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Reduction of Rainwater Intrusion Into Deerhaven Unit 2 Coal Pile Reclaim System

Reduction of Rainwater Intrusion Into Deerhaven Unit 2 Coal Pile Reclaim System. John B. (Jack) Miller – Black & Veatch Ali McDaniel – Gainesville Regional Utilities. Overview.

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Reduction of Rainwater Intrusion Into Deerhaven Unit 2 Coal Pile Reclaim System

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  1. Reduction of Rainwater Intrusion Into Deerhaven Unit 2 Coal Pile Reclaim System John B. (Jack) Miller – Black & VeatchAli McDaniel – Gainesville Regional Utilities

  2. Overview Gainesville Regional Utilities (GRU) Recently Installed a Rain Shield Over the Coal Reclaim for Their Deerhaven Unit 2. This Presentation Will: • Describe the Process That Lead to the Decision to Install the Cover • Review the • Design Development • Design Features • Construction Process • Examine the Initial Measurements of Its Effectiveness JBM(8) - 2

  3. About the Authors • Ali McDanielMaterial Science Engineer – GRU’s Project and Construction Manager for This Project • Jack MillerMechanical Engineer – Black & Veatch’s Project Manager for the Feasibility Study and Detailed Design JBM(8) - 3

  4. About GRU • GRU Is a Municipally-Owned Utility Serving the City of Gainesville, Florida for 100 Years • Gainesville Is Located in North Central Florida • GRU Serves 87,000 Retail and Wholesale Customers • Owns and Operates Two Power Plants, John R. Kelly and Deerhaven Generating Stations • Installed Capacity of 611 MW to Serve a Peak Demand of 450 MW JBM(8) - 4

  5. About Deerhaven Unit 2 • Deerhaven Unit 2 Is a 235 MW Pulverized Coal-Fired Steam-Electric Generating Unit • Commissioned in 1982 • Burns Low Sulfur East Kentucky Compliance Coal JBM(8) - 5

  6. Aerial View of Deerhaven Generating Station Looking North Northeast JBM(8) - 6

  7. Problem Definition Annually 58 inches max. 48 inches avg. 34 inches min. • Rain!! • Wet Coal • O&M Impacts Plugging in the Reclaim, Conveying Storage and Milling Systems • Negative Impact to Thermal Efficiency • Can Cause Significant Unit Derates and Relatively Expensive Replacement Power • In 2003, Wet Coal Effects Directly Resulted in the Need for 12,879 MWh of Replacement Energy JBM(8) - 7

  8. Overview of Coal Handling System JBM(8) - 8

  9. Highlights ofCoal Handling Operations JBM(8) - 9

  10. Highlights of Coal Handling Operations • Coal Is Delivered by Unit Trains Carrying About 11,000 Tons • Unloaded From Track Hopper at 3,000 TPH • Conveyed to Dual Discharge Fixed Boom Stacker • Can Build 1,800 Ton Conical Coal Pile on North and South Sides JBM(8) - 10

  11. View of Stockout Tower Looking West JBM(8) - 11

  12. Highlights of Coal Handling Operations • Reclaim System Operates at 500 TPH (2" x 0" Coal at 15% Moisture) • Four Below-Grade Hoppers: Three on the South (Active Reclaim) • One on the North (Emergency Reclaim) • Hoppers Feed a Common 30-Inch Belt Conveyor • Conveys Coal to the Six Storage Bunkers Via a Crusher Tower • Bunkers Hold 18 Hours of Fuel at Typical Burn Rate • Coal Is Fed to Burners Through B&W MPS 75N, DVS Rotating Classifier Pulverizers JBM(8) - 12

  13. Graphic Display – Stockout and Reclaim System JBM(8) - 13

  14. Coal Pile Management Equipment • Excess Coal Is Moved From Stockout Pile to Long-Term Storage Using Dozers and Front-End Loaders • Takes Three Machines Three Days to Move and Spread 11,000 Tons JBM(8) - 14

  15. Analysis and Developmentof Solution JBM(8) - 15

  16. Analysis and Development of Solution • Wet Coal Effects Had Been Manageable Until Coal Fines Content Increased • In Late '90s, Began Using Lower Sulfur East Kentucky Coal • Sizing Changed From Nominal 2" x 0" to ¾" x 0" • Fines Increased Considerably • More Conducive to Plugging When Wet • More Conducive to Excessive Ratholing Above the Reclaim Hopper JBM(8) - 16

  17. Ratholing at the Center Reclaim Hopper Ratholing Provides Direct Path for Rainfall and Runoff to Enter the Reclaim Hopper and Flow Directly Onto Reclaim Belt  Primary Source of Entrained Water in the Coal and Attendant Problems JBM(8) - 17

  18. GRU Study • Correlation Between Rainfall and Need for Replacement Energy Due to Unit Derates • Short-Term Rain Events of Greater Than 2 Inches Cause Derates on a Proportional Basis  More Rain, More Replacement Energy Needed • Results for 2003 JBM(8) - 18

  19. B&V Study Potential Solutions • Improve Pile Management Practices  Reduce Fines Stratification • Modify Reclaim Equipment  Water Collecting Gates • Install Alternate Reclaim  Above Grade, Dewatering Dozer Trap • Install Cover Over Active Reclaim  Intercept Rainfall – GRU’s Preferred Alternative – Estimated Cost $1.5 Million JBM(8) - 19

  20. GRU Economic Analysis • Focused on Cost of Replacement Energy Resulting From Unit Derates • Recognized That 2003 Experience (12,879 MWh) Was Based on Above Average Rainfall • Conservatively Assumed Average Annual Derate of 40 MW for 120 Hours • Correlates to 4,800 MWh of Replacement Energy • Based on Fuel Forecast (Natural Gas and Coal) – Avoidance of Replacement Energy Yielded and IRR of 13.4%  Satisfied GRU Threshold JBM(8) - 20

  21. Design JBM(8) - 21

  22. Functional Design Criteria • Sized to Prevent Rainfall From Impinging on Active Reclaim Area • High Enough to Accommodate 1,800 Ton Conical Pile • Maximize Area of Coverage Within Space Between Stockout Tower and Perimeter Drainage Swale • Support System Cannot Impede Movement of Coal by Mobile Pile Management Equipment • Support Structure Should Be Resistant to Contact by Mobile Equipment • Must Accommodate Night Time Pile Management Operations JBM(8) - 22

  23. Other Design Criteria • Design Life: 30 Years • Environment: Subtropical Climate  Hot Summers; Mild Winters • Temperature and Humidity: 70 F and 90% – Design 115 F and 100% – Extreme Max 10 F – Extreme Min • Rainfall: 10-Year Return Period, 24-Hour Event  0.30 Inches Per Hour, 7.2 Inches Total • Wind Speed: Per the Florida Building Code (FBC) • Seismic: Aa = .05; Av = .05, Soil Profile S-3 • Grade: 189 msl • Lighting: 5 Footcandles of Illumination, Ability to Control Lighting Level JBM(8) - 23

  24. Design • Foundation System • 16 – 48 Inch x 55 Foot Drilled Piers • Reinforced Concrete Pier Cap  Two Piers Per Cap • 2' x 3' Reinforced Concrete Grade Beams • Cover Support Structure • Concrete Columns • Precast Concrete Beams • Top of Support Is 25 Feet Above Grade JBM(8) - 24

  25. Cover Support Structure – Concrete Columns and Beams JBM(8) - 25

  26. Cover and Its Structural Framework • Initial Concept Was a Geodesic Dome • Finally Selected a Rectangular Plan Arrangement to Maximize Coverage Within Allotted Area • Arched North to South  Clear Span of 175 Feet • 160 in Length East to West and 91 Feet Above Grade at High Point of Arch JBM(8) - 26

  27. Cover and Its Structural Framework • Trusses: • Fully Triangulated Space Truss • Truss Depth Is 8 Feet • 7 Trusses With 25 Foot Spacing • Fabricated From 8 Inch Wide Flange Aluminum Struts • Lateral Stability Provided by 4 Inch Aluminum Tubing • Framework Is Bolted Together • Skin: 0.050 Inch Thick Aluminum Skin Is Bolted to Frame • Lighting: • Interior: 24 HPS Fixtures Attached to Inside of Cover Framework • Exterior: 8 HPS Fixtures Attached to Support Structure • Each Switch Controls Six Fixtures  Provides Adjustability JBM(8) - 27

  28. Construction JBM(8) - 28

  29. Construction • Contracting Approach • Engineering – Black & Veatch (Owner’s Engineer) • Cover Supply (Detailed Design, Furnish and Erect) – Conservatek • General Construction – Yates Construction • Construction Management – GRU • Overall Schedule • Design, Fabrication and Delivery of Cover – 60 days • Erection of Cover – 60 days • General Construction • Original Schedule Was 4 Months • Actual Schedule Was 8 Months JBM(8) - 29

  30. Construction • Site Preparation • For Foundation and Support Structure Construction – Removed 50% of Coal From Active Pile • For Erection of Cover Framework and Skin – Rebuild Minimum Coal Base of 12 Feet to Function as Construction Platform • Coal Base Filled the 175' x 160' Covered Area Plus 30 to 50 Foot Margin on the East West and South Sides • Foundations and Concrete Support Structures • Six Week Delay in Mobilizing Drilled Pier Contractor • Encountered Unforeseen Subsurface Obstructions Causing Damage to Caisson • Installed 16-48 Inch Diameter Drilled Piers • Tied Pairs of Piers Together With Reinforced Concrete Pier Cap • Tied Outboard Pier Caps Together With 2 Foot by 3 Foot Grade Beams JBM(8) - 30

  31. Drilled Pier Caisson JBM(8) - 31

  32. Drilled Pier Installation Equipment JBM(8) - 32

  33. Damaged Drilled Pier Caisson JBM(8) - 33

  34. Pier Cap Form Work • Foundations and Concrete Support Structures • Poured in Place Concrete Columns Were Constructed on the Pier Caps • Precast Support Beams Were Placed on Top of the Columns JBM(8) - 34

  35. Concrete Support Structure – Lifting of Precast Beam JBM(8) - 35

  36. Concrete Support Structure – Positioning of Precast Beam JBM(8) - 36

  37. Concrete Support Structure – Setting of Precast Beam JBM(8) - 37

  38. Completed Concrete Support Structure JBM(8) - 38

  39. Erection of Cover and Supporting Structural Framework • Unique Design of Cover Necessitated Custom Designed Lifting Towers • Framed Two Bays at a Time  Lift  and Proceed. Once Peak Was Reached, Sheeting to the Mid-Point of the Cover Was Accomplished • The Process Was Conducted Two Bays at a Time in That Manner Until Complete JBM(8) - 39

  40. Erection Towers and Partially Completed Trusses JBM(8) - 40

  41. Positioning Erection Towers – Partially Completed Trusses JBM(8) - 41

  42. North Side of Trusses Resting on Concrete Support – Skin Partially Installed JBM(8) - 42

  43. Skin Installation About 2/3 Complete – Repositioning South Towers JBM(8) - 43

  44. Skin About 2/3 Complete – Opening for Stockout Chute Almost Complete JBM(8) - 44

  45. View of Erection Towers on South Side and Underside of Trusses JBM(8) - 45

  46. Close-Up View of Erection Towers on South Side JBM(8) - 46

  47. South Side of Cover Being Raised Onto Concrete Supports JBM(8) - 47

  48. Completing Setting of Cover on Concrete Supports JBM(8) - 48

  49. Completed Cover Looking Northwest JBM(8) - 49

  50. Completed Cover Looking Northeast JBM(8) - 50

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