Effect of precipitation conditions on properties of lignin from the LignBoost process

Other conference contribution, 2007

Lignin extraction from black liquor is today an attractive option for pulp mills. Besides the fact that the pulp production may be increased without expanding the recovery boiler the extracted lignin can be used as a fuel internally or be sold as a product, to an external company; either as biofuel or as a feed stock in the production of various chemicals e.g. phenols. This investigation deals with the precipitation conditions and theirs influence on the lignin properties, when using the LignoBoost concept. The precipitation of lignin was tested in the pH range between 11.5 and 9.0. Both softwood black liquor and hardwood black liquor was precipitated to evaluate the possibility to produce lignin with different chemical properties. The results indicate that a high quality lignin, i.e. low sodium content and low carbohydrate content can be produced without problems from the softwood black liquor. The hardwood black liquor was however harder to separate and wash. The sodium content was held at low levels but the carbohydrate content was still present in the lignin after washing.