Thermal Degradation of Alkaline Black Liquor from Straw. Thermogravimetric Study

Abstract

Both pyrolysis and gasification can be considered as alternatives to conventional boilers for recovering chemicals and energy from black liquor. The present work is focused on the study of pyrolysis of alkaline black liquor from straw, and its interest is enhanced by the fact that the material used has hardly been studied before. The influence has been studied of the final pyrolysis temperature (500-900°C), the heating rate (5-30°C/min), and the addition of a determined CO concentration in the N 2 atmosphere (5-40% vol) on both the final solid conversion and the devolatilization rate. The results show that the thermal decomposition of the organic matter fraction of black liquor takes place at temperatures below 550°C in N 2 atmosphere. The weight loss observed at temperatures higher than 550°C is mainly due to reduction reactions of alkaline compounds by the carbon. The final solid conversion and the devolatilization rate are also noticeably influenced by the addition of a certain CO flow rate in N 2 atmosphere.