JPH0660564B2 - Air-fuel mixture controller - Google Patents

Description

TECHNICAL FIELD The present invention relates to an air-fuel mixture control device, and is used in a waste heat recovery power plant having an air-fuel mixture system.

2. Description of the Related Art An example of a conventional waste heat recovery power plant system will be described with reference to FIG.

In FIG. 4, the condensate condensed in the condenser 1 is sent to the mixed air flasher 3 by the condensate pump 2 and mixed there with hot water. After that, it is sent to the feed water preheater 5 and the boiler attached feed water preheater 6 through the feed water distribution valves 7 and 8 by the feed water pump 4, where it is heated by the waste heat source and temperature adjusted by the temperature difference controller 9. The feed water control valves 12 and 1 are fed to the No. 1 boiler 10 and No. 2 boiler 11, respectively.
Supplied through 3.

Here, No. 1 boiler 10 exemplifies a boiler having the feedwater preheater 6, and No. 2 boiler 11 exemplifies a boiler having only an evaporation section.

Since each boiler is a waste heat recovery type boiler, it is heated by a waste heat source (not shown) to generate steam. These steams are collected in the main steam pipe 14, are sent to the turbine 16 through the regulator valve 15, work there, enter the condenser 1, and return to the condensate.

When the waste heat recovered in the feed water in the feed water preheaters 5 and 6 is obtained in a larger amount than the feed water amount required for the boilers 10 and 11, the temperature control is performed by the feed water temperature controller 18 provided in the main feed pipe 17. The valve 19 is opened, and hot water is introduced into the air-fuel mixture flasher 3.

In the air-fuel mixture flasher 3, hot water is flushed, and the generated steam is mixed into the intermediate stage of the turbine 16 through the air-mixing stop valve 20 to improve the recovery rate of waste heat.

The hot water relief valve 21 is activated when the turbine is started or when the air mixture is stopped.
The surplus hot water is released to the condenser 1.

Problems to be Solved by the Invention In the conventional method, when the turbine 16 shifts to the independent speed control operation, or when the load is low, the air-fuel mixture operation cannot be performed. The feed water temperature control valve 19 is closed to stop the air-fuel mixture. Then, the hot water release valve 21 is opened to treat the hot water supplied to the air-fuel flusher 3, and the hot water is dumped to the condenser 1. As a result, the condensate system such as the condenser 1 and the condensate pump 2 must suddenly process a large amount of condensate. For this reason, there is a waste of having to install excessive equipment for a hot water dump that is not normally used. In particular, in a low temperature waste heat recovery type plant, the amount of hot water dump becomes excessively large, which may cause restrictions on the plant configuration.

Due to the structure of the turbine, it is not possible to increase the air-fuel mixture indiscriminately, so it is necessary to adjust the air-fuel mixture amount according to the turbine load, but in the past there was no suitable method.

Means for Solving the Problems According to the present invention, the allowable air-fuel mixture amount according to the turbine operating system and the turbine load is programmed, and the hot water amount to the air-fuel mixture flusher (that is, the air-fuel mixture vapor amount) is monitored and controlled. A device is installed to suppress an excessive amount of air-fuel mixture.

When the suppression of air-fuel mixture is activated, the set temperature for hot water release control is temporarily changed to limit an excessive hot water dump.

In addition, the feed water temperature is monitored, and if the feed water temperature rises excessively,
By operating a bypass adjustment device that temporarily bypasses the waste heat source of the waste heat boiler, heat recovery from the low temperature heat source is temporarily suppressed.

Function Calculate the allowable air-fuel mixture amount during turbine independent speed control operation or normal turbine operation according to the turbine load, and set the allowable air-fuel mixture amount according to the turbine operation method. On the other hand, the amount of air-fuel mixture is estimated from the amount of hot water at the inlet of the air-fuel mixture flusher, and the allowable amount of air-fuel mixture is monitored for comparison. If the amount of hot water (that is, the amount of actual mixed air vapor) becomes excessive, the opening degree of the hot water control valve is suppressed. As a result, it is possible to ensure the safety of the turbine, because it is not necessary to mix the steam in an amount larger than the amount of the mixed steam allowed in the turbine.

When the suppression of the air-fuel mixture amount is activated, the hot water escape amount increases, so the set value of the feed water temperature control is temporarily increased to minimize the opening degree of the hot water escape valve. This eliminates the waste of releasing the recovered waste heat to the condenser and prevents an excessive load on the condensate system.

Even in the above case, there is a possibility that the waste water heating amount and the recovered heat amount will not be balanced and the feed water temperature may rise excessively.Therefore, the feed water temperature should be monitored.If the feed water temperature rises excessively, the bypass device of the waste heat source should be installed. Open to reduce the amount of waste heat recovered and balance. At this time, first, the low temperature waste heat source of the feed water preheater whose main purpose is hot water generation is bypassed, and if necessary, the waste heat source of the feed water preheater attached to the boiler is bypassed.

This allows the turbine to generate the required power,
It is possible to suppress only the air-fuel mixture that must be suppressed in the operation of the turbine, and to minimize the amount of hot water released to the condenser. This naturally prevents an excessive load on the condensate system and makes it unnecessary to install an excessive amount of equipment.

Example FIG. 1 shows an example of a waste heat recovery power plant to which the device according to the present invention is applied. In the figure, reference numeral 1 is a condenser, 2
Is a condensate pump, 3 is a mixture flusher, 4 is a water supply pump,
5 is a water supply preheater, 6 is a water supply preheater attached to a boiler, 7 and 8 are water supply distribution valves, 9 is a temperature difference controller, 10 is a boiler with water supply preheater, 11 is a boiler, 12 and 13 are water supply control valves,
14 is a main steam pipe, 15 is a control valve, 16 is a turbine, 17
Is a main water supply pipe, 18 is a water supply temperature controller, 19 is a water supply temperature control valve, 20 is a mixture stop valve, 21 is a hot water relief valve, 22 is a main steam pressure controller, 23 is a generator, and 24 is a generator. Output meter, 2
5 is a program setter for normal operation, 26 is a program setter for independent speed control operation, 27 is an independent operation detector, 28 is a signal switcher, 29 is a low signal selector, 30 is a signal switcher, 31
Is a bypass device for the water supply preheater, 32 is a temperature setter, 33
Is a temperature detector, 34 is an override relay, and 35 is a bypass device.

The condensate condensed in the condenser 1 is sent to the mixed air flasher 3 by the condensate pump 2 and mixed there with hot water.
After that, it is sent by the feed water pump 4 to the feed water preheater 5 and the boiler attached feed water preheater 6 through the feed water distribution valves 7 and 8, where it is heated by the waste heat source and the temperature difference controller 9
The temperature of the water is controlled by the water supply control valves 12 and 13 to the No. 1 boiler 10 and No. 2 boiler 11. The No. 1 boiler 10 is a boiler having a water supply preheater 6,
The No. 2 boiler 11 exemplifies a boiler having only an evaporator.

Each boiler is heated by a waste heat source (not shown) to generate steam. These steams are collected in the main steam pipe 14,
The air is sent to the turbine 16 through the regulator valve 15, works there, enters the condenser 1, and returns to the condensate. When the waste heat recovered in the feed water in the feed water preheaters 5 and 6 is obtained in a larger amount than the feed water amount required for the boilers 10 and 11, the temperature is controlled by the feed water temperature controller 18 provided in the main feed pipe 17. The control valve 19 is opened, and hot water is introduced into the air-fuel mixture flasher 3. In the air-fuel mixture flasher 3, hot water flushes, and the generated steam is mixed into the intermediate stage of the turbine 16 through the air-mixing stop valve 20. As a result, particularly low-temperature waste heat is collected, which contributes to the improvement of the heat recovery rate.

The hot water release valve 21 releases excess hot water to the condenser 1 when the turbine is started or the air-fuel mixture is stopped.

In such a waste heat recovery plant, in order to effectively utilize the heat recovered by the feed water preheaters 5 and 6 and the boilers 10 and 11, the main steam pressure controller 22 usually provided in the main steam pipe 14 is used.
Thus, the regulator valve 15 is controlled to effectively introduce the generated steam amount into the turbine 16. A so-called front pressure control operation is performed.

For some reason, when the turbine 16 shifts to the independent speed control operation, the amount of air-fuel mixture is limited due to the necessity of ensuring the speed control function of the turbine 16. Further, in order to ensure the safe operation of the turbine 16, there is an air-fuel mixture amount according to the turbine load, and it is impossible to increase only the air-fuel mixture amount indiscriminately.

Therefore, the load of the turbine 16 is measured by the generator output meter 24 as the output of the generator 23, and the allowable air-fuel mixture amount is calculated and set by the program setters 25 and 26 according to the turbine output. The setting device 25 sets the allowable air-fuel mixture amount during normal operation, and the setting device 26 sets the allowable air-fuel mixture amount during independent speed control operation. An example of the program setting is shown in FIG. Whether the turbine 16 and the generator 23 are in parallel operation or in isolated operation is detected by an isolated operation detector 27, and the signal switch 28 is operated to select the setter 26 or 27. The low signal selector 29 monitors the selected allowable mixed air amount signal and the control signal from the feed water temperature controller 18, and if a temperature signal exceeding the allowable mixed air amount signal is transmitted, it is immediately permitted. The air-mixed amount signal is selected, the opening degree of the feed water temperature control valve 19 is limited, and the hot water amount (that is, the air-mixed amount) is suppressed.

If only the air-fuel mixture amount is suppressed, the feed water temperature rises. Therefore, when the islanding operation detector 27 detects the islanding speed control operation, the signal switching device 30 is also operated at the same time, and the bypass device 31 is changed to the allowable air-fuel mixture signal. Open to a commensurate degree to reduce the amount of waste heat recovered. At this time, first of all, it is important to operate the bypass device 31 of the system of the feedwater preheater 5 whose main purpose is to generate hot water so as to suppress the air-fuel mixture amount. Further, in order to prevent the waste heat collected at all from being released to the condenser 1 through the hot water relief valve 21, the feed water temperature controller 18
The temperature setting device 32 is operated at the same time as the signal switching device 30 is switched to raise and change the set temperature to the upper limit temperature allowed by the boilers 11 and 12. If the feed water temperature rises even if these are operated, it is confirmed that the temperature detector 33 detects an excessive rise in the feed water temperature and the islanding operation detector 27 detects the islanding speed control operation. Above, by operating the override relay 34, to drive the bypass device 35 of the boiler 10 with a feedwater preheater, to fully open the bypass device 35,
The heat recovery of the last water preheater 6 is suppressed.

As a result, it is possible to suppress the amount of air-fuel mixture according to the operating method and load of the turbine 16 and the generator 23, and to suppress the release of hot water to the condenser 1 to the minimum. Therefore, the safety of the operation of the turbine 16 can be ensured, and it becomes unnecessary to make the installed capacity of the condensate system excessive.

The bypass devices 31 and 35 will be specifically described with reference to FIGS. 3a to 3c, taking a case where waste heat source is waste gas as an example.

The bypass device 31 of the feed water preheater 5 is, as shown in FIG. 3a,
A bypass duct 311 and a bypass damper 312 provided therein are provided, and a ventilator 51 and an inlet damper 52 thereof are provided on the downstream side of the feedwater preheater 5. When the feedwater temperature rises excessively, the bypass damper 312 is opened and the inlet damper 52 is provided. Should be closed.

FIGS. 3b and 3c show an example of the bypass device 35 for the boiler 10 with feedwater preheater, and FIG. 3b shows that the boiler 10 is bypassed by a bypass duct 351 and a bypass damper 352 installed therein. FIG. 3c shows an example in which only the boiler feed water preheater 6 is bypassed by the bypass duct 353 and the bypass damper 354.
When the feed water temperature rises excessively, it is desirable to open the bypass damper 352 and close the ventilator inlet damper 101, or open the bypass damper 354 provided in the bypass duct 353 of the boiler-provided feed water preheater 6. .

Effects of the Invention As described above, according to the present invention, the following effects can be achieved.

(a) The amount of steam mixed into the turbine can be suppressed below the allowable limit of the turbine by monitoring, comparing and suppressing the allowable amount of mixed air according to the turbine operating method and turbine load and the feedwater temperature control signal. Therefore, safe operation of the turbine can be secured.

(b) At the same time, the set temperature of the feed water temperature controller is changed to the upper limit temperature of the boiler, and the bypass device of the feed water preheater is activated first to prevent the release of hot water to the condenser. Since it can be suppressed to a minimum, waste heat that has been collected is released to the condenser.

(c) If a temperature detector is installed in the water supply pipe and the supply water temperature rises excessively, by operating the bypass device of the feedwater preheater attached to the boiler, the recovery of waste heat can be suppressed. It is possible to prevent wasteful discharge to the condenser.

(d) By following the above steps, if the mixture amount of the turbine is limited, it is possible to limit the mixture while securing the main steam to the turbine. Since no sudden discharge of hot water occurs, it is not necessary to keep the installed capacity of the condensate system at an excessive capacity that is suitable for hot water discharge.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram of a waste heat recovery power generation plant showing an example in which a control device according to the present invention is applied, and FIG. 2 is a diagram showing an allowable air-fuel mixture amount according to a turbine operating system and turbine load. Figures showing examples of program settings, Figures 3a, 3b and 3c show examples of bypass devices when the waste heat source is waste gas, and Figure 4 is a system diagram of a conventional waste heat recovery power plant. is there. 1 ... Condenser, 2 ... Condensate pump, 3 ... Mixing flusher, 4 ... Water supply pump, 5 ... Water supply preheater, 6 ... Boiler attached water preheater, 7, 8 ... Water supply distribution Valve, 9 ... Temperature difference controller, 10 ... Boiler with water supply preheater, 11 ... Boiler, 12,13 ... Water supply control valve, 14 ... Main steam pipe, 1
5 ... Control valve, 16 ... Turbine, 17 ... Main water supply pipe,
18 ... Water temperature controller, 19 ... Water temperature control valve, 2
0 ... Mixing stop valve, 21 ... Hot water relief valve, 22 ... Main steam pressure controller, 23 ... Generator, 24 ... Generator output meter,
25: normal operation program setter, 26: independent speed control operation program setter, 27: individual operation detector,
28 …… signal switcher, 29 …… low signal selector, 30 ……
Signal switcher, 31 ... Bypass device for water supply preheater, 32 ...
... Temperature setting device, 33 ... Temperature detector, 34 ... Override relay, 35 ... Bypass device.

Claims (1)

[Claims] Claim: What is claimed is: 1. A program setter for calculating and setting an allowable air-fuel mixture signal according to a turbine operating system and a turbine load, and comparing the allowable air-fuel mixture signal with a feed water temperature control signal, the amount of steam to the turbine. Device to control the temperature below the allowable limit, a bypass device installed in the feed water preheater to suppress the amount of heat recovery against excessive rise in the feed water temperature, and a bypass device installed in the boiler feed water preheater to prevent excessive rise in the feed water temperature. And a bypass device for suppressing the amount of heat recovery.