Desalination device and process

Energy efficient apparatus for the continuous distillation of a feed of hot aqueous liquid containing a low volatility solute such as salt comprising:

• a thermally conductive, water vapor impermeable sheet forming one longitudinal wall of a distillation collecting chamber;
• a hydrophobic microporous membrane forming an opposing longitudinal wall of said chamber;
• means for rapidly flowing the hot aqueous feed past, and in intimate contact with, the surface of said microporous membrane opposite the distillate collecting chamber, water vapor from the hot feed diffusing through said microporous membrane into said distillate collecting chamber;
• means for cooling the surface of said impermeable sheet opposite the distillate collecting chamber, the cooled sheet causing condensation of the diffused water vapor in the collecting chamber, the condensed distillate film being in intimate contact with both said sheet and said membrane, said cooling means including
• (a) means for flowing past said impermeable sheet cold aqueous feed at a temperature lower than that of the hot feed flowing past said membrane, the direction of flow of said cold feed being counter to that of the hot feed, and
• (b) means for recovering the latent heat of the condensing distillate absorbed by said cold feed;
• and
• means for stripping condensed distillate from said distillate collecting chamber, said stripping means including
• (a) means using forces exerted by the rapidly flowing hot flowing feed acting across said microporous membrane on the distillate sandwiched between said porous membrane and said impermeable sheet for causing distillate flow in the direction of hot feed flow, wherein said distillate forcing means includes means for stiffening each impermeable sheet against deformation in the direction normal to its surface relative to the respective microporous membrane, said more stiff impermeable sheet and said less stiff microporous membrane being positioned in surface-contacting relationship when no liquid distillate is present in said collecting chamber, said less stiff microporous membrane being locally deformable away from said more stiff impermeable sheet during distillation operation by forces induced by the flowing hot feed to allow passage of liquid distillate, and
• (b) means for draining the distillate from the collecting chamber along the direction of hot feed flow, said stripping means preventing thick layers of distillate from forming in said distillate collecting chamber and allowing said distillate to give up its sensible heat to said cold feed.

Apparatus for the distillation of a hot feed of an aqueous liquid containing a low volatility solute such as salt comprising:

• first and second thermally conductive, water vapor impermeable sheets positioned in spaced side-by-side relationship;
• first and second microporous membranes positioned in spaced side-by-side relationship between said impermeable sheets, each of said microporous membranes together with the proximate respective impermeable sheet forming opposing longitudinal walls of first and second distillate collection chambers;
• means for flowing the hot feed between and in intimate contact with said first and second microporous membranes, water vapor from the hot feed diffusing through said membranes into the respective collecting chambers;
• means for cooling said first and second impermeable sheets, said cooled sheets causing the diffused vapor to condense and collect in the respective collecting chambers, the condensed distillate being intimately in contact with the both the membrane and the sheet forming the respective collecting chamber;
• and
• means for stripping the condensed distillate from said collecting chambers, said stripping means including
• (a) means using forces exerted by the hot flowing feed acting across said first and second microporous membranes on the distillate sandwiched between each of said first and second microporous membranes and the respective one of said first and second impermeable sheets for causing distillate flow in the direction of the hot feed flow, wherein said distillate forcing means includes means for stiffening each impermeable sheet against deformation in the direction normal to its surface relative to the respective microporous membrane, said more stiff impermeable sheet and said less stiff microporous membrane being positioned in surface-contacting relationship when no liquid distillate is present in said collecting chamber, each of said less stiff microporous membranes being locally deformable away from said respective more stiff impermeable sheet during distillation operation by forces induced by the flowing hot feed to allow passage of liquid distillate, and
• (b) means for draining the distillate from the collecting chambers along the direction of hot feed flow.

Apparatus for the distillation of a hot feed of an aqueous liquid containing a low volatility solute such as salt comprising:

• first and second thermally conductive, water vapor impermeable sheets positioned in spaced side-by-side relationship;
• first and second microporous membranes positioned in spaced side-by-side relationship between said impermeable sheets, each of said microporous membranes together with the proximate one of said impermeable sheets forming a respective distillate collecting chamber;
• means for flowing the hot feed between and in intimate contact with both said first and second microporous membranes, water vapor from the hot feed diffusing through said membranes into the respective collecting chambers;
• spacer means for separating said first and second microporous membranes and for promoting turbulence and mixing in said hot feed flowing therebetween;
• means for cooling said first and second impermeable sheets, said cooled sheets causing the diffused vapor to condense and collect in the respective collecting chambers, the condensed distillate being intimately contacted by both the membrane and the sheet forming the respective collecting chamber;
• and
• means for stripping the condensed distillate from said collecting chambers, said stripping means including
• (a) means using forces exerted by the flowing hot feed acting across said first and second microporous membranes on the distillate sandwiched between each of said first and second microporous membranes and the respective one of said first and second impermeable sheets for causing distillate flow in the direction of the hot feed flow, wherein a pressure gradient is maintained in the hot feed flow between said membranes with the static pressure decreasing along the direction of hot feed flow, and
• (b) means for draining the distillate from the collecting chamber along the direction of hot feed flow, wherein said spacer means includes a plurality of first ribs extending longitudinally in the feed flow direction;
• and a plurality of second ribs extending transversely to the feed flow direction and attached to, and transversely spacing, said first ribs, said first ribs being sized and configured to provide the required separation, and said second ribs being sized and configured to provide turbulence and to mix the feed flowing past said second ribs.

Apparatus for the distillation of a hot feed of an aqueous liquid containing a low volatility solute such as salt comprising:

• first and second thermally conductive, water vapor impermeable sheets positioned in spaced side-by-side relationship;
• first and second microporous membranes positioned in spaced side-by-side relationship between said impermeable sheets, each of said microporous membranes together with the proximate one of said impermeable sheets forming a respective distillate collecting chamber;
• means for flowing the hot feed between and in intimate contact with both said first and second microporous membranes, water vapor from the hot feed diffusing through said membranes into the respective collecting chambers;
• spacer means for separating said first and second microporous membranes and for promoting turbulence and mixing in said hot feed flowing therebetween;
• means for cooling said first and second impermeable sheets, said cooled sheets causing the diffused vapor to condense and collect in the respective collecting chambers, the condensed distillate being intimately contacted by both the membrane and the sheet forming the respective collecting chamber;
• and
• means for stripping the condensed distillate from said collecting chambers, said stripping means including
• (a) means using forces exerted by the flowing hot feed acting across said first and second microporous membranes on the distillate sandwiched between each of said first and second microporous membranes and the respective one of said first and second impermeable sheets for causing distillate flow in the direction of the hot feed flow, wherein a pressure gradient is maintained in the hot feed flow between said membranes with the static pressure decreasing along the direction of hot feed flow, and
• (b) means for draining the distillate from the collecting chamber along the direction of hot feed flow,
• wherein said spacer means also contacts and separates said first and second impermeable sheets through the respective microporous membranes, said spacer means contacting said impermeable sheets intermittently in the transverse direction.

Method of continuously distilling a hot aqueous feed containing a low volatility solute such as salt comprising the steps of:

• (a) flowing the hot feed past, and in intimate contact with, one side of a microporous membrane;
• (b) diffusing water vapor through the membrane;
• (c) condensing the diffused water vapor using an impermeable sheet positioned on the side of the microporous membrane opposite the hot feed, the condensing step including the steps of collecting the condensed vapor in the chamber defined in part by the microporous membrane and the impermeable sheet, and intimately contacting both the membrane and the sheet with the collected distillate;
• (d) stripping the condensed and collected distillate from the chamber using forces exerted by the hot flowing feed flow acting across the microporous membrane on the distillate sandwiched between the membrane and the sheet, the forces causing distillate flow in the same direction as hot feed flow, said stripping step including the step of locally deforming the microporous membrane relative to the impermeable sheet and in a direction normal to the sheet to allow passage of the distillate in the direction of the hot feed flow;
• and
• (e) draining the flowing distillate from the collecting chamber along the direction of hot feed flow.

Method of efficiently and continuously distilling a hot aqueous feed containing a low volatility solute such as salt comprising the steps of:

• (a) rapidly flowing the hot feed past, and in intimate contact with, one side of a microporous membrane;
• (b) diffusing water vapor through the membrane;
• (c) condensing the diffused water vapor using a thermally conductive impermeable sheet positioned on the side of the microporous membrane opposite the hot feed, the condensing step including the steps of collecting the condensed distillate in the chamber defined in part by the microporous membrane and the impermeable sheet, and intimately contacting both the membrane and the sheet with the collected distillate;
• (d) stripping the condensed and collected distillate from the chamber using forces exerted by the rapidly flowing hot feed flow acting across the microporous membrane on the distillate sandwiched between the membrane and the sheet, the forces causing distillate flow in the same direction as hot feed flow, said stripping step including the step of locally deforming the microporous membrane relative to the impermeable sheet and in a direction normal to the sheet to allow passage of the distillate in the direction of the hot feed flow, said stripping step maintaining the condensed distillate in relatively thin layers for efficient transfer of the sensible heat to the sheet;
• (e) draining the flowing distillate from the collecting chamber along the direction of hot feed flow;
• and
• (f) recovering the latent heat of condensation of the distillate, said latent heat recovering step including the steps of (1) cooling the impermeable sheet by flowing cold aqueous feed past the sheet in a direction opposite to the hot feed flow direction, the cold feed absorbing the latent heat of condensation transmitted through the heat conductive sheet, (2) additionally heating the cold feed after it has cooled the sheet and absorbed the latent heat, said additional heating step raising the temperature of the cold feed up to the temperature of the hot feed, and (3) introducing the heated cold feed for flow past the membrane.