JPS5935701A - Waste heat recovery boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust heat recovery boiler, and particularly to a 341t
>This invention relates to a boiler device suitable for preventing evaporation of filtrate.

A conventional exhaust heat recovery boiler of this type is shown in Figure 1.
A configuration in which a superheater 9, an evaporator 7, and an economizer 3 are sequentially disposed in a main stream 2 of high-temperature combustion exhaust gas (hereinafter simply referred to as exhaust gas) flowing inside! Water, which is the fluid to be heated, is supplied to the economizer 3 via the economizer water supply pipe 1, and after being preheated to a predetermined temperature, it passes through the drum water supply pipe 4 and is supplied to the drum 5. The compressed water supplied to the drum 5 is naturally or forcedly circulated in the order of the evaporator 7 body and the drum 5 via the evaporator downcomer pipe 6, and is heated during this time. After being separated from water in step 5, the drum steam is sent to a superheater 9 through an outlet pipe 8, and after being further heated in a steam tank, it is supplied to a steam turbine, etc. (not shown) through a main steam pipe 10, and is used to generate electricity. It is used for etc.

In the waste heat recovery boiler, each heat exchanger is designed to be as efficient as possible based on the rated load that is frequently used. Therefore, it is desirable for the water temperature of the economizer 3 to be lower than the saturation temperature of the drum pressure, but as close to this temperature as possible, and the heat transfer area is also designed based on this idea. By the way, it is known that at the above-mentioned exhaust heat recovery boiler pressure, the partial load characteristic of the boiler inlet exhaust gas temperature is different from that of a normal boiler.

That is, as shown in Fig. 2, in a normal boiler, the boiler inlet exhaust gas flow rate 14 and the exhaust gas temperature 16 change in almost the same proportion to the load, whereas in a lit heat recovery boiler, the As the temperature decreases, the boiler inlet exhaust gas temperature 15 becomes low -F-, t'- as in a normal boiler, but the boiler exhaust gas flow @13 has the advantage that it does not drop much due to the operational constraints of the exhaust gas generator. Therefore, when operating the waste heat recovery boiler, if the design concept of the conventional heat exchanger is applied as is, the outlet water temperature of the economizer 3 at low load and 1 tot is the saturation temperature of the drum pressure J. If it is operated under such conditions, the generation and disappearance of steam bubbles in the three tubes of the economizer will cause vibrations in the heat transfer tubes, leading to damage to the equipment. . In order to prevent this, conventionally, a large amount of water is supplied through the water economizer water supply pipe l shown in FIG. Excess water supplied in excess of the above temperature is controlled to be kept lower than the saturation temperature of the drum pressure by a certain temperature difference by returning the water to the condenser through the economizer pulley pipe 12. In the water supply system, the water supply flow under the rated load is much faster than the rated load, and as a result, the capacity of the water supply pump must be made very large. During high loads when there is no need to increase the water supply in the energy saver 3, the driving force of the energy saver becomes excessive and the energy efficiency deteriorates, resulting in disadvantages such as ℃ .

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to maintain the outlet water temperature of the economizer at a temperature lower than 1 degree Celsius of drum pressure without increasing the size of the water supply pump. Recovery boiler is to be provided.

In order to achieve the above object, the present invention provides an exhaust heat recovery boiler in which a fuel economizer is installed in the main stream of the combustion exhaust gas, and a combustion exhaust gas duct which bypasses the energy economizer. ,
The duct is characterized by being provided with a flow rate regulating means (damper, etc.) for the combustion exhaust gas flowing through the duct.

With the above configuration, a part of the exhaust gas passing through the economizer can be sent to the inno gas duct according to load fluctuations, so the flow of exhaust gas passing through the economizer can be controlled to a desired flow rate. The above desired flow rate is
It is understood as the flow rate required to maintain the temperature of the economizer outlet water as close as possible to, but lower than, the saturation temperature at the drum pressure, which is determined according to load fluctuations.

The bypass duct characteristically provided in the present invention is:
Any structure may be used as long as it allows exhaust gas to bypass the economizer. Further, a damper as a flow rate regulating means is generally installed in the bypass duct, but it may also be installed at the inlet or outlet of the bypass duct. This damper is preferably of an opening control type, but may be of an opening/closing type.

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the drawings.

The device shown in FIG. 3 includes the parts shown in FIG. 1 except for 12 and the parts whose explanations are similarly referred to, and a bypass duct provided at the lower part of the myositis 53 to bypass it. 17, and an opening control type damper 18 provided in the bypass duct 17.

In the device configured as described above, the damper 18 is closed at the rated load, and the exhaust gas 2 that has passed through the evaporator 7 is thereby completely saved and sent to the coalizer 3. However, at startup or at low load, the damper 18 is closed. A part of the exhaust gas (exhaust gas bypass flow) 19 is opened in response to the
Since the water flows through the bypass duct 17 and does not participate in the heating of the economizer 3, an excessive rise in the water temperature at the outlet of the economizer 3 is suppressed.

Next, the device shown in FIG. 4 shows the control system of the device shown in @FIG. A temperature calculator 22 , a calculator 24 for calculating the outlet water temperature target value of the economizer 3 from the converted saturation temperature signal and the boiler load signal 23 which is its corrected prediction information; A detector 20, a calculator 25 that calculates a temperature deviation between the water temperature detected by the water temperature detector 20 and the water temperature target value, and an arithmetic unit 25 that calculates the opening degree of the damper 18 from the temperature deviation signal. It mainly consists of a damper opening degree modifier 26 that opens and closes the damper 18 based on the calculated results.

With the above configuration, the damper 18 is automatically opened and closed in response to load fluctuations, thereby maintaining the water temperature at the outlet of the economizer 3 at the water temperature target value calculated by the calculator 24. As a result, the water at the outlet of the economizer 3 will not evaporate even during startup or under low load, so the heat transfer tubes of the economizer 3 may vibrate or break due to the generation and disappearance of steam bubbles. 4- There will be no danger of causing an accident.

In addition, the device shown in FIG. 5 uses an energy saver 30 detected by a detector 27 instead of the general load signal 23 shown in FIG.
The configuration is similar to that of the device shown in FIG. 4, except that the inlet exhaust gas temperature is used as an example of the load signal.

Also in this configuration, the water temperature at the outlet of the economizer 3 can be maintained at the water temperature target value calculated by the calculator 24 in the same way as in the case of FIG. 4, and the same effect can be achieved.

As described above, according to the present invention, by providing the exhaust gas bypass duct that bypasses the energy saver in the exhaust gas flow path of the exhaust heat recovery boiler and the damper for adjusting the flow rate of the exhaust gas flowing through the duct,
The temperature of the water at the outlet of the economizer can be kept below the saturation temperature of the drum pressure during boiler startup and under full load, which prevents the heat transfer tubes from vibrating or causing damage due to the generation and disappearance of steam bubbles. disappears. In addition, since there is no need to increase the water supply flow rate and suppress the width of the water at the outlet of the energy saver, the water supply pump can be small-sized, which is advantageous in terms of equipment area and cost, as well as providing excellent energy efficiency. .

[Brief explanation of drawings]

Figure 1 shows the conventional exhaust heat recovery boiler system diagram (6) and Figure 2 (
A) and (B) are diagrams showing the load characteristics of an exhaust heat recovery boiler in comparison with a normal boiler. (A) is a diagram showing the relationship between exhaust gas flow rate and load, and (B) is a relationship between exhaust gas temperature and load. 3 is a system diagram of the exhaust heat recovery boiler according to the embodiment of the present invention,
4 is a control system diagram of the apparatus according to the embodiment of the present invention shown in FIG. 3, and FIG. 5 is another control system diagram of the apparatus according to the embodiment of the invention shown in FIG. 1... Economizer water supply pipe, 2... Exhaust gas main stream, 3...
Economizer, 4...Drum water supply pipe, 5...Drum, 17
...Bypass duct, 18...Damper, 19...
Bypass exhaust gas flow, 20... Economizer outlet water temperature detector,
21...Pressure detector, 22...Saturation temperature calculator, 2
3... Boiler load signal, 24... Economizer outlet water temperature target value calculator, 25... Temperature deviation calculator, 26...
Damper opening degree calculator, 27... Economizer inlet exhaust gas temperature detector. Patent Attorney Takeshi Kawakita Nagatsutsu 1 Figure 2 1'Beak Figure 3 Figure 4 Figure 5 Figure 4

Claims (1)

[Claims] (1) In an exhaust heat recovery boiler equipped with a fuel economizer in the flue gas main stream, a flue gas bypass duct that bypasses the fuel economizer and a flow rate adjustment means for the flue gas flowing through the core duct are provided. An exhaust heat recovery boiler characterized by the installation of an exhaust heat recovery boiler.