JPH07293819A - Pressurized fluidized bed type boiler and its load controlling method - Google Patents

Abstract

PURPOSE:To provide an accurate adjustment of a particle taking-out amount of fluidized medium from a fluidized bed type combustion furnace in response to a load changing speed. CONSTITUTION:A flow speed of fluidized medium particles or gas in a fluidized bed down comer 12 is governed by a differential pressure per unit length in the fluidized bed down comer 12 and a differential pressure between a medium container 2 and a combustion furnace 1. These differential pressures are detected by differential pressure meters 16, 30, thereby it is possible to know a taking-out amount per unit time from the combustion furnace 1. for the fluidized medium particles in the fluidized bed through sensing of these differential pressures. Then, an amount of aeration gas 15 is adjusted or a differential pressure between the combustion furnace 1 and the medium container 2 is adjusted by a pressure reducing valve 20, thereby a taking-out amount per unit time of fluidized medium particles can be adjusted to a predetermined set amount. In the case when the taking-out amount of the fluidized medium particles cannot be adjusted under an adjustment of gas 15, a differential pressure between the combustion furnace 1 and the medium container 2 is adjusted with the pressure reducing valve 20 and then it can be adjusted to a predetermined set amount.

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 boiler technology, and more particularly to a bed height control technology for the fluidized bed.

[0002]

2. Description of the Related Art In a pressurized fluidized bed boiler, 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. In the above, by supplying the fluidized medium from the above medium container into the furnace,
By changing the burial depth of the heat transfer tube in the furnace, the heat transfer area is increased or decreased to change the amount of steam generated.

Regarding such a technique, for example, Japanese Patent Laid-Open No. 1-217108 discloses the following technique. That is, in order to extract the fluidized medium from the furnace into the medium container, the lower end of the fluidized bed combustion section is opened to the bottom of the fluidized bed combustion furnace, the other end is penetrated into the combustion furnace empty tower section, and the upper part of the medium container is opened. This dust separator is provided with a suction pipe for the opened medium to connect the fluidized bed combustion furnace and the medium container, and further, the medium container has a pressure lower than that of the fluidized bed combustion furnace. Connected through. In such a technique, by adjusting and opening the valve of the conduit connecting the medium container and the external space, the pressure in the medium 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. It is extracted into the media container.

On the other hand, the technique disclosed in Japanese Patent Application Laid-Open No. 4-050443 is characterized in that the fluid medium particles are extracted and transported by a combination of a moving bed and an air flow phase. In this technique, as a means for transporting fluidized medium particles in a fluidized bed combustion furnace to a medium vessel, a moving bed downcomer pipe for medium particles is provided at the lower end of the fluidized bed combustion furnace. Further, at the lower end of the moving bed downcomer, there is an L for adjusting the particle flow rate.
A valve is installed, and further, an air flow transport pipe having an upward flow of gas for transferring the medium particles is opened and connected to the empty tower part of the medium container to move the medium particles by gravity to a moving layer of downward flow and air flow transportation. It is intended to be transferred by the gas flow phase due to gas.

[0005]

However, the above-mentioned means has a problem that it is difficult to stably control the amount of medium particles extracted from the fluidized bed combustion furnace. That is, even if the amount of aeration gas in the L valve provided in the moving bed below the fluidized bed combustion furnace is constant, the bed height of the fluidized medium in the combustion furnace is lowered by extracting the fluidized medium in the fluidized bed combustion furnace, and the L valve is The sealing performance due to the medium particles in the upper moving bed downcomer and the combustion furnace deteriorates, the amount of medium particles taken out decreases, and further, the particles flow in the moving bed downcomer, making it impossible to transfer the particles.

Further, even if the control air of the L valve is shut off when the pressure difference between the medium container and the fluidized bed furnace exceeds a certain value,
There is a problem that particles flow out from the fluidized bed furnace into the medium container, making it difficult to control the particle flow rate. This is because the combustion gas entrained in the moving bed downcomer from the fluidized bed has the same function as the control air of the L valve. Further, there is a problem that the particle temperature in the moving bed downcomer and the L valve rapidly rises, and the volume expansion of the control air supplied to the L valve makes it difficult to control the particle flow rate.

SUMMARY OF THE INVENTION The present invention solves the above problems, and a pressurized fluidized bed boiler capable of accurately adjusting the amount of particles taken out of a fluidized medium from a fluidized bed combustion furnace in accordance with the load change rate and its load control. The purpose is to provide a method.

[0008]

A first invention for solving the above-mentioned problems is a combustion furnace, a moving-bed downcomer for taking out a fluidized-bed medium together with gas from a fluidized-bed section of the combustion furnace, and the taken-out tube. A medium container for storing the fluidized bed medium, a moving bed return pipe for returning the stored fluidized bed medium to the fluidized bed portion of the combustion furnace, an L valve connected to the moving bed downcomer, and this L valve Gas amount adjusting means for adjusting the amount of aeration gas blown in and adjusting the amount of the fluidized bed medium taken out per unit time are provided, and the fluidized bed medium is provided between the combustion furnace fluidized bed section and the medium container. In a pressurized fluidized bed boiler that transfers and returns to control the bed height of the fluidized bed section and controls the load, a first differential pressure gauge for detecting a differential pressure per unit length in the moving bed downcomer. , The combustion furnace and the medium container A second differential pressure gauge for detecting a differential pressure between the two, a differential pressure adjusting means for adjusting a differential pressure between the combustion furnace and the medium container, and a detection signal by the first and second differential pressure gauges. The amount of the fluidized bed medium taken out per unit time is determined, and the differential pressure between the combustion furnace and the medium container is adjusted by the differential pressure adjusting means, or the aeration gas amount by the gas amount adjusting means. By adjusting
A pressurized fluidized bed boiler comprising: a controller for adjusting the amount of the fluidized bed medium taken out per unit time to a predetermined set amount.

Further, a combustion furnace and a moving bed downcomer for taking out a fluidized bed medium together with gas from a fluidized bed portion of the combustion furnace,
A medium container for storing the fluidized bed medium taken out, a moving bed return pipe for returning the stored fluidized bed medium to the fluidized bed portion of the combustion furnace, an L valve connected to the moving bed downcomer, and The combustion furnace fluidized bed section and the medium of a pressurized fluidized bed boiler provided with gas amount adjusting means for adjusting the amount of aeration gas blown into the L valve and adjusting the amount of the fluidized bed medium taken out per unit time. In the load control method of the pressurized fluidized bed boiler, which controls the load by controlling the bed height of the fluidized bed portion by transferring and returning the fluidized bed medium to and from the container, a unit length in the moving bed downcomer A step of detecting the differential pressure per unit, a step of detecting the differential pressure between the combustion furnace and the medium container, the unit time of the fluidized bed medium based on the detection signal by the differential pressure detection step Determine the amount taken out per By adjusting the differential pressure between the combustion furnace and the medium container and / or adjusting the aeration gas amount by the gas amount adjusting means, the amount of the fluidized bed medium taken out per unit time is adjusted to a predetermined set amount. A second aspect of the present invention is a load control method for a pressurized fluidized bed boiler, comprising:

[0010]

The flow velocity of the fluidized medium particles and gas in the moving bed downcomer is governed by the differential pressure in the moving bed downcomer and the differential pressure between the medium container and the fluidized bed furnace. Therefore, by detecting these differential pressures, the amount of the fluidized medium particles taken out per unit time in the moving bed downcomer can be known. Therefore,
By adjusting the amount of aeration gas or by adjusting the differential pressure between the combustion furnace and the medium container, the amount of the fluidized medium particles taken out per unit time can be adjusted to a predetermined set amount. For example, when the taken-out amount of the fluidized bed medium is smaller than a predetermined set amount, the differential pressure per unit length in the moving bed downcomer is also increased to reduce the differential pressure between the combustion furnace and the medium container. This can also increase the amount of the fluidized bed medium taken out.

When the amount of fluid medium particles taken out cannot be adjusted by adjusting the amount of aeration gas, the pressure can be adjusted to a predetermined amount by adjusting the differential pressure between the combustion furnace and the medium container.

[0012]

FIG. 1 is a system diagram of a pressurized fluidized bed boiler which is an embodiment of the present invention. In the pressurized fluidized bed boiler of this embodiment, a fluidized bed combustion furnace 1, a medium container 2, a cyclone 3 and the like are housed in a pressure container 4. The fluidized bed combustion furnace 1 is provided with a dispersion plate 6 for the combustion air 5 on the bottom side and is filled with a fluidized medium on the upper side. This fluid medium generates bubbles 8 by the combustion air 5 supplied through the dispersion plate 6 to form a fluidized bed 7. Coal 10 is supplied into the fluidized bed 7 by the coal feeding pipe 9 and burned. Heat transfer tubes 11 are arranged in the fluidized bed 7 to absorb combustion heat and generate steam. 13 is a combustion furnace empty tower part. It should be noted that the dispersion plate 6, the heat transfer tube 11, the coal feeding tube 9 and the like shown in FIG. 1 are merely schematic, and the same figure does not limit the scope of the present invention.

On the bottom side of the side wall of the fluidized bed combustion furnace 1, a moving bed downcomer pipe 12 is provided with an opening.
An L valve 13 is formed by extending from the bottom of the side wall of the fluidized bed combustion furnace 1 so as to be inclined with respect to the vertical direction, and further extending vertically downward. The L valve 13 has an aeration gas 15 whose flow rate is adjusted by the control valve 14.
Is supplied.

A differential pressure gauge 16 is installed in a portion of the moving bed downcomer 12 extending vertically downward, and the moving bed downcomer 1 is installed.
The differential pressure per unit length of 2 is continuously detected, and the detection signal of this differential pressure is input to the control box 17. Further, a differential pressure gauge 3 for detecting a differential pressure between the fluidized bed combustion furnace 1 and the medium container 2
0 is also provided, and this differential pressure detection signal is also sent to the control box 17
Entered in. In the control box 17, these input signals can be arithmetically processed to send operation signals to the pressure reducing valve 20 and the control valve 14 installed in the conduit 19 opened from the empty column portion 18 of the medium container 2. An airflow transport pipe 21 is connected from the L valve 13 to the empty tower portion 18 of the medium container 2,
Airflow transport gas 23 is supplied from the lower end through valve 22. The lower end of the medium container 2 is squeezed into a conical shape to form a moving bed pipe 24, and an L valve 25 is connected to the medium container 2 and is connected to the bottom of the side wall of the fluidized bed combustion furnace 1 by opening a hole. Aeration gas 27 is supplied to the L valve 25 through the valve 26. Further, a differential pressure gauge 26 is installed between the medium container 2 and the fluidized bed combustion furnace 1, and its signal is connected to the control box 17.

Pipes for transporting the medium for transferring or returning the fluidized bed medium from the fluidized bed combustion furnace 1, for example, the air flow transport pipe 21, the L valve 25 and the like, equipment and the like,
In this embodiment, they are housed in the pressure vessel 4, but they can be provided outside the pressure vessel 4.

In the pressurized fluidized bed boiler of this embodiment, for example, the pressure of the combustion furnace 1 is 10 to 20 atm, the combustion temperature is 800 to 900 ° C., and the gas velocity of the empty column portion 13 of the combustion furnace 1 is A range of 0.5 to 1.5 m / s is adopted. Limestone particles having a maximum diameter of about 3 mm are used as the fluidized medium and the in-layer desulfurizing agent.

The amount of steam generated is controlled as follows. For example, from a state in which the fluidized bed is at a height 28 where all the heat transfer tubes 4 are buried, the fluidized medium is moved to the moving bed downcomer 12,
When it is extracted and transferred to the medium container 2 through the L valve 13 and the air flow transport pipe 21, the height of the fluidized bed in the combustion furnace 1 is 28 '.
To a position where a part of the heat transfer tube group 4 is exposed from the fluidized bed 7, the heat transfer area buried in the fluidized bed 7 is reduced, and the steam generation amount can be reduced. On the contrary, from the state of the fluidized bed 28 'in the combustion furnace to the fluidized medium 29 in the medium container 2
Through the moving bed tube 24 and the L valve 25 to the fluidized bed combustion furnace 1
The heat generation amount can be increased as desired by increasing the heat transfer area by burying the heat transfer tube group 11 in the fluidized bed to a certain level.

Although the load is changed as described above, according to the pressurized fluidized bed boiler of this embodiment, the height of the fluidized bed 7 can be changed stably at a constant speed. For example, when the load is reduced, the fluidized medium is moved from the combustion furnace 1 into the moving bed downcomer 1
2, the L valve 13, and the air flow pipe 21 to pass the medium container 2
The flow rate of the fluidized medium particles is set between the combustion furnace 1 and the medium container by the differential pressure gauge 16 provided in the moving bed downcomer 12 and the signal of the differential pressure per unit length of the moving bed downcomer 12. It can be estimated by the differential pressure of the differential pressure gauge 30.

FIG. 2 shows the flow rate of fluid medium particles flowing through the L valve 13, the differential pressure per unit length of the moving bed downcomer 12, and the interphase relationship of the differential pressure between the combustion furnace 1 and the medium container 2. It is a graph figure which shows. The flow rate of the medium particles flowing through the L valve 13 changes depending on the differential pressure per unit length of the moving bed downcomer 12 and the differential pressure between the combustion furnace 1 and the medium container 2. The moving bed descending pressure has both positive and negative values, but the pressure difference between the combustion furnace 1 and the medium container 2 is always less than the internal pressure of the medium container 2.
It becomes the pressure in the combustion furnace 1. Here, the positive side of the differential pressure of the moving bed downcomer 12 indicates that the pressure is high in the lower part of the moving bed downcomer 12 and low in the upper part. On the contrary, when the differential pressure of the moving bed downcomer 12 is negative, it means that the pressure is low in the lower part of the moving bed downcomer 12 and high in the upper part. As is clear from the figure, as the differential pressure per unit length of the moving bed downcomer 12 increases or the differential pressure between the combustion furnace 1 and the medium container 2 decreases, the flow rate of the fluidized medium particles is growing. The range shown as the uncontrollable region is a range in which the flow rate of the fluidized medium particles cannot be adjusted by the flow rate of the aeration gas 15.

More specific control contents will be described with reference to FIG. FIG. 3 is a graph illustrating the operation of the pressurized fluidized bed boiler of this embodiment. Flow rate characteristics of fluid medium particles X
It is assumed that an allowable range ε centered on is a predetermined set amount of the flow amount of the fluid medium particles. For example, the medium container 2 and the combustion furnace 1
It is assumed that the pressure difference between them is set to 0 mmAq (point e) and the particle flow rate starts to decrease the bed height of the fluidized bed 7 at the point a. When the bed height in the combustion furnace 1 decreases, the sealing effect of the fluidized bed 7 disappears, and the particle flow rate decreases to the point of b. The point b is in the flow rate characteristic Y in which the flow rate of the fluidized medium particles is smaller than the flow rate characteristic X, and the particle flow rate, that is, the bed height change speed is reduced. In order to return this to the original set amount, it is necessary to bring the particle flow rate to the point of c. For that purpose, the pressure reducing valve 30 is operated, and the medium container 2
This can be achieved by lowering the pressure difference between the combustion furnace 1 and point e from point e. The predetermined set amount of the flow medium particles has a certain width ε, and the differential pressure between the medium container 2 and the combustion furnace 1 is smoothly controlled so as to be within the allowable range ε.

Next, the differential pressure per unit length in the moving bed downcomer 12 and the differential pressure between the medium container 2 and the combustion furnace 1 are shown in FIG.
Aeration gas 1 introduced into the L valve 13 shown in FIG.
The control of the bed height of the fluidized bed 7 in the case where the flow rate of the fluidized medium particles enters the uncontrollable region by 5 will be described. If the particle flow rate uncontrollable region A due to the aeration gas 15 at the point h is entered for some reason while operating at the point g, the differential pressure between the medium container 2 and the combustion furnace 1 is set to l.
Move to the point. This operation can be handled by closing the pressure reducing valve 30. As a result, the point moves to the point i of the particle flow rate characteristic, the particle flow rate becomes lower than the initial characteristic X, and the particle is out of the uncontrollable region A. In order to return this to the initial particle flow rate, the flow rate of the aeration gas 15 is increased by the control of the L valve 14 to move to the point k.

For some reason, the moving bed downcomer 12
When the differential pressure exceeds 1000 mmAq / m and enters the uncontrollable region B of the flow rate of the fluidized medium particles by the aeration gas 15, the aeration gas 15 introduced into the L valve 13 is shut off, and The control for adjusting the differential pressure between the medium container 2 and the combustion furnace 1 to the negative side may be performed.

[0023]

According to the present invention described above, the amount of particles taken out of the fluidized medium from the fluidized bed combustion furnace can be adjusted accurately in accordance with the load changing speed, and therefore NOx, CO, and It is possible to provide a pressurized fluidized bed boiler and a load control method therefor capable of stable operation without causing abnormal generation of harmful substances such as SO ₂ .

[Brief description of drawings]

FIG. 1 is a system diagram of a pressurized fluidized bed boiler which is an embodiment of the present invention.

FIG. 2 shows a flow rate of fluid medium particles flowing through an L valve, a differential pressure per unit length of a moving bed downcomer, a combustion furnace, and a medium container in a pressurized fluidized bed boiler which is an embodiment of the present invention. It is a graph figure which shows the phase relationship of the differential pressure of.

FIG. 3 is a graph showing the operation of a pressurized fluidized bed boiler which is an embodiment of the present invention.

[Explanation of symbols]

 1 fluidized bed combustion furnace 2 medium container 5, 5'bed height 7 fluidized bed section 12 moving bed downcomer 13 L valve 14 control valve 15 aeration gas 16 differential pressure gauge 17 control box 20 pressure reducing valve 25 L valve 29 fluidized bed medium 30 differential Pressure gauge

Claims (2)

[Claims] 1. A combustion furnace, a moving bed downcomer for taking out a fluidized bed medium together with gas from a fluidized bed portion of the combustion furnace, a medium container for storing the taken out fluidized bed medium, and the stored fluidized bed. A moving bed return pipe for returning the medium to the fluidized bed portion of the combustion furnace; an L valve connected to the moving bed downcomer;
Gas amount adjusting means for adjusting the amount of aeration gas blown into the L valve and adjusting the amount of the fluidized bed medium taken out per unit time are provided, and the gas is provided between the combustion furnace fluidized bed section and the medium container. In a pressurized fluidized bed boiler that transfers and returns a fluidized bed medium to control the bed height of the fluidized bed section to control the load, first detecting a differential pressure per unit length in the moving bed downcomer. Differential pressure gauge, a second differential pressure gauge for detecting a differential pressure between the combustion furnace and the medium container, and a differential pressure adjusting means for adjusting the differential pressure between the combustion furnace and the medium container, The amount of the fluidized bed medium taken out per unit time is determined based on the detection signals of the first and second differential pressure gauges, and the differential pressure between the combustion furnace and the medium container is adjusted by the differential pressure adjusting means. And / or gas amount adjusting means By adjusting the Shongasu amount,
A pressurized fluidized bed boiler, comprising: a controller for adjusting the amount of the fluidized bed medium taken out per unit time to a predetermined set amount. 2. A combustion furnace, a moving bed downcomer for taking out the fluidized bed medium together with gas from the fluidized bed portion of the combustion furnace, a medium container for storing the taken out fluidized bed medium, and the stored fluidized bed. A moving bed return pipe for returning the medium to the fluidized bed portion of the combustion furnace; an L valve connected to the moving bed downcomer;
The combustion furnace fluidized bed section and the combustion fluidized bed section of a pressurized fluidized bed boiler provided with gas amount adjusting means for adjusting the amount of aeration gas blown into the L valve and adjusting the amount of the fluidized bed medium taken out per unit time. In the load control method of the pressurized fluidized bed boiler, which controls the load by controlling the bed height of the fluidized bed portion by transferring and returning the fluidized bed medium to and from the medium container, a unit in the moving bed downcomer. A step of detecting a differential pressure per length, a step of detecting a differential pressure between the combustion furnace and the medium container, a unit of the fluidized bed medium based on a detection signal by the both differential pressure detection steps By determining the amount taken out per time, by adjusting the differential pressure between the combustion furnace and the medium container, or, or by adjusting the aeration gas amount by the gas amount adjusting means, per unit time of the fluidized bed medium take out Load control method of pressurized fluid Doso boiler which comprises a step of adjusting to a predetermined set amount.