JPH028201B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a waste heat recovery boiler, and in particular to a waste heat recovery boiler equipped with a energy saver that does not cause water hammer when the boiler is started and can heat the feed water well when the boiler is operating. Regarding boilers.

With recent changes in electricity demand, there is a growing trend to adopt gas turbines for peak loads.The heat of the high-temperature gas that provides kinetic energy to the gas turbine is recovered in a waste heat boiler, and further Combined power generation, in which steam generated by a heat boiler drives a steam turbine to generate electricity, is being implemented to save energy.

Figure 1 shows a waste heat recovery boiler (hereinafter simply referred to as "boiler").
The following is an outline of the In the figure, 1 is a gas turbine, in which high-temperature combustion gas generated by air A and fuel F operates the gas turbine 1 to generate electricity, and then is supplied as waste gas to a boiler 2, which is then sent to a superheater 3 and an evaporator. 4 and the economizer 5, and then discharged to the outside of the system. On the other hand, the generated steam flows into the superheater 3 from the boiler drum 6, is superheated to a predetermined temperature, and is then supplied to the steam turbine 7 to generate the second power generation, and the used steam is returned to water in the condenser 8. After that, it is supplied to the boiler again as feed water W.

Although the boiler with the above configuration effectively utilizes the generated heat and saves energy, it has the following problems.

That is, gas turbines are used for peak loads because they have very good load followability, but as a result, gas turbines are started and stopped many times and often undergo rapid load fluctuations. The waste heat recovery boiler also starts and stops in response to this load change, but when the boiler stops or when the load suddenly decreases, part of the water supplied in the economizer evaporates, causing what is called water hammer when the boiler starts. will occur. The state in which steam is generated within the economizer will be explained with reference to FIG.

Normally, the water supply temperature at the outlet of the economizer is operated at a temperature below the saturation temperature (curve A shows the saturation temperature curve), for example, at the temperature shown in curve B. Suppose that the boiler was currently operating at pressure P ₂ and is now reduced to pressure P ₁ .
In this case, if the pressure drop is gradual, the temperature of the hot water will also gradually drop from T ₂ to T ₁ in response to the pressure drop, so the feed water will never rise above the saturation temperature. On the other hand, if the pressure drop is rapid, the temperature drop of the feed water cannot correspond to the pressure drop, and the temperature T ₂
The pressure will drop to P ₁ in a state close to . For this reason, when the feed water temperature is between T ₂ and T ₁ ' at pressure P, the feed water becomes equal to or higher than the saturation temperature, and a portion of the feed water evaporates and remains in the energy saver. This change in state occurs more drastically when the boiler operation is abruptly stopped than in the above-mentioned case where the boiler pressure decreases.

In addition to the reasons explained above, a considerable amount of heat remains inside the waste gas duct immediately after the boiler is stopped, and the feed water accumulated in the economizer absorbs this residual heat, raising the temperature and producing steam. Situations that occur also occur.

If the boiler is restarted with residual steam generated due to these reasons, the water supplied in the economizer will violently collide with the pipe wall, causing a large impact on the pipe body and causing water hammer, which may damage the pipe body. , the amount of water supplied to the boiler drum becomes unstable. Particularly when the water supply is descending, the descending water supply collides with the rising steam, resulting in severe water hammer.

For this reason, the inventors connected the upper and lower ends of the straight pipes with headers to form a single heat transfer panel, and connected multiple heat transfer panels with the upper and lower common headers to save energy. I provided something suitable. In this type of economizer, the water supply only ascends through the straight pipes of each panel, so even if steam is generated in the pipes, water hammer hardly occurs, but there are the following problems. In other words, the supply water rises through the straight pipes of each panel, is collected in a common header, and is sent to the upper shell, so there is a risk that heat exchange with the waste gas will be insufficient, and the temperature of the supply water is controlled by each heat exchanger tube. The control is complicated because it is performed by controlling the flow rate of the water. In other words, if the problem of water hammer is ignored, thermal efficiency will be better and control will be easier if the heat transfer tube of the economizer is made by bending the long tube body to increase the heat transfer area of each heat transfer tube.

In view of the above-mentioned problems, the purpose of this invention is to provide good heat recovery efficiency and easy control during boiler operation.
To provide a waste heat recovery boiler that does not generate water hammer when starting the boiler.

In short, this invention configures an integrated energy saver by connecting a plurality of heat transfer panels with upper and lower common headers, and connects each heat transfer panel with a downcomer pipe.
When the boiler is in operation, the feed water flows through this downpipe, and when the boiler is not in operation, all the feed water flows upward through the straight pipe of the heat transfer panel, making it easy to remove generated steam and prevent water hammer. It is composed of

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows an embodiment of the invention.

In the figure, an arrow 10 indicates an economizer placed within the gas duct 11. Reference numeral 10a indicates a heat exchanger tube panel constituting the economizer 10. This panel consists of a plurality of straight pipes 30 arranged inside the gas duct 11, and an upper header 12 and a lower header 13 that connect both ends of the straight pipes 30 outside the gas duct. 31 is a downcomer pipe that connects the upper header 12 of the panel on the upstream side of the water supply flow and the lower header 13 of the panel on the downstream side of the water supply flow adjacent to this panel, and each panel constituting the energy saver 10 is connected to this downcomer. By connecting with the downcomer pipe 31, the economizer is integrally formed.

The energy saver 10 is constructed by arranging a plurality of panels formed in this way in parallel. The upper header 12 of each panel 10a has a control valve 14
It is connected to an upper common header 16 by a conduit 15 having a diameter. On the other hand, the lower header 13 is connected to the lower common header 18 by a conduit 17 having a control valve 32. Next, the upper common header 16 is connected to the economizer cyclone 21 in the upper shell 20 through a pipe 19, and one end of the lower common header 18 is connected to a water supply pump 24 through a water supply pipe 23 having a water supply control valve 22, and the other end is connected to a water supply pump 24 through a water supply pipe 23 having a water supply control valve 22. The end is connected to the downcomer pipe 27 of the upper shell 20 by a recirculation line 26 having a recirculation flow control valve 25.
is connected to. Next, a temperature sensor 29 is installed on the upper header 12. 28 is a control box for storing memory and issuing command signals;
4, the water supply control valve 22, the recirculation flow rate control valve 25, the blow valve 33 provided in the lower common header 18, and the temperature sensor 29, respectively, are connected in circuits.

In the above equipment, during boiler operation, the control box 2
All valves 14 are fully closed by the command signal No. 8. Thereby, the water supply W fed from the water supply pump 24 ascends the straight pipe 30 of the panel on the most upstream side of the water supply flow and reaches the upper header 12. In this case, since the control valve 14 is closed, the water supply reaches the lower header 13 of the adjacent panel via the downcomer pipe 31, and by repeating this upward and downward movement, it flows from the upper header 12 on the most downstream side to the upper common header 16. Leading pipe 1
9 and flows into the upper body 20. In this case, if the upper common header 16 is arranged obliquely as shown by reference numeral 16 with the pipe line 19 side facing upward, the internal fluid can be better discharged. During boiler operation, the thermal efficiency is increased by allowing the feed water W to flow through each of the straight pipes 30 and the descending pipes 31 as described above, and the flow rate of the feed water W is also controlled by the valve 22.
It can be done only by In addition, the control box 28 detects the temperature of the feed water in the upper header 12 using the temperature detector 29 during boiler operation, and depending on the detection result, the valve 1
Adjust 4 and 32. By adjusting these valves 14 and 32, an upward flow is formed through the lower header 18 to the conduit 30 without passing through the descending pipe 31 on the downstream side detected at 29, and is supplied to the upper header 16 through the valve 14. I'll do what I do. This operation prevents flow instability such as water hammer in the downcomer.

Next, when the operation of the boiler must also be stopped due to the stoppage of the gas turbine, the feedwater pump 24 is also stopped, and the flow of feedwater in the energy saver 10 is stopped. For this reason, when the pressure inside the boiler suddenly drops, the temperature of the feed water in the economizer becomes higher than the saturation temperature, and a portion of the feed water evaporates. Further, even if the pressure does not drop suddenly, the temperature of the supply water stagnant in the gas duct 11 etc. may rise and some of the water may evaporate.

The control box 28 opens the control valves 25, 32, and 14 when the operation of the boiler is stopped. As a result, the steam generated in the straight pipe 30 and the downcomer pipe 31 of the economizer rises, passes through each upper header 12, flows into the upper common header 16, and further passes through the pipe line 19 to the upper shell 2.
It is purged to the 0 side. In other words, by stopping the supply of water, the steam generated in the economizer and the water supply inside the economizer all flow upward, allowing for good steam purging and preventing water hammer from occurring when the boiler is restarted. By supplying canned water to the water supply pump outlet at startup, the temperature of the water supply can be increased quickly, and the boiler can be started up quickly.

By implementing this invention, it is possible to effectively prevent water hammer from occurring due to steam remaining in the economizer when the boiler is restarted, increase thermal efficiency during boiler operation, and easily control water supply. .

[Brief explanation of drawings]

Figure 1 is a system diagram of a conventional waste heat recovery boiler, Figure 2 is a system diagram of a conventional waste heat recovery boiler.
The figure is a diagram showing the relationship between pressure and saturated steam temperature, and FIG. 3 is a system diagram of the waste heat recovery boiler according to the present invention. 10... Economizer, 10a... Panel, 11...
Waste gas duct, 12... Upper header, 13... Lower header, 14... Control valve, 16... Upper common header, 18... Lower common header, 22... Water supply control valve, 24... Water supply pump, 25... ...Recirculation amount control valve, 27... Downpipe, 28... Control box, 29...
...Temperature detector, 30... Straight pipe, 31... Downpipe,
32...Control valve, W...Water supply.

Claims (1)

[Scope of Claims] 1 Straight pipes located in a gas turbine waste gas duct are connected by an upper header and a lower header to form a panel, and a plurality of these panels are placed in the waste gas duct with the panel surfaces parallel, An energy saver is constructed by repeatedly connecting the upper header of the upstream panel for water supply flow and the lower header of the downstream panel adjacent to this panel with a downcomer pipe to form one water supply pipe. , the upper header of each panel is connected via a control valve to the upper common header, and the lower header is also connected via a control valve to the lower common header, and the lower common header is connected via a recirculation control valve. Connect the boiler downcomer and pipe line through
A gas turbine waste heat recovery boiler characterized in that the gas turbine waste heat recovery boiler is configured to generate only an upward flow of feed water in straight pipes and downcomer pipes that are energy saving pipes when the gas turbine is stopped. 2 A temperature sensor is installed on the upper header of each panel, and the control valves connected to the upper and lower headers of each panel are controlled by the memory that receives the temperature signal and the command from the control box that issues the command signal. 2. The gas turbine waste heat recovery boiler according to claim 1, wherein the gas turbine waste heat recovery boiler is configured to be able to adjust the flow rate of the water supply.