JPH04366307A - Supplying method for secondary air in burner - Google Patents

Abstract

PURPOSE:To suppress the generation of reaction products in a combustion device such as a furnace, etc., by providing uniform distribution of the flow (flow rate, temperature) of the combustion gas and at the same time making the time of its stay longer in order to bring complete combustion. CONSTITUTION:Secondary air is supplied to generate a rotating air flow that rotates round an imaginary center line (a) that intersects the direction of the combustion gas flow 9 perpendicularly in an intermediate. position between the section where the primary combustion is made and the section where the combustion gas is generated in a combustion device (furnace 1).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying secondary air to a combustion apparatus such as a waste incinerator.

0002

BACKGROUND OF THE INVENTION A conventional method for supplying secondary air to a furnace as a combustion device includes four surfaces of the furnace walls 2 and 3 surrounding the combustion gas flow in the furnace 1, as shown in FIGS. 7 and 8. Alternatively, some of the nozzles 12a to 12d that inject air at a certain angle to the gas flow are arranged in combination.

In this case, as shown in FIGS. 7 and 8, when giving a swirling flow to the secondary air, the secondary air flows in a horizontal direction perpendicular to the main stream 9 of combustion gas rising in the furnace 1. The nozzles 12d are arranged on the furnace walls 2 and 3 in almost the same horizontal plane so that the flow of secondary air (indicated by the arrow in FIG. They are made eccentric in opposite directions with respect to the center.

Therefore, in this conventional secondary air supply method, the virtual center line of the swirling flow of the secondary air, indicated by reference numeral 14 in FIG. 8, coincides with the direction of the main stream 9 of the combustion gas. .

[0005]

Problems to be Solved by the Invention In combustion devices such as furnaces, if combustion control is incomplete, problems such as generation of harmful substances due to generation of unreacted substances and reduction in combustion efficiency occur. Temporal changes in the properties of the combustible material (hereinafter referred to as fuel)
In stoker furnaces for waste incineration, which have significant spatial fluctuations and are likely to generate organic chlorine-based hazardous substances, even if stoker combustion is performed, most of the volatile matter in the fuel remains in the empty column within the combustion equipment. Since a combustion reaction takes place, secondary air is usually supplied. If this secondary air is supplied to high-temperature parts, unburned gas (carbon monoxide, etc.) and unreacted harmful substances (organic chlorine compounds) can be removed.
can suppress the generation of nitrogen oxides (NOx
) increases. In addition, the secondary air is transferred to the low temperature section (near the furnace outlet).
Although it is possible to suppress the oxidation reaction at high temperatures and control the generation of NOx, the high-temperature residence time of the combustion gas in the furnace until combustion is completed is insufficient, resulting in the generation of unburned gas and unreacted harmful Increase in substances is inevitable.

The above-mentioned problems are caused by the fact that the various conventional secondary air supply methods all focus on oxygen diffusion (stirring effect) in the combustion region. In order to solve this problem, a method of giving a swirling flow to the secondary air flow as shown in FIGS. 7 and 8 has been adopted.

However, although the conventional secondary air supply shown in FIGS. 7 and 8 is effective to some extent in extending the residence time of combustion gas in the furnace, Since the virtual center lines of the swirl flow coincide with each other, it is inevitable that the distribution of gas flow (flow rate, temperature) in the furnace will be non-uniform.

The present invention aims to provide a method for supplying secondary air in a combustion device that can solve the above problems.

[0009]

[Means for Solving the Problems] A method for supplying secondary air in a combustion device according to the present invention is such that combustion gas in the combustion process flows through the combustion device, which has a portion for performing primary combustion and a portion serving as an outlet for the combustion gas. Secondary air is supplied to an intermediate region between the two ends so as to generate an air flow that swirls around an imaginary center line perpendicular to the flow direction of the combustion gas in the combustion process.

0010

[Operation] In the present invention, by supplying secondary air, an air flow is generated that swirls around an imaginary center line perpendicular to the flow direction of combustion gas in the combustion process.

[0011] This prevents uneven distribution of gas flow (flow rate, temperature) within the combustion device, and
The swirling air flow provides sufficient oxygen diffusion and also increases the effective residence time of the combustion gases.

[0012] Therefore, in the combustion device, secondary combustion with a long effective residence time is carried out in a state where the gas flow is uniformly distributed and oxygen is sufficiently diffused, achieving complete combustion and eliminating unreacted substances. Generation of substances is suppressed.

[0013]

Embodiment A first embodiment of the present invention will be explained with reference to FIG. The present embodiment is a vertical type having a stoker 8 in the lower part for burning solid materials such as garbage, the combustion gas flows upward in the furnace 1 having a rectangular cross section, and the combustion gas is discharged from the outlet 11 in the upper part. This relates to the furnace 1. Secondary air ports 4, 5 and 6, 7 are provided at vertically spaced intervals near the outlet 11 of the opposing front wall 2 and rear wall 3 of the furnace 1, respectively. As shown by arrows in FIG. 1, secondary air is injected diagonally downward from the upper secondary air ports 4 and 6, and diagonally upward from the lower secondary air ports 5 and 7. It looks like this.

[0014] The secondary air flows from the air ports 4 and 7 are almost parallel, and are located approximately in the center of the front wall 2 and the rear wall 3 and are parallel to both walls 2 and 3. It is in contact with an imaginary circle centered on line a extending in the horizontal direction. Further, the secondary air flows from the air ports 5 and 6 are also substantially parallel to each other, and are in contact with an imaginary circle centered on the line a. Note that the lower portion of the rear wall 3 of the furnace 1 is inclined obliquely backward as it goes upward.

In this embodiment, the stoker 8 at the bottom of the furnace 1
Primary combustion takes place in the furnace 1, and the main stream 9 of combustion gas flows upward in the furnace 1. On the other hand, since the secondary air is injected into the furnace 1 from the secondary air ports 4 and 5 of the front wall 2 and the secondary air ports 6 and 7 of the rear wall 3 as described above, it is not part of the main flow of combustion gas. A swirling flow 10 is generated macroscopically with the orthogonal horizontal line a as the virtual center. This swirling flow 10 flows downward near the front wall 2 and upward near the rear wall 3, as shown by the arrows.

In this way, by generating the swirling flow 10 around the horizontal line a perpendicular to the main stream 9 of combustion gas by the flow of secondary air, the gas flowing inside the furnace 1 is There is no unevenness in the flow distribution, and the residence time of combustion gas in the furnace is increased.
Furthermore, secondary combustion of the combustion gas takes place in a sufficiently diffused state of secondary air, ie, oxygen. As a result, the combustion gas is completely combusted and is discharged from the upper outlet 11.

Furthermore, in this embodiment, since the secondary air is supplied to a relatively low temperature region near the outlet 11, the generation of NOx can be suppressed.

Furthermore, in the furnace 1 of this embodiment, in the main stream 9 of combustion gas when secondary air is not used, the maximum flow velocity and gas temperature appear at the front of the furnace 1, as shown in FIG. Most of the reaction gas passes through the front of the furnace at high speed, and a portion reaches the furnace outlet 11 as unreacted substances, is rapidly cooled, and is discharged as is. By introducing secondary air that forms the swirling flow 10 having the velocity distribution as shown in FIG. 2, the combined flow of combustion gas approaches a uniform flow velocity as shown in FIG. In combination with the swirling effect, the effective residence time in the furnace will be extended.

Furthermore, in this embodiment, the secondary air port 4
By optimally selecting the amount and penetration power of the secondary air supplied from 7 to 7, it is possible to control the flow pattern of the main combustion gas 9 in the furnace, and to separate the primary combustion gas containing a large amount of unburned gas from the secondary air. The relative velocity difference with the next air can be made large,
Secondary combustion is promoted.

A second embodiment of the present invention will be explained with reference to FIG. In this embodiment, in the first embodiment, the secondary air port 5 of the front wall 2 is omitted, and the interval between the secondary air ports 6, 7 of the rear wall 3 is slightly expanded. is located at a height between the secondary air ports 6 and 7, and the front wall 4
The secondary air is injected horizontally from the secondary air port 4.

[0021] This embodiment also provides the same functions and effects as those of the first embodiment.

A third embodiment of the present invention will be explained with reference to FIG. In this embodiment, the secondary air port 6 of the rear wall 3 is omitted in the first embodiment, and the secondary air port 6 of the rear wall 3 is placed between the secondary air ports 4 and 5 of the front wall 2. The secondary air outlet 6 is located at a height of , and secondary air is injected horizontally from the secondary air opening 6 in the rear wall 3.

[0023] In this embodiment as well, the same functions and effects as in the first embodiment can be achieved.

Although the furnace in each of the above embodiments is equipped with a stoker, the present invention can be applied to a furnace without a stoker. Further, the fuel used is not limited to solid fuel, but may be liquid fuel or gaseous fuel. Furthermore, the present invention is not limited to the vertical furnace as in the embodiment described above, but can also be applied to other types of combustion apparatus, such as a horizontal type.

[0025]

Effects of the Invention The present invention uses secondary air to generate an air flow in the primary combustion gas that swirls around a virtual center line perpendicular to the flow direction of the combustion gas. The distribution of gas flow (flow rate, temperature) can be made uniform, oxygen can be sufficiently diffused, and the effective residence time of combustion gas can be increased.

[0026] As a result, the primary combustion gas can be sufficiently secondary-combusted to achieve complete combustion, and the generation of unreacted substances can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment of the invention.

FIG. 2 is a distribution diagram of secondary air flow velocity in the same example.

FIG. 3 is a distribution diagram of primary combustion gas flow velocity in the same example.

FIG. 4 is a distribution diagram of composite flow velocity in the same example.

FIG. 5 is a longitudinal sectional view of a second embodiment of the invention.

FIG. 6 is a longitudinal sectional view of a third embodiment of the invention.

FIG. 7 is a longitudinal sectional view of a conventional furnace.

FIG. 8 is a horizontal sectional view of the conventional furnace.

[Explanation of symbols]

1 Furnace 2 Front wall 3
Rear wall 4, 5, 6, 7 Secondary air port 8 Stoker 9
Main combustion gas 10
swirl flow

Claims (1)

[Claims] Claim 1: In a combustion device having a part that performs primary combustion and a part that serves as an outlet for combustion gas, in an intermediate region between the two end parts through which the combustion gas in the combustion process flows, there is provided a part in the flow direction of the combustion gas in the combustion process. A method for supplying secondary air in a combustion device, comprising supplying secondary air so as to generate an air flow that swirls around a virtual center line perpendicular to .