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 energy consumption and improve the fiber bonding. While accomplishment of defibration and fibrillation in the same primary refiner is attempted in a traditional TMP plant, the ATMP methodology demonstrates that these two tasks need different conditions in order to succeed and that It is better to separate the two steps. After liberating the S2 cell wall layer of the individual fibers with RTF-pretreatment, the fibre surface is modified by a low dosage of acid bi-sulfite, which enhances the fibre bonding properties and the brightness, and significantly improves the quality-to-energy ratio (Andritz, 2010).
In the ATMP process, the first stage ( RTFibration ) is performed in a pressurized Impressafiner (screw press) 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 well-suited for a targeted chemical treatment to attack the secondary fiber walls and improve the bonding characteristics in the next stage (high-intensity RTS refining). 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. With the use of energy-efficient LC refiners, further reductions in specific energy consumption of the entire production line are possible.The first commercial installation of a complete ATMP system is completed in March 2011 in a UPM Kymmene Austria GmbH plant located in Steyrermühl .