Clinker cooler 20 golden thumb rules.pptx

Clinker cooler 20 golden thumb rules for optimizations clinker cooling efficiency

1. Clinker Cooler: Golden Rules Hartmut Meyer, CMS - TPT La Union; November 17th, 2010

2. Tasks (targets) of the Clinker Cooler 1) Heat recuperation from hot clinker to minimize the required fuel input (combustion) for the kiln system 2) Cooling of clinker Target 100 – 150 °C clinker outlet temperature for easy clinker conveying, clinker storage and cement grinding  Air cooling of the clinker

3. Grate Cooler Process Terminology Cooling Air Primary Air Fuel False Air Hot Clinker Tertiary Air Secondary Air Exhaust Air Cooled Clinker False Air Recuperation Zone Cooling Zone

4. Grate Cooler Equipment Terminology Tertiary Air Duct Kiln Hood Tertiary Air Damper Cooler Lower Section (Undergrate Compartments) Exhaust Air System Clinker Crusher Static Inlet Bull Nose Cooling Air Fans Cooler Upper Section Grate Drive

5. Grate Assembly moving static Support Roller Guide Roller Movable Grate Plate Support Fixed Grate Plate Support Side Plate Drive Shaft Hydraulic Cylinder Movable Frame Wedge Grate Plate

6. Principle of Grate Movement Parallel movement of all movable supports (wedges) and the movable grate plates is required

7. The Clinker Cooler House Clinker cooler performance is Teamwork!

8. Typical Weaknesses of Older Coolers No static cooler inlet section Outdated grate plate technology (e.g. Folax or Volga plates) Misalignment of grate Internal drag chain Beam aeration Large compartments High grate area load [t/d/m2] Low grate width load [t/d/m] Low specific cooling air [Nm3/kgcli] Grate geometry (steps, inclination) No reliable process indicators Manual control without interlocks Mechanical grate drive Hammer crusher

9. The 3 Basic (Golden) Rules for Clinker Cooler 1 st rule: Keep the clinker on the grates = minimize clinker fall through  improve gap management Cooler grate plates are designed to carry the hot clinker bed and are made of heat-resistant steel. The rest of the cooler is not designed for such high temperatures; particularly the supporting structure beneath the grate must not be exposed to more than 200°C. Hot clinker must be prevented from spilling through the grate by keeping all functional gaps tight (gap management).

10. Video Clinker Fall Through

11. The 3 Basic (Golden) Rules for Clinker Cooler 2 nd rule: Controlled air distribution into the clinker  minimize air losses  compartment sealing required !!! Cooling air must follow the intended channels and cool the intended areas. This cannot be achieved if the cooler leaks air through worn plates, gaps, poor compartment seals, or leaking hopper discharge valves. Also, intake of false air through the kiln outlet seal, clinker crusher, or cooler exhaust-air system must be minimized.

12. Unsealed compartments

13. The 3 Basic (Golden) Rules for Clinker Cooler 3 rd rule: Operate with high clinker bed  low grate speed  increased heat recuperation A high clinker bed increases the residence time of the air in the clinker, essential for good heat exchange. The cooler should always be operated at the lowest possible grate speed.

14. Cooling Time - Retention Time

15. The 3 Basic (Golden) Rules for Clinker Cooler 1 st rule: Keep the clinker on the grates = minimize clinker fall through  improve gap management Cooler grate plates are designed to carry the hot clinker bed and are made of heat-resistant steel. The rest of the cooler is not designed for such high temperatures; particularly the supporting structure beneath the grate must not be exposed to more than 200°C. Hot clinker must be prevented from spilling through the grate by keeping all functional gaps tight (gap management). B1

16. Keeping the Clinker on the Grate is the Key Avoid clinker fall through  Gap management required Only the grate plates are made of heat resistant material The steel structure below is normal mild steel (max. 200°C)

17. Gap Management Gaps on the grate arrangement: Holes (openings) of the grate plate Gap between in grate plates Gap between grate plates and side plates Gap between rows (transverse gap)

18. Grate plates with holes Grate plates without holes have to be installed in the 2 or 3 rows in front of the clinker crusher to minimize air losses via the thinner clinker layer Grate plates with slots Grate plates with pockets Overview Grate Plates: Air openings

19. Grate Plates: Gap between the plates Grate arrangement with gaps between the plates Grate arrangement without gaps between the plates Good example Grate plates are bolted together Bad example  Spacer required Grate plates with overlapping

20. Template to check Dimensions on Grate Plates

21. Gap Management Gaps on the grate arrangement: Holes (openings) of the grate plate Gap between in grate plates Gap between grate plates and side plates (side gap) Gap between rows (transverse gap)

22. Keeping clinker above the grate is the key Clinker fall through due to increased side gap

23. Red river formation / excessive wear on side

24. Red river formation / excessive wear on side

25. Overview Side Plate Design Side plates fixed on side walls Side plates fixed on grate supports Side plates with overlapping Side plates without overlapping

26. Hardfacing to Maintain the Side Gap Hardfacing with electrode Ledurit 65

27. Gap Management Gaps on the grate arrangement: Holes (openings) of the grate plate Gap between in grate plates Gap between grate plates and side plates (side gap) Gap between rows (transverse gap)

28. Principle of Grate Movement Parallel movement of all movable supports (wedges) and the movable grate plates is required

29. Misaligned Grate Movement

30. Wear on Support Rollers and Wedges Worn Support Rollers / Bearing Damage Worn Support Rails Damage on Partition Wall Wear on Surface due to Contact Abrasion due to excessive aeration Air Leakage in Partition Wall Original Position of Grate Plate

31. Wear on the Wedges Increase width of the wedge and the roller if this wear pattern appears often New design

32. Targets for gaps on the grate arrangement Gap between the grate plates: max. 2 mm Gap between fixed and movable row: 1 mm Gap between movable and fixed row: 3 mm Side gap: 5 to 7 mm if side plates are fixed on side walls 2 mm on movable rows if side plates are fixed on the fixed grate plate supports (0 mm in the area of the fixed grate plates supports) Grate guidance: 0.25 mm on each side of the guide roller (Max 1 mm in total) Measure: If required minimize gaps with spacers or weld-on front pieces

33. Rules for the grate re-alignment Replace deformed and worn out equipment. Steel frames deformed > 5 mm Support rollers and wedges worn out > 3 mm Grate plates with a remaining thickness < 8 mm Washed out side plates Establish quality standards and quality control for key parts (grate plates, grate plate supports, side plates, support rollers and wedges) Use centre position (centre of stroke length) of the grate as reference for the grate alignment Minimize shimming. If shimming is required fix the shims by welding Avoid shearing forces for screw connections Assure plate fixation by tack welding If required minimize gaps with spacers or weld-on front pieces

34. Final Messages Gap Management Detect and eliminate design weaknesses Establish quality standards for grate equipment Preventive maintenance is essential A general grate alignment is required every 3 to 5 years minimum Target: No unexpected stops due to cooler failures

35. Questions

36. The 3 Basic (Golden) Rules for Clinker Cooler 2 nd rule: Controlled air distribution into the clinker  minimize air losses  compartment sealing required !!! Cooling air must follow the intended channels and cool the intended areas. This cannot be achieved if the cooler leaks air through worn plates, gaps, poor compartment seals, or leaking hopper discharge valves. Also, intake of false air through the kiln outlet seal, clinker crusher, or cooler exhaust-air system must be minimized. B2

37. Static Cooler Inlet Section: Requirements Rapid clinker cooling to avoid clinker agglomeration (clinker liquid phase) Clinker distribution from the drop point to the entire grate width (horse shoe) Reduced thermal load of the grate equipment (operational safety) 100% sealed (no air losses)

38. Criteria for Static inlet Adequate number of air cannons required. (vessel size min. 100 liter; nozzles required) Installed specific aeration min. 1.8 m 3 /m 2 /s. Static pressure of the fans min. of 100 mbar under grate pressure. Downwards slopped grate plate (5° to 8°) to create downhill force for big lumps Static (dead) clinker layer on the grate plates before start-up Burn tip position: 500 to 1000 inside cold kiln Clinker drop height: > 4 meter Sufficient air required already during start-up

39. Layout Details

40. Horse Shoe Layout (Concept A with inclined walls) 1.0 0.5 to 0.6 15° to 20°

41. Horse Shoe Design and Air Blaster Location Inclined curbs of the horse shoe decrease snow man formation Install more nozzles in the refractory for easy air blaster connection if required min. 600

42. Measures to Minimize Snow Man Formation Design of static cooler inlet (horse shoe) Air Blaster location Air blaster operation (sequence) Specific aeration of the cooler inlet Manual measures to get rid of snow man

43. Specific Aeration of the Static Cooler Inlet without aeration average aeration increased aeration !!! Increase aeration if the clinker tends to stick together on the static inlet !!! In some cases even 2 Nm/s is required The specific aeration of the cooler inlet is the key to minimize the formation of snowman and clinker agglomerates

44. Manual Measures to Destroy a Snowman High/low operation: Pile up clinker behind the snow man by decreasing grate speed and flow on the static inlet Shoot the air cannons manually Increase grate speed and flow that the snow man can flow down the static inlet Repeat this procedure (high/low operation) after 15 minutes if required In hard cases the use of poles, lances or cardox might be required

45. Sufficient air required already during start-up

46. Air Distribution: Clinker Temperature Profiles Hot clinker at the cooler inlet and at the border sides = high pressure resistance. Cold clinker at the cooler outlet and in the centre of the grate = low pressure resistance. The cooling air escapes in aeras of low pressure resistance.  Small aeration field in the recuperation zone and a good chamber sealing is required !!! Target: Minimize cooling air losses to cold clinker areas B3

47. Air Distribution Template

48. Aeration Scheme / Air distribution

49. Clinker Cooling Curve and Air Distribution Clinker cooling curve Air distribution Specific aeration [Nm/s] Clinker temperature difference < 200°C per chamber !!!

50. Clinker Cooling Curve Calculation Clinker temperature difference < 200°C per chamber !!!

51. Cooling air fans Undergrate pressure Fan curve Fan calibration Fan assessment B4

52. Pressure Drop of the Aeration System p Grate System p Clinker p Clinker is related to Clinker temperature Clinker bed height Clinker granulometry Void volume (density) p Grate System is related to Ducting Aeration system Grate plate system Gap management Protection layer, if existing

53. Clinker Pressure Drop = f (Clinker Temperature) hot clinker cold clinker !!!  Good chamber sealing required !!!

54. Fan Curve, Pressure Resistance Curve

55. Recommended Fan Speed

56. Fan Calibration Situation: CCR flow indications are not reliable Recommended measures: Fan calibration by automation and process team

57. Fans: Air Flow Calibration

58. Fan Assessment:Example Situation: Some fans have pressure limitation and therefore operation with high clinker bed is not possible Recommended measures: Complete fan assessment (SCCC); review (HGRS) Replacement or upgrade of under-performing fans Example K6 Fan K21 No fan curves available for K5 !!!

59. What is the Partition Wall? A barrier between the different chambers, to avoid air escape from a chamber with higher pressure to the next chamber with lower pressure Compartment Sealing B5

60. Leakage in Partition Wall

61. Leakage in Partition Wall

62. Air Losses via Partition Walls Without barriers the air escapes to the cooler end (less pressure resistance of colder clinker) Air Flow Reduced heat transfer Risk of equipment overheating P 1 ≈ P 2 ≈ P 3 ≈ P 4 ≈ P 5 P 3 P 2 P 1 P 4 P 5

63. Compartment Sealing !!! Light check of holes in partition wall !!!

64. Correct Air Distribution The air pressure is adjusted to achieve the following air distribution The partition walls are tight P 1 > P 2 > P 3 > P 4 > P 5 P 1 P 2 P 3 P 4 P 5 Air Flow

65. Installation of hopper sensors Targets Improve hopper sealing by remaining clinker layer inside the hopper (minimize air losses) B6

66. False Air Minimization At cooler exhaust air system Kiln nose ring cooling Kiln inlet and out seal Doors, inspection windows Target: Reduce cold air intake B7

67. Final Messages Controlled Air Distribution Improve air distribution and clinker cooling curve Fan performance and control is important Compartment sealing is essential Target: Minimize cooling air losses

68. Questions

69. The 3 Basic (Golden) Rules for Clinker Cooler 3 rd rule: Operate with high clinker bed  low grate speed  increased heat recuperation A high clinker bed increases the residence time of the air in the clinker, essential for good heat exchange. The cooler should always be operated at the lowest possible grate speed. C1

70. Clinker Bed Height Increased clinker bed height  increased retention time of air and clinker  increased cooling time  improved heat transfer  improved clinker cooling A high clinker bed is the best protection for the grate plates !!!

71. Strokes per Minute

72. Cooling Time - Retention Time

73. Installed Fan Pressure Low installed fan pressure limits the clinker bed height in operation and therefore limits the heat recovery as well !!! Clinker bed height to be optimized to match fan and grate drive performance !!! Rule of thumb: 100 mm clinker bed = 10 mbar (for fan behind the static inlet)

74. Clinker Bed Height Low clinker bed (< 500 mm) Limited air retention time in clinker Short clinker retention time in cooler Short cooling time Low heat transfer Risk of grate plate overheating High clinker exit temperature Low secondary air temperature Limited heat recuperation Poor cooler efficiency Frequent equipment overheating High clinker bed (> 600 mm) Higher air retention time in clinker Long clinker retention time in cooler Increased cooling time Improved heat transfer Best protection for grate plates Lower clinker exit temperature Higher secondary air temperature Increased heat recuperation Good cooler efficiency Increased cooler availability

75. The 3 Basic (Golden) Rules for Clinker Cooler The completion of Rule 1: Keep the clinker on the grate and Rule 2: Controlled air distribution are pre-condition for Rule 3: Operate with high clinker bed

76. Grate Cooler Control Loops Kiln hood draft control Cooling air flow control Grate speed control Indirect control of the main cooler process temperatures (T Sec , T Ter and T clinker ) C2

77. Why Cooling Air (Fan) Control? Avoid air losses Improve air distribution Without control the cooling air flow varies due to pressure drop changes in the clinker bed

78. Basic Principle of Cooling Air Flow (Fan) Control Setpoint target: see fan operation table Actual air flow > setpoint  fan damper closes or fan speed reduces Actual air flow < setpoint  fan damper opens or fan speed increases V = constant V = constant

79. Air Flow Table

80. Why Grate Speed Control? Minimize fluctuations of recuperation temperature Avoid overfilling of the grate (downtime for manual emptying of the grate) Avoid emptying of the grate (overheating of the grate plates) Grate speed control prevents the clinker bed resistance from exceeding the pressure capabilities of the cooling air fans

81. Grate Speed Control (UG Pressure Control) V = const P ref = const Basic control principle: Actual UG pressure > setpoint  grate speed increase Actual UG pressure < setpoint  grate speed decrease Precondition: Constant flow of the reference fan

82. Setpoint of Grate Speed Control Setpoint = f (reference air flow) [m 3 /h/plate]

83. Disturbance of Grate Speed Control If reference flow is not constant: e.g. 3% flow fluctuation  up to 9% pressure dead band Dead band Grate speed may tend to over and under driving

84. Grate Speed Control (Level Control) h = const. h LevelRadar for direct measuring of the clinker bed height

85. Rules for Grate Speed Control Guideline for grate speed

86. Operation Interlocks Malfunction Action Grate drive tripped Kiln release taken off after 5 minutes Fan tripped in cooler inlet Grate drive stops after 5 minutes Fan tripped in remaining recuperation zone Grate drive stops after 5 to 10 minutes Fan tripped in cooling zone Grate drive stops after 15 to 20 minutes Clinker crusher tripped Grate drive stops immediately (after 5 minutes) Clinker transport tripped Grate drive stops immediately (after 5 minutes) Cooler exhaust air fan or kiln ID fan tripped Grate drive stops immediately Cooling air flow reduced to 50% Cooler exhaust air fan and kiln ID fan tripped Grate drive stops immediately All cooling air fans off immediately

87. Main Issues Grate Cooler Control Grate drives and grate speed control have a key function for heat recuperation and clinker cooling Reliable process indication  Reliable process control + interlocks  Increased equipment availability If it is not measured it will not be improved

88. Summary Clinker Cooler Golden rules for clinker cooler are key Gap management Air distribution + fan performance „Air Flow Table“ Compartment sealing is essential Clinker bed height = cooling time „Grate Speed Guidelines“ Automatic cooler control + interlocks

89. Questions