JPH06249409A - Pressurized fluidized bed boiler - Google Patents

Abstract

PURPOSE:To prevent agglomeration of medium particles in a medium vessel and return transfer of medium particles from the medium vessel to change of load for accurate adjustment. CONSTITUTION:A pipe arrangement making use of draft conveyance so as to extract a fluid medium from a burner reactor 1 into a medium vessel 11 comprises a moving bed descending downpipe 21 connected at its one end to a fluidized bed section 50 in the burner reactor for causing the fluid medium to descend and move, a draft conveyance pipe 23 connected between the other end of the moving bed descending downpipe 21 and a void space 13 of the medium vessel 11 for conveying the fluid medium upward by means of draft, and a fluidized bed 50 provided at a lower portion of the draft conveyance pipe 23 for burning an unburned fuel. With this arrangement, a residence time, in which medium particles and unburned coal particles remain in the fluidized bed 50, is increased to promote combustion of the unburned coal particles. Accordingly, an excessive temperature rise from the medium in the medium vessel 11 is prevented to eliminate melting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized fluidized bed combustion furnace for coal that drives gas turbines and steam turbines to perform combined power generation, and particularly to prevent melting and solidification of a medium in a medium container which is necessary when the load changes. The present invention relates to a pressurized fluidized bed combustion furnace equipped with the fluidized bed height control device.

[0002]

2. Description of the Related Art In a pressurized fluidized bed combustion furnace, the fluidized bed height can be increased or decreased to respond to load changes. That is, in order to reduce the load, the fluidized medium in the combustion furnace is extracted from the furnace and stored in a separate medium container. Supply to
The amount of steam generated is changed by changing the burial depth of the heat transfer tube arranged in the combustion furnace by the fluidized medium and increasing or decreasing the heat transfer area. Conventionally, for example, Japanese Patent Laid-Open No. 1-271010
No. 8 discloses that in order to extract the fluidized medium from the inside of the combustion furnace to the medium container, one end is opened at the bottom of the fluidized bed combustion furnace and the other end is penetrated into the combustion furnace empty tower part to The dust separator is provided with a suction conduit for the fluidized medium, which connects the fluidized bed combustion furnace and the medium vessel, and the medium vessel is connected to the external space of the pressurized vessel whose pressure is lower than that of the fluidized bed combustion furnace and a conduit having a valve. The connected means are shown. By adjusting and opening the valve of the conduit connecting the storage container and the external space in the above means, the pressure in the adjusting container becomes lower than that in the combustion furnace, and the fluidized medium flows through the suction conduit together with the gas in the combustion furnace into the medium in the furnace. It is extracted into the container.

However, according to the above publication, there is a problem that the fluidized medium is melted and agglomerated in the medium container. This is because the unburned coal particles contained in the fluidized medium are filled in the medium container, and the concentration of the fluidized medium and the oxygen concentration from the conduit at the bottom of the medium container provided for supplying the fluidized medium to the combustion furnace It is estimated that the high gas flows back into the medium container, the unburned coal particles burn intermittently in the container, the temperature rises excessively, and the fluid medium melts.
In particular, in the medium container, the medium particles and the unburned coal particles are stored for a long time in the state of the fixed bed, so that the temperature may be partially increased.

From such a background, in order to prevent the flowing medium and the gas having a high oxygen concentration from flowing back into the medium container from the conduit in the lower portion of the medium container, the inventors of the present invention, as shown in FIG. A pressurized fluidized bed boiler has been proposed in which the extracting and transferring means is a combination of a moving bed and an air flow phase (Japanese Patent Laid-Open No. 4-110509, etc.). In this pressurized fluidized bed boiler, a fluidized bed downcomer 21 for medium particles is provided in the fluidized bed 3 of the combustion furnace 1 in the pressure vessel 101 by opening. Further, the lower end of the moving bed downcomer 21 is connected to the empty tower section 1 of the medium container 11.
An air flow transport pipe 23 having an upward flow of gas for transporting medium particles is formed by connecting to a hole 3 and the medium particles are intended to be transported by a moving layer of a downward flow due to gravity and a gas flow phase due to a gas flow transport gas. .

However, the above inventions of the present inventors also have a problem that the fluidized medium is melted and agglomerated in the medium container 11. This is because the fluid medium and the gas having a high oxygen concentration flow back into the medium container from a conduit provided in the lower portion of the medium container, which is provided for supplying the fluid medium to the combustion furnace, as described in JP-A-1-217108. Although it does not happen, the amount of unburned coal particles contained in the fluidized medium fills the medium container without decreasing. As a result, it is estimated that the unburned coal particles burned intermittently in the medium container and the temperature rose excessively to melt the fluidized medium. In order to avoid the melting and solidification of the medium particles in the medium container 11 as described above, a method of supplying an inert gas such as nitrogen gas into the medium container 11 is adopted.

[0006]

In the above pressurized fluidized bed boiler of the prior art, there is no solution to the problem that the fluidized medium melts and agglomerates in the medium container 11. Therefore, an object of the present invention is to prevent the agglomeration of the medium particles in the medium container and to accurately control the transfer of the medium particles from the medium container with respect to the load change speed. Is to provide.

[0007]

The above object of the present invention can be achieved by the following constitutions. That is, in the pressurized fluidized bed combustion boiler in which the height of the fluidized bed of the combustion furnace is changed and the load is controlled by extracting the fluidized medium into the medium container and returning the fluidized medium from the medium container, It is a pressurized fluidized bed boiler provided with a fluidized bed section for flowing a fluidized medium by an air flow as a part of a piping system utilizing air flow transportation for extracting into a container. Here, the piping system utilizing the air flow for extracting the fluidized medium of the combustion furnace into the medium container may have any configuration, but the fluidized medium, one end of which is connected to the fluidized bed portion of the combustion furnace, moves while descending. A moving bed downcomer, an airflow transport pipe for transporting a fluidized medium connected between the other end of the moving bed downcomer and the empty column portion of the medium container while rising by an airflow, and The fluidized bed portion for burning the fuel can be used.

[0008]

The unburned coal particles in the medium particles are combusted in the fluidized bed portion, which is a part of the piping system utilizing the air flow for extracting the fluidized medium of the combustion furnace into the medium container, and remain in the medium container. The amount of burning coal particles can be significantly reduced. This is because in the fluidized bed portion, the residence time of the concentration of the medium particles and the unburned coal particles increases, so that the combustion of the unburned coal particles is promoted. As a result, the amount of unburned coal particles in the medium particles transferred to the medium container is reduced, and the medium in the medium container is prevented from excessively rising in temperature and melting.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. The apparatus of this embodiment shown in FIG. 1 comprises a fluidized bed combustion furnace 1 and a medium container 1.
1, a cyclone 41, a medium transport pipe according to the present invention, a pressure vessel 101 accommodating equipment, and the like. The fluidized bed combustion furnace 1 is provided with a dispersion plate 2 for introducing combustion air 8 at the bottom thereof, on which a fluidized bed 3 filled with a fluidized medium is provided.
Is formed. The fluidized medium in the fluidized bed 3 generates bubbles 7 by the combustion air 8 supplied through the dispersion plate 2 to form the fluidized bed 3 in the combustion furnace 1. The coal 10 supplied into the fluidized bed combustion furnace 1 by the coal feeding pipe 9 is combusted in the combustion furnace 1. Since the heat transfer tubes 4 are arranged in the fluidized bed combustion furnace 1, the combustion heat of the coal 10 is absorbed to generate steam in the heat transfer tubes 4.

A moving bed downcomer pipe 21 is provided at the bottom of the side wall of the fluidized bed combustion furnace 1 by opening, and the moving bed downcomer pipe 21 is extended vertically from an inclined state to form an L-shaped valve 22, It is connected to the fluidized bed section 50 for removing the coal particles. Aeration gas 19 is supplied to the L valve 22 via the control valve 20. At the upper part of the fluidized bed portion 50, an air flow transport pipe 2 for transporting medium particles to the medium container 11
3 is connected. Further, a dispersion plate 51 is installed at the bottom of the fluidized bed portion 50, and a fluidized bed of medium particles and unburned coal particles is formed on the dispersion plate 51. From the lower part of the dispersion plate 51, air 24, which serves both for fluidization and air flow transportation, is adjusted by a control valve 25 and supplied.

On the other hand, the lower end of the medium container 11 is squeezed into a conical shape to form the moving bed tube 14, and the moving bed tube 14 is the L valve 1.
An open hole is connected to the bottom of the side wall of the fluidized bed combustion furnace 1 via 5. Aeration gas 17 is supplied to the L valve 15 via a control valve 18. Medium container 1
In 1, a fluidized medium extracted from the fluidized bed combustion furnace 1 is accumulated. Further, the combustion furnace empty column section 6 and the medium container empty column section 13 are connected by a conduit 31 provided with a valve 32. Further, a cyclone 41 is connected to the combustion furnace empty column section 6 so that fine particles in the combustion gas are removed and supplied as clean gas 44 to a gas turbine (not shown) in the next step. The separated fine particles are discharged to the outside of the system through the conduit 42.

In the above apparatus, the pressure of the combustion furnace 1 is 10 to 20 atm, the combustion temperature is 800 to 900 ° C., and the superficial gas velocity of the combustion furnace 1 is 0.5 to 1.5 m / s. It Maximum diameter of 3 as desulfurizing agent in fluidized medium and fluidized bed
Limestone particles of about mm are used. Then, the steam generation amount can be controlled in this apparatus as follows. For example, the fluidized bed 3 in the combustion furnace 1 is the heat transfer tube 4
The fluidized medium in the combustion furnace 1 is withdrawn from the medium 5 at a height 5 at which all the groups are buried and drawn out to the medium container 11 through the moving bed downcomer 21, the L valve 22, the fluidized bed section 50, and the air flow transport pipe 23, and transferred. The height of 3 is reduced to the 5'position,
A part of the group of heat transfer tubes 4 is exposed from the fluidized bed 3, and the heat transfer area of the heat transfer tubes 4 buried in the fluidized bed 3 is reduced, so that the steam generation amount can be reduced.

At this time, only the unburned coal particles are combusted while the medium particles and the unburned coal particles in the fluidized bed portion 50 are fluidized by the air 24 for fluidization and air flow transportation. The temperature in the fluidized bed section 50 is 800 to 900 ° C. because the medium particles flowing from the fluidized bed combustion furnace 1 are at a high temperature. As a result, the unburned coal particles contained in the medium particles are in the fluidized bed portion 50.
The medium particles, which are easily burned inside and the unburned coal particles are reduced, are guided from the upper part of the fluidized bed section 50 to the air flow transport pipe 23 and further transferred into the medium container 11. Here, the gas flow velocity in the air flow transport pipe 23 is usually 5 to 20 m / s, and the superficial velocity in the fluidized bed section 50 is 0.5 to 1.5 m / s.

As described above, the unburned coal particles contained in the medium container 11 are 0.1% by weight or less, and the ratio of unburned coal particles can be 10% or less as compared with the conventional system.
As a result, the temperature of the medium particles does not locally rise in the medium container 11, and the trouble of melting and solidifying the medium particles can be eliminated. On the contrary, when the fluidized bed 3 in the combustion furnace 1 is at the height 5 ', the fluidized bed in the medium container 11 is moved to the moving bed tubes 14, L.
By increasing the height of the fluidized bed 3 to a certain level by returning the heat transfer tube 4 group to the combustion furnace 1 through the valve 15, the heat transfer area of the heat transfer tube 4 is increased to increase the amount of steam generated as desired. be able to.

[0015]

According to the present invention, the problem of the melting and solidification of the medium in the medium container is solved, and the amount of the inert gas can be reduced, so that the utility cost can be reduced, and the pressurized fluidized bed boiler with reliability can be reduced. Will be provided.

[Brief description of drawings]

FIG. 1 is a structural diagram showing a pressurized fluidized bed combustion furnace according to an embodiment of the present invention.

FIG. 2 is a structural diagram showing a prior art pressurized fluidized bed combustion furnace.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fluidized bed combustion furnace, 2, 51 ... Dispersion plate, 3, 12 ... Fluidized bed, 4 ... Heat transfer tube, 6 ... Combustion furnace empty tower part, 10 ... Coal, 11
... medium container, 13 ... medium container empty tower part, 14 ... moving bed tube,
17, 19 ... Aeration gas, 21 ... Moving bed downcomer pipe, 23 ... Airflow transport pipe, 41 ... Cyclone, 50 ... Fluidized bed section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kodai Nonaka 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory (72) Masataka Ogasawara 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Stock Company Kure Factory (72) Inventor Katsuya Oki 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory

Claims (2)

[Claims] 1. A pressurized fluidized bed combustion boiler in which the height of the fluidized bed of a combustion furnace is changed by extracting the fluidized medium into the medium container and returning the fluidized medium from the medium container to control the load, A pressurized fluidized bed boiler, comprising a fluidized bed portion for flowing a fluidized medium by an air flow as a part of a piping system utilizing air flow for extracting the medium into a medium container. 2. A piping system utilizing an air flow for extracting a fluidized medium of a combustion furnace into a medium container, and a moving bed downcomer for moving the fluidized medium, one end of which is connected to the fluidized bed portion of the combustion furnace, while moving the fluidized medium down. An air flow transport pipe that transports a fluid medium that is connected between the other end of the moving bed downcomer pipe and the empty column part of the medium container while rising by an air flow, and a flow that burns unburned fuel provided below the air flow transport pipe. The pressurized fluidized bed boiler according to claim 1, comprising a bed portion.