ISO/TS 11371:2023

Pulps - Guidelines for using laboratory refiners to simulate industrial low consistency refining

This document provides guidelines for the laboratory refining of various pulps intended for paper production including: - Harmonization of terms and parameters for the simulation of industrial refining processes by laboratory refiners; - Treatment of pulp samples in a (semi) continuous operation in contrast to the batch operation of laboratory beating equipment such as the PFI mill; - Evaluation of fibres for papermaking, in particular chemical market pulps, under close-to-reality conditions in terms of refining intensity and refining energy consumption. This document only considers refiners operating at low stock concentration, i.e. 3 % to 5 %.

Pâtes — Lignes directrices relatives à l'utilisation de raffineurs de laboratoire pour simuler le raffinage basse consistance industriel

General Information

• Status: Published
• Publication Date: 13-Jul-2023
• ICS: 85.040 - Pulps
• Technical Committee: ISO/TC 6 - Paper, board and pulps
• Drafting Committee: ISO/TC 6 - Paper, board and pulps
• Current Stage: 6060 - International Standard published
• Start Date: 14-Jul-2023
• Due Date: 10-Sep-2023
• Completion Date: 14-Jul-2023

Relations

• Revises: ISO/TR 11371:2013 - Pulps - Basic guidelines for laboratory refining
• Effective Date: 06-Jun-2022

Overview

ISO/TS 11371:2023 - "Pulps - Guidelines for using laboratory refiners to simulate industrial low consistency refining" provides harmonized guidance for using laboratory refiners to reproduce mill-scale, low-consistency refining conditions. The technical specification focuses on simulating industrial refining in (semi)continuous operation for pulps intended for paper production, particularly chemical market pulps, and limits refining to low stock concentrations (3%–5%). It updates terminology, refining parameters, and laboratory procedures to give more realistic evaluation of fibres than traditional batch beating (e.g., PFI mill).

Key Topics

• Terminology and machine parameters: Definitions of total load power, no‑load power, net refining power, rotational and tangential speeds (units in kW, 1/min, m/s).
• Refiner fillings and geometry: Rotor and stator, bars and grooves, bar widths, cutting edge length (CEL) and cutting length factor (CLF).
• Process parameters: Refining gap, stock concentration, flow and mass flow rates, refining time, and measures of refining energy.
• Refining intensity and energy metrics: Discussion of Specific Edge Load (SEL), Specific Surface Load (SSL), Modified Edge Load (MEL) and C‑Factor Theory as ways to describe intensity in addition to net specific refining energy (kWh/t or kJ/kg).
• Laboratory refining procedures: Guidance on (semi)continuous treatment vs batch beating, pulp preparation, determination of no‑load power (in water and in pulp suspension), measurements, maintenance and quality assurance.
• Basics of refining effects: How refining alters fibre properties (external/internal fibrillation, shortening, fines generation) and consequent sheet properties (drainage, strength, bulk, optics).

Applications / Who Should Use It

• Mill process engineers and R&D teams seeking to simulate industrial low‑consistency refining in a laboratory setting.
• Pulp and paper laboratories performing fibre evaluation, product R&D, or process optimization.
• Pulp suppliers and quality control laboratories comparing pulps under close‑to‑real refining conditions.
• Equipment manufacturers and test labs that need standardized definitions and procedures for laboratory refiners and energy/intensity reporting.

Practical uses include comparing pulp refining responses, estimating refining energy consumption, optimizing refining intensity for desired sheet properties, and harmonizing lab-to-mill correlations.

Related Standards

• ISO/TS 11371:2023 replaces and revises ISO/TR 11371:2013 and was prepared by ISO/TC 6 (Paper, board and pulps).
• The specification is intended to complement existing test methods for beating and refining; users should consider laboratory accreditation and national adoption documents when implementing procedures.

Keywords: ISO/TS 11371:2023, laboratory refiners, low consistency refining, pulps, refining intensity, specific refining energy, SEL, SSL, MEL, C‑Factor.

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 11371
First edition
2023-07
Pulps — Guidelines for using
laboratory refiners to simulate
industrial low consistency refining
Pâtes — Lignes directrices relatives à l'utilisation de raffineurs de
laboratoire pour simuler le raffinage basse consistance industriel
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
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Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Machine parameters . 1
3.2 Refiner fillings parameters . 2
3.3 Process parameters . 4
4 Basics of pulp refining . 5
5 Refining intensity . 6
5.1 General . 6
5.2 Specific Edge Load (SEL) . 6
5.3 Specific Surface Load (SSL) . 7
5.4 Modified Edge Load (MEL) . 8
5.5 C-Factor Theory . . 8
6 Pulp types and properties .9
7 Laboratory refining procedures .10
7.1 Refining parameters . . 10
7.2 Pulp preparation . 11
7.3 Refining system . 11
7.3.1 General . 11
7.3.2 Determination 1 of no-load power using water.12
7.3.3 Determination 2 of no-load power using the pulp suspension .12
7.4 Measurements . .13
7.5 Maintenance . 13
7.6 Quality assurance . 13
Bibliography .15
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
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database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.
This first edition of ISO/TS 11371 cancels and replaces ISO/TR 11371:2013, which has been technically
revised.
The main changes are as follows:
— the focus lies exclusively on simulating industrial refining with laboratory refining;
— the basics of refining are further elaborated;
— Clause 3 has been updated;
— the refining procedures have been reviewed and detailed;
— the clause on pulp preparation and the two annexes have been removed.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
It is well known that the current standardized method (PFI mill method) for beating has only limited
value in the evaluation of pulps. It was originally developed for quality control purposes and has no
counterpart in real mill operations since the fibre property development is based on a different
principle.
The biggest shortcomings are the following:
— The refining principle is different from mill-scale refining processes (controlled by energy
consumption, refining intensity);
— No possibility to adjust refining parameters for specific pulps;
— No direct measure for specific energy consumption;
— Not consistent and correct usage of terms.
This well-known standardized method has good reproducibility and repeatability and the equipment
is easy to handle. Nevertheless, many laboratories have replaced this method by the use of refiners
enabling them to simulate industrial refining and to allow the evaluation of pulps for various mill-scale
refining applications.
The objective of this document is to address the related topics by providing a common basis with regard
to refining parameters, definitions, and procedures.
v
TECHNICAL SPECIFICATION ISO/TS 11371:2023(E)
Pulps — Guidelines for using laboratory refiners to
simulate industrial low consistency refining
1 Scope
This document provides guidelines for the laboratory refining of various pulps intended for paper
production including:
— Harmonization of terms and parameters for the simulation of industrial refining processes by
laboratory refiners;
— Treatment of pulp samples in a (semi) continuous operation in contrast to the batch operation of
laboratory beating equipment such as the PFI mill;
— Evaluation of fibres for papermaking, in particular chemical market pulps, under close-to-reality
conditions in terms of refining intensity and refining energy consumption.
This document only considers refiners operating at low stock concentration, i.e. 3 % to 5 %.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Machine parameters
3.1.1
total load power
P
tot
power provided to the refiner during refining of a fibre suspension to modify fibre properties and
overcome friction and the pumping effect
Note 1 to entry: It is expressed in kW.
3.1.2
no-load power
P
power required to overcome friction and the pumping effect measured in water or fibre suspension (at
refining stock concentration) in defined conditions for flow and open gap
Note 1 to entry: It is expressed in kW.
3.1.3
net refining power
P
net
difference between total load power and no-load power
Note 1 to entry: It is expressed in kW.
3.1.4
refiner rotational speed
n
revolutions of the refiner rotor per minute or per second
Note 1 to entry: It is expressed in 1/min or 1/s.
3.1.5
tangential speed
v
speed of the rotor at the outer diameter of the refining zones of the refining elements at a defined
refiner rotational speed
Note 1 to entry: It is expressed in m/s.
3.1.6
average tangential speed
ῡ
tangential speed of a point at half-length of the refining zones of the refining elements at a defined
refiner rotational speed
Note 1 to entry: It is expressed in m/s.
3.2 Refiner fillings parameters
3.2.1
filling
exchangeable plates used for fibre treatment (refining), including a stationary element (stator) and a
rotating element (rotor) in the form of a disk, cone or cylinder with bars and grooves
3.2.2
rotor
motor-driven (rotating) refiner filling
3.2.3
stator
stationary refiner filling
3.2.4
bar
one of a number of structures of rectangular cross-section on the active surface of the rotor and stator
filling
Note 1 to entry: It may be cast, fabricated or machined into the surface of an element. The bars cause the refining
of fibres (see Figure 1) and transport of the fibre suspension.
3.2.5
bar width
b
r,s
width of a single bar at the bar surface (rotor or stator)
Note 1 to entry: It is expressed in mm.
3.2.6
number of stator bars
z
s
total number of stator bars on the refiner filling
3.2.7
number of rotor bars
z
r
total number of rotor bars on the refiner filling
3.2.8
average rotor bar angle
α
r
angle formed between the rotor bars and the radius for disc fillings
Note 1 to entry: It is expressed in °.
3.2.9
average stator bar angle
α
s
angle formed between the stator bars and the radius for disc fillings
Note 1 to entry: It is expressed in °.
3.2.10
average cutting angle
ϕ
sum of the average rotor bar angle and the average stator bar angle
Note 1 to entry: It is expressed in °.
3.2.11
cutting edge length
C
EL
CEL
total length of all bar edges at a defined refiner rotational speed
Note 1 to entry: It is expressed in km/s.
3.2.12
cutting length factor
C
LF
CLF
total length of all bar edges for one complete rotation of the rotor
Note 1 to entry: It is expressed in m·min/s.
3.2.13
grooves
channels between bars
3.2.14
groove width
g
distance between two bars (rotor or stator)
Note 1 to entry: It is expressed in mm.
3.3 Process parameters
3.3.1
refining gap
distance between the top surfaces of rotor and stator bars
Note 1 to entry: It is expressed in mm or μm.
3.3.2
refining time
period of time from the start of refining to sampling or interval between two samplings
Note 1 to entry: It is expressed in min or s.
3.3.3
stock concentration
c
ratio of the oven-dry fibre mass that can be filtered from a stock sample, to the mass of unfiltered
sample
Note 1 to entry: It is expressed in %.
3.3.4
flow rate
f
fibre suspension flow rate through the refiner
Note 1 to entry: It is expressed in l/h, l/min, l/s or m /h.
3.3.5
mass flow rate
F
fibre mass flow rate through the refiner
Note 1 to entry: It is expressed in kg/s or t/h.
3.3.6
refining intensity
I
how force is transferred to the fibre
Note 1 to entry: See Clause 5.
3.3.7.1
net specific refining energy
S
RE
SRE
net refining power per oven-dry mass flow rate of fibre
Note 1 to entry: It is expressed in kWh/t or kJ/kg.
3.3.7.2
total specific refining energy
S
RE
SRE
total refining power per oven-dry mass flow rate of fibre
Note 1 to entry: It is expressed in kWh/t or kJ/kg.
3.3.7.3
net specific refining energy
S
RE
SRE
product of the net refining power and the time for which it is applied per oven-dry
mass of fibre
Note 1 to entry: It is expressed in kWh/t or kJ/kg.
3.3.7.4
total specific refining energy
S
RE
SRE
product of the total refining power and the time for which it is applied per oven-dry
mass of fibre
Note 1 to entry: It is expressed in kWh/t or kJ/kg.
4 Basics of pulp refining
Fibres usually need treatment to meet the required paper or board quality. Refining is the most
important process step for achieving this, which it does by modifying the fibre properties.
The main purpose of refining is to improve the bonding ability of the fibres. Depending on the product,
this is required to increase strength, enhance runnability, increase stiffness, improve printing
properties, modify porosity or increase transparency, or a combination of these. It can also be used to
improve sheet formation by reducing the length of fibres, which are too long, or to modify some other
paper property.
The most common refining method for chemical pulps is to treat the pulp suspension at low stock
concentrations using metallic bars according to the bar-to-bar principle (Figure 1). The bars are
attached to elements knows as fillings, a stationary element (stator) and a rotary element (rotor). The
pulp fibres pass through the gaps between the rotor and the stator bars receiving impacts, which can
be varied in number and intensity. In industrial refiners, the refiner fillings can be disks, cones, or
cylinders.
Key
1 stator
2 rotor
3 refining gap
Figure 1 — Bar-to-bar refining principle
Refining affects fibres in several ways. The most common effects are as follows:
— External fibrillation;
— Internal fibrillation (changes in the fibre walls, swelling, and delamination);
— Cutting of the fibres;
— Fines generation by removing parts from fibre walls;
— Straightening of the fibres;
— Creating or removing kinks, nodes, or micro compressions in the fibre walls;
— Dissolving or leaching out colloidal material into the water phase.
As a result, the fibres become more flexible and conformable and their bonding area increases. This is
reflected in the pulp and sheet properties as follows:
— Rate of water removal during sheet forming is decreased (drainage resistance increased);
— Strength properties are promoted (tensile properties, burst, Z-directional strength and fracture
toughness are increased);
— Tearing resistance is increased or decreased depending on fibre characteristics and the extent of
refini
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