Aeration system for storage

1. Name: PRACHI PAHARIYA
Id no.: 14AG63R10
Native place: KATNI (M.P.)
Email:prachipaharia28@gmail.com
Education: B.TECH(AGRICULTURAL ENGG.)
University of graduation: CAE, JAWAHARLAL NEHRU
KRISHI VISHWAVIDYALAYA, JABALPUR (M.P.)
Year of passing out: 2014
Job experience (if any): NO
Training/projects undergone: TRAINING-1. ONE MONTH FROM
CENTRAL REGION FARM MACHINERY TRAINING AND TESTING
INSTITUTE , BUDNI(M.P.),
2. ONE MONTH TRAINING IN FOOD PROCESSING FROM CIAE,
BHOPAL (M.P.).

2. 3. FOUR MONTH TRAINING IN REMOTE SENSING FROM IIRS,
DEHRADUN(U.K.)
Project :DESIGN OF RPEC DRYER UNDER GUIDANCE OF PROF. C.M.
ABROAL.
Seminar on: AERATION SYSTEM FOR STORAGE.
This seminar helps us to understand the topic deeply and way of presenting .It
also improves the confidence. The teachers are very helpful and guide the
student on their mistake and want to improve the student. This seminar the
proper knowledge how to present.

3. AERATION SYSTEM FOR STORAGE
PRACHI PAHARIYA
(14AG63R10)
FOOD PROCESS ENGINEERING

4. CONTENT
INTRODUCTION
MOISTURE MIGRATION
PURPOSE OF AERATION SYSTEM
AIR MOVEMENT
WHY AERATE
HOW AERATION WORK
EXPERIMENTAL SETUP
DESIGN CONSIDERATION
BASIC COMPONENTS
AERATION-DRYING OR COOLING
REFERENCES

5. INTRODUCTION
Aeration is the process of moving air
through stored grain at low flow rates
to maintain its quality.
It is a well known and proven
Integrated Pest Management (IPM) tool
for controlling insects and other risks in
stored grains.
Useful storage management tool which
can preserve grain from deterioration,
especially where the moisture content
of the grain is above its safe level.

6. MOISTURE MIGRATION

7. PURPOSE OF AERATION SYSTEM
Aeration of stored grain has four main purposes —
Preventing mould
 Inhibiting insect development
Maintaining seed viability
Reducing grain moisture

9. Air movement within the grain stack
Grain at the top of the stack is the hottest, as heat rises
through the grain. The sun heats the silo roof and internal head
space, resulting in the surface grain at the top of the silo
heating up .
When grain is stored at moisture contents above 12 percent,
the air in the head space heats and cools each day creating
ideal conditions for condensation to form, wetting the grain at
the top of the stack.

10. From the aeration fan outlet, air will take the easiest
route to the top of the grain stack — the path of least
resistance.
Poor aeration ducting can result in pockets of grain
not being aerated.
The peak of grain in a silo is another common place
that aeration bypasses. The path of least resistance is to
the side, below the peak of the stack as it is a shorter
distance from the aeration ducting.

11. WHY AERATE
DRY GRAIN
To remove generated heat and water from grain
It keep the grain in temperature equilibrium with
the outside thereby preventing moisture migration
Important in reducing mold growth and insect
activity.
Fumigant applicant
Removing or reducing odors from grains.

12. WET GRAIN
Removes heat by natural respiration of the grain and
keep the grain near to the outside air temperature
Number of days grain can be held under various
condition without excessive spoilage and deterioration

14. EXPERIMENTAL SETUP
Properties of grain samples
The grains were maintained at a moisture content of 11 -13%.
Impurities were reduced to less than 2%.
The following grain properties were analysed regularly to
monitor the changes happening during storage of grains in
the silos.
1. 100 seeds weight (kg)
2. Moisture content (d.b)
3. Grain density (kg/m3)
4. Bulk density (kg/m3)
5. Bed porosity

15. Other suggested chemical properties
1. Pasting properties (Farinograph and RVA)
2. Cooking properties (Texture, hardness)
3. Lipid content
4. Protein content
5. Phenols
6. Flavour

16. CALCULATING CYCLE TIME:
Where,
AT = aeration time, hours/cycle
AR = airflow rate, cfm/bu
TW = test weight, lb/bu
1 lb/bu=12.87 kg/m3
Controlled aeration at 15oC in early autumn and 7oC in
late autumn for 2-cycle.
 Binning in summer followed by controlled aeration at
24oC (2 cycle autumn cooling cycle)

17. DESIGN CONSIDERATIONS
General design factors
•Location/harvest date
•Grain Type (coarse vs. small)
•Storage structure
•Available energy
•Cooling speed vs. energy cost

18. Other factors to be considered:
• Airflow rate
• Propeller vs. centrifugal fan type
• Airflow direction (suction or pressure)
• Distribution (ducts or perforated floor)
• Control (manual or automatic)

19. Basic components of the aeration system
• Fans
• Ducts
• Floor distribution system
• Roof vents, exhaust fans
• Controls for fan regulation
• Pressure switch on fans for negative
pressure systems

20. Fans
Axial
– Van-axial
– Tube-axial (small - 2Hp or less)
– Low cost, noisy
– 3 – 5 inches static pressure

21. Centrifugal
– 1460 to 3500 rpm
– Higher cost
– Quieter
– More airflow per HP
above 5” static
pressure

22. Available Aerations Systems
1. A single perforated duct.
2.A rectangular perforated area located in the middle of
the floor.
3. A cross duct arrangement.
4. A V shaped duct
5. A fully perforated floor.

25. Vent types
1. Gooseneck vent

26. 2. Mushroom vent

27. 3.Roof exhauster

28. OPIGIMAC Temperature and Insect Monitoring,
Aeration Fan Control System

29. Roof vents controllers
• Normally closed
• Designed to open under pressure of vacuum
• Interlocked electrically with fans
• Reduces insect infiltration
Fan controllers
• Temperature limit thermostats
• Humidity control
• NEMA 4R housing
• Hour meter, selector switch
• Time delay relays (TDR) for multiple fans
• Off-the-shelf components
Relative humidity and temperature controllers

30. Air distribution systems
Provide uniform airflow through
the grain.
Consist of
– Transitions, manifolds, supply
ducts
– Perforated ducts, pads or false
floors
– Roof vents or exhaust fan
systems

31. Transition/supply duct air velocities
• Maximum design air velocity
– positive pressure: 2500 fpm
– negative pressure: 2000 fpm
• Preferred design air velocity
– positive pressure: 1500-2000 fpm
– negative pressure: 1000-1500 fpm

32. Air flow rates
Depends on the fan motor (upper limit of air flow).
Negative Airflow
– Pros…
• Reduced condensation under steel roofs.
• Cooling zone movement estimated by fan exhaust air
temperatures.
• Can hold covers on outdoor grain piles.
– Cons…
• Needs larger transition/duct cross-section areas
(especially in flat storage).
• Roof damage if vents freeze (use neg. pressure switch).
•Top grain heat moves through all grain.

33. Positive Airflow
– Pros…
• Distribution in flat storage is more
uniform
• Add warm grain w/o heating cool grain
• Aeration zone finished when surface
grain cools
• Less plugging of perforated floors or
ducts
– Cons…
• Condensation under steel roofs
• Heat of compression raises air temp.
3-10° F

34. Air flow path ratio
A + B <= 1.5 C
C: duct to grain peak
A + B … longest path
Perforated floors
Cereal Grains:
3/32”diameter perf.
Smaller Seeds:
3/64 to 1/16”

35. Grain aeration systems are generally designed to carry out
either a drying or cooling function — not both.
•Aeration cooling can be achieved with airflow rates of 2–3
litres per second per tonne delivered from fans driven by a
0.37 kilowatt (0.5 horsepower) electric motor.
• Aeration drying can be achieved with fans delivering 15–
25L/s/t, typically powered by 7kW (10hp) electric motors.
• The risk of using high capacity fans for cooling is they
increase grain moisture very quickly if run when ambient
conditions are above 85 per cent relative humidity.

37. Cooling or drying — making a choice
There are some simple rules to follow:
• Grain that is dry enough to meet specifications for sale (12.5 per cent for
wheat or 13.5 per cent for sorghum) can be cooled, without drying, to
slow insect development and maintain quality during storage.
• Grain of moderate moisture (up to 15 per cent for wheat and sorghum)
will require aeration drying to reduce the moisture content to maintain
quality during storage.
• If aeration drying is not available immediately, moderately moist grain
can be cooled for a short period to slow mould and insect development,
then dried when the right equipment is available.
•High-moisture grain (for example, 16 per cent and higher for wheat and
sorghum) will require immediate moisture reduction before cooling for
maintenance.

38. REFERENCES
Reed, C. R. 2006. Aeration. In: Managing Stored Grain to
Preserve Quality and Value. AACC International, St. Paul,
Newyork, Pages 141-180
Navarro, S. and R. Noyes. 2002a. (Eds.) The Mechanics
and Physics of Modern Grain Aeration Management. CRC
Press, Boca Raton, FL 647 pp.
O.H. Friesen, D.N. Huminicki.1986. Grain Aeration and
Unheated Air Drying , Manitoba Agriculture , pages 3-30.
 Chris Warrick, Kondinin Group, July 2011. Aerating
Stored Grain Cooling or Drying For Quality Control. GRDC,
pages 2-20

39. THANK YOU