JP3830610B2 - Reheat steam control method for power generation boiler - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reheat steam control method for a power generation boiler, and more particularly to optimization of a reheat steam temperature and improvement of flame detection performance during load drop.
[0002]
[Prior art]
FIG. 3 shows a configuration of a conventionally known boiler apparatus. In this figure, 1 is a boiler furnace, 2 is a bottom of the boiler furnace 1, 3 is a first burner stage provided on the furnace wall of the boiler furnace 1, and 4 is disposed below the first burner stage 3. The second burner stage 5 is a wind box inlet damper for controlling the flow rate of the combustion air supplied to the first and second burner stages 3 and 4, 6 is a flue provided at the outlet of the boiler furnace 1, 7 Is a superheater provided in the flue 6, 8 is a reheater also provided in the flue 6, and 9 is a furnace bottom 2 and first and second burner stages that extract combustion exhaust gas from the flue 6. Exhaust gas recirculation fans 10 and 4 are recirculated, 10 is an air heater, 11 is a damper that mixes combustion exhaust gas into the combustion air supplied from the air heater 10 to each burner stage 3 and 4.
[0003]
In boiler apparatus having such a configuration, when the drop in the load at the time of t ₁ is instructed, as shown in FIG. 4 (a), in order to prevent an excessive increase of the outlet steam temperature of the superheater 7, the boiler holders pyrolytic In consideration of the above, as shown by the solid line in FIG. 4B, the fuel flow rate is lowered from the static characteristic shown by the broken line in FIG. As a result, the furnace outlet gas temperature becomes lower than that in a transient static state, and the steam temperature of the reheater 8 tends to decrease. In order to maintain the steam temperature of the reheater 8, conventionally, as shown in FIG. 4C, the recirculation amount of the exhaust gas supplied from the exhaust gas recirculation fan 9 to the furnace bottom 2 of the boiler furnace 1 is made transient. In general, the heat absorption in the boiler furnace 1 is suppressed and the reheat steam temperature is maintained at a necessary value as shown in FIG. 4 (f). In addition, in order to prevent overheating of the burner due to radiant heat from the inside of the furnace, the second burner stage 4 that stops with a load drop has a certain amount of air or air and combustion exhaust gas as shown in FIG. The air-fuel mixture is supplied.
[0004]
[Problems to be solved by the invention]
However, as shown by a broken line in FIG. 3, the recirculated exhaust gas 12 supplied from the furnace bottom 2 is biased toward the front wall and the rear wall of the boiler furnace 1 toward the burner port of the burner stage used for combustion. If the amount of recirculated exhaust gas supplied to the furnace bottom 2 is increased in order to form a flow, the amount of recirculated exhaust gas flowing into the flame ignition region of the burner increases and flame stability is impaired. As a result, the flame detection performance also deteriorates.
[0005]
The present invention has been made in order to solve the deficiencies of the prior art, and the problem is that a high reheat steam temperature can be maintained at the time of load drop, and flame stability and flame detection performance are achieved. It is in providing the reheat steam control method of the boiler for electric power generation which can improve.
[0006]
[Means for Solving the Problems]
The present invention for solving the above problems, provided with a plurality of stages of burners into the furnace, the power boiler formed by arranging the superheater and reheater in a flue, the load drop command to the boiler apparatus In the process in which the load on the boiler device is lowered to the commanded value after that, air or a mixture of air and combustion exhaust gas introduced into the furnace from a pause burner disposed below the burning burner The flow rate of the reheater was increased transiently to maintain the above temperature at the outlet of the reheater properly.
[0007]
Prior control of the flow rate of the air or the mixture of air and combustion exhaust gas introduced from the pause burner into the furnace based on a signal output from the boiler side operation control device or a load drop request from the turbine side be able to.
[0008]
When an appropriate amount of air or a mixture of air and combustion exhaust gas is transiently introduced into the furnace from the pause burner at the time of load drop, heat absorption in the boiler furnace 1 is suppressed and passes through the superheater and reaches the reheater. Since the amount of heat increases, the reheat steam temperature can be maintained at an appropriate high temperature. Further, when air or a mixture of air and combustion exhaust gas is introduced into the furnace from a dormant burner disposed below the burning burner, as shown in FIG. 1, the air or mixture 12 becomes boiler furnace. Since it is injected to the center of 1, the amount of air or air-fuel mixture flowing into the flame igniting portion of the burner is reduced, and flame stability and flame detection performance are improved. Further, as shown by a broken line in FIG. 1, the recirculated exhaust gas 13 introduced from the furnace bottom 2 is also converted into the boiler furnace 1 by the flow of air or the air-fuel mixture 12 introduced from the idle burner, as indicated by the broken line in FIG. 1. Therefore, the amount flowing into the flame ignition area of the burner is reduced. Therefore, also from this point, flame stability and flame detection performance are improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, based on FIG.1 and FIG.2, an example of the reheat steam control method of the boiler for electric power generation which concerns on this invention is demonstrated. FIG. 1 is a block diagram of a boiler device, and FIG. 2 is a graph showing a reheat steam control method according to the present invention.
[0010]
As is clear from FIG. 1, the boiler apparatus of this example is the same as the conventional boiler apparatus shown in FIG. 3 in terms of the overall configuration, and is provided on the boiler furnace 1 and the furnace wall of the boiler furnace 1. First and second burner stages 3 and 4, a wind box inlet damper 5 for controlling the flow rate of combustion air supplied to the first and second burner stages 3 and 4, a flue 6, and a flue 6 mainly includes a superheater 7 and a reheater 8, an exhaust gas recirculation fan 9, an air heater 10, and a damper 11.
[0011]
In boiler apparatus having such a configuration, when the drop in the load at t ₁ as shown in FIG. 2 (a) is commanded, in order to prevent an excessive increase of the outlet steam temperature of the superheater 7, FIG. 2 (b) As indicated by the solid line, the fuel flow rate is reduced. Up to this point, it is the same as the above-described prior art. In the present invention, in order to stabilize the flame of the first burner stage 3 during combustion and maintain good flame detection performance, as shown in FIG. The flow rate of the air or the air-fuel mixture 12 mixed with flue gas is increased transiently. Further, as shown in FIG. 2 (c), a certain amount of combustion exhaust gas 13 is supplied from the exhaust gas recirculation fan 9 to the furnace bottom 2 of the boiler furnace 1, and the boiler furnace 1 is supplied from the second burner stage 4 that is stopped. Combined with the air or air-fuel mixture 12 supplied to the boiler, the heat absorption in the boiler furnace 1 is suppressed, and the reheat steam temperature accompanying the reduction of the fuel flow rate is prevented from decreasing.
[0012]
When an appropriate amount of air or a mixture of air and combustion exhaust gas is transiently introduced into the furnace from the rest burner at the time of load drop, and the combustion exhaust gas is recirculated to the furnace bottom 2, heat absorption in the boiler furnace 1 is suppressed. Since the amount of heat passing through the superheater and reaching the reheater increases, the reheat steam temperature can be maintained at an appropriate high temperature. Further, when air or an air-fuel mixture 12 of air and combustion exhaust gas is introduced into the boiler furnace 1 from the second burner stage 4 that is disposed below the first burner stage 3 that is burning, FIG. 1, since the air or air-fuel mixture 12 is injected into the center of the boiler furnace 1, the amount of air or air-fuel mixture flowing into the flame ignition part of the burner is reduced, and flame stability and flame detection performance. And will be improved. Further, as shown by a broken line in FIG. 1, the recirculated exhaust gas 13 introduced from the furnace bottom 2 is also converted into the boiler furnace 1 by the flow of air or the air-fuel mixture 12 introduced from the idle burner, as indicated by the broken line in FIG. 1. Therefore, the amount flowing into the flame ignition area of the first burner stage 3 is reduced. Therefore, also from this point, flame stability and flame detection performance are improved.
[0013]
The above control may be performed based on a load drop request from the turbine side that supplies steam generated in the boiler. Preferably, as shown in FIG. This is performed based on a signal output from the control device. For example, when a boiler input acceleration signal (BIR) that rapidly decreases the fuel flow rate of the boiler is input, dynamic control can be performed. In this case, based on the boiler input acceleration signal, the flow rate of the air or the air-fuel mixture 12 introduced into the boiler furnace 1 from the second burner stage 4 can be controlled.
[0014]
In the above-described embodiment, the boiler apparatus having only the first burner group 3 and the second burner group 4 has been described as an example. However, the boiler apparatus having three or more burner groups is also controlled. Of course, it can be applied.
[0015]
【The invention's effect】
As described above, according to the present invention, when a suitable amount of air or a mixture of air and combustion exhaust gas is transiently introduced into the furnace from the pause burner at the time of load drop, heat recovery in the boiler furnace is suppressed, Since the amount of heat reaching the reheater through the superheater increases, the reheat steam temperature can be maintained at an appropriate high temperature. In addition, when air or a mixture of air and combustion exhaust gas is introduced into the furnace from a dormant burner disposed below the burning burner, the air or mixture is injected into the center of the boiler furnace. The amount of air or air-fuel mixture flowing into the flame ignition part of the burner is reduced, and flame stability and flame detection performance are improved. Moreover, since the recirculated exhaust gas input from the furnace bottom is also transported to the center of the boiler furnace 1 by the flow of air or air-fuel mixture input from the rest burner, the amount flowing into the flame ignition region of the burner is reduced. Therefore, also from this point, flame stability and flame detection performance are improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a boiler apparatus according to the present invention.
FIG. 2 is a control diagram of the boiler device according to the present invention.
FIG. 3 is a configuration diagram of a boiler device according to a conventional example.
FIG. 4 is a control diagram of a boiler device according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Boiler furnace 2 Furnace bottom 3 1st burner stage 4 2nd burner stage 5 Windbox entrance damper 6 Flue 7 Superheater 8 Reheater 9 Exhaust gas recirculation fan 10 Air heater 11 Damper 12 Air or air and combustion exhaust gas Mixture of 13 Recirculated exhaust gas

Claims (2)

In a power generation boiler with a multi-stage burner in the furnace and a superheater and reheater arranged in the flue , the load command of the boiler device is commanded after the load drop is commanded to the boiler device In the process of descending, the flow of air or the mixture of air and combustion exhaust gas is gradually increased from a dormant burner disposed below the burning burner, and the reheat is performed. A reheat steam control method for a power generation boiler characterized by maintaining the above temperature appropriately. 2. The reheat steam control method according to claim 1, wherein a signal output from a boiler- side operation control device or a turbine indicates a flow rate of air or a mixture of air and combustion exhaust gas introduced into the furnace from the pause burner. A reheat steam control method for a power generation boiler, characterized in that control is performed based on a load drop request from the side .

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