JPS62190309A - Fluidized bed combustion device having secondary combustion chamber - Google Patents

Abstract

PURPOSE:To decrease incurring of a power less and to prevent wear of a furnace wall, by a method wherein a secondary combustion chamber is formed to return coarse particle, by which bubbles are accompanied, is returned to the interior of a fluidized bed through change in the direction of a gas flow, and only fine particle is circulated by means of a dust collector. CONSTITUTION:Produced combustion gas is raised, in a state to be accompanied by fuel particle and a fluid medium, within a primary combustion chamber 3 up to a primary combustion chamber ceiling 3a, and is sucked by means of an injected secondary air flow and lowered down to a position in the vicinity of a secondary combustion chamber floor surface 4b. Coarse particle contained in air-fuel mixture is further lowered back to the interior of a fluidized bed 2. After fine particles are lowered down to a position in the vicinity of the floor surface 4b, they change the direction and are discharged in a manner to be carried on the flow of combustion gas destined for a combustion gas exhaust port 6. The fine particles are collected by a cyclone 10, sucked by means of an ejector 11, and returned to a secondary air feed port 5. As noted above, since only the fine particles are circulated, incurring of a power less and wear of a furnace wall can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-stage combustion device in a circulating fluidized bed combustion furnace.

[Prior art] Fluidized bed combustion furnaces can burn various solid fuels, so
Although it is widely used as a solid combustion furnace, it has the disadvantage that the use of solid fuel with poor combustibility significantly reduces combustion efficiency compared to the pulverized coal combustion method. In a fluidized bed combustion furnace, bubbles are generated from the surface of the fluidized bed, and as the bubbles rise, some of the particles that fly out of the furnace are large in size, and the residence time in the furnace necessary for combustion is reached. Therefore, if solid fuel with poor combustibility is used, the combustion efficiency will deteriorate rapidly.

In order to prevent particles that fly with air bubbles from being discharged outside the furnace, a solid air valve 1! There is a method that uses a device to return the discharged particles to the furnace and re-burn them, but since the structure is such that the particles scattered on the fluidized bed are collected by a cyclone and circulated inside the furnace, the fluidized medium and fuel particles are The disadvantage is that there is a lot of scattering and circulation, and there is a large amount of wear on the walls of the furnace and dust collector, and a large loss of ventilation power.

[Purpose of the invention]

The purpose of the present invention is to reduce the flow rate of scattered particles in the combustion furnace, control the flow rate of particles collected and recirculated by the dust collector, and reduce loss of ventilation power and wear on the furnace wall. The present invention provides a fluidized bed combustion furnace.

(Structure of the Invention) In order to achieve the above object, the fluidized bed combustion furnace of the present invention is provided with a secondary combustion chamber on the side of the empty column of the primary combustion chamber, and removes coarse particles that are scattered along with air bubbles into a waste stream. By changing the direction and returning it to the fluidized bed, the particles contained in the combustion exhaust gas entering the precipitator are reduced to only fine particles.By circulating the fine particles in the precipitator, power loss due to particle circulation is reduced. This prevents wear on the furnace walls.

(Example) An example of the present invention will be described in detail based on the drawings. 1st
The figure shows an embodiment of the present invention. In a fluidized bed combustion furnace 1 using a two-stage combustion method, the fluidized bed 2 and the empty tower section directly above the fluidized bed are used as the primary combustion chamber 3, and the empty tower section of the primary combustion chamber 3. A secondary combustion chamber 4 having a secondary air supply port 5 and a combustion gas discharge port 6 is provided on the side, and the secondary air supply port 5 directs the secondary air downward to the furnace top 4a near the primary combustion chamber 3. The combustion gas outlet 6 is placed on the side far from the primary combustion chamber 3, and the combustion gas rising in the primary combustion chamber 3 is diverted from an upward flow to a downward flow by a secondary air flow. The fuel is guided to the secondary combustion chamber 4 for secondary combustion.

Combustion air supplied from the primary air supply port 7 through the air distribution plate 8 is supplied from the fuel supply port 9 and burns the fuel present in the fluidized bed 2 . The generated combustion gas rises in the primary combustion chamber 3 accompanied by fuel particles and a fluidized medium, reaches the primary combustion chamber 3 well 3a, and is sucked by the secondary air flow jetted toward the secondary combustion seedbed surface 4b. , it descends while gently mixing with the secondary air and reaches near the floor surface 4b of the secondary combustion chamber.

Coarse particles contained in the descending mixed gas collide with the secondary combustion chamber floor surface 4b and further descend to return to the fluidized bed 2, but fine particles reach near the secondary combustion chamber floor surface 4b and then change direction. The combustion gas is discharged outside the furnace along with the combustion gas flow toward the combustion gas discharge port 6. Since the particles discharged outside the furnace include unburned particles, they are collected by a cyclone 10 installed near the furnace exhaust port, and the collected particles are sucked by an ejector 11 and returned to the secondary air supply port 5. . The purpose of returning the particles collected by the cyclone 10 into the furnace is to increase the combustion efficiency of the furnace and to increase the removal efficiency when removing SOx generated during combustion by using limestone as the fluid medium. It is desirable to increase the collection efficiency of cyclone 10, but if the combustibility is good (such as coal with a high volatile content),
Combustion of small amounts of fuel may not require recirculation of trapped particles. Therefore, it is necessary to change the collection efficiency of the cyclone 10 depending on the target fuel, and to collect particles that cannot be collected by the cyclone 10 using a secondary cyclone (not shown). Particles collected and recirculated by the cyclone 10 are pulverized during the circulation process, and the particles collected by the cyclone 10 are
Some particles are not collected by the secondary cyclone, but some particles are not sufficiently pulverized and are recycled. As the amount of particles circulated increases, the collection efficiency of the cyclone 10 decreases, so a collected particle discharge control valve 12 is provided to discharge part of the particles collected by the cyclone 10 to the outside of the furnace. The particles collected by the cyclone 10 are carried by the secondary air and sent to the secondary air supply port 5, but it is necessary to improve the contact with the secondary air in the furnace and to reach the temperature in the furnace quickly. Therefore, it is desirable to supply the air in a distributed manner within the furnace and to use preheated air.

〔effect〕

In the above fluidized bed combustion apparatus, a secondary combustion chamber is provided on the side of the primary combustion chamber, and the exhaust gas is collected in a dust remover installed near the furnace exhaust port at the secondary air supply port located inside the secondary combustion chamber. By sending particles and performing recirculation combustion, coarse particles can be easily separated in the furnace, and by recirculating only fine particles, compared to conventional circulating fluidized bed combustion furnaces that also circulate coarse particles. Figure 1 is a longitudinal sectional view of an embodiment of the present invention.

1) Fluidized bed combustion equipment 2) Fluidized bed 3) Primary combustion chamber 4) Secondary combustion chamber 5) Secondary air supply port a) Primary air supply port 10) Cyclone 11) Ejector Patent applicant: Director of the Agency of Industrial Science and Technology, etc. ↑

Claims (1)

[Claims] (1) In a fluidized bed combustion furnace using the two-stage combustion method, the fluidized bed and the empty column directly above the fluidized bed are used as the primary combustion chamber, and the secondary air supply port and the combustion gas exhaust port are located on the sides of the empty column of the primary combustion chamber. A secondary combustion chamber is provided, the dust contained in the combustion exhaust gas is removed by a dust collector, the removed dust is transported by secondary air, and the dust is transported from the secondary air supply port provided in the secondary combustion chamber. , a fluidized bed combustion apparatus characterized in that it is blown in together with secondary air.