COMPARISON OF DRYING KINETICS OF SPENT GRAIN DRIED ON INERT MATERIAL OF DIFFERENT HEAT CAPACITY M. Zielinska a,b S. Cenkowski b a Department of Agro-Food Process Engineering, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland b Department of Biosystems Engineering, University of Manitoba, Winnipeg, Canada Project financially supported by Polish Ministry of High School Education through the program “Supporting International Mobility of Researchers” and The Natural Sciences and Engineering Research Council of Canada (NSERC)

PLAN Overview Objective Material Experimental set up Methodology Experimental results

OVERVIEW Ethanol production Distiller’s spent grain Superheated steam drying Fluidized bed of inert particles Mathematical modeling of SS drying

OBJECTIVE To determine the effect of different heat capacity of inert particle on the drying characteristics of slurry fraction of grain stillage at a selected range of SS temperatures and velocities

MATERIAL Whole stillage (Mohawk Canada Limited, Husky Oil Limited, Minnedosa, MB) Slurry fraction of grain stillage (wheat distiller’s spent grain, wet distillers’ grains, DSG) The initial moisture content of DSG fraction was 75.2 ± 0.6 % w.b. Fig.1. The wheat whole stillage and slurry fraction of grain stillage

INERT MATERIAL Solid sphere Hollow sphere Size of a teflon spheres: 50.8 mm in diameter Mass of a solid sphere: g Mass of ahollow sphere: 69.2 g Fig. 2. Three dimensional view of the hollow teflon sphere Thickness of the layer of a hollow sphere: 3.5 mm

SAMPLE PREPARATION (1) (2)(3) (4) (5) The mass of wet DSG used for one experiment 22.0 ± 0.1 g equivalent to a 3 mm layer Fig. 3. The sample preparation for multilayer drying experiments using single inert element

OPERATING PARAMETERS The steam temperature : 110, 130, 160°C Pressure: under or near atmospheric pressure (the max. chamber pressure was 1 kPa above atmospheric pressure) The velocity of steam : 0.5, 0.7, 1 m/s

SUPERHEATED STEAM PROCESSING SYSTEM Fig. 4. Schematic diagram of the superheated steam processing system Drying chamber Water tank Superheater Steam generator Condensation unit Steam conveying pipes and valves Data aquisition and control system

MASS MEASUREMENTS Fig.5. The superheated steam drying chamber Drying chamber (outside) Mass balance Fan Drying chamber (inside)

TEMPERATURE MEASUREMENT

FLOW MEASUREMENT

PRESSURE MEASUREMENT

EXPERIMENTAL RESULTS Fig. 6. Typical changes in moisture content and material temperature during DSG drying on solid sphere in SS Steam temperature 160  C velocity 1 m/s) (1) (2) (3) (4)

EXPERIMENTAL RESULTS Fig. 4. Changes in DSG moisture during drying on hollow and solid sphere Steam temperature 110, 130, 160  C velocity 1 m/s Solid sphere Hollow sphere

EXPERIMENTAL RESULTS Fig. 5. The enlarged initial stage of processing DSG in SS Hollow sphere Solid sphere Steam temperature 110, 130, 160  C velocity 1 m/s 3.38 kg/kg 3.12 kg/kg 3.54 kg/kg 3.81 kg/kg

EXPERIMENTAL RESULTS Fig. 6. Moisture changes in DSG layer dried on hollow teflon sphere Steam temperature 160  C velocity 0.5, 0.7, 1 m/s

EXPERIMENTAL RESULTS Fig. 7. A typical material temperature characteristics of DSG dried on hollow and solid inert material in SS Steam temperature 160  C velocity of 1 m/s

EXPERIMENTAL RESULTS Fig. 8. A typical material temperature characteristics of DSG dried on solid inert material in SS Steam temperature 110, 130, 160  C velocity 1 m/s

EXPERIMENTAL RESULTS Fig. 9. A typical material temperature characteristics of DSG dried on solid inert material in SS Steam temperature 160  C velocity 0.5, 0.7, 1 m/s

CONCLUSIONS The constant rate drying period and the falling drying rate period were noticeable for the SS drying of the DSG layer on single inert material Drying on a solid sphere caused the initial moisture content of the sample to increase to the values 10% higher in comparison to the moisture gain on the DSG surface dried on a hollow sphere The increase in SS temperature from 110 to 160  C caused the initial moisture gain to decrease by 15% The increase in SS velocity from 0.5 to 1.0 m/s caused the initial moisture gain to decrease by 10-15%

The warm-up period of the DSG was influenced by the different heat capacity of inert material Drying of the DSG on a hollow sphere in comparison to the drying on a solid sphere cut the entire drying time even by 30% The increase in steam velocity from 0.5 m/s to 1.0 m/s resulted in shortening the entire drying time by almost 40%. The material dried on the solid teflon sphere showed a substantial delay on the temperature rate increases in the 2 nd rate period in comparison with drying on the hollow sphere.