Empirical validation of a comprehensive zero-dimensional model for lignite water evaporation

The purpose of this paper is to conduct a theoretical and experimental study of lignite drying to determine the effect of drying on the moisture content of lignite. Based on the experimental study, the theoretical model of coal drying, regarding mass exchange, i.e., moisture loss in the initial stage of drying, was verified. The following results were obtained: a mathematical model of drying was proposed and experimentally verified by conducting evaporation measurements of water droplets and coal particles. A parametric analysis of the effect of drying air temperature and drying air velocity on moisture evaporation was carried out using Frossling's equation. It was demonstrated that a reduction in evaporation time within a certain range of low temperatures is achieved by increasing the air velocity. At higher temperatures, the drying air temperature has a greater effect on the evaporation rate of water from coal. The results are presented in the form of an easy-to-read graph, showing isolines of the constant flux of evaporated water as a function of drying air velocity and temperature. A very simple linear model of water evaporation (drying kinetics) is proposed by author (equation 18), which can be used to analyze the kinetics of water evaporation under constant conditions of air temperature and air velocity. The model can be easily parameterized experimentally for any type of coal.