Method and apparatus for controlling cellulose processing

A method for controlling cellulose processing, characterized by

• performing first measurements of the cellulose during the processing, including:
• measuring drainability of the cellulose during the processing and monitoring a variation of drainage measurements, or
• measuring optically a size of particles in the cellulose during the processing;
• performing second measurements of the cellulose, including:
• first, directing optical radiation to the cellulose, the radiation comprising at least one beam that is polarized and at least one separate beam is non-polarized;
• second, measuring attenuations and parameters of polarization of the radiation interacted with the cellulose;
• and determining the size of particles in the cellulose based on at least one comparison of the parameters of polarization and the attenuations;
• and
• controlling the processing based on the first measurements until a given threshold of the first measurements, including the variation of drainage measurements or a predetermined size of the particles, has been reached and thereafter controlling the processing based on the second measurements.