1.3 Synchrotron measurements of sulphonation homogenity on single fiber level form Chemical Thermo Mechanical Pulp (CTMP)
In order to improve process efficiency, one of the key parameters during CTMP impregnation is to prevent uneven distribution of sodium sulphite (Na2SO3). Hence measurements of sulphur distribution on single fibre level has been performed at the synchrotron facility APS, Advanced Photon Source, at the Argonne National Laboratory in the USA. Elemental mapping images of several different CTMP samples are retrieved by using a synchrotron beam with one micrometer scanning step. Depending on the chemical pre-treatment of wood chips and temperature, pressure profile and refiner conditions, the position in the fibre wall where the fibre-fibre separation takes place will differ. Some fibre surfaces are exposed to lignin while other will have minor lignin contact, which might cause uneven sulphur distribution within single fibres. On a larger scale, fibres from the outer parts of the wood chips have more impregnation than the fibres coming from the inner part of the same wood chip. Significant uneven distribution of sulphur between fibres are revealed in the images of CTMP samples. On individual fibre level, it is noticed that the sulphur impregnations is concentrated mainly in the fibre shell. Although the main focus is the Sulphur (S) distribution, other elements including Chlorine (Cl), Potassium (K), Calcium (Ca), Manganese (Mn), Iron (Fe), Copper (Cu) and Zinc (Zn) are analysed as well. One purpose to these synchrotron measurements is to verify a sulphur distribution measurements setup developed for use with an X-ray tube in lab or on site at a factory.