Download Grinding and PARTICLE SIZE REDUCTION

GRINDING
and
PARTICLE SIZE
REDUCTION
Keith Behnke
Dept. of Grain Science and Industry
Kansas State University
Manhattan, Ks
WHY DO WE GRIND?
IMPROVED ANIMAL
PERFORMANCE
INCREASED MIX UNIFORMITY
IMPROVED PELLETING
MEASURING PARTICLE
SIZE
PARTICLE SIZE TEST
(ASAE STANDARD - S319)
This method involves using a sieve stack
to determine the geometric mean particle
size (dgw) and the geometric standard
deviation (sgw).
Results can be obtained either
graphically or through calculations.
ESTIMATING
PARTICLE
SIZE
A Quick Method for Estimating
PARTICLE SIZE
Minus 14 Mesh
(%)
90-95%
80-90%
70-80%
65-75%
60-70%
50-60%
Particle Size
(Microns)
500
600
700
800
900
1000
Source: Champion-Roskamp, Waterloo, IA.
METHODS OF GRINDING
Impact
Compression
Shear
Attrition
HAMMERMILLS
ADVANTAGES
Ability to grind a wide variety of
materials
Ease of maintenance, less maintenance
cost
Versatility
Less complicated to operate
Less initial cost
DISADVANTAGES
Energy consumption
Produces a greater Sgw
Noise and dust pollution
Heat generation and moisture loss
ROLLER MILLS
ADVANTAGES- Rollermills
Electrical efficiency
Particle size uniformity
Less maintenance
Less dust pollution
DISADVANTAGES
Rollermills
Higher initial cost
When maintenance is needed it is
expensive
Can not effectively grind fibrous
materials
Reduced throughput at small particle
sizes
ENERGY COST
COMPARISON
Roller Mills vs Hammermills
Grinder
Type
Particle
Size
Energy
Cost
(microns)
($/ton)
Hammermill
399
1.56
Roller Mill
432
1.31
Hammermill
718
.65
Roller Mill
709
.47
Hammermill
2,040
.35
Roller Mill
1,813
.05
Savings
(%)
16
28
86
PRE-GRINDING Vs.
POST-GRINDING SYSTEMS
PRE-GRINDING SYSTEM
Advantages
Longer grinding time a t full motor load
Gives a buffer for down time or maintenance
on the grinder
Disadvantage
Requires more storage bins for both ground
and raw ingredients
POST GRIND SYSTEM
Advantages
Accommodates material changes
Does not require as many storage bins
Disadvantages
Less energy efficient
Directly affects the capacity of the facility
INNOVATIONS
IN
GRINDING
THE FUTURE!
GRINDING OPERATIONS
* Hammer Design and Metallurgy
* Air Assist System Design
* Noise Control
* Automation and Routing
* Quick-Change Screens
* Quick-Change Hammer Gangs
THE FUTURE!
GRINDING OPERATIONS
* Vertical Shaft Hammermills??
-European Designs now available
-Air-Assist not recommended
THE FUTURE!
GRINDING OPERATIONS
* AUTOMATION???
-The One System That Clearly Should
Be Automated!!
-Start-up/Shut-Down, Routing
and Ingredient Changes
-Lights Out Operations??