Methods for obtaining deicers from black liquor

A method for making and using a deicing product from black liquor, which comprises:

• (a) using a black liquor having a pH of at least 6.5 and containing lignin, lignin degradation products and including lignin cellulose fragments and hemicelluloses, acids of the group consisting of acetate, carbonate, formate, pseudolactate, and having at least one cation selected from the group consisting of sodium, potassium, magnesium and calcium, as obtained from a pulp mill operation using a pulping process,
• (b) fractionating said black liquor from step (a) into a low molecular weight fraction wherein the compounds present in said fraction have molecular weight, of less than 500 and wherein said fraction comprises based upon the total weight of solid in said fraction, between 12% and 75% acetate salts, trace amounts and 36% carbonate salts, 1 and 24% formate salts, 1 and 32% pseudolactate salts and wherein the cation of said salts is at least one member selected from the class consisting of:
• sodium, potassium, magnesium and calcium, with the proviso that when lignin fractions having molecular weights of less than 500 and sugars having molecular weight of about 150 to 180 are present, the weight of said sugars and said lignin are less than 25% based upon said total weight of salts, said step (b) thereby maximizing the production of said salts,
• said fractionating in step (b) being selected from one of the group of methods consisting of:
• (i) control of partial wet oxidation of the black liquor under pressure and at a temperature between 140.degree. and 230.degree. C. to breakdown the high molecular weight fraction containing lignin, lignin degradation products and including lignin cellulose fragments and hemicelluloses, into low molecular weight fractions consisting of compounds having molecular weight of less than 500, and simultaneously during said control of partial wet oxidation, to favourably increase said salts, said control being obtained by the oxidation period, the temperature and pressure, and the amount and nature of the oxidation source, and
• (ii) direct membrane filtration to obtain the low molecular weight fraction wherein the compounds present have a molecular weight of less than 500 collected as the permeate, and said permeate as a whole constitutes said deicer, and wherein prior to said membrane filtration, said black liquor is filtered to remove large suspended particles and part of the high molecular weight fractions,
• (c) concentrating said low molecular weight fraction as obtained from step (b) to produce a concentrated deicing product having between 20% and 100% total solid concentration, wherein the compounds present have a molecular weight of less than 500 and wherein said fraction comprises based upon the total weight of solid in said fraction, between 12% and 75% acetate salts, trace amounts and 36% carbonate salts, 1 and 24% formate salts, and 32% pseudolactate salts and wherein the cation of said salts is at least one member selected from the class consisting of:
• sodium, potassium, magnesium and calcium, with the proviso that when lignin fractions having molecular weights of less than 500 and sugars having molecular weight of about 150 to 180 are present, the weight of said sugars and said lignin are less than 25% based upon said total weight of solids, and applying the product obtained from step (c) to a road surface in an amount sufficient to deice said surface.