Patent ID: 7998310
Filing Date: 2011-08-16
Classification: D21C

Abstract:
1. A method for impregnating untreated chips during the manufacture of chemical pulp, comprising: continuously feeding untreated chips without a preceding steam treatment into an impregnation vessel, the impregnation vessel having an upper cylindrical part with a first inner cross-sectional area and a lower cylindrical part with a second inner cross-sectional area, a bottom of the lower cylindrical part having an outlet defined therein, establishing a chip level of chips in the upper cylindrical part, the chip level being located at a distance (h) above a fluid level consisting of a liquor and the untreated chips having an angle of repose of approximately 45 degrees when disposed in the first inner cross-sectional area, the chips, after passing through the upper cylindrical part, passing through a transitional part, establishing a liquid level in the transitional part, impregnating the untreated chips with a liquor while the chips sinking down into the second inner cross-sectional area, providing an increase of an area from the first inner cross-sectional area to the second inner cross-sectional area in the transitional part, increasing the second inner cross-sectional area compared to the first inner cross-sectional area so that the second inner cross-sectional area is greater than the first inner cross-sectional area by a factor of at least √{square root over (2)}, reducing an angle and locating at least 50% of the increase in an area between the first inner cross-sectional area and the second inner cross-sectional area above the fluid level; reducing the angle of repose of the impregnated chips in the second inner cross-sectional area to less than 10 degrees so that the impregnated chips are essentially horizontally disposed in the second inner cross-sectional area; and feeding out impregnated chips from the impregnation vessel, together with the liquor, through the outlet arranged at the bottom of the lower cylindrical part.