the upper head 1 is arranged with a steam-water separator, a plurality of flange interfaces , for water intake, steam exhaust, maintenance, installation of pressure gauges, thermometers, water level gauges and safety valves; the lower head 10 is equipped with multiple flange interfaces for maintenance, sewage, and temperature and pressure measurement.

The outer shell 2 and the membrane-type water-cooled wall tube bundle 4 are filled with thermal insulation material, or a cavity is left to reduce the heat dissipation loss of the boiler body; The tensioning effect is used as the fulcrum line in the calculation of the strength of the tube sheet; the premixed gas inlet, the flue gas outlet, the inspection hole, the fire observation hole and the measuring point hole are reserved on the shell 2.

The burner distribution head 3 is composed of a premixed gas inlet 3-1, a wind casing 3-2, an equalizing orifice 3-4 and a combustion surface 3-5; the combustion surface 3-5 adopts a plane or a curved surface Form, fit with the water-cooled flame tube bundle 5; the premixed gas inlet 3-1 is parallel or perpendicular to the combustion surface 3-5 or at any angle. It is an isobaric air duct with side air intake; the equalizing orifice 3-4 is located between the premixed gas inlet 3-1 in the air casing 3-2 and the combustion surface 3-5, which is one or more layers, so that the combustion The premixed gas flow is uniform at each position on the surface 3-5; the combustion surface 3-5 adopts metal orifice plates, porous ceramic plates, closely arranged rectangular tubes, densely arranged spiral fin tubes, and densely arranged circular tubes One of five structures; the small holes on the metal orifice plate and the porous ceramic plate and the gaps between the closely arranged rectangular tubes, spiral finned tubes and round tubes can prevent tempering, equalize gas flow, stabilize The effect of the flame; the premixed gas catches fire after the gap of the water-cooled flame tube bundle 5, so the combustion surface 3-5 is not directly impacted by the flame, only a small amount of radiant heat, and is continuously cooled by the room temperature premixed gas; close-packed arrangement of tubes It is directly connected to the atmosphere, and the gas in the pipe rises after being heated to form a natural circulation of air to cool the densely arranged pipes; the densely arranged pipes are cooled by furnace water; the densely arranged pipes are provided with an upper header 3-5-1 and a lower header 3-5 -2, the boiler feed water from the outlet of the external flue gas condenser 11 first enters the lower header 3-5-2, flows upward along the closely arranged pipes to the upper header 3-5-1, and then enters the lower header 10.

The burner distribution head 3 also includes one or more layers of baffles 3-3 located between the premixed gas inlet 3-1 in the air casing 3-2 and the combustion surface 3-5, so that the combustion surface 3- 5. The premixed gas flow at each position is more uniform;

The burner distribution head 3 is detachable; the burner distribution head 3 is connected and sealed with the water-cooled flame tube bundle 5 by means of a drawer, and is put into the boiler through the opening 2-1 on the casing 2, and is pre-heated in the boiler. It can be fixed under the constraints of the guide rail; the frame of the burner distribution head 3 is sealed with the groove surface in the guide rail, and the sealing strip is added to improve the sealing effect; carbon deposition may occur when the burner distribution head is under low load, and the detachable burner The dispensing head 3 is easy to clean, and it is easier to achieve long-term safe operation.

The overall arrangement shapes of the membrane-type water-cooled wall tube bundles 4, water-cooled flame tube bundles 5, radiant tube bundles 6, high-temperature convection tube bundles 7, and low-temperature convection tube bundles 8 include rectangles, trapezoids, and curved-edge trapezoids; The same; when the trapezoidal arrangement is adopted, the flue at the 5th position of the water-cooled flame tube bundle is the widest, and the flue is continuously narrowed along the flue gas flow direction to increase the flue gas flow rate; when the curved trapezoidal arrangement is adopted, the flue width first increases After decreasing, the high temperature convection tube bundle 7 is the widest, making full use of the space of the cylindrical shell, reducing the heat load of the radiant tube bundle 6 and the high temperature convection tube bundle 7, reducing the risk of scaling in the tubes, and then reducing the flue width to increase the flue gas flow rate, Increase the heat transfer coefficient and reduce the usage of tube bundles.

The burner distribution head 3 and the water-cooled flame tube bundles 5 are arranged in a convex shape to increase the combustion surface area; when the boiler power increases, the burner area needs to be proportionally increased, and the boiler height is affected by transportation and the height limit of the boiler room. The increase range is limited, the diameter of the head and the drum is restricted by the processing capacity and the strength of the cylinder, and the increase of the boiler diameter is limited. At this time, the convex arrangement increases the combustion surface area and increases the boiler power without changing the width and height of the boiler; When the convex arrangement is adopted, the combustion surface is arranged into a trapezoid, triangular or a curved surface with sharp protrusions deep into the furnace space, and the arrangement of the water-cooled flame tube bundle 5 and the radiant tube bundle 6 is changed to cool the flame and shield the heat between the combustion surfaces. radiation.

The membrane-type water-cooled wall tube bundle 4 is formed by tangential welding of light pipes with an outer diameter of 25 to 76 mm, or welding of light pipes and 10 to 60 mm flat steel at intervals, or intermediate welding of fin tubes. 1 and the tube ends of the lower head 10 should be necked down to maintain the minimum required size of the hole bridge. The ignition needle, the ignition needle and the fire viewing hole are arranged at the flat steel between the water-cooled flame tube bundle 5 and the membrane water-cooled wall tube bundle 4. It is used to ignite the premixed gas and detect and observe the flame; the water-cooled flame tube bundle 5 adopts a light tube with an outer diameter of 25 to 60 mm, the tube bundle spacing is 1 mm to 20 mm, and the spiral fin with the height of the winding fin is less than 10 mm, and the surface of the tube bundle is away from the burner. The surface of the distribution head 3 is less than 20mm to prevent the premixed gas from catching fire in the gap between the burner distribution head 3 and the water-cooled flame tube bundle 5; the premixed gas ignites and burns after leaving the gap of the water-cooled flame tube bundle 5, and the water-cooled flame tube bundle 5 absorbs the flame The radiant heat and cooling of the flame root, so that the converted nitrogen oxides are less than 30mg under the condition that the excess air coefficient is less than 1.3; the water-cooled flame tube bundle 5 is washed by the high temperature flame for a long time, and condensed water is easily formed on the surface when the furnace is stopped, and it is necessary to prevent high temperature corrosion. and low temperature corrosion, if stainless steel is used, it will face the problem of dissimilar steel welding, so the method of spraying nickel-chromium alloy on the surface is used to improve the corrosion resistance; Absorbs more than 40% of the heat of the boiler, the flue gas temperature is higher than 900 ℃, and the evaporation is strong. The large-diameter tube is used to avoid the flow stagnation caused by steam blockage; the flue gas temperature in the 7 area of the high-temperature convection tube bundle is 900-600 ℃, and the heat is exchanged by convection. Mainly, use tubes with an outer diameter of 25 to 76 mm, choose a smooth tube or a finned tube, and the fin height of the finned tube is less than 10 mm to avoid over-temperature damage to the fins; the low-temperature convection tube bundle 8 and the external condensing heat exchange The heat exchange temperature difference in the area of the device 11 is small, and it is necessary to take measures to strengthen heat exchange, including densely packed light tubes, spiral finned tubes, finned tubes, and pin-finned tubes; the descending tube bundle 9 is located outside the water wall tube bundle 4, and the upper Between the head 1 and the lower head 10, they are not heated, and are mostly arranged near the water-cooled flame tube bundle 5, the radiant tube bundle 6, and the high-temperature convection tube bundle 7. The heat flow density in these tube bundles is high, and the water evaporates strongly, corresponding to the lower seal. The head 10 area needs to be supplemented with a large amount of water, and the descending tube bundle 9 is arranged to avoid the problem of heat transfer deterioration caused by flow stagnation in the tube bundle area.

The external condenser 11 is a water-tube heat exchanger, and the heat exchange tube bundles are all bare tubes 11-2 to reduce fouling on the flue gas side; the water supply of the steam boiler is much less than that of the hot water boiler, in order to ensure that the When the flow velocity on the water side reaches more than 0.3m/s, several light pipes need to be divided into one group, and water chamber 11-3 is used to connect each group of light pipes; water chamber 11-3 is located on both sides of light pipe 11-2, and there are upper and lower The partition plate of each group of water pipes, the water flows back and forth in each group of pipes, the water chamber 11-3 is sealed with a flanged blind plate 11-4, which can be opened to clean the dirt on the water side; the outlet 11-5 is located in the external condenser 11. The upper part is convenient for the water flow to take away the accumulated bubbles in the heat exchanger in time; because the pressure bearing capacity of the water chamber 11-3 is weak, the feed pump is located behind the external condenser 11 to ensure that the external condenser 11 is not under pressure Or only under slight pressure; the external condenser 11 adopts austenitic stainless steel of grade 304 or above or ferritic stainless steel of grade 430 or above to reduce the corrosion of condensed water.

The premixer 12 provides premixed gas for the burner distribution head 3 and is connected to the premixed gas inlet of the burner distribution head 3; the premixer 12 consists of a cylindrical shell 12-1, a coaxial cylindrical sleeve 12- 2. The central air pipe 12-3 and the rectifying plate 12-4 are composed of four parts; the coaxial cylindrical sleeve 12-2 accounts for 20% to 60% of the total axial length of the premixer, and is close to the air inlet side of the premixer. The premixer is divided into two parts: the inner part of the sleeve and the outer part of the sleeve, and the areas of the two parts are the same; Outlet side; the air flows along the axis of the premixer 12, the natural gas passes through the cylindrical shell 12-2 and enters the inner space of the coaxial cylindrical sleeve 12-2, the coaxial cylindrical sleeve 12-2 and the central gas pipe 12- 3 is connected, the inner and outer sides of the coaxial cylindrical sleeve 12-2 and the lower surface of the central gas pipe 12-3 are provided with small holes whose axis is inclined to the surface, and the natural gas is ejected from the inclined small holes to form a rotating jet, so that the gas Fully mixed with air under the action of rotary stirring, the direction of the inner and outer swirls of the coaxial cylindrical sleeve 12-2 is the same or different, and the rectifying plate 12-4 on the outlet side is used to eliminate the rotation of the premixed gas ; The rectifier plate 12-4 is a cross plate type, a rice-shaped plate type or a parallel plate type.

The innovations, advantages and positive effects of the present invention are:

1. The cylindrical low-nitrogen high-efficiency pressurized water-tube boiler of the present invention adopts the design concept of machine-furnace integration, combines the flat/curved burner with the pressurized boiler, and abandons the structure of the traditional large furnace; The wall is covered to reduce the heat dissipation loss of the boiler body; the heat exchange of the whole water pipe, and the arrangement of the water pipes is optimized with the change of the flue gas temperature, and the average heat transfer coefficient is improved.

2. The flat/curved surface burner of a cylindrical low-nitrogen high-efficiency pressurized water-tube boiler of the present invention adopts the principle of water-cooled nitrogen reduction, and uses a part of the heating surface of the boiler body as the water-cooled flame tube bundle of the burner, which solves the problem of water-cooled low-nitrogen reduction. The problem of heat distribution is that under the condition that the excess air coefficient is less than 1.3, the target of nitrogen oxide emission is not higher than 30mg.

3. The cylindrical low-nitrogen high-efficiency pressurized water-tube boiler of the present invention adopts a drawer-type detachable burner distribution head, which avoids the problem that the traditional water-cooled low-nitrogen burner cannot be disassembled and is scrapped due to carbon blockage during long-term operation. .

4. A cylindrical low-nitrogen high-efficiency pressurized water-tube boiler of the present invention optimizes the arrangement of the combustion plane/curved surface and the radiant tube bundle, adopts a convex arrangement, maximizes the use of the furnace space, and increases the burner under a given furnace width power.

5. The cylindrical low-nitrogen high-efficiency pressurized water-tube boiler of the present invention adopts an all-light tube condenser to reduce fouling on the flue gas side and facilitate cleaning. The water side adopts a water chamber to connect each light tube, and the water chamber can be opened for cleaning , which avoids the problem that the fouling gas side and the water side of the traditional condensing heat exchanger are difficult to clean due to scaling and clogging.

Description of drawings

Fig. 1 is a schematic cross-sectional view of a cylindrical low-nitrogen energy-saving pressurized water-tube boiler of the present invention.

Fig. 2a is a schematic diagram of an ellipsoidal upper head; Fig. 2b is a schematic diagram of a spherical upper head.

Figure 3a is a schematic diagram of each part of the burner distribution head; Figure 3b is a schematic diagram of a drawer connection; Figure 3c is a schematic diagram of a cross-sectional view of the burner distribution head.

Figure 4a is a schematic diagram of the trapezoidal arrangement of membrane-type water-wall tube bundles, water-cooled flame tube bundles, radiant tube bundles, high-temperature convection tube bundles and low-temperature convection tube bundles; Figure 4b is membrane-type water-wall tube bundles, water-cooled flame tube bundles, radiant tube bundles, high-temperature convection tube bundles and low-temperature convection bundles Schematic diagram of the curved edge trapezoidal arrangement of the tube bundle.

Fig. 5 is a schematic diagram of the convex arrangement of the burner distribution head and the water-cooled flame tube bundle of a cylindrical low-nitrogen energy-saving pressure water-tube boiler of the present invention.

6 is a schematic diagram of an external condenser of a cylindrical low-nitrogen energy-saving pressurized water tube boiler of the present invention.

Fig. 7a is a schematic cross-sectional view of a premixer of a cylindrical low-nitrogen energy-saving pressurized water-tube boiler of the present invention; Fig. 7b is a schematic perspective view of a pre-mixer of a cylindrical low-nitrogen energy-saving pressurized water-tube boiler of the present invention.

Detailed ways

The patent will be described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1 , a cylindrical low-nitrogen energy-saving pressurized water-tube boiler of the present invention includes an upper head 1, a casing 2, a burner distribution head 3, a membrane-type water-cooled wall tube bundle 4, a water-cooled flame tube bundle 5, and a radiant tube bundle 6. , high temperature convection tube bundle 7, low temperature convection tube bundle 8, descending tube bundle 9, lower head 10, external condenser 11, premixer 12 and supporting fans, feed pumps, gas valve groups, controllers; Wall tube bundles 4, water-cooled flame tube bundles 5, radiant tube bundles 6, high temperature convection tube bundles 7, low temperature convection tube bundles 8, and descending tube bundles 9 are all connected between the upper head 1 and the lower head 10; the membrane-type water-cooled wall tube bundle 4 is surrounded by The radiant tube bundle 6, the high temperature convection tube bundle 7 and the low temperature convection tube bundle 8 are connected to the left and right end tubes of the water-cooled flame tube bundle 5 through the flat steel. The wall surface where the flue gas flows; the shell 2 covers the boiler body formed by all the components except the external condenser 11 and the premixer 12, and only the inlet part of the burner distribution head 3 and the connection between the boiler body and the external condenser 11 are exposed. The connecting part; the upper and lower ends of the membrane type water-cooled wall tube bundle 4, the water-cooled flame tube bundle 5, the radiant tube bundle 6, the high temperature convection tube bundle 7, the low temperature convection tube bundle 8 and the descending tube bundle 9 are respectively communicated with the upper head 1 and the lower head 10; The outlet of the mixer 12 is connected to the inlet of the burner distribution head 3, and the burner distribution head 3 is adjacent to the water-cooled flame tube bundle 5; the external condenser 11 is connected to the outlet flue of the boiler body and the tube side outlet of the external condenser 11 is connected to The water replenishment port of the drum 1; the mixed gas of natural gas and air from the outlet of the premixer 12 first enters the burner distribution head 3, and is evenly distributed from the burner distribution head 3 into the water-cooled flame tube bundle 5, and ignites on the front surface of the water-cooled flame tube bundle 5 Combustion, the generated high-temperature flue gas passes through the radiant tube bundle 6, the high-temperature convection tube bundle 7, and the low-temperature convection tube bundle 8 in turn, and finally enters the external condenser 11; the boiler feed water first enters the external condenser 11 for preheating on the tube side, and then enters the upper head The water supply port of 1 is distributed to each tube bundle area through the upper head 1 and enters the lower head 10; the water in the tube bundle is heated to generate steam, and the steam flows upward from the upper head 1 and leaves the boiler; the area above the upper head 1 is the steam. space, the lower area is the water space, and the lower head is the water space.

As a preferred embodiment of the present invention, the upper head 1 and the lower head 10 are used as pressure-bearing parts, and two types of spherical head and ellipsoidal head are used; as shown in Figure 2b, the spherical head type It includes three parts: a spherical head, a cylindrical section and a tube sheet; as shown in Figure 2a, the ellipsoidal head type includes three parts: an ellipsoidal head, a cylindrical section and a tube sheet; the lower head 10 and the upper head The main structure of 1 is the same; the upper head 1 is equipped with a steam-water separator, a plurality of flange interfaces for water intake, steam exhaust, maintenance, installation of pressure gauges, temperature gauges, water level gauges and safety valves; the lower head 10 is arranged with many A flange interface for maintenance, sewage, temperature and pressure measurement.

As a preferred embodiment of the present invention, the casing 2 and the membrane-type water-cooled wall tube bundle 4 are filled with thermal insulation materials, or a cavity is left to reduce the heat dissipation loss of the boiler body; the casing 2 and the upper and lower heads 1 and 10 The edge of the tube sheet is welded, which plays the role of tension and support, and serves as the fulcrum line when calculating the strength of the tube sheet; the shell 2 is reserved for the premixed gas inlet, the flue gas outlet, the inspection hole, the fire observation hole and the measuring point hole.

As shown in Figure 3a, Figure 3b, Figure 3c, the burner distribution head 3 is composed of four parts: a premixed gas inlet 3-1, a wind casing 3-2, an equalizing orifice plate 3-4 and a combustion surface 3-5 ; The combustion surface 3-5 is in the form of a plane or a curved surface, and is attached to the water-cooled flame tube bundle 5; the premixed gas inlet 3-1 is parallel or perpendicular to the combustion surface 3-5 or at any angle, and the air shell 3-2 is parallel when it is parallel. It is a gradually expanding section. When vertical, the air casing 3-2 is an isobaric air duct with side air intake; the equalizing orifice plate 3-4 is located in the premixed gas inlet 3-1 in the air casing 3-2 to the combustion surface 3-5. There is one or more layers in between, so that the premixed gas flow at each position on the combustion surface 3-5 is uniform; the combustion surface 3-5 adopts metal orifice plates, porous ceramic plates, closely arranged rectangular tubes, One of five structures of spiral finned tubes, closely arranged round tubes; small holes on metal orifice plates and porous ceramic plates and gaps between closely arranged rectangular tubes, spiral finned tubes and round tubes All of them play the role of preventing tempering, equalizing gas flow, and stabilizing flame; the premixed gas catches fire after the gap of the water-cooled flame tube bundle 5, so the combustion surface 3-5 is not directly impacted by the flame, only a small amount of radiant heat, and continues It is cooled by premixed gas at room temperature; the densely arranged pipes are directly connected to the atmosphere, and the gas in the pipes rises after being heated to form a natural circulation of air to cool the densely arranged pipes; the densely arranged pipes are cooled by furnace water; the densely arranged pipes are provided with an upper header 3-5-1 and the lower header 3-5-2, the boiler feed water from the outlet of the external flue gas condenser 11 first enters the lower header 3-5-2, and flows upward along the densely arranged pipes to the upper header 3-5 -1, and then enter the lower head 10.

As shown in FIG. 3C , the burner distribution head 3 further includes one or more layers of baffles 3-3 located between the premixed gas inlet 3-1 in the air casing 3-2 and the combustion surface 3-5 , so that the premixed gas flow at each position on the combustion surface 3-5 is more uniform.

As shown in Figure 3b, the burner distribution head 3 is detachable; the burner distribution head 3 is connected and sealed with the water-cooled flame tube bundle 5 by means of a drawer, and is put into the boiler through the opening 2-1 on the casing 2 , and fixed under the constraints of the preset guide rails in the boiler; the frame of the burner distribution head 3 is sealed with the groove surface in the guide rail, and the sealing strip is added to improve the sealing effect; when the burner distribution head is under low load, carbon deposition may occur, The detachable burner distribution head 3 is easy to clean, and it is easier to achieve long-term safe operation.

The overall arrangement shapes of the membrane-type water-cooled wall tube bundles 4, water-cooled flame tube bundles 5, radiant tube bundles 6, high-temperature convection tube bundles 7, and low-temperature convection tube bundles 8 include rectangles, trapezoids, and curved-edge trapezoids; As shown in Figure 4a, when the trapezoidal arrangement is adopted, the flue at the water-cooled flame tube bundle 5 is the widest, and the flue is continuously narrowed along the flow direction of the flue gas to increase the flow rate of the flue gas; as shown in Figure 4b, the curved When the side trapezoid is arranged, the width of the flue increases first and then decreases, and the high temperature convection tube bundle 7 is the widest, making full use of the space of the cylindrical shell, reducing the thermal load of the radiant tube bundle 6 and the high temperature convection tube bundle 7, and reducing the risk of scaling in the tubes , and then reduce the width of the flue to increase the flow rate of the flue gas, increase the heat transfer coefficient, and reduce the amount of tube bundles used.

As shown in Figure 5, the burner distribution head 3 and the water-cooled flame tube bundles 5 are arranged in a convex shape to increase the combustion surface area; when the boiler power increases, the burner area needs to be proportionally increased, and the boiler height is affected by transportation and Influenced by the height limit of the boiler room, the increase range is limited. The diameter of the head and drum is restricted by the processing capacity and the strength of the drum, and the increase in the diameter of the boiler is limited. At this time, the convex arrangement increases the combustion surface area without changing the width and height of the boiler. , increase the power of the boiler; when the convex arrangement is adopted, the combustion surface is arranged into a trapezoid, triangular or a curved surface with sharp convexity deep into the furnace space, and the arrangement of the water-cooled flame tube bundle 5 and the radiant tube bundle 6 is changed to cool the flame and shield the Thermal radiation between combustion surfaces.

As a preferred embodiment of the present invention, the membrane-type water-cooled wall tube bundle 4 is formed by tangential welding of a light pipe with an outer diameter of 25-76 mm, or welding between a light pipe and a flat steel of 10-60 mm in spaced arrangement, or intermediate welding of a fin tube. When the pipes are tangent, the pipe ends connecting the upper head 1 and the lower head 10 should be necked down to maintain the minimum required hole bridge size. The flat steel between 4 is used to ignite the premixed gas and detect and observe the flame; the water-cooled flame tube bundle 5 adopts a light tube with an outer diameter of 25-60mm, the tube bundle spacing is 1mm-20mm, and the height of the winding fin is less than 10mm. Fins, the surface of the tube bundle is less than 20mm from the surface of the burner distribution head 3 to prevent the premixed gas from igniting in the gap between the burner distribution head 3 and the water-cooled flame tube bundle 5; the premixed gas ignites after leaving the gap of the water-cooled flame tube bundle 5 Combustion, the water-cooled flame tube bundle 5 absorbs the radiant heat of the flame and cools the root of the flame, so that the converted nitrogen oxide is less than 30 mg under the condition that the excess air coefficient is less than 1.3; To generate condensed water, it is necessary to prevent high-temperature corrosion and low-temperature corrosion. If stainless steel is used, it will face the problem of welding dissimilar steels. Therefore, the surface is sprayed with nickel-chromium alloy to improve corrosion resistance; the radiant tube bundle 6 adopts an outer diameter of 51-200mm. The radiant tube bundle area absorbs more than 40% of the heat of the boiler, the flue gas temperature is higher than 900 ℃, and the evaporation is strong. The large diameter tube is used to avoid flow stagnation caused by steam blockage; the flue gas temperature in the 7 area of the high temperature convection tube bundle is 900 ～600°C, mainly convection heat transfer, use tubes with an outer diameter of 25-76mm, choose a smooth tube or a finned tube, and the fin height of the finned tube is less than 10mm to avoid over-temperature damage to the fins; the low-temperature convection The heat exchange temperature difference between the tube bundle 8 and the external condensing heat exchanger 11 area is small, and it is necessary to take measures to strengthen heat exchange, including densely packed light tubes, spiral finned tubes, finned tubes, and pin-finned tubes; the descending tube bundle 9 is located in the Outside the water-cooled wall tube bundle 4, the upper head 1 and the lower head 10 are not heated, and are mostly arranged near the water-cooled flame tube bundle 5, the radiant tube bundle 6, and the high-temperature convection tube bundle 7. The heat flow density in these tube bundle areas is high, The water evaporates strongly, and a large amount of water needs to be supplemented in the corresponding lower head 10 area. The descending tube bundle 9 is arranged to avoid the problem of heat transfer deterioration caused by flow stagnation in the tube bundle area.

As shown in Figure 6, the external condenser 11 is a water-tube heat exchanger, and the heat exchange tube bundles are all bare tubes 11-2, which reduces fouling on the flue gas side; the water supply of the steam boiler is much less than that of the hot water boiler, In order to ensure that the flow velocity of the water side in the heat exchanger reaches more than 0.3m/s, it is necessary to divide several light pipes into one group, and use the water chamber 11-3 to connect each group of light pipes; the water chamber 11-3 is located in the light pipe 11-2. On both sides, there are partition plates for upper and lower groups of water pipes. Water flows back and forth in each group of pipes. The water chamber 11-3 is sealed with a flanged blind plate 11-4, which can open the cleaning water side dirt; The upper part of the external condenser 11 is convenient for the water flow to take away the accumulated air bubbles in the heat exchanger in time; since the pressure bearing capacity of the water chamber 11-3 is weak, the feed water pump is located behind the external condenser 11 to ensure the external condensation The condenser 11 does not bear pressure or only bears a slight pressure; the external condenser 11 adopts austenitic stainless steel above 304 or ferritic stainless steel above 430 to reduce the corrosion of condensed water.

As shown in FIG. 7 , the premixer 12 provides premixed gas for the burner distribution head 3 and is connected to the premixed gas inlet of the burner distribution head 3; the premixer 12 consists of a cylindrical shell 12-1, a coaxial The cylindrical sleeve 12-2, the central gas pipe 12-3 and the rectifying plate 12-4 are composed of four parts; the coaxial cylindrical sleeve 12-2 accounts for 20% to 60% of the total axial length of the premixer, and is close to the premixer On the air inlet side, the premixer is divided into two parts: the inner part and the outer part of the sleeve, and the two parts have the same area; the central air pipe 12-3 is located at the front end of the coaxial cylindrical sleeve 12-2, and the rectifier plate 12-4 Located on the outlet side of the premixer 12; the air flows along the axis of the premixer 12, and the natural gas passes through the cylindrical shell 12-2 into the inner space of the coaxial cylindrical sleeve 12-2, and the coaxial cylindrical sleeve 12- 2 is communicated with the central gas pipe 12-3, the inner and outer sides of the coaxial cylindrical sleeve 12-2, and the lower surface of the central gas pipe 12-3 are provided with small holes whose axis is inclined to the surface, and the natural gas is ejected from the inclined small holes A rotating jet is formed, so that the gas and air are fully mixed under the action of rotating and stirring. The directions of the inner and outer swirls of the coaxial cylindrical sleeve 12-2 are in the same direction or different directions, and the rectifying plate 12-4 on the outlet side is used for Eliminate the rotation of the premixed gas; the rectifier plate 12-4 is a cross plate type, a rice plate type or a parallel plate type.

Claims (10)

1. A cylindrical low-nitrogen energy-saving pressurized water-tube boiler, characterized in that: comprising an upper head (1), a casing (2), a burner distribution head (3), a membrane-type water-cooled wall tube bundle (4), a water-cooled flame Tube bundle (5), radiant tube bundle (6), high temperature convection tube bundle (7), low temperature convection tube bundle (8), descending tube bundle (9), lower head (10), external condenser (11), premixer ( 12) and supporting fans, feed pumps, gas valve groups, and controllers; the membrane-type water-cooled wall tube bundles (4), water-cooled flame tube bundles (5), radiant tube bundles (6), high-temperature convection tube bundles (7), low-temperature convection tube bundles The tube bundle (8) and the descending tube bundle (9) are both connected between the upper head (1) and the lower head (10); the membrane type water wall tube bundle (4) surrounds the radiant tube bundle (6) and the high temperature convection tube bundle (7) and the low-temperature convection tube bundle (8) are connected to the left and right end tubes of the water-cooled flame tube bundle (5) through flat steel, and the membrane-type water-cooled wall tube bundle (4) is connected to the upper head (1) and the lower head (10) Together, they form a wall that restricts the flow of flue gas; the casing (2) covers the boiler body formed by all the components except the external condenser (11) and the premixer (12), and only exposes the burner distribution head (3). The inlet part and the connection part between the boiler body and the external condenser (11); membrane type water-cooled wall tube bundle (4), water-cooled flame tube bundle (5), radiant tube bundle (6), high temperature convection tube bundle (7), low temperature convection tube bundle ( 8) and the upper and lower ends of the descending tube bundle (9) are respectively connected with the upper head (1) and the lower head (10); the outlet of the premixer (12) is connected with the inlet of the burner distribution head (3), and the burner distribution head (3) Adjacent to the water-cooled flame tube bundle (5); the external condenser (11) is connected to the outlet flue of the boiler body and the tube side outlet of the external condenser (11) is connected to the water supply port of the upper drum (1). The mixed gas of natural gas and air at the outlet of the premixer (12) first enters the burner distribution head (3), and is evenly distributed from the burner distribution head (3) into the water-cooled flame tube bundle (5). The front surface of the boiler is ignited and burned, and the generated high-temperature flue gas passes through the radiant tube bundle (6), the high-temperature convection tube bundle (7), and the low-temperature convection tube bundle (8) in sequence, and finally enters the external condenser (11); the boiler feed water first enters the external condenser The tube side of the device (11) is preheated, and then enters the water supply port of the upper head (1), is distributed to each tube bundle area through the upper head (1), and enters the lower head (10); the water in the tube bundle is heated to generate steam, The steam flows upward from the upper head (1) and leaves the boiler; the upper area of the upper head (1) is the steam space, the lower area is the water space, and the lower head is the water space. 2. A cylindrical low-nitrogen energy-saving pressurized water-tube boiler according to claim 1, characterized in that: the upper head (1) and the lower head (10) are used as pressure-bearing parts, and a spherical head type is selected. and ellipsoid head type; the spherical head type includes three parts: a spherical head, a cylindrical section and a tube sheet; the ellipsoid head type includes an ellipsoid head, a cylindrical section and a tube sheet; the The lower head (10) has the same main structure as the upper head (1); the upper head (1) is arranged with a steam-water separator and a plurality of flange interfaces for water intake, steam exhaust, maintenance, installation of pressure gauges, Thermometer, water level gauge and safety valve; the lower head (10) is arranged with a plurality of flange interfaces for maintenance, sewage discharge, temperature and pressure measurement. 3. A cylindrical low-nitrogen energy-saving pressurized water-tube boiler according to claim 1, characterized in that: insulating material is filled between the outer shell (2) and the membrane-type water-cooled wall tube bundle (4), or a space is left Cavity to reduce the heat dissipation loss of the boiler body; the outer shell (2) is welded with the edges of the tube sheets of the upper head (1) and the lower head (10), which play a role of tension and support and serve as a fulcrum line when calculating the strength of the tube sheet; the outer shell (2) Leave the premixed gas inlet, flue gas outlet, manhole, fire observation hole and measuring point hole on the top. 4. A cylindrical low-nitrogen energy-saving pressurized water-tube boiler according to claim 1, characterized in that: the burner distribution head (3) consists of a premixed gas inlet (3-1), a wind shell (3- 2), the flow equalization orifice plate (3-4) and the combustion surface (3-5) are composed of four parts; the combustion surface (3-5) is in the form of a plane or a curved surface, and is fitted with the water-cooled flame tube bundle (5); The mixed gas inlet (3-1) is parallel or perpendicular to the combustion surface (3-5) or at any angle. When it is parallel, the air casing (3-2) is a gradually expanding section, and when it is vertical, the air casing (3-2) is a side inlet. The equal pressure air duct of the gas; the equalizing orifice plate (3-4) is located between the premixed gas inlet (3-1) and the combustion surface (3-5) in the air casing (3-2), and is a layer or Multi-layer, so that the premixed gas flow is uniform at each position on the combustion surface (3-5); the combustion surface (3-5) adopts metal orifice plates, porous ceramic plates, closely arranged rectangular tubes, and densely arranged spiral fins One of the five structures of fin tube and close-packed round pipe; the holes in the metal orifice plate and the porous ceramic plate and the gaps between the close-packed rectangular pipes, spiral fin tubes and round pipes all play the role of The functions of anti-tempering, equalizing gas and flame stabilization; the premixed gas catches fire after the gap of the water-cooled flame tube bundle (5), so the combustion surface (3-5) is not directly impacted by the flame, and only has a small amount of radiant heat. It is continuously cooled by premixed gas at room temperature; the densely arranged pipes are directly connected to the atmosphere, and the gas in the pipes rises after being heated to form a natural circulation of air to cool the densely arranged pipes; the densely arranged pipes are cooled by furnace water; the densely arranged pipes are provided with an upper collector Box (3-5-1) and lower header (3-5-2), the boiler feed water from the outlet of the external flue gas condenser (11) first enters the lower header (3-5-2), and is arranged along the close rows The tubes flow up to the upper header (3-5-1) and then into the lower head (10). 5. The cylindrical low-nitrogen energy-saving pressurized water-tube boiler according to claim 4, wherein the burner distribution head (3) further comprises a premixed gas inlet located in the air casing (3-2) (3-1) One or more layers of deflectors (3-3) between the combustion surface (3-5), so that the premixed gas flow at each position on the combustion surface (3-5) is more uniform; The burner distribution head (3) is detachable; the burner distribution head (3) is connected and sealed with the water-cooled flame tube bundle (5) by means of a drawer, and passes through the opening (2-1) on the casing (2). Put it into the boiler and fix it under the constraints of the preset guide rails in the boiler; the frame of the burner distribution head (3) is sealed with the groove surface in the guide rail, and the sealing strip is added to improve the sealing effect; the burner distribution head has a low load When carbon deposits may occur, the detachable burner distribution head (3) is easy to clean, and it is easier to achieve long-term safe operation. 6. A cylindrical low-nitrogen energy-saving pressurized water-tube boiler according to claim 1, characterized in that: the membrane-type water-cooled wall tube bundle (4), water-cooled flame tube bundle (5), radiant tube bundle (6), high temperature The overall arrangement shapes of the convection tube bundle (7) and the low-temperature convection tube bundle (8) include rectangle, trapezoid, and curved trapezoid; when the rectangular arrangement is adopted, the width of the flue remains unchanged; when the trapezoidal arrangement is adopted, the water-cooled flame tube bundle (5) The flue is the widest at the flue gas flow direction, and the flue flue is continuously narrowed along the flue gas flow direction to increase the flue gas flow rate; when the curved-edge trapezoidal arrangement is used, the flue flue width first increases and then decreases, and the high temperature convection tube bundle (7) is the widest , make full use of the space of the cylindrical shell, reduce the heat load of the radiant tube bundle (6) and the high temperature convection tube bundle (7), reduce the risk of scaling in the tube, and then reduce the flue width to increase the flue gas flow rate, increase the heat transfer coefficient, reduce Tube bundle usage. 7. A cylindrical low-nitrogen energy-saving pressurized water-tube boiler according to claim 1, characterized in that: the burner distribution head (3) and the water-cooled flame tube bundle (5) are arranged in a convex shape, so as to increase the Combustion surface area; when the boiler power increases, the burner area needs to be increased proportionally. The height of the boiler is affected by transportation and the height limit of the boiler room, and the increase is limited. The diameter increase is limited. At this time, the convex arrangement increases the combustion surface area and increases the boiler power without changing the width and height of the boiler; when the convex arrangement is adopted, the combustion surface is arranged into a trapezoid, triangle or sharp The convex curved surface changes the arrangement of the water-cooled flame tube bundle (5) and the radiant tube bundle (6) at the same time, so as to cool the flame and shield the heat radiation between the combustion surfaces. 8. The cylindrical low-nitrogen energy-saving pressurized water-tube boiler according to claim 1, characterized in that: the membrane-type water-cooled wall tube bundle (4) adopts the tangential welding of light pipes with an outer diameter of 25-76 mm or a light pipe It is formed by welding with 10-60mm flat steel at intervals or by welding in the middle of finned tubes. If the bare tube is tangent, the tube ends connecting the upper head (1) and the lower head (10) should be necked down to maintain the minimum required hole bridge. size, the ignition needle, the ignition needle and the fire observation hole are arranged at the flat steel between the water-cooled flame tube bundle (5) and the membrane water-cooled wall tube bundle (4) to ignite the premixed gas and detect and observe the flame; the water-cooled The flame tube bundle (5) adopts a light tube with an outer diameter of 25 to 60 mm, the spacing between the tube bundles is 1 mm to 20 mm, and the spiral fins with a height of less than 10 mm are wound. The surface of the tube bundle is less than 20 mm from the surface of the burner distribution head (3) to avoid premixing The gas ignites at the gap between the burner distribution head (3) and the water-cooled flame tube bundle (5); the premixed gas ignites and burns after leaving the gap of the water-cooled flame tube bundle (5), and the water-cooled flame tube bundle (5) absorbs the radiant heat of the flame And cool the root of the flame, so that the converted nitrogen oxides can be lower than 30mg under the condition that the excess air coefficient is less than 1.3; the water-cooled flame tube bundle (5) is washed by the high temperature flame for a long time, and condensed water is easily formed on the surface when the furnace is shut down. Low temperature corrosion, if stainless steel is used, it will face the problem of welding dissimilar steels, so the method of spraying nickel-chromium alloy on the surface is used to improve the corrosion resistance; the radiant tube bundle (6) adopts a large diameter tube with an outer diameter of 51-200mm. The high-temperature convection tube bundle (7) area has a flue gas temperature of 900-600 °C, with a large diameter tube being used to avoid flow stagnation caused by steam blockage. Convective heat transfer is the main method, and tubes with an outer diameter of 25 to 76 mm are used, and plain tubes or finned tubes are selected. The height of the fins of the finned tubes is less than 10 mm, so as to avoid over-temperature damage to the fins; the low-temperature convection tube bundles (8) and The heat exchange temperature difference in the area of the external condensing heat exchanger (11) is small, and it is necessary to take measures to strengthen heat exchange, including densely packed light tubes, spiral finned tubes, finned tubes, and pin-finned tubes; the descending tube bundle (9) It is located outside the water-cooled wall tube bundle (4), between the upper head (1) and the lower head (10), and is not heated, and is mostly arranged in the water-cooled flame tube bundle (5), the radiant tube bundle (6), and the high-temperature convection tube bundle (7). ), these tube bundle areas have high heat flux density and strong water evaporation. The corresponding lower head (10) area needs to be supplemented with a large amount of water, and a descending tube bundle (9) is set to avoid the heat transfer caused by flow stagnation in the tube bundle area. worsen the problem. 9. A cylindrical low-nitrogen energy-saving pressurized water-tube boiler according to claim 1, characterized in that: the external condenser (11) is a water-tube heat exchanger, and the heat exchange tube bundles are all light tubes (11). -2), reduce the fouling on the flue gas side; the water supply of the steam boiler is much less than that of the hot water boiler. A water chamber (11-3) is used to connect each group of light pipes; the water chamber (11-3) is located on both sides of the light pipe (11-2), and there are partition plates for the upper and lower groups of water pipes, and the water returns in each group of pipes The water chamber (11-3) is sealed with a flanged blind plate (11-4), which can open and clean the dirt on the water side; the outlet (11-5) is located on the upper part of the external condenser (11), which is convenient for the water flow to take away in time Bubbles accumulated in the heat exchanger; since the pressure bearing capacity of the water chamber (11-3) is weak, the feed water pump should be located behind the external condenser (11) to ensure that the external condenser (11) is not under pressure or Only bear slight pressure; the external condenser (11) adopts austenitic stainless steel of grade 304 or above or ferritic stainless steel of grade 430 or above to reduce the corrosion of condensed water. 10. A cylindrical low-nitrogen energy-saving pressurized water tube boiler according to claim 1, characterized in that: the premixer (12) provides premixed gas for the burner distribution head (3), and is distributed with the burner The premixed gas inlet of the head (3) is connected; the premixer (12) consists of a cylindrical shell (12-1), a coaxial cylindrical sleeve (12-2), a central gas pipe (12-3) and a rectifying plate ( 12-4) It consists of four parts; the coaxial cylindrical sleeve (12-2) accounts for 20% to 60% of the total axial length of the premixer, and is close to the air inlet side of the premixer, dividing the premixer into sleeves The inner part and the outer part of the sleeve have the same area; the central gas pipe (12-3) is located at the front end of the coaxial cylindrical sleeve (12-2), and the rectifier plate (12-4) is located in the premixer (12) the outlet side of the premixer (12); the air flows along the axis of the premixer (12), and the natural gas passes through the cylindrical casing (12-2) into the inner space of the coaxial cylindrical sleeve (12-2), and the coaxial cylindrical sleeve ( 12-2) communicated with the central trachea (12-3), the inner and outer sides of the coaxial cylindrical sleeve (12-2) and the lower surface of the central trachea (12-3) are provided with small holes whose axes are inclined to the surface where they are located , the natural gas is ejected from the inclined small holes to form a rotating jet, so that the gas and air are fully mixed under the action of rotating and stirring, and the directions of the inner and outer swirls of the coaxial cylindrical sleeve (12-2) are the same or different. , the rectifier plate (12-4) on the outlet side is used to eliminate the rotation of the premixed gas; the rectifier plate (12-4) is a cross plate type, a rice plate type or a parallel plate type.

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