Fiber development in TMP main line

Esko Härkönen, Juha Kortelainen, Jukka Virtanen, Petteri Vuorio

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

35 Citations (Scopus)


A standard format for Thermomechanical Pulp (TMP) main line refining today is to install two refiners in series. Chips are fed into the first stage refiner and refined pulp suitable for further processing discharges from the secondary refiner. Two specific methods have been employed to study refining in a single two stage flat disc SD-65 refiner line. Samples were taken directly from different radial positions in the disc gap to monitor fiber development. Pulp residence time was measured with a radioactive tracer in order to obtain information concerning refining phenomena. Fiber development is explained in terms of radial position, residence time and temperature. At the inlet of the disc gap in the primary refiner, there is a zone of intensive mixing where pulp properties start to change. When pulp reaches the narrow disc gap in the primary refiner, freeness and fiber length are reduced, tensile and tear strength begin to develop and the fiber distribution is transformed towards finer fractions. In the secondary refiner inlet, there is a somewhat weaker mixing zone than in the primary refiner where fibers continue to develop and fiber properties change further as the pulp proceeds through this machine. Fiber development is related to the type of refining mechanism. This can be described as gentle or harsh and can be expressed in terms of refining intensity. When targeting energy savings in refining, the tendency is to apply higher refining intensity which equates to shorter residence time. In this paper, the development of fibers in an SD-65 refiner line has been analysed. In this connection, the influence of pressure and moisture content on the fiber residence time in the refiner has been measured. Measured values for important pulp physical and strength characteristics are shown for the primary and secondary refiner as a function of radial position within the refiner disc gap, providing more detailed information on the change of refining conditions in the refiner when operating conditions change.

Original languageEnglish
Title of host publication2003 International Mechanical Pulping Conference
Number of pages8
Publication statusPublished - 1 Dec 2003
MoE publication typeNot Eligible
EventInternational Mechanical Pulping Conference 2003 - Quebec City, Canada
Duration: 2 Jun 20035 Jun 2003


ConferenceInternational Mechanical Pulping Conference 2003
CityQuebec City


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