Experimental study on the drying kinetics of thick porous biobased fibrous materials

In this thesis, drying of thick porous biobased fibrous materials is studied. Laboratory scale drying experiments are performed in VTT Jyväskylä, Central Finland. Drying is investigated by drying foam-formed fibrous materials made from wood pulp(s), water and surfactant (SDS). The objectives are to find efficient drying method(s) that suit for thick porous bi-obased materials, could use renewable energy sources and investigation of quality of the fiber structures during drying.
The research consists of literature and experimental parts. Literature part focuses on foam forming and used raw materials, primary energy trends and its effect on selected drying methods in the future and fundamentals of drying through heat transfer methods, phases of drying and examples of selected drying methods. Experimental part focuses on air impinge-ment and microwave drying performed on a laboratory scale.
The most promising results from investigated drying methods gave the microwave drying. Over 4-times higher momentarily drying rates and 18-times higher average drying rates were reached with microwave drying compared to impingement drying. The quality control of the samples tended to be quite difficult with both drying methods, but even more difficult with microwave drying. Surface tended to expand and collapse due to fast temperature and pres-sure increase caused by microwaves and structures of some samples were destroyed. In-creased sample consistency was found to increase the sample resistance.