JPS63187011A - Low nox combustion apparatus - Google Patents

Abstract

PURPOSE:To achieve both low NOx generating and complete combustion simultaneously by a method wherein the combustion of unburnt part is carried out after the completion of denitration reaction by securing sufficient time until flames come in contact with the tertiary air. CONSTITUTION:The secondary and tertiary air are transferred respectively to an air preheater by a forced air blower and the part of the air flows into a secondary air passage through an inlet hole 11 for the secondary air of which opening is controlled by a slidable damper 9 and after revolving force is provided by a secondary vane 12, the air is spouted into the furnace inside from a secondary jet hole 13. The remaining air is provided with revolving force by a tertiary air resister 15 and spouted into the furnace inside from a tertiary jet hole 16. In this case, a spacer ring 17 with sufficient thickness (d) is installed and its end part is so constituted as to be expanded outside the axial center of the spacer ring. The tertiary air is spouted around the circumference of flames with a fixed space to the flames. The sufficient time to denitrate in the flames is secured and the flames finishing denitration comes in contact with the tertiary air at the downstream part of the flames to carry out complete combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combustion device, and particularly to a combustion device that reduces the amount of nitrogen oxides in combustion exhaust gas.

[Conventional technology]

Nitrogen oxides (hereinafter referred to as rNOxJ) mixed in combustion equipment exhaust gas
) are air pollutants, and various technologies have been developed to reduce their emissions as much as possible. As one method for reducing NOx, a method has been implemented in which NOx is reduced during the combustion stage. This method divides the supply of air into several stages, and initially performs combustion in a low oxygen state to suppress the generation of NOx and to reduce the amount of NOx generated.
x performs gas-phase reduction using reducing substances generated by this low-oxygen combustion, and furthermore, by supplying sufficient oxygen downstream of this gas-phase reduction zone, complete combustion of unburned matter is achieved. ing.

In other words, the denitrification reaction (reduction reaction) in a flame is performed using air (oxygen).
The oxidation reaction proceeds with an extremely small amount of NOx, and if sufficient air is supplied to the denitrification reaction zone, the oxidation reaction will proceed, resulting in an increase in NOx. Taking these points into account when considering the amount of air supplied, the normal low NO
In the x-burner, the weight ratio of primary air and fuel (pulverized coal) is about 2:1 to 1:1, and combustion is performed in an extremely insufficient amount of air. Next, the secondary air is set to about 1/3 to 115 of the tertiary air supply amount, and a part of the pulverized coal is combusted by this secondary air to maintain a high temperature state. This low oxygen + high temperature condition causes the denitrification reaction to proceed.

Therefore, preventing mixing of tertiary air until the denitrification reaction is completed is a prerequisite for highly efficient low NOx combustion.

[Problem that the invention seeks to solve]

Conventionally, pulverized coal transported by airflow is injected from a burner nozzle, the air for transporting the pulverized coal is used as primary air, and a flame-holding member such as a flame-holding ring is provided around the primary nozzle where the pulverized coal is injected. The flame is stabilized and secondary air and tertiary air are injected and supplied around the flame.

In this case, by applying a strong swirling force to the secondary air and tertiary air, the flow direction of the air is limitedly controlled, thereby delaying the mixing with the flame. Therefore, in order to obtain a strong turning force, a powerful blower is required, resulting in an increase in internal power. In addition, with small-scale burners, it is difficult to apply a strong swirling force to the airflow, and it is also difficult to secure sufficient furnace space, so even if sufficient swirling force can be secured, it is difficult to apply a strong swirling force to the air flow. Achieving NOx reduction is difficult, and if conventional configurations were continued, NOx reduction, especially in small-scale burners, tended to be insufficient.

[Means for solving problems]

The present invention has been constructed to solve the above-mentioned problems, and the biggest reason for the reduction in NOx is that the tertiary air for complete combustion is not sufficiently separated, and the denitrification reaction is not completed before the denitrification reaction is completed. Tertiary air mixes, resulting in low or insufficient NOx,
This structure is designed in consideration of the fact that NOx may increase in some cases.

That is, a spacer ring having a predetermined wall thickness is arranged concentrically with respect to a sleeve that injects and supplies fuel so as to share the center axis thereof, and a secondary air nozzle and a tertiary air nozzle are formed separately.

[Effect]

A spacer ring is arranged concentrically with the sleeve that injects and supplies fuel so as to share its center axis, and a secondary air nozzle and a tertiary air nozzle are formed separately, and the spacer ring is arranged concentrically with the sleeve that injects and supplies fuel. By supplying secondary air around the flame caused by the pulverized coal injected at This secures the time necessary for denitrification, and furthermore, the contact between the flame and tertiary air downstream of the flame burns the unburned content in the flame and achieves complete combustion.

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

1 and 2 show a first embodiment of the invention.

Reference numeral 14 in the figure is a partial sleeve for injecting and supplying pulverized coal to the furnace, and an oil supply pipe 2 is disposed within the sleeve 14 so as to share the central axis.
A swirler 6 is installed for applying swirling force to the pulverized coal flow carried by the primary air. 5
is a venturi portion formed in the circumferential direction of the inner circumferential wall of the sleeve 14. Further, 20 is a flame holding plate partially attached to the furnace side end of the sleeve 14, and 7 is a primary nozzle for pulverized coal injection formed by this flame holding plate 20.

Reference numeral 10 denotes a secondary sleeve partially disposed between the annular space formed between the sleeve 14 and the opening of the furnace wall 19. Next, reference numeral 17 denotes a spacer ring arranged to be fitted onto the outer circumference of the secondary air sleeve 10. This spacer ring 17 has a predetermined thickness d compared to the secondary sleeve 10, so that the flame and the tertiary air can be separated well as will be described later. That is, by arranging the spacer ring 17, a space having an annular cross section formed by the inner circumference of the spacer ring 17 and a part of the outer circumference of the sleeve 14 can be used as a secondary air passage, and the outer circumference of the spacer ring 17 and the furnace wall opening. The space between them is defined as a tertiary air passage, and the furnace-side ends of each passage are defined as a secondary nozzle 13 and a tertiary nozzle 16, respectively. The furnace side end of the spacer ring 17 is formed into a substantially truncated conical shape so as to diffuse outward at a predetermined angle with respect to its central axis, thereby delaying the contact between the injected air, especially the tertiary air, and the flame. ing.

In the above configuration, first, upon startup, the oil fuel 1 is sprayed from the nozzle tip 3 of the oil supply pipe 2 to start combustion,
When the temperature inside the furnace rises to a level suitable for pulverized coal combustion, the combustion is switched to pulverized coal and the supply of oil fuel is stopped. Pulverized coal is supplied either directly from the crushing device or once stored in a pulverized coal bin, as a mixture 4 with conveying air (primary air), its flow is adjusted in the venturi 5 part of the secondary sleeve 14, and then the swirler 6 gives a swirling force, and is injected into the furnace, where it is combusted. In this case, approximately 1 to 3 times the weight of the pulverized coal to be conveyed is used as conveying air and as primary air for combustion. Here, the calorific value of coal is 6500 to 7000 kcal/k
g, the theoretical air amount is 8 to 8.5 kg/1 kg of coal.
It will be about. Therefore, the amount of primary air supplied is extremely insufficient for coal combustion, and in the furnace, combustion is first performed in an extremely air-deficient state.

On the other hand, each of the secondary and tertiary air is sent to an air preheater (none of which is shown) by a forced blower, and after being heated to about 300°C, a wind box consisting of a furnace wall 19 and a wind box wall 8 18
supplied within. A part of this flows into the secondary air passage through the secondary air intake 11 whose opening area is adjusted by the slide damper 9, and after being given a swirling force by the secondary vane 12, from the secondary nozzle 13 to the furnace. Inject inside. The remaining air is given a swirling force by the tertiary air register 15 and is injected into the furnace from the tertiary nozzle 16.

In this case, a spacer ring 17 having a sufficient thickness d is installed, and the ends of the spacer ring are configured to diffuse outward from the axis of the spacer ring, so that the tertiary air is kept at a certain distance from the flame. spray around the flame. Therefore, sufficient time can be secured for denitration within the flame, and in the downstream part of the flame, the flame that has completed denitration comes into contact with tertiary air, resulting in complete combustion. In the above configuration, since the tertiary air is well separated from the flame by the spacer ring 17, it is not necessary to apply a strong swirling force, and therefore a powerful blower is not required.

FIG. 3 shows a second embodiment.

In this embodiment, the external taper angle β of the truncated conical portion (hereinafter referred to as “tapered portion”) at the end of the spacer ring 17 is thicker than the internal taper angle α. This allows for better separation from the air.

FIG. 4 shows a modification of the above embodiment.

In this modification, a rounded portion 23.24 is formed in which the transition from the spacer ring 17 main body to the tapered portion is smoothly formed.
This allows the secondary and tertiary air to flow more smoothly.

〔effect〕

As specifically shown in the embodiments, the present invention has a spacer ring having a predetermined wall thickness arranged concentrically with respect to a sleeve for injecting and supplying fuel so as to share its central axis. Sufficient time can be secured for the flame and tertiary air to come into contact, and unburned matter is combusted after the denitrification reaction is completed, making it possible to achieve both low NOx and complete combustion at the same time.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a pulverized coal combustion device showing a first embodiment of the present invention, FIG. 2 is a front view of the combustion device shown in FIG. 1, and FIG. 3 is a spacer showing a second embodiment. FIG. 4 is a vertical cross-sectional partial view of a spacer ring showing a modification of the second embodiment.

Claims (3)

[Claims] (1) In a combustion device configured to supply secondary air and tertiary air from around a sleeve that injects and supplies fuel together with primary air, a spacer ring having a predetermined wall thickness is installed around the sleeve that injects and supplies fuel. Low NOx characterized by being arranged concentrically and having a tertiary nozzle for injecting tertiary air separated from a primary nozzle for injecting fuel.
Combustion device. (2) A truncated conical tapered portion is formed at the furnace side end of the spacer ring so as to diffuse outward from its axis.
Ox combustion device. (3) The low NOx combustion device according to claim (2), wherein the outer taper angle of the tapered portion is formed to be larger than the inner taper angle.