FAIR-CT97-3460 Bleachability of alkaline pulps

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FAIR Area 1.3 - Forestry-Wood Chain : Paper/Pulp : Pulping : Wood (Lignocellulose)

	Type of Project	Shared Cost
	Contract No	FAIR-CT97-3460
	Total Cost	1 989 324 ECU
	EC Contribution	1 450 000 ECU
	Start Date	01/11/1998
	Duration	36 months

Bleachability of alkaline pulps

Objectives

1. To understand how the chemical structure, reactivity and morphology of the pulp polymers in alkaline pulps, notably lignin and hemicelluloses, affect the bleachability measured as consumption of oxidation equivalents per kappa number unit.
2. To determine how wood species, wood quality and pulping variables in kraft pulping affect the bleachability, defined as above.
3. To find new ways of activating the lignin in kraft pulps prior to an oxygen delignification stage.

An understanding of the chemical structure and reactivity of lignin and polysaccharides (hemicelluloses) present in unbleached chemical pulps and how these structures are changed in different bleaching operations is essential to finding new environmentally sound pulping and bleaching processes. An increased efficiency in the use of bleaching agents is essential for a more cost-effective bleaching of chemical pulps. Further development of TCF bleaching sequences and ECF bleaching with a low charge of chlorine dioxide will facilitate a closing-up of pulp mills.

Technical Approach

This project will examine the bleachability of a variety of chemical pulps, hardwood and softwood, prepared in alkaline processes, predominantly kraft pulps. Major emphasis will be on:

• pulping and bleaching parameters in order to understand how these should be chosen in order to get an easy-to-bleach pulp with high strength.
• the correlation between chemical structure of the pulp polymers and the bleachability of the pulp in order to understand what structural requirements should be met to get a high reactivity towards bleaching agents.

The consumption of bleaching chemicals, calculated as oxidation equivalents per kappa number to reach high brightness of two modified kraft pulps
and one alkaline sulfite (ASAM) pulp. Bleaching with the sequence AZQP

Brightness vs. consumption of hydrogen peroxide to reach a given brightness in an OQP sequence. Softwood kraft pulps prepared with variation of cooking technique and change of alkali to reach kappa number 19 (kappa number after O is 11).

Contacts

Coordinator

• Goran GELLERSTEDT / KTH Division of Wood Chemistry / SWEDEN

EC Scientific Officer

• Ignacio SEOANE / European Commission DG Research Theme 1 Key Action 5.3 / BELGIUM

Participant

• Prof Dominique LACHENAL / Centre Technique de l'Industrie des Papiers, Cartons et Celluloses / FRANCE
• J. CANAVAL / Empresa Nacional de Celulosas S.A. Centro de Investigacion de Ence (CIE) / SPAIN
• Mr Tapani Vuorinen / Helsinki University of Technology Lab.of Forest Products Technology / FINLAND
• Bo HORTLING / KCL Science and Consulting FINLAND
• Södra Cell AB Technical Department / SWEDEN
• Carlos PASCOAL NETO / University of Aveiro Dept of Chemistry / PORTUGAL
• Jussi SIPILA / University of Helsinki Dept. of Chemistry / FINLAND