Extracting hemicelluloses prior to aspen chemi-thermomechanical pulping: Effects of pre-extraction on pulp properties

Pre-extraction of hemicelluloses prior to pulping and conversion of the extracted hemicelluloses to other by-products will provide additional revenues to traditional pulp and paper industry. The effects of hemicelluloses pre-extraction with sulfuric acid on aspen (Populus tremuloides) chemi-thermomechanical pulp (CTMP) properties were investigated in this study. The sulfuric acid pre-extraction resulted in a release of 11% of hemicelluloses (determined as xylan) and acetic acid, especially at the second press-impregnation stage. Compared with CTMP without acid pre-extraction, the acid pre-extraction significantly reduced refining energy to a given freeness, and the pulps produced from acid pre-extracted chips have lower shives, higher strength properties except zero-span breaking length, lower bulk, but lower brightness at a similar specific refining energy. This study provides useful information for integration of biorefinery in mechanical pulp mills in the future.