Exjobbsförslag från företag

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Förslaget inkom 2003-03-25

On-line method to study paper formation in the wet-end of a paper machine ¿ Extension to on-line measurement of fibre orientation

Despite its long history, the basic principle of paper manufacturing has not changed and is still based on letting a fibre suspension in water settle on a permeable surface, which traps the fibres but allows water to pass. As water is removed, the fibres form a network that, after pressing and drying, becomes a paper sheet. The fibre suspension emerges from the headbox as a 5-10 m wide and 1 cm thick plane liquid jet, with typical velocities of 10-35 m/s. The jet impinges on one or two permeable moving wires through which water is drained. Thereupon, the wet web is mechanically pressed between two counter-rotating cylinders, thereby removing most of the unbound excess water. In a third step, the pa-per web is passed over steam-heated cylinders, where most of the remaining water is evaporated.

The formation of the final paper sheet, i.e. the variation of basis weight, is to a large extent determined by the conditions in the headbox. However, the impact of the forming jet on or between the wire(s) are also of importance as well as the effect of blade-dewatering, which has been show to promote a good formation under the right circumstances.

An on-line technique to measure formation in the wet end of a paper machine has been developed and implemented at STFI. The goal of this Master¿s thesis project is to develop the technique further, aim-ing at the implementation of on-line measurement of fibre orientation. The experimental work will start at laboratory scale and it will continue on EuroFEX, STFI:s research papermachine, where the industrial applicability of the method can be studied in realistic conditions.

· Improvement of measurement technique ¿ extension to on-line measurement of fibre orientation.
· Automation of signal processing and data handling, preferably to a real-time application (tenta-tively LabVIEW).
· Experiments a laboratory scale.
·Measurements at EuroFEX.

Preliminary plan:
1st month Literature review
2nd-4th month Implementation of the measurement technique.
Introductory tests at laboratory scale
4th month Test on the EuroFEX papermachine
5th month Report writing

The thesis should preferably be written in English.


STFI is one of the world¿s leading R&D organizations with its main activity in the field of pulp and paper. Cutting-edge competence in a number of scientific areas makes STFI an attractive partner. STFI constitutes a focal point in several international networks comprising other research institutes, universities, and industrial partners. This position makes STFI a highly attractive workplace. Internationally recognized senior scientists and younger engineers and researchers contribute to the excellence and dynamics of STFI.
STFI works both in long-term core competence research and in contract research, often of more applied nature. STFI provides industry with services such as pilot-machine trials, analysis and testing services, as well as a number of information and database services. STFI is also closely involved in standardization work. STFI combines academic depth with knowledge of industrial realities into applications in mills.

One of STFI¿s major assets in research and education is EuroFEX, a full-scale advanced research paper machine. The EuroFEX is complemented by among others a dynamic paper web test machine, a fractionation system, refiners, and advanced analytical instruments, in all ¿ a unique testing facility.

STFI has served as a major provider of highly trained specialists for industry for half a century. Many executives in pulp and paper, R&D and production personnel all over the world have been trained at STFI.

STFI is situated in Stockholm, adjacent to the Royal Institute of Technology (KTH), near Stockholm University.

STFI has approximately 230 employees, 130 of whom have university degrees.


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