Multi-stage membrane distillation process

Patent metadata

Field	Value
Publication number	US-9718709-B2
Application number	US-201313798273-A
Country	US
Kind code	B2
Filing date	Mar 13, 2013
Priority date	Mar 13, 2013
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

Portions of a feed liquid are passed through respective condensers and liquid-liquid heat exchangers. The feed liquid is then heated and injected into a first feed-liquid containment chamber, where vapor from the feed is passed through a first gas-permeable membrane and directed into a first condenser, where the vapor is cooled by the feed liquid passing through the first condenser and condenses as it cools to produce a first liquid permeate. The first liquid permeate is passed through the first liquid-liquid heat exchanger where the first liquid permeate is cooled by the feed liquid passing therethrough. After the vapor is removed from the feed liquid in the first feed-liquid containment chamber, the remaining feed liquid from the first feed-liquid containment chamber is injected into a second feed-liquid containment chamber, where the process is repeated. The first liquid permeate from the first liquid liquid-liquid heat exchanger is combined with the second liquid permeate from the second condenser to form a combined liquid permeate; and the combined liquid permeate is passed through the second liquid-liquid heat exchanger where the combined liquid permeate is cooled by the feed liquid passing therethrough.

First claim

What is claimed is:

1. A multi-stage membrane distillation apparatus, comprising:
a source of liquid feed;
a plurality of purification stages including at least a first purification stage configured to receive liquid feed from the source and a second purification stage configured to receive liquid feed from the first purification stage, each purification stage respectively including:
a vacuum membrane distillation module, including:
a feed inlet in fluid communication with the source of liquid feed;
a gas-permeable membrane contained in the vacuum membrane distillation module;
a feed-liquid containment chamber for containing liquid feed from the feed inlet, wherein the feed-liquid containment chamber is positioned on one side of the gas-permeable membrane and is in fluid communication with the feed inlet;
a vapor-permeate containment chamber for containing vapor permeated from liquid feed through the gas-permeable membrane, wherein the vapor-permeate-containment chamber is positioned on an opposite side of the gas-permeable membrane from the feed-liquid containment chamber; and
a vapor-permeate outlet in fluid communication with the vapor-permeate-containment chamber for extracting the vapor permeate from the vapor-permeate-containment chamber; and

a condenser configured to condense the vapor permeate and including (a) a vapor-permeate inlet in fluid communication with the vapor-permeate outlet of the vacuum membrane distillation module and (b) a condensed liquid-permeate outlet through which condensed liquid permeate can be removed from the condenser;

a heat source configured to heat liquid feed only between the source of liquid feed and the first purification stage, wherein no heat source is configured to heat liquid feed in or between the purification stages;
at least one liquid-remainder conduit configured to provide fluid communication from the feed-liquid containment chamber in the vacuum membrane distillation module of the first purification stage to the feed-liquid containment chamber in the vacuum distillation module of the second purification stages; and
a plurality of regulators in fluid communication with and configured to establish a first reduced pressure in the vapor-permeate containment chamber of the first purification stage, a second reduced pressure in the vapor-permeate containment chamber of the second purification stage that is lower than the first reduced pressure, and a reduced condensing pressure in the condensers.

2. The multi-stage membrane distillation apparatus of claim 1 , wherein the source of liquid feed includes liquid feed comprising water and dissolved components.

3. The multi-stage membrane distillation apparatus of claim 1 , wherein each of the purification stages further includes:
a liquid-liquid heat exchanger in fluid communication with the liquid-permeate outlet of the condenser and configured for cooling condensed liquid permeate from the condenser; and
a liquid-feed conduit extending from the source of liquid feed and including:
a bifurcation between (a) the liquid-feed source and (b) the condenser and the liquid-liquid heat exchanger in a flow path from the liquid-feed source through the liquid-feed conduit, where the bifurcation splits the liquid-feed conduit into respective conduits passing through the condenser and through the liquid-liquid heat exchanger; and
a junction positioned and configured to rejoin the set of bifurcated conduits from the condenser and from the liquid-liquid heat exchanger into a common conduit extending toward and in fluid communication with the liquid-feed-containment chamber of the vacuum membrane distillation module,

wherein the multi-stage membrane distillation apparatus further includes a liquid-permeate extraction conduit including a plurality of liquid-permeate inlets, each respectively in fluid communication with the liquid-permeate outlet of the condenser of a respective purification stage, wherein the liquid-permeate extraction conduit is configured to pass condensed liquid permeate from the liquid-permeate inlets through the liquid-liquid heat exchangers.

4. The multi-stage membrane distillation apparatus of claim 3 , further comprising a liquid-permeate receptacle coupled with the liquid-permeate extraction conduit and configured to collect liquid permeate passed through the liquid-liquid heat exchangers.

5. The multi-stage membrane distillation apparatus of claim 3 , further comprising a heat source configured to heat liquid feed flowing through the liquid-feed conduit before entering the feed-liquid containment chamber in the vacuum membrane distillation module of the first stage.

6. The multi-stage membrane distillation apparatus of claim 1 , wherein the condenser is included in the vapor-permeate containment chamber and is configured to condense vapor that has passed through the gas-permeable membrane from the feed-liquid containment chamber.

7. A method for distillation of a feed liquid comprising:
passing portions of the feed liquid through a second condenser, through a first condenser, through a first liquid-liquid heat exchanger and through a second liquid-liquid heat exchanger; then
heating the feed liquid; then
injecting the feed liquid into a first feed-liquid containment chamber of a first vacuum membrane distillation module; then
passing vapor from the feed liquid in the first feed-liquid containment chamber through a first gas-permeable membrane;
directing vapor that has passed through the first gas-permeable membrane into the first condenser, wherein the vapor first enters a first vapor-permeate containment chamber on an opposite side of the first-gas-permeable membrane from the first feed-liquid containment chamber before entering the first condenser or wherein the first condenser is combined with the first vapor-permeate containment chamber on the opposite side of the first-gas-permeable membrane from the first feed-liquid containment chamber, and where the vapor is cooled by the feed liquid passing through the first condenser and condenses as it cools to produce a first liquid permeate;
passing the first liquid permeate through the first liquid-liquid heat exchanger where the first liquid permeate is cooled by the feed liquid passing therethrough;
after the vapor is removed from the feed liquid in the first feed-liquid containment chamber, injecting the remaining feed liquid from the first feed-liquid containment chamber into a second feed-liquid containment chamber of a second vacuum membrane distillation module, wherein the feed liquid injected into the first feed-liquid containment chamber is at a temperature at least 1° C. higher than the temperature at which the remaining feed liquid is injected into the second feed-liquid containment chamber; then
passing vapor from the feed liquid in the second feed-liquid containment chamber through a second gas-permeable membrane into a second vapor-permeate containment chamber;
actively reducing the pressure in the second vapor-permeate containment chamber to a pressure lower than the pressure in the first vapor-permeate containment chamber;
directing vapor that has passed through the second gas-permeable membrane into the second condenser, wherein the second condenser is combined with or downstream from the second vapor-permeate containment chamber, and where the vapor is cooled by the feed liquid passing through the second condenser and condenses as it cools to produce a second liquid permeate;
combining the first liquid permeate from the first liquid-liquid heat exchanger with the second liquid permeate from the second condenser to form a combined liquid permeate; and
passing the combined liquid permeate through the second liquid-liquid heat exchanger where the combined liquid permeate is cooled by the fe

Assignees

• Summers Edward K
• Lienhard V John H
• Massachusetts Inst Technology

Inventors

• Summers Edward K
• Lienhard V John H

Classifications

• C02F1/447 Primary

  by membrane distillation (distillation and evaporation without the use of membranes C02F1/04) · CPC title

• C02F2209/03

  Pressure · CPC title

• C02F2103/08

  Seawater, e.g. for desalination · CPC title

• Y02A20/124

  Water desalination · CPC title