post pellet liquid application

1. Post Pellet Liquid Application
(PPLA)
Charles Stark, Ph.D.
Jim and Carol Brown Associate
Professor of Grain Science and Industry
Kansas State University

2. Liquid Application - Methods
• Apply at the die
• Spray into a screw conveyor
• Spray into a plenum or weir
• Spray using spinning disks to atomize the
liquid

3. Post Pellet Liquid Application (PPLA)
• Ingredients typically applied by PPLA:
• Liquid Enzymes
• Fat
• Molasses
• Vitamins
• Trace Minerals
• Medicated Feed Additives

4. Liquid Application At The Die
• Spray nozzle or nozzles at the pellet mill discharge
– Volumetric measurement based on turns of the feeder into the
pellet mill
• Advantages
– Liquid sprayed onto a hot pellet
– Inexpensive and can be installed on existing equipment
• Disadvantages
– Little to no retention time
– Fat can be drawn off the surface and end up in the cooler and the
cooler air system
– Fat laden fines are drawn off at the cooler and can affect
formulation of the product
– Fat may trap extra water in the pellet

5. Continuous Process Equipment
• Dry Flow System for Feed
• Volumetric Feeder
• Mass Flow Feeder
• Loss In Weight System
• Liquid Flow System for Fat
• Mechanical Liquid Meter
• Coriolis Meter
• Liquid Application Nozzles or Discs

6. Volumetric Flow System
• Measures the volume of material conveyed
– Known amount of material per rpm or pulse
• Dry material
– Screw conveyor
– Rotary feeder
– Belt conveyor
• Tach generator to measure RPM
• Catch tests to determine weight per rpm or hz value
• Liquid
– Displace a known volume per pulse of device
• Nutating disk liquid meter
• Positive displacement pump
• Piston pump
• Turbine

7. Volumetric System – Flow Diagram
Feed
Liquid

8. Volumetric System Dry
Flow Rotary Feeder
Volumetric System
Dry Flow
Screw Conveyor

9. Volumetric System – Liquid Component
Positive Displacement Pump

10. Mass Flow System
• Measures the weight of material conveyed
• Dry material
– Weigh belt
– Weigh screw
– Impact scale
– CentriFlow
• Liquid
– Coriolis liquid meter

11. Mass Flow System – Flow Diagram
Feed
Liquid

12. Weigh Belt/Drag PPLA
Fat
Load Cell
Fat
Feed
Belt

13. Mass Flow System – Weigh Screw

14. Mass Flow System – Impact Scale

15. Mass Flow System – CentriFlow

16. Mass Flow System – Liquid Component
Coriolis Meter

17. Mass Flow System – Coriolis Meter

18. Loss In Weight System
• Monitors the loss weight of material from a
weigh hopper
• Dry material
– Garner hopper
– Weigh hopper
• Liquid
– Loss in weight liquid scale

19. Loss In Weight System
Feed
Liquid

20. LIQUID APPLICATION EQUIPMENT

21. Liquid Spray Into a Screw Conveyor
• Screw conveyor with spray nozzles
• Coverage can be improved with the addition of a spray
plenum
– Increases the probability of the liquid hitting the dry product in a
uniform fashion
• Disadvantages
– Nozzles apply liquid to a limited number of particles
– Depend on the conveyor to spread the liquid
• Spotty coverage
– May be difficult to find nozzles to handle the full range of flow
– Little mixing action with standard flighting
• Cut & fold or ribbon & paddle flight
– Nozzles

22. Liquid Spray Into a Screw Conveyor

23. Liquid Application
Spray Into a Plenum or Weir
• Plenum is a chute with spray nozzles
• Liquid sprayed as the product tumbles through
the air
– Increases the probability of the liquid hitting the
pellet in a uniform fashion
• Weir
– Product sprayed on one side, flipped over and
sprayed on the other
• Disadvantages
– Nozzles

24. Liquid Application
Spray Into a Plenum or Weir

25. Liquid Application - Spinning Disks
• High speed spinning disks atomize the liquid
• Multiple disks = wider spray band
• Slots in each disk allows liquid to migrate to lower
disks
• Serrated disk teeth provides multiple planes of
liquid discharge = wider band of spray
– Wider spray band = more product surface area
exposed for a greater amount of time

26. Liquid Application - Spinning Disks
• Advantages
– Optimum coverage
– No spray nozzles to clog
• Liquid delivered to the disks via a hollow shaft
– Can apply slurries
– Less head pressure on the liquid pump
• Disadvantages
– Requires further mixing in a drum or mixing conveyor
– Requires more headroom than a standard screw
conveyor
– Higher cost

27. Types of PPLA Equipment
Feed Fat

28. Liquid Application Spinning Disks

29. Addition of Dry Additives
n Dry additives applied after liquids
– Enzymes
– Microbial & vitamin products
n Allow time for the liquid to “settle down” after
applying
– Even amount of liquid on all particles
n Can be applied with any of the liquid application
methods
– Sealed system will prevent fugitive particles
n Dry material can be blended with the liquid being
applied
– Compatibility with the liquid
– Can the applicator handle the slurry?

30. Addition of Dry Additives

31. Control System

32. PPLA Summary
• The objective of PPLA is to apply heat
sensitive enzymes or fat post pelleting to
improve pellet quality
• A volumetric or mass flow systems can be
used to measure liquids or dry feed
• The liquid application system should evenly
coat the pellets

33. Thank You!