JP2831454B2 - Control device of circulating fluidized bed boiler - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating fluidized bed boiler, and more particularly to a circulating fluidized bed boiler suitable for maintaining a furnace bottom at appropriate values of fluidized bed temperature and steam pressure. It relates to a control device.

[Conventional technology]

The bed temperature of a fluidized bed boiler using heavy oil, coal, etc. as fuel is usually 800 to 900 ° C. In a fluidized bed boiler in which heat transfer tubes and steam pipes are embedded in this bed, the layers of the heat transfer tubes and steam pipes The medium heat transfer (heat transfer coefficient) is about 5 to 10 times larger than the heat transfer from the gas flow of the conventional boiler alone, and is characterized by a large amount of heat transfer.

Fluidized bed boilers have excellent heat transfer characteristics in the bed, so even low-grade coal such as sludge coal, which had previously been dumped in spilled mountains, can be effectively used as fuel for fluidized bed boilers. Incineration of these low-rank coals can also help reduce the volume of low-rank coals.
In recent years, fluidized bed boilers have been in the spotlight.

Fluidized bed boilers are of the bubbling type and the circulation type, and the circulating fluidized bed boiler circulates 40 to 100 times the amount of fuel supplied to the fuel supply amount. There is also a feature that can cope with load control by the amount of circulation.

Hereinafter, an outline of the circulating fluidized bed boiler will be described with reference to FIG.

Fuel and medium particle bunker 2 supplied from fuel bunker 1
Is supplied to the combustion furnace 3, while the combustion air is supplied from the combustion air supply pipe 4 to the primary air 5 supplied to the furnace bottom of the combustion furnace 3 and the secondary air supplied from the side of the furnace. Combustion with air 6 occurs. Primary air 5 and secondary air 6
The coarse particles scattered by the gas flow out of the combustion furnace 3, are collected by a primary separator 7 installed at the furnace outlet, and are collected by an L-shaped valve 8.
, And is returned to the combustion furnace 3 by the air rate blower 9 and the air rate air supplied from the air rate nozzle 11 from the air rate piping 10, and is recirculated.

On the other hand, the combustion gas that has passed through the primary separator 7 is
After the heat exchange with the economizer 13, fine particles remaining in the combustion gas are separated by the secondary separator 14, and the primary air 5, 2 supplied by the forced draft fan 16 is separated by the air furnace heater 15. After heat exchange with the combustion air such as the secondary air 6, the dust is removed by the dust collector 17, and the combustion gas is sucked by the induction ventilator 18 and discharged from the chimney 19 to the outside of the system.

In this circulating fluidized-bed boiler, a dense bed with a relatively high particle concentration is formed at the bottom of the furnace, but if the fluidized bed temperature in this dense bed is not properly controlled, the coal ash will melt and become massive, resulting in a fluidized bed. Will not function.

In FIG. 2, reference numeral 20 denotes a primary particle extraction pipe, 21 denotes a secondary particle extraction pipe, 22 denotes a drum, 23 denotes an air flow rate detector, 24 denotes a thick layer temperature detector, 25 denotes a steam pressure detector, and 26 denotes a steam pressure detector. A steam flow rate detector, 27 is a fuel flow rate detector, 28 is an air rate air flow rate detector, 29 is a call feeder, and 30 is an air rate air flow rate adjusting valve.

[Problems to be solved by the invention]

In the prior art circulating fluidized bed boiler, no consideration was given to properly controlling the temperature of the fluidized bed in the dense bed, and coal ash was melted and formed into a lump, and did not function as a fluidized bed. .

The present invention seeks to overcome the disadvantages of the prior art, and aims at reducing the fuel supply amount, the particle circulation amount, and the combustion air supply amount in all operating states including a rapid load change. It is an object of the present invention to provide a circulating fluidized-bed boiler control device that can be appropriately operated to maintain the temperature of a thick bed at a set value and maintain the steam pressure at a set value.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a temperature deviation feedback signal based on signals from a rich temperature setting device and a rich temperature detector, and a pressure deviation feedback signal based on signals from a steam pressure setting device and a steam pressure detector. A calculator for calculating a fuel supply amount demand signal from a fuel advance signal based on a signal from a steam flow rate detector, a function generator for obtaining an air amount demand signal from the fuel supply amount demand signal, a rich layer temperature setting device and a rich layer temperature setting device An air flow detector is provided to calculate the particle circulation amount demand signal from the temperature deviation feedback signal from the bed temperature detector and the circulation amount dynamic advance signal based on the signal from the steam flow amount detector and the fluid medium particle circulation amount advance signal. The control drive of the forced air ventilator is controlled by the air flow deviation signal between the air flow detection signal from the The call feeder is controlled by a fuel amount deviation signal between the fuel flow amount detection signal from the flow amount detector and the fuel supply amount demand signal, and the particles of the air rate air flow amount detection signal and the particle circulation amount demand signal from the air rate air amount detector are controlled. The air rate air flow control valve is controlled by the circulation amount deviation signal.

[Action]

With respect to the fuel supply amount and the combustion air supply amount, a base demand is given by a preceding signal for the evaporation amount, a feedback control signal based on the set values of the fluidized bed temperature and the steam pressure is added, and the fuel supply amount and Determine the supply of combustion air. Therefore,
Since the steam pressure can maintain the thermal balance, the steam pressure is maintained at the set value.

On the other hand, with respect to the amount of circulating fluid particles, a base demand is given by a preceding signal and a dynamic precedence signal for the amount of evaporation, and a feedback correction signal based on the set value of the temperature of the fluidized bed is added. Determine the amount.

This balances the amount of heat generated by the combustion of the fuel, the amount of heat transferred to the combustion furnace water wall, and the amount of heat transferred by the circulation of the medium particles, so that the temperature of the fluidized bed does not deviate from the set value.

Note that the circulation amount of the medium particles is increased or decreased by air-rate air.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First
FIG. 1 is a control system diagram of a circulating fluidized bed boiler according to an embodiment of the present invention.

In FIG. 1, reference numerals 23 to 30 indicate the same components as those in FIG.

31 is a thick bed temperature setting device, 32 is a steam pressure setting device, 33a, 3
3b, 33c, 33d, 33e are subtractors, 34a, 34b, 34c, 34d, 34e
Is a controller, 35a, 35b, and 35c are function generators, 36a and 36b are operation units, 37 is a control drive for the forced-air ventilator 16, 38 is a differentiator, 39 is a coefficient unit, 40 is a fuel advance signal, and 41 is fuel. Supply amount demand signal, 42 is the air amount demand signal, 43 is the fluid medium particle circulation amount advance signal, 44 is the circulation amount dynamic advance signal, 45 is the circulation amount demand signal, 46 is the steam flow rate detection signal, 46 is the rich bed temperature A detection signal, 48 is a rich layer temperature setting signal, 49 is a temperature deviation signal, 50 is a temperature deviation feedback signal, 51 is a steam pressure detection signal, 52 is a steam pressure setting signal, 53 is a steam pressure deviation signal, and 54 is a pressure deviation feedback. Signal, 55 is a fuel flow detection signal, 56 is a fuel deviation signal, 57 is an air flow detection signal,
58 is an air flow rate deviation signal, 59 is an air rate air flow rate detection signal, and 60 is a particle circulation amount deviation signal.

In such a structure, the steam flow rate detection signal 46 from the steam flow rate detector 26 is input to the function generator 35a, and is set as the fuel advance signal 40.

The thick layer temperature detection signal 47 from the thick layer temperature detector 24 and the thick layer temperature setting signal 48 from the thick layer temperature setter 31 are subtracters.
The temperature deviation signal 49 is generated by the controller 33a, the signal is processed by the controller 34a, and the temperature deviation feedback signal 50 is input to the calculator 36a.

The steam pressure detection signal 51 from the steam pressure detector 25 and the steam pressure setting signal 52 from the steam pressure setting device 32 are subjected to signal processing of the steam pressure deviation signal 53 by the subtractor 33b, and are processed by the controller 34b to perform pressure processing. The deviation feedback signal 54 is calculated by the computing unit 36a.
To enter.

In the computing unit 36a, the fuel preceding signal 40, the temperature deviation feedback signal 50 and the pressure deviation feedback signal 54 are provided.
Are added to obtain a fuel supply amount demand signal 41. This fuel supply amount demand signal 41 is converted into a fuel flow rate detection signal 55 from the fuel flow rate detector 27 and a fuel deviation signal 56 by a subtracter 33c, processed by a controller 34c, and controlled by a call feeder 29 to control the fuel flow rate. .

Regarding the control of the combustion air supply amount, the fuel supply amount demand signal 41 from the calculator 36a is input to the function generator 35b to generate the air amount demand signal 42, and the air flow detector
Subtracts the air flow deviation signal 58 from the 23 air flow detection signal 57
33d, the signal is processed by the controller 34d, and the amount of combustion air is controlled by the control drive 37 of the forced draft fan 16.

Next, the flow rate detection signal 46 from the steam flow rate detector 26 is used to obtain the fluid medium particle circulation amount advance signal 43 via the function generator 35c, and the steam flow rate detection signal 46 of the steam flow rate detector 26 is differentiated by the differentiator.
38 and input to the coefficient unit 39 to obtain the circulation amount dynamic leading signal 44,
It is input to the computing unit 36b. A subtractor 33a obtains a temperature deviation signal 49 between the thick layer temperature setting signal 48 from the thick layer temperature setter 31 and the thick layer temperature detection signal 47 from the thick layer temperature detector 24,
The signal is processed by the controller 34a and input to the computing unit 36b as a temperature deviation feedback signal 50.

The arithmetic unit 36b adds the fluid medium particle circulation amount advance signal 43, the circulation amount dynamic advance signal 44, and the temperature deviation feedback signal 50 to obtain a particle circulation amount demand signal 45,
The subtractor 33e obtains the particle circulation amount deviation signal 60 with the air-rate air flow rate detection signal 59 from the air-rate air flow rate detector 28, processes the signal with the controller 34e, and opens and closes the air-rate air flow rate adjustment valve 30. Control the circulation amount of the fluid medium particles.

In controlling the fuel supply amount and the combustion air supply amount, the fuel supply amount is determined not only by the steam pressure but also by the bed temperature of the fluidized bed, and the combustion air supply amount is controlled in association with the fuel supply amount. There is a feature in the point.

In the control of the amount of circulating medium particles, the amount of circulating particles is determined by focusing on the bed temperature of the fluidized bed. The change in the amount of circulating particles changes the particle density in the combustion furnace 1. Since the heat transfer to the combustion furnace 1 is dominated by the heat transfer accompanying the movement of the medium particles rather than the radiation, the particle density has a great influence on the amount of heat transfer to the water cooling wall of the combustion furnace 1.

The temperature of the fluidized bed is substantially determined by the heat generated by the combustion of the fuel, the amount of heat transferred to the water cooling wall of the combustion furnace 1, and the heat transfer caused by the circulation of the particles. The temperature of the fluidized bed can be maintained at a set value by appropriate control based on the amount of circulation, since it has a very large effect. For this reason, the control of the circulation amount of the medium particles is characterized in that the controllability of the bed temperature is improved by adding a dynamic advance control accompanying a change in the evaporation amount.

〔The invention's effect〕

According to the present invention, the bed temperature of the dense fluidized bed formed at the bottom of the combustion furnace can be maintained at the set value in all operation states including the time of a rapid load change. Inconvenient phenomena such as so-called agglomeration can be prevented, and stable operation can be achieved.

Also, good controllability can be expected with respect to the steam pressure, so that the steam pressure fluctuation can be suppressed even at the time of rapid load fluctuation, and the life consumption of the pressure-resistant thick wall portion of the boiler can be reduced.

[Brief description of the drawings]

FIG. 1 is a control system diagram of a circulating fluidized bed boiler according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a circulating fluidized bed boiler. 16… Insert ventilator, 23… Air flow detector, 24… Dense layer temperature detector, 25… Steam pressure detector, 26 …… Steam flow detector, 27 …… Fuel flow detector, 28… … Air-rate air flow detector, 29 …… Coll feeder, 30 …… Air-rate air flow control valve, 31 …… Thick layer temperature setter,
32 …… Steam pressure setting device, 35 …… Function generator, 36 …… Calculator, 40 …… Fuel advance signal, 41 …… Fuel supply amount demand signal, 42 …… Air amount demand signal, 43 …… Fluid medium Particle circulating amount advanced signal, 44… Circulating amount dynamic advanced signal, 45… Particle circulating amount demand signal, 50… Temperature deviation feedback signal, 54… Pressure deviation feedback signal, 55… Fuel flow rate detection signal, 56 ... fuel deviation signal, 57 ... air flow rate detection signal, 58 ... air flow rate deviation signal, 59 ... air rate air flow rate detection signal, 60 ... particle circulation quantity deviation signal.

Claims (1)

(57) [Claims] 1. The temperature of a dense bed having a high media particle density formed at the bottom of a circulating fluidized bed boiler for circulating a fluidized medium in a combustion furnace, and the fluid pressure of water / steam for cooling the combustion furnace,
In the apparatus for maintaining a constant value by a fuel supply amount, a combustion air supply amount, and a flowing medium particle circulation amount, a temperature deviation feedback signal based on signals from the rich bed temperature setting device and the rich bed temperature detector, and a steam pressure setting. Calculator that calculates the fuel supply amount demand signal from the pressure deviation feedback signal based on the signal from the heater and the steam pressure detector, and the fuel advance signal based on the signal from the steam flow detector, and the air amount demand signal from the fuel supply amount demand signal From the function generator, the temperature difference feedback signal from the thick bed temperature setter and the thick bed temperature detector, and the circulating amount dynamic leading signal and the flowing medium particle circulating amount leading signal based on the signal from the steam flow rate detector. An arithmetic unit that calculates the circulation flow demand signal is provided, and the air flow between the air flow detection signal from the air flow detector and the air flow demand signal is provided. The control drive of the push-in ventilator is controlled by the amount deviation signal, the call feeder is controlled by the fuel amount deviation signal between the fuel flow amount detection signal from the fuel flow amount detector and the fuel supply amount demand signal, and from the air rate air amount detector A control device for a circulating fluidized-bed boiler, wherein the air-circulation air flow control valve is controlled by a particle circulating amount deviation signal between the air circulating air flow detection signal and the particle circulating amount demand signal.