Enhancing rotary dryer efficiency: Adjusting blower speed for optimal temperature stability in coffee bean drying

Abstract

This study evaluates the quality of coffee beans dried using a rotary dryer with Fuzzy Logic Control (FLC) for temperature with airspeed regulation. Laboratory tests assessed gravimetric water content, acidity levels, and antioxidant content to determine the effects of drying parameters. The FLC system effectively stabilized the drying temperature at a setpoint of 60 °C, with errors below 0.17 % under and 2 % above the setpoint. This precise control enhanced drying efficiency while maintaining the quality standards of coffee beans, achieving a moisture content below 12.5 % (SNI 01–2907–2008). Results showed that coffee beans dried at 270 min (1 kg mass) achieved a water content of 11.28 %, while 330 min (2 kg mass) reduced the water content to 9.92 %. For 450 min (3 kg mass), the water content stabilized at 10.92 %. Acidity and antioxidant levels remained optimal across all tests. This study demonstrates the effectiveness of fuzzy logic-based rotary dryers for efficient and high-quality coffee bean processing, regardless of drying mass.

Key Methodology:

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  Developed a fuzzy logic control system for real-time blower speed to regulated temperature adjustments.
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  Stabilized hot air distribution to reduce temperature deviations and relative humidity.
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  Conducted gravimetric, acidity, and antioxidant analyses on coffee beans with varying drying times and masses.