METHOD AND SYSTEM FOR IMPREGNATING CHIPS

The invention concerns a method， system and a withdrawal screen section for the impregnation of chips during the manufacture of chemical pulp. Chips are both steamed and impregnated in a low pressure impregnation vessel 3， using pressurised hot spent cooking liquor BL as the main part of the impregnation liquid， which hot spent cooking liquor produce most of the steam BLST necessary for steaming the chips.In order to reduce need for adding fresh steam for chip steaming is a first withdrawal section in the impregnation vessel 3 modified to be used both as a flash tank for warm pressurised wash filtrate as well as an improved wash-out feature for the spent impregnation liquid behind the screen in the withdrawal section. For this purpose is the withdrawal volume 60 arranged with an upper part 60a being located above the liquid level LIQLEV of the impregnation vessel， and an additional pressurised warm wash liquor REC1 is added to the withdrawal volume， and steam flashed off is led in a steam duct 62 to the chip volume above the liquid level. The invention concerns a method， system and a withdrawal screen section for the impregnation of chips during the manufacture of chemical pulp. Chips are both steamed and impregnated in a low pressure impregnation vessel 3， using pressurised hot spent cooking liquor BL as the main part of the impregnation liquid， which hot spent cooking liquor produce most of the steam BL ST necessary for steaming the chips.In order to reduce need for adding fresh steam for chip steaming is a first withdrawal section in the impregnation vessel 3 modified to be used both as a flash tank for warm pressurised wash filtrate as well as an improved wash-out feature for the spent impregnation liquid behind the screen in the withdrawal section. For this purpose is the withdrawal volume 60 arranged with an upper part 60a being located above the liquid level LIQLEV of the impregnation vessel， and an additional pressurised warm wash liquor REC1 is added to the withdrawal volume， and steam flashed off is led in a steam duct 62 to the chip volume above the liquid level.