EXPERIMENTAL SUBSTANTIATION OF THE STIMULATION PAMETERS OF THE GRAIN CONVECTIVE DRYING BY RF-RADIATION

The target of the study was to determine the possibility of reducing the general energy intensity of convective grain drying in industrial installations, such as mine and drum dryers, with a capacity ranging from 2 to 50 tonnes per hour, by using small amounts of microwave energy before filling the product into the drying chamber. The experiments were performed in 2024 at the Russian State Agrarian University – Moscow Timiryazev Agricultural Academy. The subject of the research was an experimental unit that combined the effects of microwave radiation and convective heat on the product, with the criterion for energy efficiency being energy consumption per unit time. Wheat and rye seeds with different thicknesses were used as products, placed in "transparent" containers for both microwave and convection drying. The trays were placed on a conveyor belt and moved through a microwave chamber using an electric motor. The microwave energy was supplied to the chamber from two sides, from two magnetron sources that operated in pulsed mode and in antiphase. After passing through the microwave chamber, the trays moved to a convection drying chamber, where warm air was blown onto the product from below. This process simulated the convective drying process used in industrial drying facilities. In the first set of experiments, we used a product with a weight of 3 kg and a humidity range of 28–32 %. The product was placed in the convection drying chamber and dried to a moisture content of 12 %. This moisture content corresponds to the requirements for grain storage according to GOST. To determine the energy consumption for drying, we conducted a series of experiments. During these experiments, we adjusted the power of the heating element, which was set at 5 kW. Then, the drying time and energy intensity of the process were determined. The results ranged from 8.5 to 9.5 kW per hour per kilogram of moisture evaporated. In a subsequent series of experiments, the same amount of grain was first exposed to microwave radiation at a level of 1–5 % convective heat energy. The tray with the product was then moved on a conveyor belt to a convective drying chamber, where it was dried to a moisture content of 12 %. Based on the calculated weight reduction of the product during drying, total energy consumption ranged from 6.8 to 7.8 kWh per kilogram of moisture evaporation when adding 1 % microwave power to the drying process. This value ranged from 6.2 to 7.0 kWh at 5 %, resulting in an average reduction in energy use of 19–27 %. These findings indicate the potential for using low-intensity microwave radiation in industrial grain dryers.

microwave heating, magnetron generator, convective drying, combined drying, grooved waveguide, grain drying