Distillation: processes – separatory – Water purification only
Patent
1981-05-17
1982-09-21
Bascomb, Jr., Wilbur L.
Distillation: processes, separatory
Water purification only
203 49, 203 86, 203 90, 202176, 202234, 202185B, C02F 110
Patent
active
043505708
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the art of water treatment, and more particularly to methods of desalinating water, such as sea or saline continental water.
PRIOR ART
Known in the art is a method of desalinating water wherein water is evaporated from an aqueous salt solution when the latter is made to come into contact with air and subsequently retrieved from the thus moisened air by condensation (cf. V. N. Slesarenko "Sovremennye metody opresnenia morskikh i solenykh vod--Modern Techniques for Desalination of Sea and Saline Waters" published in 1973 by the Energia Publishers, Moscow, pp, 47-48).
However, in this known method, a large amount of costly high-calorie heat energy is required to conduct the process (around 600 kcal/kg under atmospheric pressure, which corresponds to approximately 695 watts per 1 kg of desalinated water).
SUMMARY OF THE INVENTION
The invention is directed toward a method of desalinating water involving the evaporation of water from an aqueous salt solution upon contact with air and subsequent recovery of the water vapor from the air by condensation, wherein it would be possible to change the conditions for evaporation and condensation to obviate the need for energy to carry out the water evaporating process.
This is attained in a method of desalinating water wherein the evaporation of water from the aqueous salt solution upon contact of the solution with the air is conducted by using primary and secondary air flows, the primary air flow being supplied to a cooling zone, while the secondary air flow and the aqueous salt solution are supplied to an evaporation zone wherein the secondary air flow is moistened by the water being evaporated from the aqueous salt solution by virtue of the psychrometric temperature difference until the moisture content in said secondary air flow is raised as compared with the initial moisture content by from 3.5 to 116 g/kg. Meanwhile the secondary air flow while being moistened, tends to cool the primary air flow passing through the cooling zone, said secondary air flow being obtained by withdrawing some 20 to 90 volume percent from the primary air flow which has passed through the cooling zone. The condensation of the water vapor is effected by conveying the secondary air flows which has passed through the evaporation zone and the remaining 80 to 10 volume percent of the primary air flow which has passed through the cooling zones to a condensing zone.
The process of vaporizing water from the aqueous salt solution by contacting the salt with air and condensing the water vapor as heretofore described, makes it possible to vaporize the water contained in the aqueous salt solution without an external energy source as is the case with the known method, but due to the psychrometric temperature difference. Also, by imparting moisture to the secondary air flow in the evaporation zone, the latent heat of evaporation is removed from the secondary air flow. Further, thanks to the heat transfer between the secondary air flow and the primary air flow, the latter and the former are cooled and heated in the cooling zone and the evaporation zone, respectively. Consequently, two interrelated processes necessary for water desalination are carried out, the processes being
(1) imparting moisture to the secondary air flow by the water vapor, and
(2) cooling the primary air flow; said processes are conducted without any external heat energy being supplied.
Since the secondary air flow is produced by withdrawing a portion (20 to 90% by volume) of the cooled primary air flow, it is possible to effectively reduce the temperature of the primary air flow subsequent to its passage through the cooling zone to that approaching the dew point. Therefore, the temperature of the primary air flow at the outlet from the cooling zone is always sufficiently low to guarantee condensation of water vapor from the secondary air flow which has passed the evaporation zone.
Having in view the foregoing, moistened air and cool dry air are obtained with no outside h
REFERENCES:
patent: 2902414 (1959-09-01), Schmerzler
patent: 3345272 (1967-10-01), Collins
patent: 3522151 (1970-07-01), Dismore
patent: 3822192 (1974-07-01), Brown
patent: 3852162 (1974-12-01), Light
patent: 3860492 (1975-01-01), Lowi et al.
patent: 4194950 (1980-03-01), Zalles
Maisotsenko Valery S.
Tsimerman Alexandr B.
Zexer Mikhail G.
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