Evaluation of Thin-layer Models for Kinetic Analysis in Unbleached Kraft Pulpboard Drying

The drying characteristics of unbleached Kraft pulpboard have been studied in convective drying equipment under different hot air temperatures and velocities. In this work, the drying experiments were conducted in the range of 80-100℃ and 1.87-2.48m/s, respectively. The results indicated that high air temperature and velocity are beneficial to increasing drying rate and decreasing drying time. Ten thin-layer drying models were evaluated to describe the drying kinetic of unbleached Kraft pulpboard for its suitability. Based on the statistical analysis, the Yun model could predict the pulpboard drying kinetic better than others in terms of fitting performance. Through calculation and fitting, the effective moisture diffusivity varied from 2.077´10-10 to 3.631´10-10m2/s over the investigated temperature range and the average activation energy for moisture diffusion was 22.818 kJ/mol.