FIELD: chemistry.
SUBSTANCE: chips are both steamed and impregnated in a low pressure impregnation vessel, using pressurised hot spent cooking liquor BL as the main part of the impregnation liquid, where said hot spent cooking liquor produces most of the steam BLST necessary for steaming the chips. At least two independent first and second screen rows, SC1 and SC1b respectively, are installed in order to improve the process in the impregnation vessel. The first screen row withdraws acidified treatment liquor for disposal which otherwise would be excess acidified waste fluid in the system. The second screen row recirculates treatment fluid back to centre of the treatment vessel in order to even out the pH profile over the cross-section of the vessel.
EFFECT: improved system and method of impregnating and heating chips, fewer problems with formation of large amounts of acid condensates during steaming.
13 cl, 5 dwg
