Patent ID: 7501043

Claim:
A method for the treatment of chips, comprising: heating the chips with steam in a steam treatment inside a steam treatment vessel, adding an acidic fluid to the chips disposed in the steam treatment vessel while the chips are being steamed in the steam treatment vessel in an amount that gives the chips at least a five-fold increase in an ionic concentration of hydrogen ions at an end of the steam treatment compared to steam treatment without adding the acidic fluid, in the steam treatment vessel, heating the chips together with the acidic fluid by the steam for a period of 1-20 minutes, the chips falling down through a chute connected to the steam treatment vessel, adding an alkali impregnation fluid to the chute while the chips fall therethrough, forming the chips to a slurry in the chute with the alkali impregnation fluid, wherein said alkali impregnation fluid comprises a liquor with sulfides, conveying the slurry to a digester, and cooking the chips in the digester.