JPH11211008A - Flushing water supply device for pump mechanical seal - Google Patents

Abstract

(57) Abstract: A flushing water supply device for a pump mechanical seal portion that does not damage a mechanical seal portion mounted on a pump shaft. A flushing water supply device for a pump mechanical seal unit according to the present invention includes a mechanical seal unit (38).
The flushing water supply system 36 bypassed from the low pressure water supply system 30 of the exhaust heat recovery boiler was provided at a and 38b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flushing water supply device for a pump mechanical seal unit that uses purified water as flushing water supplied to the pump mechanical seal unit.

[0002]

2. Description of the Related Art For example, in a recent thermal power plant,
Combined cycle power plants with higher plant thermal efficiency are becoming more prevalent than conventional power plants that combine a steam turbine plant with a boiler.

[0003] This combined cycle power plant is a combination of a gas turbine plant with a steam turbine plant and an exhaust heat recovery boiler. The exhaust heat recovery boiler uses exhaust gas (exhaust heat) from the gas turbine plant that has completed expansion work as a heating source. To generate steam, and the steam drives a steam turbine plant to generate electric power.
The fact that the exhaust gas of a gas turbine plant is used as a heating source for generating steam from an exhaust heat recovery boiler makes the plant thermal efficiency higher than that of a conventional power generation plant.

An exhaust heat recovery boiler that generates steam by using exhaust gas of a gas turbine plant as a heating source has a configuration shown in FIG. 8 as an example.

[0005] The exhaust heat recovery boiler comprises a cylindrical casing 1 extending in the axial direction, and a high-pressure steam drum is sequentially arranged in the casing 1 along the flow of exhaust gas G supplied from a gas turbine plant (not shown). And a high-pressure secondary economizer 3, a high-pressure primary economizer 4, a medium-pressure economizer 6 with an intermediate-pressure steam drum 5, a low-pressure economizer 8 with a low-pressure drum 7, and the like. .

The exhaust heat recovery boiler has a low-pressure water supply system 10 that guides water supplied from a steam turbine plant (not shown) to a low-pressure economizer 8 through a low-pressure water supply pump 9. A high-pressure water supply system 12 is connected from the outlet side of the low-pressure economizer 8 to one side through a high-pressure water-supply pump 11 and connected to the high-pressure primary economizer 4, and the other is an intermediate-pressure water-supply pump 13. And an intermediate-pressure water supply system 14 connected to the intermediate-pressure economizer 6.

The high-pressure water supply pump 11 provided in the high-pressure water supply system 12 accommodates multi-stage impellers, and has a middle-stage water supply system 15 that supplies water supplied from the middle stage to the low-pressure water supply system 10. I have.

In the exhaust heat recovery boiler having such a configuration, the low-temperature water supplied from the low-pressure water supply system 10 is supplied to the low-pressure fuel-saving device 8, the medium-pressure fuel-saving device 6, and the high-pressure primary fuel-saving device 4 during startup operation. If supplied to each of them, there is a possibility that dew point corrosion of the heat transfer tube or the like may occur. Therefore, relatively high-temperature hot banking water confined in the low-pressure economizer 8 is supplied to the high-pressure water supply system 12 and the medium-pressure water supply system 14. High pressure primary economizer 4 through each
And the medium-pressure economizer 6, and supplies high-pressure water extracted from the middle stage of the high-pressure water supply pump 11 to the low-pressure water supply system 10 through the middle-stage water extraction system 15, and supplies low-temperature water to the low-pressure water supply system 10. Merge, set to a suitable temperature, and use low-pressure economizer 8
To prevent damage to the heat transfer tubes.

On the other hand, as shown in FIG. 6, a high pressure water supply pump 11 applied to the high pressure water supply system 12 and a medium pressure water supply pump 13 applied to the medium pressure water supply system 14 are provided with a mechanical seal portion 17 on a pump shaft 16. In this mechanical seal part 17,
Relatively high-pressure flushing water (cooling water) extracted from the impeller of the pump itself (usually one or two paragraphs) via the cooling pipe 43 is supplied after being cooled by the cooler 18 interposed in the cooling pipe 43 once. ing.

As another embodiment, as shown in FIG. 7, a high pressure water supply pump 11 and a medium pressure water supply pump 13 are connected to a port 1 of a mechanical seal portion 17 mounted on a pump shaft 16.
A circulation path 20 provided with a cooler 18 is connected to 9 a and 19 b, and flushing water (cooling water) is circulated using the rotational force of the pump shaft 16 to cool the mechanical seal portion 17.

As described above, the high-pressure water supply pump 11 and the medium-pressure water supply pump 13 applied to the exhaust heat recovery boiler handle relatively high-temperature water supply, and the flushing water is supplied to the mechanical seal portion 17 provided on the pump shaft 16. To cool the mechanical seal portion 17 to protect the heat from frictional heat accompanying the rotation of the pump shaft 16, and to suppress the water supply leak from the pump shaft 16.

[0012]

In the conventional mechanical seal portion 17 applied to the high-pressure water supply pump 11 and the medium-pressure water supply pump 13 shown in FIGS. 6 and 7, iron is dissolved in flushing water. There was a problem that the seal was insufficient and the water supply leaked from the pump shaft.

Generally, the high-pressure water supply pump 11 and the medium-pressure water supply pump 13 supply the water whose water quality has been sufficiently controlled to the exhaust heat recovery boiler, so that there is no problem in that respect.

However, when the high-pressure water supply pump 11 and the medium-pressure water supply pump 13 suddenly supply low-temperature water to heat exchangers such as the low-pressure economizer 8, the medium-pressure economizer 6, and the high-pressure primary economizer 4, In consideration of causing dew-point corrosion on the heat transfer tube, relatively high-temperature hot banking water confined in the low-pressure economizer 8 is used during the start-up operation. Iron in the plant is dissolved in the hot banking water.

FIG. 5 is a graph showing the relationship between the temperature of the feed water and the iron dissolved in the feed water.
It is known that at 70 ° C., the solubility of iron is the highest. Hot banking water has the highest iron solubility since it has a water temperature of 150 ° C.

As described above, due to the special circumstances of the exhaust heat recovery boiler, the high-pressure water supply pump 11 and the medium-pressure water supply pump 13 supply the water containing the largest amount of iron to the mechanical seal portion 17 as flushing water. The mechanical seal 17 may be damaged by the iron, or the pump shaft 16 may be damaged.
There is a possibility that the sliding portion may become clogged, the sealing may become insufficient, and the supply water may leak from the pump shaft 16.

The present invention has been made in view of the above circumstances. In a case where a pump uses hot banking water during startup operation and a part of the hot banking water is supplied to a mechanical seal portion as flushing water. It is another object of the present invention to provide a flushing water supply device for a pump mechanical seal unit that removes iron dissolved in hot banking water and supplies the removed water to the mechanical seal unit.

[0018]

According to a first aspect of the present invention, there is provided a flushing water supply device for a pump mechanical seal portion, wherein the mechanical seal portion is mounted on a pump shaft. In the flushing water supply device of the pump mechanical seal unit for supplying flushing water, a flushing water supply system is provided in the mechanical seal unit, the flushing water supply system being bypassed from the low pressure water supply system of the exhaust heat recovery boiler, and the flushing water supplied to the mechanical seal unit is provided. And the purified water supply of the low pressure water supply system.

In order to achieve the above object, the flushing water supply system for a pump mechanical seal according to the present invention is provided with a flushing water supply system provided with a booster pump.

According to a third aspect of the present invention, there is provided a flushing water supply device for supplying a flushing water to a mechanical seal portion mounted on a pump shaft. In the flushing water supply device of the pump mechanical seal part,
A circulation path for circulating flushing water is provided in the mechanical seal portion, and a flushing water supply system bypassing the low pressure water supply system of the exhaust heat recovery boiler is provided in this circulation path, and the low pressure water supply as the flushing water circulating in the circulation path is provided. The system uses purified water supply.

According to a fourth aspect of the present invention, there is provided a flushing water supply device for a pump mechanical seal, wherein a cooler is provided in a circulation path.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a flushing water supply device for a pump mechanical seal according to the present invention will be described below with reference to the drawings and reference numerals in the drawings.

FIG. 1 is a schematic system diagram of an exhaust heat recovery boiler in which a flushing water supply device for a pump mechanical seal according to the present invention is applied to an exhaust heat recovery boiler of a combined cycle power plant as an example.

The exhaust heat recovery boiler is constituted by a cylindrical casing 21 extending in the axial direction. In the casing 21, high-pressure steam is supplied in order from the downstream side of the flow of the exhaust gas G supplied from the gas turbine plant (not shown). High pressure secondary economizer 23 with drum 22, high pressure primary economizer 24, medium pressure drum 25
And a low-pressure economizer 28 equipped with a low-pressure drum 27 and the like.

The exhaust heat recovery boiler is provided with a low-pressure water supply system 30 for guiding water supplied from a steam turbine plant (not shown) to a low-pressure economizer 28 through a low-pressure water pump 29. A high-pressure water supply system 32 is connected from the outlet side of the low-pressure economizer 28, one of which is interposed with a high-pressure water pump 31 and connected to the high-pressure primary economizer 24, and the other is an intermediate-pressure water pump 33. And an intermediate-pressure water supply system 34 connected to the intermediate-pressure economizer 26.

The high-pressure water supply pump 31 provided in the high-pressure water supply system 32 accommodates multi-stage impellers, and has a middle-stage water supply system 35 for supplying water drawn from the middle stage to the low-pressure water supply system 30. ing.

On the other hand, the low-pressure water supply system 30 bypasses the intermediate portion between the outlet side of the low-pressure water supply pump 29 and the connection part of the middle-stage water extraction system 35, and supplies water to the mechanical parts of the high-pressure water supply pump 31 and the medium-pressure water supply pump 33, respectively. A flushing water supply system 36 for supplying flushing water to the seal portion is provided.

As shown in FIG. 2, the flushing water supply system 36 includes a high-pressure water supply pump 31 and a medium-pressure water supply pump 33.
Are connected to the ports 39a, 39b of the mechanical seal portions 38a, 38b mounted on the respective pump shafts 37a, 37b, so that the mechanical seal portions 38a, 38b are cooled by the water supplied from the low-pressure water supply system 30. . When the pressure of the supply water bypassed from the low-pressure water supply system 30 is insufficient, the flushing water supply system 36 may be provided with a booster pump 40 as shown in FIGS. 1 and 3.

As described above, in the present embodiment, the low-pressure water supply system 3
Ports 39 of mechanical seal portions 38a, 38b mounted on the pump shafts 37a, 37b of the high-pressure water supply pump 31 and the medium-pressure water supply pump 33, respectively.
Since the flushing water supply system 36 connected to the a and 39b is provided and the water quality is sufficiently controlled and high-purity water is supplied to the mechanical seal portions 38a and 38b as flushing water, the mechanical seal portions 38a and 38b are damaged. Without causing clogging of the sliding portions of the pump shafts 37a and 37b,
a and 38b can be sufficiently cooled, and the high-pressure water supply pump 31 and the medium-pressure water supply pump 33 can be operated stably.

FIG. 4 is a schematic view showing a modification of the embodiment of the flushing water supply device for the pump mechanical seal portion according to the present invention. The same reference numerals are given to the same components as those of the embodiment shown in FIGS.

In this embodiment, the pump shafts 37a and 37b of the high-pressure water supply pump 31 and the medium-pressure water supply pump 33 are used.
The cooler 4 is connected to the ports 39a ₁ , 39a ₂ , 39b ₁ , 39b ₂ of the mechanical seal portions 38a, 38b mounted on the shaft.
1 is connected to the circulation path 42, and the pump shafts 37a, 3
The flushing water supply system 36 is connected to mechanical seals 38a and 38b that circulate flushing water using the rotational force of 7b.

As described above, in this embodiment, the mechanical seal portions 38a and 38b for circulating flushing water are provided with:
A flushing water supply system 36 is provided, and the supply of the flushing water whose water quality is sufficiently controlled is controlled by the mechanical seal unit 3.
8a and 38b, the high-pressure water supply pump 31 and the medium-pressure water supply pump 33 can be operated stably.

[0033]

As described above, the flushing water supply device for a pump mechanical seal according to the present invention is provided with a flushing water supply system that bypasses the low-pressure water supply system in the mechanical seal mounted on the pump shaft. Water is supplied from the low-pressure water supply system to the mechanical seal as flushing water, and the mechanical seal is cooled, so that the pump can be operated more stably.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing an embodiment in which a flushing water supply device for a pump mechanical seal unit according to the present invention is applied to an exhaust heat recovery boiler of a combined cycle power plant.

FIG. 2 is a schematic partial view for explaining supply of flushing water to a mechanical seal portion applied to the high-pressure water supply pump and the medium-pressure water supply pump in FIG. 1;

FIG. 3 is a schematic partial view for explaining supply of another flushing water to a mechanical seal portion applied to the high-pressure water supply pump and the medium-pressure water supply pump in FIG. 1;

FIG. 4 is a schematic partial view showing a modification of the embodiment in which the flushing water supply device for the pump mechanical seal unit according to the present invention is applied to an exhaust heat recovery boiler of a combined cycle power plant.

FIG. 5 is a diagram showing the relationship between the temperature of the water supply and the iron dissolved in the water supply.

FIG. 6 is a schematic partial view showing a conventional mechanical seal portion.

FIG. 7 is a schematic partial view showing another conventional mechanical seal portion.

FIG. 8 is a schematic system diagram showing a waste heat recovery boiler of a conventional combined cycle power plant.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Casing 2 High-pressure steam drum 3 High-pressure secondary economizer 4 High-pressure primary economizer 5 Medium-pressure drum 6 Medium-pressure economizer 7 Low-pressure steam drum 8 Low-pressure economizer 9 Low-pressure water supply pump 10 Low-pressure water supply system 11 High-pressure water supply pump 12 High-pressure water supply system 13 Medium-pressure water supply pump 14 Medium-pressure water supply system 15 Middle-stage water extraction system 16 Pump shaft 17 Mechanical seal portion 18 Cooler 19a, 19b Port 20 Circulation path 21 Casing 22 High-pressure steam drum 23 High-pressure secondary economizer 24 High-pressure primary economizer Container 25 Medium-pressure drum 26 Medium-pressure economizer 27 Low-pressure steam drum 28 Low-pressure economizer 29 Low-pressure water supply pump 30 Low-pressure water supply system 31 High-pressure water supply pump 32 High-pressure water supply system 33 Medium-pressure water supply pump 34 Medium-pressure water supply system 35 Middle-stage water supply system 36 Flushing water supply system 37a, 37b Pump shaft 38a, 38b Mechanical seal 39a , 39a ₁ , 39a ₂ , 39b, 39b ₁ , 39
b ₂ port 40 Boost pump 41 Cooler 42 Circulation path 43 Cooling pipe

Claims (4)

[Claims] 1. A flushing water supply device for a pump mechanical seal section for supplying flushing water to a mechanical seal section mounted on a pump shaft, wherein the flushing water bypasses the mechanical seal section from a low pressure water supply system of a waste heat recovery boiler. A flushing water supply device for a pump mechanical seal, wherein a supply system is provided. 2. The flushing water supply device for a pump mechanical seal according to claim 1, wherein a boosting pump is interposed in the flushing water supply system. 3. A flushing water supply device for a pump mechanical seal part for supplying flushing water to a mechanical seal part mounted on a pump shaft, wherein a circulation path for circulating the flushing water is provided in the mechanical seal part. A flushing water supply system for a pump mechanical seal, wherein a flushing water supply system is provided which is bypassed from a low pressure water supply system of the exhaust heat recovery boiler. 4. The flushing water supply device for a pump mechanical seal according to claim 3, wherein a cooler is provided in the circulation path.