JP2000257809A - Pressurized fluidized bed boiler and starting method of same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a quick response of main steam temperature control when the main stream temperature is controlled by regulating the balance of a rate of water to fuel only through the regulation of flow rate of fuel by a method wherein the combustion air flow rate controllability of respective furnaces, divided into a plurality of sets, and the combustion characteristics as well as the atmospheric characteristic of a boiler furnace are improved while the starting method of the furnaces is provided. SOLUTION: In a pressurized fluidized bed boiler, in which an evaporator 23 is arranged in a furnace 1a, a super-heater 24 and a re-heater 25 are arranged in another furnace 1b, respective furnaces 1a, 1b are received into pressure vessels 27a, 27b receiving respective furnaces 1a, 1b individually, while means 3a, 3b for regulating combustion air sent into respective furnaces 1a, 1b, and a regulating means for the rate of supplying fuel are provided, the flow rate of combustion air is regulated by introducing a control signal, for operating the combustion air flow rate regulating devices 3a, 3b in accordance with the superficial velocity detecting values of superficial velocity measuring instrument 5a, 5b in respective furnaces 1a, 1b, as the correcting factor for the regulation.

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 and a method of operating the same, and more particularly, to a method of starting the same and a method of controlling the steam temperature of a pressurized-type fluidized-bed boiler in which a steam system has the form of a once-through boiler. .

[0002]

2. Description of the Related Art In a fluidized bed boiler having an evaporator, a superheater and a reheater in a fluidized bed, a fluidized bed having an evaporator and a fluidized bed having a superheater and a reheater are divided into two parts. It is known from Japanese Utility Model Publication No. 3-11521 or the like to start up a fluidized bed having the cooling steam of the superheater and the reheater first, and then start the fluidized bed of the superheater and the reheater.

On the other hand, in a pressurized fluidized-bed boiler, a furnace having an evaporator and a furnace having a reheater among evaporators, superheaters and reheaters are individually housed in at least two pressure vessels. For example, Japanese Patent Application Laid-Open No. 5-248601
It is known as described in Japanese Patent Publication No.

In the pressurized fluidized-bed boiler of the prior art, as shown in FIG. 8, a program control for supplying a required amount of air corresponding to a fuel supply amount from the compressor 2 to the boiler is performed as shown in FIG. The air flow control device 22 of the compressor 2 controls the flow rate so that the boiler outlet oxygen concentration becomes constant with respect to the influence of the combustion state fluctuation.

In this case, when the pressurized fluidized-bed boiler is started, the fuel supply start timing and the fuel supply amount to the two furnaces 1a and 1b disposed between the pressure vessels 27a and 27b are different from each other. The oxygen concentration at the furnace outlet is detected so that the air supplied to the furnace can be supplied at a constant ratio to the fuel input amount, and the air distribution to each furnace is controlled so as to reach the set target concentration value.

For example, the combustion air supplied from the compressor 2 is supplied to an air flow controller 22 of the compressor 2.
Is controlled to an appropriate value such that the boiler outlet oxygen concentration becomes a predetermined value, and is further distributed to the furnaces 1a and 1b filled with the fluidized beds 8a and 8b through the boiler air flow controllers 3a and 3b, respectively. Since the air amount is supplied at a constant ratio to the fuel flow rate supplied to each of the furnaces 1a and 1b, the exhaust gas oximeter 4 is provided at the furnace outlet gas pipes 9a and 9b.
a, 4b are installed, the oxygen concentration here is measured, and the air flow rate adjusting devices 3a, 3b are set so as to have predetermined values.
Distributed in.

[0007] The air flow rate adjusting device 22 has a signal from the air flow rate converter 20 based on a signal from the adder 11 via the fuel flow meters 6a and 6b and an oxygen based on a signal from the boiler outlet oxygen concentration meter 18. A value obtained by adding the signal of the airflow converter 19 of the density deviation and the signal of the airflow converter 19 by the adder 21 is input.

For this reason, in the prior art, when the measured values of the oxygen concentration meters 4a and 4b of the furnace outlet gas become different from the set values, the deviation is calculated by the furnace outlet oxygen concentration deviation subtractor 16 and obtained. The oxygen concentration deviation and the damper opening are converted by the converter 17 and further converted by the converter 17 into an air flow rate adjustment signal.

On the other hand, the air flow rate of each furnace 1a, 1b is determined by the ratio of the fuel amount obtained by the adder 11 to which the signals measured by the fuel flow meters 6a, 6b are added and the furnace fuel ratio calculation divider 12 by the damper opening degree. A command signal of the air flow controller is generated by a damper opening degree converter 13 which converts the signal into a signal, and the signal from the converter 17 is added to the signal by an adder 14.
a and 1b are sent as signals to the air flow controllers 3a and 3b. Normally, the air flow controllers 3a and 3b are valves or dampers for changing the air flow resistance. At this time, the air flow controllers 3a and 3b operate in reverse via the damper reverse operation signal function unit 15, respectively. At the initial stage of boiler startup and before venting of the steam turbine, combustion is first introduced into the furnace 1a having the evaporator 23, and the steam necessary for cooling the superheater 24 and the reheater 25 in the evaporator 23 of the furnace 1a. , Fuel is supplied to the furnace 1b having the reheater 25 to start the furnace. The time difference between the start of the furnace 1a and the start of the furnace 1b is approximately 1 to 5 hours.

[0010] The flow rate of combustion air supplied to the boiler and each furnace 1
The air amount distribution to the furnaces 1a and 1b is controlled such that the outlet oxygen concentration of each of the furnaces 1a and 1b is about 3 to 5 in accordance with the above-described control according to the fuel input amount.
It is adjusted to be%.

FIG. 9 shows a system diagram of main steam temperature control during a once-through operation of a conventional once-through boiler, and FIG. 10 shows a system diagram of a variable-pressure once-through boiler. In FIG. 10, the boiler furnace wall 74 is shown.
Consists of a membrane wall with water pipes continuously welded in a plate shape,
It constitutes a heat transfer surface. The water supply to the boiler furnace wall 74 is
First, the water is sent from the feed water pump 71 to the feed water heater 72 and heated, and then sent to the boiler furnace wall 74 and the evaporator 75 via the economizer 73. The feedwater rises while being heated by the boiler furnace wall 74 and the evaporator 75, and finally generates steam.

The generated steam is sent to a high-pressure turbine 82 through a steam separator 76, a primary superheater 77, a superheater superheat reducer 78 and a secondary superheater 80. The steam that has worked in the high-pressure turbine 82 is sent to the medium-pressure turbine 87 via the reheater overheat reducer 83 and the reheater 85.

The superheater superheat reducer 78 and the reheater superheat reducer 83 have a superheater spray flow rate control valve 79, respectively.
The temperature is adjusted by the spray water whose supply amount has been adjusted by 84. The steam discharged from the intermediate pressure turbine 87 is recovered by a condenser (not shown), and is recycled to the water supply system. The temperature of each steam supplied to the high-pressure turbine 82 and the intermediate-pressure turbine 87 is measured by thermometers 81 and 86.

As shown in the system diagram of the main steam temperature control during the once-through operation of the once-through boiler in FIG. 9, the transient main steam temperature control is performed by superheater spray injection, but the permanent main steam temperature control is performed by the water-fuel ratio. Control (controls the ratio of boiler feed water amount to fuel amount). At this time, in the conventional boiler, the water-fuel ratio is adjusted by adjusting the fuel amount so that the ratio (water-fuel ratio) between the boiler water supply amount and the fuel amount becomes a desired value.

The fuel flow command 101 is a boiler input command 9
1 is input to a function generator 95 having a boiler input command-fuel flow rate set value characteristic determined by the boiler static characteristics, and the output of the base fuel flow rate signal 103 is corrected by a spray amount in an adder 96. It is produced by adding a correction by the main steam temperature deviation 94 in the adder 97.

The correction added to the base fuel flow signal 103, which is the output of the function generator 95, in the adder 96 is as follows:
This is a correction circuit for adjusting the fuel flow rate and returning to the original spray ratio when the spray flow rate changes due to a transient change and the spray ratio is deviated from the planned value and balance is achieved.

The correction signal is a function generator 9 having a load command-spray flow rate set value characteristic determined by the boiler static characteristic.
In step 8, a spray flow rate set value 104 corresponding to the load command 92 is created, and the spray flow rate set value 1 which is the output of the function generator 98.
A function generator 102 converts a spray flow rate deviation signal, which is an output signal of a subtractor 99, from a spray flow rate measured value 93 to a base fuel flow rate signal 103 output from a function generator 95. It is added by the adder 96.

The correction added to the output signal of the adder 96 in the adder 97 is a correction circuit for adjusting the fuel flow rate for controlling the main steam temperature. This correction circuit uses an output signal obtained by calculating a main steam temperature deviation 94, which is a deviation between the main steam temperature set value and the actually measured value, by the proportional integrator 100 as a fuel flow rate correction signal and an adder 97 to the adder 9
6 is added to the output signal.

The fuel flow rate command signal 101 corrected by the above-mentioned spray flow rate deviation and main steam temperature deviation,
The fuel flow rate is adjusted so that the boiler feedwater flow rate according to the load at that time and the appropriate water-fuel ratio for the main steam temperature,
The main steam temperature is controlled to a desired value.

[0020]

The concept of the air flow control of the prior art shown in FIG. 8 is to control the optimum fuel / air ratio for combustion. The amount is not merely the amount of air required for combustion, but also has the purpose of supplying the fluidized air necessary to maintain stable fluidized bed combustion. The stable flow is generally related to the superficial velocity of the fluidized bed, and in the pressurized fluidized-bed boiler, the superficial velocity of 0.
It is necessary to maintain about 9 to 1.0 m / s.

In the design of a pressurized fluidized-bed boiler, if the amount of combustion air is increased with an increase in the amount of fuel (load), the amount of combustion gas increases and the gas pressure in the boiler furnace (fluidized bed) increases. If an appropriate flow area (furnace cross-sectional area) is selected, the superficial velocity should be almost constant (about 0.9 to 1.0 m / s) even when the supply air volume is increased or decreased from high load to low load. become.

However, as described above, the furnace 1 in which the evaporator 23 is disposed in the conventional pressurized fluidized-bed boiler is used.
a, from the furnace 1b in which the superheater 24 and the reheater 25 are arranged, from the furnace 1a in which the evaporator 23 is arranged, and if the cooling steam of the superheater 24 and the reheater 25 is to be secured, The gas pressure of the furnace 1a after the
The pressure is gradually increased from a to about 1 MPa.

Accordingly, the furnace 1a in which the evaporator 23 is disposed
Since the gas pressure of the furnace 1a rises before the furnace 1b in which the superheater 24 and the reheater 25 are arranged after starting the furnace 1b, the furnace 1b in which the superheater 24 and the reheater 25 are arranged Is started, the air flow rate in the compressor 2 is adjusted so that the outlet oxygen concentration of the furnace 1b becomes the same value as that of the furnace 1a in which the evaporator 24 is arranged. Since the superficial velocity is low, the superficial velocity of the furnace 1b in which the superheater 24 and the reheater 25 started later are arranged is lower than the superficial velocity of the furnace 1a in which the evaporator 23 started earlier is arranged. However, stable fluid combustion may not be maintained.

Here, the oxygen concentration at the outlet of the furnace 1b is
The reason for making the same value as the outlet oxygen concentration of a is as follows.
It is as follows. That is, when the furnace outlet oxygen concentration increases, the NOx also increases. Even if the outlet oxygen concentration of one furnace is low and the outlet oxygen concentration of the other furnace is high, the NOx concentration in the combined exhaust gas is not averaged, and the exhaust gas having a high NOx concentration is discharged. . Therefore, it is necessary to make the outlet oxygen concentration of each furnace the same as much as possible.

As described above, in the prior art combustion air flow control method, each furnace 1a, 1
Although the outlet oxygen concentration of b is used for the air control signal,
In a pressurized fluidized-bed boiler having a plurality of furnaces, the start timing of each furnace requires a deviation, so that there is a possibility that the superficial velocity of the furnace started later cannot be maintained within a certain range. Further, in order to reduce the deviation as much as possible, it is necessary to execute the start timing of the furnace 1b in which the superheater 24 and the reheater 25 are arranged in the shortest necessary time.

A first object of the present invention is to solve the above-mentioned problems of the prior art and to improve the controllability of the combustion air flow rate of each of the plurality of furnaces, the combustion characteristics of the boiler furnace, and the environmental characteristics. It is an object of the present invention to provide a pressurized fluidized bed boiler and a method for starting the same. Further, in the conventional method of controlling the once-through boiler shown in FIG. 9, the response from the change of the fuel flow rate to the change of the main steam temperature is faster than that of the pressurized fluidized-bed boiler. Although the temperature is controlled, when this conventional boiler technology is applied to a pressurized fluidized bed boiler, there are problems specific to the pressurized fluidized bed boiler as described below.

That is, in the pressurized fluidized bed boiler, the main steam temperature control is basically performed by changing the fuel flow rate. In the case of the pressurized fluidized bed boiler, coarse coal, pulverized coal, coal stone and water are mixed. Into paste (hereinafter CWP)
) As fuel, and the fuel contains a large amount of water (about 2
(5 to 30 wt%), and because of the presence of coal having a large particle size, the combustion delay is larger than that of a conventional boiler using pulverized coal, oil, gas or the like as a fuel (90 to 12 wt%).
0 seconds), the fuel flow rate changes, the heat input to the fluidized bed changes, and as a result, the fluidized bed temperature changes, then the heat transfer tube temperature changes, and the steam temperature changes. It takes a long time to change the steam temperature. Therefore, if the main steam temperature is controlled only by adjusting the fuel flow rate, a large response delay occurs in the main steam temperature, and it is difficult to obtain a quick main steam temperature control response.

In particular, when the balance of the water-fuel ratio is lost and the main steam temperature starts to rise, the fluidized bed temperature does not immediately decrease even if the fuel flow rate is reduced. Therefore, the main steam temperature tends to overshoot, and in some cases, the main steam temperature becomes abnormally high, which may lead to an emergency stop of the boiler.

As a method of controlling the main steam temperature, there is a method of injecting a superheater spray. However, if the injection amount of the superheater spray is increased, the amount of water supplied through the water wall and the evaporator is reduced. Since the temperature rises, it is only transiently effective, and if the temperature of the evaporator rises too much, it may lead to heat transfer tube damage.

The pressurized fluidized-bed boiler is operated with the fluidized-bed temperature controlled so as to always fall within a specified temperature range for reasons such as maintaining desulfurization performance in the furnace and suppressing the amount of exhaust gas NOx generated. There must be. For this reason, the temperature range in which the fluidized bed temperature can be varied is narrow, and the range of change in the fuel flow rate is also limited.Therefore, quick main steam only by adjusting the fuel flow rate in a state in which the range of the fluidized bed temperature variation is limited. It is difficult to obtain a temperature control response.

Accordingly, a second object of the present invention is to obtain a quick main steam temperature control response when the main steam temperature control is performed by adjusting the balance of the water-fuel ratio only by adjusting the fuel flow rate. An object of the present invention is to solve the problems of a pressurized fluidized-bed boiler.

[0032]

The first object of the present invention is attained by incorporating a measurement signal of the superficial velocity of each furnace as a correction factor of a control signal for operating a combustion air flow control device. That is, the present invention arranges an evaporator, a superheater and a reheater in a furnace, and among the evaporator, the superheater and the reheater, a furnace in which at least an evaporator is arranged and a furnace in which at least a reheater is arranged. Furnace divided into at least two separate furnaces, at least two pressure vessels for individually storing each divided furnace, and means for adjusting the combustion air and fuel supply ratio sent to each furnace A pressurized fluidized-bed boiler, comprising: means for detecting the superficial velocity of each furnace, wherein the air for adjusting the flow rate of combustion air supplied to the pressurized fluidized-bed boiler according to at least the detection value of the superficial velocity detection means It is a pressurized fluidized bed boiler having a flow rate adjusting means.

At the time of starting the boiler, the combustion air flow rate can be adjusted not only when the combustion air flow rate is adjusted only by the superficial velocity in the furnace but also in consideration of the value of the gas oxygen concentration at the furnace outlet.

Further, the present invention provides an evaporator, a superheater and a reheater in a furnace, and comprises, among the evaporator, the superheater and the reheater, at least a furnace in which the evaporator is arranged and at least a reheater. Furnace divided into at least two separate furnaces respectively arranged, at least two pressure vessels individually housed each divided furnace, the combustion air and fuel supply ratio to be sent to each furnace In a pressurized fluidized-bed boiler having a means for adjusting, when starting the boiler, the flow rate of combustion air supplied to the pressurized fluidized-bed boiler is adjusted according to the superficial velocity of each furnace, and the fuel and air supply amounts of each furnace are adjusted. After the pressure becomes approximately the same, this is a method for starting a pressurized fluidized bed boiler in which the combustion air flow rate is adjusted according to the oxygen concentration at the boiler outlet.

The present invention also includes the following invention.
That is, an evaporator, a superheater and a reheater are arranged in a furnace, and among the evaporator, the superheater and the reheater, a furnace in which at least an evaporator is arranged and a furnace in which at least a reheater is arranged. Furnace divided into at least two separate furnaces, at least two pressure vessels for individually storing each divided furnace, and means for adjusting the combustion air and fuel supply ratio sent to each furnace In a pressurized fluidized-bed boiler having a furnace, after starting a furnace having an evaporator, steam generated by the evaporator is introduced into a superheater and a reheater arranged in a furnace other than the furnace having an evaporator, and After detecting that the amount of introduced steam has reached a predetermined value or more, in the starting process of starting a furnace equipped with a superheater and a reheater, the superficial velocity of each furnace and the furnace To the boiler so that the outlet oxygen concentration becomes the specified value A pressurized flow boiler starting method of controlling the air flow rate to be fed.

In the present invention, the distribution of the combustion air flow to the plurality of furnaces is adjusted by the combustion air adjusting device at the furnace inlet. By taking the superficial velocity as a correction factor, the start timing of each furnace is adjusted. However, since the combustion air flow rate is controlled so that it stays within a certain superficial velocity even if there is a deviation in the bed temperature or bed height, it is necessary to ensure stable combustion during the startup process of multiple furnaces with different startup timings. Can be.

The second object of the present invention is achieved by the following method. In the main steam temperature control performed by adjusting the balance of the water-fuel ratio during the once-through operation, the main steam temperature is basically controlled by adjusting the fuel flow rate. As a backup in an emergency where the main steam temperature could not be controlled due to a delay in the response to the steam temperature, the response to the main steam temperature was fast, and the desulfurization performance in the furnace peculiar to pressurized fluidized-bed boilers was maintained and the amount of NOx generated in the exhaust gas was reduced. The boiler feedwater flow rate, which is not affected by the limitation of the bed temperature change width due to suppression or the like, is adjusted and suppressed.

The pressurized fluidized-bed boiler must be controlled and operated so that the fluidized-bed temperature always falls within a specified temperature range for reasons such as maintaining desulfurization performance in the furnace and suppressing generation of NOx in exhaust gas.

Since the main steam temperature is determined by the balance between the fuel flow rate, the fluidized bed height, and the boiler feedwater flow rate, the main steam temperature and the fluidized bed height are controlled when the fuel flow rate, the fluidized bed height, and the boiler feedwater flow rate are controlled to be constant. The temperature will be constant. When the fuel flow rate or the boiler feed water flow rate is changed, the ratio of the boiler feed water flow rate to the amount of heat applied to the boiler feed water, that is, the water-fuel ratio changes, and the main steam temperature also changes according to the change in the water-fuel ratio.

When the water-fuel ratio is changed by the fuel flow rate, the combustion delay of the fuel is large, and the fuel flow rate changes to change the amount of heat input to the fluidized bed. As a result, the fluidized bed temperature changes, Since the heat pipe temperature changes and the steam temperature changes, the time constant is large and it takes time to change the steam temperature, resulting in a large response delay in the main steam temperature. On the other hand, when the water-fuel ratio is changed with the boiler feedwater flow rate,
Since the water-fuel ratio is changed by directly changing the boiler feedwater flow that flows out as main steam after being input to the boiler, the water-fuel ratio is changed as compared to the case where the fuel flow is changed with a large fuel flow delay in response to the main steam temperature. Quick response to main steam temperature change.

Therefore, the main steam temperature control can be performed with a quick response by adjusting the boiler feedwater flow rate and changing the water-fuel ratio. Further, the main steam temperature change due to the combustion delay peculiar to the pressurized fluidized bed boiler can be achieved. The main steam temperature can be controlled without being affected by the delay in the response of the fluidized bed, the restriction of the fluidized bed temperature change width due to the maintenance of the in-furnace desulfurization performance, the suppression of the exhaust gas NOx generation, and the like.

However, the main steam temperature can be quickly controlled by changing the flow rate of the boiler feedwater, but if the flow rate of the boiler feedwater is changed, the flow rate of the main steam also changes and the output of the steam turbine is affected. The steam temperature is basically controlled by adjusting the fuel flow rate, and the boiler feedwater flow rate is adjusted as a backup in an emergency in which the response to the main steam temperature is slow only by adjusting the fuel flow rate and the main steam temperature cannot be controlled. Control.

That is, the present invention provides a pressurized fluidized-bed boiler in which a heat transfer tube group in which a steam system has the form of a once-through boiler is arranged in a fluidized bed. In the method of controlling a pressurized fluidized-bed boiler that controls the main steam temperature determined by the water-fuel ratio by controlling the main steam temperature by adjusting the fuel flow rate, the response to the main steam temperature is controlled by adjusting the fuel flow rate. A method for controlling a pressurized fluidized-bed boiler, comprising controlling a main steam temperature by adjusting a boiler feedwater flow rate which responds quickly to a main steam temperature as a backup in an emergency when the main steam temperature cannot be controlled late. It is.

Further, according to the present invention, a boiler fuel flow rate is determined based on a deviation between a fuel flow rate set value determined by a boiler input command signal and a fuel flow rate measured value, and the main steam temperature is set with respect to the boiler fuel flow rate. The fuel flow rate is controlled by adding a correction based on the deviation between the measured value and the measured value, and the base water flow rate is determined based on the deviation between the set value of the boiler water flow rate and the measured value of the water flow rate, which is determined by the boiler input command signal. The main steam temperature is corrected according to the deviation between the set value and the measured value, and the fuel supply amount determined by the boiler input command signal is further corrected by the deviation between the main steam temperature set value and the measured value. A method for controlling a pressurized fluidized-bed boiler, wherein the correction is performed to adjust the boiler feedwater flow rate.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a specific example of a combustion air flow control method for a pressurized fluidized bed boiler according to the present invention. 1 having the same function as the device shown in FIG. 4 among the devices having the configuration shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. The pressurized fluidized bed boiler shown in FIG. 1 operates as follows.

After starting the furnace 1a having the evaporator 23, the steam generated in the evaporator 23 is introduced into the superheater 24 and the reheater 25 arranged in the furnace 1b, and the amount of introduced steam is detected. After detecting that the amount of introduced steam has reached a predetermined value or more, the furnace 1b including the superheater 24 and the reheater 25 is started, and in the starting process, the superficial velocity of each of the furnaces 1a and 1b is increased. And a method for starting the boiler for controlling the flow rate of combustion air supplied to the boiler so that the oxygen concentration at the furnace outlet becomes a predetermined value.

A furnace 1a having an evaporator 23 and a superheater 24
In the pressurized fluidized-bed boiler having the furnace 1b provided with the reheater 25, the amount of combustion air supplied to each furnace 1a, 1b is adjusted by adjusting the air supplied from the compressor 2 by the adjusting devices 3a, 3b. And the respective furnaces 1a, 1
b.

In the example shown in FIG. 1, the distribution of the combustion air flow rate of each of the furnaces 1a and 1b is changed depending on the ratio of the supplied combustion, and the measured values of the exhaust gas oximeters 4a and 4b of each of the furnaces 1a and 1b are measured. This is a control method for correcting the distribution of the combustion air flow rate based on the deviation and the deviation between the measured values of the superficial velocity measuring devices 5a and 5b.

By doing so, each furnace 1
A control device 3 for controlling the combustion air flow rate by controlling the deviation of the superficial tower speeds 5a and 5b due to the bed temperature and the fluidized bed height difference at the time of start-up of a and 1b
The effects of a and 3b make it possible to secure a certain range.

For example, when the furnace 1b is started, the superficial velocity 5b
Is less than the required value, the amount of air supplied from the compressor 2 is increased by the air volume converter 19 for the oxygen concentration deviation at the superficial velocity 5b, but the amount of air supplied to the furnace 1a is constant at the outlet oxygen concentration of the furnace 1a. The flow rate of air supplied to the furnace 1b is adjusted by the boiler outlet oximeter 18 so that the furnace 1b does not fall below the superficial velocity 5b required for stable flow. Is controlled.

In the configuration shown in FIG. 1, the control of the air flow rate adjusting device 22 of the compressor 2 is corrected by the signal of the air flow rate converter 19 of the oxygen concentration deviation of the superficial velocity, but the output oxygen of the boiler furnaces 1a and 1b is corrected. Since the concentration detection means 4a and 4b are provided together, the deviation of the measured values of the exhaust gas oximeters 4a and 4b and the superficial velocity meter 5 when the boiler is started up
A control method for correcting the distribution of the combustion air flow rate based on the deviations of the measured values a and 5b is performed. After the combustion / air supply amounts of the plurality of furnaces 1a and 1b become substantially the same, the boiler outlet oxygen concentration meter 4a It is also possible to switch the control method so that the control correction of the air flow control device 22 of the compressor 2 can be performed with each of the measured values 4b and 4b.

In the pressurized fluidized-bed boiler shown in FIG. 1, only the evaporator 23 is arranged in the furnace 1a, but a part of the superheater 24 is arranged in the furnace 1a in addition to the evaporator 23, and May be arranged in the furnace 1b, and at the same time, a reheater is also arranged in the furnace 1b.

FIGS. 2 to 7 show a control system diagram and a control characteristic diagram of a main steam temperature control system of the pressurized fluidized-bed boiler according to the embodiment of the present invention.

In the control system diagram of the main steam temperature control system shown in FIG. 2, a boiler input command signal 32 is a function generator having a boiler input command-feed water flow rate set value characteristic as shown in FIG. The difference signal between the feed water flow rate set value 44 and the measured feed water flow value 31 that is input to the feed water flow rate 38 is generated by the subtractor 34, and the feed water flow deviation signal output from the subtracter 34 is input to the proportional integrator 35. And calculate
The output is the base feed pump output command 45. The base feed water pump output command 45 is corrected by the main steam temperature deviation in the adder 42, and an output is obtained in the adder 42. The output, the feed water pump output command 46, passes through the automatic / manual switch 43. Is output to the feedwater pump.

The correction added by the adder 42 to the base feed water pump output command 45, which is the output of the proportional integrator 35, is to adjust the feed water pump output when a deviation occurs between the set value of the main steam temperature and the measured value. It is a correction circuit for controlling the main steam temperature by changing the boiler feedwater flow rate.

The correction circuit includes a main steam temperature set value 47, which is an output signal of a function generator 36 having a boiler input command-main steam temperature set value characteristic as shown in FIG. The difference signal of the value 33 is subtracted by a subtractor 39.
The main steam temperature deviation signal output from the subtractor 39 is input to the function generator 49. The function generator 49 is a function for setting a dead zone in the main steam temperature deviation as shown in FIG. 7, and is for the purpose of using the main steam temperature control by adjusting the flow rate of the boiler feed water as a backup of the main steam temperature control by adjusting the fuel flow rate. If the main steam temperature deviation does not exceed a specified value, the main steam temperature based on the boiler feed water flow rate is not operated.

The output of the function generator 49 is
Is multiplied by the multiplier 40 with the gain correction signal 48 which is the output of. The reason why the multiplier 40 multiplies the main steam temperature deviation by the gain correction signal 48 output from the function generator 37 having the boiler input command-main steam temperature deviation gain correction signal characteristic as shown in FIG. This is because the amount of change in the main steam temperature with respect to the amount of correction of the boiler feedwater flow changes depending on the load unless the amount of correction to the boiler feedwater flow for the main steam temperature deviation is changed according to the boiler feedwater flow rate.

The output of the multiplier 40 is input to a proportional unit 41 for calculation, and the output is added to a proportional integrator 35 by an adder 42.
The output of the adder 42 is added to the base feed water pump output command 45 which is the output of the boiler feed water pump output command 46.
And is output to the boiler feed pump through the automatic / manual switch 43. As the proportional coefficient of the proportional unit 41, a coefficient obtained from the characteristic of the main steam temperature change width with respect to the boiler feedwater flow rate change amount is used.

Also, because of the main steam temperature due to the adjustment of the fuel flow rate, the main steamer output signal of the function generator 36 having a boiler input command-main steam temperature set value characteristic as shown in FIG. A deviation signal between the steam temperature set value 47 and the measured main steam temperature value 33 is calculated by the proportional integrator 50, and the output thereof is determined by the boiler static characteristic in the adder 51. As shown in FIG. The base fuel supply pump output command, which is the output of the function generator 52 having the pump output command characteristic, is corrected by the main steam temperature deviation. The fuel supply pump output command corrected by the adder 51 is output to the fuel supply pump through the automatic / manual switch 54.

In the above control example, in the main steam temperature control of the pressurized fluidized-bed boiler, response delay of steam temperature change due to fuel combustion delay peculiar to the pressurized-type fluidized-bed boiler, maintenance of in-furnace desulfurization performance and suppression of exhaust gas NOx generation are described. The response to the main steam temperature is slow only by adjusting the fuel flow rate due to the limitation of the fluctuation range of the fluidized bed temperature due to the boiler temperature, etc., and the boiler feed water flow rate is adjusted as a backup only in an emergency when the main steam temperature cannot be controlled. Controls the temperature, and adjusts the boiler feedwater flow rate to delay the response of steam temperature changes due to fuel combustion delay peculiar to pressurized fluidized-bed boilers, and to maintain the in-furnace desulfurization performance and suppress the generation of exhaust gas NOx in the fluidized bed. The main steam temperature can be quickly controlled without being affected by the limitation of the temperature range in which the temperature can be varied.

[0061]

According to the present invention, when starting a pressurized fluidized bed boiler having a furnace divided into two or more, it is possible to secure the superficial tower speeds of two or more furnaces having different starting timings within a certain range. Thus, stable combustion is achieved during the start-up process of each furnace.

In the main steam temperature control, when the balance of the water-fuel ratio is changed only by adjusting the fuel flow rate, the response to the main steam temperature is slow, and the main steam temperature cannot be controlled only by adjusting the fuel flow rate. As a backup, the boiler feedwater flow rate is not affected by the rapid response to the main steam temperature and is not affected by the limitation of the range of fluidized bed temperature change due to the maintenance of in-furnace desulfurization performance unique to pressurized fluidized bed boilers and the suppression of exhaust gas NOx generation. By controlling the main steam temperature quickly by adjusting, the controllability of the main steam temperature is also improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of combustion air flow control of each furnace of a pressurized fluidized-bed boiler according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of main steam temperature control of the pressurized fluidized-bed boiler according to the embodiment of the present invention.

FIG. 3 is a boiler input command of a function generator 36 in FIG. 1;
It is a figure showing an example of a main steam temperature set value characteristic.

4 is a boiler input command of a function generator 37 in FIG. 1;
It is a figure showing an example of a main steam temperature deviation gain correction signal characteristic.

5 is a boiler input command of a function generator 38 in FIG. 1;
It is a figure showing an example of a boiler feed water flow rate set value characteristic.

6 is a boiler input command of function generator 52 in FIG. 1;
It is a figure showing an example of a fuel supply pump output command characteristic.

7 is a diagram showing an example of a characteristic of a dead zone of a main steam temperature deviation of the function generator 49 in FIG.

FIG. 8 is a configuration diagram of a combustion air flow rate control of each furnace in the pressurized fluidized bed boiler system of the related art.

FIG. 9 is a diagram showing a main steam temperature control method of a conventional once-through boiler.

FIG. 10 is a diagram showing an example of a steam system of a conventional once-through boiler.

[Explanation of symbols]

1a, 1b Furnace 2 Compressor 3a, 3b Air flow control device 4a, 4b Exhaust gas oxygen concentration meter 5a, 5b Superficial velocity meter 6a, 6b Fuel flow meter 7a, 7b Furnace air supply pipe 8a, 8b Fluidized bed 9a, 9b Furnace Outlet gas piping 10a, 10b
Fuel supply pipe 11, 14, 21, 42, 51, 96, 97 Adder 12 Furnace fuel ratio calculation divider 13 Fuel damper opening degree converter 15 Damper reverse operation signal function unit 16 Furnace outlet oxygen concentration deviation calculation subtraction Device 17 Oxygen concentration deviation-damper opening degree converter 18 Boiler outlet oxygen concentration meter 19 Oxygen concentration deviation air flow converter 20 Fuel flow air flow converter 22 Air flow regulator 23,75 Evaporator 24 Superheater 25,85 Reheating Vessels 27a, 27b
Pressure vessel 31 Boiler feedwater flow 32, 91 Boiler input command 33 Main steam temperature measured value 34, 39, 9
9 Subtractor 35, 50, 100 Proportional integrator 36, 37, 38, 49, 52, 95, 98, 102
Function generator 40 Multiplier 41 Proportional unit 43, 54 Automatic / manual switch 44 Feed water flow set value 45 Base feed water pump output command 46 Feed water pump output command 47 Main steam temperature set value 48 Gain correction signal 53 Base fuel pump output command 71 Feedwater pump 72 Feedwater heater 73 Energy saving device 74 Boiler furnace wall 76 Steam separator 77 Primary superheater 78 Superheater overheat reducer 79, 84 Superheater spray flow control valve 80 Secondary superheater 81, 86 Thermometer 82 High pressure Turbine 83 Reheater overheat reducer 87 Medium pressure turbine 92 Load command 93 Spray flow actual measurement 94 Main steam temperature deviation 101 Fuel flow command 103 Base fuel flow signal 104 Spray flow set value

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuyuki Yamamoto 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Inside the Kure Factory (72) Inventor Shuhei Akimoto 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Kure Factory Co., Ltd. (72) Koji Tomoyasu 6-9 Takara-cho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory F-term (reference) 3K064 AA08 AA11 AB01 AC06 AC07 AC13 AD01 AE02 BA13 3L021 AA04 BA08 CA01 DA07 DA25 DA26 EA04 FA12 FA13

Claims (6)

[Claims] An evaporator, a superheater and a reheater are arranged in a furnace, and a furnace in which at least an evaporator is arranged and a furnace in which at least a reheater is arranged among the evaporator, the superheater and the reheater. Furnace divided into at least two separate furnaces, at least two pressure vessels for individually storing each divided furnace, and means for adjusting the combustion air and fuel supply ratio sent to each furnace A pressurized fluidized-bed boiler, comprising: means for detecting the superficial velocity of each furnace, wherein the air for adjusting the flow rate of combustion air supplied to the pressurized fluidized-bed boiler according to at least the detection value of the superficial velocity detection means A pressurized fluidized-bed boiler comprising a flow control means. 2. An air supply distribution adjusting means which comprises an oxygen concentration measuring means at the outlet of each furnace and adjusts an air supply distribution to each furnace from the measured oxygen concentration at the furnace outlet by each oxygen concentration measuring means. 2. The method according to claim 1, wherein
A pressurized fluidized bed boiler as described. 3. A furnace in which an evaporator, a superheater and a reheater are arranged in a furnace, and among the evaporator, the superheater and the reheater, a furnace in which at least an evaporator is arranged and a furnace in which at least a reheater is arranged Furnace divided into at least two separate furnaces, at least two pressure vessels for individually storing each divided furnace, and means for adjusting the combustion air and fuel supply ratio sent to each furnace A method for starting a pressurized fluidized-bed boiler, comprising: when starting the boiler, adjusting a combustion air flow rate supplied to the pressurized fluidized-bed boiler according to the superficial velocity of each furnace to supply fuel and air to each furnace. A method for starting a pressurized fluidized-bed boiler, comprising adjusting the flow rate of combustion air in accordance with the oxygen concentration at the outlet of the boiler after the amounts become substantially equal. 4. A furnace in which an evaporator, a superheater and a reheater are arranged in a furnace, and among the evaporator, the superheater and the reheater, a furnace in which at least an evaporator is arranged and a furnace in which at least a reheater is arranged Furnace divided into at least two separate furnaces, at least two pressure vessels for individually storing each divided furnace, and means for adjusting the combustion air and fuel supply ratio sent to each furnace In the pressurized fluidized-bed boiler having the above, after starting the furnace having the evaporator, the steam generated in the evaporator is introduced into a superheater and a reheater arranged in a furnace other than the furnace having the evaporator, and Detects the amount of steam,
After detecting that the amount of introduced steam has reached a predetermined value or more, in the start-up process of starting a furnace equipped with a superheater and a reheater, the superficial velocity of each furnace and the oxygen concentration at the furnace outlet are predetermined. A method for starting a pressurized fluidized boiler, characterized in that the flow rate of air supplied to the boiler is controlled to a value. 5. The fuel flow rate of a pressurized fluidized-bed boiler comprising a furnace in which a heat transfer tube group in which a steam system has the form of a once-through boiler is disposed in a fluidized bed fluidized by fuel, and a pressure vessel containing the furnace. Control of a pressurized fluidized-bed boiler that controls the main steam temperature, which is determined by the balance between the height of the fluidized bed and the flow rate of the boiler feedwater to the heat transfer tube group, by adjusting the water-fuel ratio (the ratio of the flow rate of the boiler feedwater to the amount of heat supplied to the boiler feedwater) The method is based on controlling the main steam temperature by adjusting the fuel flow rate, and the fuel flow rate control is used as a backup in the case of an emergency in which the response to the main steam temperature is slow and the main steam temperature cannot be controlled. A method for controlling a pressurized fluidized-bed boiler, wherein a main steam temperature is controlled by adjusting a flow rate of a boiler feedwater having a fast response. 6. A boiler input command signal for a pressurized fluidized-bed boiler comprising a heat transfer tube group through which boiler feedwater flows, a furnace arranged in a fluidized bed for fluidizing the boiler fuel, and a pressure vessel containing the furnace. The boiler fuel flow rate is obtained based on the deviation between the fuel flow rate set value and the fuel flow rate measured value, and the boiler fuel flow rate is corrected by the deviation between the set value of the main steam temperature and the measured value to control the fuel flow rate. The base water supply flow rate is determined based on the deviation between the boiler water supply flow rate set value and the measured water supply flow rate value determined by the boiler input command signal. The fuel supply amount determined by the boiler input command signal is further corrected according to the deviation between the set value of the main steam temperature and the measured value, and the boiler feed water flow rate is corrected. Control method for pressure-type fluidized bed boiler and adjusting.