Abstract
Knowledge of the drying properties of tobacco in high temperatures above 100 °C and its dust are crucial in the design of dryers, both in the optimization of the superheated-steam-drying process and in the correct selection of innovative explosion protection and mitigation systems. In this study, tobacco properties were determined and incorporated into the proposed model of an expanding superheated steam flash dryer. The results obtained from the proposed model were validated by using experimental data yielded during test runs of an industrial scale of a closed-loop expansion dryer on lamina cut tobacco. Moreover, the explosion and fire properties of tobacco dust before and after the superheated steam-drying process at 160, 170, 180, and 190 °C were experimentally investigated, using a 20 L spherical explosion chamber, a hot plate apparatus, a Hartmann tube apparatus, and a Godbert–Greenwald furnace apparatus. The results indicate that the higher the drying temperature, the more likely the ignition of the dust tobacco cloud, the faster the explosion flame propagation, and the greater the explosion severity. Tobacco dust is of weak explosion class. Dust obtained by drying with superheated steam at 190 °C is characterized by the highest value of explosion index amounting to 109 ± 14 m·bar·s−1, the highest explosion pressure rate (405 ± 32 bar/s), and the maximum explosion pressure (6.7 ± 0.3 bar). The prevention of tobacco-dust accumulation and its removal from the outer surfaces of machinery and equipment used in the superheated steam-drying process are highly desirable.
Highlights
Drying is a necessary process and the most energy-consuming step in tobacco production
This paper concerns modeling the drying process of tobacco that takes place in the expanding superheated steam dryer in order to predict the properties of tobacco in high temperatures above 100 ◦C and the efficiency of drying systems
Knowledge of the drying properties of tobacco and its dust is critical in designing a superheated steam dryer and optimizing production costs [9,10]
Summary
Drying is a necessary process and the most energy-consuming step in tobacco production. The tobacco is shredded, and the cut tobacco is dried again to its final moisture content. In this drying process, tobacco can be simultaneously expanded to increase its filling power (and so reduce tissue density). An ensemble of expansion tunnel and rotary dryers or a one-stage superheated steam expansion dryer (closed-loop expansion dryer (CLED)) are used [4] After this stage, the tobacco is conditioned again by adding some additional components (called sauces), which improve flavor and taste. The tobacco will no longer be dried in a dryer, but will only lose some moisture (1–2%) during the cigarette-making process. This paper concerns modeling the drying process of tobacco that takes place in the expanding superheated steam dryer in order to predict the properties of tobacco in high temperatures above 100 ◦C and the efficiency of drying systems
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