METHOD AND ARRANGEMENT FOR STEAMING AND IMPREGNATING WOOD CHIPS IN A DOWN FLOW VESSEL

摘要

The invention relates to a method and arrangement for steaming and impregnating wood chips in a single down flow vessel. A first upper volume of chips is established above a liquid level (LIQ_LEV) in the vessel, wherein steaming takes place. Said upper volume having a height (H1) of at least 2-5 meter. A second lower volume of chips is established below the liquid level, wherein an impregnation takes place. Said lower volume having a height (H1) of at least 2-5 meter.In order to reduce the torque demand on the bottom scraper are plug holding forces applied against the descending plug flow at a distance (H3) below the liquid level less than 20% of the height (H1) of said lower volume, such that a minimum free and unobstructed plug flow in the first volume is established which unobstructed plug flow is established at a vertical distance in said vessel exceeding 2-5 meter above the liquid level.