An Experimental Study of the Falling Rate Period of Superheated Steam Impingement Drying

The drying of paper under impinging jets of superheated steam and air during the falling rate period was investigated in the range of jet temperatures 150 < Tj < 450oC and basis weights 30 < B < 150 g/m2. The equilibrium moisture content of Kraft and TMP paper was measured. The adsorption energy of water on pulp fibers near the boiling point appears lower than the value extrapolated from Prahl s (1968) measurements made in air at lower temperatures. The critical moisture content was determined for superheated steam and air impingement drying. Complete drying rate - moisture content histories are presented for a series of typical conditions.