Mo Och Domsjo Aktiebolag

Mo Och Domsjo

Erik Olof Hagglund

Hans O Samuelson

Hans Olof Samuelson

Leif Ake Smedman

Ulf Torbjorn Olson

A process is provided for reducing carbohydrate losses in the sulphate pulping of wood using sodium hydroxide and sodium sulfide, by pretreating the wood in the presence of water with oxygen gas and nitrogen oxide such as NO.sub.2 and/or NO and/or polymeric oxides and double molecules thereof, for example, N.sub.2 O.sub.4 or N.sub.2 O.sub.3, for from about 3 to about 110 minutes at a temperature within the range from about 25.degree. to about 100.degree. C., the amount of nitrogen oxide charged, calculated as monomers, being within the range from about 0.05 to about 1 kilomole per 1000 kg bone-dry wood, resulting in one or several of the following advantages: an improved yield of pulp, an improved viscosity, and a reduced requirement for bleaching chemicals in any subsequent bleaching stages.

Process for reducing carbohydrate losses in the sulfate pulping of wood

A method for improving heat economy in the batchwise digestion of lignocellulosic material especially when using a batch digester with a digestion or cooking liquor in which the digestion or cooking chemicals are dissolved, such as in sulphate, sulphite, bisulphite, oxygen, peroxide and ammonium hydroxide digestion processes, and also in the manufacture of high yield semichemical pulps. A superatmospheric gas pressure is applied above the level of the liquor in a batch digester; the level of the digester liquor is determined after the liquor has been absorbed by a batch lignocellulosic material; the level of free digestion liquor is then adjusted to that level providing an amount including the absorbed liquor to digest the lignocellulosic material; and then the material is digested under the superatmospheric pressure to form cellulose pulp.

Method for improving heat economy in the batchwise digestion of

A process is provided for producing cellulose pulp of high brightness, which comprises pulping lignocellulosic material such as wood with oxygen under superatmospheric pressure in two stages, in the first at a pH within the range from about 6 to about 9, and in the second at a more alkaline pH of at least about 10.

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Ornskoldsvik, Sweden

Erik Olof Hagglund