Industrial-scale contact-type far-infrared grain drying: Drying rate, energy performance, and quality evaluation

: This study investigates the drying performance of a self-developed industrial-scale contact-type far-infrared (C-FIR) grain circulation dryer for paddy rice. The system integrates four graphene heating modules and four convection dehumidification modules in a vertically alternating arrangement, enabling continuous grain circulation and efficient moisture removal. Heat is transferred to the grain through two mechanisms: contact conduction contributes 58.31% of the total heat input, while far-infrared radiation accounts for 41.69%. Drying experiments were conducted using an initial batch of 10 t of freshly harvested paddy rice, with a graphene plate surface temperature of 75 °C and an airflow rate of 5046 m 3 ·h -1 . The drying kinetics, energy performance, and final grain quality were systematically evaluated. The overall drying rate reached 2.18 × 10 -4 kg·kg -1 ·min -1 . The specific total energy consumption was 3.92 MJ·kg -1 , and the overall thermal efficiency was 64.5%. The final maximum moisture difference was 0.69% (wet basis), and the crack ratio increase was only 2.8%, indicating excellent drying uniformity and minimal kernel damage. Compared with conventional hot-air drying, the C-FIR system eliminates the need for preheating large air volumes, thereby substantially reducing energy waste. These findings demonstrate that the industrial-scale C-FIR dryer offers superior energy efficiency and satisfactory grain quality, providing a promising and sustainable alternative for modern grain processing.