Different types of seed dryers and various machines used in the pre-conditioning process of seed cleaning

2. TYPES…..
• Layer-in-bin dryer
• Batch-in-bin dryer
• Batch dryer
• Continuous dryer

3. LAYER-IN-BIN DRYER
• Bin is filled to specific depth – depending on
• Seed moisture
• Drying unit
• Bin size
• Drying air controlled by – humidistat set at 55% - to prevent over drying of lower
layers
• Most efficient – slowest drying method – seed drying is uniform between top and
bottom bins
• After filling initial layer – fills must be separated by 3-4 days

4. • Bin functions as dryer with following
components:
• Fan
• Heater
• Operating and Safety controls
• Transition duct
• Foundation Ring
• False floor
• Seed leveller
• Sweep unloader
• Unload auger
• Layer-in-bin ranges from 21-40 feet
diameter and 5-20 horse power

5. BATCH-IN-BIN DRYER
• Quantity of seed at a given moisture
content can be dried with a given drying
unit
• Differ – Have higher capacity heaters and
fan, grain leveller, sweep unloader and
Unload auger
• Deeper the seed depth – lower the air flow
– slower the drying

6. BATCH DRYER
• Relatively dry air is blown through a layer of seed – after drying, seed lot is removed
and filled with another batch
• Have bins with inner chamber surrounded by 2 parallel perforated steel walls – to
contain designed thickness of seed
• Fan and heater unit – connected to one end or side of plenum – heated air for drying
and natural air for cooling forced through the seed
• Rectangular or cylindrical – volume in Bushels (1 bsh = 8 gallons= 36.36 L)
• Fan power = 3 to 30-40 horse power

7. • No. of batches per day = 8-10 for small dryers and 2-3 for large units

8. CONTINUOUS DRYER
• Move seeds through heating and cooling sections of the column continuously
• Seed flow controlled by – volume metering device at the lower side of seed column
• Heated air blown – upper 2/3 – ¾ of the seed column at 100-150 CFM/bu (Cubic feet
per min.)
• Power – 7.5 – 60 horse power
• One leg and two system are available
• One leg – Seed from dryer accumulated in dry holding bin for manual removal
• Two Leg – Low capacity elevator leg moves dry seeds to storage continuously

10. STIRRING DEVICES
• Keep seeds in a loose fill condition – allow more
air to flow through bottom layers – help to avoid
the problems of over-drying
• Breaks pockets of fire and trash
• Blend the seed by mixing action
• Caution – possible to damage the side walls
• Auger near center when starting - to minimize
concentrated pressure and possible damage to
side walls.

11. HEATED AIR DRYING
• Air flow rates – 15-40 CFM/bu – in drying bins and wagons
• Minimum air flow rate – 8-10 CFM/bu for all seeds
• Heated air drying requires higher rates of air flow for two reasons:
• Water is evaporated faster and more air is needed to carry it away
• Higher the rate of air flow – more uniform drying of upper and lower layers
• Faster drying – recommended temp. at higher rates of air flow
• Drying time halved – doubling the air flow

12. Procedure for Heated Air Drying in Bins
• Charge seeds into the bin at recommended depth – maintain uniform distribution
• Operate dryer at recommended temp. for the seed
• After drying – continue blowing air without heat for the seeds to cool to air temp. or
to 500F (100C).

13. SEED CLEANING…..
• Methods……
• Preparing seeds for basic seed cleaning
• Basic seed cleaning operation
• Upgrading the quality of cleaned seed

14. Pre-conditioning and Pre-cleaning…
• Pre-conditioning:
• prepare seed lots for basic seed cleaning
• Remove particles like pieces of trash, stones etc
• Also remove particles lighter in weight and smaller in size the crop
seed
• No pre-cleaning – hand harvested and winnowed seed lots

15. Pre-conditioning Equipments
• Scalper/ Rough cleaner
• Huller – scarifier
• De-bearder
• Pebble miller
• Maize sheller

16. SCALPER
• Scalping: Process in which particles larger than seed size are screened out and seeds
separated in a vessel
• Simple device – for removing large trash
• Consists of – vibrating or rotating screen or sieve
• Screen perforations allow rough seed to pass through – larger inert materials scalped off and
removed
• Single sieve pre-cleaner – Scalper
• Multiple sieve units – Rough cleaner

17. • Rough Cleaner : multiple sieves
• Separation of light chaff and dust – with controlled air
• Separation of large trash – over large hole screen
• Separation of small foreign material – through small hole screen

18. HULLER-SCARIFIER
• Hulling – Removal of outer coat or husk
• Scarification – Scratching of seed coat
• Seeds fall on to a rotating distributing disc –
thrown against hulling and scarifying
surface – centrifugal force
• After seeds are moved – suction chamber –
suction removes fine dust
• Seed discharged to the bottom of the
chamber

19. DE-BEARDER
• Have horizontal beater with arms rotating inside a steel drum – move the seeds through
the drum
• Machine rubs the seeds against arms and against each other
• Degree of action – processing time; beater clearance and beater speed

20. PEBBLE MILL
• Used to remove cob-webby hairs – blue grass
• Has drum rotating about a shaft – at opposite ends
• Mill loaded – seeds and smooth 0.5 inch pebbles – turns at slow speed – rubbing
action roll off the fuzz into small round balls
• Seeds & matted fuzz run over a scalper to remove the pebbles

21. MAIZE SHELLER
• Varies from small hand powered sheller – large
moor driven shellers
• Small hand powered sheller consists – a crank;
small feed inlet; heavy cast iron fly wheel
• It removes the maize seed from ear – seeds drop
into bottom & cobs discharged out from rear
• useful for small lots

22. • Power shellers – installed in processing plants
• Consists of 4 parts
• Inlet hopper
• Rotating beating cylinder
• Concave : perforated steel sheet – to allow seeds to pass through but retain cob toward
vibrating screen
• Fan
• Indigenous power sheller require 7.5 hp motor
• Shelled seed from lower concave – passed through air blast – to remove small cob
pieces and dust