JPS604704A - Combustion device - Google Patents

Abstract

PURPOSE:To restrict the generation of NOx and reduce non-combustioned component in the ash by a method wherein a guide plate for arranging air in an external air passage to outside of the passage is installed at the extremity end of an outer cylinder and a circulating means for forcedly circulating air flow stronger than the air flow in the inner air passage is arranged in the external air passage. CONSTITUTION:A guide plate 16 for arranging air in an external air passage 13 outwardly is arranged at the extremity end of an outer cylinder 11 and at the same time a circulating means 17 for forcedly circulating the air flow stronger than the air flow in the inner air passage 12 is arranged in the external air passage 13. Thus, the external air in the external air passage 13 is baffled by a guide plate 16 to be injected outwardly, so that the air is injected into a furnace 1 while suctioning a part of the inner air in the inner air passage 12, resulting in that the root part of the fine coal supplying nozzle 3 shows a high O2 area, NOx is produced from component of N in the fuel to cause O2 to be consumed, thereafter the reducing material is produced at the downstream side of the passage, NOx and the reducing material are reacted with each other and reduced to N2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion device that exclusively burns or co-burns fuel such as liquid or solid fuel, and particularly relates to a combustion device that reduces nitrogen oxides (hereinafter referred to as NOx) in exhaust gas.

Fossil fuels contain N in addition to fuel components such as C and H, and pulverized coal in particular has a larger amount of N than gaseous fuels or liquid fuels.

Therefore, NOx generated during combustion of pulverized coal is larger than NOx generated during combustion of gaseous fuel and liquid fuel, and therefore, it is desired to reduce the power of NOx.

NOx generated during combustion of various fuels is thermal (Tb
e rma 1 ) NOx and 7 x −x A/ (
Fue, l) NOx, thermal NO.
x is generated by the oxidation of nitrogen in the combustion air, and has a strong dependence on flame temperature (the higher the temperature, the greater the amount generated) - NOx is produced by nitrogen other than nitrogen in the fuel It is generated by the oxidation of NOx, and has a strong dependence on the oxygen concentration in the flame, and a temperature dependence on /J%.

Combustion methods that can suppress the generation of NOx include a multistage combustion method in which combustion air is divided into multiple stages and injected, and an exhaust gas recirculation method in which combustion exhaust gas with a low oxygen concentration is mixed into the combustion area. All of these low NOx combustion methods are aimed at suppressing the generation of thermal NOx by lowering the temperature of the combustion flame through low oxygen combustion.

However, between thermal NOx and 7UEL NOx,
It is thermal NOx that can suppress the amount of NOx generated by lowering the combustion temperature, and the amount of fuel NOx generated has little dependence on the combustion temperature.

Therefore, conventional combustion methods aimed at lowering the flame temperature are effective for combustion of gaseous fuels with low N content, but they are not suitable for pulverized coal fuels, where nearly 80% of the NOx generated is fuel NOx. Coal oil mixed fuel (abbreviated as COM) is a mixture of pulverized coal and heavy oil.
), coarse pulverized coal, mixed coal fuel (C
It has little effect on the combustion of oil water mixture (abbreviated as CWM).

On the other hand, the combustion mechanism of pulverized coal consists of a thermal decomposition process of pulverized coal in which volatile components are released, a combustion process of the released volatile components, and a combustion process of combustible solid components (hereinafter referred to as char) after thermal decomposition. Consists of processes.

The combustion rate of these volatile components is much faster than that of the solid components (volatile components are burned at the beginning of combustion. Also, in the pyrolysis process, the N content in the pulverized coal is also absorbed by other combustible components). Like other components, it is divided into those that are volatilized and released, and those that remain in the char.

Therefore, fuel NOx generated during pulverized coal combustion is
NOx from volatile N minutes and NO from N minutes in char
x, in 7 uel NOx, 7 from char
Since NOx is only generated when char is burned, NOx continues to be generated until the latter half of combustion, and countermeasures against this are an important point.

It is known that volatile N becomes compounds such as NH3 and HCN in the initial process of combustion and in the oxygen-deficient combustion region. In addition to reacting with oxygen to form NOx, these nitrogen compounds can also serve as reducing agents that decompose the generated NOx into nitrogen.

This NOx reduction reaction by nitrogen compounds proceeds in a system in which NOx coexists; in a reaction system in which NOx does not coexist, most of the nitrogen compounds convert to NOx.

Oxidized. Further, the generation of reducing substances progresses more easily in an atmosphere with a lower oxygen concentration.

As described above, an effective method for reducing NOx during combustion of pulverized coal is a combustion method in which a volatile nitrogen compound having reducing properties and NOx coexist, and the nitrogen compound reduces NOx to nitrogen.

In other words, a combustion method that eliminates the generated NOx and the NOx precursor by using a reducing nitrogen compound such as N (N) (3), which is a precursor of NOx, is effective for reducing NOx. It is.

Figure 1 shows the conventional combustion of heavy oil, COM, CST and pulverized coal.
Alternatively, it is a longitudinal cross-sectional view of a combustion device that performs co-combustion.

The pulverized coal burner is composed of a pulverized coal supply nozzle 2 that injects a mixed fluid of pulverized coal and primary air or pulverized coal and exhaust gas into a furnace 1, and a curved elbow 3. A splash plate 4 for changing the flow direction of the pulverized coal is arranged to form a pulverized coal fuel supply passage 5a, and in this pulverized coal fuel supply passage 5a, heavy oil, cod
A liquid such as a CWM burner and a mixed coal fuel supply passage 5b are arranged so that pulverized coal, heavy oil, COM, and CWM can be fired exclusively or mixedly.

The pulverized coal fuel supply passage 5a, liquid and mixed coal fuel supply passage 5b are arranged from the wind box 6 to the burner boat 8 of the furnace wall 7, and the inside of the wind box 6 is connected to a partition plate 9.
, 10, partitioned into an inner air passage 12 and an outer air passage 13 by an outer cylinder 11, and an inner air passage 12 and an outer air passage 1.
3 are provided with air vanes 14.15, and the passages 12, 13
control the amount of air.

In such a structure, the fuel from the pulverized coal fuel supply passage 5a or the liquid or mixed coal fuel supply passage 5b is injected into the furnace 1 from its tip, and is injected into the furnace 1 by the combustion air from the inner air passage 12 and the outer air passage 13. Burn.

However, in conventional combustion devices, even if the fuel from the pulverized coal fuel supply passage 5a or the liquid/mixed coal fuel supply passage 5b is attempted to be combusted at a low air ratio by the combustion air in the inner air passage 12, the outer air A part of the combustion air in the passage 13 is drawn in as combustion air, inhibiting the low air ratio at the root, and thereby making it impossible to achieve low NOx.

The present invention attempts to eliminate such conventional drawbacks,
The objective is to obtain a combustion device that can reduce NOx in exhaust gas and also reduce unburned content.

In order to achieve the above-mentioned object, the present invention provides a guide plate at the tip of the outer cylinder to rectify the air in the outer air passage to the outside, and causes the air flow in the outer air passage to swirl more strongly than the air flow in the inner air passage. A turning means was provided.

Embodiments of the present invention will be described below with reference to the drawings.

2 and 4 are longitudinal sectional views of the combustion apparatus of the present invention, and FIG. 3 is a perspective view illustrating the flow state of fuel and air in the combustion apparatus of the present invention.

In FIGS. 2 to 4, numerals 1 to 14 indicate the same parts as the conventional ones.

Reference numeral 16 denotes a guide plate disposed at the tip of the outer cylinder 11. This guide plate 16 rectifies the outside air of the outside air passage 13 more outward, and serves as an obstacle to lowering the air ratio of the combustion air to the burner root. It's also a board. Reference numeral 17 is a turning means, such as an air register, which applies a strong turning force to the outer air flow of the outer air passage 13, 18 is an operating rod for moving the outer cylinder 11 and the guide plate 16 forward and backward, and 19 is a handle.

In such a structure, the outside air in the outside air passage 13 in FIG. Ru.

In this way, the outside air in the outside air passage 13 is transferred to the guide plate 16.
Since the pulverized coal is injected into the furnace 1 while sucking a part of the inner air in the inner air passage 12, the base of the pulverized coal supply nozzle 3 has a high 02 area. As a result, NOx is generated from the N in the fuel and 02 is consumed, and the trailing end (tip) becomes a low 0□ region where 0□ is consumed, and in this low 02 region, reducing substances such as N1-13 are The above-mentioned NOx reacts with this reducing substance and is reduced to N2.

That is, as shown in FIG. 3, by strongly swirling the outside air by the swirling means 17 shown in FIG. 2, a swirling flow A is formed outward from the combustion apparatus as shown by arrow A.

A part of the inner air in the inner air passage 12 is sucked by this swirling flow A and becomes a negative pressure, and an inward circulating flow B is generated in the attenuating wake of the swirling flow.

On the other hand, at the base C of the pulverized coal supply nozzle 2, the inner air from the inner air passage 12 creates a high 02 region, and NOx
occurs. On the other hand, in the wake of the base C, the swirling flow A
A part of the inside air is sucked in by the swirling force of
Reducing substances such as H3 and HCN are generated.

Therefore, the NOx at the base C is mixed with the reducing substance at the downstream part by the circulating flow B, and the NOx is reduced to N2.

According to the combustion experiments conducted by the inventors, at the root C of the pulverized coal supply nozzle 2, the inner air is consumed by combustion and N
Ox increases, but as the amount of this inner air 00□ decreases, it is observed that the amount of reducing substances such as NH3 and HCN generated increases in the downstream area, and on the other hand, it is observed that as the amount of inner air 00□ decreases, the amount of reducing substances such as NH3 and HCN increases. It was observed that the flame holding effect at the root C of the pulverized coal supply nozzle 2 was also improved by expanding it outward by the plate 16.

FIG. 4 shows another embodiment of FIG. 2, in which the outer cylinder 11 and the guide plate 16 are moved forward and backward using the handle 19 and the operating rod 18 to move the outer cylinder 11 and the guide plate 16 forward and backward. The outward angle of the outside air is slightly adjusted, and the other explanations are the same as those shown in FIG.

In the case shown in Fig. 4, in addition to the above-mentioned fine adjustment of the outside air, when the combustion equipment is extinguished, the outer cylinder 11 and the guide plate 16 are moved back from the position shown by the solid line to the position shown by the dotted line to prevent burnout and damage. You can also do

Below, experimental data conducted by the present inventors will be introduced.

The table shows a coal-fired 1.5T/H combustion test furnace with a height of 16,000mm and a width of 3,000mm x 4,200mm (number of burners used: 1).
This is experimental data obtained by burning the combustion devices shown in FIGS.

Note that NOx, unburned content v Hair A/ (NOx is PP77
1-6%02 conversion, unburned content is unburned carbon wt% in ash
), the upstream pressure (static pressure) of the swirling means 17
was set to be 12 times the upstream side pressure (static pressure) of the air vane 14, and the inclination angle of the guide plate 16 was set to 20 to 90 degrees, and in the one shown in FIG. 4, the outer cylinder 11 and the guide plate 16 were slightly adjusted.

The concentration at the furnace outlet 02 at this time was 3.5 to 4.0%.

In the present invention, a guide plate is provided at the tip of the outer cylinder to rectify the air in the outer air passage to the outside, and a swirling means is provided in the outer air passage to swirl the air more strongly than the air flow in the inner air passage. It is possible to reduce NOx in the ash, prevent an increase in unburned content in the ash, and even existing combustion equipment can be easily modified.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a conventional combustion device, FIGS. 2 and 4 are vertical cross-sections of a combustion device according to an embodiment of the present invention, and FIG.
The figure is a perspective view illustrating the flow state of air in the combustion apparatus of the present invention. 5a, 5b...Fuel supply passage, 11...
...Outer tube, 12...Inner air passage, 13...
...Outside air passage, 16...Guidance plate, 17.
...Turning means. (Fig. 1, Fig. 2), Fig. 53, Fig. 4

Claims (1)

[Claims] An outer cylinder is provided on the outer periphery of the fuel supply passage to partition the fuel supply passage into an inner air passage and an outer air passage, and the fuel from the fuel supply passage is combusted by combustion air from the air passage. A combustion device characterized in that a guide plate is provided to rectify the air to the outside, and a swirling means is provided in the outer air passage to swirl the air more strongly than the air flow in the inner air passage.