JPH07151307A - Ash conveyor for fluidized bed combustion device - Google Patents

Abstract

PURPOSE:To convey ash, collected from exhaust gas of a fluidized bed combustion device through an ash-collecting facility, safely to a bag filter. CONSTITUTION:The exhaust gas of combustion is employed as gas for conveying ash without employing a part of combustion air such as in a conventional method. For this purpose, high-temperature and high-pressure exhaust gas in an inlet port for a gas turbine 15 is employed after cooling it by a heat exchanger 25 to the low-temperature and low-pressure exhaust gas in the outlet port of the gas turbine 15 is employed after pressurizing it by a compressor 29. The exhaust gas of combustion, in which the concentration of oxygen is extremely low, is employed whereby the spontaneous combustion of unburnt fuel contained in ash in an ash collecting facitlty 14 and the like will never be worried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed combustion apparatus, and more particularly to a conveying and cooling facility for combustion ash such as a pressurized fluidized bed boiler using a fluidized bed form.

[0002]

2. Description of the Related Art In a fluidized bed combustion apparatus, a predetermined amount of particles (referred to as fluidized material) are charged and stored in a fluidized bed combustion furnace (vertical furnace).
The particles move up and down to form a fluidized bed. The in-furnace flow velocity forming this fluidized bed is called superficial velocity, and the amount of combustion per unit area of the fluidized bed can be increased at the same superficial velocity as at atmospheric pressure by applying pressure in the combustion furnace. .

FIG. 2 is a system diagram showing an example of a conventional fluidized bed combustion apparatus. In this figure, a fluid material is charged in advance in the combustion furnace (1), and a heat transfer tube (3) in which a heating medium is flowing is inserted and mounted in the fluid material (2). . Combustion air supplied from an air compressor (5) driven by an electric motor (4) or the like through a combustion air duct (6) passes through a plenum chamber (7) and a perforated plate (8) to a combustion furnace (1). ), The air is jetted into the interior of the container and fluidizes the fluid material (2).

On the other hand, a high temperature gas generated in a high temperature gas generating furnace (not shown) is directly sent into the fluidized material (2) and the fluidized material (2) is heated to a temperature higher than the ignition temperature of a fuel such as coal, and then the fuel The solid fuel such as coal in the storage hopper (9) is supplied by the feeder (1
0), and supply into the fluid material (2) through the supply pipe (11). Then, spontaneous combustion starts and the fluid material is heated to a higher temperature, so that the supply of the high temperature gas from the high temperature gas generating furnace is stopped. In this state, the heat generation amount of the fuel and the heat absorption amount of the heat transfer tube (3) are adjusted to appropriately maintain the temperature of the fluid material (2).

Further, the combustion gas reaches the ash collection facility (14) through the freeboard (12) and the exhaust gas duct (13). Then, after removing the combustion ash that has carried over together with the combustion gas, it is sent to the gas turbine (15) to drive it. As a result, the air compressor (5) and the generator (not shown) are driven, so that the electric motor (4) is stopped. The output of the gas turbine (15) increases as the amount of fuel increases, and the amount and pressure of combustion air sent from the air compressor (5) increase to reach a predetermined value, resulting in a steady operation state. The combustion gas is decompressed and reduced in temperature by driving the gas turbine (15), and then heat is recovered by a heat exchanger or the like and released to the atmosphere.

On the other hand, the combustion ash collected by the ash collecting facility (14) is cooled by the carrier air supplied through the ash carrier air duct (16) branched from the combustion air duct (6) to a cooling pipe. After being conveyed and cooled through (17), the sensible heat of the ash is recovered and then pressure-fed to the bag filter (18). Then, the pressure is further reduced by the pressure reducing line (19), and the ash dispenser (2
It is discharged to the atmosphere through 0). The valves (21), (2
In 2) and (23), pressure adjustment such as opening / closing or pressure reduction is performed as necessary.

[0007]

The above-mentioned conventional fluidized bed combustion apparatus has the following problems to be solved. That is, as described above, the fluidized material (2) is operated in the combustion furnace (1) at a constant superficial velocity that does not carry over, but the fuel injected into the combustion furnace (1) is completely combusted. Carry over with the combustion ash to the outside of the combustion furnace (1). And about 10 is contained in the ash collected by the ash collection facility (14).
% Or less is included as unburned component. Further, the combustion ash and the unburned fuel are in a high temperature state because heat is not recovered. However, since the oxygen concentration is extremely low, it is temporarily stored in the ash collection facility (14) without ignition. However, when fresh combustion air having a high oxygen concentration is supplied as a gas for transporting ash in such a state, the unburned component in the ash comes into contact with it and spontaneously ignites. The generated heat may cause troubles such as burnout of the ash collecting equipment or explosion of unburned components in the ash in a locally high-concentration atmosphere to damage the equipment.

[0008]

In order to solve the above conventional problems, the present invention cools and conveys combustion ash discharged from a fluidized bed combustion furnace together with combustion gas and collected by an ash collecting facility. In the thing, a part of the combustion gas is cooled,
This is used as a gas for carrying the combustion ash, and an ash carrier for a fluidized bed combustion apparatus; and a combustion ash discharged from a fluidized bed combustion furnace together with combustion gas and collected by an ash collecting facility. Characterized in that the above-mentioned combustion gas is allowed to work, a part of the same combustion gas after the work is pressurized, and this is used as a gas for carrying the combustion ash. The ash carrier of the ash carrier of the fluidized bed combustor is proposed.

[0009]

In the present invention, the combustion gas having an extremely low oxygen concentration is used as a carrier gas for carrying the combustion ash discharged from the fluidized bed combustion furnace together with the combustion gas and collected by the ash collection facility while cooling. Therefore, there is no risk of spontaneous combustion of unburned fuel in the combustion ash. In the first solving means, since the high temperature combustion gas is cooled and used, there is no fear of burning the ash collecting equipment or the ash conveying equipment.

In the second solving means, the combustion gas is caused to work, and a part of the combustion gas whose pressure is reduced / decreased thereby is used as the carrier gas.
There is no risk of equipment burnout, and since pressure is used, the pressure required for ash transportation is secured.

[0011]

FIG. 1 is a system diagram showing an embodiment of the present invention. In this figure, the parts similar to the conventional one described with reference to FIG.
The same reference numerals are given and detailed description thereof is omitted.

In this embodiment, the gas turbine (1
The first exhaust gas extraction duct (24) is branched from the inlet of 5), a heat exchanger (25), a container (26) and an exhaust gas supply duct (27) are provided, and the exhaust gas supply duct (2) is provided.
7) is connected to the ash carrying air duct (16). Further, the second exhaust gas extraction duct (28) is branched from the outlet of the gas turbine (15), a compressor (29) is further provided, and it is connected to the container (26) through the duct (30).

Since the unburned content, that is, carbon (char), increases the exothermic reaction rate in proportion to the oxygen concentration, in the present embodiment, in order to reduce the oxygen concentration of the air for transporting ash, oxygen is replaced with fresh air. It uses combustion exhaust gas with extremely low concentration for ash transportation. However, a certain pressure difference (head) is required to convey ash in the cooling pipe (17).
is necessary. In a pressurized fluidized bed in which the inside of the combustion furnace (1) is pressurized to, for example, about 10 kg / cm ² g, the gas turbine (15)
Since the combustion exhaust gas at the inlet has a sufficiently high pressure but is also at a high temperature, there is no commercially available shut-off valve capable of withstanding it, and it is not possible to extract it and use it as it is for ash transportation.

Therefore, in this embodiment, the gas turbine (1
5) Part of the high temperature combustion exhaust gas extracted at the inlet to the first exhaust gas extraction duct (24) is subjected to heat recovery by the heat exchanger (25) and then stored in the container (26). In an emergency where there is a risk of exothermic reaction due to spontaneous combustion, the internal pressure of the combustion furnace (1) is immediately reduced to create a pressure difference with the inside of the container (23), and the air is sent via the ash carrying air duct (16). The flue gas in the container (26) is mixed with the supplied air, or alternatively, it is used for ash transportation. In the present embodiment, the combustion exhaust gas is extracted from the decompressed / cooled portion of the gas turbine (15) outlet to the second exhaust gas extraction duct (28), and the compressor (29).
After pressurizing with, it is fed to the container (26) via the duct (30). As a result, the pressure of the combustion exhaust gas contained in the container (26) can be further increased with a small amount of gas. The valves (31) and (32) are opened and closed as necessary to adjust the pressure. Thus, without lowering the internal pressure of the combustion furnace (1), it is possible to continuously carry and cool ash by using combustion exhaust gas having an extremely low oxygen concentration instead of combustion air having a high oxygen concentration, Therefore, it is a safe ash carrier that does not cause spontaneous combustion of unburned matter in the combustion ash.

[0015]

[Table 1]

Now, when the size of the container (26) and the amount of extracted exhaust gas are calculated on the basis of the condition [I] shown in [Table 1], the result is [II].

[0017]

According to the present invention, the following effects can be obtained. 1) By using inactive combustion exhaust gas with extremely low oxygen concentration for transportation and cooling of ash, exothermic reaction of unburned matter in ash is avoided and troubles caused by combustion loss of ash cooling equipment are prevented. it can.

2) The high-temperature and high-pressure combustion exhaust gas is extracted from the gas turbine inlet and cooled to be used for transportation, and the low-temperature low-pressure exhaust gas is extracted from the gas turbine outlet to be pressurized and used. It is only commensurate with the pressure loss required for transportation and other pressure losses. Therefore, the compressor capacity can be remarkably small as compared with the case where the total amount of the carrier gas is increased from normal pressure.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram showing an example of a conventional fluidized bed combustion apparatus.

[Explanation of symbols]

(1) Combustion furnace (2) Fluid material (3) Heat transfer tube (4) Electric motor (5) Air compressor (6) Combustion air duct (7) Plenum chamber (8) Perforated plate (9) Fuel storage hopper (10) Supply machine (11) Supply pipe (12) Freeboard (13) Exhaust gas duct (14) Ash collection facility (15) Gas turbine (16) Ash transport air duct (17) Cooling pipe (18) Bag filter (19) Decompression Line (20) Ash dispenser (21), (22), (23) Valve (24) First exhaust gas extraction duct (25) Heat exchanger (26) Container (27) Exhaust gas supply duct (28) Second Exhaust gas extraction duct (29) Compressor (31), (32) valve

Claims (2)

[Claims] 1. A method for transporting a combustion ash discharged from a fluidized bed combustion furnace together with combustion gas and collected by an ash collection facility while cooling the combustion gas, wherein a part of the combustion gas is cooled and the combustion ash is cooled. An ash carrier for a fluidized bed combustor characterized by being used as a carrier gas. 2. A method for transporting a combustion ash discharged from a fluidized bed combustion furnace together with combustion gas and collected by an ash collection facility while cooling the combustion ash, causing the combustion gas to work, and then performing the same combustion. An ash carrier for a fluidized bed combustion apparatus, wherein a part of gas is pressurized and used as a gas for carrying the combustion ash.