ANDRITZ TX68 high-consistency refiner
Due to its modular design, the ATMP process can be implemented in stages during the rebuild of a conventional TMP (thermo-mechanical pulp) plant. Considerable research has been directed to the fundamentals of wood breakdown – specifically defibration (breaking the chips into fiber bundles) and fibrillation (creating the bonding surfaces) – to reduce the specific energy demand and improve the fiber bonding.
A traditional TMP plant attempts to accomplish defibration and fibrillation in the same primary refiner. The ATMP methodology demonstrates that these two tasks need different conditions in order to succeed. It is better to separate the two steps.
In the ATMP process, the first stage (RTFibration) is performed in a pressurized Impressafiner and a fiberizer (low specific energy refiner) to delaminate the wood chips into loose structures of fibers. With a large surface area, these bundles are perfect for targeted chemical treatment to attack the secondary fiber walls and improve the bonding characteristics in the next stage (high-intensity RTS refining).
Schematic drawing of an ATMP process
A 300-800 kWh/t energy saving for a given pulp tensile strength has been confirmed at mills running the combination of chemicals and mechanical treatment alone. The high energy efficiency and pulp quality at lower freeness in the primary stage requires less refining energy in the secondary and/or reject refining stages. Modern mills are using energy-efficient LC refiners which further reduce the specific energy consumption of the entire production line.
