JPS6069486A - Cooling method of condensate - Google Patents

Abstract

PURPOSE:To prevent the corrosion in the system as well as to reduce the power consumption in cooling the condensate during a suspension period of operation of a steam power generating plant etc. by an arrangement in which a water circulating pump is stopped, and a separate water circulating pump for suspension and a sea water heat exchanger for suspension period are operated instead. CONSTITUTION:During the suspension period of operation, a water circulating pump 16 is stopped, and a separate circulating pump for suspension 19 is started to cause the cooling water to flow from a circulating water pipe for suspension 18 to a sea water heat exchanger for suspension period 20 to cool down the condensate that is heated by an ejector steam condenser 9 and a gland steam condenser 11 and flows into a condensate minimum flow line 12 for cooling. By this arrangement, the amount of the cooling water can be reduced, and the cooling can be achieved by a less power.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cooling condensate during shutdown of all plants having steam condensers.

As shown in FIG. 1, as a conventional cooling device used in a method for cooling condensate during shutdown of this type of plant, a gland seal steam pipe 1 is connected to a turbine gland 3 of a steam turbine 2, and a The turbine gland 3 communicates with a gland steam condenser 11 via a gland leakage steam pipe 4 to perform primary cooling of the steam turbine 2, and the steam turbine 2 is connected to a circulating water intake groove (or pipe). ) 15 and a circulating water discharge pipe 17, a condensate pipe 8 is drawn out from a botwell 6 of the condenser 5, and a condensate pump 7, Ejector steam condenser 9 and ground steam condenser]
1 is provided, and a ground and ejector steam condensate line 13 is led back to the hot well 6 from the ejector steam condenser 9 and the gland steam condenser 11, and a condensate line 13 is routed from the downstream portion of the gland steam condenser 11 of the condensate pipe 8. There is one in which the water minimum flow line 12 is drawn back to the condenser 5.

In the figure, 10 is an ejector driving steam pipe communicating with the ejector steam condenser 9, and 14 is a non-condensable gas extraction pipe communicating from the condenser 5 with the ejector steam condenser 9. The condenser 5 is provided with a circulating water intake groove (or pipe) 15 for circulating seawater and a circulating water discharge pipe 17, and the circulating water intake pipe 15 is provided with a circulating water pump 16.

Note that in a plant that uses a vacuum pump instead of an ejector to create a vacuum in the condenser 5, the ejector steam condenser 9 and the ejector drive steam pipe 10 are removed, and the noncondensable gas extraction pipe 14 is not shown. Not connected to a vacuum pump.

Conventionally, when a thermal power plant is out of service, the maintenance state of the condensate system can be roughly divided into the following two methods.

■ Break the vacuum of the condenser and release it to the atmosphere.

■ Maintain a vacuum in the condenser to prevent air from entering the system.

In the case of breaking the vacuum as in the former case, all equipment is stopped and maintenance power costs are saved, but the condenser and turbine are filled with air and a significant portion of the system is Since it is wet with water, considerable rusting is inevitable.

On the other hand, in the case of maintaining a vacuum as in the latter case, the steam is sent to the turbine gland, and the slightly reduced air is collected in the air + ring zone (not shown) in the condensate, where it becomes non-condensable gas. It is discharged from the extraction tube 14 by an ejector or a vacuum pump, and the partial pressure of air in the system, that is, the partial pressure of oxygen, is kept low and rusting is prevented.

The following cooling method is generally used to prevent rust from forming and to prevent the temperature in the system from rising too high due to gland seal steam.

The condensate is circulated through a system of a real well 6, a condensate pump 7, a condensate minimum flow line 12, and a condenser 5, and the ejector drive steam and gland leakage steam are cooled and condensed in the ejector steam condenser 9 and the brand steam condenser v11, respectively. urge The condensate whose temperature has increased due to this heat exchange is sent from the condensate minimum low line 12 to the condenser 5, where the circulating water, that is, the cooling seawater sent by the circulating water pump 16 and the circulating water intake pipe 15. It is cooled by indirect heat exchange with

Through the above operations, the inside of the condensate system is maintained at a temperature slightly higher than seawater, the pressure inside the vessel is approximately the saturated water vapor pressure at that temperature, the oxygen partial pressure is maintained low, and corrosion of equipment is prevented.

Note that during the above operation, the condensate pump 7 and the circulating water pump 1
Since each of the 6 vehicles is operated, a considerable amount of power is required.

However, with the first method mentioned above, which destroys the vacuum in the condenser and opens it to the atmosphere, there is considerable rust formation within the system, which results in frequent shutdowns, and in thermal power plants, every time the plant is started up. Since iron and copper eclipse products are brought into the boiler from the water supply system, the water supply system and boiler are heavily contaminated with rust, and if disposed of incorrectly, they accumulate on the inner surface of the boiler evaporation tube and cause evaporation due to scale. The pipes become overheated and sometimes blowouts generate electricity.

To prevent this, we inspect the evaporator pipes more frequently than in plants that have fewer starts and stops, monitor the degree of contamination, and perform early chemical cleaning of the boiler to remove corrosion products from iron and copper that have adhered or accumulated. However, the expense of this chemical cleaning is quite large, so the increased frequency of chemical cleaning compared to the operating time is a loss.

In order to reduce the amount of dirt brought into the boiler, a so-called talin-up operation is carried out in which rust and other dirt in the condensate system and water supply system is flushed out of the line each time the boiler is started, but the startup operation takes a long time. For example, if you want to bring the power plant to full load at 8 a.m., there is a drawback that startup may not start until midnight.

On the other hand, in the case of the above-mentioned second method, which is a shutdown method that maintains the vacuum level of the condenser, there is little rust in the system (and the time required for startup is short, but the condensate pump 7 and circulating water pump 1
6 of power is required, and the power consumption of the circulating water pump, which is particularly large, is extremely large.

As a result, power generation plants, which are now often shut down at night and on holidays, consume a considerable amount of electricity while they are not producing electricity, resulting in a large increase in costs throughout the year.

When performing the cooling operation described above, the circulating water pump 16 is too large for the required cooling amount.

The present invention was made in view of the problems of the prior art and to solve the problems.The present invention was made in order to solve the problems of the prior art. The purpose is to provide a condensate cooling method that can suppress the occurrence of corrosion in the system by keeping air leakage low, and can significantly reduce the power required to maintain vacuum compared to conventional methods. shall be.

In order to achieve this object, the condensate cooling method of the present invention is applicable to a thermal power generation plant having a steam turbine and a steam condenser, when the plant is shut down without causing a vacuum breakdown of the condenser. By stopping the circulating water pump and using a separately installed small circulating water pump and seawater heat exchanger when not in use, you can eliminate ground leakage steam, ejector drive steam, etc. with a smaller circulating water flow rate than when using the circulating water pump. It is characterized by performing necessary cooling while the plant is not in operation.

The details of the invention will now be described with reference to an illustrative embodiment. Note that the same reference numerals are used for the same components as those of the cooling device (FIG. 1) used in the conventional condensate cooling method.

Figure 2 shows a thermal power plant equipped with a steam turbine and a steam condenser that maintains the vacuum of the condenser 5 during plant shutdown and uses condensate cooling without introducing air into the condensate system. In plants such as power generation plants, a circulating water pipe 18 for cooling during downtime is installed separately from the circulating water pipe for cooling during normal operation, and this circulating water pipe 18 for cooling during downtime is equipped with a circulating water pump during normal operation. A circulating water pump 19 at rest, which is smaller than 16, and a seawater heat exchanger 20 at rest, are provided, and the seawater heat exchanger 20 at rest is located in the middle of the condensate minimum flow line 12 to cool the condensate. The condensate minimum flow line 12 is detoured with a seawater heat exchanger bypass line 21 for normal operation [16] in which the Nrj water heat exchanger 20 is not used during shutdown. A condensate cooling system is described.

Reference numerals 1 to 17 in FIG. 2 are the same as those of the conventional cooling device shown in FIG. 1, but the parts starting from 18 are different. That is, in FIG. 2, the circulating water pipe 18 at rest is pulled out from an appropriate position of the circulating water intake pipe 15 and connected to the circulating water discharge pipe 17. A small circulating water pump 19 at rest and a heat exchanger 20 at rest are provided, and the heat exchanger 20 cools the condensate in the minimum condensate flow line 12. A seawater heat exchanger bypass line 21 is connected in a roundabout manner to the seawater heat exchanger bypass line 21 for normal operation when the seawater heat exchanger 20 is not used when the seawater heat exchanger 20 is not used.

Note that the water intake of the circulation pipe 18 during suspension may be on the downstream side or the upstream side of the circulation water pump 16, or may be taken directly from the sea, river, lake, etc. In addition, the outlet for circulating water when not in use may be connected to the circulating water discharge pipe 17 (or to the appropriate sea, river, or lake in the pond). However, generally, the circulating water pipe 18 is kept as short as possible when not in use. ka (coined)

Next, a cooling method using the cooling device configured as described above will be explained.

When maintaining the vacuum in the condenser 5, sealing steam is sent to the gland 3 of the turbine 2, and the small amount of air that leaks is collected in the air ring zone shown in the figure in the condenser 5, so that it is not condensed. The gas is discharged from the extraction tube 14 by an ejector or a vacuum pump, and the air partial pressure, that is, the oxygen partial pressure, in the system is kept low.

Furthermore, the condensate is circulated through a system of the Hontowell 6, the condensate pump 7, the condensate minimum flow line 12, and the condenser 5, and the condensate is circulated through the system of the Esekku steam condenser 9 and the grand steam condenser]
1, the ejector driving steam and the gland leaking steam are cooled and condensed. In this respect, the operation is the same as that of the conventional device shown in Fig. 1.
The system is kept sufficiently empty by using steam and an ejector or vacuum pump, and by suppressing the 3"1.6X cleaning of the system by these steams by cooling.

In the method of suppressing the temperature rise in the system in this case, the present invention uses a circulating water pump 16 as shown in FIG.
9 is started, cooling water is passed through the rest period circulating water pipe 18 to the rest seawater heat exchanger 20, and is heated by the ejector steam condenser v9 and the grand steam condenser 11 and condensed water. Minimum flow line 12
The purpose of cooling is achieved with a small amount of cooling water by cooling the condensate flowing through.

As described above, in the method for cooling condensate during plant shutdown according to the present invention, the vacuum of the condenser is maintained during shutdown, and the condensate is cooled without introducing air into the condensate system. In thermal power generation plants and other plants equipped with steam turbines and steam condensers that use The system is configured so that the flow rate of circulating water used for necessary cooling such as condensate water during periods of rest is sent to the circulation path at a flow rate lower than that during normal operation and with less power. The power of the circulating water pump can be much smaller than the power of the circulating water pump during normal operation.

For example, since it can be used as the power source for ``/+oo~]/SOO, the annual cost savings are extremely large for power plants that frequently start and stop.By the way, 350
The amount of circulating water in MW class power generation is approximately 1.05 T/H, and when only one circulating water pump is operated during normal operation, the flow rate is 2.5 to 4.5 X I O' T/II. On the other hand, the flow rate of circulating water during rest may be several hundred'1''//II. Of course, taking into account the safety factor, using a larger amount of water can be used as long as it does not significantly impair economic efficiency. This does not depart from the purpose of the present invention.

[Brief explanation of drawings]

Figure 1 is a system diagram of a condensate system of a cooling device used in a conventional method for cooling condensate during plant shutdown, and Figure 2 is a system diagram of a condensate system used in the present invention's method for cooling condensate during plant shutdown. FIG. 2 is a system diagram of a condensate system of a cooling device. 5・e condenser, 1211・condensate minimum flow line,
l 5... Circulation fffi Mizutori Zk'1ii11 (i
...Circulating water pump when connected to '+ifl', F... Circulating water discharge pipe, 18... Circulating water pipe when not working, 19... Circulating water pump when not working, 20... Seawater heat exchanger when not working, 21・・・
Seawater heat exchange bypass line.

Claims (1)

[Claims] In thermal power generation plants and other plants equipped with steam turbines and steam condensers that maintain a vacuum in the condenser when the plant is shut down and cool the condensate without introducing air into the condensate system. , Cooling required for condensate during normal operation and cooling required for condensate during stoppage are carried out through separate routes, and circulating water is used for cooling necessary for condensate during stoppage. A method for cooling condensate characterized by sending a flow rate smaller than that during normal operation to its circulation path with less power.