AIR3-CT94-2507 New Demands on Laboratory-Refining in Quality Assessment of Paper Pulps

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AIR Cluster VII - Forestry and Forest Products : Paper/Pulp : Process Engineering

	Proposal No:	AIR3-CT94-2507
	Date Prepared:	September 1999
	Source:	Summary Report 1997

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Summary Report 1997

Summary

Chemical pulps are the most widely used raw material for the manufacture of paper products. World wide annual production of paper pulps amounts to 123 million tons with a market value of approximately 50 billion ECU. Chemical pulps are important commodities for the industrialised countries of the European union: Scandinavian countries and countries in Southern Europe, such as Portugal, are chemical pulp exporters, whereas countries such as the United Kingdom and Germany, which only have marginal chemical pulp productions, are importers of chemical pulp. Optical and strength properties are crucial parameters for the technological suitability and product quality as well as the pricing of paper pulps. Both property criteria are influenced by the digesting and bleaching technologies applied.

Recently the European chemical pulp industry has successfully focused on the elimination of chlorine from these processes. The considerable improvements thus achieved in non-polluting production and products are accompanied by changes in the technological behaviour of chemical pulps, especially in terms of strength, brightness and chemical reactivity. Regrettably, the methods used for evaluating the physical properties lag behind the advanced pulping technologies: the standardised equipment for classifying laboratory beating methods dates back to the years 1923 (Valley-Beater), 1930 (JOKRO-Mill) and to 1948 (PFI-Mill).

Available data sheets of market pulps which ought to characterise their real technological potential in the paper-making and converting processes are still exclusively based on investigations with conventional equipment. Some typical shortcomings of these methods are substantial differences in energy transfer mechanisms and amount of specific refining energy as compared to industrial refining machinery, quasi-stationary treatment of pulp in small-sized process jars and too inflexible process parameters. Simulating laboratory refining equipment and methods employing lab-scale refiners thus appear to be a viable alternative. The following distinct advantages of these machines permit close-to-reality assessments of the refining behaviour of pulps:

• measurement of specific energy consumption
• variation of refining intensity via precise control of refiner edge loads
• flexibility of process parameters
• option to test new configurations and/or materials of refiner fillings

In this context, recommendations for methods and parameters for the simulation of industrial refining processes with laboratory refiners were elaborated. The proposed harmonisation of parameter ranges for simulating laboratory refining will help to make simulating lab refiners a more effective tool for the optimisation of energy and material consumption in the paper and board industry. Future commercial data sheets for market pulps should not only be based on evaluations classifying beating-equipment or methods, but also evaluations of pulp property. This should be done according to the recommendations for simulating refining in the laboratory that were drawn up as one of the most important outcomes of the Concerted Action. The Concerted Action also resulted in the preparation of the following documents.

• Unification of terms, definitions and parameter ranges concerning the simulation of industrial refining processes.
• Present state of classifying laboratory beating/refining methods and conclusions for their future use.

In addition, it was suggested that the existing standards EN 25642-2 (laboratory beating based on PFI mill) and EN 2563-3 (laboratory beating based on Jokro mill) be revised. Furthermore, it was suggested to formulate a proposal for a CEN Report on laboratory refining and the simulation of industrial refining processes in particular.