The industrial production of RMP began in 1960, since which time the refiner

Process has been extensively developed as result of the increasing demand for

Pulp fibers and the commissioning of large and highly efficient paper machines.

The advantages of refiner processes can be summarized as follows:

_ Chips as a raw material allows the processing of wood that cannot

Be used for grinding (size of the logs, wood species), for example,

Saw mill chips or sawdust. With chemical pretreatment, some

Hardwoods can also be used successfully.

_ There are good possibilities of process automation and minimal

Operating effort. Wood transportation and log handling are no

Longer necessary.

_ Pulps with a high content of long fibers and good strength properties

Can be produced.

Mechanical Pulping Processes

_ The quality of the mechanical pulp produced is constant over a

Longer time interval than for groundwood, because there are no

Sharpening fluctuations.

The development of the refiner process has been enforced by much better designs

Of the refiners, highly efficient refiners, and the development of wear-resistant

Plate materials.

4.2.2

Mechanical, Thermal, and Chemical Processes in the Refiner Process

Fiber deliberation from the fiber compound can occur in the refiner process as

follows:

_ Softening of the lignin in the middle lamella and in the primary

Wall of the wood fiber by pressure load frequencies in the refiner;

This is mechanical softening.

_ Softening of the lignin in the middle lamella and in the primary

Wall of the wood fiber by thermal influences; this is thermal softening.

_ Softening of the lignin in the middle lamella and in the primary

Wall of the wood fiber by chemical pretreatment; this is chemical

Softening.

Many process parameters are considered responsible for the character and properties

of the mechanical pulp produced, including: (a) the pressure and temperature

During thermal pretreatment; (b) the duration of thermal pretreatment; (c) the

Addition of chemicals; (d) the specific energy consumption; (e) the energy distribution

Within the refining stages; (f) the consistency in the refining zone of the

First refining stage; (g) the wood chip quality; (h) the refiner design; and (i) refining

Intensity caused by plate design and rotational speed.

The duration of thermal pre-treatment has only minimal influence on pulp

quality, since in practical terms this stage lasts for only 1–3 min, and a minimum

Time is striven for.

The defibration temperature is as important as for the grinding process, and

should be 100–130 °C. By raising the temperature to 140 °C, the lignin becomes

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