GB1455399A - Method for digesting wood - Google Patents

Abstract

1455399 Digesting wood MO OCH DOMSJO AB 10 Sept 1974 [10 Sept 1973] 39459/74 Heading D2W In a method of digesting wood with an alkaline cooking liquor in the presence of a gas containing molecular oxygen, digested fibres on the surface of the wood are detached and removed from the digester in suspension in liquid, and the wood from which the fibres have been detached is subjected to further digestion. The wood may be either a hardwood or softwood and may be digested in the form' of chips, shavings, or splinters. The gas containing molecular oxygen may be pure oxygen or a mixture thereof with other gases. The alkali used for the cooking liquor may be a hydroxide, carbonate, or hydrogen carbonate of an alkali or alkaline earth metal or an ammonium compound or ammonia. The fibres may be detached from the surface of wood by spraying with a liquid e.g. digestion liquor and/ or by blowing with a gas e.g. the molecularoxygen containing gas and/or by mechanical treatment e.g. using peg shredders or agitators and/or by using a pump and/or by using a rotary digester to provide a rubbing action and/or by use of one or more vibrators in the digester or a vibrating table or screen. The word "wood" as used in the specification is not intended to include defibrilated wood i.e. mechanical pulp or chemical-mechanical or semichemical pulp. However, prior to digestion with oxygen-containing gas and alkali, the wood may be subjected to a chemical pretreatment process with an acid, neutral or alkaline aqueous solution at elevated temperatures.