Simulation model for conditioning and casing processes in a rotary cylinder
The water content and the temperature of tobacco material in conditioning and casing processes affect the quality of tobacco products. It is necessary to clarify the mechanisms of the processes for improving quality and for designing the optimum apparatus. The purpose of this study is to develop a model for conditioning and casing to clarify the process mechanisms. Since actual processes are complex systems in which tobacco, moist air, and water and/or sauce droplets coexist, some simplified model is required for analysis. For that purpose, a rotary cylinder type test apparatus capable of batch processing was developed, and an aqueous glycerol solution was used as a casing sauce. Our model focuses on (1) the mass-enthalpy transfer among tobacco, moist air, water and/or sauce droplets and cylinder-wall, and (2) the one-dimensional diffusion of water along the thickness-axis of tobacco. The simulated values of the water content and the temperature of tobacco under the model were in good agreement with the experimental data. Moreover, the simulation clarified that (1) the heat of water adsorption onto tobacco in the early stage of conditioning contributes to the temperature rise of tobacco, and that (2) the conditioning by water adsorption reduces the water content distribution along the thickness-axis, compared with the water addition by nozzles.