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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??