JPH0227282Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a natural circulation type exhaust heat recovery boiler, and particularly to a boiler device suitable for preventing low-temperature corrosion of a economizer.

As shown in Figure 1, the natural circulation type waste heat recovery boiler has a low pressure economizer 6, a low pressure evaporator, a high pressure economizer 8, a high pressure evaporator 9, and a superheater installed in the flue from the downstream side to the upstream side of the exhaust gas. The water supply indicated by W in the figure is supplied to the low-pressure economizer 6 via the low-pressure water supply pump 3, and the water preheated here is supplied to the low-pressure energy saver 6 via the low-pressure water supply regulating valve is supplied to the drum 1.

On the other hand, a portion of the preheated water from the low-pressure economizer 6 is supplied to the high-pressure economizer 8 via the high-pressure water pump 4 . Further, the water supply heated by the high-pressure economizer 8 is supplied to the high-pressure drum 2 via the high-pressure water supply adjustment valve 13.

Further, the drum water in the low pressure drum 1 is naturally circulated via the low pressure evaporator 7, and the low pressure steam generated in the low pressure drum 1 is supplied to a low pressure turbine (not shown). Further, the drum water in the high pressure drum 2 is naturally circulated via the high pressure evaporator 9, and the steam generated in the high pressure drum 2 is superheated in the superheater 10.
This superheated steam is turned into a high-pressure turbine (not shown)
is supplied to

In the case of such a natural circulation heat recovery boiler system without a deaerator installed, the temperature of the feed water supplied to the low pressure economizer 6 is low, so the temperature of the exhaust gas at the gas outlet side of the low pressure economizer 6 is low. If it gets too cold, water vapor in the exhaust gas will condense on the outer surface of the tube of the low-pressure economizer 6, causing corrosion of the outer surface of the tube of the low-pressure economizer 6, a problem called low-temperature corrosion.

Conventionally, no particular measures have been taken to deal with the problem of low-temperature corrosion on the outer surface of the economizer tube, and appropriate countermeasures have been desired.

An object of the present invention is to provide a natural circulation type waste heat recovery boiler that meets the above-mentioned demands and can eliminate low-temperature corrosion on the outer surface of the tube of the economizer.

In short, the present invention provides a bypass line that branches off from the water supply line from the economizer to the drum in a natural circulation waste heat recovery boiler, and uses the thermal energy of the feed water in this bypass line to heat the water supplied to the economizer. This is accomplished by providing a feed water preheating device with means for

Hereinafter, embodiments of the present invention will be described based on the drawings.

Figures 2 to 4 show embodiments of the present invention;
Components that are the same as those in the figures are indicated by the same reference numerals.

In FIG. 2, the difference from the conventional natural circulation type waste heat recovery boiler shown in FIG. A bypass line extending to the side is provided, a low pressure economizer recirculation regulating valve 14 is interposed in this bypass line, and a circulation system to the inlet of the low pressure water supply pump 3 is provided.

In this natural circulation type waste heat recovery boiler, the feed water W is pressurized by the low pressure water supply pump 3 and flows into the low pressure economizer 6 . A part of the water supply heated by the low pressure economizer 6 is supplied to the low pressure drum 1 via the low pressure water supply regulating valve 12 .

Further, the other part of the water supply preheated by the low-pressure economizer 6 is transferred to the high-pressure economizer 8 via the high-pressure water supply pump 4.
will be introduced in In addition, a part of the preheated water from the low-pressure economizer 6 is supplied via the low-pressure economizer flow rate adjustment valve 14.
The water is returned to the upstream side of the low-pressure water supply pump 3, mixed with the low-pressure water supply, and the low-pressure water supply is heated.

In the case of this embodiment, the water supply circulation of the low-pressure energy saver 6 is performed by the discharge pressure of the low-pressure water supply pump 3, which has a relatively low discharge pressure, and the temperature of the water supply is increased without providing a special dedicated pump. Low-temperature corrosion on the outer surface of the tube of the vessel 6 can be eliminated.

FIG. 3 is a system diagram of main parts of the natural circulation type waste heat recovery boiler of the present invention, and the constituent parts other than those shown in FIG. 3 are the same as those in FIG. 2.

In this natural circulation type waste heat recovery boiler, hot water at an optimal pressure is extracted from the intermediate stage of the high-pressure feed water pump 4, and a bypass line with a low-pressure economizer recirculation adjustment valve 14 is connected to the low-pressure feed water pump 3. Connected to the downstream side (outlet side). In this natural circulation type waste heat recovery boiler, there is no need to install a dedicated pump for recirculating the low-pressure economizer, and the intermediate stage where water exits the low-pressure economizer 6 and is pressurized by the high-pressure feed pump 4 is used. Since water is extracted at a suitable pressure and returned to the outlet side of the low-pressure water supply pump 6, there is no consumption of shaft power in the high-pressure water supply pump 4, and by heating the water supply, the outer surface of the tube of the low-pressure energy saver 6 is reduced. can prevent low-temperature corrosion.

FIG. 4 is a system diagram of the main parts of the natural circulation type waste heat recovery boiler of the present invention, and the components not shown are the same as the embodiment shown in FIG. 2.

In FIG. 4, the water supply line from the low-pressure water economizer 6 to the high-pressure water supply pump 4 is installed in a water supply preheater 15 provided in the middle of the water supply line from the low-pressure water supply pump 3 to the low-pressure water economizer 6, and this water supply preheating is performed. The water supplied from the low-pressure water pump 3 is preheated in the container 15.

In the case of this embodiment, the feed water preheater 15
By appropriately selecting the preheating capacity of W as a design value, it is possible to warm the feed water W and prevent low-temperature corrosion. In this case, the system is such that the entire flow of water from the low-pressure economizer 6 to the high-pressure water pump 4 contributes to preheating the water supplied to the low-pressure economizer 6.

In the embodiment described above, there is no need to install a dedicated pump for recirculating the water to the low-pressure economizer 6, and the hot water pressurized to a high pressure by the high-pressure water supply pump 4 can be depressurized and recirculated. Therefore, the water supplied to the low-pressure economizer 6 can be heated and low-temperature corrosion can be prevented without consuming unnecessary shaft power of the high-pressure water supply pump 4.

In the embodiment described above, in addition to the low-pressure economizer 6 and the low-pressure evaporator 7, the high-pressure economizer 8 and the high-pressure evaporator 9 are
Although an example of a natural circulation heat recovery boiler equipped with The present invention can also be applied to a boiler that includes a drum and an evaporator and circulates drum water between the drum and the evaporator by natural circulation.

[Effect of idea]

As described above, according to the present invention, the water supplied to the economizer is heated to a predetermined temperature, so that the temperature of the exhaust gas on the gas outlet side of the economizer does not become too cold. Condensation of water vapor in the exhaust gas on the outer surface of the economizer tube is eliminated, and so-called low-temperature corrosion in which the outer surface of the economizer tube corrodes can be prevented.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional natural circulation type waste heat recovery boiler, Figure 2 is a system diagram showing an embodiment of the natural circulation type exhaust heat recovery boiler of the present invention, and Figure 3 is a system diagram of the natural circulation type of the present invention. FIG. 4 is a system diagram showing another embodiment of the exhaust heat recovery boiler. FIG. 4 is a system diagram showing still another embodiment of the present invention. 1...Low pressure drum, 2...High pressure drum, 3...
Low pressure water supply pump, 4... High pressure water supply pump, 6...
Low pressure energy saver, 7...Low pressure evaporator, 8...High pressure energy saver, 9...High pressure evaporator, 10...Superheater, 12...
...Low pressure water supply adjustment valve, 13...High pressure water supply adjustment valve, 1
4...Low pressure economizer recirculation regulating valve, 15...Water preheater.

Claims (1)

[Scope of utility model registration request] A natural circulation waste heat recovery boiler in which a fuel economizer, a drum to which feed water preheated by the energy saver is supplied, and boiler water in the drum circulates between the drum and the evaporator by natural circulation, A feed water preheating device comprising: a bypass line branched from the water supply line from the economizer to the drum; and a means for using the thermal energy of the feed water in the bypass line to heat the water supplied to the economizer. Natural circulation type exhaust heat recovery boiler.