Drying 2004 – Proceedings of the 14th International Drying Symposium (IDS 2004) São Paulo, Brazil, 22-25 August 2004, vol. B, pp. 1319-1326 1319 DRYING CURVES GENERALIZATION IN CONDUCTIVE/CONVECTIVE DRYING OF CELLULOSE O. C. Motta Lima, M. Stenzel and N. C. Pereira Chemical Engineering Department , State University of Maringá Av. Colombo 5790 , Bloco D90 , CEP 87020-900 , Maringá - PR , Brazil Phone: (+55 44)261-4759 , Fax: (+55 44)263-3440 E-mail: oswaldo@deq.uem.br Keywords : Drying , Cellulose drying , Drying rates curves, Generalized drying rates ABSTRACT Aspects in the drying of cellulose sheets over a heated surface under natural and forced convection conditions are provided. The influence of the operational variables - samples initial moisture content, heated surface temperature and air velocity -, and the type of cellulose, on the conductive/convective drying process behavior is studied through a proposal of generalized drying curves. This methodology has the advantage of reducing the different curves representing the drying process to, respectively, only one generalized curve for the drying curves (generalized drying curves - GDC) and for the drying rate ones (normalized drying rate curves - NDRC). Samples materials are short- and long- fiber cellulose and the experiments are made inside an oven and with an apparatus which reproduces the operational conditions of the conventional paper dryers and consists of a metallic box heated by a thermostatic bath containing an upper surface (heated plate) on which the samples are placed. It is verified whether the proposal of generalization of the drying curves and the drying rate ones can be applied to all the drying results of the two types of cellulose, and, also, the possibility of fitting the generalized curves obtained adapting some of the models usually found in drying literature. INTRODUCTION This work presents a study related to some aspects in conductive/convective drying of cellulose sheets over heated surfaces under natural and forced air conditions, developed at the Separation Processes Laboratory (DEQ/UEM). The intention is to give a look in contact paper drying and to analyze the possibility of applying the drying curves generalization methodology to conductive/convective hot plate drying of short- and long-fiber cellulose under different operational conditions of initial paper moisture content, drying (heated surface) temperature and air velocity (natural and forced convection). This kind of approach is very interesting because it permits comparison of the results of different experiments by reducing them to only one set, which can be divided into two groups: the generalized drying curves (GDC), which relate a dimensionless moisture content (Y = X/X 0 ) to a dimensionless drying time