method for separating lignin from black liquor, lignin product, and use of a lignin product for the production of fuels or materials

摘要

Method for Separation of Black Liquor Lignin, Lignin Product, and Use of a Lignin Product for Fuel or Material Production The invention relates to a method for controlling the sodium and sulfur balance of a cellulose pulp plant while separating lignin from black liquor, and also a lignin product or a lignin intermediate product obtainable by said method. The invention also provides for the use of a lignin product or a lignin intermediate product for the production of fuel (solid, gaseous or liquid) or materials. The method involves the following steps: (1) lignin precipitation using an acid followed by filtration, (2) resuspension of the filter cake, (3) filtration forming a second cake, and (4) return of the filtrate for washing and suspension in the previous steps. In a preferred embodiment, sodium sulfate rich esp (electrostatic precipitator) powder produced in the recovery boiler is used to wash the precipitated lignin.