Towards a New Sensing Strategy for Measuring Paper Pulp Properties: a Combination of Ultrasonic and Optical Measurement Techniques

ii To my family... iv In the manufacturing process of paper the mass fraction and material properties of the fibres in the pulp suspension are important for the strength and quality of the finished product. The properties of the fibres in the pulp suspension that enters the paper machine is not well understood and therefore an adequate prediction of the strength and quality of the finished paper is not possible. Also with the demand for a more environmentally friendly process the amount of recycled paper that enters the process has increased. The properties of the recycled fibre are unknown and also vary. Thus, the pulp suspension contains fibres of different sizes, mechanical properties and from fibres with different origin. The pulp and paper industry is a highly energy consuming industry. Therefore to be competitive on the world market the energy consumption needs to be reduced. Altogether, there is an increasing demand for methods of on-line characterisation of th