JPS61280387A - Water level control of condenser for combined plant - Google Patents

Abstract

PURPOSE:To lengthen the life of plant equipments and to operate the condenser safely by a method wherein inflow of makeup water from a makeup water supplying device, installed at the outside of the condenser, into the condenser is prevented in order to prevent the temporary increase of concentration of oxygen dissolved in condensed water. CONSTITUTION:Upon starting the combined plant, condensed water in the condenser 50, which contains oxygen sufficiently, is circulated to the condenser 50 through a condensed water re-circulating pipeline 57, equipped with a condensed water pump 71, a condensed water pipe 72, gland steam condenser 73 and a condensed water re- circulating valve 56, while deaerating steam is introduced into the condenser from an auxiliary steam supplying source 80 through an auxiliary steam pipeline 82 and a regulating valve 81 whereby oxygen, dissolved in the condensed water, is reduced. In this case, the set value of water level in the condenser is set by an interlock so as to be higher than the same at normal operation, whereby temporary water level rise, accompanied by the introduction of deaerating steam into the condenser, is permitted, discharge of condensed water into a makeup water tank 60 through a spillover pipeline 65 is prevented and the temporary increase of concentration of oxygen dissolved in the condensed water may be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for controlling the water level of a condenser during startup of a combined power generation plant that is not equipped with a deaerator.

In the present invention, a combined power generation plant includes a gas turbine, a means for recovering exhaust heat of the gas turbine to generate steam, a steam turbine driven by the steam, and a steam turbine for recovering steam discharged from the steam turbine. This refers to power plant equipment that is equipped with a condenser that produces steam, and a generator that is driven by the steam turbine described above.

[Background of the invention]

FIG. 5 shows an example of a schematic system diagram including a condensate degassing system of a combined plant in which a deaerator is not installed. The condensate degassing method using a condenser at the time of plant start-up according to the prior art is as described in Japanese Patent Application Laid-Open No. 59-3106, in which the oxygen stored in the condenser 50 shown in FIG. (approximately 7000 p p b ) is sent to the condenser 50 through a condensate recirculation pipe 57 equipped with a condensate pump 71 , a condensate pipe 72 , a GRACON 73 , and a condensate recirculation valve 56 . At the same time, degassing steam is supplied to the condenser 50 from an auxiliary steam source 80 (for example, an auxiliary steam header) installed outside the condenser 50 through an auxiliary steam piping 82 equipped with a steam regulating valve 81. A method of reducing dissolved oxygen in the condensate stored in the condenser is adopted.

However, during the period of condensate recirculation operation (approximately 1 hour) accompanied by the introduction of auxiliary steam, the set value of the water level in the condenser is not particularly changed, and the water level control method during normal operation is used. The amount of auxiliary steam introduced from outside to maintain the same water level as before (approximately 5 m3/hour x 1 hour = approximately 5 ma)
The increase in the water level will be discharged to the make-up water tank 60 installed outside the condenser 50 through a pipe 65 equipped with a spillover valve 64 shown in FIG.

FIG. 7 is a chart showing changes in the oxygen concentration A in condensate and the condensate water level B in the condenser when starting a combined power generation plant without a deaerator using the above-mentioned known technique.

When condensate recirculation is started at time t□, oxygen concentration curve A
begins to fall.

When degassing steam is introduced at time t2, the condensate water level in the condenser tends to rise, so water (5 m") corresponding to C shown with parallel hatching is discharged and Keep the water level curve B almost at the set position.

At time t4, when the amount of dissolved oxygen in the condensate has fallen below the specified value (approximately 10 ppb), it is assumed that degassing has been completed, and water is passed to the exhaust heat recovery boiler 10, and then at time t, the gas turbine 20 is 5).

After the gas turbine 20 is started, the drum blow 11 is carried out for the purpose of purifying the drum water from the drum 12 of the exhaust heat recovery boiler 10.
However, the amount of blowing is approximately 5 m3 per startup, and system water will be discharged outside the plant system, so make-up water will be supplied from outside to the condenser 50. It is necessary to supply 5ma. At this time, the condenser 50
A make-up water tank pipe 62 equipped with a make-up water pump 63 and a make-up water adjustment valve 61 extends from a make-up water tank 60 installed outside of the
, the amount corresponding to C′ shown with parallel hatching (
If the make-up water tank 60 is a tank that is open to the atmosphere, the make-up water in it will contain approximately 7000 p p b of dissolved oxygen, and at this point. , steam has not yet been introduced into the steam turbine 40, and the deaeration effect of the make-up water (at the time of introduction of the condenser) due to the steam turbine exhaust heat cannot be expected to be nearly as effective.For this reason, the condensate water The dissolved oxygen concentration curve A begins to increase from time 1 and reaches about 3000 p p b at time t6. This can lead to undesirable effects on lifespan.

Here, the make-up water tank 6 installed outside the condenser 50
Even if the tank has a floating roof type or neoprene type that prevents atmospheric oxygen from dissolving into the tank or water stored therein, the dissolved oxygen concentration in the make-up water is around 300 ppb, and in this case, the concentration of dissolved oxygen in the condensate water The dissolved oxygen concentration is about 1'20pp
b, but the concentration is approximately 17 times higher than the limit value of 7 ppb during normal operation, and although it is temporary, it shows that the general operation pattern of combined plants is often starting and stopping operations every day. Thinking about it, some kind of countermeasure was necessary.

[Purpose of the invention]

An object of the present invention is to provide a combined plant in which a deaerator is not installed and condensate is degassed in a condenser, and when the water level in the condenser fluctuates at the time of plant startup. By preventing a temporary increase in dissolved oxygen concentration in condensate water due to the introduction of make-up water, we aim to extend the lifespan of equipment that makes up a combined plant and provide a control method that enables safe plant operation. That is.

[Summary of the invention]

In order to achieve the above object, the control method of the present invention improves the water level control method of the condenser for a certain period of time during the start-up process of a combined plant. It is characterized by preventing makeup water (high oxygen concentration) from flowing into the condenser from the supply device.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described using FIG. 5, FIG. 1, and FIG. 2.

When starting up a combined plant, the condensate containing sufficient oxygen in the condenser 50 in FIG.
, condensate pipe 72, Guracon 73. The deaeration steam is circulated to the condenser 50 via a condensate recirculation pipe 57 equipped with a condensate recirculation valve 56, and is also supplied from an auxiliary steam supply source 80 via an auxiliary steam pipe 82 and a regulating valve 81. By introducing (about 5 m3) into the condenser, dissolved oxygen in the condensate will be reduced.

At this time, as shown in Figure 1, an interlock (for example, a signal for introducing deaeration steam into the condenser) causes the water level setting value of the condenser to be set higher than the water level (NWL) during normal operation (for example, By setting NWL + 200mm),
To allow a temporary rise in water level (approximately 200 countries) due to the introduction of deaeration steam into the condenser, spillover piping 65
This prevents condensate from being discharged into the make-up water tank 60 via the

FIG. 2 is a chart showing changes in the oxygen concentration curve A' in condensate and the condensate water level B' in the condenser in an embodiment of the present invention.

When condensate recirculation is started at time t1, the oxygen concentration curve A'
begins to fall.

When introducing the deaeration steam at time t2, the water level set value D' in the condenser is changed to NWL+200 nm.

Therefore, the condensate water level curve B' starts to rise from time t2.

At time t3, the oxygen concentration becomes 10 Pppb. At this point, the deaeration is completed and the gas turbine is started at time t,'.

After the gas turbine is started, drum blowing 11 is carried out from the exhaust heat recovery boiler 10, and the amount of this blowing is approximately 5 m'' per start-up as shown in Fig. 1. It is almost equal to the amount introduced.

At time t, the condensate water level setting B' is returned to NWL.

The water level in the condenser can be increased without changing the water level setting, for example, by introducing deaeration steam into the condenser and forcibly closing the spillover control valve 64 shown in FIG. The goal is to raise the

Furthermore, after starting the gas turbine 20, the exhaust heat recovery boiler 1
When drum blowing 11 is performed from 0 (time point t), by supplying excess condensate stored in the condenser to the waste heat recovery boiler using the above method, make-up water from outside the condenser is removed. Introduction can be prevented.

Here, after drum blowing, the steam from the exhaust heat recovery boiler will be vented to the steam turbine, but the spillover regulating valve that was forcibly closed above will be forced to close, for example, by the steam turbine ventilation signal. By releasing this, after time t7, the water level B' in the condenser will be operated while being controlled at the water level during normal operation.

Furthermore, the secondary effects of applying the present invention to a combined plant where degassing is not installed will be described below.

FIG. 4 shows the changes in pressure in various parts of the condenser due to the introduction of auxiliary steam from outside the condenser at the time of plant startup. Hot well outlet condensate pressure (■
) tends to maintain a somewhat high pressure due to the difference in static water head between the operating water level in the condenser and the hot well outlet.

Here, as the condensate temperature in the hot well increases due to the introduction of auxiliary steam for degassing, the condensate pressure in the hot well becomes (■)
However, in the conventional condenser water level control method (i.e., maintaining the same water level as during normal operation even at startup), the water level in the condenser Because the hydrostatic head difference between the hot well outlet and the hot well outlet is small, the condensate pressure may be higher than the hot well outlet condensate pressure, as shown in (■) in Figure 4, and in this case, the hot well outlet When the condensate flashed and air bubbles flowed into the condensate pump, there was a risk of cavitation in the condensate pump.

To solve the above problems, the present invention temporarily raises the water level in the condenser at startup, increasing the difference in static water head between the water level in the condenser and the hot well outlet, thereby increasing the hot well outlet pressure. By always maintaining the condensate pressure higher than the condensate pressure inside the hot well and preventing flash phenomena at the outlet of the hot well, it can have a significant effect on safe plant operation.

As a further different embodiment, in order to prevent makeup water containing a large amount of dissolved oxygen from being introduced into the condenser from the makeup water supply device installed outside the condenser at the time of plant startup, the first The temporary dissolved oxygen concentration in the condensate at startup can also be controlled by a control method that forcibly closes the make-up water regulating valve 61 installed in the middle of the piping 62 that connects the make-up water device 60 and the condenser 50 in the figure. It is possible to prevent an increase in

However, in this example, the water level in the condenser is expected to decrease when drum blowing from the waste heat recovery boiler is performed, so the flash phenomenon at the outlet of the condenser hot well is prevented. For the purpose of
If the water level drops to below, it is necessary to take measures such as releasing the forcible closure of the make-up water isolation valve.

Furthermore, if this embodiment is adopted, the forcible closure of the make-up water regulating valve will be released by a signal such as steam turbine ventilation, but at that time, the condenser water level is lower than the water level during normal operation. Therefore, there is a concern that a large amount of make-up water will be supplied to the condenser when the make-up water adjustment valve is forcibly closed. For this reason, it is necessary to control the opening operation of the make-up water regulating valve by using a ramp function generator or the like so that a large amount of make-up water is not supplied to the condenser at once.

〔Effect of the invention〕

Blowing As described in detail, when the method of the present invention is applied to a combined power generation plant that does not have a deaerator separate from the condenser, the condenser is affected by fluctuations in the water level in the condenser at the time of plant startup. By preventing the temporary increase in dissolved oxygen concentration in condensate water caused by the introduction of make-up water, this is an excellent practical solution that extends the lifespan of the equipment that makes up the combined plant and enables safe plant operation. be effective.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a water level control method in an embodiment of the present invention, Fig. 2 is a chart for explaining the effects of the above embodiment, and Fig. 3 is a diagram for explaining the effects of an embodiment different from the above. Figure 4 is a diagram for explaining the secondary effects of the method of the present invention. Fig. 5 is a system diagram of a combined power generation plant to which the control method according to the present invention is applied, Fig. 6 is an explanatory diagram of the conventional control method, and Fig. 7 is a diagram for explaining problems in the conventional technology. be. 10...Exhaust heat recovery boiler, 11...Drum blow. 12...Drum, 20...Gas turbine, 30...
- Generator, 40... Steam turbine, 50... Condenser, 51... Condenser water level control device, 56... Condensate recirculation valve, 57... Condensate recirculation piping, 60... Replenishment tank, 61... Makeup water adjustment valve, 62... Makeup water piping,
63... Makeup water pump, 64... Spillover adjustment valve, 65... Spillover piping, 71... Condensate pump, 72... Condensate pipe, 73... Gracon, 74
... Water supply stop valve, 75 ... Water supply adjustment valve, 80 ... Auxiliary steam source, 81 ... Auxiliary steam adjustment valve, 82 ... Auxiliary steam piping.

Claims (1)

[Claims] 1. A gas turbine, a means for recovering exhaust heat of the gas turbine to generate steam, a steam turbine driven by the steam, and a steam turbine for generating steam discharged from the steam turbine. A method comprising a condenser for recovery and a generator driven by the steam turbine, and a deaerator is not provided in the water supply system of the steam generating means, and the condenser also serves as a deaerator. In a combined power generation plant configured as shown in FIG. A method for controlling a condenser water level in a combined plant, the method comprising: adjusting the water level of condensate in a combined plant. 2. The means for adjusting the make-up water so that it does not flow into the condenser is to change the setting value of the automatic water level control device installed in the condenser during a certain period of time during the plant start-up process. A method for controlling a condenser water level in a combined plant according to claim 1, characterized in that the method is carried out by: 3. The means for controlling the make-up water so that it does not flow into the condenser is to provide a valve in the piping connecting the condenser and the make-up water supply device, and to prevent the make-up water from flowing into the condenser during a certain period of time during the plant start-up process. 2. A condenser water level control method for a combined plant according to claim 1, wherein said method is carried out by closing said valve. 4. The means for adjusting the make-up water so that it does not flow into the condenser includes a condensate pipe that supplies condensate in the condenser to a boiler for exhaust heat recovery, and a condensate storage tank. The combined plant restoration according to claim 1 is carried out by providing a valve in the middle of the connected piping and closing the valve during a certain period during the plant startup process. Water device water level control method.