JPH0618017A - Combustor - Google Patents

Abstract

PURPOSE:To provide a combustor of high combustion efficiency by which unburnt component contained in oombustion exhaust gas in a slight amount can be combusted so completely that rednction of NOX can be realized. CONSTITUTION:The conbustor is formed of a fluidized bed 1, a free board part 2 positioned above the bed 1, and an after furning zone 3 which is a high temperature zone where unburnt gas component is comtusted. At a connection part 4 for the free board part 2 and the after burning zone 3, a cross sectional area AB at an entrance of the after burning zone 3 and another cross sectional area AF at the free board part 2 satisfy the following expression: AF/AB>=2.5. the combustor supplies tertiary air to the entrance of the after furning zone 3 for the purpose of supplying air used for mixing, stirring and combusting unburnt gas component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus for incinerating municipal waste, industrial waste, etc., which can prevent the generation of minute amounts of harmful substances such as dioxins and can perform combustion with high combustion efficiency. It is about.

[0002]

2. Description of the Related Art In recent years, due to the diversification of physical distribution systems and the like, the amount of plastics, fibers, papers and the like has increased in urban wastes, and the municipal wastes have a tendency to gradually increase in calories. During incineration of plastics, there are some cases in which refractory materials are damaged by local high-temperature heat generation, clinker is generated, and continuous operation of the furnace and incineration of the rated amount of garbage are prevented, so that plastics are sorted as unsuitable for incineration. . However, it is difficult to completely separate the plastics from the waste, and if the separated plastics are landfilled, a valuable energy source is also landfilled.

[0003] As a burning device for municipal wastes that have high calorie content, a burning device equipped with a fluidized bed furnace is drawing attention.

[0004]

The combustion mechanism of solid matter is as follows:
Combustion is completed through a process of evaporating and drying water, a process of thermally decomposing solid matter, and a process of combusting pyrolysis product gas and product char. In the case of a fluidized bed furnace, the evaporation / drying process of water and the thermal decomposition process of solid matter are carried out within a short time. Therefore, in the case of incineration of municipal refuse whose properties are not constant, the amount of produced gas varies. For this reason, the residence time of the combustible gas in the furnace is temporarily reduced. As a result, a small amount of unburned components is generated. This is particularly noticeable in plants of medium scale or smaller.

On the other hand, in the conventional fluidized bed furnace, two-stage combustion is performed, but even in this two-stage combustion, the remaining amount of combustion air is supplied to the freeboard section, so there is a limit to NOx reduction.

The present invention has been made in view of the above points, and provides a combustion device having a high combustion efficiency capable of completely burning a small amount of unburned components contained in combustion exhaust gas and achieving low NOx. With the goal.

[0007]

In order to solve the above-mentioned problems, the combustion apparatus of the present invention comprises a fluidized bed section, a freeboard section located above the fluidized bed section, and a post-combustion which is a high temperature region for burning unburned gas components. And a region.

The above-mentioned combustion apparatus is characterized in that the cross-section area A _B at the post-combustion area inlet and the cross-section area A _{F at the} freeboard part satisfy the following equation at the connection portion between the freeboard section and the post-combustion area. . A _F / A _B ≧ 2.5

Further, the combustion apparatus is characterized in that tertiary air is supplied to the inlet of the after-combustion region for the purpose of supplying air for mixing / stirring and combustion of unburned gas components.

Further, the combustion apparatus is characterized in that the freeboard portion is provided with a mixing and stirring means constituted by arranging a large number of pipes having air injection holes.

Further, the combustor is characterized in that the amount of primary air blown from the bottom of the fluidized bed of the fluidized bed incinerator is set to be equal to or less than the theoretical amount of air so that the combusted material is slowly combusted in the fluidized bed. .

Further, in the combustion apparatus, secondary air is blown into the freeboard portion to make a high temperature oxidizing atmosphere with an air ratio of 1.0 to 1.5, and further tertiary air is blown into the post combustion area inlet, It is characterized in that the air ratio in the post combustion region is 1.5 or more.

[0013]

According to the present invention, by constructing the combustion apparatus as described above, the tertiary air is supplied to the post-combustion region, whereby the mixing and stirring of the combustion gas is promoted, and as a result, the combustion efficiency is improved.

Further, by providing the post-combustion region, the residence time of the combustion gas in the high temperature region can be sufficiently secured, and the combustion efficiency of unburned components is improved.

Further, since the air ratio in the freeboard portion is small, the cooling effect due to excess air can be reduced, and the freeboard portion can be heated to a high temperature. As a result, combustion efficiency is improved.

Further, by supplying air in three stages of primary air, secondary air, and tertiary air, NOx reduction can be achieved.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the structure of a combustion apparatus of the present invention.
1A is a vertical cross-sectional view, and FIG. 1B is a side view seen from the direction of arrow A. The combustion device is a fluidized bed 1 surrounded by a furnace wall.
And a freeboard portion 2 located above it and a post-combustion region 3 which is a high temperature region where the unburned gas component is burned. Further, the connection portion 4 between the freeboard portion 2 and the post-combustion region is shaped to be eccentric with respect to the freeboard portion 2 for the purpose of promoting mixing and stirring of combustion exhaust gas. The average retention time of the combustion exhaust gas is set within the range of 2 to 4 seconds in the freeboard section 2 and 1 to 3 seconds in the post combustion area 3 and the connecting section 4.

A wind box 5 for supplying primary air 7 is provided at the bottom of the fluidized bed 1, and a fluidized bed is formed at the top of the wind box 5. Secondary air supply ports 8 and 9 are provided in the furnace wall 6 of the freeboard unit 2. At the connecting portion 4 between the freeboard portion 2 and the post combustion region 3, the post combustion region 3
The cross-sectional area A _{B at} the entrance portion of and the cross-sectional area A _{F at the} freeboard portion 2 satisfy the following equation. A _F / A _B ≧ 2.5

A dust supply port 10 is provided on the furnace wall 6 of the freeboard section 2. Furthermore, a tertiary air supply port 11 is provided at the inlet of the post combustion region 3, and by supplying the tertiary air from the tertiary air supply port 11, the combustion gas is mixed and stirred. The upper portion of the post combustion region 3 is connected to the exhaust gas outlet 12. The operation of the combustion device having the above structure will be described below.

As described above, the burning of the solid matter includes (1) the evaporation and drying steps of water, (2) the pyrolysis step of the solid matter,
(3) Combustion is completed through a combustion process of pyrolysis product gas and product char. The dust is supplied from the dust supply port 10 into the fluid medium (sand) of the fluidized bed 1 having a high temperature and a uniform temperature. The combustible substances contained in the garbage are (1) above,
Since the three steps of (2) and (3) are performed, it can be said that there are no combustible substances in the residue discharged from the bottom of the fluidized bed 1.

However, since the above-mentioned two steps (1) and (2) are performed in a short time, in the case of city refuse whose properties are not constant, it appears as a fluctuation of the produced gas. As a result, the oxygen concentration required for combustion in the furnace fluctuates. That is, there is a problem that the combustion air (oxygen) becomes excessive and the combustion temperature lowers, or conversely, oxygen becomes insufficient and is released into the atmosphere as unburned. Further, due to the shape of the furnace, gas mixture, etc., the oxygen distribution in the furnace becomes uneven, and as a result, unburned components are contained in the exhaust gas.

In order to solve this problem, in the present combustion device,
A post-combustion region 3 is provided above the freeboard unit 2.
By providing the post-combustion region 3, (1) rectifying action at the inlet part, (2) mixing action by tertiary air inflow from the tertiary air supply port 11 at the inlet part, (3) post-combustion in the high temperature region By ensuring the exhaust gas retention time in the region 3, a diffusion combustion action can be expected.

In the present combustion apparatus, the high temperature region (combustion region) is divided into three regions of the fluidized bed portion 1, the freeboard portion 2 and the post combustion region 3 and each of them operates in a sharing role. The operating condition criteria in each of the fluidized bed section 1, the freeboard section 2 and the afterburning zone 3 are set as follows.

(1) Criteria for setting the temperature range a) The temperature of the fluidized bed 1 is preferably low in order to make the gasification rate of dust slower, and in this embodiment, the upper limit was set to 700 ° C. . On the other hand, the lower limit is governed by the gasification temperature of the substances that make up municipal waste. Complete gasification,
It is important that the amount of incombustibles burned off is extremely small.
Most of the thermal decomposition temperatures of the substances that compose the municipal waste such as paper and plastic are 400 ° C. or lower, and in this example, the lower limit was set to 600 ° C. with a sufficient margin. b) The upper limits of the temperatures of the freeboard section 2 and the post-combustion region 3 are set to 950 ° C. in order to suppress the generation of thermal NOx and prevent the dust problem due to fly ash. On the other hand, the lower limit was set to 800 ° C or higher in order to secure a good combustion state.

(2) Criteria for setting the air ratio a) Air ratio of the fluidized bed section 1 {Supply air quantity: Minimum air quantity (theoretical air quantity) required for combustion of combustion products}, that is, from the bottom of the fluidized bed section 1 The upper limit of the amount of primary air to be blown was set to an air ratio of 1 or less in order to cause partial combustion of dust. On the other hand, the lower limit is set to the amount of air required to fluidize the fluidized medium. b) The air ratio of the freeboard portion 2 enables high temperature combustion, and at the same time, the air ratio is 1.0 to 1.
The high temperature oxidizing atmosphere in the region 5 was set. c) The air ratio in the post combustion region 3 is an amount necessary for completing the combustion of a small amount of unburned components, and by blowing the tertiary air from the tertiary air supply port 11 at the inlet of the post combustion region 3, The air ratio in the combustion area 3 is set to 1.5 or more.

Preheating of Secondary Air and Tertiary Air The secondary air and the tertiary air supplied from the secondary air supply ports 8 and 9 and the tertiary air supply port 11 complete the combustion efficiently and therefore maintain the temperature and agitate. It needs to be done. In this embodiment, the secondary air supply ports 8 and 9 and the tertiary air supply port 1
By preheating the secondary air and the tertiary air supplied from No. 1, the internal temperature of the freeboard section 2 and the post combustion region 3 was raised, and the combustion gas was stirred by the secondary air and the tertiary air. In addition, by preheating the secondary air, it is possible to burn high-temperature dust even with low heat value, and prevent overcooling by secondary air due to fluctuations in the amount of combustion gas due to fluctuations in the amount of dust supplied and changes in dust properties. Yes, stable combustion can be secured.

FIG. 2 is a view showing another structure of the combustion apparatus of the present invention, FIG. 2 (A) is a longitudinal sectional view, and FIG. 2 (B) is a side view seen from the direction of arrow A. The present combustion apparatus is composed of a fluidized bed portion 1 surrounded by a furnace wall, a freeboard portion 2 located above the fluidized bed portion 1, and a post combustion region 3 which is a high temperature region for burning unburned gas components. It is the same as the combustion device of No. 1. This combustion apparatus is different from the combustion apparatus of FIG. 1 in that a large number of pipes 13 having air injection holes are arranged side by side on the freeboard portion 2. This improves the mixing and stirring action of the combustion gas in the freeboard section 2.

[0028]

As described above, according to the present invention, the following excellent effects can be expected. (1) By supplying the tertiary air to the post-combustion region, mixing and agitation of combustion gas are promoted, and as a result, combustion efficiency is improved. (2) By providing the post-combustion region, the residence time of the combustion gas in the high temperature region can be sufficiently secured, and the combustion efficiency of unburned components is improved. (3) Since the air ratio in the freeboard portion is small, the cooling effect due to excess air can be reduced, and the freeboard portion can be heated to a high temperature. As a result, combustion efficiency is improved. (4) The NOx reduction can be achieved by supplying air in three stages of primary air, secondary air, and tertiary air.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of a combustion apparatus of the present invention.
1A is a vertical cross-sectional view, and FIG. 1B is a side view seen from the direction of arrow A.

FIG. 2 is a diagram showing another structure of the combustion apparatus of the present invention.
FIG. 2A is a vertical sectional view, and FIG. 2B is a side view seen from the direction of arrow A.

[Explanation of symbols]

 1 Fluidized Bed Part 2 Freeboard Part 3 Post-Combustion Area 4 Connection Part 5 Air Box 6 Furnace Wall 7 Primary Air 8 Secondary Air Supply Port 9 Secondary Air Supply Port 10 Dust Supply Port 11 Tertiary Air Supply Port 12 Exhaust Gas Exhaust Port 13 Pipe with air injection holes

Front page continuation (72) Inventor Mitsutoshi Yamamoto 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo Inside EBARA CORPORATION

Claims (6)

[Claims] 1. A combustion apparatus comprising a fluidized bed portion, a freeboard portion located above the fluidized bed portion, and a post-combustion region which is a high temperature region for burning unburned gas components. 2. The cross-sectional area A _{B at the} inlet of the post-combustion region and the cross-sectional area A _{F at the} freeboard portion of the connection portion between the freeboard portion and the post-combustion region satisfy the following equation. The combustion device according to 1. A _F / A _B ≧ 2.5 3. The combustion apparatus according to claim 1, wherein tertiary air is supplied to the inlet of the post-combustion region for the purpose of supplying mixing / stirring and combustion air of unburned gas components. 4. The combustion apparatus according to claim 1, wherein the freeboard portion is provided with a mixing and stirring means configured by arranging a large number of pipes having air injection holes. . 5. The method according to claim 1, wherein the amount of primary air blown from the bottom of the fluidized bed is made equal to or less than the theoretical amount of air, and the fluidized bed is made to perform slow partial combustion. The combustion device according to any one of claims. 6. Secondary air is blown into the freeboard section to create a high temperature oxidizing atmosphere with an air ratio of 1.0 to 1.5, and further tertiary air is blown into the post combustion region inlet, thereby The combustion apparatus according to claim 3, 4 or 5, wherein the air ratio in the combustion region is 1.5 or more.