JPH0989207A - Method and device for controlling steam temperature in boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make separate regulating means unnecessary and attain cost down by a method wherein a bias amount is added to the objective value of temperature difference to employ it as the actual objective value of temperature difference. SOLUTION: A temperature difference objective value function device 5 receives the load commanding signal 4s of a boiler and outputs the temperature difference value signal 5s of a superheat reducer in the fuel ratio of standard coal, for example. A correcting coefficient function device 2 receives the load commanding signal 4s and outputs a correcting coefficient signal 2s based on a reference load. On the other hand, a correcting amount function device 1 receives the fuel ratio signal 7s of coal and outputs a correcting signal 1a based on the fuel ratio of the standard coal. A multiplier 3 receives the outputs of the correcting coefficient function device 2 and the correcting amount function device 1 to output a temperature difference bias amount signal 3s from the product of both outputs. An adder 6 receives the outputs of the temperature difference objective value function device 5 and the multiplier 3 and adds them to output the temperature difference actual objective value signal 5 as of the superheat reducer. The optimum actual objective value of temperature can be obtained in such a manner at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam temperature control and apparatus for a boiler which is applied to a once-through boiler for a prime mover product.

[0002]

2. Description of the Related Art A conventional once-through boiler will be described with reference to FIGS.

As shown in FIG. 7A, a furnace evaporation pipe 30, a low temperature superheater 32, and a high temperature superheater 34 are provided in the furnace for burning coal. And the furnace evaporation tube 30,
The steam / water separator 31, the low-temperature superheater 32, the superheat reducer 33, and the high-temperature superheater 34 are sequentially connected. In the figure, 35 is a drain line and 36 is a spray water line.

As shown in FIG. 7 (b), the steam is slightly cooled by the superheat reducer 33, reaches a specified temperature at the outlet of the high temperature superheater 34, and is sent to the steam turbine. In this control, as shown in FIG. 8, the load command signal 4s is made into the temperature difference (ΔT) target value signal 5s of the overheat reducer through the temperature difference target value function unit 5, and the flow rate of the spray water is controlled by this signal. Was there. The target value is determined so that the superheat degree of the fluid at the outlet A of the furnace evaporation tube 30 or the outlet A'of the steam separator 31 falls within a required range.

[0005]

In the dry operation range of the once-through boiler having the subcritical pressure range as the operation range in the above conventional apparatus, in order to suppress the in-plane temperature difference of the water wall of the furnace within the allowable range in terms of strength. Moreover, it is necessary to suppress the superheat degree at the outlet of the furnace evaporation tube 30 to a certain level or less. Also, it is necessary to ensure the minimum degree of superheat so that it does not fall to saturation.

Spray water is used as the method for adjusting the degree of superheat. However, when the type of coal used as fuel changes, the combustion characteristics and the fouling characteristics inside the furnace change, and the heat absorption rate of the furnace also changes.Therefore, a separate adjusting means other than spray water is provided and adjustment is performed using it. It was

[0007] With the recent destruction of the value of the actual product, there is a need to further reduce the cost, and thus it is required to omit the separate adjusting means which has been conventionally provided.

[0008]

The present invention employs the following means to solve the above-mentioned problems. (1) In the boiler steam temperature control method for determining the temperature difference target value of the boiler having the superheat reducer from the load command and controlling the flow rate of the spray water to the superheat reducer, the load command is used as a reference from the load command. The temperature difference target value of the overheat reducer in the fuel ratio of coal is calculated, the correction coefficient is calculated from the same load command based on the reference load, and the correction amount is calculated from the fuel ratio of coal based on the fuel ratio of the reference coal. A bias amount obtained by multiplying the obtained correction coefficient is added to the temperature difference target value of the overheat reducer to obtain an actual temperature difference target value of the overheat reducer.

In the above, the temperature difference target value of the overheat reducer at the fuel ratio of the reference coal is obtained from the load command.
Further, a correction coefficient is obtained from the same load command based on the reference load. Further, the correction amount can be obtained from the fuel ratio of coal based on the fuel ratio of standard coal. Next, the correction amount is multiplied by the correction coefficient to obtain the bias amount, which is added to the temperature difference target value of the overheat reducer and used as the actual temperature difference target value.

As described above, even if the fuel ratio of the coal used changes in various ways, the bias amount corresponding to it is calculated and added, so that the optimum actual temperature difference target value can always be obtained. That is, the outlet steam temperature is maintained within a required level range with respect to the fuel ratio which changes over a wide range due to the change in coal type. Therefore, no separate adjusting means is required, and the cost can be significantly reduced. (2) It has a temperature difference target value function unit that receives a load command signal of a boiler having an overheat reducer and outputs a temperature difference target value signal of the same coal heat ratio at the fuel ratio of the reference coal. In the steam temperature controller of the boiler that controls the flow rate of spray water to the superheat reducer, a correction coefficient function unit that receives the load command signal and outputs a correction coefficient signal based on the reference load, and a fuel ratio of coal A correction amount function unit that receives a signal and outputs a correction amount signal based on the fuel ratio of the reference coal, a multiplier that receives the output of the correction coefficient function unit and the correction amount function unit, the temperature difference target function unit, and And an adder that receives the output of the multiplier and outputs an actual temperature difference target value signal.

In the above, the temperature difference target value function receives the load command signal of the boiler and outputs the temperature difference target value signal of the overheat reducer at the fuel ratio of the reference coal. The correction coefficient function unit receives the same load command signal and outputs a correction coefficient signal based on the reference load.

On the other hand, the correction amount function unit receives the fuel ratio signal of coal and outputs a correction amount signal based on the fuel ratio of the reference coal. The multiplier receives the outputs of the correction coefficient function unit and the correction amount function unit, and outputs a bias amount signal from the product thereof. The adder receives the outputs of the temperature difference target value function unit and the multiplier, adds them, and outputs an actual temperature difference target value signal.

As described above, even if the fuel ratio of the coal used changes variously, the bias amount corresponding thereto is calculated and added, so that the optimum actual temperature difference target value can always be obtained. That is, the outlet steam temperature is maintained within a required level range with respect to the fuel ratio which changes in a wide range. Therefore, no separate adjusting means is required, and the cost can be significantly reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, the load command signal 4s is sequentially output through the temperature difference target value function unit 5 and the adder 6. The load command signal 4s is sent to the multiplier 3 via the correction coefficient function unit 2.

On the other hand, the coal fuel ratio signal 7s is sent to the adder 6 through the correction amount function unit 1 and the multiplier 3 in sequence.

In the above, the temperature difference target value function unit 5 receives the load command signal 4s of the boiler and outputs the temperature difference target value signal 5s of the overheat reducer at the fuel ratio of the reference coal, for example, as shown in FIG. . Further, the correction coefficient function unit 2 receives the same load command signal 4s and outputs a correction coefficient signal 2s based on the reference load (reference) as shown in FIG.

On the other hand, the correction amount function unit 1 receives the fuel ratio signal 7s of coal and outputs the correction amount signal 1s as shown in FIG. 4 based on the fuel ratio of the reference coal. The multiplier 3 receives the outputs of the correction coefficient function unit 2 and the correction amount function unit 1, and outputs a temperature difference bias amount signal 3s as shown in FIG. The adder 6 is a temperature difference target value function unit 5 and a multiplier 3
Is output and added to output the actual temperature difference target value signal 5as of the superheater reducer as shown in FIG. 6 (the case where the fuel ratio is larger than the reference coal).

As described above, even if the fuel ratio of the coal used changes variously, the bias amount corresponding to it is calculated and added, so that the optimum actual temperature difference target value can always be obtained. That is, the outlet steam temperature is maintained within a required level range with respect to the fuel ratio which changes in a wide range. Therefore, a separate adjusting means is not necessary, and a large cost reduction is possible. Note that if there is a separate adjusting means, fine adjustment is possible and effective.

[0020]

According to the present invention as described above,
Despite the fuel ratios of various coal types, the boiler outlet steam temperature can be maintained within a certain range without the aid of conventional individual regulation means. Therefore, the cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is an operation explanatory view of the same embodiment.

FIG. 3 is an operation explanatory view of the same embodiment.

FIG. 4 is an operation explanatory view of the same embodiment.

FIG. 5 is an operation explanatory view of the same embodiment.

FIG. 6 is an operation explanatory view of the same embodiment.

FIG. 7 is an explanatory diagram of a conventional boiler.

FIG. 8 is a block diagram of the conventional example.

[Explanation of symbols]

 1 correction amount function unit 2 correction coefficient function unit 3 multiplier 5 temperature difference target value function unit 6 adder 30 furnace evaporator 31 steam separator 32 low temperature superheater 33 superheat reducer 34 high temperature superheater 35 drain line 36 water supply line

Claims (2)

[Claims] 1. A steam temperature control method for a boiler, wherein a target temperature difference value of a boiler having a superheat reducer is obtained from a load command of the boiler, and the flow rate of spray water to the superheat reducer is controlled. The target temperature difference value of the overheat reducer in the fuel ratio of the standard coal is calculated from the above, the correction coefficient is calculated from the standard load from the same load command, and the fuel ratio of the coal is corrected based on the fuel ratio of the standard coal. A steam temperature control method for a boiler, characterized in that the amount of bias is obtained by multiplying the correction coefficient by the correction amount, and the bias amount is added to the temperature difference target value of the overheat reducer to obtain an actual temperature difference target value of the overheat reducer. 2. A temperature difference target value function unit for receiving a load command signal for a boiler having an overheat reducer and outputting a temperature difference target value signal for the fuel ratio of the reference coal, the temperature difference target value function unit having the same temperature difference target value. In the steam temperature control device of the boiler that controls the flow rate of spray water to the superheat reducer by the signal, a correction coefficient function unit that outputs the correction coefficient signal based on the reference load upon receiving the load command signal, and the coal A correction amount function unit for receiving a fuel ratio signal and outputting a correction amount signal based on the fuel ratio of the reference coal, a multiplier for receiving the correction coefficient function unit and the output of the correction amount function unit, and the temperature difference target function A steam temperature control device for a boiler, comprising: an adder that receives the outputs of the multiplier and the multiplier and outputs an actual temperature difference target value signal.