Superheated Steam Drying of Distillers' Spent Grains on a Single Inert Particle

Abstract

The article presents the results of drying a distillers’ spent grain fraction (DSG) of a stillage in superheated steam (SS). The study aimed at determination of the effect of SS parameters on drying kinetics of DSG deposited as a pasty layer on the 50-mm solid Teflon sphere. Drying was conducted at approximately 2 to 4 kPa above the atmospheric pressure, with steam temperature ranging from 110 to 160°C and steam velocity of 1 m/s. Samples were dried with SS at different processing times ranging from 60 to 360 min, depending on the SS temperature. During the initial warmup period of SS processing, the pasty DSG gained moisture due to steam condensation on its surface, which further evaporated at constant material temperature (apparent constant rate period). That period ended as soon as the condensate evaporated and temperature of the product passed the saturation point of steam. Only the falling drying rate period was observed. The drying rates increased from 0.02 to 0.83 L/min with the increase in steam temperature from 110 to 160°C, respectively. The effective diffusivity of moisture in DSG increased with the increase in steam temperature according to the Arrhenius-type relationship. The values of the effective diffusivity ranged between 3.24 × 10⁻¹⁰ and 2.48 × 10⁻⁹ m²/s, with the activation energy of 53.74 kJ/mol.

Keywords:

• Distillers' spent grain
• Drying
• Single inert particle
• Stillage
• Superheated steam

ACKNOWLEDGMENT

The study was financially supported by the Polish Ministry of Science and Higher Education through the program entitled “Supporting International Mobility of Researchers” and by the Natural Sciences and Engineering Research Council of Canada.