Method for optimizing the refining energy during an operation of refining of a fiber composition

A method of optimization of the refining energy supplied by a refiner to a fiber composition during a refining operation, the refiner comprising at least two refining disks separated from each other by an adjustable gap, said method comprising the following steps:

• a) setting an initial refining energy set point,
• b) measuring a vibration of the refiner, to obtain a corresponding vibration signal which depends on the gap,
• c) comparing at least one characteristic of the vibration signal with a determined maximum value and a determined minimum value so as to:
• c1) if the characteristic of the vibration signal is lower than the maximum value and higher than the minimum value, resume the method from step b),
• c2) if the characteristic of the vibration signal is higher than or equal to the maximum value, automatically decrease the initial refining energy set point down to a lower set point value, and automatically increase the gap so that the refining energy tends towards the lower set point value, and
• c3) if the characteristic of the vibration signal is lower than or equal to the minimum value, automatically increase the initial refining energy set point up to a higher set point value, and automatically decrease the gap so that the refining energy tends towards the higher set point value,
• wherein the lower set point of step c2) or the higher set point of step c3) is kept constant for a time interval of at least 5 seconds, whatever the vibration measured during said time interval, and
• wherein the characteristic of the vibration signal comprises an acceleration of the refiner.