JPH04106394A - Condenser for steam turbine - Google Patents

Abstract

PURPOSE:To provide a condensed water descending pipe with the function of a pressure equalizing pipe and reduce the number of isolating valves by a method wherein the condensed water descending pipe, having an outlet opening above the water level of a hot well is provided in order to form two flow passages of non-condensable gas or deaerating excessive steam, ascending toward a condensing part through the central part of the pipe. CONSTITUTION:The flowing condition of a condensed water descending pipe 6 is different remarkably depending on the operating condition of a condenser and principal flow upon starting is ascending flow of excessive deaerating steam, introduced by a deaerating heater 9 and flowing from a hot well 4 into a water condensing part 3, while the flow upon normal operation is the descending flow of condensed water of the exhaust steam of a turbine, which flows from the water condensing part 3 toward the hot well 4. The superposing condition of these ascending flow and descending flow under the maximum flow rate conditions of respective flows can not be generated when a condenser is operated. The size of the condensed water descending pipe 6 is determined considering the flow conditions of both of the flows while the outlet port thereof is provided above the water level of the hot well 4 considering the ascending flow of excessive steam upon starting the operation of the condenser. The functions of a condensed water descending pipe and a pressure equalizing pipe can be realized by only the condensed water descending pipe 6 and the reduction of the number of isolating valves becomes possible.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a condenser for a steam turbine, and in particular, to a method that isolates a hot well when the plant is stopped, and deaerates condensate and supplies water when the plant is started. The present invention relates to a steam turbine condenser suitable for a condenser structure.

[Conventional technology]

A conventional steam turbine condenser is disclosed in Japanese Patent Application Laid-open No. 60-5719.
As stated in Publication No. 1, when the plant is started up, the condensate stored in the hot well of the condenser is recirculated through the condenser recirculation piping connected to the condenser outlet, and at the same time It is necessary to carry out the operation while heating the condensate using a heating steam injection pipe, and in addition to requiring heated steam for degassing upon startup, this structure requires a long startup time due to the degassing operation.

Furthermore, as described in Japanese Patent Application Laid-Open No. 59-52192, a partition wall is provided between a tube nest for condensing steam and a hot well for storing condensed water, and the space is separated by a water seal while the condensate is returned to the hot well. In addition to guiding water, a pressure equalizing pipe with an isolation valve is installed between the tube nest and the real well to prevent air from stagnation in the space below the bulkhead, and when the plant is stopped, a water seal and isolation in the pressure equalizing pipe are installed. There is a method that uses a valve to prevent direct contact between the hot well condensate and the atmosphere, thereby reducing the dissolution of oxygen into the condensate water, but with this method, when the plant is stopped, the hot well pressure is reduced to atmospheric pressure. Therefore, it is impossible to maintain the amount of dissolved oxygen at a level that allows startup.

Furthermore, since each of the above conventional examples has advantages and disadvantages, the sealing effect can be further enhanced by combining them and installing a condensate downcomer pipe equipped with an isolation valve in the same way as the pressure equalization pipe in place of the water seal described above. A method is planned.

[Problem to be solved by the invention]

In a condenser designed by combining a hot well isolation method and a condensate degassing structure as in the above conventional technology, condensate condensed in a tube nest is transferred to a downcomer pipe and a pressure equalizing pipe that lead to a hot well. Each is equipped with an isolation valve, and the hot well is isolated by closing this isolation valve, but in this implementation, the diameter of the isolation valve becomes considerably large, and moreover, the frequency of opening and closing of the valve is usually very high. Because of the large number of valves, it is difficult to ensure a perfect seal due to deterioration of the valves over time, and the amount of air leaking from the valves increases in proportion to the number of valves. is desired.

In order to reduce the amount of air leaking from the hot well isolation when the plant is stopped, the present invention adopts a structure in which the condensate downcomer pipe also has the function of a pressure equalization pipe, thereby reducing the number of isolation valves. An object of the present invention is to provide a steam turbine condenser that can send deaerated feed water to a steam generator.

[Means to solve the problem]

In order to achieve the above object, the steam turbine condenser of the present invention allows the condensate in the condensate part to fall toward the hot well through the pipe wall of the condensate downcomer pipe having an isolation valve, and to prevent the condensate from falling in the central part of the pipe. A condensate downcomer pipe having an outlet opening above the water surface of the hot well is installed to form two flows in which condensed gas or surplus steam for deaeration rises toward the condensate section.

Further, a rectifying device (straightening tube) is installed in the condensate downcomer pipe so that the two fluids face each other and form a smooth flow.

[For production]

The condensate downcomer pipe of the steam turbine condenser has a cylindrical shape with an opening in the partition between the condensate part and the hot well, and the outlet is vertically located above the water surface of the hot well. Therefore, condensate from the condensate section flows from the outer periphery of the condensate downcomer pipe and flows down along the wall surface, and the condensate flowing down becomes thicker and flows as the flow rate increases, but the flow rate at the center of the pipe is very small, so by appropriately selecting the diameter of the condensate downcomer pipe for the condensate flow rate, condensate flows through the pipe wall and gases such as non-condensable gas or excess steam face each other in the central part. Furthermore, since the outlet of the condensate downcomer pipe is set above the water surface of the hot well, it can also function as a pressure equalizing pipe, which was conventionally provided separately.

In addition, by installing a rectifying device such as a rectifier at the inlet of the condensate downcomer pipe to force the flow of condensate only to the wall surface, the effect of this restriction can be applied to the lower part of the condensate downcomer pipe. Since the flow of the two fluids becomes smoother, it becomes possible to reduce the diameter of the condensate downcomer pipe. Furthermore, by providing guide vanes around the straightening tube between the wall surface of the condensate downcomer pipe and the straightening tube, smoother flow can be achieved.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 is a sectional view showing an embodiment of a steam turbine condenser according to the present invention. In FIG. 1, a condenser body 1 includes a condensing part 3 having a tube nest 2 for condensing steam from a turbine, a hot well 4 for storing condensed water, and a condensing part 3 and a hot well 4. A horizontal partition wall 5 is provided for partitioning. Further, the bulkhead 5 is provided with a condensate downpipe 6 having an isolation valve for causing condensate to flow down to the hot well 4, and the outlet of the condensate downcomer 6 is set above the water surface of the hot well 4. ing. The hot well 4 also has a condensate recirculation device 7 directly below the partition wall 5, a zigzag baffle 8 for retaining condensate within the hot well 4, and a condensate outlet of the hot well 4 formed by the zigzag baffle 8. A heating device 9 for degassing by steam injection is installed below the water surface at the entrance of the connected passageway at the end.

FIG. 2 is a partially detailed view of the condensate downcomer pipe 6 shown in FIG. In FIG. 2, the condensate downcomer pipe 6, which is the essential part of the present invention, is equipped with an isolation valve 10, and a rectifier tube 11 that forms a rectifier at its inlet.
is provided. Note that the same reference numerals indicate corresponding parts throughout the drawings.

FIG. 3 is an explanatory diagram showing operating procedures for each operation mode of the condenser shown in FIG. 1. In Fig. 3, the operation modes of the condenser can be roughly divided into stop operation and stop operation.

There is a start-up operation and a normal operation, and the condensate deaeration means shown in Figs. 1 and 2, the condensate recirculation device 7, the deaeration heating device 9, and the condensate precipitation during each operation. Pipe isolation valve I
A summary of the operating status of each device O and the magnitude relationship between the flow rates of condensate and non-condensable gas flowing in the condensate downcomer pipe 6 at that time is shown. The details are shown below.

During stop operation, the main purpose of the present invention is to provide an optimal condenser for this operation, but the condenser that is the object of the present invention is one that is frequently started and stopped in the plant,
When the hot well 4 is stopped, it is intended to be completely isolated and maintained at the same pressure and amount of dissolved oxygen as immediately before the stop. 5 For this purpose, the reliability of the isolation structure is important. In order to completely isolate this, it is necessary to eliminate the cause of air leakage from the atmosphere side to the hot well 4, which is maintained in a high vacuum during stopped operation, and an effective means for this is to install an isolation valve etc. The aim is to reduce the number of valves used, reduce their diameters, and create a structure that further improves airtightness.

During start-up operation, there are two methods of start-up operation: hot start, which is started after a relatively short stop, and cold start, which is started after a long stop.Hot start is a start-up operation that is started after a relatively short stop, and cold start, which is started after a long stop. Normal operation for the purpose of degassing can be done in a relatively short period of time, while a cold start involves starting from a stop without isolation, which requires long degassing operations. It becomes necessary. In other words, a deaeration operation is required in either case at the time of start-up operation, and this is done by recirculating the condensate taken out from the outlet of the hot well 4 by the condensate recirculation device 7, and degassing it under the water surface of the hot well 4. Heating device! By adding steam from step 9.

The structure is such that deaeration is performed using the stirring action of condensate heating and bubbling. During start-up operation, the condensate section 3 must also be in a vacuum state, and only exhaust steam for turbine gland sealing flows into the condensate section 3 (turbine exhaust does not flow in), and the condensate downcomer pipe The flow rate of condensate flowing down 6 is extremely smaller than that during normal operation described below.

On the other hand, surplus steam introduced by the heating device 9 and used for bubbling is introduced into the condensing section 3 through the condensing downcomer pipe 6, where it becomes condensed water and is collected in the hot well 4. Therefore, the flow rate flowing upwardly from below inside the condensate downcomer pipe 6 is larger than during normal operation described below.

During normal operation, the amount of dissolved oxygen required for water supply to the steam generator can be reduced to about 7 ppb using the same operating method as a conventional condenser, so the introduction of steam by the deaeration heating device 9 is Not necessary. The turbine exhaust gas is therefore condensed by the tube nest 2.

The condensed water is led to the hot well 4 by the condensate downcomer pipe 6, and at this time the condensate flow rate is maximum. Note that the flow rate flowing upward into the condensate section 3 is mainly only air leaking into the hot well 4, and is much smaller than that during the startup operation described above.

As mentioned above, the flow condition in the condensate downcomer pipe 6 varies greatly depending on the operating conditions of the condenser, and at startup, the main flow is excess steam from the degassed steam introduced by the deaeration heating device 9. This is an upward flow from the hot well 4 toward the condensate section 3 due to the condensation of the turbine exhaust gas, and a downward flow toward the hot well 4 from the condensate section 3 due to condensation of the turbine exhaust during normal operation.

In addition, it is impossible for the upward flow and the downward flow to overlap each other under the maximum flow rate condition. Therefore, in the embodiment of the present invention, the dimensions of the condensate downcomer pipe 6 are determined in consideration of both of these flow conditions, and the outlet of the condensate downcomer pipe 6 is set at the water level of the hot well 4 in consideration of the upward flow of excess steam during startup operation. It is installed so that it is higher up. On the other hand, in the conventional example, a pressure equalizing pipe is provided as a passage separate from the condensing downcomer pipe 6 for the flow of surplus steam to the condensing part 3 during startup operation, and the dimensions of this pressure equalizing pipe are also It is almost the same as the condensate downcomer pipe 6, and of course an isolation valve is also required for when the operation is stopped. In other words, in the embodiment of the present invention, the functions of the condensate downcomer pipe and pressure equalization pipe of the conventional example can be realized only with the condensate downcomer pipe 6, and this makes it possible to reduce the number of isolation valves. , Hot Well 4 with reduced air leakage during stop motion
This can prevent the amount of dissolved oxygen in the condensate stored in the water from increasing.

Furthermore, in this embodiment, in addition to the main flow of the condensate downcomer pipe 6, which is the upward flow during start-up operation and the downward flow during normal operation, there are flows in opposite directions, so that the condensate precipitation tube 6
A rectifying device (straightening tube) 11 is provided at the inlet of the condensate downcomer pipe 6 to smooth these two flows within the condensate downcomer pipe 6. This rectifying device 11 directs condensate flowing downward from the condensate section 3 (indicated by the broken arrow in FIG. 2) to the condensate downcomer pipe 6 as much as possible.
This system allows the flow of gaseous fluids such as leakage air or surplus air to flow at a high density on the wall surface of the 5, and in the center of the 5, flows as an upward flow (solid arrow in Figure 2) due to buoyancy. Like the condensate downcomer pipe 6, it has a cylindrical shape and is arranged concentrically with the condensate downcomer pipe 6.

FIG. 4 is a partially detailed view of a condensing downcomer pipe 6 showing another embodiment of the steam turbine condenser according to the present invention. Further, FIG. 5 is a view taken along the line A--A in FIG. 4.

4 and 5, a rectifier bag M (
A guide vane 12 is installed around the rectifier tube 11 between the rectifier tube) 11 and the condensate downcomer pipe 6, and this guide vane 12 protects against radiation from the center of the rectifier tube 11 as shown in FIG. It is installed so that it has an inclination of angle θ. As a result, the condensate is forcibly guided toward the wall of the condensate downcomer pipe 6 (solid arrow), and the centrifugal force causes the condensate to flow at a higher density on the wall. Since it extends to the lower part of the downcomer tube 6, the effect of the rectifier tube 11 can be further enhanced.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

By setting the outlet of the condensate downcomer pipe of the condenser above the water surface of the hot well, it is possible to introduce condensate into the hot well during normal operation and to condense excess degassed steam during startup operation. It is possible to have the two functions of introducing
Since the conventional pressure equalization pipe is not required, hot well isolation during shutdown operation becomes more reliable, and therefore the amount of dissolved oxygen in the condensate can be maintained at a lower level, thereby shortening the start-up time of the plant.

Further, by providing a rectifier tube in the condensate downcomer pipe, the flow in the condensate downcomer pipe can be made smooth, and the size can be reduced.

Furthermore, by providing guide vanes around the straightening tube, the flow within the condensate downcomer pipe can be made smoother, allowing stable operation of the condenser.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a steam turbine condenser according to the present invention, FIG. 2 is a partial detailed view of the condensing downcomer pipe shown in FIG. 1, and FIG. 3 is a diagram showing each operation mode shown in FIG. Driving instructions diagram,
FIG. 4 is a partially detailed view of a condensing downcomer pipe showing another embodiment of the steam turbine condenser according to the present invention, and FIG.
It is a view from arrow A. 1... Condenser body, 2... Tube nest, 3... Condensate part,
4... Hot well, 5... Bulkhead, 6... Condensate downcomer pipe, 7... Condensate recirculation device, 8... Baffle, 9...
... Heating device for degassing, 10... Isolation valve, 11... Rectifier tube, 12... Guide vane. Representative Patent Attorney Tadashi Akimoto Actual Figure 5-7 Ichijiku Figure 10-Isolation Well 11...-Fleet Figure 12--fF#1 Hafukuro

Claims (1)

[Claims] 1. A partition is provided between a condensate section having a tube nest that condenses the exhaust gas of the turbine and a hot well that stores condensate from the condensate section, and a partition wall is provided between the condensate section and the hot well. A steam turbine condenser equipped with a condensate downcomer having an isolation valve for guiding condensate to a hot well, characterized in that the outlet of the condensate downcomer is located above the water surface of the hot well. Condenser for turbine. 2. The condenser for a steam turbine according to claim 1, further comprising a rectifier for causing different types of fluids to flow in opposite directions in the condensing downcomer pipe. 3. The condenser for a steam turbine according to claim 2, wherein guide vanes are provided between the inner wall of the condensate downcomer pipe and a rectifier tube forming a rectifier. 4. The steam turbine according to claim 1, further comprising a degassing means comprising a steam heating device using steam injection provided below the water surface at the inlet of the connected passage whose end is the condensate outlet of the hot well. condenser.