Radiant Heating and Tempering Treatmentsfor Improving Rate of Moisture Removalduring Drying of Shelled Corn

Radiant heating holds great potential to improve the drying rate of freshly-harvested, high moisture content (MC) grain. The effectiveness of the process when combined with tempering steps for drying corn has not been elucidated. This study evaluated the effects of various process parameters during radiant heating and tempering treatment of corn to determine the percentage point of moisture removed and relative energy requirements. Freshly-harvested corn at initial moisture contents (IMCs) of 20%, 24% and 28% wet basis (w.b.) were used in the study. The corn was heated using an IR energy source equipped with catalytic IR emitters to surface temperatures of 50°C, 70°C, and 90°C. The IR treatments were performed with the corn kernels at product-to-emitter-gap (PEG) sizes of 110, 240, and 430 mm which corresponded to measured IR intensities of 10.84, 2.83 and 2.15 kW m-2. Following the IR treatments, the samples were tempered for 2, 4, and 6 hours at 50°C, 70°C, and 90°C. The study evaluated the implications of one- and two-pass IR heating and tempering treatments. The rate of corn kernel surface temperature rise depended on the PEG size and IMC. The longest duration corresponded to the largest PEG (430 mm) size and IMC (28%), and vice versa. At a PEG size of 430 mm, IR heating durations of 110, 122, and 140 s were required to raise the surface temperature of the corn kernels at IMCs of 20%, 24%, and 28% (w.b.) and ambient conditions (26°C) to 90°C, respectively. IR heating of corn at IMC range of 20% to 28% and at PEG size of 430 mm to surface temperatures ranging from 50°C to 90°C resulted in 0.9 to 3.2 and 1.5 to 5.2 percentage point reduction in MC, for one- and two-pass treatments, respectively. The longer the tempering duration the more moisture was removed from the corn kernels. One-pass IR heating of corn kernel at IMC of 28% and PEG size of 430 mm to surface temperature of 90°C, and tempering at 50°C, 70°C, and 90°C for 6 h, resulted in 4.2, 4.7 and 5.2 percentage points and 7.2, 8.7, and 8.6 percentage points of moisture removed for one- and two-pass treatments, respectively. The significant and rapid moisture removals by the IR and tempering treatments provide for justification to optimize and scale-up the practices for corn drying.