CN108397772B

CN108397772B - Combustion head

Info

Publication number: CN108397772B
Application number: CN201810425196.7A
Authority: CN
Inventors: 柏盛; 王明君
Original assignee: Shanghai Quanjie Environment Equipment Co ltd
Current assignee: Shanghai Quanjie Environment Equipment Co ltd
Priority date: 2018-05-07
Filing date: 2018-05-07
Publication date: 2024-05-14
Anticipated expiration: 2038-05-07
Also published as: CN108397772A

Abstract

The invention discloses a combustion head, which comprises an outer wall cylinder, an inner wall cylinder and annular cavities formed by the inner edges and the outer edges of sealing surfaces at two ends, wherein fuel gas is injected into the annular cavities through at least one secondary fuel gas connecting pipe, fuel gas distribution holes are distributed on the outer wall cylinder and the inner wall cylinder, the fuel gas flows out of the annular cavities through the fuel gas distribution holes, and fuel gas nozzles are arranged on the fuel gas distribution holes. The annular cavity combustion head can separate combustion-supporting air to form two different mixing ratio airflows, the central primary airflow can ensure to generate stable primary flame (central flame), and the layered secondary air airflow can also well ensure the staged combustion of secondary flame, so that the generation of NOx is greatly reduced.

Description

Combustion head

Technical Field

The invention belongs to the technical field of burners and air-gas mixing devices related to the burners, and particularly relates to a combustion head and a burner. The present invention relates to an associated industrial burner, of the type comprising a burner head mounted on a combustion chamber, the fuel being natural gas, usable in systems with or without external fume circulation.

Background

For combustion units that burn fossil fuels, the exhaust gas can produce environmentally harmful pollutants, particularly the formation of nitrogen and oxygen compounds (e.g., NO 2), commonly referred to as nitrogen oxides NOx. Various measures can be taken in designing the combustion device so that the production of pollutants can be influenced and/or reduced, in particular the burner used therein.

In the case of a burner of a thermal energy system, the amount of nitrogen oxides produced by combustion increases directly exponentially with the flame temperature when the combustion temperature reaches a certain critical temperature. For known burners of the above type, the recommended solutions are all made on how to reduce the flame temperature.

In general, reducing or minimizing NOx production has been desirable for industrial burners. In the past, some effective nitrogen reduction methods are adopted, mainly comprising the steps of using a fuel/air mixture to form main combustion, namely lean combustion (or lean combustion, mainly comprising the step of enabling the content of combustible gas in the mixture to be lower than the air-fuel ratio fuel amount required by normal complete combustion, namely lean combustion, and then matching with secondary combustion of another part of fuel gas in a fuel stage. The main lean combustion approach may be more satisfactory in some devices because the excess air in the lean combustion provides a load to reduce flame temperature and thus nitrogen oxides. The staged gas is later mixed into the combustion zone through a burner edge gas cap or enters the combustion zone through a center gas cap that extends out of the gas nozzle outlet. The secondary combustion fuel and the surplus air of the lean combustion are combusted in the environment with some smoke, so that the reaction effect that the combustible mixed gas is diluted is achieved. However, these arrangements have not always been successful in reducing nox to the desired level.

For example, the main lean fuel mixture requires the addition of a large amount of excess air in the combustion zone, so the air flow rate is relatively very fast. Such high flow rates sometimes exceed flame combustion speeds, creating an unstable combustion flame environment, with unstable flames and combustion not even sustaining.

In patent document DE3811477A1, it is described that for a gas burner, gas is mixed with air at the inlet of the combustion chamber, the gas entering through some mixing pipes. Wherein the fuel gas is directly sent into the inlet of the combustion chamber through the gas mixing pipe and the nozzle thereof, and is mixed with the combustion air to enter the combustion chamber. The outlets of the gas pipes are distributed in different tangential planes in the mixing cavity of the burner according to the divergent direction.

The expression DE19509219 relates to a method and a burner for a burner of this type, in which combustion air is supplied in connection with the combustion of fuel gas, nitrogen oxides are reduced by means of inert gas, wherein the fuel gas is divided into two stages, one stage is superimposed behind the other stage, the combustion air is blown in from the root of the flame in the flow direction of the combustion air, the combustion air with a first stage super-chemical reaction ratio and the fuel gas mixture flow to the flame, the supplementary fuel gas is added in the second stage tangential plane, where the recirculated flue gas is added as inert gas to the second stage, a part of the combustion gas is injected into the second stage and the recirculated flue gas to form a mixture with a lower chemical reaction ratio, and is mixed before reaching the flame.

EP0347834 describes a burner head for a forced-air gas burner with a burner tube containing fuel gas and combustion air distribution means, and associated fuel gas nozzles and air passages, the burner tube being connected to a flame tube, and at the location where the burner tube is connected to the flame tube, there being radially perforated circulating flue gas ports, from which the circulating flue gas flows counter-currently into the flame base, while fuel gas and air flow positively through the nozzles and air passages, the fuel gas projecting into the flame zone divergently in the direction of the longitudinal axis of the burner head interior.

EP0635676 describes a low NOx burner for liquid or gaseous fuels, the burner of which projects into the combustion chamber of a boiler, the burner having at least one fuel nozzle in the burner cartridge for supplying fuel and adjacent to the burner plate, which delivers a large quantity of fuel gas from the burner plate outwardly to the inner wall area of the cartridge, the rapid gas flow through the gap between the cartridge and the burner plate creating a negative pressure at the front edge of the cartridge, the flue gases produced in the combustion chamber being fed to the negative pressure area by internal circulation, the cartridge having a plurality of flow guide corners extending into the negative pressure area.

Chinese patent CN107120652 describes a staged gas low nitrogen burner, which relates to the burner technical field. The staged gas low nitrogen burner includes a distributor, a baffle plate, an ignition electrode, an ignition fuel tube and a combustion can. The distributor is used for providing a flow path for fuel gas and air and comprises a body, a plurality of fuel gas spray pipes, a fuel gas distribution ring and a plurality of air distribution pipes. The body is a cylinder with a first interlayer, and the fuel gas is sprayed out from the fuel gas distribution ring after entering the fuel gas pipe through the body. The air flows through the hollow part of the body, the air distribution pipe and the outer side of the distributor to form an air flow path for providing combustion-supporting gas for the fuel gas. The distribution ring of CN107120652 is thinner, not larger than 4 times the diameter of the gas distribution hole, just the gas is distributed as the inner and outer rings, and there is no function of separating air. The flow guiding disc of CN107120652 guides the air led in by a plurality of air distributing pipes to form a rotating air flow, the main body is air, and no gas distributing device is arranged.

The above patent makes the gas divide into two-stage blowout after the gas distribution ring, provides sufficient air for central flame, has strengthened air and gas mixing, shortens the dwell time of flue gas in the high temperature zone, is favorable to reducing flame temperature. The patent can control the flow and speed of air and fuel gas, control the air-fuel ratio, make fuel gas and air mix fully and burn, reduce the generation of nitrogen oxides.

However, the above-mentioned known methods and structures are not adequate to achieve the increasing demands for reducing pollutant emissions from combustion plants, especially when legal requirements are met for low NOx emissions, which are limited or are problematic.

The object of the present invention is to overcome the above-mentioned drawbacks of the known burner heads by using an innovative distribution of the annular cavity, which distributes the combustion gases very precisely in the vicinity of the flame zone, while separating the combustion air into primary and secondary air and then out of the burner head. The primary air and the secondary air can be completely separated, and meanwhile, the mixing ratio of air and fuel gas of the primary air flow and the secondary air flow can be accurately controlled. By means of this precise control of the air-fuel mixture, it is possible to produce a secondary gas stream (fuel-lean zone) with an air quantity exceeding the chemical reaction ratio and a primary gas stream (fuel-rich zone) with an air quantity below the chemical reaction ratio. Increasing the primary gas stream gas concentration and decreasing the secondary gas stream gas concentration may result in a reduction in the amount of nitrogen oxides produced.

Disclosure of Invention

The invention aims to provide a combustion head and a burner which can accurately control air and fuel gas of primary air flow and secondary air flow to be mixed so as to greatly reduce the generation amount of nitrogen oxides.

The technical scheme of the invention is that the combustion head comprises an outer wall cylinder, an inner wall cylinder and annular cavities formed by the inner edges and the outer edges of two end sealing surfaces, wherein fuel gas is injected into the annular cavities through at least one secondary fuel gas connecting pipe, fuel gas distribution holes are distributed on the outer wall cylinder and the inner wall cylinder, the fuel gas flows out of the annular cavities through the fuel gas distribution holes, and fuel gas nozzles are arranged on the fuel gas distribution holes.

Preferably, the annular cavity has a length in an axial direction of the burner head to create separate primary and secondary air passages, in which the air flow forms a rotating flow of primary air and in which the secondary air flow forms a straight flow of secondary air.

Preferably, the length of the annular cavity is greater than or equal to 20% of the diameter of the burner basket.

Preferably, the gas nozzle is integrated with an air guide component, and the gas nozzle is installed and fixed according to the required gas distribution direction.

Preferably, the combustion gases are distributed to the flame zone through the outlet region of the annular cavity.

Preferably, the gas nozzle is in threaded connection with the thread of the gas distribution hole, and the gas flow is regulated by regulating the screwing depth of the gas nozzle, so that the gas nozzle can be closed after the gas nozzle is completely screwed to the bottom.

Preferably, gas nozzles are arranged on the front side and the rear side of the flame stabilizing tray along the longitudinal length extending in the axial direction of the burner head.

Preferably, the inlet end of the secondary gas connecting pipe is connected with the outlet end of the secondary gas distributing pipe in a piston type nested manner, so that the axial position of the combustion head can be adjusted in a front-back telescopic manner, and the flow of secondary air is adjusted by matching with a gap between the conical closing-in parts at the front end of the inner wall of the burner flame tube.

Preferably, the burner further comprises a cylindrical cavity and a flame stabilizing disc, wherein an outlet of the burner flame tube is in a conical closing shape, a clearance space between the annular cavity and the conical closing of the burner flame tube forms a secondary air throat, the cylindrical cavity provides mounting support for the flame stabilizing disc, and the cylindrical cavity can stretch and slide back and forth on the primary gas distribution pipe along the axial direction of the combustion head so as to adjust the relative position between the cylindrical cavity and the annular cavity.

In summary, the beneficial effects of the invention are as follows: the annular cavity combustion head can separate combustion-supporting air to form two different mixing ratio air flows, the rotating primary air flow can ensure to generate stable primary flame (central flame), and the layered secondary air flow can also well ensure the staged combustion of secondary flame, so that the generation of NOx is greatly reduced.

The invention will be described in more detail by means of examples.

Drawings

FIG. 1 is a schematic view of a burner head of the present invention for use with a burner and positioned in a combustion chamber.

Fig. 2 shows a transverse cross-sectional view and a cross-sectional view taken along the A-A direction of the burner head of the present invention.

Fig. 3 is a transverse cross-sectional view and a cross-sectional view taken along the A-A direction in the drawing of the burner head of the present invention.

FIG. 4 is a schematic view of the structure of the burner head of the present invention.

FIG. 5 is a schematic view of the structure of the combustion head of the present invention having an air deflector mounted to the outer cartridge wall.

FIG. 6 is a schematic view of the structure of the burner head of the present invention.

FIG. 7 is a cross-sectional view of the structure of the burner head of the present invention.

The reference numerals of the present invention refer to the following: 1. the burner comprises a burner head, 2, a main air inlet pipe, 3, a primary gas distribution pipe, 4, a secondary gas distribution pipe, 5, an annular cavity, 6, a gas nozzle, 7, a flame stabilizing disc, 8, a flame tube, 9, an inner wall tube, 10, an outer wall tube, 11, an inner edge, 12, an outer edge, 13, a cylindrical cavity, 14, a primary air channel, 15, a secondary air channel, 16, a secondary air throat, 17, a primary flame generation area, 18, a secondary flame generation area, 19, a primary gas flow, 20, a primary gas flow, 21, a secondary gas flow, 22, an axis of the burner head, 23, a gas distribution hole, 24, a secondary gas connection pipe, 25, a boiler, 26, a combustion chamber, 27, an air guide part, 28, a conical closing-in, and 29 burner head outlet area (long dashed line).

Detailed Description

The invention will now be further illustrated by way of example with reference to the accompanying drawings.

As shown in fig. 1 to 7, which show the specific structure of the burner head of the present invention, the burner head 1 of the present invention is designed with a gas collector of an annular cavity to guide the gas flowing into the area where the burner head generates fire, the burner head comprises an annular cavity formed by an outer wall cylinder 10, an inner wall cylinder 9 and inner and outer edges 11 and 12 of both end closure surfaces, the outer wall cylinder 10, the inner wall cylinder 9 being coaxial with the burner flame cylinder 8, the annular cavity having a length sufficient to ensure that sufficient gas nozzles 6 can be arranged on an extension line of the central axial direction of the combustion chamber 26 to divide the gas quantitatively and stepwise into primary and secondary flame generation areas 17 and 18 of the burner while dividing the combustion air into primary and secondary air.

The burner head (i.e. the gas collector) of the annular chamber of the present invention has a dual function: the first function is that a plurality of gas nozzles 6 are integrated in the gas distribution holes 23 on the outer wall cylinder 10 and the inner wall cylinder 9 of the annular cavity 5, and the gas nozzles 6 can be distributed in the length direction and the diameter direction of the annular cavity 5, and can also be distributed on the surfaces of the inner edge 11 and the outer edge 12 of the annular cavity 5 in the airflow flowing direction. By matching with the gas nozzles 6 with different diameters and numbers, the gas can be accurately distributed into the primary flame generating area 17 (small dotted line circulating area) and the secondary flame generating area 18 (large dotted line circulating area) according to the required flow and the required spraying direction of the gas.

The second function of the combustion head of the annular cavity of the invention divides the combustion-supporting air into two parts, the combustion-supporting air passes through the primary air channel 14 established by the inner wall cylinder 9 of the annular cavity 5, the primary air is formed when the air flow passes through the primary air channel 14, and the secondary air is formed when the combustion-supporting air passes through the secondary air channel 15 formed by the outer wall cylinder 10 of the annular cavity 5 and the flame cylinder 8. Through which the combustion gases are distributed to the flame zone at the outlet area 29 of the burner head 1 for heating the boiler 25.

The ratio of primary air to secondary air can be controlled by design by choosing the appropriate diameter dimensions of the outer 10 and inner 9 wall cylinders of the annular chamber. The ratio of the primary air to the secondary air can be controlled in other ways, the diameter of the flame stabilizing disc 7 is reduced relative to the position of the annular cavity 5, the flow rate of the primary air can be increased, the size of the gap between the flame tube 8 and the outer wall tube 10 of the annular cavity 5 determines the flow cross section area of the secondary air, which is called as a secondary air throat 16, and the size of the secondary air throat controls the air quantity of the secondary air.

A plurality of gas nozzles 6 are mounted on the surfaces of the inner and outer wall barrels 9, 10 and the outer rim 12 of the annular cavity 5. The gas nozzles 6 may be selected in different diameter sizes, numbers and shapes to achieve a desired gas distribution in the primary and secondary flame generating areas 17, 18.

The air guiding members 27 may be metal fins, and are mounted on the inner wall or the outer wall of the annular cavity 5 to guide air flow, so that the strength of the air rotating flow can be enhanced to shorten the length of flame, and the air guiding members can also be used for adjusting the ratio of primary air and secondary air.

The gas nozzle 6 and the air guide 27 are designed as threaded connections with the annular chamber 5 and can be screwed in easily. By adjusting the screwing depth of the gas nozzle 6, the gas flow is adjusted, and the nozzle can be closed by completely screwing to the bottom.

The annular cavity 5 can integrate and install a plurality of other parts to meet additional functions, the ignition electrode and the flame detection electrode can be installed through a proper support, the ignition and flame detection functions are realized, some external parts can be installed to calibrate the central position of the flame tube 8, or universal balls are installed, and the device is convenient to install and easily slide and drag during maintenance.

The main gas flow 19, also the total gas flow, flows through the main intake pipe 2. The gas collector is connected with the main gas inlet pipe 2 through the secondary gas distribution pipe 4 and the secondary gas connecting pipe 24 to receive gas injection, and the number of the secondary gas distribution pipe 4 and the secondary gas connecting pipe 24 can be more than one and can be multiple. Is extended radially and divergently outwards by the main intake pipe 2, and then the secondary gas distribution pipe 4 is parallel to the axis 22 of the burner. The primary gas flow 19 forms a secondary gas flow 21 through the secondary gas distribution pipe 4 and a primary gas flow 20 through the primary gas distribution pipe 3. The secondary gas distribution pipe 4 and the secondary gas connection pipe 24 are coaxially nested by adopting a piston type, so that the gas collector can slide forwards or backwards on the axis 22 of the combustion head, and the purpose is to ensure that the distribution of air flow can be changed by adjusting the position of the annular cavity 5 relative to the conical closing-in 28 and the flame stabilizing disc 7. The primary gas distribution pipe 3 of the present invention is referred to as a central gas distribution pipe, and the secondary gas distribution pipe 4 and the secondary gas connection pipe 24 are referred to as gas distribution pipes for the annular chamber 5.

Because the annular cavity 5 only contains the gas distribution in the outer ring region of the burner, the invention also cooperates with the use of a primary gas distribution system to direct the gas from the outlet of the main inlet pipe 2 to the fire zone of the primary flame generating zone 17. In the primary flame generating region 17, the front side of the flame holder 7 creates an environment of relatively low pressure and high swirl air flow, forming a primary flame (center flame) on the axis of the burner head. The primary gas distribution system may consist of a plurality of gas nozzles, the invention uses a cylindrical cavity 13 which provides both support and mounting location for the flame holding pan 7, including the primary gas nozzles 6. The cylindrical cavity 13 can slide back and forth on the primary gas distribution pipe 3 along the axis 22 of the combustion head in a telescopic manner so as to adjust the relative position with the annular cavity 5.

The burner comprises a flame tube 8, the outer end of the flame tube 8 being open at the interface of the combustion chamber 26. The outlet of the flame tube 8 can be made into a conical closing shape, and the clearance space between the annular cavity 5 and the conical closing 28 of the flame tube 8 forms a secondary air throat 16, which is used for adjusting the flow of secondary air. The annular cavity 5 is adjusted by sliding outwards on the axis 22 of the burner head, so that the ventilation cross-sectional area of the throat of the secondary air can be reduced to reduce the flow of the secondary air.

Due to the combustion head 1 with the annular cavity 5, primary air and secondary air can be completely separated, and meanwhile, the mixing ratio of air and fuel gas of primary air flow and secondary air flow can be accurately controlled. By means of this precise control of the air-fuel mixture, it is possible to produce a secondary gas stream (fuel-lean zone) with an air quantity exceeding the chemical reaction ratio and a primary gas stream (fuel-rich zone) with an air quantity below the chemical reaction ratio. Increasing the primary gas stream gas concentration and decreasing the secondary gas stream gas concentration can create the same physicochemical mechanism (lean burn and rich burn) for reduced nitrogen oxide production.

The combustion head with the annular cavity structure can separate combustion-supporting air to form two different mixing ratio air flows, the rotating primary air flow can ensure to generate a stable primary flame generating area 17 (central flame), and the layered secondary air flow can also well ensure the staged combustion of the secondary flame generating area 18, so that the generation of NOx is reduced.

The burner head of the present invention is not limited to the structure of the above-described embodiment, and various modifications are possible. In general, all modifications that do not depart from the spirit of the invention are intended to be within the scope of the invention.

Claims

1. The utility model provides a combustion head which is characterized in that, including the annular cavity that forms of the inner edge (11) and outer fringe (12) of outer wall section of thick bamboo (10), inner wall section of thick bamboo (9) and both ends closure face, outer wall section of thick bamboo (10) and inner wall section of thick bamboo (9) are with combustor flame tube (8) coaxial, and the gas is poured into annular cavity through at least one second grade gas connecting pipe (24), is distributed on outer wall section of thick bamboo (10) and inner wall section of thick bamboo (9) gas distribution hole (23), and the gas is through gas distribution hole (23) outflow annular cavity, install gas nozzle (6) on gas distribution hole (23); the annular cavity has a certain length in the axial direction of the combustion head so as to generate a separated primary air channel (14) and a secondary air channel (15), wherein the primary air channel (14) forms a primary air flow, and the secondary air channel (15) forms a secondary air flow; the burner comprises a burner flame tube (8), a cylindrical cavity (13) and a flame stabilizing disc (7), wherein an outlet of the burner flame tube (8) is in a conical closing shape, a clearance space between the annular cavity (5) and the conical closing (28) of the burner flame tube (8) forms a secondary air throat (16), the cylindrical cavity (13) provides mounting support for the flame stabilizing disc (7), and the cylindrical cavity (13) can stretch and slide back and forth on a primary gas distributing pipe (3) along the direction of an axis (22) of the burner head so as to adjust the relative position with the annular cavity (5); the inlet end of the secondary gas connecting pipe (24) is connected with the outlet end of the secondary gas distributing pipe (4) in a piston type nested way, the axial position of the combustion head can be adjusted in a front-back telescopic way, and the flow of secondary air is adjusted by matching with a gap between the conical closing-up (28) at the front end of the inner wall of the burner flame tube (8).

2. The burner head according to claim 1, characterized in that the length of the annular cavity is greater than or equal to 20% of the diameter of the burner basket (8).

3. A burner head according to claim 1, characterized in that the gas nozzle (6) is integrated with an air guiding member (27), the gas nozzle (6) being mounted and fixed in accordance with the desired gas distribution direction.

4. The burner head of claim 1 wherein the combustion gases are distributed to the flame zone through an outlet region of the annular cavity.

5. A burner head according to claim 3, characterized in that the gas nozzle (6) is screwed with the screw thread of the gas distribution hole (23), and the gas flow is adjusted by adjusting the screwing depth of the gas nozzle (6), so that the gas nozzle (6) can be closed by screwing completely.

6. A burner head according to claim 1, characterized in that gas nozzles (6) are arranged on the front and rear sides of the flame holder plate in the longitudinal length extending in the direction of the axis (22) of the burner head.