JP2000074329A - EXHAUST GAS SELF-RECIRCULATING TYPE LOW NOx BURNER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set an exhaust gas circulating ratio by suitably regulating to an optimum range by adjusting an exhaust gas recirculating amount after an operation is started. SOLUTION: The exhaust gas self-recirculating type low NOx burner comprises a substantially horizontal nozzle tube 1 having a fuel nozzle 1a at a front end and supplying fuel from a rear end, an air nozzle 3 surrounding the rear end of the tube at a gap and injecting the air along an axis Z from the gap, a cylindrical inner sleeve 4 surrounding the front end side of the tube at a gap (x) axially from the air nozzle, an outer sleeve 5 surrounding an outside of the air nozzle and the inner sleeve at a gap to communicate at one end within a furnace, and a nozzle moving unit 12 moving the nozzle 3 along the axis to regulate the gap (x).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx burner of an exhaust gas self-recirculation type.

[0002]

2. Description of the Related Art Conventionally, NOx reduction means for mixing a part of combustion exhaust gas into combustion air and recirculating the same to suppress the flame temperature and reduce NOx in the exhaust gas has been conventionally known. FIG. 2 shows the exhaust gas circulation rate and the N by this exhaust gas recirculation method.
It is a relation diagram with Ox reduction rate, and each point in the figure has shown the data of an actual can (boiler). From this figure, it can be seen that although the variation is actually large, the NOx increases as the exhaust gas circulation rate increases.
It can be seen that the reduction effect is large.

[0003] The above-mentioned exhaust gas recirculation system has a problem in that it usually requires an installation of a recirculation blower, a duct, and the like, and thus is expensive. Therefore, the low NO of the exhaust gas self-recirculation system that recirculates the exhaust gas inside the burner
x burners are being developed. FIG. 3 is a schematic diagram of a conventional low-NOx burner with self-recirculation of exhaust gas. In this figure, 1 is a nozzle tube, 1a is a fuel nozzle, 2 is a swirler, 3 is an air nozzle, 4 is an inner sleeve, 5 is an outer sleeve, and 6 is an air chamber. Fuel (gas or liquid) is injected into the furnace from the fuel nozzle 1a via the nozzle tube 1. Combustion air is supplied by a forced air blower (FD).
F), is supplied to the swirler 2 through the air nozzle 3 and the inner sleeve 4 and mixed with the fuel while generating a swirling flow, thereby holding the flame. Part of the exhaust gas generated in the furnace is
The air is recirculated through the space between the air nozzle 3 and the inner sleeve 4, and is sucked and mixed by the airflow passing through the air nozzle 3 to be recirculated. Therefore, such an exhaust gas self-recirculation type low NOx burner can be used without changing the pressure loss of the conventional push blower.
For example, it has a feature that an exhaust gas recirculation rate of about 20 to 25% can be obtained.

[0004]

However, the conventional low NOx burner described above has a problem that the amount of exhaust gas recirculation cannot be adjusted. That is, as shown in FIG. 2, the higher the exhaust gas circulation rate, the greater the NOx reduction effect. However, if the exhaust gas circulation rate is too high, combustion becomes unstable. For this reason, the exhaust gas circulation rate needs to be appropriately adjusted and set to an optimum range in the actual operation of the boiler.
However, in the conventional low NOx burner, the exhaust gas recirculation amount cannot be adjusted after the operation is started, and therefore, there has been a problem that it cannot be set to the optimum range.

The present invention has been made to solve such a problem. That is, an object of the present invention is to provide an exhaust gas self-recirculation type low NOx burner which can adjust the exhaust gas recirculation amount after the start of operation and thereby can appropriately adjust and set the exhaust gas circulation rate to an optimum range. It is in.

[0006]

According to the present invention, there is provided a fuel nozzle (1a) for injecting fuel into a furnace, and a substantially horizontal nozzle tube provided with the fuel nozzle at a leading end and supplying fuel from a trailing end. 1), an air nozzle (3) which surrounds the end of the nozzle tube with a gap therebetween and injects air along the axis Z from the gap, and a tip side of the nozzle tube with a gap x in the axial direction from the air nozzle. And an outer sleeve (5) surrounding the air nozzle and the outside of the inner sleeve at an interval and having one end communicating with the inside of the furnace, and further adjusting the gap x. An exhaust gas self-recirculation type low NOx burner is provided, comprising a nozzle moving device (12) for moving an air nozzle (3) along an axis.

According to the configuration of the present invention, fuel (gas or liquid) is injected into the furnace from the fuel nozzle (1a) through the nozzle tube (1), and combustion air is supplied to the air nozzle (3). The fuel and the air can be mixed and burned by supplying the fuel around the fuel nozzle through the inner sleeve (4). Further, there is a gap x in the axial direction between the air nozzle (3) and the inner sleeve (4), and one end of the outer sleeve (5) surrounding the gap is in communication with the inside of the furnace. A part of the exhaust gas generated in the furnace is sucked from the gap x by the air flow, mixed with the air flow and recirculated, so that the flame temperature can be suppressed and the generation amount of NOx can be reduced.

Further, according to the present invention, an air nozzle (3)
Is moved along the axis to adjust the gap x between the air nozzle (3) and the inner sleeve (4) in the axial direction. Can be adjusted, whereby the exhaust gas circulation rate can be appropriately adjusted and set within an optimum range.

[0009]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In each of the drawings, common portions are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a schematic view of a low NOx burner of the exhaust gas self-recirculation type according to the present invention. As shown in this figure, a low NOx burner 10 of the present invention comprises a fuel nozzle 1a for injecting fuel into a furnace and a substantially horizontal nozzle tube 1
, An air nozzle 3, a cylindrical inner sleeve 4,
An outer sleeve 5 having one end communicating with the inside of the furnace is provided. The fuel nozzle 1a may be for liquefied natural gas (LNG) or for a liquid fuel such as heavy oil. Further, a swirler 2 may be provided around the fuel nozzle 1a to impart a swirl to the airflow flowing therethrough.

In this example, a substantially horizontal nozzle tube 1 extends from an end located outside the boiler, through an air chamber 6 into the furnace, and supplies fuel to a fuel nozzle provided at the end. An air blower (not shown) (FD) is provided in the air chamber 6.
Fresh air is supplied under pressure by F). The air nozzle 3 surrounds the end of the nozzle tube 1 with a gap therebetween, and the end communicates with the air chamber 6 so that air is injected along the axis Z from the gap. As shown in the figure, the cross-sectional shape of the air nozzle 3 is configured such that the cross-sectional area inside the furnace is small, the flow velocity of the jetted air flow is increased, and the static pressure at that portion is reduced by Bernoulli's theorem. The cylindrical inner sleeve 4 is attached to the air nozzle 3.
The nozzle tube surrounds the distal end side of the nozzle tube with a gap x in the axial direction from the front end side of the nozzle tube, and the surrounding gas is introduced into the inside from the gap x. The outer sleeve 5 surrounds the outside of the air nozzle 3 and the inner sleeve 4 at an interval, and has one end (tip) communicating with the inside of the furnace.

Therefore, according to this configuration, fuel (gas or liquid) is injected from the fuel nozzle 1a into the furnace through the nozzle tube 1, and the air for combustion is forced into the blower (FDF).
To the air chamber 6, the air can be guided to the swirler 2 through the air nozzle 3 and the inner sleeve 4, where it is mixed with fuel to form and hold a flame while generating a swirling flow. A part of the exhaust gas generated in the furnace is guided between the outer sleeve 5 and the inner sleeve 4 to the gap x in the axial direction on the distal end side of the air nozzle 3, and the air flow passing through the air nozzle 3 causes the inner x to pass through the gap x. It can be sucked inside the sleeve 4 and mixed with the air stream for recirculation.

Further, the low NOx burner 10 of the present invention includes a nozzle moving device 12 for moving the air nozzle 3 along an axis so as to adjust the gap x. The nozzle moving device 12 includes, for example, a plurality of horizontal rods 12 each having one end fixed around the air nozzle 3 and the other end extending to the outside.
a and a fixture 12b (for example, a nut) for horizontally moving and fixing the horizontal rod 12a. With this configuration, by changing the position of the nut screwed into the female screw provided at one end (outer end) of the horizontal rod 12a,
The air nozzle 3 can be freely moved in the horizontal direction.

According to the configuration of the present invention described above, the fuel is
Injecting fuel into the furnace from the fuel nozzle 1a through the nozzle tube 1 and supplying combustion air around the fuel nozzle 1a through the air nozzle 3 and the inner sleeve 4 to mix and burn fuel and air. Can be. In addition, there is a gap x in the axial direction between the air nozzle 3 and the inner sleeve 4, and one end of the outer sleeve 5 surrounding the gap x communicates with the inside of the furnace. A part of the exhaust gas generated in the above is sucked from the gap x, mixed with the air flow and recirculated,
The amount of NOx generated can be reduced by suppressing the flame temperature.

Further, according to the present invention, the air nozzle 3 is moved along the axis so that the air nozzle 3 and the inner sleeve 4 are moved.
Is provided with the nozzle moving device 12 that adjusts the axial gap x, so that after starting the operation, the gap x can be adjusted to adjust the amount of exhaust gas recirculation, thereby appropriately adjusting and setting the exhaust gas circulation rate to an optimal range. can do.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0017]

As described above, in the exhaust gas self-recirculation type low NOx burner of the present invention, the amount of exhaust gas recirculation can be adjusted after the start of operation, whereby the exhaust gas circulation rate is appropriately adjusted to an optimum range. It has an excellent effect that it can be set.

[Brief description of the drawings]

FIG. 1 is a low NOx exhaust gas self-recirculation system according to the present invention.
It is a schematic diagram of a burner.

FIG. 2 is a relationship diagram between an exhaust gas circulation rate and a NOx reduction rate.

FIG. 3 is a schematic view of a conventional exhaust gas self-recirculation type low NOx burner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle tube 1a Fuel nozzle 2 Swirler 3 Air nozzle 4 Inner sleeve 5 Outer sleeve 6 Air chamber 10 Low NOx burner of exhaust gas self-recirculation system 12 Nozzle moving device

Claims (1)

[Claims] A fuel nozzle (1) for injecting fuel into a furnace.
a), a substantially horizontal nozzle tube (1) having the fuel nozzle at the tip and supplying fuel from the end, and air along the axis Z from the gap surrounding the nozzle at a gap. Air nozzle (3), a cylindrical inner sleeve (4) surrounding the distal end side of the nozzle tube with a gap x in the axial direction from the air nozzle, and one end surrounding the air nozzle and the inner sleeve with a gap therebetween. Has an outer sleeve (5) communicating with the inside of the furnace, and further has a nozzle moving device (12) for moving the air nozzle (3) along the axis so as to adjust the gap x. Low NOx with self-recirculation of exhaust gas
Burner.