APPARATUS AND METHOD FOR PRE-TREATMENT OF WOOD CHIPS

摘要

A pre-treatment device (11) for wood chips for pulping comprises a tube through which the chips fall into a digester (13). Steam is injected (26) into the tube through rings of nozzles (28), which are angled circumferentially to impart a rotary and turbulent motion to the falling chips. Some nozzles (28) are angled downwardly to encourage the chips to flow freely through the tube, some are horizontal to encourage a longer dwell time near the nozzles (28). Digesting liquor is also sprayed (34) on the chips from spray nozzles (42) after the first ring of steam nozzles (28). The heat and steam expel air and other non-condensable gases and volatiles form the chips, allowing them to absorb the liquor. At the bottom of the tube, the chips are propelled down and outwards by jets of higher-pressure steam, spreading and packing them into the digester (13).