Study On Multiphase Flow Transfer Of Tobacco Redrying Process

Tobacco is an important part of Chinese agriculture. Tobacco redrying is the transitional phase between agricultural products processing and cigarette manufacturing. Based on the desorption property of tobacco, tobacco is re-processed to make it beneficial to storage and further to conform to the requirements of the cigarette manufacturing. The encence of the drying of tobacco leaf in the redrying machine is hot air convection drying. Based on the existing dry mode, after studying on the drying kinetics of the tobacco leaf and heat transfer and mass transfer characteristics of the drying process, the computer is used to simulate dynamically each dryer in the drying process, which are respected to provide the basis dates for the tobacco drying (humidifying) theory research and tobacco redrying process parameters controllment.The features of drying kinetics of two flue-cured tobaccos were studied with an online device of heating-moisture treatment and tobacco adsorption and desorption device for analyzing. Drying experiments of strips were carried out under various temperature and relative humidity.The effective moisture diffusion coefficient and equilibrium moisture content under experimental conditions of temperature and humidity were determined. At the same time, according to the experimental data, the optimal thin layer drying equation and equilibrium moisture content model was determined with nonlinear fitting.The drying process was abstracted into corresponding physical and chemical process, and the total thermal-mass balance was determined for the drying chamber. At the same time, considering the influence of the external resistance, the modified biot number and the tobacco drying rate model were established. Based on the thermal-mass balance theory, the tobacco bed drying model was established with four differential equations excluding the mass balance equation, the heat balance equation, heat transfer equation and the drying rate equation. Using Fortran language, the simulation program for tobacco redrying progress was programmed. And the distribution of temperature and humidity of tobacco and drying medium (air) were obtained.