This document discusses feed manufacturing processes, with a focus on grinding methods. It describes the functions of hammer mills and roller mills. Hammer mills are the most common grinding device and use hammers on a rotor to reduce particle size through impact. Roller mills use compression and shearing forces between counter-rotating rolls. The document provides details on the components, operation, advantages, and disadvantages of each type of grinder to optimize particle size for animal feed applications.
5. Why Do We GrindWhy Do We Grind
Expose greater surface area for digestion.
Improve mixing characteristics of ingredients.
Improve the potential for further processing.
Satisfying customer preferences
6. GRINDING
DEFINITION:
The particle size reduction
which increases both
The number of particles
The amount of surface area
per unit of volume
Also modify the physical
characteristics of ingredients
Access to nutritional comp. as
starch & Protein
Grain Interior is exposed to
digestive enzymes
Enhanced breakdown improves
absorption in the digestive tract.
ANIMAL PERFORMANCE
Mixing
Conditioning
Pellet Quality
Pelleting efficiency
Feed handling & transport.
7. GRINDING
MATERIALS
Majority of materials either
Within the feed plant or
Prior to receiving.
Most Common are
Grains
Corn
Sorghum
Wheat
Meals
Canola meal
Soybean meal
8. GRINDING
PARTICLE SIZE
In past, Terms used were
Fine
Medium
Coarse
Thus
Standard procedure
1) Series of sieves are used
2) Grain Amount Retained on
Each sieve analyzed
3) Mathematical calculation /
Formula is applied
Particle size uniformity in
a particular sample
These are relative terms
Little use in evaluating
research on the particle size
GMD
(Geometric Mean Diameter)
Measured in Microns “μ”
GSD
(Geometric Standard Deviation)
GSD uniformity
GSD uniformity
9. PARTICLE SIZE
Particle size of ground material by hammer mill
Using different screens
S. #
Screen Size GMD
Category
Inches mm μ (range)
1 1/8 3.18 540—630 Finer
2 3/16 4.76 680—720 Fine
3 1/4 6.35 720—880 Medium
4 ? 7.94 About 970 Coarse
5 ? 9.59 About 1200 Coarser
10. PARTICLE SIZE
EFFECT ON PELLET DURABILITY
The accepted principles
1. A finer grind results in a more durable pellet.
2. Fine or medium ground materials
Surface area for moisture absorption from steam
better lubrication and increased production rates.
3. Very coarse grinds or large particle size
provide natural breaking points in pellets
Creating more fines, lowering pellet quality.
11. PARTICLE SIZE
EFFECT ON NUTRIENT COMPOSITION
CORN Different fractions based on Particle Size
have little or no effect on nutrient composition. [ Nir et al. 1994 ]
CONCLUSIONS
In pelleted or crumbled diets
little effect on live performance,
uniformity of nutrient content of feed
Or the pellet quality produced
If grains are to be incorporated into mash,
Finer particle sizes (less than 600 µ GMD) should be avoided.
Producers should adjust grinding size depending the form of diet to
be fed ( Mash / Pellet) using hammer mill and roller mill grinding.
15. HAMMER MILL OPERATION
GENERAL DESIGN
1) A delivery device
(For material introduction)
2) Rotor Assembly
With series of disks
Mounted on the
horizontal shaft
3) Free-swinging hammers
Suspended from rods
4) Perforated screen
5) Removal of ground product
Either gravity- or Air-assisted
Horizontal
shaft
16. HAMMER MILL OPERATION
Hammers
Rotor Plates
Rod
Rotor Shaft
Rotor
Assembly
Outlet &
Take Away
Air Assist
Motor
Screen
Inlet
HAMMER MILL INTERIOR
18. System Design Factors
Feed material characteristics
Size (decide multistep grinding or single)
Moisture contents (determine dust collector)
Grindability (hardness, density etc..)
Temperature sensitivity
Hammer mill factors
Operating requirements (capacity, horsepower,
hammer-tip speed)
Safety requirements (magnets, exploisable, sensors )
19. Contamination and Cleaning Requirements
Space Requirements
Maintenance Requirements
Related equipments
Feeders
Drives
Sensor Monitoring
System Design Factors
20. HAMMER MILL OPERATION
VARIABLES
a) # Of Hammers on shaft
b) Size of Hammers used
c) Arrangement manipulated
d) The hammer Sharpness
e) Hammer Wear patterns
f) Hammer-tip speed
g) Screen design
h) Screen hole size
i) Whether or not air assist is used.
GRINDING CAPACITY
APPEARANCE OF THE PRODUCT
4.06
2.84
1.63
0.85
0
1
2
3
4
5
Prod.
Rate
T/H
900 700 500 300
Partile size (Mirons)
Particle size &
Rate of Production
21. HAMMER MILL OPERATION
COMPONENTS DESIGN & SPECIFICATION
1. DELIVERY DEVICE / FEEDERS
Screw feeders,
Rotary vane pocket feeders,
Vibratory feeders,
Belt feeders,
Drag feeders,
"Pocket" feeder, Fitted with a Rotor
Considerations For Feeder Selection
Initial cost,
Evenness of feed,
Compatibility with product
Physical size of the feeder,
The estimated maintenance cost
23. COMPONENTS DESIGN & SPEC.
2. HAMMER DESIGN
Optimal hammer design Maximum contact with the feed ingredient.
SIZE:
Rotor speed = 1,800 rpm, 10 In. Long, 2.5 In. Across & 0.25 In Thick
Rotor speed = 3,600 rpm, 6 to 8 In Long, 2 In Across, & 0.25 In Thick
NUMBER:
For 1,800 rpm = 1 for every 2.5 to 3.5 Horsepower
For 3,600 rpm = 1 for every 1 to 2 Horsepower
DISTANCE:
The distance b/w hammer & screen = 0.5 In For cereal grains.
HAMMER TIP SPEED:
Tip speed of the hammers is critical for proper size reduction
Tip speeds commonly Range Between 16,000b & 23,000 F/ M
24. COMPONENTS DESIGN & SPEC.
3. SCREEN DESIGN:
Open area of screen Determines
The particle size &
Grinding efficiency.
DESIGN
Designed to maintain
The Integrity & Greatest amount of open area
Generally
Screen openings (holes) aligned in a 60-dig. Staggered pattern
This method will result in a 40 percent open area
Optimized open area while maintaining screen strength
OPEN SCREEN AREA TO HORSEPOWER.
Recommended ratio for grains = 8 to 9 square Inch per Horsepower.
Not enough open Area / Horsepower generation of heat.
Generated Heat Exceeds 120F to 125F (44C to 46C)
Capacity may be decreased as much as 50 percent.
25. COMPONENTS DESIGN & SPEC.
4. GROUND MATERIAL REMOVAL
A critical design feature
Directly affects the efficiency of operation
Also affects the particle size determination
AIR ASSIST SYSTEM
Most newer hammermills are equipped
Draws air into the hammermill with the product to be ground.
Provide Reduced pressure on exit side of the screen
Disrupt the fluidized bed of material on the face of the screen
Allow particles to exit easily through screen holes.
26. HAMMER MILL OPERATION
ADVANTAGES
Ability to grind wide
variety of materials.
Produce a wide range of
particle sizes
Work with any friable
material and fiber
Less initial purchase cost
compared to roller mills
Minimal maintenance
expense
Uncomplicated Operation
DISADVANTAGES
May generate heat
(source of energy loss)
Create noise pollution
Create dust pollution
Produce greater particle
size variability
(less uniform)
27. ROLLER MILL OPERATION
PRINCIPLE
SIZE REDUCTION Combination of Forces and Design
Features.
Rolls rotate at same speed,
Compression is the primary force used.
Rolls rotate at different speeds,
Shearing + compression are the forces used
Rolls are grooved,
Tearing & Grinding components introduced.
Coarse grooves Less size reduction
Finer grooves More size reduction
28. ROLLER MILL OPERATION
GENERAL DESIGN
1) A Delivery Device
To supply a constant and
uniform amount of the material
2) Pair Of Rolls
Mounted horizontally in rigid
frame
3) One roll Fixed in position
And Other is Moveable
closer to or further from fixed roll
4) Rolls counter rotate either
at same speed or one may
faster
5) Roll surface may be smooth or
have various grooves
6) Pairs of rolls may be placed on
Rotor
1st
Roll Pair
Coarse Grooves
Coarse ground
Material
Inlet Bin
2nd
Roll Pair
Fine Grooves
Fine Ground
Material
29. ROLLER MILL OPERATION
COMPONENTS DESIGN & SPECIFICATION
1. DELIVERY DEVICE / FEEDERS
The simplest feeder
Bin hopper with an agitator located inside
Possess manually set discharge gate.
Best suited for coarse processing.
For grinding operations
Roll feeder is suggested.
Roll is located below the bin hopper and
Possess automatic adjustable discharge gate.
30. COMPONENTS DESIGN & SPEC
2. ROLL SPECIFICATIONS
IN A PAIR
Rolls are 9 to 12 inches in diameter
Ratio of length to diameter can be as great as 4:1.
ALIGNMENT
Sizing dependent gap between the rolls along their length
Non Uniform gap Increased maintenance costs & reduced out put,
Overall increased operation costs.
Gap Adjusted automatically
Through pneumatic or hydraulic cylinders operated by programmable controller
COUNTER ROTATING SPEED
Typical differentials range from 1.2:1 to 2.0:1 (fast to slow)
Typical roll speeds would be 1,300 feet per minute for a 9-inch to
3,140 feet per minute for a 12-inch roll.
ROTATING MOTOR
Single motor is used to power a two roll pair
With either belt or chain reduction supplying the differential.
31. ROLLER MILL OPERATION
ADVANTAGES
Energy efficient
Uniform particle-size
distribution
Little noise
Less dust generation
No Sig. Heat prod.
Decreased fire risk
Excellent physical
appearance
Easy installation
DISADVANTAGES
Little or no effect on
fiber
when required,
maintenance can be
expensive
may have high initial
cost (depends on
system design)
32. For coarse reduction of grain, a roller mill may have a
significant advantage over a hammermill in terms of
throughput/kwh of energy. For cereal grains processed to
typical sizes (600 to 900 microns) for the feed industry, the
advantage is about 30 to 50 percent. This translates into
reduced operating expense.