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COMPARISON OF DRYING KINETICS OF SPENT GRAIN DRIED ON INERT MATERIAL
OF DIFFERENT HEAT CAPACITY
M. Zielinska a,b S. Cenkowski b
aDepartment 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)
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
MATERIALWhole 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 MATERIALSolid sphereHollow sphere
Size of a teflon spheres: 50.8 mm in diameter
Mass of a solid sphere: 149.2 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 gequivalent to a 3 mm layer
Fig. 3. The sample preparation for multilayer drying experiments using single inert element
OPERATING PARAMETERSThe 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 tankSuperheater
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)
EXPERIMENTAL RESULTS
Fig. 6. Typical changes in moisture content and material temperature during DSG drying on solid sphere in SS
Steam temperature 160C 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, 160C 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, 160C velocity 1 m/s
3.38 kg/kg
3.12 kg/kg3.54 kg/kg
3.81 kg/kg
EXPERIMENTAL RESULTS
Fig. 6. Moisture changes in DSG layer dried on hollow teflon sphere
Steam temperature 160C 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 160C 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, 160C velocity 1 m/s
EXPERIMENTAL RESULTS
Fig. 9. A typical material temperature characteristics of DSG dried on solid inert material in SS
Steam temperature 160C velocity 0.5, 0.7, 1 m/s
CONCLUSIONSThe 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 160C 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%
CONCLUSIONS
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 2nd rate period in comparison with drying on the hollow sphere.