Apparatus and method for osmotic membrane distillation

Abstract

A method of enhancing the concentration of a first inorganic compound in a first aqueous solution of a first process of a heavy chemical plant, the method comprising (a) feeding the first solution having the first compound at a first concentration and a first water vapor pressure to an osmotic membrane distillation means comprising a hydrophobic, gas and water vapor permeable membrane separating (i) a first chamber for receiving the first solution, from (ii) a second chamber for receiving a receiver feed aqueous solution having a second water vapor pressure lower than the first water vapor pressure; (b) feeding the receiver aqueous feed solution to the second chamber as to effect transfer of water vapor through the membrane from the first chamber to the second chamber, and to produce (i) a resultant first solution having a second concentration of the first compound greater than the first concentration and (ii) a diluted receiver feed aqueous solution; and (c) collecting the resultant first solution. The apparatus and method are of particular value in electrolytic haloalkali production plants in offering reduced capital and operating re-concentration and dilution costs.

1 .- 24 . (canceled) 
   
   
       25 . Apparatus for enhancing the concentration of a first inorganic compound in a first aqueous solution having a first water vapor pressure provided by a first process of a heavy chemical plant by osmotic membrane distillation, said apparatus comprising
 osmotic membrane distillation means comprising   
     (i) a hydrophobic, gas and water permeable membrane; 
     (ii) a first chamber for receiving said first solution; and 
     (iii) a second chamber for receiving a receiver feed aqueous solution having a second water vapor pressure lower than said first water vapor pressure and separated from said first chamber by said membrane means;
 means for feeding said first solution to said first chamber and means for feeding said receiver feed aqueous solution to said second chamber as to operably effect transfer of water vapor through said membrane from said first chamber to said second chamber, and to produce 
 
     (i) a diluted receiver feed aqueous solution; 
     (ii) a diluted receiver feed aqueous solution;
 means for collecting said resultant first solution; and 
 means for collecting said diluted receiver feed solution. 
 
   
   
       26 . Apparatus as defined in  claim 25  wherein said receiver feed aqueous solution is provided by a second process of said heavy chemical plant. 
   
   
       27 . Apparatus as defined in  claim 25  further comprising means for recycling said resultant first solution back to said chemical plant. 
   
   
       28 . Apparatus as defined in  claim 27  further comprising means for recycling said diluted receiver feed solution back to said chemical plant. 
   
   
       29 . Apparatus as defined in  claim 28  wherein said member is microporous. 
   
   
       30 . Apparatus as defined in  claim 25  further comprising means for providing isothermal operation at a temperature of at least 50° C. 
   
   
       31 . Apparatus as defined in  claim 25  comprising means for feeding to said first chamber spent alkali metal halide solution constituting said first solution obtained from an electrolytic cell for the production of halogen and alkali metal hydroxide from alkali metal halide. 
   
   
       32 . Apparatus as defined in  claim 25  comprising means for feeding to said second chamber, said receiver feed solution selected from the group consisting of 
     (i) concentrated brine, 
     (ii) concentrated sodium hydroxide; and 
     (iii) spent sulfuric acid from a chlorine drying process. 
   
   
       33 . An improved haloalkali production plant comprising
 an electrolytic cell for the electrolytic production of alkali metal hydroxide and halogen from an alkali metal halide solution;   means for feeding alkali metal halide solution to said cell;   means for collecting spent alkali metal halide solution having a spent water vapor pressure from said cell;   means for collecting said alkali metal hydroxide from said cell;   the improvement comprising   osmotic membrane distillation means comprising
 (i) a hydrophobic, gas and water vapor permeable membrane; 
 (ii) a first chamber for receiving said spent alkali metal halide solution and wherein the production of re-concentrated alkali metal halide solution is effected; and 
 (iii) a second chamber for receiving a receiver feed aqueous solution having a receiver water vapor pressure lower than said spent water vapor pressure, separated from said first chamber by said membrane and wherein the production of a diluted receiver feed aqueous solution is effected; 
   means for feeding said spent alkali metal halide solution to said first chamber;   means for feeding said receiver feed aqueous solution to said second chamber;   means for recycling said re-concentrated alkali metal halide solution in whole or in part, directly or indirectly from said first chamber to said electrolytic cell; and   means for collecting said diluted receiver feed aqueous solution from said second chamber   
   
   
       34 . A plant as defined in  claim 33  further comprising means for feeding said alkali metal hydroxide to said second chamber. 
   
   
       35 . A plant as defined in  claim 33  wherein said alkali metal halide is sodium chloride. 
   
   
       36 . A plant as defined in  claim 33  wherein said hydrophobic, gas and water vapor permeable membrane is microporous. 
   
   
       37 .- 38 . (canceled)