JPH10325507A - Water supply system for pressurized fluidized bed boiler - Google Patents

Abstract

(57) [Problem] To prevent acid components in combustion exhaust gas from condensing on a low-temperature portion of a low-pressure gas cooler during low-load operation without causing a rise in equipment costs and power costs. SOLUTION: A main steam 25 is taken out from an in-layer evaporator 8 of a fluidized-bed boiler main body 2 provided inside a pressure vessel 1 and is worked. In a water supply system of a pressurized fluidized-bed boiler circulated to the in-layer evaporator 8 through a deaerator 36, a booster pump 38, a water supply pump 39, and a high-pressure gas cooler 15, 14 in this order, the deaerator The booster pump 3 in the high-pressure water supply system 40 from 36 to the evaporator 8
8 is a return flow path 4 that guides a part of the high-temperature high-pressure water 41 from an appropriate position and circulates to the inlet of the low-pressure gas cooler 16.
8, and an on-off valve 49 is provided in the return channel 48.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a water supply system for a pressurized fluidized-bed boiler.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional pressurized fluidized-bed boiler in which a fluidized-bed boiler main body 2 is placed in a pressure vessel 1 in which a pressurized atmosphere is supplied by the supply of pressurized air 1a.
The air diffuser 3 is arranged inside the lower part of the fluidized-bed boiler main body 2.

The upper part of the air diffuser 3 is filled with sand, and a coal fuel 4 and a desulfurizing material 5 such as limestone are also charged. The sand, the coal fuel 4, the desulfurizing material 5, etc. The fuel is fluidized and agitated by the pressurized air 1a which is taken into the air diffuser 3 from the inlet 3a and jetted upward, so that the coal fuel 4 is efficiently burned. A high-temperature fluidized bed 7 composed of bed ash 6 in which ash, desulfurized material 5, sand, etc. are mixed, heats the in-layer evaporator 8 and the reheater 9 installed in the fluidized bed 7. ing.

[0004] The flue gas 1 b heated in the in-layer evaporator 8 and the reheater 9 is dust-removed by a cyclone 10, then goes out of the pressure vessel 1 and is further dust-removed by a ceramic filter 11. , Low pressure gas turbine 1
3 and then to a chimney 20 through a denitration device (not shown), high-pressure gas coolers 14 and 15, and a low-pressure gas cooler 16 in that order.

[0005] The high-pressure gas turbine 12 is provided with a high-pressure compressor 17 and a gas turbine generator 18 coaxially, and the low-pressure gas turbine 13 is provided with a low-pressure compressor 19 coaxially. The air that has been suctioned by the low-pressure compressor 19 and primarily pressurized is
After being cooled by an intercooler (not shown), it is secondarily pressurized by the high-pressure compressor 17 to be supplied to the pressure vessel 1 as pressurized air 1a.

A high-pressure steam turbine 21, a medium-pressure steam turbine 22, a low-pressure steam turbine 23, and a steam turbine generator 24 are arranged coaxially outside the pressure vessel 1, and the fluidized-bed boiler is provided. The main steam 25 from the in-layer evaporator 8 in the main body 2 is guided to the high-pressure steam turbine 21 to drive the high-pressure steam turbine 21, and then guided to the reheater 9 to be reheated. It becomes reheated steam 26,
Next, the steam is guided to the medium-pressure steam turbine 22 to drive the medium-pressure steam turbine 22, and then to the low-pressure steam turbine 23 to drive the steam turbine generator 24, and then to the condenser 27. Is cooled by the cooling water 29 circulated by the circulating water pump 28 and condensed. The low-pressure water 31 is supplied to the low-pressure water heaters 32 and 33 by the condensate pump 30 via the low-pressure water supply system 35a. And
Low-pressure bleed air extracted from the low-pressure steam turbine 23
, And is supplied to the deaerator 36 as low-pressure supply water 31 ′.

A part of the low-pressure water 31 from the condensate pump 30 is guided to the low-pressure gas cooler 16 via a low-pressure water supply system 35b.
Is heated by the combustion exhaust gas 1b passed through the
And the low-pressure water 31 ′ from the low-pressure water heaters 32 and 33 is supplied to the deaerator 36, and the medium-pressure bleed air extracted from the medium-pressure steam turbine 22 by the deaerator 36. It is heated by 37 and degassed.

The feed water degassed by the deaerator 36 is pressurized in two stages by a booster pump 38 and a feed water pump 39 so as not to cause cavitation, and becomes high-pressure feed water 41. 1
After being sequentially guided to 5, 14 and heated by the combustion exhaust gas 1b, it is circulated to the in-layer evaporator 8 inside the fluidized-bed boiler main body 2 via the inlet header 8a,
The high-pressure water 41 circulated through the in-straight evaporator 8 becomes the main steam 25 again and is supplied to the high-pressure steam turbine 21.

A part of the high-pressure water 41 from the water pump 39 is guided to high-pressure water heaters 43 and 44 via a high-pressure water system 42, and the high-pressure water turbines 43 and 44 cause the high-pressure steam turbine 21. High-pressure bleed 4 extracted from
After being heated by 5, it is combined with the high-pressure water 41 from the high-pressure gas cooler 15 and supplied to the high-pressure gas cooler 14.

[0010]

However, in the low-pressure gas cooler 16 of such a pressurized fluidized-bed boiler, the combustion exhaust gas 1b whose temperature has been reduced by the heat recovery by the high-pressure gas coolers 14, 15 is still not sufficiently preheated. Since it is cooled by the low-pressure supply water 31 of a relatively low temperature that is not formed, if the temperature of the combustion exhaust gas or the temperature of the supply water is low during low-load operation, the metal temperature in the low-temperature portion of the low-pressure gas cooler 16 is too low. As a result, the acid component in the combustion exhaust gas 1b may be condensed, and corrosion may occur in the heat transfer tube, or the condensed acid component may act as a binder to cause adhesion of combustion ash.

For this reason, conventionally, an outlet and an inlet of the low-pressure gas cooler 16 in the low-pressure water supply system 35b are connected by a water supply circulation passage 46, and a circulation pump 47 is provided in the water supply circulation passage 46, so that the low-pressure gas cooler 16 operates during low load operation. A part of the low-pressure water 31 'is circulated from the outlet to the inlet of the low-pressure gas cooler 16 to raise the temperature of the water supplied to the low-pressure gas cooler 16, and the low-temperature portion of the low-pressure gas cooler 16 is maintained at a temperature equal to or higher than the dew point of the acid component in the combustion exhaust gas 1b. However, in such a case, there is a problem that facility cost is required for the circulation pump 47 and the like, and power cost of the circulation pump 47 during low load operation is increased.

Further, the low-pressure feed water 31 'whose heat has been recovered from the flue gas 1b at a relatively low temperature by the low-pressure gas cooler 16 and whose temperature has just been raised is not so high. In order to reliably maintain the temperature above the dew point of the acid component, a relatively large amount of low-pressure water 3
1 'must be circulated, and the differential pressure of water supplied to the low-pressure gas cooler 16 during normal operation and low-load operation increases, and the power of the upstream condensate pump 30 must be increased during low-load operation. There was also a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents acidic components in combustion exhaust gas from condensing on a low-temperature portion of a low-pressure gas cooler during a low-load operation without causing a rise in equipment costs and power costs. It is intended to be.

[0014]

According to the present invention, a main steam is taken out from an in-layer evaporator of a fluidized-bed boiler main body provided inside a pressure vessel and worked, and then condensed by a condenser. In a water supply facility of a pressurized fluidized-bed boiler that is circulated to the in-layer evaporator by sequentially passing through a low-pressure gas cooler, a deaerator, a booster pump, a water supply pump, and a high-pressure gas cooler, the in-layer evaporation from the deaerator A return flow path for guiding a part of the high-temperature high-pressure water supply from an appropriate position after the booster pump in the high-pressure water supply system to the vessel and circulating at the inlet of the low-pressure gas cooler was provided, and an on-off valve was provided in the return flow path. It is characterized by the following.

When the open / close valve of the return flow path is opened during low-load operation, a portion of the high-temperature high-pressure water is partially supplied to the high-pressure water because the pressure after the booster pump in the high-pressure water supply system is high. It is led from the system and circulated to the inlet of the low-pressure gas cooler, the feed water temperature for the low-pressure gas cooler is raised by the introduction of the high-temperature high-pressure feed water, and the low-temperature portion of the low-pressure gas cooler 16 has a temperature higher than the dew point of the acid component in the combustion exhaust gas 1b. Kept at temperature.

In the present invention, the return passage may be provided so as to guide a part of the high-temperature high-pressure supply water from the outlet of the booster pump and circulate it to the inlet of the low-pressure gas cooler. It is also possible to provide such that a part of the supply water is guided and circulated to the inlet of the low-pressure gas cooler.

[0017]

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

FIG. 1 shows an example of an embodiment of the present invention, and the portions denoted by the same reference numerals as those in FIG. 4 represent the same components.

In the pressurized fluidized-bed boiler having substantially the same configuration as that of FIG. 4 described above, a feedwater circulation passage provided with a circulation pump is provided between the outlet and the entrance of the low-pressure gas cooler 16 in the low-pressure water supply system 35b. Instead, between the outlet of the booster pump 38 and the inlet of the low-pressure gas cooler 16 in the high-pressure water supply system 40 extending from the deaerator 36 to the in-layer evaporator 8, the high-pressure high-pressure water 41 from the outlet of the booster pump 38. A return flow path 48 for guiding a part of the high pressure water cooler 16 is provided in the return flow path 48, and an open / close valve 49 is provided in the return flow path 48 so as to appropriately block the flow of the high pressure water 41.

Thus, during the low load operation, the return flow path 48
When the on-off valve 49 of the high-pressure water supply system 40 is opened, a part of the high-temperature high-pressure water 41 is guided from the outlet of the booster pump 38 because the pressure after the booster pump 38 in the high-pressure water supply system 40 is high. And the supply water temperature to the low-pressure gas cooler 16 is raised by the circulation of the high-temperature high-pressure supply water 41, and the low-temperature portion of the low-pressure gas cooler 16 is maintained at a temperature equal to or higher than the dew point of the acid component in the combustion exhaust gas 1b. Become.

Therefore, according to the above embodiment, a part of the high-temperature high-pressure water 41 is guided from the outlet of the booster pump 38 of the high-pressure water supply system 40 and circulated to the low-pressure gas cooler 16, whereby the water supply temperature to the low-pressure gas cooler 16 is increased. And the low temperature part of the low pressure gas cooler 16 is
Since the temperature can be maintained at a temperature equal to or higher than the dew point of the acid component in the fuel gas, it is possible to prevent the acid component in the combustion exhaust gas 1b from condensing at the low temperature portion of the low pressure gas cooler 16 during low load operation. Problems such as corrosion of the heat pipe or adhesion of combustion ash due to the condensed acid component serving as a binder can be prevented beforehand.

Further, since the pressure after the booster pump 38 of the high-pressure water supply system 40 is high, a high-pressure high-pressure water supply 41 can be obtained simply by opening the on-off valve 49 provided in the return passage 48 without providing a circulation pump or the like. Can be circulated to the inlet of the low-pressure gas cooler 16, so that equipment costs can be reduced, and the power cost for circulating the low-pressure feed water 31 ′ at the outlet of the low-pressure gas cooler 16, which has been conventionally required. Can be eliminated.

In addition, the high-pressure feed water 41 guided from the outlet of the booster pump 38 is heated by the medium-pressure bleed 37 extracted from the medium-pressure steam turbine 22 by the deaerator 36 after recovering heat from the combustion exhaust gas 1b by the low-pressure gas cooler 16. And the temperature has been raised sufficiently, it is only necessary to circulate a smaller amount of high-pressure water 41 than the low-pressure water 31 'conventionally circulated by the circulation pump. The pressure difference between the water supply of the gas cooler 16 and the condensate pump 30 on the upstream side can be reduced.
Can be kept relatively small even during low-load operation.

Further, since the temperature of the circulated high-pressure water 41 is sufficiently high, if the high-pressure water 41 is circulated by opening the on-off valve 49 when the normal operation state is shifted to the low-load operation state, the low-pressure gas cooler 16 The temperature of the low-temperature portion can be raised with good responsiveness.

FIG. 2 shows another embodiment of the present invention.
A part of the high-temperature high-pressure water supply 41 is guided from the outlet of the second-stage high-pressure gas cooler 15 to the low-pressure gas cooler 1 through the return passage 48.
6 is provided so as to circulate at the inlet of FIG. 6, and FIG. 3 shows still another embodiment of the present invention.
8 is provided so that a part of the high-temperature high-pressure water supply 41 is guided from the outlet of the first-stage high-pressure gas cooler 14 and circulated to the inlet of the low-pressure gas cooler 16.

In short, the return channel 48 of FIG.
2 can guide the high-temperature supply water 41 having a higher temperature on the downstream side to the inlet of the low-pressure gas cooler 16 than the return flow path 48 in FIG. 4
8 can guide the high-pressure feedwater 41 having a higher temperature further downstream to the inlet of the low-pressure gas cooler 16. The higher the temperature of the high-pressure feedwater 41 returned to the inlet of the low-pressure gas cooler 16, the lower the circulation flow rate becomes. Therefore, it is possible to further reduce the water pressure difference between the low-pressure gas cooler 16 during the normal operation and the low-load operation, thereby further suppressing the power of the upstream condensate pump 30 at the time of low load. can do.

However, the high-pressure water 41, which has finished flowing to the downstream side of the high-pressure water supply system 40, is supplied to the low-pressure gas cooler 16 on the upstream side.
Returning to the inlet of the high pressure feed water 41 also increases the transport loss of the high pressure feed water 41, and the high pressure feed water 41
Therefore, the transport loss of the high-pressure water supply 41 is minimized by taking into account the arrangement of various devices in the actual water supply equipment, and the high-pressure water supply 41 is heated as high as possible. It is preferable to connect a suitable position in the high-pressure water supply system 40 and an inlet of the low-pressure gas cooler 16 by a return flow path 48 such that the flow path 48 can be derived.

The water supply equipment of the pressurized fluidized-bed boiler of the present invention is not limited to the above-described embodiment, but shows an example in which two high-pressure gas coolers are provided. Needless to say, the number of stages may be three or more, and various changes may be made without departing from the spirit of the present invention.

[0029]

According to the water supply system for a pressurized fluidized-bed boiler of the present invention, various excellent effects as described below can be obtained.

(I) A part of the high-pressure high-pressure water is guided from an appropriate position after the booster pump of the high-pressure water supply system and circulated to the inlet of the low-pressure gas cooler, whereby the temperature of the supply water to the low-pressure gas cooler is raised, and the low-pressure gas cooler is cooled. Can be maintained at a temperature equal to or higher than the dew point of the acid component in the combustion exhaust gas, so that the acid component in the combustion exhaust gas can be prevented from condensing on the low-temperature portion of the low-pressure gas cooler during low-load operation. Problems such as corrosion of the heat transfer tube or adhesion of combustion ash due to the condensed acid component acting as a binder can be prevented beforehand.

(II) Since the pressure after the booster pump in the high-pressure water supply system is high, a part of the high-temperature high-pressure water supply can be obtained by simply opening the on-off valve provided in the return flow path without using a circulation pump or the like to increase the pressure. Can be circulated to the inlet of the low-pressure gas cooler, equipment costs can be kept low, and
The power cost for circulating the low-pressure supply water at the low-pressure gas cooler outlet, which was conventionally required, can be eliminated.

(III) The high-pressure water supplied from the high-pressure water supply system is sufficiently heated and heated more than the low-pressure water that has been conventionally circulated by the circulation pump, and has a smaller amount of high-pressure water than the conventional low-pressure water. Since it is only necessary to circulate the water supply, the pressure difference between the low-pressure gas cooler and the low-pressure gas cooler during normal operation and low-load operation can be reduced. It is possible to keep it small.

(IV) Since the temperature of the circulated high-pressure water is sufficiently high, if the high-pressure water is circulated by opening the on-off valve at the time of transition from the normal operation state to the low-load operation state, the low-temperature part of the low-pressure gas cooler can be cooled. The temperature can be increased with good responsiveness.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of an embodiment for implementing the present invention.

FIG. 2 is a system diagram showing another embodiment of the present invention.

FIG. 3 is a system diagram showing still another embodiment of the present invention.

FIG. 4 is a system diagram showing a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pressure vessel 2 fluidized-bed boiler main body 8 in-layer evaporator 14 high-pressure gas cooler 15 high-pressure gas cooler 16 low-pressure gas cooler 25 main steam 27 condenser 36 deaerator 38 booster pump 39 water supply pump 40 high-pressure water supply system 41 high-pressure water supply 48 return flow path 49 On-off valve

Claims (3)

[Claims] 1. A main steam is taken out from an in-layer evaporator of a fluidized-bed boiler main body provided in a pressure vessel, and after work is performed, water is condensed by a condenser, and a low-pressure gas cooler, a deaerator, and a booster are provided. In a water supply system of a pressurized fluidized-bed boiler that is circulated to the in-layer evaporator by sequentially passing through a pump, a water supply pump, and a high-pressure gas cooler, in a high-pressure water supply system from the deaerator to the in-layer evaporator. A pressurized flow characterized by providing a return flow path that guides a portion of the high-temperature high-pressure feed water from an appropriate position after the booster pump and circulates at the inlet of the low-pressure gas cooler, and that an on-off valve is disposed in the return flow path. Water supply equipment for layer boiler. 2. The pressurizing method according to claim 1, wherein the return flow path is provided so as to guide a part of the high-temperature high-pressure feed water from the outlet of the booster pump and circulate to the low-pressure gas cooler. Fluidized bed boiler water supply equipment. 3. The return flow passage is provided so as to guide a part of the high-temperature high-pressure feed water from the outlet of the high-pressure gas cooler and circulate to the inlet of the low-pressure gas cooler.
2. A water supply system for a pressurized fluidized-bed boiler according to item 1.