US 5,676,795 A · Process for the production of viscose pulp

Abstract

The present invention relates to a process for producing viscose pulp from lignocelluloses, such as hardwood, softwood or annual plants, in which process the lignocellulose is treated in a digester at first with saturated steam to prehydrolyze hemicelluloses and subsequently, without flashing, with hot black liquor (HSL) of a preceding sulfate pulp digestion as well as, if desired, under addition of fresh white liquor (WL) to neutralize the acidic reaction products formed, neutralization liquor (NL) thus being formed in the digester. Upon addition of the amount of alkali required for delignification in the form of fresh white liquor (WL), if desired, in combination with a displacement of neutralization liquor (NL) and temperature adjustment, digestion then will take place with or without temperature gradient. When reaching the desired degree of digestion, digestion is terminated by displacement of the hot black liquor (HSL) with cold alkaline washing filtrate (WF), at the same time the pulp is freed from still adhering lignin degradation products, and the thus obtained pulp is discharged from the digester at a temperature of below 100.degree. C.

Claims17

Dependent claims

A process for producing viscose pulp from lignocelluloses according to a steam prehydrolysis sulfate (Kraft) displacement digestion process, comprising the steps of:

i) in a digester, prehydrolysing lignocellulose with saturated steam;
ii) neutralizing the prehydrolysed lignocellulose by adding a hot black liquor, and optionally fresh white liquor;
thereby forming a neutralization liquor;
iii) digesting and delignifying the neutralized lignocellulose by adding a fresh white liquor and optionally heating, thereby displacing a partial amount of said neutralization liquor, forming a digestion liquor, and forming a digested fiber material and lignin;
iv) washing said lignin from said digested fiber material by adding an alkaline washing filtrate, thereby displacing said digestion liquor and forming a viscose pulp;
and
v) cooling and discharging said viscose pulp.

4 more elements

Dependencies are inferred from the claim text.

Process for the production of viscose pulp

Life of this patent

Process for the production of viscose pulp

Life of this patent

Abstract

Claims17