Technological Progress and Equipment R&D in Graphene Far-Infrared Grain Drying
China suffers serious post-harvest grain losses, with mildew and sprouting deterioration causing an annual rice loss of approximately 35 million tons. Mechanical drying is a key step for loss reduction and quality preservation. However, China's drying segment lags behind its harvesting segment, with unbalanced development between the North and the South. Traditional hot-air drying easily causes rice kernel fissuring and browning, and has low energy utilization efficiency. Existing infrared drying mostly uses high-temperature radiation sources of 400–800 °C, which suffer from problems such as short irradiation time, high instantaneous intensity, and open-flame risks. To address these pain points, the team carried out joint research on graphene far-infrared grain drying technology and equipment. The peak wavelength of graphene far-infrared radiation is about 9.4 μm, which highly overlaps with the absorption bands of moisture, proteins, and carbohydrates in grains, allowing penetration into the grain for simultaneous internal and external heating, with no combustion emissions and no open-flame risk. The team developed a graphene low-temperature far-infrared irradiation panel and multi-channel irradiation heating and ventilation dehumidification modules. Using "Nanjing 46" rice as the test object, single-factor experiments and response surface optimization were conducted. The optimal drying conditions were determined as an infrared radiation temperature of 51.01 °C, an air velocity of 377.69 m³/h, and a grain flow rate of 8 kg/min. The drying kinetics were best fitted by the Midilli model, with an effective moisture diffusion coefficient of 8.79–29.97×10⁻¹⁰ m²/s and a drying activation energy of 36.41 kJ/mol. When the radiation source temperature increased from 35 °C to 60 °C, the drying time shortened from 460 min to 180 min, and the thermal efficiency increased from 49.28% to 73.47%. A 5H-10 graphene far-infrared grain dryer was developed, with a batch processing capacity of 10–12 tons. In rice tests, the drying rate was 1.3%/h; in wheat tests, the drying rate was 1.4%/h, the moisture-removal energy consumption was 3193 kJ/kg, and the increase in broken kernel rate was only 0.3%, with comprehensive performance superior to national and industry standards. This technology achieves open-flame-free, low-energy, and high-quality drying, and is of great significance for safeguarding national food security.
