VALORIZATION OF SULFUR FREE BLACK LIQUOR THROUGH HYDROTHERMAL LIQUEFACTION

摘要

Numerous studies deal with the conversion of chemical pulp mills into wood-based biorefineries. In particular, the extraction of the hemicelluloses by an autohydrolysis allows the recovery of sugars for the chemical industry and the use of a soda cooking instead of a kraft cooking to produce cellulosic pulp. Lignin ends up in an aqueous effluent called black liquor, usually burned in a Thomlison boiler to recover the sodium and energy. In this work, conversion of black liquor through hydrothermal liquefaction will be compared to the Thomlinson recovery in term of energy efficiency, sodium recovery and the production of phenolic compounds will be studied. Experiments were performed in a batch reactor between 250 and 310°C and 5 and 120min using a sulfur free black liquor at 19%WT. A viscous biocrude containing up to 59% of the carbon and 70% of the HHV of black liquor is produced. The remaining aqueous phase contains 97% of initial Na and phenolic compounds (mainly catechol, guaiacol and syringol). Medium molecular weight of organic molecules in the aqueous phase is divided by 6. Those results demonstrate hydrothermal liquefaction is efficient in term of energy and sodium recovery and chemical plateform molecules were produced.