Thermophysical properties of laboratory-prepared corn/wheat dried distillers grains and dried distillers solubles dehydrated with superheated steam and hot air

ABSTRACT

The objective of this study was to dry–wet distillers grains and centrifuged solubles and to examine the effect of two different drying media, superheated steam and hot air, at different drying temperatures (110, 130, and 160°C), moisture contents (5–30% wb), and percentages of solubles’ presence (0 or 100%) on some thermophysical properties of laboratory-prepared corn/wheat dried distillers co-products, including geometric mean diameter (d_g), particle density (ρ_p), bulk density (ρ_b), bulk porosity (ϵ_b), specific heat (C), effective thermal diffusivity (α_eff), and bulk thermal conductivity (λ_b). The values of d_g of corn/wheat dried distillers co-products ranged from 0.358 ± 0.001 to 0.449 ± 0.001 mm. Experimental values of ρ_p, ρ_b, and ϵ_b varied from 1171 ± 6 to 1269 ± 3 kg m⁻³, from 359 ± 7 to 605 ± 5 kg m⁻³, and from 0.54 ± 0.01 to 0.71 ± 0.01 kg m⁻³, respectively. The values of α_eff were between 0.58 × 10⁻⁷ and 0.93 × 10⁻⁷ m² s⁻¹. The calculated values of C ranged from 1887 ± 11 to 2599 ± 19 J kg⁻¹ K⁻¹, and the values of λ_b of corn/wheat dried distillers co-products ranged from 0.06 ± 0.01 to 0.09 ± 0.01 W m⁻¹ K⁻¹. Multiple linear regression prediction models were developed to predict the changes in d_g, ρ_p, ρ_b, ϵ_b, C, α_eff, and λ_b of laboratory-prepared corn/wheat dried distillers co-products with different operational factors.

KEYWORDS:

• Corn/wheat dried distillers co-products
• hot air drying
• physical properties
• superheated steam drying
• thermal properties

Acknowledgments

The author would like to thank Stefan Cenkowski from the Department of Biosystems Engineering, University of Manitoba for making his laboratory available for the needs of the project; Kelsey Hargreaves from the University of Manitoba for her technical support; and the local distillery (Mohawk Canada Limited, Minnedosa, MB, Canada) for donating stillage.