JPH0436502A - Method of combustion for pressurized fluidized bed boiler - Google Patents

Abstract

PURPOSE:To operate a boiler always stably and under most suitable conditions by determining the quantity of discharged fluidizing medium from a fluidized bed boiler out of the system so as to keep the sum of the quantity of the medium in a storage chamber and that in the fluidized bed of the fluidized bed boiler at a constant value. CONSTITUTION:A storage chamber 8 is connected to a fluidized bed boiler 2 through a channel 26 and to a pipe 28 connected to a pressure reducing valve in its upper section and to a blowing-in pipe 30 connected to a high pressure compressor in the direction of the extension of the channel 26. The medium used in a fluidized bed 12 makes the total amount of the medium stored in the fluidized bed boiler 2 and the storage chamber 8 enough to bury the heat transfer pipe of a super-heating pipe 24. When load to a steam turbine 4 is reduced, the medium in the fluidized bed 12 is drawn into the storage chamber 8 by making its pressure negative in order to reduce the transferred heat quantity at the super-heating pipe 24, and when load increases, the medium is introduced into the boiler 2 from the storage chamber 8. And fuel which holds the temperature of the fluidized bed at 750 - 950 deg.C all the time regard less of the height of the fluidized bed is supplied into the fluidized bed, and an amount of the medium determined to keep the sum of the medium in the storage chamber and the fluid ized bed always at a constant value is discharged out of the system.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a pressurized fluidized bed boiler in which the height of the fluidized bed in the boiler can be changed, and to constantly and smoothly adjust the height of the fluidized bed. This article relates to a combustion method for a fluidized bed boiler that can be used.

[Conventional technology]

In fluidized bed boilers, sulfur contained in coal is often desulfurized using limestone or the like, and due to the nature of the desulfurization reaction, the combustion temperature of the fluidized bed has an appropriate range of 750 to 950°C. In addition, in a pressurized fluidized bed boiler, the height of the fluidized bed in the boiler is high, and the contact area between the heat transfer tubes and the fluidized bed can be changed by controlling the height of the fluidized bed. maintained.

The height of the fluidized bed in the boiler can be controlled by connecting a storage chamber that can store the fluidized bed medium to the fluidized bed boiler, allowing fluidized bed movement between the fluidized bed boiler and the storage chamber, and reducing the amount of steam generated. There are known systems that can respond to varying boiler loads. In other words, in this system, when the load decreases, the fluidized bed medium is sent to the storage chamber to lower the bed height of the fluidized bed in the fluidized bed boiler, and conversely, when the load increases, the fluidized bed medium is sent from the storage chamber to the fluidized bed boiler. and raised the layer height.

[Problem to be solved by the invention]

In a pressurized fluidized bed boiler, the fluidization velocity is selected to be relatively slow, about 1 m/see, so that the amount of fluidized medium that is thrown out from the fluidized bed is generally small. This is to prevent the height of the fluidized bed from rising as a result of the accumulation of ash, limestone, etc. in the coal in the fluidized bed as the boiler operating time passes, even if the boiler load is constant. This indicates that it is necessary to discharge the fluid medium out of the system.

In conventional fluidized bed boilers, the amount of discharge from the system was determined by the operator's judgment so that the height of the fluidized bed remained constant.

However, in a pressurized fluidized bed boiler that has a storage chamber and changes the height of the fluidized bed with the load, the following problems will occur if the boiler is operated in a manner that relies on conventional operator judgment criteria. .

In other words, when the bed height is high and the load is high, the amount of media discharged from the system is large; conversely, when the bed height is low and the load is low, the amount of media discharged from the system is small. There may be excess or deficiency in the total amount of fluid medium including the chamber.
The amount of media discharged from the system changes depending on the size of the boiler load, making the boiler operation unstable.

[Means to solve the problem]

The present invention has been made as follows to solve the above problems. In other words, the fluidized bed medium is moved between a pressurized fluidized bed boiler and a storage chamber connected to the fluidized bed boiler to change the height of the fluidized bed in the boiler according to the load, and the fluidized bed temperature changes depending on the bed height. In a pressurized fluidized bed boiler in which fuel is supplied into the fluidized bed so that the temperature is always maintained at 750 to 950°C regardless of the temperature, the sum of the media amounts of the fluidized bed in the storage chamber and the fluidized bed boiler becomes a constant value. Therefore, we decided to determine the amount of fluidized medium discharged from the fluidized bed boiler to the outside of the system.

[For production]

When the fluidized bed height rises or falls due to an increase or decrease in fuel, the sum of the media volumes in the fluidized bed in the storage room and boiler is constantly checked against the reference value and discharged outside the system based on that, so the bed height accurately corresponds to the load. In addition, it is possible to maintain a necessary and sufficient amount of fluidized bed regardless of the bed height, and it is possible to maintain a fluidized bed boiler in a state where it can cope with sudden load changes. Furthermore, since extreme fluctuations in the amount of fluidized bed medium discharged to the outside of the system do not occur, operational stability of the boiler is ensured.

〔Example〕

An embodiment of the control method according to the present invention will be described below. FIG. 1 is an example of a pressurized fluidized bed boiler. In the figure, the fluidized bed boiler 2 includes a steam turbine 4 and a condenser 6.
, a storage chamber 8, a gas turbine 10, etc., and a fluidized bed 12 is housed inside. Furthermore, the fluidized bed boiler 2 has a combustion gas discharge pipe 14 at the top and a fuel input port 1 at the side.
6. An ash discharge pipe 18 and an air introduction pipe 20 are connected to the lower part, and an air dispersion plate 22 that supports the fluidized bed 12 and a heat transfer pipe of a superheating pipe 24 buried in the fluidized bed 12 are provided inside. ing.

The superheating pipe 24 is a circulation path that connects the fluidized bed boiler 2 to the steam turbine 4 and returns via the condenser 6, and the steam turbine 4 is connected to load equipment such as a generator. The gas turbine 10 is installed in the middle of a combustion gas exhaust pipe 14 of the fluidized bed boiler 2, and like the steam turbine 14, load equipment is connected thereto.

The storage chamber 8 is formed by a peripherally insulating wall, has a capacity capable of accommodating at least the maximum reduction in the amount of medium in the fluidized bed 12 in the fluidized bed boiler 2, and is connected to the fluidized bed boiler 2 via a passage 26. , a vibrator 28 connected to a pressure reducing valve (not shown) in the upper part, and a blowing vibrator 3 connected to a high pressure compressor (not shown) in the extending direction of the passage 26.
o is connected. The medium of the fluidized bed 12 is a mixture of coal and limestone, etc., and the total amount stored in the fluidized bed boiler 2 and the storage chamber 8 is a necessary and sufficient amount to bury the heat exchanger tubes of the superheating tubes 24.

When the load on the steam turbine 4 decreases, the vibrator 28 connected to the storage chamber 8 is opened to create a negative pressure inside the storage chamber 8, and the medium of the fluidized bed 12 is introduced from the fluidized bed boiler 2. The layer height is lowered to reduce the amount of heat transferred through the superheating tubes 24. On the other hand, when the load increases, the medium of the fluidized bed 12 is introduced into the fluidized bed boiler 2 from the storage chamber 8 to raise the height of the fluidized bed.

During the above-mentioned load increases and decreases, as well as during normal operation with a constant load, the fluidized bed 12, which is about to increase due to the injection of fuel, is A determined amount of medium is discharged out of the system so that the sum of the medium amount is always constant. Specifically, detectors for detecting the bed height of the fluidized bed 12 are installed in the fluidized bed boiler 2 and the storage chamber 8, and the amount of media in the fluidized bed accommodated in each is calculated from the values of these detectors. Calculate the sum and determine the amount of emissions outside the system so that this value becomes a constant value.

Therefore, the layer height can be maintained according to the load, and
Since the total amount of the fluidized bed is kept constant, there is no problem with the movement of the fluidized bed 12 between the fluidized bed boiler 2 and the storage chamber 8, and the height of the bed can be adjusted as desired, improving the overall efficiency of the fluidized bed boiler 2. can always be maintained high.

In addition, stable operation of the boiler is ensured by preventing the occurrence of human errors, including during normal operation.

〔Effect of the invention〕

According to the control method of the present invention, a storage chamber is connected to a fluidized bed boiler, and the fluidized bed medium in the boiler is moved between the boiler and the storage chamber to change the height of the fluidized bed in accordance with the load. Regardless of the temperature, the combustion temperature in the boiler should be 750~
Fuel is supplied to maintain the temperature at 950°C, and the sum of the amount of media in the fluidized bed in the storage chamber and the amount of media in the fluidized bed in the fluidized bed boiler is made to correspond to the amount of fluidized bed in the fluidized bed boiler at the maximum load. Since the amount of medium discharged from the boiler to the outside of the system is determined, the pressurized fluidized bed boiler can always be operated in a stable and optimal state without causing human error.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a fluidized bed boiler that implements the control method according to the present invention. In the drawing 2...Fluidized bed boiler, 4...Steam turbine, 6...
・Condenser, 8...Storage room, 10...Gas turbine,
DESCRIPTION OF SYMBOLS 12... Fluidized bed, 14... Exhaust pipe, 16... Input port, 18... Discharge port, 20... Air introduction pipe, 22...
... Air distribution plate, 24 ... Heat exchanger tube, 26 ... Passage,
28...vibrator, 30...blow pipe. Figure 1

Claims (1)

[Claims] The fluidized bed medium is moved between a pressurized fluidized bed boiler and a storage chamber connected to the fluidized bed boiler to change the height of the fluidized bed in the boiler according to the load, so that the fluidized bed temperature remains constant regardless of the bed height. In a pressurized fluidized bed boiler in which fuel is supplied into the fluidized bed so that the temperature is always maintained at 750 to 950°C,
A pressurized fluidized bed boiler characterized in that the amount of fluidized medium discharged from the fluidized bed boiler to the outside of the system is determined so that the sum of the amount of media in the fluidized bed in the storage chamber and the fluidized bed boiler becomes a constant value. Combustion method.