JP3188010B2 - Control method of coal-fired boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a coal-fired boiler adapted to the properties of coal.

[0002]

2. Description of the Related Art Conventionally, control for automatically changing the control elements of a boiler according to the properties of coal has not been performed.

[0003]

In a coal-fired boiler, the characteristics of the boiler greatly change depending on the properties of the coal burned in the boiler. For this reason, if the set values of the boiler control elements such as the gas recirculation amount, the burner tilt, the gas distribution damper or the spray amount to the generated steam remain the same, the enthalpy at the furnace wall outlet of the boiler and the boiler outlet Steam temperature control became unstable, and it was difficult to control in an appropriate range. Specifically, the enthalpy of the furnace wall outlet is low for low volatile coal or high fuel ratio coal, and the steam temperature at the reheater outlet tends to be high. The enthalpy tends to be high, the steam temperature at the outlet of the reheater tends to be low, and the boiler characteristics differ greatly.

An object of the present invention is to provide a method for controlling a coal-fired boiler that can perform appropriate control depending on the characteristics of coal.

[0005]

According to the present invention, there is provided a method for controlling a coal-fired boiler, comprising: a fuel ratio, which is a ratio of fixed carbon and volatile matter of coal, a ratio of carbon to hydrogen of coal, or a value of volatile matter content of coal. based on gas recirculation amount is controlled elements of the boiler, burner tilt, changing either the set value at a minimum of spray flow to the gas distribution dampers and steam generated, the boiler
Controls the enthalpy at the fire wall outlet and the steam temperature at the boiler outlet
Vinegar Rukoto and features.

[0006]

The characteristics of the boiler are as follows: low-volatile coal with low volatile content or low fixed-carbon and volatile ratio fuel ratio or high coal-to-hydrogen ratio The heat absorption is low and the enthalpy at the furnace wall outlet tends to be lower than an appropriate value. In the present invention, the fuel ratio is the ratio of fixed carbon and volatile matter of coal or the ratio of carbon to hydrogen of coal is high, and the content of carbon is high, or the value of volatile matter content of low coal is low. When the fuel is burned, at least one of the set values of the control elements of the boiler is changed based on the value of the fuel ratio of coal, the ratio of carbon to hydrogen, or the value of the volatile matter content of coal. That is, the control elements of the boiler
That is , the gas recirculation amount is small, the burner tilt is downward, the spray flow rate to the generated steam is large, and at least one of the gas distribution dampers on the reheater side and the like is set in the closing direction. Thus, it is possible to control so as to become an appropriate value steam temperature of boiler outlet, such as enthalpy and reheater outlet of the furnace wall outlet increased heat absorption rate in the furnace wall.

On the other hand, in the case of highly volatile coal or coal having a low carbon content, heat absorption at the furnace wall is large, and the enthalpy at the furnace wall outlet tends to be higher than an appropriate value. In the present invention, the fuel ratio or the ratio of coal to carbon is low when the carbon content is low, or when the high volatile content coal having a high volatile content of coal is burned, the fuel ratio of the coal, Based on the ratio of hydrogen to carbon or the value of the volatile content of the coal, at least one of the setting values of the control elements of the boiler is reversed from that of the low volatile coal or the coal with a high carbon content. To change. That is, among the control elements of the boiler, the gas recirculation amount is large, the burner tilt is upward, the spray flow rate to the generated steam is small, and the gas distribution damper on the reheater side is set in the opening direction. Do at least one of them. Thus, it is possible to control so as to become an appropriate value steam temperature of boiler outlet, such as enthalpy and reheater outlet of the furnace wall outlet reduces the heat absorption rate at the furnace wall.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. In FIG. 1, reference numeral 1 denotes a boiler, and a plurality of burners 2 that can be tilted in the vertical direction are provided in a furnace of the boiler 1 whose tube wall forms an evaporator. At the outlet side of the boiler 1, a superheater 6 and a reheater 7 to which bleed air such as a turbine is supplied are installed so as to be parallel to the combustion gas flow of the boiler 1. On the downstream side of the vessel 7,
Gas distribution dampers 5 and 4 for adjusting the flow rate of the combustion gas passing therethrough are provided. One end of a pipe 8 having a gas recirculation fan 3 is connected to a flue 9 for discharging combustion gas from the boiler 1, and the other end is connected to a position below the burner 2 of the furnace of the boiler 1. Of the combustion exhaust gas discharged from the boiler 1 by the boiler 1
Is recirculated to the furnace.

FIG. 2 shows a water / steam system of the boiler in the present embodiment. The feed water heated by the economizer 15 is supplied to an evaporator provided in the boiler furnace 14 to become steam. This steam is superheated by the primary superheater 13, the secondary superheater 12, and the tertiary superheater 11 in the boiler. In the steam passage between the primary superheater 13 and the secondary superheater 12 and the steam passage between the secondary superheater 12 and the tertiary superheater 11, a part of the feed water is supplied through the flow control valves 17a and 16a. Primary overheat reducer 17 and secondary overheat reducer 16
Is provided.

When burning high volatile coal or coal having a low carbon content in the boiler 1, the amount of heat absorbed in the furnace 14 in FIG. 2 is increased, the enthalpy at the furnace wall outlet is increased, and the superheater outlet is increased. The steam temperature is lower. In the present embodiment, when such coal is burned, a boiler (not shown) based on the fuel ratio, which is the ratio of fixed carbon and volatile matter of coal, the ratio of carbon to hydrogen, or the value of volatile matter content of coal is used. The control device controls the control elements of the boiler. That is, the burner 2 is tilted upward, the recirculation amount of the combustion exhaust gas of the boiler by the gas recirculation fan 3 is increased, the gas distribution damper 4 on the reheater side is set in the opening direction, and the flow control valve 17a is set. To reduce the spray flow rate of the water supply to the primary superheat reducer 17. As a result, the heat absorption ratio in the furnace 14 can be reduced to make the enthalpy at the furnace wall outlet an appropriate value, and the steam temperature at the reheater outlet can be made an appropriate value.

On the other hand, when coal having a low volatile content or a high carbon content is burned in the boiler 1, the amount of heat absorbed by the furnace 14 is reduced, the enthalpy at the furnace wall outlet is reduced, and the steam at the superheater outlet is reduced. The temperature rises. In the present embodiment, when such coal is burned, the boiler control device (not shown) controls the control element of the boiler based on the fuel ratio of the coal, the ratio of carbon to hydrogen, or the value of the volatile matter content of the coal. I do. That is, the burner 2 is tilted downward to reduce the recirculation amount of the combustion exhaust gas of the boiler by the gas recirculation fan,
The gas distribution damper on the reheater side is set in the closing direction, and the flow control valve 17a is controlled to increase the spray flow rate of the water supply to the primary superheat reducer 17. Thereby, the furnace 14
, The enthalpy at the furnace wall outlet and the steam temperature at the reheater outlet can be set to appropriate values.

In this embodiment, one example of the set values of the control elements of the boiler based on the fuel ratio of the burning coal is shown in FIGS.
And FIG. By inputting the properties of the coal to the boiler control device, the control elements of the boiler are automatically controlled and their set values are changed.

In this embodiment, the tilt of the burner is changed, the recirculation amount is adjusted, the opening or closing direction of the gas distribution damper is set, and the primary desuperheater is changed. It is also possible to use a combination of changing the spray flow rate, perform one of them, or perform some of them.

[0014]

According to the present invention, as described in the claims, the fuel ratio of coal, the ratio of carbon to hydrogen or the value of its volatile content is used as a control index, and the manipulated variable and
Gas recirculation, which is the control element of the boiler , and the burner
Filter, gas distribution damper and spray flow rate to generated steam
By changing at least one of the set values, the enthalpy at the boiler fire wall outlet and the steam temperature at the boiler outlet can be automatically controlled to appropriate ranges regardless of the properties of the coal.

[Brief description of the drawings]

FIG. 1 is a layout view of a boiler to which an embodiment of the present invention is applied.

FIG. 2 is a system diagram of water and steam of a coal-fired boiler to which the embodiment is applied.

FIG. 3 is a graph showing an example of a relationship between a coal fuel ratio and a set value of a primary spray flow rate in the embodiment.

FIG. 4 is a graph showing an example of a relationship between a coal fuel ratio and a set value of a gas recirculation amount in the embodiment.

FIG. 5 is a graph showing an example of a relationship between a fuel ratio of coal and a set value of a tilt of a burner in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler 2 Burner 3 Gas recirculation fan 4,5 Gas distribution damper 6 Superheater 7 Reheater 8 Pipeline 9 Flue 11 Tertiary superheater 12 Secondary superheater 13 Primary superheater 14 Furnace 15 Energy saving device 16 Secondary Superheat reducer 17 Primary superheat reducer 16a, 17a Flow control valve

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F23N 5/00 F22B 35/00

Claims (1)

(57) [Claims] 1. A gas recirculation amount which is a control element of a boiler based on a value of a fuel ratio which is a ratio of fixed carbon and volatile matter of coal, a ratio of carbon and hydrogen of coal or a content of volatile matter content of coal. burner tilt, at a minimum of spray flow to the gas distribution damper and the steam generated by changing one of the set value, the boiler
Controls the enthalpy at the fire wall outlet and the steam temperature at the boiler outlet
Coal control method of the boiler and wherein to Rukoto.