Lignins derived from black liquor

Abstract

Depolymerized lignins contained within black liquor are transferred to an organic solvent, soluble in organic matter and insoluble of aqueous sodium compounds contained within the black liquor. Upon separation of the aqueous sodium compounds from the organic solvent, saturated with contained depolymerized lignins, depolymerized lignins are removed from the organic solvent to result in depolymerized lignins and a separated organic solvent suitable for recycling. Resulting aqueous sodium compounds are concentrated by a multiple effect evaporator to provide liquor to digest wood chips. Whereby depolymerized lignins, substantially free from sodium compounds, are separated from a black liquor. Accordingly this invention modifies black liquor without employing a lime kiln and a recovery boiler, producing a molten smelt.

What is claimed is:  
     
         1 . A method to produce lignins substantially free from sodium compounds, which comprises: 
 providing a black liquor containing depolymerized lignins, and    providing an organic solvent for extraction, and    subjecting said black liquor to extraction by said organic solvent to form an extractate of said depolymerized lignins contained in said organic solvent and a raffinate containing sodium hydroxide and, separating said extractate from said raffinate, and    separating said depolymerized lignins from said extractate to provide depolymerized lignins free of said organic solvent, and    recycling the heretofore separated organic solvent for extraction of additional black liquor, and    adding an acidic solution to the heretofore separated depolymerized lignins to form sodium salts and lignins insoluble within the sodium salts, and    separating lignins heretofore derived from the insoluble sodium salts whereby lignins substantially free of sodium compounds are obtained from a black liquor.    
     
     
         2 . The method as described in  claim 1  wherein said sodium salts are subjected to a bipolar membrane for a salt splitting operation from said sodium salts creates sodium hydroxide and creates an acid.  
     
     
         3 . The method as described in  claim 3  wherein sodium hydroxide is combined with said raffinate.  
     
     
         4 . The method as described in  claim 1  wherein said acidic solution added to said extractate forms gaseous hydrogen sulfide.  
     
     
         5 . The method as described in  claim 5  wherein the gaseous hydrogen sulfide is added to said raffinate and reacted with sodium hydroxide contained within said raffinate to form sodium sulfide.  
     
     
         6 . The method as described in  claim 1  wherein the acid is derived from carbon dioxide contained in a flue gas.  
     
     
         7 . The method as described in  claim 1  wherein said raffinate is concentrated within a multiple effect evaporator.  
     
     
         8 . The method as described in  claim 7  wherein the concentrated raffinate contains about 40% sodium hydroxide to about 10% sodium hydroxide.  
     
     
         9 . The method as described in  claim 7  wherein the concentrated raffinate is substantially skimmed of tall oil.  
     
     
         10 . The method as described in  claim 1  wherein said black liquor contains sodium sulfide.  
     
     
         11 . The method as described in  claim 1  wherein said black liquor contains polysulfide polymers.  
     
     
         12 . The method as described in  claim 1  wherein said black liquor contains anthroquinone.  
     
     
         13 . The method as described in  claim 1  wherein said black liquor is supplied from kraft pulping digestion.  
     
     
         14 . The method as described in  claim 1  wherein said black liquor is supplied from soda pulping digestion.  
     
     
         15 . The method as described in  claim 1  wherein said extraction by said organic solvent is accomplished by counter flow of said organic solvent.  
     
     
         16 . The method as described in  claim 1  wherein said organic solvent is selected from the group of hydrocarbons, organic halogens and alcohols including an individual or a combination thereof.  
     
     
         17 . The method as described in  claim 1  wherein said extractate creates depolymerized lignins substantially devoid of organic solvent.  
     
     
         18 . The method as described in  claim 17  wherein the extractate is cooled to form depolymerized lignins.  
     
     
         19 . The method as described in  claim 1  wherein said extractate is subjected to a centrifuge to obtain organic solvent for recycle, and depolymerized lignins substantially devoid of the organic solvent.  
     
     
         20 . The method as described in  claim 1  wherein said depolymerized lignins are subject to gasification to produce gasification products which function as a fuel.