JPH0238172Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a fluidized bed combustion apparatus, and in particular to a fluidized bed combustion apparatus that uses a fuel that produces a large amount of solid ash after combustion, such as coal or petroleum coke.

(Conventional technology) There is an urgent need to switch energy sources from oil, which has limited reserves, to coal, which has abundant resources. Coal has a higher sulfur content than petroleum and contains more ash, so it requires special care when handling it as a fuel. A fluidized bed combustion furnace is attracting attention as a combustion furnace for extracting energy from coal. In a fluidized bed combustion furnace, air for fluidization and combustion is supplied to the fluidized bed above it through an air distribution plate that forms the ceiling of an air chamber installed at the bottom of the furnace, forming a fluidized bed. The fluidized medium (composed of heat-resistant particles such as sand, cement clinker, etc., and in some cases may contain desulphurizing agent particles such as limestone) is fluidized as if it were boiling water, and It burns a supplied fuel such as coal particles. The height of the fluidized bed is about 50 to 100 cm,
Due to the large heat capacity of the high-temperature fluidized medium heated to 700-1000°C, it is possible to easily burn not only coal but also sludge with a high moisture content, flame-retardant EP ash, petroleum coke, etc.

When fuel is burned at a high temperature of 1000℃ or higher, the nitrogen and oxygen contained in the combustion air combine to produce nitrogen oxides (NOx). This creates a pollution problem.

Additionally, when burning fuel with a high sulfur content, limestone powder is mixed into the fluidized medium to remove sulfur oxides (SOx) produced during combustion, but this desulfurization reaction is To be effective, it is necessary to maintain the temperature of the fluidized bed between 850 and 1000°C.

For the above reasons, the fluidized bed temperature is set to 800~
It is common practice to maintain the temperature at 1000℃ and burn fuel such as coal. On the other hand, when burning coal particles, EP ash, etc. in a fluidized bed, fuel with small particle size is scattered from the fluidized bed to the upper part of the tower by gases such as fluidized air, and remains unburned. Carried into the flue by flue gases. In addition, the combustion of relatively large particles is also pulverized into small particles by fluidized combustion in a fluidized bed.
At a relatively low fluidized bed temperature of 1000°C, the particles are carried to the flue by flue gas through the empty column without being completely combusted.

Therefore, since the flue gas from the fluidized bed combustion equipment contains a large amount of unburned ash, the ash is separated using a cyclone type dust collector and this is maintained at a high temperature of about 1100°C. It is put into a combustion furnace to completely burn off the unburned matter, and it is turned into combustion ash that can be used as fly ash.

(Problems that the invention aims to solve) Conventionally, coal ash is separated from exhaust gas using a cyclone dust collector, is cooled and stored in an ash storage tank, and is then supplied to a reburning furnace. this is,
This is because the unburned carbon content in the ash is 30 to 40%, so there is a risk of combustion if the ash is transported or stored at a high temperature. However, burning the ash in a reburning furnace after cooling it is difficult because there is a large heat loss due to cooling, water is generally used as a coolant, but this utility is large, and it is difficult to use a cooler or to burn the ash after cooling. There were problems such as the high cost of equipment such as conveyors for transportation.

(Means for Solving the Problems) In order to solve the above-mentioned problems of the prior art, the present invention aims to store combustion ash collected by a cyclone dust collector using combustion exhaust gas that is lower temperature than the combustion ash. By cooling the ash while transporting it to a tank, the sensible heat of the ash is recovered into a carrier gas, and the thermal energy recovered by this carrier gas is used effectively in an air preheater or the like.

That is, the present invention includes a fluidized bed combustion furnace, a separator that separates solid ash from the combustion exhaust gas discharged from the furnace, and an air preheater that passes the exhaust gas from which the solid ash has been separated and recovers its thermal energy. In a fluidized bed combustion apparatus comprising an exhaust device for discharging the heat-recovered exhaust gas to the outside air, a bypass pipe is branched from the exhaust gas passage downstream of the separation device to bypass a part of the exhaust gas, and the exhaust gas is bypassed. The bypass pipe line includes an exhaust gas pressurization fan, and a pipe line that leads the pressurized exhaust gas to the ash removal device of the separation device.
A pipe line is provided for conveying the ash taken out from the ash extraction device using the exhaust gas and sending it to an ash tank, and a pipe line is provided for supplying the exhaust gas separated from the ash in the ash tank to the air preheater. It is characterized by:

(Embodiment of the invention) FIG. 1 is a system diagram of a fluidized bed combustion apparatus showing an embodiment of the invention. In the fluidized bed main combustion furnace 1, the air supplied from the air distribution plate 1b provided at the upper part of the air chamber 1a causes the fluidized medium above the air to form a fluidized bed 1c. The coal particles 12 supplied to the fluidized bed are burned in the bed and are entrained in the combustion exhaust gas through the empty column 1d and the flue 3a, and are collected by the cyclone dust collector 3 as ash containing unburned components. be done.

The combustion exhaust gas from which the ash content has been separated enters the air preheater 4 through the flue 3b. Here, the thermal energy of the exhaust gas is used to heat combustion air supplied to the main combustion furnace 1 and the reburning furnace 2. The combustion exhaust gas then enters an electrostatic precipitator 5 to collect and remove fine ash, and then passes through an induced draft fan 6 to the chimney 1.
3 is released into the atmosphere.

In the embodiment shown in FIG. 1, a part of the exhaust gas exiting the induced draft fan 6 is branched from the bypass 7a, is boosted in pressure by the boost draft fan 7, and reaches the bench lily type ash removal device 7d via the bypass 7b and the valve 7c. While taking out the ash stored in the hopper of the cyclone type dust collector 3, the ash is transported to the cyclone separator 8 via the pipe 8a.

After the ash is separated in the cyclone separator 8, the exhaust gas flows into the pipe line 8b. The ash separated by the cyclone separator 8 is stored in an ash tank 9.

Since the combustion exhaust gas leaving the booster ventilator has a low oxygen content, when the ash is transported from the ash removal device 7 through the pipe 8a, there is no risk of the ash being burned, and the ash tank 9 is also isolated from the air. , there is no risk of ash burning in the same tank.

In addition, the temperature of the combustion exhaust gas in the bypass 7b used for conveyance is 100 to 130°C, but the temperature is increased to about 200°C while conveying the high-temperature combustion ash, and in the flue 3b,
It merges with the exhaust gas flowing from the cyclone separator 3. This mixed gas heats the combustion air in the air preheater. This performs heat recovery.

In the above embodiment, the exhaust gas was bypassed after exiting the induced draft fan 6, but as shown by the dotted line in FIG. It is also possible to bypass the boost fan 7. The subsequent operation is similar to that of the previous embodiment. In this case, induced draft fan 6
Since the amount of exhaust gas passing through the ventilator is reduced, the ventilator can be made into a small-sized equipment.

In the embodiment shown in FIG. 1, in order to supply the ash stored in the ash tank 9 to the reburning furnace 2, the exhaust gas is supplied to the ash removal device 11b via a pipe line 11 branched from the bypass 7b and a valve 11a. , the ash in the ash tank 9 is fed to the reburning furnace 2 through a line 10.

FIG. 2 shows a configuration for replenishing the main combustion furnace 1 and the reburning furnace 2 with a fluidized medium. A part of the exhaust gas exiting the induced draft fan 6 is bypassed, and the pressure is increased by the pressure boost draft fan 7', and then supplied to the bench lily type fluidized medium extraction device 11b' through the pipe 11' and the valve 11a', where it is heated to room temperature. By conveying the fluidized medium with the exhaust gas from the smoke inlet via the pipes 10', 10a', 10b' to the main combustion furnace 1 and the reburning furnace 2, the fluidized medium is heated during the conveyance. Therefore, the thermal energy of the exhaust gas discharged from the chimney will be recovered accordingly, and if implemented in conjunction with the embodiment shown in FIG. 1, the heat recovery effect can be further promoted.

(Effects of the invention) By implementing the invention, it is possible to appropriately cool the ash discharged from the fluidized bed combustion equipment and recover its thermal energy, and to prevent the ash from being burned in the ash tank. .

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining one embodiment of the present invention, and FIG. 2 is an explanatory diagram of an implementation in which a fluidized medium is conveyed through a main combustion furnace and a reburning furnace using combustion exhaust gas. 1...Fluidized bed main combustion furnace, 2...Reburning furnace, 3
... Separation device, 4 ... Air preheater, 6 ... Induced draft fan, 7a, 7a', 7b ... Exhaust gas bypass pipe, 7 ... Boosting draft fan, 7d ... Ash removal device of separation device, 8 ...Ash hopper ash separation device, 8a
...Ash conveyance pipe, 8b...Exhaust gas pipe, 9...
Ash tank, 10...Ash conveyance pipe, 12...Fuel supply device, 13...Chimney.

Claims (1)

[Scope of utility model registration request] A fluidized bed combustion furnace, a separator that separates solid ash from the combustion exhaust gas discharged from the furnace, an air preheater that passes the exhaust gas from which the solid ash has been separated and recovers its thermal energy, and an air preheater that recovers the heat energy. In a fluidized bed combustion apparatus comprising an exhaust device for discharging waste gas to the outside air, a bypass pipe for bypassing a part of the exhaust gas is branched from an exhaust gas passage downstream of the separator, and the bypass pipe is provided with a bypass pipe for bypassing a part of the waste gas. A booster ventilator, a pipe line that leads the pressurized exhaust gas to the ash removal device of the separation device, and a pipe line that transports the ash taken out from the ash removal device with the exhaust gas and sends it to the ash tank, A fluidized bed combustion apparatus, further comprising a pipe line for supplying exhaust gas separated from ash in the ash tank to the air preheater.