Dewatering black liquor and lignin with supercritical CO2

Black liquor, the residue remaining from pulping wood chips for papermaking, is used as fuel to power mill. For energy efficiency, black liquor must be concentrated over 65% solids prior combustion. Supercritical CO2 achieves this by precipitating lignin dropping pH below pKa of phenolic groups in lignin, thereby depositing and creating a porous liquid/solid matrix. It then displaces water matrix manner analogous dewatering materials such biomass, coal, sludge. Thus, supercritical performs dual role generating it. The amount removed far exceeds its solubility proportional boiling point rise liquor. This opens possibility replacing one or more stages multi-effect evaporator with unit. A similar approach applies deposited use biofuel chemical feedstock. Porosity appears control displacement process being facile open structures.