JPH0322522B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a combined cycle power generation plant, and particularly to a system for supplying high-temperature water to an exhaust heat recovery heat exchanger of the unit in response to demands for rapid start-up of the plant. The present invention relates to a combined cycle power generation plant capable of reducing start-up time.

[Technical background of the invention and its problems]

Combined cycle power plants have been developed to meet the recent demands on the power supply and demand side, that is, to be able to make large and rapid load adjustments, and to be able to maintain high thermal efficiency even at partial loads. In consideration of this point, gas turbines, exhaust heat recovery heat exchangers,
The output of each unit consisting of a steam turpin and a generator is kept small, and multiple units with low output are often combined into one power generation plant. The ability of this combined cycle power plant to quickly respond to changes in power demand is largely due to the ease with which the gas turbine can be started and stopped. In order to make full use of the characteristics of this gas turbine, it is important to check whether the other equipment that makes up the unit is compatible with it, and the exhaust heat recovery heat exchanger is This is the first device that becomes a problem in such cases. The exhaust heat recovery heat exchanger used here will be explained below.

That is, this type of exhaust heat recovery heat exchanger has a low pressure steam drum 1, a low pressure energy saver 2, as shown in FIG.
and a low-pressure system consisting of a low-pressure evaporator 3, and a high-pressure system consisting of a high-pressure steam drum 4, a high-pressure economizer 5, a high-pressure regular generator 6, and a high-pressure superheater 7. Guided by lineage. Generally, exhaust heat recovery heat exchangers are classified into forced circulation type and natural circulation type depending on the can water circulation method, and FIG. 4 shows an example of the forced circulation type.
The feed water coming out of the water pump 9 is heated by the low pressure economizer 2 and guided to the low pressure steam drum 1. The canned water in the low-pressure steam drum 1 is sent to the low-pressure steamer 3 via the low-pressure circulation pump 10, where it is partially evaporated, and then returned to the low-pressure steam drum 1. The two-phase flow of steam and water returned to the low-pressure steam drum 1 first enters the first stage moisture separator 11, where it is separated into steam and water, and the water becomes canned water. On the other hand, after the steam flows on the surface of the can water, it enters the second stage moisture separator 12, where the moisture is finally removed.
It passes through a low-pressure main steam official 13 and is guided to a low-pressure stage of a steam turbine (not shown). In addition, low pressure steam drum 1
A portion of the canned water is led to the transfer pump 14 and boosted in pressure, and sent to the high pressure economizer 5 where it is heated again.
Enters high pressure steam drum 4. The canned water in the high-pressure steam drum 4 is sent to the high-pressure evaporator 6 via the high-pressure circulation pump 15, where a portion is evaporated to become a two-phase flow of steam and water, which returns to the high-pressure steam drum 4. As in the case of the low-pressure steam drum 1, this two-phase flow is separated into steam and water through the first-stage moisture separator 16 and the second-stage moisture separator 17, and the steam is sent to the high-pressure superheater 7. Sent. Also, the water merges with the canned water. The steam sent to the high-pressure superheater 7 becomes superheated steam here, and is led to a high-pressure stage of a steam turbine (not shown) via a high-pressure main steam pipe 18. The steam that has completed its work in the steam turbine becomes condensed water in a condenser (not shown), and is again sent to the low-pressure economizer 2 by the water supply pump 9. In the case of the natural circulation type, the only difference is that the circulation force is not based on the circulation pump but on the density difference of the fluid inside the heat transfer tube.
The flow of canned water is almost the same as in the forced circulation type.

By the way, in this type of exhaust heat recovery heat exchanger, a warming operation is performed because thermal stress generated in the low pressure and high pressure steam drums 1, 14 at the time of startup must be reduced. In this operating method, the low pressure and high pressure circulation pumps 10 and 15 are operated with the transfer pump outlet valve 19 fully closed, and the recirculation water pipes 2 provided in the low pressure and high pressure systems respectively are operated.
0 and 21 to the low pressure economizer 2 and low pressure evaporator 3, and to the high pressure economizer 5 and high pressure evaporator 6, respectively. The low-pressure and high-pressure steam drums 1, 14 are warmed by circulating canned water through the low-pressure and high-pressure systems, respectively. Note that the steam generated during this warming is recovered to a condenser using a turbine bypass system (not shown). Furthermore, when the water levels in the low-pressure and high-pressure steam drums 1 and 14 decrease due to the generation of steam, the water supply pump 9 operates to introduce water into the low-pressure steam drum 1, while the high-pressure steam drum 1
4, the transfer pump 14 is activated to move the canned water from the low pressure system to the high pressure system to restore the water level.

However, in the warming operation of such an exhaust heat recovery heat exchanger, the temperature of the exhaust gas 8 led to the exhaust heat recovery heat exchanger is not so high in the initial stage of startup, and it takes a long time for the temperature of the canned water to rise. , there is a problem that warming takes a long time.
FIG. 5 shows an example of startup characteristics when the above-mentioned warming operation is applied. As is clear from Figure 5, the pressure in the high-pressure system rises from an early stage and reaches the standard value in a short time, whereas the pressure in the low-pressure system rises extremely slowly and takes a long time to reach the standard value. It takes. As mentioned above, since low-temperature feed water flows into the low-pressure system as make-up water for the generated steam, the warming time of the low-pressure system becomes even longer.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a combined cycle power plant that can overcome the problems of the prior art described above and has better adaptability to load changes.

[Summary of the invention]

The present invention provides a connecting pipe for supplying canned water from the high pressure steam drum and low pressure steam drum of the waste heat recovery heat exchanger of one unit to the high pressure steam drum and the low pressure steam drum of another adjacent unit, respectively,
During a cold start, the canned water in the high-pressure steam drum and low-pressure steam drum of the waste heat recovery heat exchanger of another unit that is in operation is transferred to the high-pressure steam drum and low-pressure steam drum of the waste heat recovery heat exchanger of the unit that is about to start up. It is characterized in that it is supplied to each of the following.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in more detail using the drawings.

FIG. 1 is a system diagram showing an embodiment of the present invention in a combined cycle power generation plant using a forced circulation type exhaust heat recovery heat exchanger. In Fig. 1, parts indicated by the same reference numerals as in Fig. 4 are
Since the parts are the same as those shown in the figure, their explanation will be omitted. However, in FIG. 1, the unit that is about to be activated is referred to as A unit, and its constituent elements are given an A at the end of their reference numerals. Further, a unit already in operation adjacent to the above-mentioned unit is referred to as a B unit, and its constituent elements are given a B at the end of the reference numeral. The difference from the conventional plant in Fig. 1 is that the high pressure steam drum 4B of the waste heat recovery heat exchanger of the B unit which is in operation and the waste heat recovery heat exchanger of the A unit which is about to be started from the bottom of the low pressure steam drum 1B. First stage moisture separator 16 in high pressure steam drum 4A
Communication pipes 22 and 23 leading to the first stage moisture separator 11A in the A and low pressure steam drums 1A are provided, respectively, and stop valves 24 and 25, pressure Control valve 26,2
7 and stop valves 28 and 29 are provided.

The present invention is constructed as described above, and during warming at the time of a cold start of the A unit, the canned water in the high pressure steam drum 4B and the low pressure steam drum 1B of the exhaust heat recovery heat exchanger of the B unit in operation is reduced to pressure. After the pressure is reduced by the control valves 26 and 27 until it reaches the warming completion pressure of the high-pressure steam drum 4A and the low-pressure steam drum 1A, for example, 15 atg and 2.5 atg, the high-pressure steam of the exhaust heat recovery heat exchanger of the A unit that is being started is released. Water is supplied to the first stage moisture separator 16A in the drum 4A and the first stage moisture separator 11A in the low pressure steam drum 1A, respectively. and,
When the internal pressures of the high-pressure steam drum 4A and the low-pressure steam drum 1A reach the warming completion pressure, the stop valves 24 and 25 are closed to stop the supply of canned water to the high-pressure steam drum 4B and the low-pressure steam drum 1B that are in operation. Stop. The communication pipes 22 and 23 are provided with two stop valves 24, 28 and 25, respectively.
29 is provided, which is a pressure regulating valve 26
This is to stop the flow of canned water during repairs and inspections.

Thus, the present invention applies the high-pressure steam drum 4A and low-pressure steam drum 1A of the exhaust heat recovery heat exchanger of unit A during warming to the high-pressure steam drum 4B and low-pressure steam drum 1A of the exhaust heat recovery heat exchanger of unit B during operation. FIG. 2 shows the increase in internal pressure of the high-pressure steam drum 4A and the low-pressure steam drum 1A by supplying canned water of 1B after reducing the pressure to the warming completion pressure of the high-pressure steam drum 4A and the low-pressure steam drum 1A, respectively. The start-up characteristics can be accelerated, reducing the warming time of high-pressure and low-pressure systems, and the start-up time of a combined cycle power plant during cold starts, thereby increasing the adaptability of the entire plant to load changes. It is possible to increase the

The above embodiment is a case where the present invention is applied to a forced circulation type waste heat recovery heat exchanger, but next, using FIG. 3, an example when the present invention is applied to a natural circulation type waste heat recovery heat exchanger. I will explain about it. The configuration of the present invention in a plant using a natural circulation type waste heat recovery heat exchanger is the same as the case where it is applied to the forced circulation type waste heat recovery heat exchanger shown in Fig. 1. From the bottom of the high pressure steam drum 4B and low pressure steam drum 1B of the recovery heat exchanger, the first stage moisture separator 16A and the low pressure steam drum 1A of the high pressure steam drum 4A of the waste heat recovery exchanger of unit A during startup are detected.
Connecting pipes 22 and 23 leading to the first stage moisture separator 11A are provided respectively, and stop valves 2 are installed in the paths of the connecting pipes 22 and 23 in order from the B unit side.
4 and 25, pressure regulating valves 26 and 27, and stop valves 28 and 29 are provided. The functions of each component are the same as those in FIG. 1 described above, so the explanation will be omitted.

According to this embodiment, the exhaust heat recovery heat exchanger of the A unit during warming is connected to the high pressure steam drum 4A and the low pressure steam drum 1A, and the exhaust heat recovery heat exchanger of the B unit during operation is connected to the high pressure steam drum 4B and the low pressure steam drum 1A. Transfer canned water from steam drum 1B to high pressure steam drum 4.
By supplying the steam after reducing the pressure to the warming completion pressure of A and the low pressure steam drum 1A, it is possible to hasten the rise in the internal pressure of the high pressure steam drum 4A and the low pressure steam drum 1A, shortening the high pressure system and low pressure system warming time. , it is possible to shorten the start-up time of a combined cycle power plant at the time of a cold start, and thereby it is possible to increase the adaptability of the entire plant to load changes.

〔Effect of the invention〕

As explained above, the present invention provides a system for supplying canned water from a high pressure steam drum and a low pressure steam drum of one unit and an exhaust heat recovery heat exchanger to the high pressure steam drum and low pressure steam drum, respectively, of another adjacent unit. The high pressure steam drum of the waste heat recovery heat exchanger of the unit in which the high pressure steam drum and low pressure steam drum of the waste heat recovery heat exchanger of another unit in operation are to be started with a connecting pipe and the canned water of the waste heat recovery heat exchanger of another unit in operation at the time of a cold start. and low-pressure steam drum, the warming time of the waste heat recovery heat exchanger is significantly shortened, and the start-up time of the combined cycle power plant is shortened, resulting in excellent adaptability to load changes. It can be done.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a combined cycle power generation plant showing an embodiment of the present invention applied to a forced circulation type waste heat recovery heat exchanger, and Fig. 2 is a system diagram of a combined cycle power generation plant according to the present invention when applied to a forced circulation type waste heat recovery heat exchanger. Fig. 3 is a diagram of startup characteristics during warming; Fig. 3 is a system diagram of a combined cycle power generation plant showing an embodiment in which the present invention is applied to a natural circulation type waste heat recovery heat exchanger;
The figure is a system diagram showing an example of a conventional forced circulation type exhaust heat recovery heat exchanger, and FIG. 5 is a starting characteristics diagram during warming in the conventional exhaust heat recovery heat exchanger. 1, 1A, 1B...Low pressure steam drum, 3, 3A
...Low pressure evaporator, 4,4A,4B...High pressure steam drum, 6,6A...High pressure evaporator, 9,9A...Water pump, 11,11A,16,16A...1st
Stage moisture separator, 12, 12A, 17, 17A...
Second stage moisture separator, 14, 14A... Transfer pump, 19, 19A... Transfer pump outlet valve, 22,
23... Communication pipe, 24, 25, 28, 29... Stop valve, 26, 27... Pressure regulating valve.

Claims (1)

[Claims] 1. In a combined cycle power plant in which a plurality of adjacent units are each equipped with an exhaust heat recovery heat exchanger, the canned water of the high-pressure steam drum and low-pressure steam drum of the exhaust heat recovery heat exchanger of one unit is Connecting pipes are provided to supply the high-pressure steam drum and low-pressure steam drum of each separate unit, and at a cold start, the canned water of the high-pressure steam drum and low-pressure steam drum of the waste heat recovery heat exchanger of the other unit in operation is started. What is claimed is: 1. A combined cycle power generation plant characterized in that the power is supplied to a high pressure steam drum and a low pressure steam drum of a waste heat recovery heat exchanger of a unit in which the power is to be generated.