JPH028204B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel combustion system, and more particularly to a fluid fuel combustion system that reduces the production of nitrogen oxides by lowering the temperature of the combustion zone and providing a reducing atmosphere in the ignition zone.

BACKGROUND OF THE INVENTION Throughout the world there is increasing interest today in the urgent and long-term problems caused by the rapid deterioration of air pollution resulting from the advancement of industrial civilization. Immediate action must be taken to reverse this pollution trend, and public and private economic bodies must develop measures to prevent the release of particulates and gases that can be released into the atmosphere and become a source of pollution. Therefore, it is understood that maximum efforts should be made as a matter of urgency. Such sources of air pollution include nitrogen oxides (NOx) present in the gases emitted from the chimneys of fossil fuel-fired steam generators. Nitric oxide (NO) is an invisible and relatively harmless gas. However, when this NO passes through a steam generator and comes into contact with oxygen, the reaction produces nitrogen dioxide and other nitrogen oxides, collectively known as nitrogen oxides. Nitrogen dioxide is a yellow-brown gas that is toxic to animals and plants in significant concentrations. It is this gas that creates the visible haze at the stack exhaust of a steam generator.

Nitric oxide is created by the reaction of nitrogen and oxygen.
It is also called thermal nitrogen oxide and/or fuel nitrogen oxide. The former results from the nitrogen and oxygen contained in the air supplied for the combustion of fossil fuels, while the latter results from the reaction between the nitrogen contained in the fuel and the oxygen in the combustion air.

The rate at which thermal nitric oxide is produced depends on any one or a combination of the following variables: That is, the factors are (1) flame temperature, (2) residence time of combustion gas in the high temperature zone, and (3) excess oxygen supply. The production rate of nitrogen oxide increases as the flame temperature increases. However, this reaction takes time, and when a mixture of nitrogen and oxygen is held at a specific temperature for a very short time, less nitrogen oxide is produced than when the same mixture is held at a lower temperature for a longer time. is generated. 3700〓 (2038℃) during the combustion of fuel and air, which will be considered below.
In a type of steam generator that produces a flame temperature of
At flame temperatures below 2900°C (1593°C), no appreciable amount of nitrogen oxide (NO) is produced;
The reaction rate increases rapidly when the temperature exceeds 2900°C (1593°C).

The rate at which fuel nitrogen oxides are produced depends primarily on the supply of oxygen in the ignition zone, and in a reducing atmosphere there is no appreciable production of nitrogen oxides. In other words, this is a case where the level of oxygen level in the ignition zone is lower than the level of oxygen required for complete combustion of the fuel.

From the above considerations, it is clear that the production of thermal nitrogen oxides can be reduced to any degree by lowering the flame temperature, and can be minimized by lowering it to below 2900°C (1593°C). Fuel nitrogen oxides can be suppressed by creating a reducing atmosphere in the ignition zone.

With the establishment of more stringent hazardous emissions regulations, manufacturers of fuel combustion equipment are actively seeking means to limit the amount of pollutants formed from the combustion of fossil fuels.

U.S. Patent No. 1, granted to Mr. KRIPPENE et al. and assigned to the assignee of the invention.
No. 3,788,796 discloses a technique used in connection with pulverized coal combustion and achieves a reduction in the production of nitrogen oxides and obtains a more complete combustion of the fuel.

In short, the present invention reduces the generation of nitrogen oxide,
On the one hand, it provides a device capable of more complete combustion of fluid fuel than was previously possible.

Therefore, the device according to the present invention is such that at least a part of the device is located in a wind box to which combustion air is supplied;
It is also formed between the wall of the steam generator and the adjacent burner. Since the furnace wall has burner ports suitable for the combination of fuel and air for the combustion mixture and its ignition, adjacent openings are provided in the burner wall through which parts of the equipment normally located in the wind box can pass. is provided. The device includes a central passageway with an open member terminating in the windbox and a concentric circular cross section terminating in the burner port at the discharge end through which 15 to 30% of the chemically required air volume flows. A conduit having portions spaced concentrically around the opening member thereby discharges to the burner port and is capable of discharging from 5 to 50% of said air volume.
A first annular passageway having 35% flow is formed therebetween. Registers spaced concentrically around the conduit form a second annular passageway opening into the burner port, through which 50 to 65% of said air volume is fed.
Let it flow. Means are provided within the windbox for distributing combustion air between the passageways in the proportions. The nozzle means extends into the windbox to allow fluid fuel to flow into the burner port to form a spray pattern that is substantially symmetrical to the axis of the port.

One of the objects of the present invention is that the initial combustion is carried out with a fuel richness (in excess) to create a reducing atmosphere that suppresses the formation of fuel nitrogen oxides, resulting in a lower peak temperature that minimizes the formation of thermal nitrogen oxides. There is a particular thing.

Another purpose is to limit the initial mixing of flowing fuel and air creating a recirculation zone that stabilizes the flame.

Yet another object is to accommodate the residual air needed for complete combustion in a flow pattern that wraps around the reducing and flame stability zone and mixes with the substantially fluid fuel for complete combustion.

An embodiment of the invention will be described below with reference to the drawings in connection with a fuel combustion device in combination with liquid fuel.
However, the invention is equally applicable to the use of gaseous fuels.

In FIG. 1, reference numeral 10 indicates a fuel combustion device, which performs combustion through a circular burner port 12. The burner port 12 is made of refractory material, has a truncated conical shape that widens toward the furnace side of the front wall 14, and is cooled by fluid flowing within the tube 16. The burner or outer wall 18 is the furnace front wall 14
A wind box 20 is formed therebetween. The burner wall 18 is provided with an adjacent opening 22 through which components of the fuel combustion system normally located within the windbox 20 are admitted.

Drawings by J.Fletcher
A liquid fuel burner 24 of the type disclosed in U.S. Pat. It includes a guide tube 26 extending therethrough. The guide tube 26 has an inlet portion screwed onto a yoke assembly 28, and the yoke assembly is connected to a liquid fuel and atomizing fluid line (not shown). Yoke assembly 28 and member 30
A gasket (not shown) is inserted between the connecting surfaces, and a locking device 32 applies pressure to prevent leakage. A fuel tube or nozzle 34 passes through the guide tube 26 and extends from its distal end. Nozzle 3
4 is connected at an inlet end to an intermediate member 30 and positioned as an outlet end to an atomizer set including a sprayer plate 36 for introducing atomized fuel into the burner ports 12 creating a substantially symmetrical pattern with respect to the axis of the ports. do. The distal end of the guide tube 26 has a support ring 38 to which an air deflector (burner cone) 40 is attached. The deflector 40 has a frustoconical shape, shares a central axis with the burner port 12, and includes an opening through which the sprayer plate 36 passes.

In accordance with the present invention, a double-ended open member 42 is located concentrically with and spaced apart from a portion of the liquid fuel burner guide tube 26 to define a concentric annular cross-sectional central passageway 44 having an open opening in the burner port 12. A conduit 46 extends through the wind box 20 and has an outlet end concentrically spaced apart from the open ended member 42 to define a first annular passageway 48 that discharges to the burner port 12 . The conduit 46 has an inlet portion projecting through a closure member 50 which covers the burner access port 22. The inlet end is then capped with a disk member 52. The closure member 50 and the plate member 52 of the burner wall 18 are covered by an insulating material 54 to prevent heat transfer therethrough. Combustion air is preferably provided in conduit 4 adjacent to burner wall 18.
6 through one or more slots 56 spaced apart from each other. slot 56
are separated by ribs 58 formed in the conduit walls, preferably having arcuate square holes. A sleeve-like member 60 is located within the conduit 46 and is provided with wheels 62 that abut ribs 58 that are partially recessed into the sleeve wall;
Sleeve member 60 facilitates movement across slot 56 to cover some or all of the area of slot 56 providing a means for controlling the amount of air introduced into conduit 46. The outer diameter of the sleeve member 60 is slightly smaller than the inner diameter of the conduit 46, and the axial length thereof is slightly larger than the axial length of the slot 56. A pair of positioning rods 64 are positioned horizontally and spaced apart from each other and have remote ends welded to sleeve member 60 . The other end protrudes outside the wind box 20, and a handle portion 66 is attached so that the sleeve 60 can be positioned from outside the wind box. Locating rods 64 are guided and supported by respective tubular members 68 which extend through plate 52 and insulation to secure support rods 64 to hold sleeve 60 in a selected position relative to slot 56. It has a fixing means 70 to do so. The distance between the trailing edge of slot 56 and the windbox end of tube member 68 is substantially equal to the axial length of the sleeve member such that sleeve 60 abuts the windbox end of tube 68 to allow combustion air to enter conduit 46. The slot 56 is designed to be fully open when The collar-shaped stop 71 is a positioning rod 64
and is fixedly positioned so as to contact the outer end of the tube member 68 when the sleeve member 60 completely covers the slot 56 and substantially blocks the flow of combustion air into the conduit 46.

The plurality of vanes 72 are located in the first annular passageway 48 so as to surround the open-end member 42 outwardly, and
The vanes 72 are also equally spaced apart and preferably linked together so that the shaft member 74
can be operated uniformly and instantaneously from outside the wind box 20 using the manual operation handle 76. The main function of the vanes 72 is to apply a rotation component to the combustion air passing through the first annular passage 48 .

The tubular member 78 has one end fixedly connected to the plate 52, extends concentrically within the conduit 46, is spaced apart from the burner nozzle guide tube 26, and is axially connected to the inlet end of the open-ended member 42. be located far away. Circumferentially spaced struts 80 are located axially intermediate the tube member 78 and support the conduit 46 on the member 78 . The member 78 also supports the guide tube 26 with a plurality of struts 81, and the support rods 81 have a collar shape and are in contact with the inner wall of the tubular member 78.

Sleeve-like member 82 connects member 78 to control the amount of combustion air flowing through central member 44.
is slidably mounted over the front end of the
The space 83 between the forward end 85 of member 82 and the inlet end of member 42 is varied. The sliding member 82 is shown fully retracted in this figure and fully open to allow the entire amount of combustion air to flow from the conduit 46 into the central passage 44.

A pair of positioning rods 64A are located vertically apart from each other, their remote ends are welded to the rear end of the sliding member 82, and the other ends extend through the wind box 20.
A handle 66A is attached to its end, allowing the sliding member 82 to be controlled from outside the wind box. The locating rods 64A are each guided and supported by a tubular member 68A which extends through the plate 52 and the insulation and which locating members 64A extend through the plate 52 and the insulation and are arranged in a manner such that the locating member 64A can maintain the sliding member 82 in a selected position relative to the open end member 42.
A locking means 70A is provided to securely hold 4A. The post 80 also serves as a rear stop for the sleeve member 82 so that the space 83 is at its maximum dimension when the rear end of the sleeve member 82 hits the post 80. Collar-shaped stop 71A
is provided on the positioning rod 64A, and when the front end flange 85 is in contact with the inlet end 86 of the open end member 42, that is, when the space 83 is closed and the inflow of combustion air into the open end member 42 is substantially blocked. , are fixed so as to abut against the outer end of the tube member 68A.

A resistor set 87 is positioned surrounding the conduit 46, with one end fixedly connected to the plate 52 and the other end connected to the burner port 1.
Opens at 2. The resistor set includes a cylindrical housing 88 that closely surrounds the conduit 46 and a slot 89 that is substantially the same shape as the slot 56 .
are placed on top of each other to provide an unobstructed inflow path. The distal end of the housing 88 is secured to the inner periphery of an annular plate member 90, and the member 90 is connected to the register set 8.
It becomes one of the walls forming the entrance to 7. The other wall plate forms an annular plate member 91 that connects with a converging frustoconical member 92 . Plate 91 and member 92 together with conduit 46 form an annular passageway 98 therebetween.

Member 93 connects plate 91 and member 92 to front wall 14. A plurality of damper or register doors 94 are spaced circumferentially and pivotally mounted between walls 91 and 90 and are operable between open and closed positions to control the amount of combustion air passing through second annular passageway 98. do. The dampers 94 are opened and closed at the same time by a shaft 95, and the shaft 95 has an operating handle 96 extending outside the wind box 20. Known ignition device 9
7 passes through the closure member 50 and the plate member 90 and terminates at its furnace end in a second annular passage 98 .

If necessary, positioning rods 64, 64A, damper 9
4 may suitably be a gear set, a link set or other connection system, and may be made compatible with the control of an automatic control device.

FIG. 2 is a drawing showing the end face of the plate member 52, and its components include, for example, a handle 66, which is related to positioning of the sleeve member, which is a component of the invention.
66A and fixing means 70, 70A are attached. Also shown are a pair of observation windows 99 spanning the liquid fuel burner 24 and a handle 76 associated with the shaft used to control the vanes located in the central passage.

In operation according to the preferred embodiment, liquid fuel is supplied to burner 24 and atomized to create a spray into port 12 in a substantially symmetrical manner about the axis of port 12. The total amount of air required for combustion of the fuel is supplied through the wind box 20 and distributed to three separate passages that discharge into the ports 12. The three passages are a central passage 44 and a first annular passage 48.
and a second annular passage 98. The amount of combustion air admitted into each passage is effected by separate flow rate combustion means. i.e. a sleeve member 82 for adjusting the spacing 83 relative to the entrance of the central passageway 44;
A sleeve member 60 that adjusts and changes the opening degree of the slot 56 which is the introduction port of the first annular passage formed by the conduit 46, and a damper that forms and includes the second annular passage and adjusts and changes the opening of the register set 87. It is 94. In accordance with the present invention, the disclosed apparatus provides a means for adjusting the sleeve member 82 to limit the amount of combustion air vented to the central passageway 44 so that initial fuel combustion occurs in a reducing atmosphere. A means is also provided for flame stability to be created by adjustment of the sleeve member 60 which controls the amount of air received in conduit 46 and exhausted through the first annular passageway to effect recirculation of air around the outer periphery of the reduction zone. The last one is a means for adjusting and controlling, by a damper 94, the amount of residual air that wraps around the reduction zone and the flame stabilization zone and is discharged into the second annular passage for ultimately mixing with the fuel and completing combustion. .

In actual operation, 15 to 30% of the chemically theoretically required amount of air flows through the central passage 44, and 5% to 30% of the theoretical amount of air flows through the first annular passage.
to 35% flow to provide stable ignition and lower peak flame temperatures under reducing atmospheres. Since the combustion air flowing through the second annular passage 98 is maintained within a range of 50 to 65% of the theoretical air amount, the air necessary to complete the combustion of the fuel is replenished and the intended purpose of the present invention is achieved. It is something that will be done.

[Brief explanation of drawings]

FIG. 1 is a partial side view of a fluidized fuel combustion apparatus that is an embodiment of the present invention, and FIG.
FIG. 3 is a partial end view of the illustrated device; 10... Fuel combustion device, 12... Burner port, 14... Front wall, 18... Outer wall, 20... Wind box, 26... Guide pipe, 40... Deflector, 42
...Both ends open member, 44...Central passage, 46...
Conduit, 48...first annular passage, 56...slot, 64...support rod, 72...vane, 78...
Pipe member, 82... Attachment member, 85... Front end flange, 87... Register set, 97... Ignition device, 98... Second annular passage.

Claims (1)

[Claims] 1. A furnace that is combined with the peripheral wall of a furnace, has at least one burner port on the peripheral wall, forms a wind box between the peripheral wall and a burner wall located at a distance, and supplies combustion air to the wind box. in which the exhaust opening is located in the burner port, has a concentric circular cross section, and has an air volume of 15 cm, which is the chemically theoretically required amount of air.
a both-end release member located within the wind box forming a central passage through which between 5 and 30% of the air flow; conduit means forming a first annular passage through which the air flows, a register concentric with said first annular passage forming a second annular passage discharging into said burner port and through which 50 to 65% of said air volume flows; means located within the box for distributing combustion air in said ratio between said passages; and nozzle means for spraying liquid fuel into the burner port substantially symmetrically about its axis. A fuel combustion device that uses