PILOTSCALE INVESTIGATION OF INFRARED DRYING OF PAPER

This investigation considers the infrared (IR) heat transfer mechanism taking place in IR paper drying. A mathematical model was developed t o calculate the IR energy density impinging onto the paper sheet, to e valuate the penetration of the IR rays into the paper sheet, and to ca lculate the IR absorption by the paper sheet. Experimental results, ob tained with a pilot-scale machine using a gas-fired IR dryer, show tha t the evaporation rate generally decreases with time as the paper shee t passes through the drying section. A higher IR emitting surface temp erature leads to a higher evaporation rate but to a lower drying effic iency. The paper temperature, measured under the operating conditions studied, is well below 100 degrees C, and it can be effectively contro lled by manipulating the blowing air velocity or the IR emitting surfa ce temperature. The surface brightness of a pdper sheet, dried with IR energy, can be lowered by about 1 point as the moisture content is de creased to about 0.1 g water/g fiber.