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2018 Coal Blending and Slag Formation.pdf

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2018 Coal Blending and Slag Formation.pdf

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This mostly self explanatory presentation discusses what properties of coal blend well, and the impacts it may have on combustion. Wall slag is discussed along with the Rod Hatt Splat Factor, where I try to show how low CV coal can increase slag by itself. For more coal information please see our social media page: http://www.coalcombustion.com/social%20media.html
Lots of free videos and articles.

This mostly self explanatory presentation discusses what properties of coal blend well, and the impacts it may have on combustion. Wall slag is discussed along with the Rod Hatt Splat Factor, where I try to show how low CV coal can increase slag by itself. For more coal information please see our social media page: http://www.coalcombustion.com/social%20media.html
Lots of free videos and articles.

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2018 Coal Blending and Slag Formation.pdf

  1. 1. Blending Coals Impacts on Slag 1 Rod Hatt
  2. 2. Ash Deposits Slagging - Molten Fouling - Sulfate Salts
  3. 3. Most Slag Starts on walls
  4. 4. Coal Blending Chemical Data Blends • Heating Value • Sulfur • Ash Chemistry
  5. 5. Coal Blending Physical Test - Difficult • Hardgrove (HGI) • Ash Fusion Temps • Combustion Properties
  6. 6. Measuring Coal Quality Coal Lab Testing only produces average data Power plants respond to swings in quality
  7. 7. Does this coal meet spec? 5.7 6.1 Average Plant Limit
  8. 8. Measuring Coal Quality Coal Lab Testing only produces Bulk or Total Quality PC power plants respond to Individual Particle
  9. 9. SiO2 Fe2O3 Al2O3 CaO TiO2 MgO K2O Na2O Acid Oxides Basic Oxides Glass Formers Fluxes Ash Chemistry
  10. 10. Base/Acid = Fe2O3+CaO+MgO+K2O+Na2O SiO2+Al2O3+TiO2
  11. 11. Slag and Fouling Index Bituminous SI = %dry sulfur x B/A FI % sodium X B/A Sub-Bituminous % Sodium (Na2O) You are on your own?
  12. 12. Slag is a build up of rate process so, the amount of ash should matter.
  13. 13. 17 Lets look at all boiler related coal qualities on a heat basis; lets put all percentages on a per million Kcal basis LOADING LEVELS
  14. 14. Kg. of ash/MKcal = %ash / (Kcal/10,000)
  15. 15. Kg. of element/MKcal = %ash / (Kcal/10,000) X (%Element/100)
  16. 16. Many slagging concerns have been addressed using Ash Loading and Elemental loading levels; especially Fe2O3, CaO, Na2O
  17. 17. Lessons Learned From Experience 1. Ash Fusion Temps do not work 2. Increase in Moisture Causes more Slag 3. Lowering Sodium by Dilution Causes more Slag
  18. 18. B/A Ratio Fusion Fusion verse Base to Acid Ratio Low Sulfur Bit Mid/High Sulfur Fe2O3 High Calcium Sub Bit 0 0.5 1.0 1.5
  19. 19. Can Not Blend Fusions (1200 + 1200) = 1100 ? 2
  20. 20. Amount of Ash Matters
  21. 21. 18 Month Study 1300 MW PC Boiler Slag Observations Coal Quality Statistical Review #1 – Did you have slag yesterday #1 CQ - Moisture
  22. 22. Sub-Bit Impacted by OSD (Rock)
  23. 23. Bit Coal Combustion 30
  24. 24. Sub-Bit Coal Combustion 31
  25. 25. Coal Combustion 32
  26. 26. Coal Combustion 33
  27. 27. Coal Combustion 34
  28. 28. Sub-Bit Coal Combustion 35 Quartz and rocks stay big, sticking in wet wall.
  29. 29. Splat Factor Velocity is Important Kinetic Energy = Mass x (velocity)2 2 Large dense particles Pyrite Quartz, rock Coal pipe velocity Low Btu, Hi Moist. Hi PA Flow
  30. 30. SPLAT FACTOR Coal Pipe Velocity increases due to: 1. High PA flow (mill A/F) 2. Low CV coal 3. High moisture
  31. 31. SPLAT FACTOR 1. Calculate KE for Quartz and Pyrite particles 2. Multiply KE times Q & P loading levels 3. Multiply result by % on 50 mesh screen (>300 microns)
  32. 32. SPLAT FACTOR Low with low levels of large particles Low with low levels of ash and sulfur Lowers with less PA flow A/F is important
  33. 33. Coal Combustion 43 Bituminous 1.Maintain 70%+ passing 200 mesh screen 2.High Calorific Value and low moisture allow for low mill loading 3.Lower Primary Air due to lower coal flow can allow for rejects
  34. 34. Coal Combustion 44 Sub - Bituminous 1.Maintain 70% passing 200 mesh screen to Minimize Slag, (lower to increase ton rate) 2.Low Calorific Value and high moisture make for high mill loading 3.High Primary Air for drying and high coal flow sends reject material into the furnace
  35. 35. Advice – Set up plant 1.Pulverize to meet Un-reactive coal 2.Pulverize for slag control-not carbon 3.Maintain CV to take load off mill or 1.Change Expectation – Load, Forced Outage Rate (SLAG, TUBE LEAK) Maintenance
  36. 36. www.asiansbcusers.com 46 Thank You

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