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)

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

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)

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 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.