Desalination apparatus and method of operating the same

Distillation: processes – separatory – Water purification only – Under pressure or vacuum

Reexamination Certificate

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C159S046000, C159S901000, C159S903000, C159S047100, C159SDIG001, C202S173000, C202S186000, C202S205000, C202S234000, C203S049000, C203S073000, C203S087000, C203SDIG001, C203S100000, C126S569000

Reexamination Certificate

active

06391162

ABSTRACT:

TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
The present invention relates to a desalination apparatus that obtains fresh water from raw water, e.g. sea water, ground water (brine) containing salt, or industrial waste water, by a distillation method utilizing solar energy, and also relates to a method of operating the desalination apparatus.
CONVENTIONAL TECHNIQUE
Recently, great interest has been focused on the technique of desalinating sea water by utilizing solar energy.
FIG. 17
is a schematic sectional view of a conventional desalination apparatus utilizing solar energy, which is known as “basin type solar heat distiller”. The desalination apparatus in
FIG. 17
has a basin
102
for holding raw water
101
, e.g. sea water, and an air shield
103
that covers the basin
102
and is permeable to solar energy
104
. The outer surface of the air shield
103
is used as a radiating part
106
. In the desalination apparatus in
FIG. 17
, the raw water
101
in the basin
102
is heated with solar energy
104
to generate water vapor
105
. The water vapor
105
is cooled and condensed on the inner surface of the air shield
103
, and thus distilled water
107
is obtained.
Solar energy (sunlight) is a massive energy source in terms of quantity. However, the energy density of sunlight is extremely low, i.e. 1 kw/m
2
at most, and it varies considerably according to hours and seasons. For these reasons, solar energy cannot be applied to industrial techniques that require stable high-density energy. Desalination apparatuses utilizing solar energy, which have been proposed or developed so far, including the above-described basin type solar heat distiller, suffer low efficiency and are inferior in durability. Therefore, the conventional desalination apparatuses are not suitable for practical application.
PROBLEMS THAT THE INVENTION IS TO SOLVE
The present invention was made in view of the above-described problems, and it is an object of the present invention to provide a desalination apparatus utilizing solar energy that is capable of obtaining fresh water from raw water by satisfactorily grasping the characteristics of solar energy and effectively utilizing it, and also provide a method of operating the desalination apparatus. A particular object of the present invention is to provide a desalination apparatus capable of obtaining a large amount of distilled water at low temperature by utilizing a depressurized condition. Another object of the present invention is to increase the useful life of a solar heat collector by using a circulating heating medium. A further object of the present invention is to provide a multiple-effect desalination apparatus having a combination of evaporation cans and condensers, which can utilize with high efficiency thermal energy obtained in a solar heat collector. A still further object of the present invention is to provide a desalination apparatus that consumes very little power so that it can be driven by electric power from a solar battery. A still further object of the present invention is to make the structure of a multiple-effect desalination apparatus compact in size and simplified. In addition, an object of the present invention is to provide a simplified method of operating a multiple-effect desalination apparatus with high efficiency. Other objects and advantages of the present invention will be made apparent from the following description of embodiments, taken in connection with the drawings, and in the appended claims.
MEANS FOR SOLVING THE PROBLEMS
A desalination apparatus according to the present invention has a solar heat collector for heating a heating medium with solar energy, a heat exchanger cooperating with an evaporation can so as to subject the heating medium and raw water in the evaporation can to heat exchange and generate water vapor in the evaporation can, a condenser cooperating with a raw water tank so as to receive the water vapor from the evaporation can, cool the water vapor by subjecting the water vapor and raw water in the raw water tank to heat exchange and obtain distilled water, a distilled water tank for storing distilled water, vacuum means for evacuating the evaporation can and depressurizing the inside of the evaporation can so as to promote generation of water vapor in the evaporation can, and raw water supply means for supplying raw water to the evaporation can. The vacuum means depressurizes the inside of the evaporation can, a condensation space communicated with the inside of the evaporation can, a distilled water storing space, etc.
The desalination apparatus according to the present invention preferably has a plurality of evaporation cans arranged in series, i.e. in a multiple-effect relation to each other, and a condenser cooperating with the evaporation cans. In this case, the heat exchanger is arranged to cooperate with a first evaporation can so as to generate water vapor in the first evaporation can, and the condenser cooperating with the raw water tank is arranged to receive water vapor from a final evaporation can. The condenser cooperating with the evaporation cans receives water vapor from the upstream-side evaporation can, cool the water vapor with raw water in the downstream-side evaporation can and thereby produce distilled water, and also heat the raw water in the downstream-side evaporation can and generate water vapor.
More specifically, in a case where two evaporation cans arranged in series are used, the heat exchanger cooperates with the upstream-side evaporation can to generate water vapor in the upstream-side evaporation can. The condenser cooperating with the raw water tank is arranged to receive water vapor from the downstream-side evaporation can, cool the water vapor with raw water in the raw water tank and thereby produce distilled water. The condenser cooperating with the evaporation cans is disposed so as to receive water vapor from the upstream-side evaporation can, cool the water vapor with raw water in the downstream-side evaporation can and thereby produce distilled water, and also heat the raw water in the downstream-side evaporation can and generate water vapor.
In a case where three evaporation cans, i.e. a first, second and third evaporation cans, are used in series, two pairs of upstream- and downstream-side evaporation cans are formed, and two condensers cooperating with the evaporation cans are used. More specifically, the heat exchanger cooperates with the first evaporation can, and the condenser cooperating with the raw water tank is arranged to receive water vapor from the third evaporation can, cool the water vapor with raw water in the raw water tank and thereby produce distilled water. One of the condensers cooperating with the evaporation cans is disposed so as to receive water vapor from the first evaporation can, cool the water vapor with raw water in the second evaporation can and thereby produce distilled water, and also heat the raw water in the second evaporation can and generate water vapor. The other of the condensers cooperating with the evaporation cans is disposed so as to receive water vapor from the second evaporation can, cool the water vapor with raw water in the third evaporation can and thereby produce distilled water, and also heat the raw water in the third evaporation can and generate water vapor. In a case where N evaporation cans (N is an integer of 4 or higher) are used in series, N−1 pairs of upstream- and downstream-side evaporation cans are formed, and N−1 condensers are used to cooperate with the evaporation cans.
The desalination apparatus according to the present invention preferably has the following arrangements. (a) The heating medium is circulated by the action of thermosiphon in which the heating medium is heated in the solar heat collector to form vapor, which is then cooled to become liquid in the first evaporation can. (b) The heating medium is water. (c) The desalination apparatus has an air shield that covers the raw water tank, the air shield having a structure in which the inner surface of the air shield

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