Hot Mix Asphalt Production

1. Hot Mix Asphalt Production Chris Lange PMP, Pr.Tech.(Eng) Director (Technical) Much Asphalt (Pty) Ltd Road Pavement Forum: 10th April 2006

2. Hot Mix Asphalt Production • Plant types and basic components • Plant calibration • Dust extraction • Filler handling and control • Aggregate heating • Procurement / handling of raw materials • Finished product storage • Delivery

3. Scalping screen to remove oversize aggregate Cold Feed Bins Drum Mix Plant - Conventional Hot Storage Bins Exhaust Fan Filter Baghouse Primary dust collector HMA made continuously and sent to storage silos Bitumen Tanks Drying and mixing drum Belt scale

4. TWIN DRUM PLANT : COUNTER-FLOW

5. Old Drum Mix Mix Plant:

6. Plant filler storage and feed Twin Drum Plant RAP Feed Filter Baghouse Coating & mixing drum Aggregate feed Finished product storage Drying & heating Drum

7. Parallel-Flow Drum-mixer Zones Combustion Air Heating Drying Mixing BIT. Hot Mix Asphalt

8. Mixing Combustion Heating Drying Air Hot Mix Asphalt Bitumen Counter-Flow Drum-mixer Zones Aggregate

9. Counter-Flow Batch Plant Dryer Zones Combustion Heating Drying Air Aggregate Hot Aggregate

10. Batch/Mixing tower Primary collector Filter Baghouse Hot Storage silos Batch Plant Elements Bitumen storage tanks RAP Feed Dryer Drum Cold feed bins

11. Aggregate to screens Aggregate weigh hopper Bitumen weigh pot Pugmill Hot mix asphalt dispensed into truck / hot-bin Aggregate from dryer Screens size aggregate Hot aggregate travels up bucket elevator

12. Aggregate and bitumen weigh hoppers Bitumen Weigh-hopper

13. Aggregate Hot Bins

14. Warren Brothers Patent Application Drawing: Original Batch Plant

15. Belt Scale Calibration Cold feed system Belt scale Reference scale

16. Cold Feed Bins and RAP Bin

17. “Graphing the Feeders”

18. Tachometer Mounted on Tail Pulley of Cold Feed Bin Belt

19. “No Flow” Paddle at Feeder Discharge

22. Induced Air Burner

23. Fuel Reticulation and Heating System HFO Tank In-line heater HFO Sampling pt

24. Temperature Profile of Counter-Flow Dryer Heating Combustion Drying 800º C 760º C 120º C 400º C Gases Aggregates Aggregate 0º C 150º C 150º C 300º F 100º C 20º C

25. Drum Flights / Lifters

26. Primary and Secondary Emission Control Primary Dust Collector Filtered Air Secondary Dust Collector Fines collected and returned Drying Drum Exhaust Fan

27. Primary Collector:Cyclone

28. Multi-Tube Collector Outlet tube Gas inlet Spin vanes Inlet tube Collector element Valve

29. Discharge Housing Functions as a Knockout Box Air Gas flow Optional knock down plate Bitumen Fines mix with hot mix asphalt

30. Cutaway Section of a Typical Baghouse

31. Pulse Jet Baghouse Exhaust fan Exhaust fan Manifold Manifold Dust screw Dust screw

32. Automatic Damper Controls

33. Hot Elevator Cyclone feeding fines directly back Batch tower Cyclone, Screw Collector, and Hot Elevator

34. Filler Weigh-Pod After Surge Silo

35. Emission Control Summary • Remove particulate matter • Primary • Secondary • Return fines to the mix • Affects void content • Affects mix stiffness • Difficult to control

36. Batch plant filtration

37. Aggregate storage

38. Aggregate Storage

39. Bitumen Storage BITUMEN TANKS – ELECTRICALLY HEATED/ 24 HR TEMPERATURE MONITOR AND CONTROL

40. Old Style Operating Cabin

41. Plant automation: Modern control cabin:

42. Plant automation

43. Roodepoort Op Screen Plant Automation – Operating System Graphics

44. Batch Plant Schematic

45. Batch Plant Op Screen

46. Laboratory from the past

47. Modern Asphalt Laboratory

48. Quality Control Trends Monitored Binder Content Voids in Mix Filler Content

50. Slat Conveyor Feeding Storage Silos