A number of process variants have been established for the two methods. It is mainly the
temperatures at preheating and processing of the wood material that distinguish the different
methods. Groundwood pulps (GWD) have for a long time been produced in non-pressurised
systems. In more recent systems the logs are preheated and processed under pressurised steam.
The temperature in systems for production of pressurised groundwood (PGW) can vary from
100 °C to 140 °C. Refiner pulp is usually produced in a so-called thermomechanical pulping
wood magazine
water
stone
motor
stator
rotor
chips in
feeder
motor
stator
rotor
rotating discs pulp out processes (TMP)