Patent ID: 7615134

Claim:
A method for the impregnation of chips during the manufacture of chemical pulp comprising: (a) continuously feeding chips without preceding steaming to a top of an impregnation vessel in which a pressure at essentially atmospheric pressure, ±0.5 bar, is established at the top, and continuously feeding out impregnated chips at a bottom of the impregnation vessel, providing a first impregnation fluid having a first temperature and a second impregnation fluid having a second temperature, (b) heating the chips in an upper fluid-filled zone of the impregnation vessel by adding the first impregnation fluid at the first temperature, (c) heating the chips in a second fluid-filled zone under the upper fluid-filled zone by adding the second impregnation fluid at the second temperature that exceeds the first temperature by at least 5° C., (d) establishing a fluid level in the impregnation vessel by adding and withdrawing impregnation fluid, establishing the fluid level such that the fluid level lies under a chip-level of the chips in the impregnation vessel, and withdrawing impregnation fluid at a position in the impregnation vessel above a position of addition of the first impregnation fluid, establishing a flow (BL 1 V ) of impregnation fluid in a direction opposite to a sinking motion of the chips in at least an upper part of the impregnation vessel.