Investigation of the Operating Process of a Technological Module for High-Intensity Combined Thermal Treatment of Compound Feed Ingredients Using Convective and Microwave Heating

Introduction. Within the framework of the national project for accelerated livestock development, the modernization of feed preparation enterprises is becoming critically important. Improving feed quality and nutritional balance directly in-creases livestock productivity and mitigates human health risks. However, grain, animal, and mineral raw materials are highly susceptible to severe microbial spoilage, with molds posing a particular hazard due to their mycotoxins, which drastically reduce nutritional value. Combined convective-microwave treatment of grain and mineral raw materials ensures intensive starch dextrinization, 100% product decontamination, and a two-fold reduction in energy consumption. The objective of this study is to determine the rational combination of convective (up to 60 °C) and microwave heating (up to 95–105 °C) parameters within a technological module to ensure high-intensity thermal treatment of compound feed ingredients.

Materials and Methods. Hydrothermal treatment of grain is a complex heat and mass transfer process, wherein moisture migrates both within the material and from its surface into the environment, predominantly as a vapor-liquid mixture. During high-intensity thermal processing (e.g., infrared heating), rapid moisture evaporation occurs inside the grain, leading to a rise in vapor pressure and the generation of overpressure that disrupts the grain structure, causing its softening and puffing. This process is divided into two distinct periods: 1) heating up to 95–105 °C (the onset of vaporization); 2) heating above this temperature range, during which the primary qualitative transformations occur, including the elimination of microflora. For the first period, convective heating is proposed due to its simplicity and energy efficiency; for the second period, microwave heating is implemented to provide rapid, uniform heating and a sharp increase in vapor pressure. The overall efficiency of the combined treatment depends heavily on the integration of the process operating parameters.

Research Results. In laboratory studies, the convective heating of winter wheat grain and seashell flour was investigated. The temperature profiles of both stationary and moving beds were plotted as a function of processing duration. It was established that as the throughput increases, the discharge temperature of the materials decreases: for the grain (95–105 °C), the optimal throughput is 300–500 kg/h, whereas for the seashell flour (60–80 °C), it exceeds 650 kg/h. Furthermore, a correlation was identified between the throughput, specific energy consumption, and the clearance gap between the metering roller and the cutoff plate. Increasing this gap up to 4.5 mm reduces energy consumption by a factor of 2.0 to 3.5. These findings were subsequently applied to refine the engineering design documentation of the combined treatment technological module (convective + microwave heating) with a capacity of up to 400 kg/h.

Discussion and Conclusion. In the course of this research, the functional dependencies and the boundaries of design and technological parameters for preliminary convective heating during the processing of compound feed ingredients were determined. Based on these findings, the engineering design documentation was refined for the combined (convective and microwave) treatment module with a capacity of up to 400 kg/h.

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