JPH0952082A - Apparatus for desalinating seawater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain fresh water from seawater by evaporating seawater efficiently and stably utilizing low temperature waste heat. SOLUTION: This seawater desalination apparatus uses hot seawater which is discharged from a condenser 1 of a steam turbine in an LNG thermal electric power station as hot seawater and cold seawater which is discharged from an LNG gasifier 6 of the LNG thermal electric power station as cooling water for the indirect heat exchange in a fresh water condenser.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seawater desalination apparatus for desalinating seawater by an evaporation method for use as industrial water, drinking water and domestic water.

[0002]

2. Description of the Related Art Conventional desalination of seawater includes an evaporation method, a reverse osmosis membrane method, an electrodialysis method and a freezing method. Among them, the multi-stage flash method in the evaporation method will be described with reference to FIG.
The apparatus is composed of a plurality of evaporators 51 to 53. The evaporators are connected in series and are depressurized in sequence.

When seawater flows through the heat transfer tubes of the condensers 54 to 56 of each stage evaporating can, it is preheated by the condensation of the steam generated in the cans, and the heater 5 uses the steam from the boiler as a heat source.
It is heated by 7 and enters the first-stage evaporator 51.

When the pressure inside the evaporator is set to be equal to or lower than the saturated vapor pressure corresponding to the temperature of the heated seawater, the seawater is instantly evaporated. After the second stage, the temperature gradually decreases, but flash evaporation is repeated by increasing the degree of pressure reduction.

[0005]

In the conventional multi-stage flash type, steam from the boiler and a heat source instead of the steam are required to heat the seawater. Even if an attempt is made to use waste heat having a low temperature which has been conventionally discarded as a heat source in order to effectively use energy, an effective amount of evaporation could not be stably obtained.

On the other hand, JP-A-2-214585 discloses a device for obtaining fresh water by spray-flushing relatively high-temperature warm seawater near the sea surface and condensing evaporated water vapor with deep-water relatively low-temperature cold seawater. ing.

However, this has a problem that the temperature that can be expected for seawater near the sea surface is limited, and that considerable energy is required to pump up cold seawater having a relatively low temperature in the deep part.

The present invention has been made in order to solve the above problems, and utilizes waste heat having a low temperature, which has been discarded in the past, to efficiently and stably evaporate the waste water from seawater. The purpose is to obtain fresh water.

[0009]

The seawater desalination apparatus of the present invention is a spray flash type seawater desalination apparatus,
The warm seawater discharged from the condenser of the steam turbine of the LNG thermal power plant is used as the warm seawater, and is discharged from the LNG vaporizer of the LNG thermal power plant as the cooling water for the indirect heat exchange of the freshwater condenser. It is characterized by using cold seawater.

Further, as a fresh water condenser, a first fresh water condenser that uses cold seawater discharged from the LNG vaporizer of an LNG thermal power plant as cooling water, and a first fresh water condenser that cools steam by indirect heat exchange with the atmosphere. Two fresh water condensers are provided in parallel, and these two fresh water condensers can be switched.

As cooling water supply means for indirect heat exchange of the fresh water condenser, first cooling water supply means for supplying cold seawater discharged from the LNG vaporizer of the LNG thermal power plant, and a cooling tower. It is characterized in that a second cooling water supply means for supplying the cold water cooled by is provided in parallel, and these two cooling water supply means can be switched.

The warm seawater discharged from the condenser of the steam turbine is spray-injected in the depressurized flasher, and the temperature drops and at the same time part of it evaporates. The vaporized vapor is cooled in the condenser by the cold seawater discharged from the LNG vaporizer, and can be condensed to obtain fresh water. When there is a cold atmosphere in winter, the cold atmosphere is used to cool and condense. When colder cold water is obtained by the cooling tower in winter, it is condensed as cooling water.

[0013]

FIG. 1 shows a first embodiment of the present invention.
It is a whole block diagram which shows the example of. The seawater that has risen in temperature after leaving the steam turbine condenser 1 is led to the depressurized flasher 2 as the supply seawater for desalination. The seawater guided to the flasher 2 is sprayed from the nozzle 3 arranged in the flasher 2. Part of the sprayed seawater evaporates as the temperature drops. The seawater that has not evaporated is discharged to the outside of the flasher 2.

The vaporized vapor passes through the separator 4 and flows into the condenser 5. The inflowing steam is LNG in the condenser 5.
It is cooled by the seawater whose temperature has dropped after leaving the vaporizer 6, and is condensed into fresh water.

The vacuum pump 7 discharges the non-condensing gas remaining when the vapor is condensed to the outside of the system so that the condensing temperature and pressure do not rise due to the non-condensing gas. The fresh water obtained is
After being stored in the fresh water tank 8, it is sent to a necessary place by the fresh water pump 9.

Next, a second example will be described with reference to FIG. This is because when the atmospheric temperature decreases in winter,
An example is shown in which the vapor evaporated by the flasher 2 is cooled in the atmosphere using an air-cooled condenser 10 and condensed.

For that reason, the steam leaving the separator 4 is
It is introduced to the air-cooled condenser 10 through the valve 11 or the valve 12
So as to flow into the condenser 5 as in the case of FIG.
It can be switched by the valves 11 and 12.

That is, a first fresh water condenser that uses cold seawater discharged from the LNG vaporizer as cooling water and a second fresh water condenser that cools steam by indirect heat exchange with the atmosphere are provided in parallel. It is possible to switch between these two fresh water condensers.

By using this method, a part of the heat quantity of the warm seawater that has left the steam turbine condenser 1 is released to the atmosphere via the air-cooled condenser 10. Therefore, the temperature of the warm seawater is lowered, and as a result, the temperature rise of the wastewater discharged to the sea can be suppressed to a low level.

The valve 11 is used except in winter when the atmospheric temperature is low.
By closing the valve and opening the valve 12, the same operation as in the case of FIG. 1 can be performed. Next, a third example will be described with reference to FIG.

This is because the vapor evaporated in the flasher 2 is cooled by the cooling tower 10 when the atmospheric temperature is lowered in winter.
An example in which the cold water cooled in a is supplied to the condenser 5 by the circulation pump 16 and condensed is shown.

That is, the valves 23 and 24 are opened, and the cooling tower 10
A loop for supplying the cold water cooled in a to the condenser 5 by the circulation pump 16 is formed to form the second cooling water supply means. In this case, the valves 22 and 25 are closed, the valve 21 is opened, and the seawater leaving the LNG vaporizer 6 is discharged as it is.

On the other hand, the valve 2 is used except in winter when the atmospheric temperature is low.
By closing 1, 23 and 24 and opening the valves 22 and 25, a first cooling water supply means for supplying the cold seawater discharged from the LNG vaporizer is formed.
In this case, the same operation as in the case of FIG. 1 can be performed.

In this way, the first and second cooling water supply means are provided in parallel, and these two cooling water supply means are switchable. Also in this case, as in the case of the second example in FIG. 2, it has the effect of suppressing the temperature rise of the wastewater discharged to the sea to a low level. In addition, as compared with the second example of FIG. 2, since the condensation temperature is higher, the evaporation amount is smaller,
Condensation performance is improved and the condenser becomes smaller.

[0025]

As described above, according to the present invention, the warm seawater after exiting the steam turbine condenser is used as a heating source for the LN.
Since cold seawater after leaving the G vaporizer was used as a cold heat source and a seawater desalination device by spray flash was constructed, waste heat that was conventionally discarded can be effectively used, and cheap fresh water can be obtained. effective.

Furthermore, by using a method of cooling the evaporated vapor by the atmosphere and condensing it in the winter, the temperature rise of the seawater discharged to the sea can be suppressed to a low level, and the effect on the surrounding environment can be reduced. There is.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a first example of the present invention.

FIG. 2 is an explanatory diagram showing an overall configuration of a second example of the present invention.

FIG. 3 is an explanatory diagram showing an overall configuration of a third example of the present invention.

FIG. 4 is an explanatory diagram of a conventional multi-stage flash evaporation method.

[Explanation of symbols]

1 ... Steam turbine condenser, 5 ... Fresh water condenser, 6 ... LN
G vaporizer, 10 ... Air-cooled condenser, 10a ... Cooling tower.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Kitano 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Haracho Kubota 25 Shintomi, Futtsu, Chiba TEPCO Inside Futtsu Thermal Power Station

Claims (3)

[Claims] 1. A spray flash type evaporator that evaporates a part of hot seawater by injecting the hot seawater into a depressurized container through a nozzle, and vapor generated in the evaporator to the outside of the evaporator. In a seawater desalination apparatus including a lead steam pipe and a steam introduced through the steam pipe, by cooling by indirect heat exchange to obtain fresh water by condensing, as the warm sea water. , Warm sea water discharged from the condenser of the steam turbine of the LNG thermal power plant, and cold sea water discharged from the LNG vaporizer of the LNG thermal power plant as cooling water for indirect heat exchange of the fresh water condenser A seawater desalination apparatus characterized by using. 2. A first fresh water condenser that uses cold seawater discharged from an LNG vaporizer of an LNG thermal power plant as cooling water as a fresh water condenser, and a steam that cools steam by indirect heat exchange with the atmosphere. The seawater desalination apparatus according to claim 1, wherein the two freshwater condensers are provided in parallel, and these two freshwater condensers can be switched. 3. A first cooling water supply means for supplying cold seawater discharged from an LNG vaporizer of an LNG thermal power plant as a cooling water supply means for indirect heat exchange of a fresh water condenser, and a cooling tower. The seawater desalination apparatus according to claim 1, wherein a second cooling water supply means for supplying the cold water cooled in (1) is provided in parallel, and these two cooling water supply means can be switched.