System for liquid extraction, and methods

Abstract

A process for removing water from solid material using liquid-solid extraction and liquid-liquid extraction. In most embodiments, multiple solvents are used to remove the water from the solids and obtain dry solids. Multiple solvents facilitate the removal of the water from the solids, by replacing the water with a solvent, replacing that solvent with a different solvent, and then eventually removing the second solvent from the solids. The process utilizes a lesser amount of thermal energy to dry the solids and separate the solvents than conventionally used in drying processes. The first solvent selected has a lower heat of vaporization, enthalphy of vaporization, boiling point, or other such physical property, than water. Each additional solvent can have a still lower heat of vaporization, enthalphy of vaporization, boiling point, or other such physical property.

We claim: 
     
         1 . A process for drying solids initially wet with water, the process comprising:
 (a) contacting a feed stream with a first solvent and a second solvent, the feed stream comprising solids having interstitial spaces therebetween and water present in the interstitial spaces, wherein the first solvent and the second solvent are introduced into the solids concurrently, the first solvent having a heat of vaporization lower than the heat of vaporization of water and being miscible with water, and the second solvent having a heat of vaporization lower than the heat of vaporization of the first solvent, being insoluble with water, and being miscible with the first solvent;   (b) displacing the water present in the interstitial spaces with the second solvent to provide solids having the second solvent present in the interstitial spaces; and   (c) removing the second solvent from the interstitial spaces of the solids by the application of heat.   
     
     
         2 . The process according to  claim 1 , wherein contacting a feed stream with a first solvent comprises:
 (a) contacting the feed stream with a first solvent that is an alcohol.   
     
     
         3 . The process according to  claim 2 , wherein contacting the feed stream with a first solvent that is an alcohol comprises:
 (a) contacting the feed stream with a first solvent that is ethanol.   
     
     
         4 . The process according to  claim 2 , wherein contacting the feed stream with a second solvent comprises:
 (a) contacting the feed stream with a second solvent that is a halogenated hydrocarbon.   
     
     
         5 . The process according to  claim 4 , wherein contacting the feed stream with a second solvent comprises:
 (a) contacting the feed stream with a second solvent that is n-propyl bromide.   
     
     
         6 . The process according to  claim 1 , wherein contacting a feed stream with a first solvent and a second solvent comprises:
 (a) contacting the feed stream with the first solvent mixed with the second solvent.   
     
     
         7 . The process according to  claim 6 , wherein:
 (a) contacting a feed stream with a first solvent and a second solvent comprises combining a feed stream with an alcohol and with n-propyl bromide; and the process further comprises:   (b) obtaining a product that is at least 95% pure n-propyl bromide; and   (c) obtaining an alcohol product that is at least 90% pure alcohol.   
     
     
         8 . The process according to  claim 7 , wherein:
 (a) combining a feed stream with an alcohol comprises combining with ethanol; and   (b) obtaining an alcohol product that is at least 90% pure alcohol comprises obtaining an alcohol product that is at least 95% pure ethanol.