JPS6336849A - Method of starting mill in once-through boiler - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for starting a mill in a once-through boiler regarding the starting timing of the first mill to start when a plurality of mills that supply fuel to the once-through boiler are sequentially started. It is something.

[Conventional technology]

A once-through boiler operates in a wet mode and a dry mode. In the wet mode, as shown in FIG. A recirculation line is used to connect the tank 4 and recirculate the water in the separation tank 4 with a recirculation pump 5, and a spray device 7 is used to connect the water supply pipe 6 to the furnace 1 to the steam pipe 2. In a configuration in which water is sprayed, the recirculation pump 5 is operated until the furnace 1 warms up to recirculate the water in the separation tank 4, and the steam separated by the steam separator 3 is transferred to the steam pipe 2. The air is heated in a superheater 8 and then guided to a turbine 9. At this time, furnace 1
The amount of fuel injected into the tank is adjusted by the steam pressure signal from the steam pressure gauge 10, and the spray water of the spray device 7 is controlled by the signal from the steam thermometer 11 (-
It is.

In addition, in the dry mode, after the furnace 1 has warmed up, all the steam is discharged from the furnace 1, so as shown in Fig. 4, the steam separator in the wet mode is 3. Since the separation tank 4 is not used, it is operated without a recirculation line, and at this time, the amount of fuel input is switched so as to be regulated by the steam thermometer 11.

On the other hand, the pulverized coal device that supplies fuel to the furnace 1 has a fifth
As shown in the figure, a plurality of burner groups 12 installed in the furnace 1
Each mill 13 installed in accordance with
The primary hot air duct 16 that introduces primary hot air via the air preheater 15 is connected in sequence, and the primary cold air duct 17 that bypasses the air preheater 15 is connected to the primary hot air duct 1.
6, and introduces primary air consisting of primary hot air and primary cold air into the mill 13, and the pulverized coal pulverized in the mill 13 is conveyed by the primary air and guided to the burner group 12, It is designed to be fed into the furnace 1 as fuel.

As mentioned above, the mills 13 installed in each of the burner groups 12 of the furnace 1 are started one by one to supply fuel to each burner group and cause combustion in the furnace 1, but especially at the beginning. For mills that start up in
The primary air temperature inside the mill does not rise even after startup due to the fact that the mill is cold, and the mill outlet air temperature, which affects the raw coal pulverizing performance of the mill 13, does not easily reach a predetermined temperature (for example, 65C). Inside the mill, the raw coal is not dried sufficiently, so the pulverization of the raw coal is poor, resulting in a delay in coal output, making the amount of coal output inconsistent, and making it difficult to predict the amount of fuel input to the furnace 1. There is.

Therefore, when starting the first mill among a plurality of mills, the timing of starting it becomes important.

Conventionally, the first mill was started when the once-through boiler was in the dry mode.

[Problem that the invention seeks to solve]

However, in the dry mode of a once-through boiler, only steam flows in the steam pipe 2, so the heat transfer surface is not constant with respect to the length of the steam pipe, and the heat transfer surface changes due to fluctuations in the amount of fuel. As a result, the response of steam temperature control based on fuel amount is delayed. Therefore, when the once-through boiler is in dry mode, if the amount of fuel input to the boiler is not clearly known, the steam temperature cannot be controlled, and the low steam temperature may interfere with the operation of the turbine 9. In the conventional method of starting the first mill during mode, the amount of coal output from the first mill is not constant, making it more difficult to predict the amount of fuel and making it impossible to control the steam temperature as described above. This caused problems with turbine operation.

Therefore, the present invention focused on the fact that when a once-through boiler is in wet mode, the heat transfer surface is fixed with respect to the length of the steam pipe, so even if the fuel amount fluctuates, there is little effect on the steam temperature. This is an attempt to solve the above-mentioned conventional problem by starting the first mill among the mills when the prediction of the fuel amount is incorrect but the influence on the steam temperature is small.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention is configured to check the load on a once-through boiler, the presence or absence of water level in a separation tank that stores water separated from steam, and whether a recirculation pump that recirculates water in the separation tank is in operation. It uses the data as data to determine whether it is in dry mode or wet mode, and in wet mode, it issues a start command to the first mill to start up first among the multiple mills, and starts the first white mill. Let it start.

[For production]

When a once-through boiler is in wet mode, the heat transfer surface is fixed because there is water in the steam pipes, so even if the amount of fuel input from the mill changes, there is little effect on the steam temperature, and the coal output from the first mill is There is no problem even if the amount is not constant.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an apparatus for carrying out the present invention.
A data section I determines whether the once-through boiler is in wet mode or dry mode, a mode determination section ■ determines the mode based on data from the data section ■, and a mode determination section ■ determines whether the wet mode is selected. When the determination is made, a start command is issued to the first mill, and the mill control device NnI is configured to control the mill based on this command.

The wet mode of a once-through boiler is when the boiler is started, operating at low load, when the load is 20% or lower, the water level in the separation tank 4 is above zero, and the recirculation pump 5 is in operation. is driving. Therefore, the data section ■
The load, the water level in the separation tank 4, and whether the recirculation pump 5 is running or not are output as data, and this data is sent to the mode determination section H. The mode determination unit ■ determines whether it is in dry mode or wet mode based on the input data, and if it is in wet mode, it issues a start command for the first mill and the mill control device ■ determines whether it is in dry mode or wet mode. Primary air is introduced into the mill for the first pewter to start it up.

When starting the first mill, since the primary hot air duct 16 (see Figure 5) is cold as described above,
It is most difficult to predict the amount of fuel to the boiler because the primary air temperature in the second mill is low and the raw coal is not dried sufficiently, the raw coal has poor pulverization, and there is a delay in coal output. . Shigashi,
As shown in Figure 2, when the once-through boiler is in wet mode,
In the steam pipe 2, the steam S and water W are separated by the steam separator 3, and the water W does not fluctuate, and the heat transfer surface remains fixed and does not fluctuate even if the fuel amount fluctuates. The influence on the steam temperature is significantly less than in the dry mode, and the spray device 7 to the steam pipe 2 is independent and can absorb fluctuations in steam temperature, so it is recommended to start the first mill at this time. let As a result, when the amount of coal output from the first mill becomes constant and the amount of fuel can be determined, the dry mode is activated, and the amount of input fuel can be clearly determined and the steam temperature can be controlled.

Note that for the second and subsequent mills, since the secondary hot air duct 16 is heated, the amount of coal output can be determined, and the above-mentioned problem does not occur.

〔Effect of the invention〕

As described above, according to the method of the present invention, the first mill among the plurality of mills is started when the once-through boiler is in the wet mode, so that the primary hot air duct to the first mill to be started is cooled. As a result, the mill outlet air temperature does not easily reach the specified temperature, and as a result, the amount of coal produced is not constant, and the amount of fuel input to the boiler cannot be clearly determined. Moreover, in the dry mode, the amount of input fuel can be clearly grasped, and the steam temperature can be controlled, eliminating the risk of interfering with the operation of the turbine.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a device implementing the present invention, Fig. 2 is an explanatory diagram showing the internal state of the steam pipe in the wet mode of a once-through boiler, and Fig. 3 is a schematic diagram showing the system in the wet mode of the once-through boiler. 4 is a schematic diagram showing a system of a once-through boiler in dry mode, and FIG. 5 is an example diagram of a pulverized coal apparatus. ■...Data section, ■...Mode judgment section, III...
・Mill control device, 1...furnace, 2...steam pipe, 3.
...Steam water separator, 4...Separation tank, 5...Recirculation pump, 9...Turbine, 12...Burner group, 13
...mil, 16...-secondary hot air duct.

Claims (1)

[Claims] 1) The load of the once-through boiler, the presence or absence of water level in the separation tank that stores water separated from steam, and whether or not the recirculation pump that recirculates the water in the separation tank is in operation are used as data to determine whether the water is in dry mode or not. 1 to determine when in wet mode and start first among multiple mills in wet mode
A method for starting a mill in a once-through boiler, comprising issuing a start command to a first mill and starting the first mill.