JPH04155107A - Low nox burner - Google Patents

Abstract

PURPOSE:To suppress the generation of NOx in a great measure by constituting a stable reduction combustion area by evaporation and vaporization combustion by means of combustion gas recirclulation created by an annular air between a vaporization cylinder and a combustion cylinder and oxidizing and burning in a very short time the reduction combustion flame in a reduction combustion area. CONSTITUTION:The combustion gas in a combustion cylinder 14 expands, and, further, it is influenced by the throttling section 15 at the tip end of the combustion cylinder 14 and it flows back in an annular space 16 between a vaporization cylinder 7 and the combustion cylinder 14 and returns by flowing to the outside section 17 of a conical partition wall 5 which constitutes a nozzle blow-out section 6. And, the reduction combustion flame that blows out into the furnace from the throttling section 15 at the tip end of the combustion cylinder 14 goes through an annular gap 23 between an outer cylinder 22 and the combustion cylinder 14, and, while it absorbs the heat of the combustion cylinder 14, is mixed quickly with the air flow that blows out from an annular gap 24 and burns completely. In this case the annular gap 24 is made so that, for theoretical air 100%, 30-50% of which may blow from a nozzle blow-out section 6, 10-30% from the passage 19, and 20-50% from the annular gap 24, and an air flow having a high speed and directivity reaches the inside of the reduction combustion flame from the throttle section 15 at the tip end, and the reduction combustion flame is oxidized in a short time and the combustion is completed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a low NOx burner.

(Prior art) When liquid fuel is evaporated and mixed with air as gaseous fuel and burned, harmful substances (odors, soot, N
It has been known for some time that it can significantly reduce emissions such as Ox), and it has been put to practical use in some types of small burners in Japan.

Such a combustion device requires an evaporative mixing zone and a combustion zone. Heating oil is often used as a method for evaporation, but
There is a risk of soot generation and fire.

There are also gun-type burners, which spray liquid fuel at high pressure from a pressure spray nozzle, mix it with air from a fan, and combust it.Normally, no special evaporation zone is provided. Since the surface area of the ll-formed oil particles has increased significantly, conditions have been established for easy evaporation. In an evaporative combustion device using such a pressure spray nozzle, a method has been devised in which high-temperature gas is recirculated by recirculating the combustion gas, and the resulting thermal energy is used to evaporate particulate liquid fuel. When making the combustion amount from one nozzle variable in a pressure injection type, the amount of recirculated gas will change as the turntown area becomes wider.

A burner that incorporates such a recirculation system and further preheats the combustion air to actively promote the evaporation of liquid fuel and perform stable evaporative combustion over a wide range is disclosed in Japanese Patent Publication No. 2-32.
It is disclosed in Japanese Patent No. 531 (see FIG. 5).

(Problems to be Solved by the Invention) In the above-mentioned known technology, combustion air is preheated by heat exchange with high-temperature combustion gas, and then directed to a plurality of jet nozzles drilled near the small diameter part of the evaporator tube. Since the combustion gas is ejected and its suction action recirculates the combustion gas, it is less affected by fluctuations in the amount of recirculated gas due to changes in the amount of combustion, and evaporative combustion can occur over a wide range. Also, since the temperature inside the combustion cylinder is relatively high at 1,300°C, metal materials are prone to thermal distortion, but because the structure is relatively simple and the combustion air has a cooling effect, such troubles can be avoided. To be able to do it.

Alternatively, reduction combustion also has the effect of not producing soot.

The present invention aims to further improve this and provide a low NOx burner.

(Means for solving the problem) A tapered conical partition wall with a nozzle outlet at the tip is provided concentrically with the wind box leading to the blower, and a liquid fuel atomizing nozzle and a liquid fuel atomizing nozzle are installed in the center of the partition wall. An ignition electrode is arranged, and a vaporizing cylinder is arranged surrounding the nozzle outlet of the partition wall,
Furthermore, a combustion tube is arranged concentrically outside the vaporization tube, and an outer tube is arranged concentrically outside the vaporization tube, and the combustion tube and the vaporization tube are provided with a tangential passage in the vicinity of the nozzle outlet so that a part of the combustion air can be absorbed. In addition, the annular space between the vaporization tube and the combustion tube is communicated with the outside of the nozzle outlet, and the diameter of the tip of the combustion tube is reduced (the diameter reduction ratio is lower than that of Japanese Patent Publication No. 2-32531). (lower the furnace pressure of the combustion gas, shorten the residence time of the combustion gas in the combustion cylinder, reduce the residence time <L, reduce the generation of NOx), form a tip constriction part to enable the combustion gas to recirculate, An annular gap was formed between the end of the combustion tube and the end of the outer tube to allow some of the combustion air to be blown out.

(Example) This will be explained based on the drawings. In FIG. 1, combustion air is sent from a blower 1 to a wind box 2. A part of this combustion air is divided by an adjustable damper 3 into the outside of the partition wall 5 formed in the shape of a tapered cone and into the nozzle chamber 4 inside the partition wall 5. The air flowing into the nozzle chamber 4 from the damper 3 is blown out into the vaporizing cylinder 7 from the nozzle blowing part 6 at the tip of the nozzle chamber 4.

On the other hand, the pressure of fuel oil is increased by the hydraulic pump 8, and the fuel oil is increased in pressure by the hydraulic pump 8.
and is sprayed into the vaporizing tube 7 from the nozzle 11 attached to the tip of the nozzle adapter 10.

It mixes with the air blown out from the nozzle blowing part 6 and starts combustion.

Reference numeral 12 denotes an ignition electrode that sparks high-voltage electricity generated by the ignition transformer 13 to ignite and burn the atomized air mixture of fuel oil and air blown out from the nozzle outlet 6.

The atomized mixture air flow passes through the cylindrical vaporization tube 7, where it rapidly evaporates and vaporizes, and then passes through the combustion tube 1, which is concentric with the vaporization tube 7 and surrounds it.
Burns within 4. This combustion gas expands, and is further influenced by the presence of the end constriction part 15 of the combustion tube 14, and flows backward through the annular space 16 between the vaporization tube 7 and the combustion tube 14 (arrow 18), and the conical gas constituting the nozzle outlet 6. The outer part 17 of the partition wall 5
Reflux to. The amount of reflux is approximately 70%.

When this reflux gas flows back through the annular space 16, it
Since the gas is heated from the outside, the vaporizer cylinder 7 is heated to 0.000 mA after the start of combustion.
The temperature reaches approximately 600° C. in 5 seconds, further promoting evaporation of the atomized air mixture, and the temperature reaches 1150° C. within approximately 3 seconds, resulting in a steady combustion state.

As shown in FIG. 2, a part of the combustion air flows in from the passage 19 provided in the tangential direction from the combustion tube 14 to the vaporization tube 7 (reference numeral 20), and forms a thin, high-speed swirling flow of a film on the inner peripheral edge of the vaporization tube 7. 21
form. This high-speed swirling flow 21 prevents the atomized mixed air flow ejected from the nozzle blowout section 6 from colliding with the inner surface of the vaporization tube 7 and turning into droplets at the start when the temperature of the vaporization tube 7 is low, and also prevents the nozzle blowout from the damper 3. This is to add the amount of air necessary for combustion from the passage 19 in order to keep the air flow velocity flowing into the section 6 below 15 m/s, which is a stable ignition condition.

Note that the combustion in the combustion f1114 is reduction combustion (oxygen-deficient combustion), and the air ratio is.

is 0.8, and the inside of the combustion tube 14 is in a state where soot is likely to be generated. In order to suppress the generation of soot, evaporation and vaporization promote the atomization of oil particles (5 to 20μ) in the air mixture flow, resulting in blue flame combustion↓, thus keeping the temperature inside the combustion tube 14 below 1250℃. Prevents the generation of NOx.

Further, the reducing combustion flame ejected into the furnace from the end constriction part 15 of the combustion tube 14 passes through the annular gap 23 between the outer tube 22 and the combustion tube 14 and absorbs the heat of the combustion tube 14. It mixes rapidly with the air flow ejected from the annular gap 24 between the fuel cells 14 and burns completely. In this case, the annular gap 24 is filled with theoretical combustion air 10
0%, the minimum is 60% from the nozzle blowing part 6, passage 1
9 and 30% from the annular gap 24, so that a high-velocity, directional air flow reaches the inside of the reducing combustion flame from the tip constriction part 15.

Therefore, the reduction combustion flame is oxidized and combustion is completed in an extremely short time.

In addition, since it is extremely difficult to form the tangential passage 19 in a small burner with a combustion rate of less than IOQ/h, a small hole with a diameter of about 1.51 mm is formed around the nozzle outlet 6 as shown in FIGS. 3 and 4. Eight or more units 25 were installed, and air was blown out from each unit. In this case, although a swirling flow cannot be generated on the inner surface of the vaporizing cylinder 7, it is possible to prevent oil particles from turning into droplets and from generating carbon (soot).

(Effect) Constructs a stable reduction combustion zone through evaporative combustion due to recirculation of combustion gas from the annular space between the vaporization tube and the combustion tube,
Since the reductive combustion flame in the reductive combustion zone can be oxidized and burned in an extremely short time, it has become possible to greatly suppress the generation of NOx.

In addition, a tangential passage is provided between the vaporization cylinder and the combustion cylinder, from which a swirling air flow can be sent into the vaporization cylinder, so that a thin film of air flow is formed on the inner surface of the vaporization cylinder, and the mixture flow is reduced to droplets. This makes it possible to prevent carbon generation and to provide a two-stage combustion type low NOx burner that is capable of stable combustion even in the reductive combustion range.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the low NOx burner of the present invention. FIG. 2 is a reduced cross-sectional view of the section ■-■ in FIG. 1. FIG. 3 is a sectional view showing the configuration around the nozzle blowing part in a small burner. FIG. 4 is a sectional view taken along the line rV-IV in FIG. 3. FIG. 5 is a sectional view of a known burner. In the figure: 1 blower 2 wind box 3 damper 4 nozzle chamber 5 partition wall 6 nozzle outlet 7 vaporizer tube
8 Hydraulic pump 9 Oil feed pipe 10
Nozzle adapter 11 Nozzle 12 Ignition electrode 13 Ignition transformer 14 Combustion tube 15
Tip throttle part 16 Annular space 17 (partition wall) outer part 19 Passage 21 High-speed swirling flow 22 Outer cylinder 23 Gap
24 Annular gap 25 Small hole or more

Claims (1)

[Claims] A tapered conical partition wall (5) with a nozzle outlet (6) at the tip is installed concentrically within the wind box (2) leading to the blower (1), and the liquid is placed in the center of the partition wall (5). A fuel atomizing nozzle (11) and an ignition electrode (12) are disposed, and a vaporizing tube (7) is provided surrounding the nozzle blowout part (6) of the partition wall (5), and a vaporizing tube (7) is provided outside the vaporizing tube. Combustion cylinder (14
), and an outer cylinder (22) is arranged concentrically on the outside thereof, and the combustion cylinder (14) and the vaporization cylinder (7) have a tangential passage (19) in the vicinity of the nozzle outlet (6). The annular space (16) between the vaporization tube (7) and the combustion tube (14) is communicated with the outside of the nozzle outlet (6), and the combustion tube ( The diameter of the tip of the combustion tube (14) is reduced to form a tip constriction (15) to enable combustion gas to be recirculated, and an annular gap (24) is formed between the end of the combustion tube (14) and the end of the outer tube (22). ) so that part of the combustion air can be blown out.