Distillation: apparatus – Apparatus – Systems
Patent
1987-02-10
1989-04-04
Bascomb, Wilbur
Distillation: apparatus
Apparatus
Systems
2022671, 159DIG27, 203 10, 203 86, 203 99, 203DIG17, 210640, B01D 1300, B01D 5322, C02F 104
Patent
active
048183458
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a distillation apparatus primarily intended for desalinating or de-salting sea water. The distillation apparatus according to the invention is more specifically a membrane distillation apparatus.
In Swedish Patent Specification No. 419 699 there is described an apparatus for membrane distillation which comprises a plurality of first cassettes intended for conducting warm salt water, and a plurality of second cassettes intended for conducting a cold liquid, such as cold salt water. A separation cassette effective for separating one of the first cassettes from one of the second cassettes is provided between two mutually adjacent cassettes.
The separation cassette of the aforementioned Patent Specification includes a hydrophobic porous membrane which constitutes the one side surface of the cassette and a thin plastic film which constitutes the other side surface of the cassette, the membrane being arranged at a distance from the plastic film so as to form an air gap between the membrane and said film. Warm salt water flows into one of the first cassettes from the side of the membrane remote from the air gap, while cold water flows into one of the other cassettes from the side of the plastic film remote from said air gap.
During a distillation process the warm salt water gives off water vapour, or steam, which passes through the pores of the membrane and through the air gap, whereafter the water vapour condenses on the cold plastic film. The pore size is such as to prevent liquid water from passing through the membrane.
A problem of long standing with an arrangement constructed in accordance with the aforesaid Patent Specification is one of achieving a high capacity. The high quantities of energy consumed also constitute a problem.
The present invention relates to an embodiment of a distillation apparatus of the kind described in the aforesaid Patent Specification, with which, in accordance with the invention, a high capacity can be achieved in relation to the available membrane surface, with relatively low energy consumption.
Accordingly, the present invention relates to a distillation apparatus intended for distilling liquid, primarily water, comprising a distillation unit which includes a porous hydrophobic membrane which is permeable to steam or vapour but impermeable to liquid, and further includes a condensation surface spaced from the membrane, and in which apparatus an air gap is located between the membrane and the condensation surface, said distillation apparatus further including units for conducting liquid to be distilled on the membrane surface remote from the air gap, and a unit arranged to conduct liquid, which is colder than the first mentioned liquid, on the side of the condensation surface remote from the air gap, the apparatus being characterized in that the distance between the membrane and the condensation surface lies in the range of about 0.2 mm to about 1 mm; and in that the thickness of the membrane is smaller than about 0.5 mm.
An embodiment of the invention will now be described in more detail with reference to the accompanying drawings and also with reference to a number of graphs, where
FIG. 1 is a schematic vertical cross-sectional view of a separation cassette;
FIG. 2 is an enlarged schematic view of a membrane and a plastic film;
FIGS. 3-7 are various graphs constructed in accordance with an arithmetic model hereinafter described;
FIG. 8 is a part sectional view of a membrane provided with a carrier; and
FIG. 9 is a partial plan view of a membrane seen from the left in FIG. 8.
FIG. 1 is a schematic cross-sectional view of a distillation unit 1 incorporating a porous hydrophobic membrane 2 through which steam or vapour can pass, but which prevents the passage of liquid, and further incorporates a condensation surface formed by a plastic film 3 located at a distance from the membrane. Arranged between the membrane 2 and the plastic film 3 is an air gap 4, which is provided with a channel 5 or the like for supplying the air required as illustrated b
REFERENCES:
patent: 3266223 (1966-08-01), Dresser et al.
patent: 3563860 (1971-02-01), Henderyckx
patent: 3878054 (1975-04-01), Rodgers
patent: 4391676 (1983-07-01), Torberger
patent: 4545862 (1985-10-01), Gore et al.
patent: 4620900 (1986-11-01), Kimura et al.
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