Plant Waste Drying in an Isothermal Model

Abstract

The paper highlights advantages of using furnaces for processing vegetable waste, including the absence of condensation, minimal ash production, stable coolant temperature, and efficient heat exchange. To improve this machine and intensify the drying process, it is necessary to gather data on the heat and mass transfer characteristics during high-temperature drying of moisture-laden particles. Due to the inherent challenges of studying the drying process in a real furnace, the experiment was conducted using an isothermal (cold) model under laboratory conditions closely resembling real-world processes. (Research purpose) The research aims to assess the effectiveness of the proposed aerodynamic models for drying plant waste and validate the mathematical model for drying particles in a suspended bed. (Materials and methods) The study employs two suspended bed models with distinct vortex flow aerodynamics (flare and cyclone) in combustion chambers. The study investigates the drying kinetics of two specific fractions of sunflower husks, each with an equivalent particle diameter of 0.25 and 1.5 millimeters, and initial moisture levels of 15 and 18 percent. At various time intervals, measurements were taken for both the temperature and humidity of the husk particles, in addition to recording the temperature and relative humidity of the drying agent as it exited. The drying process operated in a cyclical mode. (Results and discussion) When the sunflower husk particles had an initial moisture content of 15 percent, two phases of increasing drying rates were observed, while at an 18 percent moisture content, three such periods were identified, with the first period displaying a constant rate. The results suggest that when the husks start with an initial moisture content of 15 percent, the drying curves exhibit minimal linear segments. This observation implies that the process is occurring as the drying rate decreases. (Conclusions) The experiment reveals the most effective drying mode in terms of intensity. It becomes evident that both the flarevortex and cyclone-vortex aerodynamic modes facilitate particle drying, with the cyclone-vortex mode delivering a notably more intense drying process. When transitioning from a model to a real-world process, it is essential to undertake a comparison of estimated processes with practical operational conditions, as exemplified by the particle drying model in a suspended bed.