Thermal studies on kraft black liquor

Abstract Kraft black liquor and lignin from the same batch were subjected to thermal analysis (DTA and TGA) under an inert atmosphere and also in an oxidising atmosphere to simulate conditions which might be encountered in the recovery furnace. Gasification studies were carried out by rapidly heating the sample under helium. Results showed that the thermal decomposition of black liquor can be divided into four characteristic steps: drying up to 200°C, pyrolysis between 200 and 550°C, inorganic sodium salt formation between 550 and 800°C and salt fusion between 800 and 1000°C. Gases evolved during gasification of black liquor are rich in flammable compounds while those from the lignin sample are rich in CO2.