Control Strategies for Low Temperature In-bin Drying of Barley for Feed and Malt

Abstract

A computer simulation model, which was adequately verified by comparing measured and predicted data in drying wet barley in a thin-layer batch dryer, was used to investigate low-temperature in-bin drying of barley grain for feed and malt under typical weather conditions in the Canadian prairies in North America. Drying systems with and without supplementary heat were simulated for air flow rates of 1 to 2 m3 min-1 t-1, initial grain moisture contents of 16 to 25% and harvests in August, September and October. The optimum control strategies were obtained within set bounds of drying time. grain deterioration by mould growth and storage time for viability to fall to 99%.A control strategy for drying by continuous ventilation without supplementary heat can he used to dry feed and malt barley within 30 d if the initial grain moisture content is less than 19% in August and 16% in September. Drying under other initial moisture contents and time of harvest requires supplementary heat to complete drying within 30 or 15 d. High or moderate drying air temperatures above ambient and in excess of about 30 to 40°C can significantly reduce viability and other desirable malting qualities. For such conditions, cooling the grain after drying to about 15°C with cool ambient air can greatly increase the storage life of the grain. However, it is safe to dry barley for malt in deep beds or bins for long-term storage artificially provided the drying air temperature does not exceed 25°C at relative humidities below ambient and the initial grain moisture content is not more than 22%.The drying systems with supplementary heat, by maintaining the inlet air temperature at 30 to 40°C, resulted in reduced drying time and least drying costs for feed barley, while the control strategies by increasing the ambient temperature by 5 to 10°C, or maintaining the inlet air temperature below 25°C, were the best for drying barley for malt.