The control strategy of the paper machine. Varying refiner positions (1st stage, 2nd

Stage, reject) also require different refiner plate designs. Refiner plate designs are

Always under further development, and some selected examples of actual plate

Design are illustrated in Fig. 4.34. Bi-directional refiner plates are standard in

TMP production, and perform independently of the direction of rotation of the

refiner. Turbine™ segments are the latest development by Metso Paper for the

Conical disc refiner RGP 82 CD (see Fig. 4.30); this system operates at low pressure

During chip defibration stage, and this results in improved optical properties

Of the refined pulp.

Refiner Processes

Fig. 4.34 Selected examples of refiner plate designs.

Refiner plates are hard-wearing tools with a working lifetime of between 300

And 1000 h. Selected examples of mechanical pulp lines using the refiner process

are shown in Figs. 4.35–4.37.

Fig. 4.35 Single-stage TMP line with Metso-Double disc

Refiners RGP 68DD (Union Bruk Norway, 1999).

Mechanical Pulping Processes

Fig. 4.36 Two-stage TMP line with two-stage reject refining

And fractionation for LWC paper (Metso Paper).

Fig. 4.37 Modern CTMP refining in one or two stages (Metso Paper).

To date, the production of pulp for fluting has been the most common use of

Semi-chemical hardwood pulps. The dominant process for this product is the neutral

Sulfite semi-chemical process (NSSC), with sodium or ammonium sulfite as

cooking chemicals. The pulp yield is in the range of 70–80% depending on the

Wood species. Birch, beech, maple, oak and eucalyptus are the most frequently

Used hardwoods for fluting production, often as the sole component in furnish.

Primarily, the demand on a fluting pulp is high stiffness and good crush resistance.

A combination of short, stiff fibers and a high proportion of hemicellulose

In hardwoods makes them more favorable than softwoods for this purpose. A

Semi-mechanical pulping process is illustrated schematically in Fig. 4.38.

Refiner Processes

Fig. 4.38 Semi-mechanical pulping process.

Processing of Mechanical Pulp and Reject Handling:

Screening and Cleaning

Jurgen Blechschmidt and Sabine Heinemann

5.1

Basic Principles and Parameters

The aim of mechanical defibration of wood is the deliberation of fibers from the

Wood, without their destruction. This happens only ideally, and in reality a mixture

Of different fiber components and debris is created immediately after defibration,

and is characterized as follows:

_ Shives (unsuitable particles that must be separated from the

Pulp).

_ Fibers, divided into:

– Long fibers; length 800–4500 lm; width 25–80 lm

– Short fibers; length 200–800 lm; width 2.5–25 lm

_ Fines, divided into:

– Fibrillar fines (slime stuff); length up to 200 lm, width about

Lm

– Flake-like fines (flour stuff); length 20–30 lm; width 1–30 lm

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