Continuous treatment of small chips

Abstract

Paper pulp is produced from small chips (e.g. having a smallest dimension of between about 1 and 5 mm), which may be more easily penetrated by the treatment liquids resulting in a more uniform Kappa distribution which makes it possible to cook to lower Kappa numbers without losing strength. The chips are steamed and then impregnated with sulfur containing liquor in an impregnation vessel having a conveyor. The conveyor, such as an endless belt with baffles, moves the chips through the liquor rather than trying to circulate the liquor. From the impregnation vessel the chips move to the top of an upright digester where they are steamed, and then are subjected to digesting conditions, entrained in white liquor, in the digester and discharged from the bottom. The digester has smooth side walls, devoid of screens and circulation loops. At the bottom of the digester the chips--at a consistency of about 10 to 20%--are diluted to a consistency of about 6 to 10% and then passed, with a feeding a mechanism, to a first pressure diffuser. From the first pressure diffuser the chips pass through a flow control valve to a hot alkali extraction tank, and then to a second pressure diffuser.

Dependencies are inferred from the claim text.