On-farm cross-flow dryer. Cross-flow drying. Goal. The glass transition (Tg) line. Tempering

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1 ay 23, 17 On-farm cross-flow dryer Undried rice (inlet) Effect of material state gradients on head rice yield reduction during cross-flow drying Drying column angeeta ukhopadhyay and Terry J. iebenmorgen 24 th Industry Alliance eeting 17 ay 23, 17 Fan Burner ross-flow drying ymmetry line Goal Improve the rice drying process = drying + tempering illing yield Dryer performance Energy-use efficiency Dryer throughput Tempering The glass transition (Tg) line ommercial drying processes comprise multiple passes, with periods of tempering between passes 9 Rubbery region Low viscosity, modulus of elasticity, and density; holding the rice in a bin Allows intra-kernel moisture and material state gradients to subside Temperature, 3 1 High diffusivity, specific heat, specific volume, and thermal volumetric expansion coefficient Glassy region High viscosity, modulus of elasticity, and density; Low diffusivity, specific heat, specific volume, and thermal volumetric expansion coefficient (T g = X ; R 2 =.81) oisture content, % w.b. 1

2 ay 23, 17 Tg hypothesis Temperature ( ) Fissure formation during drying Initial state (uniform T and ) Thin-layer drying vs. deep-bed drying Temperature ( ) Fissure formation during tempering 9 (a) 3 (b) (a) Tempering temperature > Tg 1 (b) Tempering temperature < Tg Objectives 1. Quantify the effects of drying and tempering treatments on moisture contents (s) and HRY reductions (HRYRs) as a function of location within the drying column 2. tudy the effects of intra-kernel material state gradients on HRYRs within the drying column From dryer to laboratory set-up ymmetry line 12.7 cm B1 Fiberglass baskets Air-duct Heated air 38 cm B7 B5 B3 B2 B1 onditioned-air inlet Acrylic glass cylinder Rough rice T/RH sensor/logger Gasket Wooden box T/RH sensor/logger led-environment chamber Experimental design (full factorial) FATOR ultivar Roy J (16.3% initial ) Tg = 46 Airflow rate (.56 (m 3 /s)/m 2 ) Drying duration ( min) 1. Drying air conditions i. To maintain kernels in the glassy state: /32% RH ii. To induce different extents of intra-kernel material state gradients: /18% RH, /12% RH, /8% RH 2. Tempering approaches REPONE 1. T/RH of the drying air 2. of rice after min of drying 3. RY and HRY 2

3 ay 23, 17 s after min of drying Initial = 16.3% Drying air conditions Bulk column (%, wb) ᵒ/26% RH 14.3 ᵒ/17% RH ᵒ/13% RH ᵒ/9% RH 11.5 ross-flow dryer ymmetry line /26% RH /17% RH 1 Basket 1 is next to the HAP Tempering approaches illing analyses i. TA1 - Bulk column; not tempered ii. TA2 - Bulk column; tempered Duplicate, 1-g samples Dehulled in laboratory huller, milled to.4% surface lipid content Data presented as RY and HRY Dehuller Laboratory mill Grading machine Rough rice was conditioned to 12% using air at 26 /56% RH Five, 1-g samples were milled and the yields averaged Bulk-column milling yields Tempering approaches illed rice yield (%) Tempered Not tempered iii. TA2 Individual baskets; not tempered iv. TA4 Individual baskets; tempered /26% RH /17% RH Drying air condition /26% RH /17% RH Drying air condition 3

4 ay 23, 17 HRYs within the column Tempered Not tempered HRY reduction in light of the Tg line /26% RH /17% RH /26% RH Basket 1 is next to the HAP B1 B1 Relevant considerations Relevant considerations 1. Bulk vs. individual-kernel s Individual-kernel s Individual-kernel behavior Relevant considerations HRY reduction in light of Tg line Tempered 2. The Tg line T g = X (R 2 =.81) /26% RH 4

5 ay 23, 17 /26% RH /17% RH Extent of intra-kernel material state gradients Equilibrium ummary and conclusions Final s 1. Increased with distance from HAP; large variations in within the column 2. Decreased with increasing severity of drying air condition illing yield 1. RY decreased only at the most severe drying air condition; RY was not affected by whether or not the rice was tempered after drying 2. HRYs Kernel in glassy state Negligible HRYR regardless if samples were tempered after drying or not Thank you Kernel with material state gradients Negligible HRYR if samples were tempered at an elevated temperature after drying 5