JPS5817365B2 - Two-fluid spray burner - Google Patents

Description

Detailed Description of the Invention The present invention is a low NOx combustion system in which a burner installed in a boiler or the like performs combustion using air as a medium for spraying liquid fuel or a mixed gas of air and water vapor as a secondary fluid. This invention relates to a two-fluid spray burner that can be used for various purposes, and in particular, the flame from the fuel spray nozzle is installed with a covered flame stabilizer and a distance device that balances the combustion gas flow velocity and flame propagation velocity, thereby stabilizing combustion. This invention relates to a two-fluid spray burner having a structure as described above.

Conventionally, various types of burners have been used in boilers, heating furnaces, etc.; So-called two-fluid spray type burners have been developed and adopted, which improve combustion efficiency by increasing combustion efficiency.

Incidentally, in liquid fuel burners, exhaust gas recirculation and self-recirculation systems are adopted as a countermeasure against pollution, which has recently become a problem, but in the former, piping and fans are used to supply exhaust gas from the flue to the flame section. It is necessary to provide a special structure, and there is a disadvantage that the structure is complicated and the cost is high.

In addition, in the latter case, since a burner having a high-speed air jet mechanism that draws in high-temperature gas in the downstream part of combustion is specially manufactured, there are structural and cost problems as well, and maintenance is also troublesome.

On the other hand, there are two-stage combustion methods in which two-stage combustion air introduction holes are provided in the furnace body, burner tiles, etc., for example,
Burners of the type disclosed in Japanese Patent No. 1-12423 and the like have also been developed.

However, the burner for two-stage nuclide combustion also had the problem of increasing the number of man-hours required to manufacture a special furnace body.

Therefore, NOx generated by combustion can be broadly classified into Fu.
Fuel NOx is divided into el NOx and ThermaI NOx, but the former, Fuel NOx, is generated by the oxidation of N in the fuel, and is caused by the fuel itself, so it cannot be directly controlled by ordinary burner control measures. Excluded.

The latter Thermal NOx is generated depending on the combustion conditions in the burner, etc., and
CH mechanism, combustion process model, etc., the factors that cause NOx to occur are a) The 5th to 6th power of temperature affects the generation, and b)
It is known that the 1/2 power of the oxygen concentration causes a negative effect on the formation, and c) when the carbon in the fuel, residual coal, etc. burns out, it becomes hot in spots and affects the formation. We know that there are three key points.

Therefore, as countermeasures against NOx in burners, etc., it is necessary to effectively implement a) temperature control, b) oxygen suppression, and c) coal grain suppression.

The purpose of the present invention is to solve the problems of the two-fluid spray burner based on the prior art described above, and to solve the problems described above. This is an excellent two-fluid spray burner that is equipped with a heat exchanger, which not only suppresses temperature but also suppresses oxygen, and in addition suppresses coal grains, making it possible to efficiently implement low NOx measures and benefiting furnace-specific applications in various industries. We aim to provide the following.

In order to solve the above-mentioned problems, the structure of the present invention, which is based on the above-mentioned claims in accordance with the above-mentioned object, is to eject primary air and liquid fuel from a nozzle in the form of fine spray, and to set a preset air temperature within the first-stage flame stabilizer. It ignites at the fuel ratio and generates a vortex to form a ridge of reducing flame, which serves as the basis for stable combustion in the later stage.It also acts to suppress coal particles, and then releases secondary air etc. in the space between it and the two-stage flame stabilizer. It entrains and cools it to lower the temperature, forms residual oxygen through low-temperature combustion to suppress oxygen, and maintains an appropriate atomizing air pressure while reducing speed, etc.
The downstream flame stabilizer installed at a position that balances the flow velocity of the mixed air flow of secondary air and combustion exhaust gas with the flame propagation velocity produces optimal combustion, and performs essentially the same combustion as the second-stage combustion with exhaust gas recirculation, resulting in low combustion efficiency. We used technical means to ensure stable combustion while taking measures against NOx, even with flame holders after the two-stage flame holder.

Next, embodiments of the present invention will be described below based on the drawings.

In the embodiment shown in FIG. 1, reference numeral 1 denotes a two-fluid atomizing burner of the present invention, and a nozzle portion 2 is provided at the base of the burner, and the nozzle portion 2 is atomized into fine particles by primary air (not shown). A fuel nozzle 3 for spouting heavy oil is provided, and a secondary air nozzle 4 is integrally externally installed coaxially with the fuel nozzle 3 and has an open front part, and a mounting frame is attached to the casing 5. 6 is integrally fixed, and the burner 1 is attached to a furnace wall (not shown).

In front of the opening of the fuel nozzle 3, a first stage flame stabilizer 7 is integrally provided coaxially with the fuel nozzle 3 and as close as possible via a branch of the mounting frame 6. There is.

As shown in the figure, the first stage flame stabilizer 7 is formed to widen toward the front, and an internal bulkhead 9 for flame stabilization is layered in the shape of a flange at the front of the inside of the truncated conical frame 8. Therefore, the front opening of the secondary air nozzle 4 of the nozzle section 2 is formed so as to face outward from the rear of the first stage flame holder 7.

10 is a second stage flame holder, and its cylindrical frame 1
1, an internal bulkhead 12 is layered in the shape of a flange, and is provided coaxially with the fuel nozzle 3 and first stage flame stabilizer 7 at the tip of the mounting frame 6 (integrally provided with its base opening). is a diameter corresponding to the diameter of the jet stream from the first stage flame holder 7, and the flow velocity and flame propagation of the fuel gas, secondary air, and fuel exhaust gas from the first stage flame holder 7 as described later. are provided at a balanced distance.

The first stage flame holder 7 and the second stage flame holder 10 are fixed via the branched mounting arms 13 of the frame 6 so as to be integrally attached to the furnace wall at the above-mentioned designed distance. However, depending on the design, the axial installation distance of the flame stabilizers 7 and 10 can be adjusted as appropriate with respect to the mounting arm 13 via an appropriate adjustment mechanism.

In the above configuration, the fuel oil is atomized into the fuel nozzle 3 using primary air as the atomizing medium, and is fed with the primary air at an air-fuel ratio of about 0.2, and is atomized from the nuclear fuel nozzle 3, and then immediately transferred to the first stage flame stabilizer 7. A spark discharge device (not shown) discharges sparks within the first stage flame holder γ to start ignition, forming a flame as a reducing flame.

The thus formed flame generates a flame vortex in the vicinity of the bulkhead 9 of the first stage flame holder 7.

Therefore, once ignited, the flame vortex is continuously maintained as a reduction flame, so even if a spark discharge fire is started and then extinguished, the nuclear fire continues and becomes stable.

After the flame of the reduction flame is formed, CO is produced in the vaginal first stage flame holder γ due to the reduction flame.

Gas and H20 gas are generated, and these gases and fuel, which has been decomposed and gasified due to the coal particle suppression effect due to the heat, form a mixed jet and are ejected from the first stage flame stabilizer 7 as a jet flow,
In order to diffuse during the ejection process, the pressure is reduced, and due to the reduced pressure, the secondary air ejected from the secondary air nozzle 4 and surrounding the first stage flame holder 7 is drawn in and mixed, so that the jet stream from the first stage flame holder 7 is cooled and subjected to a low temperature effect.

Furthermore, when the temperature is suppressed in this manner, combustion is suppressed, residual oxygen increases, oxygen suppressing effect is performed, and NOx control is effectively performed.

This is as shown in Figures 4a, 4b, and 4c, and in Figure 4a (vertical axis flame temperature) corresponding to the burner structure shown in Figure 4c, the flame temperature curve C1 of this invention is the flame temperature curve without oxygen suppression. It can be seen that the temperature is more suppressed than in C2.

Moreover, it can be clearly seen that the temperature of the flame in front of the first and second stage flame stabilizers 8 and 10 has decreased, and it can be clearly seen that this is an effective measure against NOx.

Therefore, as shown in FIG. 4b (vertical axis: oxygen degree %), the curve C3 of the amount of supplied oxygen gradually increases between the first and second stage flame stabilizers 8 and 10, and the air-fuel ratio is about 2. While the actual oxygen consumption curve C4 reaches the stoichiometric air-fuel ratio i, op2 at a small increase rate, the oxygen is suppressed by forming the residual oxygen amount Q. The action is completed and NOx
It can be seen that the measures are working effectively.

In addition to the above-mentioned effect, it also has a speed-lowering effect, and as mentioned above, the second stage flame holder 10 (this jet stream enters and is spontaneously ignited by reducing flame when mixed with secondary air.

That is, the atomization, thermal decomposition, and gasification state of the fuel,
By adding secondary air, etc., combustibility conditions are satisfied, and coal grain suppression, temperature suppression, and oxygen suppression are performed in an optimal state.

Therefore, a combustion state including exhaust gas recirculation and two-stage combustion is achieved, and the flame 14 is constantly generated with low NOx.

By maintaining combustion using secondary air, a sufficient combustion temperature can be obtained.

By the way, it is known that what primarily regulates the above-mentioned combustion is the dynamic pressure of the primary air in the fuel nozzle 3, and according to experiments, as shown in FIG. It was found that when the horizontal axis is the dynamic pressure Pkg/ant of the primary air and the vertical axis is the NOx generation concentration Cppm, data of a kind of quadratic curve-like curve can be obtained for the designed nozzle.

Therefore, if the primary air dynamic pressure is set to a predetermined value ζ, the generation of NOx can be suppressed to a minimum.

In addition, the embodiment shown in FIG. 3 is different from the embodiment shown in FIG. This embodiment is coaxially installed at a predetermined position in front of the second stage flame holder 10, and in this embodiment, the first stage flame holder 10 at the front stage becomes an adjustment flame holder, and the third stage flame holder 10' at the final stage. It is possible to attempt complete combustion as an afterburner, in which case the secondary air mixing, coal particle suppression, oxygen suppression effect, and temperature suppression effect will be more ensured in the subsequent process.

The embodiments of this invention are of course not limited to the above-mentioned embodiments, and the arrangement is similar to that of the secondary air nozzle 4.
20 Various configurations of the tube can be adopted to allow steam to be mixed in.

As described above, according to the present invention, in a two-fluid spray burner, a nozzle part provided with a secondary air nozzle surrounding a fuel nozzle has a plurality of flange-shaped bulkheads for flame stabilization coaxially at the front part of the fuel nozzle. By arranging the flame stabilizers at a distance that balances the combustion gas flow velocity and flame propagation velocity, the fuel sprayed by the primary air from the fuel nozzle is basically transferred to the flame stabilizing flange of the first stage flame stabilizer. A mixing effect of fuel, air, and exhaust gas that is substantially similar to the exhaust gas recirculation effect, such as forming a reducing flame by a shaped bulkhead, producing high-temperature exhaust gas, and suppressing coal grains and gasifying them with the generated CO2 and H20 gas. In addition, there is no need to use a flame holder.
The temperature is suppressed by the low temperature effect caused by the secondary air mixture, and the oxygen is suppressed accordingly, resulting in the excellent effect of maintaining a stable flame and performing the first stage combustion with low NOx combustion. .

Furthermore, the jet gas flow coming out of the first stage flame stabilizer draws in secondary air from the surroundings as described above, receives a kind of temperature control effect due to the heat dissipation effect, and achieves appropriate flammability conditions due to the mixing effect.
As a result, the effects of suppressing coal grains, suppressing temperature, and suppressing oxygen work favorably, resulting in an extremely low NO of several 10% compared to normal combustion.
The effect of being able to perform x combustion is achieved.

Further, by providing two or three stage flame stabilizers depending on the combustion conditions of the furnace body such as a boiler and the fuel, etc., there is an effect that combustion can be performed with the lowest possible NOx generation rate.

According to experiments, the fuel used was heavy oil, and the combustion rate was 100,000 Kcae/
h.For flame holder, length 70mm, inner diameter 70mmφ2
When the bases are set at 90 mm intervals, combustion is performed at a primary air spray dynamic pressure of 1.7 to 2 kg/cut, resulting in an excellent low NOx generation rate that is 30 to 40% lower than normal combustion.
The excellent effect of performing x-concentration combustion was obtained.

Although this is a two-fluid spray burner with good anti-pollution measures, the structure is extremely simple, so it is possible to perform optimal combustion operation through rational design, and it is possible to deal with pollution problems and achieve high-efficiency combustion. The effect of making it possible is produced.

[Brief explanation of drawings]

The drawings show an embodiment of the invention, and FIG.
FIG. 2 is a graph explaining the relative relationship between nozzle operating pressure and NOx generation rate; FIG. 3 is a side view explaining another embodiment; FIG. 4a is a flame temperature graph ,
FIG. 4b is an oxygen concentration graph, and FIG. 4c is a nozzle schematic diagram. 3...Atomizing fuel nozzle, 4...Secondary air nozzle, 1
...2-fluid spray burner, γ, 10...Flame stabilizer, 9,
12... Bulkhead for flame stabilization, L... Balance distance.

Claims (1)

[Claims] 1. In a two-fluid spray burner having a fuel nozzle for spraying and a secondary air nozzle integrally provided surrounding the fuel nozzle, a plurality of flame stabilizers are provided coaxially with respect to the fuel nozzle for spraying. Each flame stabilizer has a bulkhead mechanism for flame stabilization, and each flame stabilizer is installed at a distance that balances the flow rate of the combustion mixture gas and the flame propagation speed. A two-fluid spray burner characterized in that a heat insulator is provided close to an opening of the fuel nozzle.