JP2003129859A - Composite power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the output of a gas turbine generator independently of a steam turbine generator in a composite power generation system. SOLUTION: The composite power generation system is provided with: a pressurized fluidized bed boiler 5 which burns a fuel while fluidizing it using a combustion air 2 supplied from a compressor 1 as the air for fluidization and combustion, and has a steam heat transfer tube 17 and an overheating heat transfer tube 18 therein; a steam turbine generator 20 driven by the steam generated in the boiler 5; and a gas turbine generator 11 driven by a combustion gas 7 discharged from the boiler 5. In this system, there is provided a control means 28 for controlling an amount of the air for fluidization and combustion to regulate the output of the gas turbine generator 11 to a target value.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a combined power generation system including a fluidized bed combustion furnace, a steam turbine generator and a gas turbine generator.

[0002]

2. Description of the Related Art A conventional combined power generation system is installed in a fluidized bed combustion furnace for combusting air supplied from an air supply machine as fluidizing and combustion air while burning fuel while flowing the fuel. There is known a boiler including a heat transfer tube, a steam turbine generator driven by steam generated in the boiler, and a gas turbine generator driven by combustion gas discharged from a fluidized bed combustion furnace. . It is also known to use a pressurized fluidized bed combustion furnace that pressurizes the entire combustion furnace as the fluidized bed combustion furnace.

In the combined power generation system thus constructed, fuel such as pulverized coal is combusted in the fluidized bed combustion furnace, the boiler is heated by the combustion heat, and steam is generated.
The steam drives a steam turbine generator to output electric power. On the other hand, the combustion gas drives a gas turbine generator to output electric power. Usually, in the case of a boiler in which a heat transfer tube is arranged in a fluidized bed, the output of the steam turbine generator is, for example, 2.
The ratio is 8 times.

[0004]

By the way, since the temperature of the combustion gas flowing to the gas turbine generator is recovered by the boiler heat transfer tube which is not buried in the fluidized bed, the temperature of the fluidized bed is kept constant. Even if held at, it changes according to the buried area of the heat transfer tube. As a result, the gas turbine generator output also changes. For example, if the height of the fluidized bed is increased to increase the portion of the heat transfer tube buried in the fluidized bed, the temperature of the combustion gas rises and the output of the gas turbine generator increases. On the contrary, when the height of the fluidized bed is lowered, the output of the gas turbine generator becomes smaller. Generally, the fuel supply amount and the fluidized bed height are adjusted so that the output of the steam turbine generator is maintained at a constant target value. for that reason,
The area of the heat transfer tube buried in the fluidized bed increases or decreases, and the output of the gas turbine generator fluctuates. In other words, the output of the gas turbine generator is a natural result.

Further, the output of the gas turbine generator fluctuates depending on not only the combustion gas flow rate and the combustion gas temperature but also factors such as atmospheric temperature and deterioration of the compressor over time.

However, it is not desirable that the amount of power generation is unstable in the power generation system. Therefore, in the combined power generation system as described above, it is desired to adjust the output of the gas turbine generator independently of the control of the output of the steam turbine generator.

An object of the present invention is to adjust the output of a gas turbine generator in a combined power generation system independently of the steam turbine generator.

[0008]

The above object is to provide a fluidized bed combustion furnace which combusts air supplied from an air supply machine as fluidizing and combustion air while flowing fuel, and a fluidized bed combustion furnace installed in the fluidized bed combustion furnace. Fluidized bed provided with a boiler having an improved heat transfer tube, a steam turbine generator driven by steam generated in the boiler, and a gas turbine generator driven by combustion gas discharged from the fluidized bed combustion furnace. This can be solved by providing control means for controlling the fluidization and combustion air amounts in the combustion apparatus to adjust the gas turbine generator output to a target value. By doing so, the amount of the combustion gas flowing to the gas turbine can be adjusted mainly, and the output of the gas turbine generator can be stably controlled independently of the steam turbine generator.

In this case, pulverized coal can be used as the fuel of the fluidized bed combustion furnace.

Further, an oxygen concentration meter for measuring the oxygen concentration of the combustion gas of the fluidized bed combustion furnace is provided, and the control means adjusts the amount of air for fluidization and combustion to keep the measured oxygen concentration within the set range. Preferably. By doing so, the oxygen concentration in the combustion gas can be suppressed within the set range, and the combustion can be controlled by suppressing the amount of carbon monoxide generated in the combustion of the fluidized bed combustion furnace.

Here, the control means calculates a correction value of the oxygen concentration from the deviation between the output of the gas turbine generator and the target value of the output of the gas turbine generator, and corrects the set value of the oxygen concentration with the correction value. . In this way, since the set value of the oxygen concentration can be corrected and the output of the gas turbine generator can be adjusted to the target value, the output of the gas turbine generator can be stably maintained.

Further, the control means is characterized by having a limiter for suppressing the corrected set value of the oxygen concentration within the set range. As a result, the corrected oxygen concentration can be kept within the set range, and the combustion can be controlled by suppressing the amount of carbon monoxide generated in the combustion of the fluidized bed combustion furnace.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a pressurized fluidized bed boiler combined power generation system according to an embodiment of the present invention.

As shown in FIG. 1, in the pressurized fluidized bed boiler combined cycle power plant, the combustion air 2 supplied from the compressor 1 is used as fluidization and combustion air, and the combustion air 2 causes the fuel to flow. A pressurized fluidized bed boiler 5 in which a pressurized fluidized bed combustion furnace that burns while being stored in a pressure vessel 3 is provided.
An evaporation heat transfer tube 17 and a superheat transfer tube 18 are provided in the fluidized bed boiler 5. The steam turbine generator 20 is driven by the steam generated in the pressurized fluidized bed boiler 5. In addition, combustion gas 7 discharged from the pressurized fluidized bed boiler 5
The gas turbine generator 11 is driven by.
Moreover, the oxygen concentration of the combustion gas 7 is measured by the oxygen concentration meter 27,
A control device 28 for controlling the flow rate of the combustion air 2 is provided using the oxygen concentration and the output of the gas turbine generator 11 as control signals.

The operation of the embodiment thus configured will be described below. Combustion air 2 compressed by compressor 1 at startup
Is heated in a hot air stove 4 for start-up, and the temperature of the fluidized medium 6 in the pressurized fluidized bed boiler 5 is raised to a temperature at which the pulverized coal is ignited or higher, and then the pulverized coal which is the fuel is supplied to a fuel feeder (not shown) To the pressurized fluidized bed boiler 5. As a result, pulverized coal is
Is combusted as air for fluidization and combustion to form a fluidized bed to generate combustion gas 7. The combustion gas 7 passes through a flue 8 installed above the pressurized fluidized bed boiler 5 to remove dust by a dust remover 9, and then is introduced into a gas turbine 10 to rotate the gas turbine 10. The gas turbine 10 rotates the compressor 1 and drives the gas turbine generator 11 to output electric power. Combustion gas 7 that worked in the gas turbine 10
The harmful components are removed by the denitration device 12, and are introduced into the gas feed water heater 14 to exchange heat with the feed water. This allows
It becomes low-temperature exhaust gas and is emitted from the chimney 16 to the atmosphere. On the other hand, the feed water whose temperature has been raised by the gas feed water heater 14 flows through a steam feed pipe 24 to a steam heat transfer pipe 17 for steam generation installed in the pressurized fluidized bed boiler 5. The steam generated in the steam heat transfer tube 17 is separated and removed by the brackish water separator 25 from the water contained therein, and only the steam is passed through the superheat transfer tube 18 for steam heating. On the other hand, the water is circulated and supplied to the steam heat transfer tube for steam generation by the boiler circulation pump 26. The steam flowing through the superheated heat transfer tube 18 becomes high-temperature superheated steam and is introduced into the steam turbine 19 to drive the steam turbine generator 20 to generate electric power. The steam that has worked in the steam turbine 19 becomes low temperature and low pressure and is sent to the condenser 21, and the steam recovers the residual energy that it has and becomes condensed water. This condensate is supplied to the gas feed water heater 15 by the condensate pump 22, preheated by heat exchange with the combustion gas 7 from the outlet of the gas turbine 10, and gas impurities are removed by the deaerator 23 and pressurized flow. It is supplied again to the steam heat transfer tube 17 of the layer boiler 5.

On the other hand, during operation of the pressurized fluidized bed boiler combined cycle power generation system, the temperature of the fluidized medium 6 is maintained above the ignition temperature of the pulverized coal, and even if the hot-air stove 4 for starting is extinguished, As the supply amount increases, the temperature of the fluidized medium 6 (hereinafter, referred to as bed temperature) rises, and the flow rate and temperature of the combustion gas 7 emitted from the pressurized fluidized bed boiler 5 rises, so that the output of the gas turbine 10 rises. To do. At this time, since the pressurized fluidized bed boiler 5 secures a bed temperature of about 800 ° C. that can maintain stable fluidized combustion of pulverized coal, the amount of the fluidized medium 6 is small at the time of start-up and low load when the pulverized coal supply amount is small. To reduce the height of the fluidized bed and reduce the fluidized bed height
The output of the steam turbine generator is adjusted by adjusting the areas of 17 and the superheat transfer tube 18. For example, in order to increase the load of the pressurized fluidized bed boiler 5, the supply amount of pulverized coal is increased.
Since the bed temperature rises with an increase in the supply amount of the pulverized coal, supplying the fluidized medium 6 results in an increase in the areas of the steam heat transfer pipe 17 and the superheated heat transfer pipe 18 buried in the fluidized medium. The area to recover temperature is reduced. Therefore, the amount of generated steam, that is, the load on the steam turbine 19 can be increased while maintaining the bed temperature of the fluidized bed at or above a certain temperature suitable for combustion. In FIG. 1, illustration of system equipment for increasing or decreasing the amount of the fluid medium 6 is omitted.

Further, the combustion air 2 of the pressurized fluidized bed boiler 5 is
It is supplied at a certain excess rate with respect to the supply amount of pulverized coal. The excess ratio of the combustion air 2 is controlled so that the oxygen concentration of the combustion gas 7 is measured by the gas analyzer 27 installed at the outlet of the fluidized bed boiler 5 so that the oxygen concentration falls within a certain range. The combustion gas 7 passes through the steam heat transfer tube 17 and the superheat transfer heat transfer tube 18 which are not buried in the fluidized medium 6 from the layer surface of the fluidized bed, and after the dust removal device 9 removes dust from the outlet of the pressurized fluidized bed boiler 5. ,gas turbine
Vent to 10. Even if the bed temperature is almost constant, the fluid medium
Heat is exchanged by the steam heat transfer tube 17 and the superheat heat transfer tube 18 which are not buried in 6, that is, located above the layer surface of the fluidized bed,
The temperature of the combustion gas 7 will drop. As the load of the pressurized fluidized bed boiler 5 increases, the height of the fluidized bed rises and the steam heat transfer tube 17 and the superheated heat transfer tube exposed above the bed surface of the fluidized bed
When the area of 18 decreases, the flow rate and temperature of the combustion gas 7 increase and the load of the gas turbine 10 also increases.

The control means for controlling the flow rate of the combustion air 2 and adjusting the output of the gas turbine generator 11 to the target value according to the features of the present invention will now be described. The output of the gas turbine generator 11 varies depending on not only the flow rate and temperature of the combustion gas 7, but also factors such as atmospheric temperature and deterioration of the compressor 1 over time. Therefore, in the present embodiment, the gas turbine generator 11 is increased or decreased by correcting the flow rate of the combustion air 2 in accordance with the variation of the output of the gas turbine generator 11 and the deviation of the target value of the gas turbine generator 11. The output of 11 can be adjusted to the target value.

In FIG. 2, the flow rate of the combustion air 2 is increased / decreased,
1 shows an embodiment of a control device 28 that adjusts the output of the gas turbine generator 11. Basically, the flow rate of the combustion air 2 is determined by the amount of pulverized coal supplied to the pressurized fluidized bed boiler 5. The controller II calculates the required combustion air flow rate Y1 from the supply amount X of pulverized coal, controls the combustion air flow rate control valve 13 based on the calculated value, and adjusts the flow rate of the combustion air 2.

Next, the flow rate of the combustion air 2 thus adjusted can be adjusted to the target value of the fluctuating output of the gas turbine generator 11, and the oxygen concentration of the combustion gas 7 is set within the set range. The control for fine adjustment will be described.

First, as shown in FIG. 2, the deviation ΔW between the target value W0 of the output of the gas turbine generator 11 and the detected output value W of the gas turbine generator 11 is input to the controller III, and the oxygen The density correction value S2 is calculated. Calculated oxygen concentration correction value
Adjust the oxygen concentration set value SS determined in advance by S2. The adjusted oxygen concentration set value S3 is input to the limiter, and is controlled so that the oxygen concentration set value S3 falls within the set range. The oxygen concentration correction value S4 output from the limiter and the oxygen concentration S1 of the combustion gas 7 are added, and the controller I calculates the correction value Y2 of the flow rate of the combustion air 2. The correction value Y2 of the flow rate of the combustion air 2 and the flow rate Y1 of the combustion air 2 set by a function for the fuel supply amount X of pulverized coal are added, and the combustion air flow rate control valve 13 is controlled based on the value, Increase or decrease the flow rate of combustion air 2.

By properly adjusting the flow rate of the combustion air 2 as described above, not only the flow rate and the temperature of the combustion gas 7 but also the factors such as the atmospheric temperature and the aging deterioration of the compressor 1 which are artificially uncontrollable. Instead, the output of the gas turbine generator 11 can be maintained at the target value while keeping the oxygen concentration of the combustion gas 7 within the set range. That is, the gas turbine generator
The output of 11 can be adjusted independently of the steam turbine generator 20, and the power generation amount of the pressurized fluidized bed boiler combined cycle power generation system is stabilized.

For example, even when the output of the steam turbine generator 20 is constant, the output of the gas turbine generator 20 varies at night when the atmospheric temperature is low and during the day when the atmospheric temperature is high.
If the difference in atmospheric temperature between daytime and nighttime is about 10 ° C., the output of the gas turbine generator 11 fluctuates by about ± 3%. Here, the flow rate of the combustion gas 7, which corresponds to about ± 3% of the output fluctuation of the gas turbine generator 11, is 97% to 103%, which means that the oxygen concentration at the outlet of the pressurized fluidized bed boiler 5 is ± 1%. Equivalent to fluctuation. Therefore, if the set value of the oxygen concentration at the outlet of the pressurized fluidized bed boiler 5, for example 3.5%, can be adjusted within a range of ± 1%, even if the atmospheric temperature fluctuates during the day and night, the gas The flow rate of the combustion air 2 is increased or decreased according to the fluctuation of the output of the turbine generator 11, and the gas turbine generator 1
The output of 1 can be adjusted to the target value.

FIG. 3 shows the relationship between the flow rate of the combustion air 2 and the amount of fuel supplied to the pressurized fluidized bed boiler 5.
The horizontal axis is the amount of fuel supplied to the pressurized fluidized bed boiler 5,
The vertical axis represents the flow rate of the combustion air 2 flowing through the pressurized fluidized bed boiler 5. Conventionally, the fuel amount and the combustion air flow rate were supplied at a fixed ratio, but in the present embodiment, the flow rate of the combustion air 2 can be finely adjusted by providing an operation width that can be corrected to a fixed ratio. . By providing the operation width in this way, the gas turbine generator output 11 can be adjusted independently of the steam turbine generator 20 while adjusting the oxygen concentration of the combustion gas 7 to fall within a certain range.

Although the present invention has been described based on the embodiment of FIG. 1, the configuration of the combined power generation system according to the present invention is not limited to this. For example, in the embodiment shown in FIG. 1, the combined power generation system including the pressurized fluidized bed boiler 5 has been described, but the present invention is not limited to this, and can be applied to a fluidized bed boiler that is not pressurized. .

Although pulverized coal is used as the fuel in the present embodiment, the present invention is not limited to this. In short, any fuel can be used as long as it can burn while forming a fluidized bed.

Further, in the embodiment of FIG. 1, the gas turbine 10 is of the single-shaft type that drives the compressor 1 at the same time, but the present invention is not limited to this, and the compressor is driven by another drive machine, for example. You may do it.

As described above, according to the embodiment of the present invention, the output of the gas turbine generator 11 can be adjusted independently of the output of the steam turbine generator 20, as compared with the conventional technique. Therefore, the output of the gas turbine generator 11 can be stably maintained, and the combined power generation system can be stably operated.

[0029]

As described above, according to the present invention, the output of the gas turbine generator in the combined power generation system can be adjusted independently of the steam turbine generator.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment in which the present invention is applied to a pressurized fluidized bed boiler combined power generation system.

FIG. 2 is a diagram showing details of a control device used in an embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the amount of fuel supplied to the pressurized fluidized bed boiler and the flow rate of combustion air in the present embodiment.

[Explanation of symbols] 1 compressor 2 Combustion air 5 Pressurized fluidized bed boiler 6 Fluid medium 7 Combustion gas 11 gas turbine generator 13 Combustion air flow control valve 17 Evaporative heat transfer tube 18 Overheated heat transfer tube 20 steam turbine generator 27 Oxygen meter 28 Control device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02P 9/04 H02P 9/04 PF term (reference) 3G071 AB01 BA04 FA01 HA02 JA03 3G081 BA02 BA11 BB00 BC05 DA22 5H590 AA08 AA21 CA01 CA08 CA29 CC01 EA14 EB14 FA01 GA06 HA06

Claims (4)

[Claims] 1. A fluidized bed combustion furnace for combusting air supplied from an air supply machine as fluidizing and combustion air while flowing fuel, and a boiler having a heat transfer tube installed in the fluidized bed combustion furnace. A fluidized bed combustion apparatus comprising a steam turbine generator driven by steam generated in the boiler and a gas turbine generator driven by combustion gas discharged from the fluidized bed combustion furnace, A combined power generation system comprising a control means for controlling the amount of combustion air to adjust the output of the gas turbine generator to a target value. 2. An oxygen concentration meter for measuring the oxygen concentration in the combustion gas of the fluidized bed combustion furnace is provided, and the control means controls the fluidization and combustion air amounts so as to keep the oxygen concentration within a set range. The combined power generation system according to claim 1, wherein the combined power generation system is adjusted. 3. The control means calculates a correction value of the oxygen concentration from a deviation between the target values of the gas turbine generator output and the gas turbine generator output, and corrects the set value of the oxygen concentration with the correction value. The combined power generation system according to claim 2, wherein 4. The control device according to claim 3, wherein the control unit has a limiter for suppressing the corrected set value of the oxygen concentration within a set range.