An experimental study of gas-fired infrared drying of paper

Abstract

The concept of using an infrared (IR) source for drying proposes is not a new one, yet the application of this technology in the paper industry has been slow to gain acceptance. Recent advances in the design, construction, and controllability of natural gas-fired IR emitters allow for immense potential benefits to the paper industry. A dedicated test facility was designed and built in the Drying Research Center laboratories at Texas A&M University. This facility allowed for the real-time mass and internal temperature measurements for paper samples that were exposed to a single tile surface-burner IR emitter. After successfully validating the data collection capabilities and establishing testing procedures that produced consistent data, an experimental study was initiated. The lack of fundamental information explaining the transport phenomena occurring within a paper sheet due to energy supplied by a gas-fired infrared heater is the motivation for this experimental work. Mass and internal temperature measurements were made for fiberboard samples of basis weights of 500 to 100 g/m² and bleached fiber samples with basis weights of 300 to 100 g/m². The average drying rates of 18.81 g/sm² for the fiberboard corresponded to the heaviest basis weight for two seconds from initial exposure. The bleached fiber samples resulted in an average drying rate of 10.52 g/sm² for the lightest basis weight within four seconds of IR exposure time. Differences in the trends of the data were then further investigated through the addition of measurement of the internal temperature distribution. It was found that the fiberboard samples responded more quickly to the initial exposure of infrared while the bleached fibers had a slower initial reaction, but then dried faster as the exposure time increased. The final investigation focused on the effects of varying emitter parameters. Flame temperature, sample mass, and internal temperature measurements were made for various air/fuel ratios and overall fuel consumption rates. Peak flame temperatures resulted in the highest drying rate and the steepest internal temperature increases for a air/fuel ratio of 11:1 with a fuel consumption rate of 56.3 kW which corresponded to an emitter flux of 234.6 kW/m².