A feasibility study of a novel electro-membrane based process to acidify Kraft black liquor and extract lignin

Lignin extraction from black liquor is of utmost importance for decreasing the load of the recovery boiler and consequently increasing the production capacity of Kraft process. A feasibility study of a novel acidification technique (acidification with electrodialysis using bipolar membrane (EDBM)) was carried out to drop the pH of Kraft black liquor and extract lignin. In order to evaluate the technical feasibility of the proposed method, the acidification of the Kraft black liquor was performed in two different pathways i.e. electrochemical acidification by means of EDBM process and chemical acidification using sulfuric acid. The results have indicated that the implementation of the proposed method resulting in use of less chemicals than the chemical acidification method and simultaneously production of caustic soda. The experiments performed in the course of this study addressed the advantages and challenges of this electro-membrane based process in the Kraft black liquor acidification application.