Osmotic separation systems and methods

Abstract

Separation processes using osmotically driven membrane systems are disclosed generally involving the extraction of solvent from a first solution to concentrate solute by using a second concentrated solution to draw the solvent from the first solution across a semi-permeable membrane.

What is claimed is: 
     
         1 . A system for osmotic extraction of a solvent from a first solution, comprising:
 a plurality of forward osmosis units, each comprising:
 a first chamber having an inlet fluidly coupled to a source of the first solution; 
 a second chamber having an inlet fluidly coupled to a source of a concentrated draw solution; and 
 a semi-permeable membrane system separating the first chamber from the second chamber and configured for osmotically separating the solvent from the first solution, thereby forming a second solution in the first chamber and a dilute draw solution in the second chamber; 
   a separation system in fluid communication with the plurality of forward osmosis units and configured to separate the dilute draw solution into the concentrated draw solution and a solvent stream, and   a flushing system in fluid communication with the plurality of forward osmosis units and   the separation system, the flushing system comprising:
 a source of flushing solution; 
 a fluid transfer device in fluid communication with the source of flushing solution and at least one of the plurality of forward osmosis units; 
 a valve arrangement in fluid communication with the source of flushing solution, the fluid transfer device, and the at least one forward osmosis unit; and 
 a control system in communication with at least one of the source of flushing solution, the fluid transfer device, or the valve arrangement, where the control system is configured to operatively connect the source of flushing solution with the at least one forward osmosis unit via the fluid transfer device and the valve arrangement. 
   
     
     
         2 . The system of  claim 1 , wherein the valve arrangement comprises:
 a plurality of valves; and   at least one sensor, wherein the at least one sensor is configured to generate a signal based on at least one operating characteristic of the system.   
     
     
         3 . The system of  claim 2 , wherein the control system comprises a set of instructions configured to control the flushing system according to at least one of a predetermined protocol or as triggered by one or more signals generated by the at least on sensor. 
     
     
         4 . The system of  claim 3 , wherein the control system actuates one or more of the plurality of valves to direct a flow of flushing solution from the source of flushing solution through the second chamber of the at least one forward osmosis unit. 
     
     
         5 . The system of  claim 1 , wherein the control system directs the flushing solution to each of the plurality of forward osmosis units in series. 
     
     
         6 . A system for osmotic extraction of a solvent from a first solution, comprising:
 a forward osmosis unit comprising:
 a first chamber having an inlet fluidly coupled to a source of the first solution; 
 a second chamber having an inlet fluidly coupled to a source of a concentrated draw solution; and 
 a semi-permeable membrane system separating the first chamber from the second chamber and configured for osmotically separating the solvent from the first solution, thereby forming a second solution in the first chamber and a dilute draw solution in the second chamber; 
   a separation system in fluid communication with the forward osmosis unit and configured to separate the dilute draw solution into the concentrated draw solution and a solvent stream, the separation system comprising a filtration unit, a reverse osmosis unit, and a by-pass circuit all in fluid communication with the forward osmosis unit, wherein:
 the filtration unit comprises: 
 a first chamber having an inlet fluidly coupled to the second chamber of the forward osmosis unit for receiving at least a first portion of the dilute draw solution; 
 a second chamber having an outlet fluidly coupled to the reverse osmosis unit for transferring a less dilute draw solution thereto; and 
 a filtration membrane separating the first chamber from the second chamber and configured for partially removing solutes from the dilute draw solution, thereby forming the less dilute draw solution in the second chamber, wherein the removed solutes are returned to the first chamber of the forward osmosis unit via an outlet from the first chamber of the filtration unit; 
 the reverse osmosis unit comprises: 
 a first chamber having an inlet fluidly coupled to the second chamber of the forward osmosis unit for receiving at least a second portion of the dilute draw solution and an outlet fluidly coupled to the second chamber of the forward osmosis unit for introducing the concentrated draws solution thereto; 
 a semi-permeable membrane coupled to the first chamber; and 
 a second chamber coupled to the semi-permeable membrane and configured for receiving a solvent fluxed through the membrane, thereby leaving the concentrated draw solution in the first chamber for transfer to the forward osmosis unit; and 
 the by-pass circuit configured to selectively direct the first and second portions of the dilute draw solution to the filtration unit and the reverse osmosis unit. 
   
     
     
         7 . The system of  claim 6 , wherein the forward osmosis unit comprises a plurality of forward osmosis units, each comprising:
 a first chamber having an inlet fluidly coupled to the source of the first solution;   a second chamber having an inlet fluidly coupled to the source of a concentrated draw solution; and   a semi-permeable membrane system separating the first chamber from the second chamber and configured for osmotically separating the solvent from the first solution, thereby forming the second solution in the first chambers and the dilute draw solution in the second chambers.   
     
     
         8 . The system of  claim 6 , wherein the portions of the dilute draw solution are delivered to at least one of the filtration unit and the reverse osmosis unit under pressure. 
     
     
         9 . The system of  claim 6 , wherein the separation system further comprises means for introducing an additive to at least one of the first portion or the second portion of the dilute draw solution. 
     
     
         10 . The system of  claim 6 , wherein the separation system further comprises a thermal recovery unit in fluid communication with the outlet of the first chamber of the reverse osmosis unit for receiving the concentrated draw solution therefrom for further concentration and the second chamber of the forward osmosis unit for introducing the more concentrated draw solution thereto.