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DESIGN or A PILOT-SCALE CONCURRENT
FLOW GRAIN DRYER

Thesis for the Degree of M. S.

MICHIGAN STATE UNIVERSITY

DENNIS PETER KUNE ’
1977

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ABSTRACT

DESIGN OF A PILOT-SCALE CONCURRENT
FLOW GRAIN DRYER

BY

Dennis Peter Kline

A continuous flow pilot-scale grain dryer with
concurrent drying and counter-flow cooling was designed,
constructed and tested. The dryer constitutes an evolu-
tion of previously designed models. Mechanical air locks
and spreading devices have been eliminated. A positive
grain metering mechanism has been installed to obtain con-
sistent grain throughput rates.

The main body of the thesis details the construc-
tion and operation of the pilot-scale dryer used. Corn
was used to test the dryer initially. After modification

of the dryer, soybeans were dried.

Approved EW/ jflgé /éd/M2

Major Professor

I
Approved B. «M

Department Chairman

[6267

 

DESIGN OF A PILOTHSCALE CONCURRENT

FLOW GRAIN DRYER

BY

Dennis Peter Kline

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Agricultural Engineering

1977

g‘i .. _

ACKNOWLEDGMENTS

It has been the author's privilege to work under
the guidance of Dr. Fred W. Bakker-Arkema, whose friend-
ship and advice are appreciated.

I would like to thank Dr. Lynn S. Robertson and
Lloyd E. Lerew for serving on my guidance committee and
for the knowledge I gained from them while completing my
program.

I would also like to thank the Andersons of
Maumee Ohio for their financial support during the pro-
gram.

I offer my gratitude to my parents, Mr. and Mrs.
George D. Kline, for the help they provided in the prepa-
ration of the final copy of the thesis and for the moral
support they offered to me throughout the program.

The pilot-scaled dryer was designed, constructed,
and tested jointly with my good friend, Stephen J. Kalchik.
I would especially like to thank Stephen and my many
friends at Michigan State University for their help and

encouragement while completing my program.

ii

TABLE OF CONTENTS

LIST OF TABLES . . . . . . . . . . .
LIST OF FIGURES . . . . . . . . . .
LIST OF SYMBOLS . . . . . . . . . .

LIST OF TERMS . . . . . . . . . . .

INTRODUCTION . . . . . . . . . . .

Background on Concurrent Flow Dryers .

Background on Concurrent Flow Laboratory

Dryers O O O O O O O O O 0
Objectives . . . . . . . . . .

DESCRIPTION CONSTRUCTION AND TESTING OF DRYING
APPARATUS O O O O O O O O O O C C

Concurrent Section . . . . . .
Grain Level Maintenance and Air Lock
Components . . . . . . . . .

Counter-Flow Section . . . . . .
Instrumentation . . . . . . . .
Operation . . . . . . . . .

Testing of Dryer Using Corn . . . .

SUMMARY . . . . . . . . . . . . .
CONCLUSIONS . . . . . . . . . . . .
SUGGESTIONS FOR FUTURE STUDY . . . . . .
APPENDIX . . . . . . . . . . . .
REFERENCES . . . . . . . . . . . .

iii

Page

iv

vi

vii

12
17
20
20
27
31
36
41
43
51
52
53
55

134

LIST OF TABLES

Table Page
1. Summary of Monitoring Equipment . . . . 38
2. Data Collected During the First Corn

Drying Test . . . . . . . . . . . 48
3. Heat Balance Calculations . . . . . . 49
4. Mass Balance Calculations . . . . . . 50

iv

Figure
1. Theoretical Concurrent Air and Grain
Temperatures . . . . . . .
2. Theoretical Crossflow Air and Grain
Temperatures . . . . . . .
3. Oholm Grain Dryer . . . . . .
4. M and W Perfect Kern'l Grain Dryer
5. Mfihlbauer Grain Dryer . . . .
6. Anderson Spreaderless Design . .
7. Anderson Pendulum Spreading Device
8. Westelaken Floor . . . . . .
9. Westelaken Three Stage Dryer . .
10. Westelaken Three Stage Dryer with Heating
Air Recirculators . . . . . .
11. Pilot-Scale Dryer Before Modifications
12. Revolving Spreading Device . . .
13. Modified Spreaderless Design . .
14. Overall View of Pilot-Scale Concurrent
Flow Grain Dryer . . . . . .
15. Exposed View of Concurrent Section
16. Exposed View of Grain Level Maintenance
and Airlock Components . . . .
17. Exposed View of Counter-Flow Section
18. Instrumentation Diagram . . . .

LIST OF FIGURES

Page

10
11
13

13
15
18
18

21
23

28
34
39

LI ST OF SYMBOLS

Absolute humidity, lb. water/lb dry air
(kg water/kg dry air).

Moisture content, % dry basis.

Moisture content, inlet, % dry basis.
Moisture content, outlet, % dry basis.
Rate of wet air movement, cfm/min (m3/min).
Rate of dry movement, cfm/min (m3/min).

Specific heat of air, .24 BTU/lb air/°F

(10004 J/kg air/°C).

Temperature °F (°C).

vi

Air Lock

Concurrent Flow

Concurrent Section

Cooling Air

Cooling Zone

Counter-current Flow

Counter-flow Section

Cross Flow

Heating Air

Heating Zone

Product

LIST OF TERMS

A device which inhibits air passage
while allowing for grain movement.

Condition which exists when grain
and air move in the same direction.

That portion of the dryer which
includes the heating section, tem-
pering section, and related compo-
nents so as to allow for concurrent
flow of product and air.

Ambient air which is forced through
the cooling section.

That portion of the counter-flow
section in which the cooling air
and product have flow velocities in
opposite directions.

Condition which exists when grain
and air move in opposite directions.

That portions of the dryer which
includes the cooling section and
related components to allow for
counter-flow of air and product.

Condition which exists when grain
and air flow in perpendicular
directions.

Air that has passed through the
burner and which is forced through
the heating section

That portion of the concurrent
section in which the heating air
and product have flow velocities
in the same directions.

The biological material being arti-
ficially dryed.

vii

Spreading Device

Tampering Zone

A device which mechanically intro-
duces a layer of wet grain on top
of the heating section.

That portion of the concurrent sec-
tion in which heated grain travels
in an environment free of air
movement allowing the grain to
temper.

viii

INTRODUCTION

The first section of this study involves the
design, construction, and testing of a pilot-scale dryer
using corn as the product. The pilot-scale dryer uses
the principle of concurrent heating and counter-flow
cooling.

The maximum product temperature is lower than the
maximum heating air temperature (see Fig. 1). In a cross-
flow grain dryer, the temperature of the product will
approach or equal the maximum value of the heating air

(see Fig. 2). Corn was used as the testing medium.

Background on Concurrent Flow Dryers

A concurrent flow grain dryer, patented in the
United States by a Swedish inventor (Oholm, 1955), fea-
tures a method of transferring energy to the grain in the
upper drying bed without increasing the absolute humidity
of the heating air (see Fig. 3). Hot liquid can be cir-
culated through pipes to transfer heat to the grain. The
concept could prove practical if direct fired burners
could not be supplied with the relatively clean burning
fuels now available.

A portable concurrent flow grain dryer is produced

by the M andW Gear Company (see Fig. 4). The M and W

1

Temp.

450

20

180‘“

160-

140“

 

120

°F

  

Heating air temperature

Product temperature

Temp.

  
    

 

2

 

Figure l.--Theoretical Concurrent Air and Grain

30 60 90 120 cm
I 1 l I

l l l I

1 2 3 4 ft

Temperatures.

°C

230

90
80
70
60

SO

 

 

 

  

Temp. °F Temp. °C
200 n . 90
Heating Air Temperature
180 - #— I. 80
160‘ .. 70
140 Product Temperature ”’60

 

 
 

 

60 90 120 cm

I I 1 l

I I I l

1 2 3 4 ft
Depth

Figure 2.--Theoretical Crossflow Air and Grain
Temperature

 

 

 

 

 

 

 

 

 

FIGURE 3.--Oholm Grain Dryer.
Legend: 1. Heating element

2. Grain inlet

3. Heating pipes

4. Heating air exhausts

1 Grain velocity

0 Hot air velocity

 

 

 

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FIGURE 4.--M and W Perfect Kern'l Grain Dryer

Legend: 1. Grain inlet auger
2. Hot air inlet
. Hot air and cooling air exhaust
Cooling air inlet
. Grain metering mechanism
Grain outlet auger
Grain velocity
Hot air velocity
Cooling air velocity

”(zemmnw

Perfect Kern'l grain dryer is similar in design and prin-
ciple to a drying apparatus patented by Graham (1967a).
The dryer is similar in design to the first concurrent
flow dryer constructed by Anderson (1972). The heated air
temperature is limited to 300°F (149°C) with a grain
throughput rate of approximately 2.5 bushels of corn per
hour per square foot (.85 m3/m2) (Graham 1967).

Mfihlbauer et al., (1971) constructed a concurrent
flow dryer in which the heating air escapes upward through
the grain placed on top of the dryer (see Fig. 5). No
detrimental effect on grain quality or dryer efficiency
was observed.

One of the first commercial continuous flow grain
dryers using a concurrent heating section and a counter-
flow cooling section is described by Anderson (1972). The
dryer has no spreading device (see Fig. 6) and is reported
to cause excessive grain damage as a result of overdrying
the grain. Bees wings collected in the valleys and was
believed to have been responsible for many fires. The
grain flow rate was reported to be approximately five
bushels per hour per square foot (.18 m3/m2). The temr
perature of the heating air was limited to 350°F (177°C)
in order to reduce the fire hazard and preserve grain
quality. Another problem encountered was that of unequal

heating air temperature distribution across the top of

 

 

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AA
AA

 

 

 

 

AA
AA

 

 

Figure 5.--Muhlbauer Grain Dryer.

. Grain inlet

Heating air inlet
Heating section
Heating air exhaust
Cooling air exhaust
Cooling section
Cooling air inlet

Legend:

1
2
3
4
5
6
7

the heating bed due to heat losses through the long air
ducts.

A second prototype was constructed by Anderson
(1972) with a spreader built on top of the heating sec-
tion. The spreading device (see Fig. 7) eliminated many
of the problems encountered with the first prototype. A
point of interest is that the suggested safe Operating
temperature is 525°F (274°C) for corn, and is limited by
the ignition point of bees wings which was experimentally
found to be between 550 and 575°F (287 and 302°C).

Spreaderless, continuous flow concurrent drying
and counter-flow cooling grain dryers are being con-
structed for commercial grain operations by Westelaken
(1975). The dryers use a "grid" type floor with insulated
round steel tubes located above the heating bed to intro-
duce the heating air to the product (see Fig. 8). The
steel "grid" floor combined with high air and product flow
rates is used to prevent the problems of other spreader-
less designs while eliminating the need for the extra
moving parts found in spreader-type dryers. Many of these
dryers are multi-stage designs (see Fig. 9). Two or more
concurrent heating stages are installed. Grain is
allowed to temper between the heating stages. Improved
grain quality and greater overall drying efficiency as a
result of the extra heating and tempering sections are

two benefits of using multi-stage dryers.

 

 

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Figure 7.--Anderson Pendulum Spreading Device.

1. Pivot point for pendulum spreading device
2. Inlet grain hopper

3. Pendulum spreading device

0 Hot air velocity

v Grain velocity

000 .Hot air and grain boundary

11

 

 

 

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01 0 I 0 0

 

 

'0 0’. g
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Legend: 1.
2.
V
v

000

0..

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Figure 8.--Westelaken Floor.

Top view of Westelaken floor

Side View of Westelaken floor

Hot air velocity

Grain velocity

Boundary between hot air and grain

11

 

 

 

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Figure 8.--Weste1aken Floor.

Legend: 1. Top view of Westelaken floor
2. Side view of Westelaken floor
V Hot air velocity
V Grain velocity
ooo Boundary between hot air and grain

12

A modification of the multi-stage concurrent flow
dryer (see Fig. 10) is the addition of heating air exhaust
recirculators (Bakker—Arkema, 1977). Exhaust air from the
first drying zone is heated and circulated through the
second heating zone. The exhaust air from the second
heating section is circulated through the third heating
stage. This modification will reduce the amount of energy
which must be used to heat the incoming air for the second
and third drying zones.

Background on Concurrent Flow
Laboratory Dryers

Carrano (1970) designed, constructed, and tested
the first Michigan State University prototype of the con-
current flow laboratory dryer. The dryer was made of
square steel sections bolted together and insulated. Corn
was the product dried. Spreader and Spreaderless versions
of the dryer were tested. An air lock was used to prevent
the downward flow of air in the counter-flow cooling sec-
tion. No means of replenishing the wet grain supply was
provided. Testing was limited by the amount of grain
which could be loaded into a sealed holding hOpper on top
of the dryer. A 47% reduction in germination was reported
for grain dried at 450°F (232°C) at a flow rate of approxi—
mately 3.2 bushels per square foot per hour (.13 m3/m2/hr).

The Carrano square sectioned dryer was replaced

by a round sectioned dryer (see Fig. 11) by Gygax (1972).

13

Figure 9.--Westelaken Three Stage Dryer.

Figure 10.--Westelaken Three Stage Dryer with Heating
Air Recirculators

Legend:

LOG)\lO\U'IubWNl-'
O

1.:
O

11.
12.

13.
14.
15.
16.
17.

18.
19.

20.

Grain bin

First hot air inlet

First drying zone

First hot air exhaust

First tempering zone

Second hot air inlet

Second drying zone

Second hot air exhaust
Second tempering zone

Third hot air inlet

Third drying zone

Third hot air exhaust and
cooling exhaust

Cooling zone

Cooling air inlet

Metering rolls

Dry grain discharge

First stage heating air exhaust
recirculator

Second stage heating air fan
Second stage heating air exhaust
recirculator

Third stage heating air fan

14

 

 

 

 

 

 

 

 

 

 

 

 

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18

 

 

 

 

 

 

 

 

19

20

 

 

 

 

 

10

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________14________

 

 

Fig. 9 Fig. 10

15

Figure 11.--Pilot-Scale Dryer Before Modifications.

Legend:

1.
2.
3.
4.
5.
6.
7

8.

9.
10.
11.
12.
l3.

14.

15.
16.

ago

Bucket elevator

Mechanical air lock

Grain storage hopper

Mechanical grain spreading device
Heat air enters here

Concurrent drying section
Perforated circular drying section
metering and unloading mechanism
Screen funnel-heated air exists
here

Mechanical air lock

Cooling fan

Cooling air exits here
Counter-current cooling section
Perforated circular cooling sec-
tion unloading mechanism
Discharge auger

Heated air fan

Burner

Grain velocity

Heating airflow velocity

Cooling airflow velocity

17

A spreading device (see Fig. 12) was constructed and put
on top of the heating bed. Heavy motors and gear boxes
powered the rotating spreader and rotary air lock. The
dryer had many air leaks and an unreliable grain through-
put metering mechanism.

The dryer used in this study had no speader or
rotary air locks and had fewer moving parts. The pilot-
scale dryer has a high degree of reliability when com-
pared to previous laboratory dryers. The rotary air lock
used in the Gygax dryer was eliminated in the pilot-scale
dryer used in this study by an air restriction tube (see
Fig. 13). The circular feed mechanism was replaced by a

grain collection cone and metering auger.

Objectives

 

'1. To modify and test a concurrent flow labora-
tory grain dryer.

2. To conduct drying tests with corn and soy-
beans.

3. To gain experience and knowledge in the
field of continuous flow concurrent drying

of grain.

18

Figure 12. Revolving Spreading Device.

Legend:

0 QQWNH

Rotary air :5“

Rotary spreader

Hot air inlet

Hot air velocity

Grain velocity

Boundary between hot air and
grain

Figure 13.--Modified Spreaderless Design.

Legend:

0

l
2
3
V

W
o

0

Air flow restriction tube
Grain distribution tube

Hot air inlet

Hot air velocity

Grain velocity

Boundary between hot air and
grain

 

 

 

 

 

 

 

 

oooooo

 

 

 

 

 

 

DESCRIPTION CONSTRUCTION AND TESTING

OF DRYING APPARATUS

The pilot-scale laboratory dryer is an evolution-
ary machine. Many of the parts on the dryer to be
described have been used on previous prototypes. Since
the laboratory dryer is small when compared to larger
commercially available dryers, care must be taken not to
assume that problems common to each can be solved for both
by using similar solutions. Airflow and heating air
temperature distributions may not be a problem in a small
laboratory dryer and may be a relevant problem in a larger
scale machine.

The grain and airflow paths through the present
machine are illustrated in Figure 14. The Figure illus-

trates components to be discussed.

Concurrent Section

 

The concurrent section is that part of the dryer
in which the heating air is introduced and forced through
the moving grain bed. The concurrent section of the dryer
also includes the grain flow metering mechanism. Fig—'

ure 15 illustrates the components of the concurrent sec-

tion.

20

21

Figure 14.--Overall View of Pilot-Scale Concurrent Flow

Grain Dryer.

Legend:

1.
2.
3
4

\OCDQONU'I
O

10.
11.
12.
13.
14.
15.
16.
17.

Bucket elevator

Grain storage hopper

Natural grain airlock

Heating air and grain boundary
area

Concurrent drying section
Heating air exit

Tempering section

Grain flow rate metering auger
D. C. shunt wound variable
speed motor

Cooling air exit

Cooling section

Cooling air entrance

Cooling section air lock
Cooling section discharge auger
Cooling air fan

Heated air fan

Burner

Grain flow

Hot air flow

Cooling air flow

22

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 15.

23

Exposed View of Concurrent Section.

Legend:

\OGJQONUWQWNH

20.
21.
22.

23.
24.

Heated air introduction chamber
Asbestos gasket

Asbestos gasket

Heated air elbow

Asbestos gasket

Burner

Gasket

Transition piece

Burner ignition and safety
controls

Asbestos gasket

Concurrent heating section

Air shroud with exit

Air shroud

Heated air exit

Tempering zone

Grain collection cone

Grain collection cone supporting
Grain collection hopper shield
Grain collection hopper
Concurrent section base support
frame

Concurrent grain metering
discharge auger

Variable speed D.C. shunt wound
electric motor and Speed reduction
Grain spout

Inlet fan and motor assembly

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

15

 

 

 

 

24

 

 

 

 

 

 

 

 

 

 

25

The tee section (1) is from a previous design of
the dryer. Heating air is directed to the heating section
from the burner via the tee section and elbow (4) which
connects to the burner (6) and burner safety controls (9).

The burner and burner safety controls are from a
previous dryer. A liquid petroleum tank (located outside
of the building) provides the fuel for the burner. Safety
devices include an automatic shut-off valve to guard
against burner malfunction. A transition piece (8) was
constructed of galvanized sheet metal to connect the
burner to an inlet air supply hose. All air hoses used
on the dryer are four inches (10.16 cm) in diameter and
are made of wire-reinforced vinyl. Inlet air is supplied
by a 22 inch (56 cm) diameter forward inclined fan powered
by a five horsepower motor (24).

Asbestos gaskets (10, 2, 3, 5, and 7) are used to
prevent air leakage; 3/8 inch (9.5 in m) bolts of various
lengths are used throughout the construction of the dryer.

The heating section (11) is three feet (91.44 cm)
long with a one square foot (930 cm2) cross-sectional
area. The wet product and heating air meet and flow
through this section in the same direction.

After the heated air travels the full length of
the heating section, the air is exhausted through the

heated air exhaust (l4). Perforated sheet metal was

v‘
.

 

26

welded to the inside of this structural piece. Shrouds
(12 and 13) are placed over this section to provide a
means of monitoring exhaust air properties.

After the heating air is exhausted, the grain
continues to move downward. The tempering zone (15) is
provided as a means of allowing the grain to remain warm
and to allow for moisture redistribution within the indi-
vidual product particles. Better product quality and
greater overall dryer efficiency are reported by Foster
(1964) as a result of tempering.

Grain exist and metering mechanisms (16-23) are
located below the tempering zone. Grain is funneled into
a metering auger (21) and hopper (19) by a cone made of
galvanized sheet metal (16). The grain collection cone
(16) is held into place by a ring with tabs welded to the
side of the ring (17). The ring bolts on to the base (20)
and prevents the long column of grain from forcing the
cone downward. The grain collection hopper (19) was
formed using galvanized sheet metal. The design allows
for easy removal and replacement of the metering auger
(21-23). Hoper side extentions were later added to pre-
vent spilling upon filling the dryer initially. The con-
current section support frame (20) prevents the round
portion and heated air assemblies from falling over. Sty-

rofoam panels (not shown) were added to prevent an

27

excessive heat loss through the bottom of the concurrent
section.

The 4 inch (10.16 cm) in diameter metering auger
(21-23) is placed with the inlet portion in the grain
collection hopper (19). The auger sets at a 60 degree
angle to the floor. A grain shield (23) was constructed
and fitted to the auger to prevent grain spilling from
the auger discharge to the inlet of the counter-flow
section of the dryer. The auger is covered with fiber-
glass insulation to prevent heat loss from the product.

A variable speed D.C. shunt wound electric motor
(22) and control are used to power the metering auger. A
gear reduction shaft and extra pulleys are used to arrive
at a proper range of discharge rates of the product being
dried. The variable speed motor allows for infinite dis-
charge auger speeds and constitutes an easy method for
change of the grain throughput rate.

Grain Level Maintenance and
Air Lock Components

The purpose of the grain level maintenance and
air lock components is to maintain a supply of wet grain
above the heating section of the dryer. A natural air
lock is formed which prevents the upward escape of heat-

ing air. Figure 16 illustrates an exposed view of this

section of the dryer.

28

Figure l6.--Exposed View of Grain Level Maintenance
and Airlock Components.

Legend:

1.

N

mmnw
O o o o

\Dmd
o I.

10.
11.
12.

Bucket elevator

1/3 horsepower capacitor-start
electric motor

Spout and deflector plate
HOpper shield

Microswitch section

Lower hopper section

Grain distribution tube
Airflow restriction tube
Asbestos gasket

Asbestos gasket

Heated air introduction chamber
Inlet grain temperature thermo-
coupe support

29

 

 

 

 

 

 

 

 

 

10

11

 

 

 

 

30

A bucket elevator (l) is used to transport the
product from the floor to the wet grain holding hopper
(4-6). Micro switches (5) are positioned to assure that
the wet grain holding hopper would have an adequate amount
of grain during the tests. The micro switches engage a
relay (not shown) which in turn power a 1/3 horsepower E
capacitor-start motor (2).

The grain distribution tube (7) spreads grain

over the heating bed and is the means by which the heat- r

 

ing air is introduced to the wet product above the drying
zone (see Fig. 13). The grain distribution tube (7) is
nine inches (23.9 cm) in diameter and four feet (12 cm)
long. Two feet (60.5 cm) extend into the tee section (11)
of the concurrent section. A donut shaped flange is.
welded to the middle of the grain distribution tube to
support the tube above the drying bed. Heated air cir-
culates around the two foot (60.5 cm) length of the grain
distribution tube which fits inside of the tee section to
prevent grain damage. An asbestos gasket is bolted
between the tee section (1) and the grain distribution
tube. The lower hopper assembly is bolted to a base
welded onto the top of the grain distribution tube. A
gasket is installed between the lower hopper assembly
and the grain distribution tube.

The air restriction tube (8) is bolted to the

lower grain hopper (6). This component is a 4 inch

31

(10.16 cm) diameter insulated aluminum tube 54 inches
(1.37 m) in length. Wet product fills the tube when the
dryer is in operation and prevents any significant leak-
age of heating air. The discharge end of the air restric-
tion tube empties wet grain into the grain distribution
tube (7).

Inlet grain temperature thermocouples allow deter- I

mination of the inlet grain temperature, thereby indicat-

 

ing if there is any significant air leakage. The support
is constructed of a steel rod to allow placement of the
thermocouples at 12 inches (30.5 cm) and 36 inches (91.5

cm) below the hopper section.

Counter-Flow Section

The product leaves the metering auger of the con-
current section (see Fig. 17). The purpose of the counter-
flow section is to cool the grain thoroughly in a counter-
flow fashion. The driest and coolest grain is exposed to
the coolest air, thereby minimizing quality deteriation.
The cooling section of the dryer is constructed of round
sections one square foot (929 cm2) in area bolted together.

The product level is maintained by two micro
switches (3A) located in the upper region of the cooler
(3). The microswitches are similar in design and Opera-
tion to the micro switches installed in the grain level

maintenance portion of the concurrent section. Two

32

shields (l and 2) are constructed of tin and provide
access to the micro switches. The micro switches engage
and disengage the discharge auger (13). The auger does
not Operate continuously: therefore, the counter-flow
section of the dryer is in reality not a continuous flow
mechanism. I
Exhaust air is collected and exited through a 7

four inch (10.16 cm) diameter pipe (3b) so that the dry

 

bulb and wet bulb temperatures can be measured. r

The cooling air exhaust and counter-flow product
level maintenance chamber (3) is constructed of 20 gauge
sheet metal. This section supports the metering auger
and is bolted to the middle counter-flow section via a
gasket (4).

The cooling of the grain takes place in the middle
counter-flow section (5). This two foot (60.96 cm) long
section of the dryer was used on previous dryers and
needed no modifications for use on this model. Room tem-
perature cooling air is introduced to the product in the
lower counter-flow section (7) through a perforated wedge
(7a) formed of perforated sheet metal. The wedge is
bolted to the inside of the round section. A square hole
exists in the side of the round section to allow cooling
air to travel upward through the cooling bed. A transi-
tion (7b) allows a four inch (10.16 cm) diameter hose to

be installed between the cooling bed and cooling fan (16).

33

The bottom of the counter-flow section is made air-
tight by a tin plate (1) and a gasket (10) bolted to the
bottom between the base (12) and lower counter-flow sec-
tion (7). The base (12) is constructed of one inch (2.54
cm) welded square tubing.

Cooling air is provided by a 15 inch (38.1 cm) '
centrifugal fan (16) that is powered by a two horsepower
three phase motor. A laminar flow element (not shown) is

placed between the fan and transition. Two pieces of hose hi

 

connect the three components. Cooling airflow may be
changed by adding shutters or changing fan and motor
pulley sizes.

The product discharge mechanism is very similar in
action to the unloading mechanism found in the concurrent
section. A grain collection funnel (18) is held in place
by sheet metal screws. The product is funneled into a
collection basin (9) where the discharge auger's (13)
inlet is placed. The auger is placed inside of the lower
counter-flow section (7) near the bottom and sealed in
place to prevent air leakage. A stand (not shown) is
provided to support the discharge end of the auger.

A temporary spout and flow diverter (not shown)
were added near the inlet of the counter-flow section so
that the counter-flow section of the dryer could be by-

passed.

34

Figure 17.--Exposed View of Counter-Flow Section.

Legend:

LONE-4

3a.
3b.
4.
5.
6.
7.
7a.
7b.

8.

9.
10.
11.
12.
13.
14.

Micro switch inspection plate
Microswitch inspection plate
Cooling air exhaust and counter-
flow product level maintenance
Micro switches

Exhaust air exit

Gasket

Middle counter-flow section
Gasket

Lower counter—flow section
Perforated air introduction wedge
Fan to counter-flow section air
transition

Product collecting funnel
Product collection basis

Gasket

Counter-flow section end plate
Counter-flow section base frame
Discharge auger

Cooling fan

36

Instrumentation

 

The instrumentation of a pilot-scale laboratory
dryer distinguishes a pilot-scale dryer from larger
dryers. A description of the instrumentation is summar-
ized in Table l.

The accurate measurement of product moisture con-
tent is of primary importance to those dealing with bio-
logical products. Efficiency of the pilot scale dryer is
calculated using the change in grain moisture content and
amount of energy used to change the moisture content. A
Steinlite moisture meter measures dielectric properties
of the product being tested to indirectly determine
moisture content.

An oven dry method (Brooker et al., 1974) was
used to directly measure the moisture content of both
corn and soybeans. Results are compared to those obtained
using the Steinlite. The results indicated that the
Steinlite was accurate when compared to the oven dry
method.

Air flow of heating and cooling air is accom-
plished by the use of a laminar flow element and a cali-
brated manometer installed in the heating bed at 6, 12,
and 24 inches (15.24, 30.48, and 60.97 cm):m3that pressure
drop across the drying bed could be measured. The same

plastic hoses that connect the laminar flow element to

 

 

37

the manometer were used to correct the pressure taps to
the manometer.

Humidity determination is accomplished by two
methods. Relative humidity of ambient room air is
determined using the Bendix Aviation psychometer (see
Table 1). Wet bulb thermocouples are installed at the
air outlet of the heating air fan (8 and 9) air outlet of
the concurrent section (10 and 11) and air outlet of the
counter-flow section (12 and 13). The wicks are changed
and inspected before each run.

Air and grain temperatures are closely monitored.
Heated air temperatures are measured separately by a two
channel Texas Instrument recorder and asbestos-insulated
iron-constantan thermocouple wires (6 and 7). A 24
channel Texas Instrument recorder is used to monitor the
copper-constantan thermocouples.

The inlet grain temperature is measured by insert-
ing a mercury in glass thermometer in the inlet grain
before being loaded into the dryer. A second method
involves installing thermocouples (l and 2) in the air
restriction tube as described in the section titled,
Grain Level Maintenance and Air Lock Components.

Air leakage should cause the bottom thermocouple
to record a significantly higher temperature than the top
thermocouple. Heating air‘was not lost through the open

top of the dryer as the thermocouples in the air

38

TABLE l.--Summary of Monitoring Equipment.

 

Instruments Description--Accuracy

 

l. Manometer Meriam Model 40GD10WM-6.
Accuracy : 0.02 inch water

2. Laminar Flow Elements Meriam Model 50 MC2-4p.
Accuracy : 0.05% of calibra-
tion curve

3. Recorder Texas Instruments twenty-four
Channel Model EMWT6B
Accuracy : 0.75°F, linearity
: 0.3°F.

4. Recorder Texas Instruments two channel
Model P 502 W6A
Accuracy : 2°F, linearity
i 0.3°F

5. Moisture Tester Steinlite Model 400 G,
Accuracy + 0.5% moisture con-

tent weE basis

6. Drying Oven Blue M. Electric Company
Model OVSlO, Mercury in
steel thermometer used,

Accuracy : 2.5°F.

7. Room Air Psychmeter Bendix Aviation Corporation
Model 573,
Accuracy : 5% relative
humidity.

 

39

Figure 18.--Instrumentation Diagram.

Legend:

Thermocouple Location

1.

N
o

mmbw
I O O

8.
9.
10.
ll.
12.
13.

Air
14.
15.

16.
17.

18.

Inlet grain (12") (30.48 cm)
above concurrent section

Inlet grain (36") (91.44 cm)
above concurrent section

6" (15.24 cm) concurrent section
12" (30.48 cm) concurrent section
24" (60.96 cm) concurrent section
Heated air immediately before
introduction to concurrent
section

Heated air immediately before
introduction to concurrent
section

Wet bulb inlet air

Dry bulb inlet air

Wet bulb concurrent exhaust air
Dry bulb concurrent exhaust air
Wet bulb counter—flow exhaust air
Dry bulb counter-flow exhaust air

Pressure Measurement Locations

6" (15.24 cm) concurrent section
12" (30.48 cm) concurrent section
24" (60.96 cm) concurrent section
Concurrent inlet air laminer

flow element

Counterflow inlet air laminer
flow element

£11wa

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

40

 

 

 

 

 

 

 

 

 

 

 

 

 

41

restriction tube recorded nearly identical temperature
measurements throughout the tests.

Grain bed air and grain temperatures are measured
by copper-constantan thermocouples at the same locations
as the static pressure taps. The thermocouples are placed
inside hollow steel rods about 1.5 inches (3.81 cm) from
the wall of the dryer.

The outlet grain temperature is measured using a

mercury in glass thermometer at the discharge collection
container of the counter-flow section.
The throughput rate of the product is determined

using a Toledo platform scale and watch.

Operation

 

Operation of the dryer consisted of three steps:
(1) pre-equilibrium procedures; (2) testing after reaching
equilibrium and, (3) post run operations. The first step
was that of filling the concurrent flow section with pre-
viously dried products. Product to be dried was added
after the concurrent section was filled. The metering
auger was engaged and set to the desired discharge rate.
The heating air fan, burner, and burner safety controls
were adjusted to maintain the desired heating air tempera-
ture. Iron-constantan thermocouples and a recorder were
used to determine the air temperature of the heating air.

The cooling fan was engaged as soon as the first product

42

was discharged out of the counter-flow section. A 24
channel recorder was used to determine if equilibrium
had been reached. Ambient air conditions and inlet grain
temperatures were recorded at this time.

Wet product had to be added throughout the test
at regular intervals in order to keep heating air from
escaping through the natural air lock. Inlet heating air
temperatures were monitored and adjusted if needed
throughout the drying run.

After reaching equilibrium, the throughput rate
of product was determined with the platform scale and a
watch. Outlet and inlet grain samples were collected for
further analysis. Drying bed, inlet air, outlet air,
wetbulb and inlet grain temperatures were noted.

After all the wet product has been fed through
the dryer, the testing stopped and post run operations
were begun. Previously dried product was placed on top
of the wet product in the drying section to preserve the
natural air lock. After all the wet product has been
dried, the gas fired burner and controls were turned off.
The heating fan continued to run until the heating zone
of the dryer had cooled. The cooling fan was allowed to

run until all the product was out of the counter-flow

section.

43

Testing of Dryer Using Corn

Corn was used for initial testing of the dryer
for two main reasons. More readily available information
can be obtained about drying corn than soybeans or any
other cereal grain. Standardized tests can be run on
corn samples obtained from a drying run and compared to
previous work. The tests include germination and Stein
breakage tests (Anderson 1972).

The second reason for selecting corn as the best
test medium is purely economical. The price of soybeans
at the time of initial dryer testing was approximately
three times the price of corn. Corn can also be rewetted
and re-dried many times (Carrano 1970).

The first corn test will be described as it was
the only experiment in which germination and Stein break-
age tests were conducted. Later tests used rewetted corn
from the first corn test.

Corn purchased for the test was ear corn and
required shelling before being dried in the dryer. The
steps followed in the operation of the dryer are described
in the previous section (2.5). Three inlet corn samples
were collected during the run. Inlet moisture content
was measured before conducting the test using the Stein-
lite moisture meter to determine the approximate feed rate
of the metering auger for obtaining a moisture content

level of between 13 and 20 percent moisture content dry

 

44

basis. Five outlet grain samples were collected during
the test after the dryer had reached equilibrium. Data
gathered during the test is found in Table 2.

Moisture content was checked on the three inlet
grain samples and the five outlet samples the day after
the test was conducted. The moisture content gradient
within the dried kernals will be less the day after the
testing than immediately after the run is completed.

Germination is a measure of the amount of damage
done to a product during the drying process. Germination
is a strict test of quality. A process which reduces the
viability of the seed may or may not alter the usefulness
of the product for its intended purpose.

One hundred sound kernals from each sample are
placed inside special germination papers and soaked with
water. After a week, the papers are unwrapped and the
number of normally germinating kernals are counted as the
percent germination.

A standardized breakage test was performed on the
eight samples. The samples were conditioned before the
breakage tests were conducted. The amount of breakage is
influenced by the moisture content of the grain. The
samples were placed in screen trays insidea conditioning
box. The conditioning box contains a circulation fan
and pans of saturated sodium chloride salt solution in

order to maintain a constant relative humidity of

 

 

45

approximately 75%. The temperature of the conditioning
box was approximately 80°F (26°C). The purpose of the

conditioning box is to allow the samples to arrive at a
uniform moisture content level of approximately 14% MC

dry basis (Brooker 1974).

After a week, the samples were removed from the
conditioning box. One hundred grams of grain which had
been cleaned over a 3/16 inch mesh screen were used for
the breakage tests. \

The Stein breakage tester contains an inpeller
which revolves on the inside of a container loaded with
the 100 gram sample for a timed period of two minutes.
After the sample is treated in the breakage tester, the
sample is screened over a 12/64 inch round sieve. The
sample is again weighed. The difference between the
initial grain sample weight and the sample weight after
the treatment is the percent breakage.

Heat balance calculations (see Table 3) determine
the efficiency of.the pilot-scale grain dryer with regard
to energy consumed per unit weight of water removed. The
air flow was obtained by the use of a laminar flow ele-
ment and a manometer. Thermocouples at the heating air
inlet and outlet were used to obtain the air temperatures
used in the heat balance evaluations. The grain through-
put rate was obtained by using a Toledo platform scale

and a watch. Density of the air was determined from a

 

 

46

psychrometric chart after the room air temperature and
relative humidity were measured. The amount of water that
was removed from the grain was measured one day after the
testing was completed by using a Steinlite moisture meter.

The mass balance calculations (see Table 4) of the
first corn run had to be calculated after the heat balance
calculations were completed. The wet bulb thermocouple
located in the heating air exhaust port produced erroneous
temperature readings. Normally, heat and mass calcula-
tions are done independently to serve as a check for an
error in the calculations or in gathering the data.

The mass of the water removed by the cooler was
calculated. The wet and dry bulb thermocouples measured
constant temperatures throughout the first corn test.

The cooling air flow rate was determined by using a lami-
nar flow element and a manometer. Ambient room air was
used for cooling the grain through the counter-flow sec-
tion.

The mass of water removed by the heating air was
not measured due to the faulty thermocouple. The mass of
_water removed from the grain in the dryer was calculated
by subtracting the water removed from the grain by cooling
air from the total amount of water removed from the grain.

The heating value of the fuel, the amount of
energy required to warm the heating air, and the combus-

tion constant of the fuel are values which are used to

,:_EW

fir

 

47

obtain the mass of water added to the heating air due to
combustion of the fuel in the direct fired burner. The

heating air mass includes the water gained by combustion
of the fuel and the mass of water removed from the grain.

The water mass of the ambient air is added to the
heating air mass and constitutes the total water mass of
the heating air. The total water mass of the heating air
is divided by the dry airflow rate to determine the abso-
lute humidity of the exhaust heating air.

The throughput rate of the dryer for the first
test was 7.4 bushels per hour (.25 cubic meter per hour).
The temperature of the heating air was 360°F (182°C) at
an airflow rate of 128 CFM (3.62 m3/min). The grain was
dried from 29.5% to 22.5% moisture content dry basis. The
germination and Stein breakage test show very little dam-
age was done to the corn. Higher air temperatures and
slower grain throughput rates were used in later tests.

I After the first run was completed, modifications
to the pilot-scale dryer were made. A grain shield at
the tOp of the wet grain holding hopper (Fig. 16) and a
shield for the grain collection hopper (Fig. 16) were
installed. The train of the product metering auger (see
Fig. 17) was redesigned to provide for a lower throughput
rate of the dryer. After further testing, two copper-
constantan thermocouples were installed on the inside of

the air restriction tube to determine heating air loss

and the inlet grain temperature.

 

48

TABLE 2.--Data Collected During the First Corn Drying Test.

 

 

Parameters Measurements
l. Inlet Grain MC, dry basis 29.5%
2. Outlet Grain MC, dry basis 22.5%
3. Heating Air Temperature 360°F (182°C)

4. Inlet Temperature of Grain 39°F (2.9°C)
5. Outlet Temperature of Grain 80°F (27°C)
*6. Test Weight of Inlet Grain 52 lb/bu (660 kg/m3)
7. Test Weight of Outlet Grain 52 lb/bu (669 kg/m3)
8

. Grain Throughput Rate 412 lb/hr (184 kg/hr)
7.4 bu/hr (.25 m /hr
9.2 ft/hr (2.8 m/hr)

 

9. Ambient Air Relative

Humidity 39%
10. Ambient Air Temperature 68°F (20°C)
11. Heating Air Exhaust

Temperature 137°F (58°C)
12. Cooling Air Exhaust

Temperature 83°F (28°C)
13. Cooling Air Wet Bulb

Temperature 81°F (26°C)

14. Drying Bed Temperatures

A. 6 inch (15.2 cm) depth 182°F (83°C)
B. 12 inch (30.4 cm) depth 176°F (80°C)
C. 18 inch (15.6 cm) depth 173°F (78°C)

15- Density of Air

0.074 lb/ft3 (1.2 kg/m3)

16. Air flow rate of heating 128 CFM (3.62 m3/min)
air measured at ambient 53 CFM/bu (51m3/ton)
air conditions

17. Air flow rate of cooling 20 CFM (.6 m3/min)
air measured at ambient 8 CFM/bu (7.7 m3/ton)

air conditions
18. Germination Tests

A. Inlet Grain 39.3%
B. Dryed Grain 31.2%
C. % Decrease in Germination 21.6%

19. Breakage Tests

A. Inlet Grain 8%
B. Dryed Grain 12%
C. Percent increase 50%

 

49

TABLE 3.--Heat Balance Calculations.

 

Conditions

Results

 

1.

Rwa for heating air:

Airflow rate X 60 X air
density

Heat needed to warm heat-
ing air:

T X Rwa X Sha
MC Change:
MC. - MC

in out

Dry matter throughput
rate:

Grain throughput rate X
(l - MC change)

Water removed from grain:

Dry matter rate X
MC change

Energy requirement for
water removed:

Energy required/amount
of water removed

568.0 1b/hr (257.3 kg/hr)

41,464 BTU/hr (4.3714107 J)

7%

385.4 1b/hr (174.6 kg/hr)

29.091 1b/hr (13.18 kg/hr)

1650 BTU/lb water removed

(3.842 X 106 J/g water

removed)

 

 

50

TABLE 4.-—Mass Balance Calculations.

 

Conditions

Results

 

l. Rwa for cooling air:

Air flow rate 60 air
density

2. Increase in absolute
humidity of cooling air:

Ah cooling exhausair-Ah
ambient air

3. Mass of water removed by
cooler:

Rwa X Increase in
absolute humidity

4. Mass of Water Removed by
Heating air:

Water removed from grain-
water removed by cooler

5. Mass of Fuel burned:

Heat needed to warm

heating air/heating

value* (19,444 BTU/1b)
6. Mass of water added to

heating air due to com-
bustion of fuel:

Mass of fuel burned X
combustion constant**

7. Total mass of water added
to heating air:

Mass of water added to
heating air due to com-
bustion + mass of water
removed by heating air
from grain

8. Rda of heating air:
Rda/l + Hh
9. Ah of heating air exhaust:

(Rwa - Rda X total mass of
water)/Rda

88.2 lbs air/hr (39.9 kg
air/hr)

0.024 lb water/lb dry air
(0.24 kg water water/kg
dry air)

2.12 lb water/hr
(0.96 kg water/hr)

26.97 lb water/hr
(12:22 kg water/hr)

2.13 lb fuel/hr (0.97 lb
fuel/hr)

3.49 lb water/hr
(1.58 kg water/hr)
1.63 lb water/lb of fuel

30.46 lb/hr (13.461 kg/hr)

564.6 1b/hr (255.5 kg/hr)

0.06 lb water/lb dry air
(0.06 kg water/kg dry air)

 

*Hall (1957).

**Chilton and Perry (1973).

 

SUMMARY

Pilot scale continues flow grain dryers can be
used to predict the performance of a larger machine for
a given set of conditions. Modifications can be made on

pilot scale dryers easier and with less expense incurred ,

 

than if the same modifications are made on larger dryers.
Corn and soybeans were dried in the tests. Other prod-
ucts, e.g., rice, should be dried in a pilot scale dryer
before attempts are made to dry the products in a larger
machine.

Germination and breakage tests were conducted on
samples taken during the first corn run with a 4%
increase in the amount of breakage and an 8.1% decrease
in germination caused by drying the corn in the pilot

scale dryer at 360°F (182°C).

51

CONCLUS IONS

1. By using the pilot—scale concurrent flow
dryer, performance of large scale concurrent flow dryers
can be predicted.

2. Grain throughput rates are as important as
heated air temperatures and flow rates in determining
whether spreader devices are needed to preserve grain
quality.

3. Proper instrumentation is necessary to the
successful operation of a pilot-scale dryer.

4. A pilot-scale dryer should be designed to

permit modifications with relative ease.

52

SUGGESTIONS FOR FUTURE STUDY

Humidity determination was a problem using wet
bulb thermocouples during the tests.

A gas flow meter should be installed on the liquid
petroleum feed line to the burner. The use of this meter 4
would provide a check when heat and mass balances are cal-
culated.

Air flow measurement is an important aspect of
grain dryer testing. The laminar flow elements should be
recalibrated or other air flow measurement methods
installed to insure that airflow is accurately measured.

The conversion of the laboratory dryer to a multi-
stage heating section dryer should be investigated as a
method to increase the amount of water removed for a given
amount of energy consumed without a reduction of grain
quality.

The counter-flow section of the dryer is separated
from the concurrent section of the dryer. The operation
of the dryer could be simplified further if the counter-
flow section were fitted directly beneath the concurrent
section. Lack of ceiling clearance necessitated the

separation of the concurrent and counter-flow sections.

53

:mfij‘.

54

More information needs to be gathered about the
tempering section of the dryer to determine the optimum
length for different initial product conditions with
regard to quality retention and or gains in drying effi-
ciency.

A heat exchanger was installed on the dryer dur-
ing some of the corn runs (Sokhansanj 1977). The results
were encouraging. Further work should be done in the

area of heat exchangers and exhaust air recirculation.

 

APPENDIX

DRYING OF SOYBEANS IN A PILOT-SCALE

CONCURRENT FLOW DRYER

55

TABLE OF CONTENTS

Page

LIST OF TABLES . . . . . . . . . . . .. 57
LIST OF FIGURES . . . . . . . . . . . 58
LIST OF ABBREVIATIONS AND COMPUTER VARIABLE
NAMES . . . . . . . . . . . . . . . 559
INTRODUCTION . . . . . . . . . . . . 62
BACKGROUND INFORMATION . . . . . . . . . 64
OBJECTIVES . . . . . . . . . . . . . 70
REVIEW OF SELECTED PREVIOUS CONCURRENT DRYER
WORK . . . . . . . . . . . . . . . 71
QUALITY TESTS USED ON THE SOYBEANS . . . . . 73
TEST PROCEDURE . . . . . . . . . . . . 78
RESULTS AND DISCUSSION . . . . . . . . . 83

Calculation Procedure . . . . . . . 83

Soybean Test Data . . . . . . . . . 91

Quality Analysis Results . . . . . . 108
CONCLUSIONS . . . . . . . . . . . . . 113
SUGGESTIONS FOR FURTHER STUDY . . . . . . . 114
APPENDICES

A. Concurrent Dryer Analysis Program . . 115

B. Chemical Oil Analysis Procedures . . 120

C. Computer Simulations . . . . . . 125
REFERENCES . . . . . . . . . . . . . 132

56

(i

LIST OF TABLES

Table Page

1. Humidity Corrections Calculation Example . 96

2. Calculated and Measured Exhaust Wet Bulb
Temperatures . . . . . . . . . . 102

3. Concurrent Exhaust Relative Humidity
Predicted V. Calculated Values . . . . 109

4. Germination and Stress Cracks of the Soy-
bean Samples . . . . . . . . . . 111

5. Results of Chemical Oil Analysis . . . . 112

57

 

LIST OF FIGURES

Figure Page
1. Grain Flow Calibration Chart . . . . . 80

2. Predicted v. Actual Bed Temperatures for
the First Run First Pass . . . . . . 100

3. Predicted v. Actual Bed Temperatures for —
the First Run Second Pass . . . . . . 104

 

4. Predicted v. Actual Bed Temperatures for
the Second Run . . . . . . . . . . 106

58

LIST OF ABBREVIATIONS AND COMPUTER VARIABLE NAMES

MC Moisture content

TDB Dry bulb temperature

WGT Weight

CFM Cubic feet per minute

BTU British thermal unit

wb Wet basis (moisture content)

The following appear in the concurrent dryer analysis

program:
AHI Abolute humidity of air into dryer
after heating
AHIC Absolute humidity into counterflow
AHIO Absolute humidity into concurrent section
IAHO Abolute humidity of concurrent exhaust
AHOC Absolute humidity of counterflow exhaust
AHR Total pounds of water removed by air in
both sections per hour (lb/hr)
AHRA Pounds of water removed per hour by
air in concurrent section (lb/hr)
AIRC Countercurrent airflow (CFM)
AIRH Concurrent airflow (CFM)
BDO Test weight of dryer output (lb/bu)

59

BTU

BTUPP

CAP

CFP

DM

GBTU

PH

PHC

PM

PRO

TDBI

TH

TGE

TO

TI

TOT

WBU

WCI

WCO

Net energy into system (BTU/hr)

Energy consumed per pound of water removed
(BTU/lb)

Grain flow rate out (bu/hr)

Ambient air density (CUBIC FEET/pound)
Dry matter (lb)

Gross energy into system (BTU/hr)
Pounds of dry air per hour through
concurrent section (lb/hr)

Airflow in cooler (lb/hr)

Grain flow rate out (lb/min)

Propane burned (lb/hr)

Ambient dry bulb temperature (°F)
Heated air temperature (°F)

Change in energy of grain due to changes
in temperature and moisture content

in and out

Grain temperature out (°F)

Grain temperature in (°F)

Grain flow rate out (lb/hr)

Water removed from grain (lb/bu)

Wet basis moisture content of grain in
(decimal)

Wet basis moisture content of grain out

(decimal)

60

WI

WO

Pounds of water in grain in per hour (lb/hr)
Pounds of water in grain out per hour
(lb/hr)

Pounds of water removed from grain (lb/hr)

61

INTRODUCTION

A wide variety of farm crops has been artificially
dried in the past with satisfactory results for certain
uses of those crops. Corn in particular has been artifi-
cially dried because of high initial moisture content. A -
great percentage of the corn (greater than 80%) is used
for animal feeds where the nutritional characteristics
remain acceptable even though some indices of quality,
especially germination, may be quite low as a result of
drying. This thesis is concerned with soybeans and the
quality retained through artificial drying with a concur-
rent flow dryer. The soybeans are not intended for use
as seed but germination is used as a quality indicator
because of its extreme sensitivity. The primary purpose
of the drying process is to prepare the soybeans for an
oil extraction plant. The high temperatures could have a
detrimental effect on the quality of oil extracted from
the soybeans. The literature available tended to indicate
that about 175° F (79 C) is the upper temperature limit
for retaining the oil quality within an acceptable range
(Bunn, 1970). Nowhere, was the duration of time and tem-
perature during the drying process linked to quality of

the oil.

62

63

Soybeans may be stored safely for several months
at a moisture content of 13% wb..(Wolf.muiCowan, 1971).
Prior to processing for oil, however, the moisture content
must be reduced to 9% wb.* The first processing step
removes the hulls (since they contain no oil) and the
second step forms the soybeans into flakes to hasten the
solvent extraction rate. This research is concerned with
quality changes as the result of drying soybeans between
13 and 9% wb.

The remainder of the soybeans after extraction may
be used for soybean meal, soy flours, concentrates, or
isolates. These products are used directly as feed (soy-
bean meal), processed further for use as additives to
such foods as baked goods for the control of fat absorb-
tion and emulsification properties, or to produce tex-
tured vegetable proteins (Alden, 1975).

The oil quality is the most difficult to retain
so it is the quality and retention of the oil quality that

is studied in this thesis.

 

*Interview with C. M. Westlaken, Westlake Agri-
cultural Engineering, St. Mary's, Ontario, 1977.

BACKGROUND INFORMAT ION

Crop dryers used for drying seeds, either grains,
such as corn, wheat, and oats, or legumes such as soy-
beans may be of either batch or continuous-flow design.
Grains and legumes are two different products but in this
thesis for the purposes of description of dryers the term
"grains" will include both groups unless specifically
indicated otherwise.

Batch drying systems may involve either in-bin
arrangements or columns of grain through which air of
below 70% relative humidity is forced. Relative humidity
of the air is critical because differences in vapor pres-
sure of the water in the air and the water in the kernel
determine whether or not drying occurs. This principle
holds for all dryers. Equilibrium moisture content is
the moisture content of a grain at a specified air rela-
tive humidity and temperature. When drying air has a
lower relative humidity than that required for the desired
final moisture content it is possible that part of the
grain bed may be overdried if exposed to that air for a
long period of time. Such is the case with many batch
systems. Briefly, in a drying bed, a front passes through

in the direction of airflow with relatively dry grain

64

65

as the drying air enters the bed and wet grain beyond.
It is possible under conditions where the grain initially
is quite cool to have condensation of water on the wet
grain side of the front as it passes through the bin.

The in-bin arrangements may use either a full bin,
a single layer of a few feet, or several layers added
daily on top of each other. Close management is required
with each to be sure that the wet grain, not yet reached
by the drying front does not remain in the bin long
enough for mold to grow. As the depth of grain in the
bed increases to a full bin it becomes increasingly
important that the equilibrium moisture content of the
grain at the drying air conditions is not below the maxi-
mum desired final moisture content. Frequently with full
bin systems, the grain is stored in the same bin. There-
fore the drying front must be forced completely through
the bed to prevent mold at the drying front and in the wet
grain beyond. Using drying air with a low equilibrium
moisture content results in an entire bin of grain that
is too dry. This may result in a longer storage life but
also in loss of weight for which a premium is not often
paid at the market.

With in-bin systems using layers of only a few
feet the drying front may not be pushed completely through
the bed before drying is stopped. The grain at the air

entry point is overdried and the grain on top of the bin

66

remains at a high moisture content. Seldom can this grain
be stored safely in the drying bin. By experience the
operator can determine how far through the bed the drying
front must go so that when the grain is unloaded from the
bin and mixed, it will have an average moisture content
equal to the desired final moisture content. Several prob-
lems here include the breakage that occurs through hand-
ling of the overdried grain before mixing, stress cracks

in the overdried grain, and if mixing is incomplete the
mold that develops in wet pockets.

Uniform filling of the bin is critical to assure
an even bed depth and no concentrated areas of broken
kernels and foreign materials which may cause uneven air-
flows and therefore uneven movement of the drying front
through the bed. In an effort to reduce the moisture con-
tent gradient across the drying front, several manufac—
turers have developed grain circulation systems to stir
the bed continuously. The stirring mechanisms cause local
concentrations of foreign material which reduce the uni-
form flow of air. Such systems have problems with the
grain at the air inlet of the bed being subjected to over
drying and extended periods of heat. Less than uniform
airflows result in the drying front being completely
through certain areas of the bed while barely starting in
others. Ranges in moisture content result in some moldy

areas even though the average moisture content may have

67

been low enough for satisfactory storage. Batch in-bin
systems use bed depths of several feet (1 meter).
Batch drying systems using columns generally use
higher airflows than the in-bin systems and have verti-
cally oriented bed depths of 12 to 18 inches (30.5 to
45.7 cm) with air passing horizontally. Unfortunately
with this system considerable quality damage occurs 1
because of the rapid drying with air of a continuously "
low relative humidity. With this arrangement more uni- 1
form mixing occurs during unloading and this system is
easily adapted to automatic cycling so little time is
wasted between unloading of a dried batch and refilling
with wet grain. At this point also note that the periodic
cycling of these large quantities of grain with several
hours between cycles warrants extreme caution concerning
bystanders who may identify supply bins (garner bins) as
having stationary beds. This author feels the operator
should watch the operation closely enough to protect out-
siders from these less than obvious hazards.
The column type batch dryers are usually not as
energy efficient as the in-bin dryers especially where
deeper beds are used with the in-bin arrangements. With
deeper beds the air will absorb more moisture as it passes
through.
Continuous flow dryers are generally of crossflow

design. They differ from the batch dryers in that instead

68

of a stationary bed during drying process there is a
slowly moving bed of grain. The first most obvious dif-
ference is that a grain metering device is required so
that the grain flow rate can be regulated and controlled.
The grain flow rate is reasonably predictable and con-
stant at any given control setting (Hall, 1957).

Continuous flow crossflow dryers have similar I
quality problems to those of the batch crossflow design. ‘
Over drying on one side of the bed occurs but mixing on
release of the grain from the dryer eliminates wet pockets
in storage. Personal safety is not quite the problem with
continuous flow dryers because all of the grain is con-
tinuously moving at the same rate with no sudden changes.

Counterflow continuous-flow dryers are arranged
such that the drying air moves up through the bed while
the grain is continuously moving downward. The bed is
solid, not fluidized, but it is moving. The problem here
is that the hottest driest air is exposed to the warmest
driest grain. Counterflow dryers cause an extreme gra-
dient of moisture content within individual kernels.
Quality may be adversely affected. The kernels will be
over dried on the outside but quite wet in the middle.

The grain temperature may also approach the initial dry-
ing air temperature.

The concurrent continuous flow dryer is the type

of dryer studied for use in drying soybeans. Grain flow

69

and airflow both move downward. This creates a situation
where the hottest driest air hits the coolest wettest
grain. Temperature of the drying air decreases rapidly
because it is absorbing moisture from the cool wet grain.
The grain temperature also increases rapidly but it never
reaches the initial drying air temperature in this dryer.
The grain and air temperatures approach each other a few
centimeters into the bed and continually decrease from
that point. During this temperature decrease tempering
occurs where moisture from the center of the individual
kernels migrates to the outer kernel parts from where it
is slowly absorbed by the drying air. Since the drying
air becomes more saturated as the grain moves downward
and continues drying reduced stress within the kernels
exists than that found in either crossflow or counterflow
dryers because of the moisture content gradient. Because
of the lower stresses and the fact that none of the grain
is exposed to high temperatures for more than a few
minutes, significantly higher quality grain can be
obtained from this dryer than from crossflow, counterflow,
batch crossflow, or certain of the batch in-bin systems
while retaining the high capacities associated with con-

tinuous flow processes (Brooker et al., 1974).

OBJECTIVES

The objectives of the research reported in this

thesis are:

l.

2.

To mechanically test a pilot scale concur-
rent dryer.

To test soybeans in a pilot scale concur-
rent dryer.

To analyze quality changes of soybeans
dried in a concurrent dryer.

To compare results of corn dried in a con-
current flow dryer with those of soybeans.

70

J;

REVIEW OF SELECTED PREVIOUS CONCURRENT

DRYER WORK

Carrano (1970) dried corn with a concurrent flow
dryer using a bed depth of only 18 inches (46 cm) and
immediately cooled the grain with ambient air in counter-
current flow. Both Carrano (1970) and Anderson (1972) in
corn (with temperatures up to 550° F, 288 C) and soybeans
have maintained a spreading device was necessary to obtain
uniform treatment of the grain at the surface of the con-
current bed. The spreading device is a mechanical appa-
ratus that operates either by oscillating or rotary motion
to add another thin layer of wet grain about every 20
seconds to the top of the bed. The research reported in
this thesis indicated that a grain spreading device is not
essential to maintain quality if uniform flow of air and
grain is established within the dryer. This is simply a
flow design problem. No kernels were found with this
design to have been scorched.

Carrano (1970) reported no figure on how much
moisture was removed by the cooler but suspected it was
relatively low. It is nearly impossible to obtain accurate

moisture content readings on samples taken prior to

71

72

cooling due to handling problems with the warm grain and
the moisture content gradient within the kernels.

Exhaust air humidities are difficult to measure
as Carrano (1970) reported and it will be discussed in
detail later in this thesis. He also discusses the prob-
lem of rotary airlocks for moving the grain in and out of
the airflow. They may be a problem as experience on this
project has indicated. For that reason the rotary air- _
locks were eliminated in the final design of this project.

Gygax et a1. (1974) used higher air temperatures
(500° 53 260 C!) in a concurrent flow dryer and found a
"case hardening" effect that seemed to decrease rather
than increase test weight after drying. After re-wetting
corn and redrying it with the concurrent flow dryer, some
of the decrease may have resulted from the re-wetting.
The effects Gygax et a1. (1974) reported concerning the
Operator on counting of stress cracks in a sample is a
strong indication of the subjectivity of stress crack
analysis. However, this test should be considered with
soybeans because of its importance at the time of sale for

farmers. Little attention to this factor is generally

given for corn.

QUALITY TESTS USED ON THE SOYBEANS

The soybeans which were dried are intended for an
oil extraction plant and therefore oil quality is of
prime consideration here. Soybean oil is a compound pri-
marily composed of triglyceryl esters of oleic, linoleic,
and linolenic acids (Overhults et al., 1972). Fats are
generally considered as solidified compounds and oils as
liquids depending on the ambient temperature of the par-
ticular geographical location (Mehlenbacher, 1960). For
convenience the term oils will include both fats and oils.

As indicators of soybean oil quality, Overhults
et al. (1972) used free fatty acids, iodine number, per-
oxide number, and thiobarbituric acid value. Free fatty
acids occur as a result of hydrolysis of some of the tri-
glycerides (Mehlenbacher, 1960). Cracks in the soybeans
expose the oil to enzmes within the seed. Hydrolysis Of
the oils (by enzyme action) result in the formation of
free fatty acids. During one step of the oil refining
- process, alkali is added which combines with the free
fatty acids. The soap formed by the combination of alkali
and free fatty acids percipitates out but carries with
it some of the neutral oil. Free fatty acids are there-

fore undesirable in the crude oil because a lower refined

73

74

oil yield is realized and the expense of additional
alkalis required during processing is a significant
expenditure. The free fatty acid results are expressed
as oleic assuming the same molecular weight as oleic.
The difference, if any, is not significant with such a
low acidity. Iodine number concerns oils having only
isolated double bonds and indicates total unsaturation
(Mehlenbacher, 1960). It is a measure of extreme damage
to the oil that is not likely to happen in a dryer. If
several of the more sensitive tests show that damage as
likely, it could have been used. The peroxides have cus-
tomarily been considered as products of initial fat
decomposition (Mehlenbacher, 1960). The peroxide value
units indicate the reactive oxygen content as milliequiva-
lents of oxygen per kilogram of oil or as millimols of
peroxide per kilogram of oil. One millimol of oxygen
equals two milliequivalents of peroxide. Thiobarbituric
acid value was not used because its utility and relia-
bility in this application were not established. Anisi-
dine test could have been used if severe damage had
occurred because it is a measure of secondary oxidation
in oils. This damage was not indicated by the earlier
tests.

The Department of Food Science at Michigan State
University conducted the peroxide value test according to

the American Oil Chemists' Society (AOCS) Official Method

75

Cd 8-53 as listed in Appendix B of this thesis. Free
Fatty Acids were determined also according to the AOCS
Official Method Ca 5a-4O as corrected in 1972 with minor
changes as listed also in Appendix B.

The Oil was extracted by Soxhlet extraction using
hexane as the solvent (Dokhani, 1977). There was some
concern that rapid drying of the beans may affect the
internal structure and result in a change in the oil
yield* (Rodda, 1974; Overhults et al., 1972). To obtain
a more accurate indication of oil yield therefore, anhy-
drous ethyl ether was used as the solvent (Dokani, 1977)
according to the official methods of analysis of the Asso-
ciation of Official Agricultural Chemists for Crude Fat
Determination of Soybean Samples as also listed in Appen-
dix B of this Thesis. The ether recovers a higher per-
centage of the oil from the soybeans than the hexane but
presents some laboratory problems; therefore, it was not
used for all of the extractions.

Germination is a very sensitive indicator of heat
damage. Previous corn experience with this dryer has con-
sistently shown retention of at least some of the germina-
tion when the corn was not rewetted for testing of
multiple passes. To retain germination in grains used for

seed, the maximum grain temperatue would certainly have to

 

*Interview with Dr. Charles Stine, Department of
Food Science, Michigan State University, February 1977.

 

76

be lower than those used here. These soybeans are not for
seed. However, germination at whatever level to which it
is lowered is still a heat damage indicator. It is used
as a quality indicator with that fact in mind. Germina-
tion samples were each of 100 kernels arranged on absor-
bent paper, rolled up in waxed paper, with distilled
water, and stored at approximately 80°F (26.7 C) for a
minimum of 7 days. Only normally sprouted seeds were
counted as germinated.

When farmers sell soybeans, the number of split
beans is used in the market place as a quality indicator.
This is due to the shorter storage life for soybeans
which are cracked or split. Apparently the seedcoat,
when intact, does offer some protection from rancidity
of the oil and from mold growth. For the anticipated use
of this dryer as preparation of the soybeans for immediate
processing, the absolute amount of cracked and Split
kernels is not of great concern. A crack is any fissure
in the surface and a split is broken pieces. Since the
next processing step involves physical crushing of the
soybeans to remove the hulls, breaking of the kernels
prior does not have a detrimental effect. In fact, it
may be beneficial to the process.* Breakage does indi-

cate the stress placed on the individual kernels so this

analysis was also conducted.

 

*Interview with C. M. Westelaken, Westlake Agri-
cultural Engineering, Inc., St. Marys, Ontario, January
1977.

 

77

The samples for both germination and stress cracks
were conditioned for a minimum of one week so that all
samples would be at the same moisture content and subject
to the same amount of drying. Saturated salt solutions
of sodium chloride giving a relative humidity of 75%
(Hall, 1957) at 80°F (26.7 C) were used to condition the
first run samples. An Aminco Aire unit was used to give
the same atmospheric conditions for the second run sam-
ples. The Amino Aire unit uses a water bath and spray
apparatus to establish the dew point temperature. Elec-
tric heaters control the dry bulb temperature. The

moisture content of the samples after conditioning was

10.7% wet basis.

 

TEST PROCEDURE

A uniform lot of soybeans raised from certified
SRF 200 seed by a Mason, Michigan, farmer was used for
the tests. The beans had been stored in a steel bin with
aeration until February (the time of purchase) from the
previous harvest season. They were stored in burlap bags
inside the Agricultural Engineering Building until after
the first test run. Because of the low relative humidity
in the building (about 20%) the soybeans were slowly dry-
ing. By moving the beans outdoors, placing them in a
covered steel bin, and circulating air through the beans
during periods of high relative humidity we gently
increased the moisture content of our stock supply from
about 10.0 to 12.5% for the second run.

Moisture contents of the soybeans were measured
using a Steinlite electronic moisture tester. Comparing
the Steinlite results to oven dry at 210°F (98.9 C) for
48 hours it was found to be high by an average of 0.068%
moisture content wet basis high (s=0.020, d.f.=5). Hall
(1957) indicates a standard error for the Steinlite of
0.44%. This is an acceptable accuracy so because of the
ease of using the Steinlite over the oven dry method, the

Steinlite was used for the moisture contents. Samples

78

 

were placed in self sealing plastic bags at the time of
testing and allowed to come to equilibrium at room tem-
perature for one day before taking moisture content read-
ings.

The Steinlite measures an electrical property
(capacitance) ofthe sample and converts that to moisture
content. Grain fresh from the dryer has a higher moisture

content in the center of the kernels than at the outside

 

edge. Inaccurate readings indicating a lower moisture
content result if this moisture is not allowed to dis-
tribute itself uniformly throughout the kernels.

Actual dryer Operation involved at least two
people. Description of the apparatus appears in Appendix
D of this thesis but a short review of the procedure for
Operation is in order. The concurrent section of the
dryer was first filled with dry grain until the micro
switches on top indicated that it was full. This required
5.875 bushels (0.2070 cubic meters). All recording instru-
ments were switched on. The fan on the concurrent section
was then actuated and the burner was ignited and adjusted
to the desired temperature by manual regulation of the
LPG pressure. Immediately, the cross auger from the base
of the concurrent section was switched on. The shunt
wound DC motor powering to auger served as the grain flow
rate control. The speed control on the motor control

unit was adjusted according to Figure l to give the

80

 

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Houoe on pcao3 ucsnm Emu oomm mo Ommmm Omumu m

 

OOH mm om mm
r n m
1 OH
m.o .
H£\mE . om
HE\ee
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81

desired flow rate. Actual flow rates were computed by
weighing the entire dryer output during each run. Test
beans were then fed in. Steady state conditions were
reached at 5.875 bushels (0.2070 cubic meters) when the
cooler was not used. An additional 2.362 bushels (0.083

cubic meters) were required to fill the cooler and cross

auger. Steady state conditions exist when grain and air
outputs stabilize. The dryer was built so that the out-

put from the concurrent section could be diverted from I”

 

the machine. This gives the capability of using the sys-
tem as a multi-stage concurrent dryer (with only one con-
current section). Tempering time between passes through
the concurrent section is critical to allow moisture to
migrate from the middle of the kernels to the outside. In
calculating the tempering time it is important to consider
also the 2 feet tempering zone at the base of the concur-
rent section.

Countercurrent cooling was used when the grain
flow was not diverted for another pass through the con—
current section as was the case in the second run. The
cross auger dumps directly into the cooler.

Together, 2.362 bushels (0.08324 cubic meters) are
required to fill both the cross auger and cooler. Micro-
switches on tOp of the cooler control the unloading auger

at the base so that a constant bed depth is maintained.

82

Ambient air is used to cool the grain; the cooling fan is
turned on when the cooler was full.

Initially, there had been some concern that the
entry tube to the concurrent section did not adequately
prevent the heated air from escaping out the top. The air
movement through the top was in fact insignificant. Two
thermocouples located in that tube during the second run
(where a heated air temperature of 450°F (232 C) was used)
indicated a temperature increase of only 1.25°F (0.7 C)
as the grain entered through that tube.

The basic dryer design should permit testing of
nearly all common grains such as oats, wheat, rye, corn,
soybeans, etc. The slope of 60° on interior grain flow
diversion parts is greater than the angles of repose of
any of these grains. Even flow of grain through the
dryer was not considered as a problem with this system.
Although no special attention was given to the problem,

no scorched kernels were evident after multiple passes.

 

in evaluation of the individual runs of the dryer.
Energy consumption calculation was the primary purpose of
the program but it also gives some indication of the g

experimental technique. The program was written to be

RESULTS AND DISCUSSION

Calculation Procedure

 

A short computer program was developed to assist

 

 

run as batch, not online with a teletype. Minor changes

would be required for teletype use.

Inputs for each run (or pass) take 3 cards on

which the data should be arranged as follows:

Card #1

le-J

Care #2

DWNH

Each of the following variables may take an F10
field beginning at the left edge of the card
(all real numbers).
run number
temperature Of the plenum (°F., F=[(9/5)C] + 32)
absolute humidity into concurrent section at
ambient temp.
'dry bulb temperature of ambient air into con-
current section (F)
absolute humidity exhausted from concurrent
section
airflow at ambient of concurrent section (CFM,
CFM=cubic meters per minute/0.02831685)
density of ambient air into concurrent section
[cubic feet per pound, CFP=7.769 (cubic meters
per kg)]
All real numbers (4 F10 fields from left).

run number

counterflow section airflow (CFM)
absolute humidity of counterflow exhaust
absolute humidity into counterflow

83

84

Card #3 All real numbers (7 F10 fields from left).

1 run number

2 grain flow rate out (lbs per min, PM=2.2046kg

per min)

moisture content wet basis of grain in (decimal)
moisture content wet basis of grain out (decimal)
temperature of grain in (F)

temperature of grain out (F)

test weight of grain out (lbs per bu, PB=0.7769kg
per m3)

\lO‘U‘lnbw

End of data type "0.5" in first 10 spaces of separate
card

The calculations assume LPG to have 19,444 BTU
per pound (1.800 kg cal/kg), air to have a specific heat
of 0.25 BTU per lb °F (0.0002390 J per kg K), and the air~
density to be the same going into both the concurrent and
counterflow sections. Changes in the energy held by the
grain in and out use the specific heat equations from
Kazarian (1962). As the LPG burns it is assumed to add
1.63 pounds of water to the air per pound of gas burned

(Perry, 1973).

More than one set of conditions may be analyzed
during a computer run. Each set of 3 cards must have the
number of the run (whole real number) in the first 10
spaces of each set of cards. The only end of data card
is placed at the end of the entire data stack. No two
consecutive runs may have the same run number. Individual
run labels are printed as whole numbers only.

If the cooler is not used, card #2 of the run

should read as follows:

 

85

Card #2 All real numbers (4 F10 fields from left).

run
0.0

absolute humidity into concurrent at ambient
absolute humidity into concurrent at ambient

nwmw

This may be used if an analysis of the individual steps
of a multistage run is desired. There is no provision to
analyze an entire multistage run as one unit in this pro—
gram. The individual stages must be entered as separate

runs.

Because cross-sectional area figures do not enter
into the program, it may be used for other concurrent
dryers in the field of any cross sectional area. The pro-
gram output consists of the following:

1. all input data
2. water removed from the grain per hr*
water removed by the air per hr*
airflow in concurrent section (lbs per hr)
grain flow rate out (lbs per hr)
change in grain energy due to difference in
temperature and moisture content in and out
net energy into system (total minus change
in grain energy)
8. total energy into the system (based on air-
flow, LPG burned, and specific heat of air)
9. LPG burned (based on total energy)
10. energy used to remove water from the grain
11. water removed from the grain (lbs per bushel)

ONU'IALU
o o o o

\l

The following output is used if the counterflow cooling

section is used:

12. water removed in the concurrent section by

the air
13. airflow in the counterflow section (lbs per

hr)

 

*These two items vary from equality only by
measurment error.

 

86 ‘

The program has assisted in the analysis because
fewer hand calculations are required. The program is
listed in Appendix A.
The calculations for one run are shown also. This
data is from a corn run (2—22-77) that will be referred
to later. The cooler was used in this example. I

ambient dry bulb temperature
TDBI 58°F
14.4 C *

absolute humidity into concurrent section I
AHIO 0.007 lb per lb* .1

airflow in concurrent flow at ambient
AIRH 135 CFM**
3.82 cubic meters per min.

 

ambient air density
CFP 13.7 cubic ft per lb*
1.76 cubic meters per kg

heated air temperature

TH 400° F
204 C
absolute humidity of concurrent flow exhaust
AHO 0.075 1b/1b*
airflow in counterflow
AIRC 21.CFM**

0.59 cubic meters per min.

absolute humidity of counterflow exhaust
AHOC 0.038 lb/lb

grain flow rate out
PM 5.06 lb/min
2.30 kg/min

moisture content in wet basis
WCI 0.2377 decimal

moisture content out wet basis
WCO 0.1551 decimal

 

*Obtained by use of standard ASHRAE psychro-
metric charts.

**Obtained by pressure drop across laminar flow
element.

87

grain temperature in

TI 42. °F
5.6 C
grain temperature out
TO 64. F
17.8 C
test weight out
BBQ 50 lb/bu

644 kg/cubic meter

absolute humidity into cooler
AHIC 0.007 lb/lb*

Example calculations:

PM*60 (min/hr)
5.06*60=303.6 1b/hr

TOT (grain flow rate out)

137.7 kg/hr
CAP (grain flow rate out) = 303.6 (lb/hr)/BDO
= 303.6/50
= 6.07 bu/hr
0.214 cubic meters/hr
DM (dry matter = TOT*(l-WCO)
= 303.6*(1-0.1551)
= 256.5 lb/hr
116.3 kg/hr

WI (pounds of water in grain in per hour)
WCI*DM/(1-WCI)
0.2377*256.5/(1-0.2377)
79.98 lb/hr

36.29 kg/hr

WO (pounds of water in grain out per hour)
= WCO*TOT

0.1551*303.6

47.09 lb/hr

21.36 kg/hr

WWR (pounds of water removed from grain per hour)
WI-WO

79.98-47.09

32.89 lb/hr

14.93 kg/hr

 

*Obtained by use of standard ASHRAE psychrometric
charts.

 

 

88

TGE (change in energy of grain due to changes in tempera-

ture and moisture content in and out)

= TO*[.35 + (.851)*WCO] *TOT—TI*

[.35 + (.851)*WCI] *WI/WCI
64.* [.35 + (.851)*0.1551]*303.6-42.*
[.35 + (.851)*0.2377]*79.98/0.2377
1560.4 BTU/hr
1646300. j/hr

PH (pounds of dry air per hour through concurrent section)
AIRH*60./CFP

135.*60./13.7

591.2 lb/hr

268.2 kg/hr

AHI (aboslute humidity of air into dryer after heating)

= AHIO + (TH-TDBI)*(.25 BTU/lb F)
(lb.LPG/l9444 BTU) (1.63 lb water/lb LPG)
0.007 + (400.-58)*0.25/19444*l.63
0.0142 lb/lb

AHRA (pounds of water removed by air in the concurrent
section per hour)

(AHO-AHI)*PH

(0.075-0.0142)*591.2

35.94 lb/hr

16.30 kg/hr

PHC (airflow in cooler)
(AIRC/CFP)*6O
(21./l3.7)*60
92.0 lb/hr
41.7 kg/hr

AHR (pounds of water removed by the air in both sections)
AHRA + (AHOC-AHIC)*PHC

35.94 + (0.038-0.007)*92

38.79 lb/hr

17.60 kg/hr

BTU (net energy into system)
(TH-TDBI)*O.25*PH-TGE
(400—58)*0.25*59l.2—1560.4
48987.2 BTU/hr

51684200. j/hr

 

89

GBTU (gross energy into system)
BTU + TGE
48987.2 + 1560.4

50547.6 BTU/hr
53330500. j/hr

PRO (propane burned per hour)
GBTU/19444
50547.6/19444
2.60 lbs/hr
1.18 kg/hr

BTUPP (energy consumed per pound of water removed)

BTU/WWR H
48987.2/32.89

1489.4 BTU/1b

827.44 kg/cal/kg

I" m- I.“ A"‘(

WBU (water removed from grain)
BDO*WWR/TOT
50.*32.89/303.6
5.417 lb/bu

6.9 kg/cubic meter

In comparing the above calculated values to those
found in the computer output shown in Appendix A for corn
of 2/22/77 the answers are quite close. The differences
are due to rounding off errors in the longhand calcula-
tions. Two corn runs have been included in the appendix
to show how the program works. In addition to the one
previously mentioned there is also data for corn from
3/8/77. These two runs used the same corn but it was
rewetted in between runs with distilled water and allowed
to come to equilibrium for a week at 40°F (4.4 C) prior

to drying. The water calculated to have been removed by

90

the air and the water calculated to have been removed from

the grain should be equal. If these two numbers fail to
be equal there is a measurement problem somewhere. For
the February run the grain to air water removal ratio was
32.90/39.06 or 0.84. For March it was 46.76/42.02 or
1.11. These values are both reasonably close to 1.00.

At least close enough to consider the measurements used
to calculate those values (airflows, humidities, moisture
contents, and grain flow rates) as within an acceptable
range. Keep in mind that here are large changes in mois-
ture contents during drying and quite high exhaust air
relative humidities. Humidities were measured using wet
and dry bulb thermocouples that would only indicate rela-
tive humidities too high. Inadequate wet bulb depression
results from insufficient air velocity or improper design
and location.

Several observations can be made concerning the
results to be expected when using rewetted grain (corn in
particular). The test weight dropped, concurrent airflow
increased, and the energy consumed per pound of water
removed decreased. Physical breakdown of the kernel
structure is likely to be the cause of the energy con-
sumption decrease. This suggests the use of artificially
rewetted corn for research data may be less than desirable

from a standpoint of accuracy.

 

91

Sgybean Test Data

 

A "run" is one complete processing cycle on a
quantity of soybeans. A "pass" is that part of the cycle
where the soybeans go through the concurrent section once.
On 2/4/77 the first run was made and an attempt to acquire
data on two passes was only partially successful. The
3/15/77 run was a single pass. In Appendix A three sets

of soybean data are listed. For 2/4/77 the first run

'3" __“‘—w

first pass and first run second pass are listed. For
3/15/77 only one pass was conducted so only one set of
results is relevant. A time schedule Of when each grain
sample was organized when data for each pass was collected
and assisted in determining when steady state operating
conditions were reached. As mentioned earlier, 5.875
bushels (0.2070 cubic meters) are required to fill the
concurrent section. Since in the first run the grain
flow rate was 588 1b/hr (266.7 kg/hr) with a test weight
of 57 lb/bu (734 kg/cubic meter) steady state was reached
in 34.2 minutes. The cooler was not used in the test.
Also to be considered is the fact that a pass of grain
into the dryer takes 34.2 minutes to mass through. The
last input sample was deleted from the analysis because

it was not typical in relation to the other values and

92

no output samples were taken at 34.2 minutes. For the
input moisture content (wet basis) of the first run-

first pass of 13.6% the sample standard deviation(s)

was 0.12 with 3 degrees of freedom (d.f.). Output samples
were collected from the dryer spout and sealed in plastic
bags also. The warm grain was not allowed to exchange
moisture with the ambient air. The average output mois-
ture content of the first run first pass was 11.4% with

a s=0.43 and d.f.=4.

Between passes the grain was tempered for approxi-
mately 35 minutes. Additional samples were taken as this
first pass output grain was fed into the dryer as input
second pass grain. The surfaces of the containers were
exposed to ambient air for a time and it is possible that ‘
some moisture, at least from the container surfaces may
have evaporated to the air from the war grain during this
period. The samples were taken from the surface. They
indicated a lower moisture content (0.6% MC wb) than the
samples taken at the output spout. Those samples were
therefore not included in the analysis.

Output moisture content of the first run-first
pass was used as the input to the first run second pass.
The output to the first run second pass posed other diffi-
culties. An error predicting when steady state conditions

of the output would occur resulted in termination of

93

sampling too soon. Referring to the times of sampling
schedule, and the fact that at 588 lb/hr (266.7 kg/hr)
34.2 minutes are required to reach equilibrium, there was
only one valid output sample. The sample was collected
only one minute after equilibrium had been established.
Basic statistics would not put much value on a single
sample but it is in the likely range and had to be used
for the inferences to be made from this analysis.

Data collection for the second run (3/15/77) was
more consistent. It was a single pass run and the cooler
was used. For the inlet moisture content of 12.5% wb
s=0.l4 and d.f.=ll. The outlet moisture content of 10.6%
wb had s=0.l6 and d.f.=7. Some additional static pressure
data was collected to use as a check on the airflow
determined by use of the laminar flow element on the con-
current section. The bed depth in the concurrent section
was 3 feet. Several holes were drilled into the wall of
the dryer to check the drop in static pressure across the
bed. Comparing this pressure drop to Shedd's data (1953)
for soybeans an estimation of airflow was obtained.
Between the l and 2 feet bed depths there was a pressure
drop of 1.8 inches (4.6 cm). Interpolation beyond the
range of the chart (if this is accurate) gives an airflow
of at least 120 CFM (3.40 cubic meters/min) which is in
the neighborhood of the 141 CFM (4.0 cubic meters/min)

determined by pressure drop across the laminar flow

94

element. Since this interpolation is somewhat question-
able the laminar flow element figure was used for the cal-
culations.

The weight of water removed from the grain and
the total water removed by the air (grain to air water
removal ratio) do not balance for any of the 3 sets of
soybean data. For the first run first pass it is 14.97/
33.58 or 0.46, for the first run second pass it is 14.27/
27.61 or 0.52, and for the second run it is l4.33/35.20
or 0.41. It is apparent that an error of approximately
the same magnitude occurred in all 3 cases. The corn
data was obtained with the same equipment between when the
two soybean runs were made. This indicates that it is
likely to be a problem typical to only the soybean runs.
In reviewing the accuracy of the measurements, the grain
flow rate is correct because total output was weighed and
timed. Moisture content error is small as discussed
earlier. So the water removed from the grain is probably
reasonable. Moving to the airflow measurements, there was
airflow through the concurrent section similar to what
occurred with corn (123 to 146 CFM at the extremes).

Inlet absolute humidities were measured with a Bendix
Aviation psychrometer. Outlet absolute humidities were
measured through the use of wet and dry bulb thermo-
couples placed in the 4 inch (10.2 cm) diameter exhaust

port of the concurrent section. The airflow across the

95

wet bulb wick according to Brooker et a1. (1974) must be
at least 15 ft/sec (4.57 m/sec) to obtain maximum wet
bulb depression. The mean air velocity through the 4
inch port at 123 CFM (3.48 cubic meters/min.) is only
10.7 ft/sec and at 145.5 is 12.7 ft/sec. Calculation of
Reynolds number indicates the air to be in turbulent flow.
Therefore, the velocity over the wet bulb wick is nearly
equal to the mean velocity. The web bulb temperature was
the measurement most likely to be in error because the
other measurements are more stable. The other measure-
ments can be used to recalculate the concurrent exhaust
humidity and determine what the actual wet bulb tempera-
ture was. Carrano (1970) had the same problem with his
dryer and used a similar approach in his analysis.

Shown below are the calculations for the first run
first pass. Following those calculations Table 1 shows
the results of the same series of calculations for all
three sets of soybean data. The table shows the calcu-
lated wet bulb temperature measurement to have been con-
sistently at least 12.5° F lower than the measured values
for the soybean tests.

Threlkeld (1962) has published data showing errors
in wet bulb temperature measurement as a result of radia-
tion error and low airflow. Although the wet bulb

depression was only 20°F‘ (11.13) and maximum air

96

TABLE l.--Humidity Corrections Calculation Example
(First Run First Pass).

 

 

 

Conditions
Drying Parameters Physical Quantities*
WWR 14.97 lb/hr
6.79 kg/hr
AHIO 0.003 lb/lb
PH 573.1 lb/hr
260.0 kg/hr
TH 350° F
177 C
TDBI 68° F
20 C
Concurrent exhaust dry 152° F
bulb temperature 67 C

 

*Calculations

 

AHIO + [(TH-TDBI)*().25)(1/19444)(1.63)]
0.003 + [(350.-68.)*(0.25)(1/19444)(l.63)]
0.00891 lb/lb

AHI

Outlet absolute humidity
AHI + WWR/PH

0.00891 + 14.97/573.1
0.0350 lb/lb

97

temperature only 120°F (49. C) for the data listed in
Threlkeld (1962) the trend indicates a maximum wet bulb
temperature measurement error due to both radiation and
airflow rates to be of only about 0.5°F (0.3 C) for the
soybean data presented here. If in fact the error does
lie in wet bulb temperature measurement, the error could
also result from conduction through the wick to both the
distilled water and the thermocouple wire.

Standard errorsixlthe measurements considered as
accurate should be examined to see if they can account
for the apparent error in wet bulb temperature measure-
ment. Loeffler (1966) indicates the accuracy of iron—
constantin thermocouples (type J) to be : 4.0°F (:2.2 C).
Type J thermocouples were used to sense the heated air
temperature. Type T thermocouples (copper-Constantin)
were used through the rest of the dryer and have an accu-
racy of i l l/2°F (0.8 C) in the temperature range of
-75 to 200°F. The Steinlite moisture tester manufacturer
states its moisture tester to have an accuracy of :0.44%
MC wb. The platform scale used to weight the output grain
is calibrated to an accuracy of i 1/8 lbs (0.06 kg). With
the five weight measurements averaged for the first run,
the total error in weight would be 1 5/8 lbs (0.3 kg).

The airflow measurement with the Meriam Laminar
flow element and manometer is claimed to be quite accur-

ate. However, to be more realistic in case dirt and bees'

 

98

wings were present in the cone assembly of the lamimar
flow element an accuracy of i 10 CFM (0.28 cubic meters/
min) will be considered.

Recalculation with all the above standard measure-
ment erros combined gives the following information in
relation to the first pass first run soybeans in Appen-
dix A. The weight of water removed from the grain is
i 6.05 lb/hr, total water removed by air is i 3.66 lb/hr.
The net energy figure is i 4432 BTU/hr, gross energy
i 4961 and energy used to remove water from grain : 822
BTU/1b. These large cumulative errors may help to explain
some of the difference between the weight of water
removed from the grain and weight of water removed by the
air but do not account for the entire difference. The wet
bulb temperature measurement appears to be quite inaccu-
rate.

To acquire information on the temperatures within
the concurrent stage of the dryer, three thermocouples were
installed through the side at 6 inches (15.2 cm), 1 foot
(30.5 cm), and 2 feet (61.0 cm) down into the bed pro-
truding into the bed 1 3/4 inches (4.46 cm). The indi-
cated temperatures are values somewhere between the air
and the grain temperatures. Surface conduction heat
transfer takes place between the thermocouples and the

kernels and convection heat transfer takes place between

 

99

the thermocouples and the air. The measured data appears
later in the thesis.

Bakker-Arkema et al. (1974) have developed a com-
puter simulation model to describe the drying process
within a concurrent flow grain dryer. A thin-layer equa-
tion must be supplied in the program for the particular i
product to be dried. For soybeans the Sabbah et al. (1976)
thin-layer equation for beans was used. Computer outputs
for both the first and second runs are included in Appen- A
dix C. In Figure 2 the air and grain temperatures are
plotted as curves and the measured temperatures from
within the bed as points for the first run-first pass.

The maximum measured temperature in the first run first
pass was 160°F (71 C) at the 2 feet level. The program
predicts a maximum grain temperature of 150.8°F (66 C) but
the two peaks occur at different locations. The predicted
output moisture content of 11.97% wb is close to the
actual value of 11.1% wb. The calculated final air rela-
tive humidity was about 3% lower and exhaust air tempera-
ture 3 to 21°F (12 C) higher (Table 2).

For the first run second pass, Figure 3 shows pre-
dicted air temperature, predicted grain temperature, and
measured bed temperatures. Once again the measured values
do not appear to fall between the air and grain predicted

temperatures. Notice also that the simulation predicted

100

Figure 2.--Predicted v. Actual Bed Temperatures for the
First Run First Pass.

 

450

400

Temperature
°F

300

200

100

50

101

 

Air Temperature Predicted

Measured

k\\\‘fi‘ Values

I
‘\-Measured

Values

 

 

Grain Temperature Predicted

 

 

' V v

1 2
Bed depth (ft)

0

200

°C

100

V'

 

102

TABLE 2.--Calculated and Measured Exhaust Wet Bulb

 

 

Temperatures.
First run First run Second
First pass Second pass Run
WWR lb/hr 14.97 14.27 14.33
kg/hr 6.79 6.47 6.50
AHIO lb/lb 0.003 0.003 0.006
PH lb/hr 573.1 550.7 622.1
kg/hr 260.0 249.8 282.2
TH °F 350. 300. 450.
C 177. 149. 232.
TDBI °F 68. 68. 74.
C 20. 20. 23.
Dry Bulb Concurrent
Exhaust Temperature
°F 152. 155. 171.
C 67. 68. 77.
AHI lb/lb 0.0089 0.0079 0.014
Calculated outlet
Absolute Humidity .
lb/lb 0.0350 0.0338 0.0372
Calculated Relative
Humidity
% 20. 18. 14.
Calculated Wet Bulb
Temperature
°F 103. 102. 106.
C 39. 39. 41.
Measured Wet Bulb
Temperature
°F 118. 115. 120.
C 48. 46. 49.
Error in Wet Bulb
Temperature Measurement
°F +15. +12.5 +13.5
C + 8.3 + 6.9 + 7.5

 

 

103

a 20°F (11 C) higher temperature than was recorded in the
experiment. The simulation predicted well on the amount
of drying (1.85% to 1.87% wb reduction) but the calculated
relative humidity was again higher (by 3%) and exhaust air
temperature higher (3°F, 2 C) (Table 2).

On the second run a heated air temperature of
450.°F was used. Figure 4 shows the predicted versus
measured temperature values. Peak grain temperatures were

in the same are of the bed but predicted grain tempera-

 

ture was 5°F (3 C) too high. The simulation indicates
drying of about 0.25% wb more. The calculated exhaust
relative humidity (RH) of 14% and temperature of l7l°F
(77 C) compare favorably with the 16% RH and 150°F (70 C)
predicted.

To compare the soybean results with those of corn,
the same operating conditions as for the first run first
pass soybeans and the conditions of the second run were
used. Once again the concurrent dryer simulation was
used but this time the Thompson thin-layer equation for
corn was used. The output has been included in Appen-
dix C. Corn seems more difficult to dry in the 13% to
9% wb range. However, it is seldom necessary to dry corn
below 12% wb. Relative humidity and equilibrium moisture
contents determine how dry a product must be for safe
storage. Soybeans must be dried to about lO-ll%:corn to

l4.5-15.5%. As a product dries, the energy required to

104

Figure 3.--Predicted v. Actual Bed Temperatures for
the First Run Second Pass.

105

 

 

 

 

m
0 0.5 1,0
450 . .
4001
- 200
Temperature
OF 0C
300-
I
Air Temperature
Predicted
. 100
2004
\\__Measured Values
100. Grain Temperature
Predicted
50 . I

Bed depth (ft)

106

Figure 4.--Predicted v. Actual Bed Temperatures for
the Second Run.

107

 

 

 

 

 

 

 

m
0.5 1.0
450 ** ‘ ‘
400
.200
Temperature
OF °C
300
Air Temperature
,r////—_ Predicted
.100
200
I
t
\_ xix ‘1
Measured Values
Grain Temperature
100 Predicted
50 , , ,
l 2 3

Bed depth (ft)

 

108

remove an additional quantity of water increases. In gen-
eral it is probably more likely that corn will dry more
rapidly and with lower fuel requirements because higher
final moisture contents may be acceptable. Brook* sug-
gests some differences in drying rates may be due to dif-
ferences in particle size. i
The Sabbah thin-layer equation for beans may have

application in the concurrent dryer simulation for pre-

v“- u'. ‘ LL“
.
I

diction of maximum soybean temperatures in the dryer. >4

 

Unfortunately, there apparently is no temperature and
time v. quality data to use for management but the simula-

tion can be used when the information becomes available.

Quality Analysis Results

Germination of the soybeans was above 50% for all
samples. For counting of cracks in individual beans
(cracks are defined as any fissure in the surface) two
Operators were used. One for each run. This makes the
results between runs somewhat less than absolutely compar-
able because of the subjectivity of the Operators. How-
ever, the trends are the same. Table 3 shows germination,
cracks, maximum predicted temperatures, maximum measured
bed temperatures and heated air temperatures. The method

of counting splits, or broken soybean pieces, was not

 

*Interview with R. C. Brook, Research Associate,
Department of Agricultural Engineering, Michigan State
University, March 1977.

109

TABLE 3.--Concurrent Exhaust Relative Humidity Predicted
v. Calculated Values.

 

First Run First Run

First Pass Second Pass Second Run

 

Air Temperature

Measured
F 152. 155. 171.
C 67. 68. 77.
Relative Humidity
Calculated
% 20 l8 14
Air Temperature
Predicted
F 131. 152. 158.
C 55. 67. 70.
Relative Humidity
Predicted
% 22 15 16

Difference Between

Measured and Pre—

dicted Relative

Humidity -2 +3 -2

 

110

accurate enough to be included but few splits did occur.
The number of splits was certainly less than 1%.

It is apparent that even though the soybeans may
have reached the critical quality temperature of 175°F
(79 C) (as indicated by Bunn, 1970) there was no extreme
decrease of germination. This indicates that temperature
is related to quality but the time at a given temperature
is also very important. Referring to the computer simu-
1ation, the soybeans were at their maximum temperature for
relatively short periods of time. Drying caused only
small changes in germination and cracking percentages in
the operation planned as one of the early steps in soybean
oil extraction. Decreasing the grain flow rate from what
was used in the tests will increase the amount of drying
but will increase the grain tempertature within the dryer
and may adversely affect the quality.

Samples were combined to provide two inlet and
two outlet samples per run to be processed for quality by
the Food Science Department. Four duplicates of each test
were processed. Table 4 shows the results of the analy-
sis.

There was no significant change in quality as
measured with the tests after drying of the soybeans in a
concurrent flow dryer. The peroxide value would have been

the first indicator of deterioration and it remained

 

 

111

 

TABLE 4.--Germination and Stress Cracks of the Soybean

 

 

Samples.
First Run First Run
First Pass Second Pass Second Run
Heated Air
Temperature
F 350. 300. 450.
C 177. 149. 232.

Maximum Predicted
Temperature of

 

Soybeans
F 156. 181. 192.
C 69. 83. 89.
Maximum Measured
Temperature
F 160. 152. 182.
C 71. 67. 83.
% germination
before drying 99. 66. 99.
after drying 66. 51. 57.
% cracks
before drying 2. l8. . 1.

after drying 18. 37. 21.

 

112

unchanged. The oil quality was superior before as well
as after drying (Dokhani, 1977).

Some interior breakdown of the physical soybean
structure may have occurred and as a result the allowable.
storage life may have decreased. Stine* noted that none
of these quality indicators would measure such a problem.
For use as a dryer in an oil extraction plant, however,
storage will likely be only for a very short period.
Thus, interior breakdown, if it exists, is not a major
concern. If breakdown of the soybeam structure occurres,
the oil yield may be favorable affected due to easier

extraction; the test did not show a significant change in

oil yield.

TABLE 5.-—Results of Chemical Oil Analysis.

 

First Run

First Pass Second Run

 

% Crude Fat
Before drying 18.06 16.88
After drying 18.20 17.14

Peroxide value as milliequi—
valents of peroxide per
kilogram of Oil

Before drying <0.0l <0.01

After drying <0.01 <0.01
% Free Fatty Acids as Oleic

Before drying 0.192 0.176

After drying 0.176 0.205

 

 

*Interview with Dr. Charles Stine, Department of
Food Science, Michigan State University, February 1977.

 

CONC LUS I ONS

 

1. Air temperatures of at least 450.°F (232 C)
may be used to dry soybeans from 13% to 9% in a concurrent
flow dryer without significant reduction of the resulting '
oil quality provided the flow rate is adjusted to less 4

than 10 bushels per hour square foot (0.032 cubic meters

 

per hour square meter). There is likely to be a limit
not far from these values for oil quality to suffer dele-
terious effects but the limiting temperature, grain flow
rate, and moisture content range have not yet been deter-
mined.

2. Mechanical leveling devices are not necessary
on the concurrent bed surface for introducing the wet
grain.

3. It is possible to have a concurrent dryer
function effectively without the use of rotary airlocks
to control air and grain movement.

4. Instrumentation to continuously monitor mois-
ture content in the dryer would assist in management.

5. The difference in temperature between the
inlet cooler air and outlet grain temperature of about
40°F (22 C)_ probably did not stress the soybeans.

6. Reduction of moisture content in the cooler was

not very high.
113

SUGGESTIONS FOR FURTHER STUDY

DevelOpment of instrumentation to accurately
record the exhaust air relative humidity and continuously
monitor grain moisture content would greatly assist lab-
oratory work in this area. Future work should also
include statistical evaluation of drying parameters to
find optimum conditions for both energy efficiency and
high quality grain output. Computer simulation models
predicting output moisture content with changing inlet
moisture contents would assist in the management of dry-
ing Operations.

Quality tests to be considered should include
more than those of oil analysis. Protein Dispersibility
Index and Nitrogen Solubility Index should be included as
measures of heat damage to the protein of the soybeans.
Changes in safe length of storage for retention of quality
due to any interior structural breakdown should be con-
sidered if the dried soybeans are not immediately proc-
essed. The relationship of quality to grain flow rate

and moisture content decrease should also be investigated.

114

PAGE

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APPENDIX A

CONCURRENT DRYER ANALYSIS PROGRAM

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119

APPENDIX B
CHEMICAL OIL ANALYSIS PROCEDURES

SAMPLING AND ANALYSIS OF COMMERCIAL FATS AND OILS
A.O.C.S. Official Method Ca Sal-40

Revised 1971
Corrected 1913

Free Fatty Acids

Definition: This method determines the free fatty acids existing in the

sample.

Scope: Applicable to crude and refined vegetable and marine oils and

animal fats.

A. Apparatus:

1.

Oil sample bottles, 115 or 230 ml. (‘1- or 8 oz.) or 250-m1 Erlenmeyer
flasks.

B. Reagents:

1.

2.

Ethyl alcohol, 95% (U.S.S.D. Formulas 30 and 3A are permitted).
The alcohol must give a definite, distinct and sharp end-point with
phenolphthalein and must be neutralized with alkali to a faint but
permanent pink color just before using.

Phenolphthalein indicator 50111., 1% in 93% alcohol (see Note 1).

 

 

 

3. Sodium hydroxide solns., accurately standardized.
0. Procedure:

F. r. A. Range. <7. Grams of sampled MI. 0! Aleuhol Strength cit—Alkali
0.00 to 0.2 56.4 :t 0.2 50 0.1 N
0.2 to 1.0 28.2 1:0.2 50 0.1 N
1.0 to 30.0 7.05 $0.05 75 0.25 N
30.0 to 50.0 7.05 $0.05 100 0.25 or 1.0 N
50.0 to 100 3.525 1' 0.001 100 1.0 N

 

 

 

 

1. Samples must be well mixed and entirely liquid before weighing.
2. Use the table above to determine quantities to be used with various

ranges of fatty acids. Weigh the designated size of sample into an
oil-sample bottle or Erlenmeyer flask (see Note 2).

. Add the specified amount of hot, neutralized alcohol and 2 ml. of

indicator.

. Titrate With alkali shaking vigorously to the appearance of the first

permanent pinl: color of the same intensity as that of the neutralized
alcohol before addition of the sample. The color must persist for
30 seconds.

D. Calculations:
1. The percentage of free fatty acids in most types of fats and oils is

calculated as oleic acid, although in coconut and palm kernel oils
it is frequently expressed as lauric acid and in palm 011 in terms of
palmitie acid.

a. Free fatty acids as oleic, % =
Ml. of all-tall X N X 28.2

\Vcight of sample

 

b. Free fatty acids as lauric, % =
Ml. ofallgaii X N X 20.0

lVeight of sample

 

120

 

121

SAMPLING AND ANALYSIS OF COMMERCIAL FATS AND OILS

 

Free Fatty Acids Ca Sat-40

Page 8 .

c. Free fatty acids as palmitie, % =
Ml. of alkali X N X 25.6

“Veight of sample

 

2. The free fatty acids are frequently expressed in terms of acid value
instead of % free fatty acids. The acid value is defined as the num-
ber of mg. of KOH necessary to neutralize 1 g. of sample. To
convert % free fatty acids (as oleic) to acid value, multiply the
former by 1.99.

1:. Notes:

1. Isopropanol, 99% may be used as an alternate solvent with crude
and refined vegetable oils.

2. Cap bottle and shake vigorously for one minute if oil has been
blanketed with carbon dioxide gas.

 

122

SAMPLING AND ANALYSIS or COMMERCIAL FATS AND OILS
A.O.C.S. Otiicial Method Cd 853

Oflchl 1950

 

Peroxide Value

Definition: This method determines all substances, in terms of mini-equiv-
alents of peroxide per 1000 grams of sample, which oxidize potassium
iodide under the conditions of the test. These are generally assumed
to be peroxides or other similar products of fat oxidation.

Soaps: Applicable to all normal fats and oils including margarine. This
method is highly empirical and any variation in procedure may result
in variation in results.

A. Apparatus:
1. Pipet, Mohr, measuring type, l-ml. capacity.
2. Erlenmeyer flasks, glass-stoppered, 250 ml.

B. Reagents:

1. Acetic acid-chloroform solution. Mix 3 parts by volume of glacial
acetic acid, reagent grade, with 2 parts by volume of chloroform,
U.S.P. grade.

2. Potassium iodide solution, saturated solution of KI, A.C.S. grade, in
recently boiled distilled water. Make sure the solution remains satu-
rated as indicated by the presence of undissolved crystals. Store in
the dark. Test daily by adding 2 drops of starch solution to 0.5 ml.
of the potassium iodide solution in 30 m1. of acetic acid-chloroform
solution. If a blue color is formed which requires more than 1 drop
of 0.1 N sodium thiosulfate solution to discharge, discard the iodide
solution and prepare a fresh solution.

3. Sodium thiosulfate solution, 0.1 N, accurately standardized.

4. Sodium thiosulfate Solution, 0.01 N, accurately standardized. This
solution may be prepared by accurately pipetting 100 ml. of the 0.1 N
solution into a 1000-ml. volumetric flask and diluting to volume with
recently boiled distilled water.

5. Starch indicator solution, 1.0% of soluble starch in distilled water.

C. Procedure for Fats and Oils:

1. Weigh 5.00 i- 0.05 g. of sample into a 250-ml. glass-stoppered Erlen-
meyer flask and then add 30 ml. of the acetic acid-chloroform solu-
tion. Swirl the flask until the sample is dissolved in the solution. Add
0.5 m1 of saturated potassium iodide preferably using Mohr type
measuring pipet.

2. Allow the solution to stand with occasional shaking for exactly 1
minute and then add 30 ml. of distilled water.

3. Titrate with 0.1 N sodium thiosulfatc adding it gradually and with
constant and vigorous shaking. Continue the titration until the, yel-
low color has almost disappeared. Add ca. 0.5 ml. of starch indicator
solution. Continue the titration, shaking the flask vigorously near
the endpoint to liberate all the iodine from the chloroform layer. Add
the thiesulfate dropwise until the blue color has just disappeared.

Note: If the titration is less than 0.5 ml., repeat the determination
using 0.01 N sodium thiosulfate solution.

‘11"; ‘

 

 

123

SAMPLING AND ANALYSIS OF COMMERCIAL FATS AND OILS

 

Peroxide Value Cd 8-53
Page 3
4. Conduct a blank determination of the reagents daily. The blank titra-

tion must not exceed 0.1 ml. of the 0.1 N sodium thiosulfatc solution.

D. Calculation:

.1.

Peroxide value as milliequivalents of peroxide per 1000 g. of sample ==
(S—B) (N) (1000)

B = Titration of blank ,
weight of sample

 

S = Titration of sample.
N = Normality of sodium thiosulfate solution.

E. Procedure for Margarine:

1.
2.

Proceed as directed above in Paragraphs 1 through 4 after prepara-
tion of the sample as directed below.

Melt sample by heating with constant stirring on hot plate set at
low heat, or by heating in air oven at (SO-70°C. Avoid excessive
heating and particularly prolonged exposure of oil to temperatures

above 40°C.
. When completely melted, remove the sample from the hot plate or

oven and allow to settle in a warm place until the aqueous portion
and most of the milk solids have settled to the bottom.

. Dceant the oil into a clean beaker and filter through a \Vhatman

No. 4 paper (or equivalent) into another clean beaker. Do not reheat
unless absolutely necessary for filtration. The sample should be clear
and brilliant.

124

CRUDE FAT DETERMINATION OF SOYBEAN SAMPLES

(Official Methods of Analysis of the Asso-
ciation of Official Agri. Chemists)

The whole batch (about 1.0 lb) of soybean was
ground in a Wiley Mill for 5.0 min. The ground sample
was dried in a vacuum oven (v.o.) at 100°C and 29 inches
pressure for 5.0 hours. It was then cooled in a desic—
cator.

About 2.0 grams of v.0. dried sample was weighed
accurately with a microbalance and soxhlet extracted
with anhydrous ethyl ether for 12.0 hrs., and the yield
of crude fat extract was determined as percent. In

all trials duplicates were used.

(Written by S. Dokhani)

APPENDIX C

COMPUTER SIMULATIONS

FONCUFRENT STAIN DRYER SIMULATION
USING THE SABBAH THINLA ER EUUQTIUN FOR BEANS

INFUT CONFITIUN:
NUAUKH OF STAUES TU BE SIMULATED 1
AMBIENT TEMP. F7
INLET MOISTUVE CONTENT: UET BASIS PERCENT12.47

STWGC 1 INPUT LUNUIIIUNS:

IHLTI 61H TLKV. F400.

INLET 6P3 HUM RfiTI0.0063

AIRFLCU RATE. CFM/Bu FTiAT AMBIENT CONDITIONS) 141.

LRRLN FLLM RATE. BU/HR/SG FT 11.38

LAYER LENGTH. FT 3.

OUTPUT INTERVAL FT.1

' Second Run

w, . Conditions
rhtLIHINARY CALCULATED VALUES

REL nun. [ECIfiAL .0003 .
AIRFLm HATE. LB I-RY AIFT/HR/SG FT 605.7 CFM AT TIN 240.3 Soybean Drying
le‘fl' rmxwraa soar. BTU/EIH/SG FT/F 15.902 simulation
£331. as. we r:acr~7 .04 DRY BASIS. DECIMAL .0004

INLET AC. any 39313 BECIHAL .1425

EEniV VELUQITY. FT/HH 14.16 LB DRY HATTER/HR/SG FT 572.21

 

HEPTH TIHF 01R fihg REL GRAIN NC NC
lLffi’ liLTi iiUTi thd’ U15 U15
FT HF F LB/LB DECIMRL F PLRCENT UECIMAL
000 000 44:09 00063 00004 7700 12047 01425
.10 .01 219.0 .0075 .0098 184.3 12.39 .1415
70 .01 196-2 .0089 .0190 171.9 2.26 .1597
53 .02 152.2 .0105 .0212 '90.5 12.13 .1330
.1. .03 189.6 .0121 .0294 188.2 12.00 .1364
.36 .04 135 6 .0141 .0365 105.3 11.83 .1342
.52 .04 183.3 .0149 .0398 194.1 11.76 .1333
.72 .05 133.5 .0161 .0446 182.3 11.66 .1320
.32 .06 191.7 .0173 .0495 190.7 11.57 .1308
.96 .07 177.1 .0191 .0578 178.1 11.42 .1290
1.63 .07 173.1 .0197 .0611 177.1 11.37 .1293
1.11 .08 1X7.1 .0201 .0544 176.2 11.31 .1276
inL‘: 00“.) 117.102., .0716 00/1. 174.4 .102 0120.3
1.31 .09 171.4 .0222 .0743 173.5 11.16 .1257
1.17 .10 1/2.3 .0235 .0826 171.5 11.05 .1242
1.64 .11 1 1.5 .Oflsl .0859 170.7 11.01 .1237
1.60 .11 110.7 .0246 .0892 170.0 10.96 .1231
1.73 .12 169.2 .0255 .0958 168.5 10.89 .1221
1.H0 .13 163.3 .0260 .0991 167.8 10.84 .1216
1.93 .11 167.2 .026 .1056 166.5 10.77 .1207
2.66 .15 163.9 .0277 .1120 165.3 10.70 .1198
2.13 .13 165.3 .0231 .1152 164.7 10.66 .1194
2.26 .16 164.1 .020‘ .1216 161.5 13.60 .1185
2.32 .16 165.3 .3293 .124d 163.0 10.57 .1181
2.46 .17 162. .0300 .1310 161.9 10.50 .1174
2.55 .18 161.6 .0305 .1357 161.1 10.46 .1168
2.62 .19 161.1 .0309 .1388 160.6 10.43 .1165
2.73 .19 160.1 .0315 .1449 159.7 10.38 .1158
2.8? .2 159.7 .0318 .1479 159.2 10.35 .1155
2.95 .21 153.3 .0324 .1539 158.3 10.30 .1148
3.01 .21 1b3. .0327 .1569 157.9 10.28 .1145
STATIC PFESSURF. INCHES 0F H20 9.08
HORSEPSHER/SG FT .20

 

125

ENERGY INPUTS: BTU/BU

FAN (.b EFF) 90.
HEAT AIR 4900.

MOUE GRAIN

0.
TOTAL 4990.

UATER REHOUEflv LF/PU 1.40

BTU/LB H20 3552.21

QUALITY CHANGE, PERCENT 11.

QUALITY CHANGE: PERCENT 11.

18

18

126

ESTIMATE OF THE MOISTURE REMOVAL TO COOL TO AMBIENT
HOISTUFE REHOUEDI POINTS UET BASIS

FINAL MOISTURE CONTENT:

UET BASIS

TOTAL

BTU/LB H20
END CONCUR

3552.21

1.004 CP SECONDS EXECUTION TIME

EEnDY 16.33.51
22::‘36.
F/FC EEGUN.16.34.06.

LSING THE EAHPHH

IHEJT»COEN;TIOW*3
NiHPrR I)" T-TIICFS TO BE
AfiHIEUT TEN?) F69.
Ii1-LT E‘UIST’NQE C(HTHEHTI

STAGE 1 INPUT CONDITIONS:
INEET AIR TEMP. F350.
INLET APS HUM RATI0.003

SIMULATED 2

2.13

8.49

THIHLAYER EQUATION FOR BEQNS

UET BASIS PERCENT13.6

AIRFLOU RATE; CFM/SQ FT(AT AMBIENT CONDITIONS) 128.
GFfiIN FLOU FATE. BU/HR/SO FT 10.32

LIVER LENGTH, FT 3.
OUTPUT INTERVAL: FT.1
TEHF';F.'ING LENGTH, FT '3.

PRELIMINAWT CALCULATED VALUES

FEL HUM! PECIHAL .0005 -
fiIFTLCU PATE- LB FRY AIR/HF/SO F 537.1 CFM AT
“FLT FFALSFEH CJlEr IfllLfifli/SQ FT/F 15.167

LCUIL ”C. MB FEHC.MT .03 LHY BASIS: UECIMAL

INLET MC. DRY BASIS DECIMHL
UFHIN VELOCITY, FT/HR 12.84

.1574

LE flRY HATTER/HH/SU

DEPTH TIME AIR ABS REL
TEMP HUM HUM

FT HR F LB/LB DECIMAL
.00 .00 347.6 .0030 .0005
.10 .01 173.7 .0038 .0132
.20 .02 159.6 .0049 .0243
.34 .03 135. .0064 .0347
.41 .03 134.1 .0071’ .0393

L'- I‘A dl'f" l 13".“ flafll

TIN 196.4
.0003

MC

08
PERCENT
13.60
13.54
13.45
13.32
13.27

1" 1’

MC
DB

DECINAL

.1574
.1566
0 . 524
.1537
.1530

{E‘I

First Run
Conditions

Soybean Drying
Simulation

 

 

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.32 .02 180.3 .00/0 .0211

.11 .01 1752.4 .0077? .0757

.01 .01 175. I .00‘1‘3 .0303

.51 .03 1‘T3.1 .(1104 .031K‘

./1 .06 173.6 .0114 .0397

.31 .05 17?.1 .0124 .0444

0""; .03 1‘270: 001.59 0052‘]?
1.04 .03 107.0 .0145 .0536
1.1 .09 163.2 .0150 .0583
1.2 .10 Iéd.£ .0161 .0651
I.-6 .11 137.1 .0171 .0715
I.-.:'- .11 1.73.4 . 1-76 .0747
1.3? .12 163.7 .0137 .0396
1 .65 .13 1"/‘.-’) .0171 .03‘3/
1.72 .13 161.4 .3195 .0539
1.35 .14 1;}.2 .0703 .0951
1.92 .13 E 7.6 .0207 .0982
2.C5 .16 i;3.3 .0315 .1044
2.12 .16 177.9 .0318 .1075
2.25 .13 13.5.9 .'.":7".7'.5 .1131:
2. 51 .18 1176.4 .0333 .1156
2.33 .1'7 15.3.4 .0.’ 55 .1221.
2 31 .70 1;§.7 .OTJV .12/0
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2.71 .21 If{.4 .0?43 .1338
3.31 .52 ‘57.0 .0231 .1333
3.71 .23 113.2 .0336 .1443
3.02 .23 131.3 .0259 .1472

S'fi-"I': F'F'ET‘V'JJ'Z'Fy 137313723 {11: HBO 7.47
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11.37
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11.04
11.00
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10.63
10.36
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F1" '._:."-1f'."- ' '.:'.‘ {J’li :‘I'K-Z' VALUES

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11

Second Run
Conditions

Corn Drying
Simulation

CFM AT TIN 240

 

AJ

CO.-- '1“. -‘M

130

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C..;3 REL? 6 win Lfifih SIfiULATION
L. IN," EhE Ti13i’.r-(..vl li11-.i-.5..’:.h' ELika-iTIUN i'bR CURN
INPUT CTJPITfflti:
I“? :: f-IF.’ TEN-'9 74'3").
I{L-T 333 HUN RQYIU.OO3
AIFFLJU Fa“?! LEM/50 FT(AT AMBIENT CONDITIONS) 128.
AMAIIWT TEuP. Fofl.
INLI'f EifiI;3 TE”VW 1:70.
IN_£ HGISTbHE CSNFEhI. MET BASIS PERCENT13.6
C'fili FWJTJECLTEr BU/HH/fiillrr 10.32
URIER LEFSTH. rr 3.
OUTPUT INthVfiLv FT.1
FFELIHINARY CALCULPTED VALUES

”fi- :4...'P.'.b-u :-~‘—“P now-’9‘ H‘CIWOI—‘(D'v“’-—..$ .-‘ :0...” 1' J‘-. M

.JJ/7
.1354
o 1 Tit—Id
o 134:”)

.1333

First Run -
First Pass
Conditions

Corn Drying
Simulation

 

l3].

RFl HUM. DFVYHWL .0305 ATFFLfiu RRTF. 1F DRY AIRIHR/SN FT 559.1 CFM AT TIN 176

I” .r fr-./...':..'»L'=: 1..-: . L«;._./u.</:.u . .r'xr' 12.).167
L."L H_. q. '.wrr'r .33 try Banls. L5¢1HAL .0018
'- "r W‘. 2w 1 fnj"'" --

91.13 UELCCI'Yo ‘I/HR 12.04 bk RY fl011ER/HR/UJ FT 496.96

DEPTH TIME AI" fiFS RtL CRhIN NC NC
'TCMF' rHlM PHH1 'TEMF' NB Uh
FT 1”? F LII/Li" DEPTHLL F F'ERL‘EN' {IL’CII‘ML
.00 .CO 347.0 .0030 .0003 70.6 13.60 .lCz4
.10 .Ll 100.2 .0030 .0120 176.6 13.52 .lfléJ
.20 .02 176./ .QCuO .01é3 176.0 13.43 .1502
.31 .02 174.? .0050 .0303 174.3 13.34 .1540
.41 '03 173.3 .0070 .0746 172.7 13.96 .1329
.72 .03 i71.5 .0980 .0393 170.9 15.18 .1318
..3 .05 110.0 .0039 .0355 169.5 13.10 .1508
.7? ."'.‘3 1-...-.6 .00‘.’:" .0571} 1.14.1 1.5.04 .11‘1‘9’
.93 .Co is .3 .0103 .0420 65.8 12.97 .1490
.93 .07 1:3.5 .0113 .0471 165.3 12.90 .14H0
1.11 .03 154.3 .0130 .0314 lé”.1 19.03 .147:
1.23 .C? 1.3.5 .0127 .4253 1d2.? 12.78 .IQQS
1.1.3 .10 Zulffl? .0134 .0! 0:? 131.3 lib/2 {14:41.5
I-J: .10 1oi.1 .0143 .0346 lfi0o7 12.€7 .ITUL
L. .2: .11 1"-0.1. .0146 .05.}? 11.9.7 12.6.2 .1414
1.:2 .1? J"9.1 .0131 .0733 139.} 12.57 .1439
l . .2 . ”3 13.1. .0157 .07/6 Ira-”.7 12’. 5;? . .1 4.3.1
1./3 ..3 157.3 .0‘61 .0013 15/.0 13.4H .14]?
1.7:? .1‘. 135.? .0163”) .0369 1113.13 12.4.3 .1419
1.73 .I: 117.5 .0172 .0911 "1111.0 12.3? .1~1.4
3.1“; . ‘4 "1.4.7 .0177 .(‘J‘rLfi-‘J 154.2 123.31:- .19.“;
3. 15 .1 ‘ 'r-3.}' .017 l .3{”/5 15.1.4? 113.u1 .1 d'w
2.35 .17 1JJ.T .ULJfl .1035 13C.7 12.37 .ISVf
2‘. '52 .1'3‘ .T.—.‘._$ .319" .10.”. Vii-ff." 1.7.234 .1101}
2.": ot'l 1 10.1. n.11"‘. 911.10 1111.3 1?..1 0.1.1.1."?!
3.5:! .."1 l'.0.')‘ .-'.-“/7 .1]..'. 130.6 1.2.17 .151nb
LUH’ .71 1‘5‘.7 .')..!5 “12.6 149.5 12.12 .1..‘./‘.‘"
?.77 .2J 11V.J .0206 .1251 159.1 1”.10 .1370
2.51 Q'; 1:9. I .7L03 .1370 148.7 '2.08 .13/4
2.75 ._J 1124.4 .3211 .131d 148.2 12.05 .1371
7:.”3 .-"r 1"/'...1 .DLJ4 .1350 147.6 12.03 .1367
3,571: HECZEprv :HCX;C C. th 12.30
-1,“ 7~in.n0 r7 .AJ
u191.’ INPUTS. BfU/EU

FQW ' 5 L??) 122.

Hin! (13 3/19.

11.: 1:{r‘l-'1 ’1.

391.3 . .53
"’41‘ 1.04.2in
C

P :ECUHfls LXECUIION TlflE

 

 

REFERENCES

 

Alden, D. E. Soy Processing: From Beans to Ingredients.
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Anderson, R. J. Commercial Concurrent Flow Heating-- ,
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Bunn, J. W. Moisture Extraction Concepts, Design and
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Carrano, J. A. High Temperature Continuous Flow Grain
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Overhults, D. G., et al. Effects of Heated Air Drying on
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"7'11 1117 "11171114711111 1'“