Ultra-high-temperature pulping: Effect of pressure release and chip impactat the end of cooking on the pulp properties

This study was carried out to determine the effect of pressure release and chip impact against a wall of the release vessel during ultra-high-temperat ure pulping. Specific refining energy, fiber properties and strength of lab oratory sheets were examined. Chips impregnated with sodium sulfite and/or sodium bicarbonate were used in the study. Sudden pressure release combined with a strong impact of the chips against a wall produce the most significant effect on chip structure and provide pu lp of high quality with low refining energy consumption. Chip impact plays a significant role during ultra-high-temperature pulping and is considered more important with regard to pulp properties than sudden pressure discharg e without chip impact.