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Mechanical pulping

CTMP (chemi-thermomechanical) pulping

The CTMP (chemi-thermomechanical) pulping processes provide excellent bulk properties of paper at a high production capacity. The key sub-processes in CTMP pulping cover all the way from chip preparation, high-consistency refining, steam recovery, fractionation, treatment of long fiber fraction, bleaching and dewatering to pulp storage prior to papermaking process or drying and baling for market pulp. The use of CTMP pulps is continuously spreading into new end-use applications and combinations. At the same time, new and better process technologies and equipment for bleached chemi-thermomechanical (BCTMP), chemi-mechanical (CMP), semi-chemical (NSSC) and non-wood fiber applications are being developed.

TMP (thermomechanical) pulping

TMP (thermomechanical) pulping processes provide excellent strength related properties of paper at a high production capacity. The key sub-processes in TMP cover all the way from chip preparation, high-consistency refining, steam recovery, fractionation, treatment of long fiber fraction, bleaching and dewatering to pulp storage prior to papermaking process or drying and baling for market pulp. TMP process can consist of single stage, two or three refiners in a series in one production line supplying paper machine, and the TMP pulp is dewatered and stored before papermaking.

NSSC (Neutral Sulfite Semi Chemical) pulping

NSSC (Neutral Sulfite Semi Chemical) pulping is a type of semi-chemical pulping process to produce unbleached pulp at yields of around 80%. Hardwoods are normally used as raw material and the produced pulp is mainly used for production of corrugating medium (fluting). Chips are impregnated with sulfite and carbonate at neutral pH, cooked for about 30 minutes at around 170-180 °C, defibrated to coarse pulp in a refiner, washed and finally refined to obtain an optimum combination of strength and stiffness. The total specific energy consumption in defibration and refining is normally less than 200 kWh/t. The spent liquor is normally sent to a kraft mill for recovery of chemicals and heat (cross-recovery).

PGW (pressurized groundwood) system

PGW (pressurized groundwood) system utilizes roundwood as raw material. PGW main sub-processes include grinding, screening, reject treatment, bleaching, dewatering and storage. The PGW process is unique in allowing separate choice of pulping temperature and pressure. As a result, it is possible to customize pulp properties according to specific paper quality requirements. The PGW process is highly automated, featuring automatic log feed, extensive control and information systems as well as online measurement. The WaterJet pulp-stone conditioning system is used as an improvement on traditional burr sharpening of a pulp stone. For producers of wood-containing printing papers, visual quality improvement is the key to satisfying customer needs. Valmet’s pressure grinders and complete PGW processes produce mechanical pulps for products of the highest final quality – and with the lowest energy consumption and environmental load.