JPH031565B2 - - Google Patents

Description

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

[Conventional technology]

Fluidized bed combustion furnaces are widely used as solid combustion furnaces because they can burn various solid fuels, but when solid fuels with poor combustibility are used, the combustion efficiency is significantly lower than that of pulverized coal combustion methods. It has the disadvantage of In a fluidized bed combustion furnace, air bubbles are generated from the surface of the fluidized bed, and as the air bubbles rise, some of the particles that fly out of the furnace are large in size, and the residence time in the furnace required for combustion is reached. If solid fuel with poor combustibility is used, the combustion efficiency will deteriorate rapidly.

In order to prevent the particles that are scattered along with the bubbles from being discharged outside the furnace, there is a method that uses a solid-gas separator to return the discharged particles to the furnace and re-burn them, but the particles that are scattered on the fluidized bed Since the structure is such that fuel particles are collected by a cyclone and circulated within the furnace, there is a large amount of fluidized medium and fuel particles scattered and circulated, which has the disadvantage of causing 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 amount of scattered particles in the combustion furnace, control the flow rate of particles collected and recirculated by the dust collector, and reduce the loss of ventilation power.
The present invention provides a fluidized bed combustion furnace that reduces wear on the furnace walls.

[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 tower part of the primary combustion chamber, and by changing the direction of the gas flow, coarse particles that are scattered along with air bubbles are fluidized. By returning it within the layer,
By reducing the particles contained in the combustion exhaust gas entering the precipitator to only fine particles and circulating the fine particles through the precipitator, loss of power due to particle circulation is reduced and wear on the furnace walls is prevented.

〔Example〕

Embodiments of the present invention will be described in detail based on the drawings. FIG. 1 shows an embodiment of the present invention, in which a fluidized bed combustion furnace 1 using a two-stage combustion method has a fluidized bed 2 and an empty column directly above the fluidized bed as a 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 of the empty column of the primary combustion chamber 3, and the secondary air supply port 5 is located at the furnace top 4a near the primary combustion chamber 3.
The combustion gas exhaust port 6 is placed on the side far from the primary combustion chamber 3, and the combustion gas rising inside the primary combustion chamber 3 is caused to flow upward by the secondary air. The air is guided downward into 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 combustion supply port 9 and burns the fuel present in the fluidized bed 2 .
The generated combustion gas rises inside the primary combustion chamber 3 accompanied by fuel particles and fluidized medium and reaches the ceiling 3a of the primary combustion chamber.
The air reaches the secondary combustion chamber floor surface 4b, is sucked in by the secondary air flow ejected toward the secondary combustion chamber floor surface 4b, descends while gently mixing with the secondary air, and reaches near the secondary combustion chamber floor surface 4b.

The coarse particles contained in the descending mixed gas collide with the floor surface 4b of the secondary combustion chamber, and further descend to form the fluidized bed 2.
However, after reaching near the floor 4 of the secondary combustion chamber, the fine particles change direction and are discharged out of 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 SO _x generated during combustion by using limestone as the fluid medium. . Although it is desirable to increase the collection efficiency of cyclone 10, the combustion of fuels with good combustibility (such as coal with high volatile content) and low S content may not require recirculation of the collected particles. be. 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). cyclone 10
The particles collected and recirculated are pulverized during the circulation process, and some are not collected by the cyclone 10 and are collected by the secondary cyclone, but there are also particles that are not sufficiently pulverized and are recycled. When the amount of particles circulated increases, the collection efficiency of the cyclone 10 decreases, so a collected particle discharge control valve 12 is provided that can discharge some of the particles collected by the cyclone 10 to the outside of the furnace.
will be established. 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 in 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. It has excellent features such as reducing power loss and furnace wall wear, and allowing the furnace top to be lowered.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the invention. 1...Fluidized bed combustion apparatus, 2...Fluidized bed, 3...
Primary combustion chamber, 4...Secondary combustion chamber, 5...Secondary air supply port, 7...Primary air supply port, 10...Cyclone, 11...Ejector.

Claims (1)

[Claims] 1 In a fluidized bed combustion furnace using a two-stage combustion method,
The fluidized bed and the empty tower directly above the fluidized bed are used as the primary combustion chamber, and a secondary combustion chamber with a secondary air supply port and a combustion gas exhaust port is provided on the side of the empty tower of the primary combustion chamber to reduce the amount of gas contained in the combustion exhaust gas. A fluidized bed combustion device characterized in that dust is removed by a dust collector, the removed dust is conveyed by secondary air, and is blown in together with the secondary air from a secondary air supply port provided in a secondary combustion chamber. .