Numerical study on hygroscopic material drying in packed bed

Abstract

-The paper addresses numerical simulation for the case of convective drying of hygroscopic material in a packed bed, analyzing agreement between the simulated and the corresponding experimental results. In the simulation model of unsteady simultaneous one-dimensional heat and mass transfer between gas phase and dried material, it is assumed that the gas-solid interface is at thermodynamic equilibrium, while the drying rate of the specific product is calculated by applying the concept of a "drying coefficient". Model validation was done on the basis of the experimental data obtained with potato cubes. The obtained drying kinetics, both experimental and numerical, show that higher gas (drying agent) velocities (flow-rates), as well as lower equivalent grain diameters, induce faster drying. This effect is more pronounced for deeper beds, because of the larger amount of wet material to be dried using the same drying agent capacity.

Otimização Do Consumo Energético Da Secagem Do Crambe Em Um Secador De Leito Fixo

“…Utilizou-se o modelo de dupla resistência à transferência de massa para descrever o processo de secagem, empregado também nos estudos realizados por Stakić e Tsotsas (2005) na secagem de carvão industrial e cubos de batata por Stakić et al (2011).…”

Fluid bed drying as upgrading technology for feasible treatment of Kolubara lignite

“…With the intention to analyze convective drying in a packed bed, an unsteady-state 1-D mathematical model, already validated for different biological materials (corn grains, soybean, potato cubes, poppy seeds, etc., see [1][2][3][4]), was developed in the past. This model, describing simultaneous heat and mass transfer between the gas phase and the dried product during convective drying in a packed bed, rests upon the following assumptions: -drying parameters vary in 1-D only, namely in a direction of gas flow (usually vertical), and only changes of the parameters in this direction are addressed and discussed, -all solids are of the same size, shape, and density at one moment in time, -the gas-solid interface is at thermodynamic equilibrium, -the product drying rate is calculated by applying the drying coefficient principle, and -dispersion of mass or heat in the considered gas flow direction is neglected.…”

“…The main objective of the work presented in this paper is to provide a brief overview of the current status of low-rank coal upgrading technologies, particularly addressing utiliza---------------tion of drying technologies, as well as to propose appropriate calculation method for evaluating parameters of the coal pre-drying process. The packed bed drying model was developed in the past and validated for biological materials [1][2][3][4], but also successfully used to depict drying of Kolubara lignite [5]. The paper reflects on possible upgrades of this model so as to be suitable for simulation of the fluid bed drying process.…”

Theoretical and experimental drying of a cylindrical sample by applying hot air and infrared radiation in an inert medium fluidized bed

“…The Crank-Nickolson finite difference method was employed to solve the above equations for the temperature and moisture variation through time (Stakic et al, 2011).…”