Abstract: The invention is directed to a method for producing a purified lignin salt from alkaline spent liquor from the chemical cooking of lignocellulosic raw materials. The method comprises the steps of decreasing the spent liquor pH to form a lignin precipitate suspension; filtering the lignin precipitate to form a lignin filter cake and a filtrate; mixing the lignin filter cake into a dilution liquid to form an alkalilignin agglomerate colloid; subjecting the alkalilignin agglomerate colloid to large-pore membrane filtration; and recovering a purified lignin salt concentrate.

Abstract: Lignin-rich starting material is suspended in a first medium, which is acidic and aqueous, to form a aqueous acidic suspension, which is heated and allowed to form two continuous phases, a thermoplastic lignin phase and an aqueous phase. The thermoplastic lignin phase is separated from the aqueous phase and passed through a shape giving process into a second medium which is at a temperature lower than that of the thermoplastic lignin phase and in which the thermoplastic lignin phase is essentially insoluble. Solid lignin formed in the second medium is recovered.

Abstract: Lignin-rich starting material is suspended in a first medium, which is acidic and aqueous, to form a aqueous acidic suspension, which is heated and allowed to form two continuous phases, a thermoplastic lignin phase and an aqueous phase. The thermoplastic lignin phase is separated from the aqueous phase and passed through a shape giving process into a second medium which is at a temperature lower than that of the thermoplastic lignin phase and in which the thermoplastic lignin phase is essentially insoluble. Solid lignin formed in the second medium is recovered.