NUMERICAL MODELING OF THE HEAT AND MASS TRANSFER PROCESS DURING DRYING OF COMPOSITE PELLETS

An urgent task at the current level of society's development is to preserve natural resources and the environment from pollution caused by human activity. It is necessary to preserve and increase the capacity of water and land recycling and reuse systems, develop waste-free and resource-saving technologies. The accumulated sludge deposits from wastewater treatment plants in large cities are outdated, having lost most of their nutrients, become too mineralized and practically unsuitable for direct use as fertilizers. The research is devoted to the development of a unified approach to the efficient processing of sludge sediments as fuel with the addition of flammable fillers such as milled peat and biomass. The aim of the study was to conduct research on drying composite raw materials based on obsolete sludge deposits and theoretical analysis of the heat and mass transfer process. The kinetics of the drying process of composite raw materials on an experimental convective drying bench with automatic data acquisition was studied. The studies show that at a coolant temperature of 80 °C, the drying time increases by about 1.4 times compared to 120 °C. The numerical simulation of convective drying of composite pellets showed that this model generally satisfactorily describes the nature of the change in the temperature in the center of the pellet and its moisture content over time during convective drying. In general, it can be noted that the considered model can be used for an approximate preliminary assessment of the drying time of a pellet made on a screw mechanical device in the proportion of 50% silt and 50% peat.