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TECHNICAL BOILER TRAINING

TECHNICAL BOILER TRAINING. Introduction. Water is the raw material most used in nearly all industries. US industry uses about 140 billion gallons per day. The Water Molecule. Oxygen and hydrogen share electrons - this is called covalent bonding. The bond angle is 105 degrees. H. O.

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TECHNICAL BOILER TRAINING

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  1. TECHNICAL BOILER TRAINING

  2. Introduction • Water is the raw material most used in nearly all industries. • US industry uses about 140 billion gallons per day.

  3. The Water Molecule Oxygen and hydrogen share electrons - this is called covalent bonding. The bond angle is 105 degrees. H O 105 deg H

  4. The Hydrologic Cycle

  5. FUNDAMENTALS OF AVAILABLE WATER SURFACE WATER • Lower in dissolved solids • Higher in suspended solids • Quality changes quickly with seasons and weather GROUND WATER • Higher in dissolved solids • Lower in suspended solids • Higher in iron and manganese • Low in oxygen, may contain sulfide gas • Relatively constant quality and temperature

  6. Basic Water Chemistry

  7. FOUR IMPORTANT CHEMICAL PROPERTIES OF WATER ARE: 1. Conductivity 2. Hardness 3. Alkalinity4. pH

  8. CONDUCTIVITY A Measure of the Total Dissolved Solids (TDS) in the Water. Read in µS/cm Approximation: ppm TDS x 1,8 = µS/cm

  9. HARDNESS The amount of Calcium and Magnesium ions in the water Total hardness and Ca-hardness Read in ppm CaCO3

  10. Water - the Universal Solvent • Water is a poor conductor of electricity. • As more ions dissolve, water becomes a better conductor.

  11. Total Dissolved Solids Conductivity Water - the Universal Solvent This phenomenon is used to indicate total dissolved solids.

  12. ALKALINITY Carbonate or Bicarbonate Ions that Can Cause Scaling Problems together with Ca, Mg Ions. Read in ppm CaCO3

  13. M P O Free OH- and CO3= FMA and CO2 HCO3- becoming CO3= CO2 becoming HCO3- 0 4.3 8.2 9.8 Acid - Base Chemistry • The most common buffering system encountered in industrial plants is the carbonate buffering system. pH

  14. Acid - Base Chemistry The actual distribution of carbonate species Carbonate Buffering System 100 90 CO2 HCO3- CO3= CO2 80 HCO3- CO3= 70 60 50 Molar ratio 40 30 20 10 0 0 4 8 12 0.8 1.6 2.4 3.2 4.8 5.6 6.4 7.2 8.8 9.6 10.4 11.2 12.8 13.6 pH

  15. Acid - Base Chemistry Expressing hydrogen ion concentrations: pH = negative log molar concentration of H+ pH H+ Conc. 5 1.0 ppb 6 0.1 ppb 7 0.01 ppb 8 0.001 ppb

  16. Water - the Universal Solvent Expressing the levels of dissolved solids: per cent - used for concentrated solutions ppm - a weight relationship ppm as CaCO3 - an equivalent weight relationship mg/l - same as g/ml - in dilute waters, same as ppm

  17. FUNDAMENTALS OF WATER • SPECIFIC HEAT • is the measure of how well a substance can absorb heat • 1 Kcal/kg°C • VAPORIZATION HEAT • Energy to transform liquid to gaseous • 970 Kcal/kg at 100°C

  18. Pretreatment Filtration Softener Dealkalizer Reverse Osmoses Demineralizer Dearator

  19. PRETRATMENT SOFTENER

  20. Softening Regeneration with NaCl CaMg Na Na Ca Na Ca Mg Na Mg Na Na Softener - Ion Exchange Process Water Ion Exchange Resin

  21. Four Steps of Softener Regeneration Backwash Brining Slow Rinse Fast Rinse

  22. Ca, Mg Na, Na

  23. Boiler tube failure due to scaling and overheating of tube metal over critical temperature for steel This leads to partial destroyed boiler sections and even boiler explosion

  24. Deaeration: Water Temperature is Increased So That CO2 and O2 Are Released from the Water Water is Broken Into Small Droplets CO2 and O2 Are Removed By Venting

  25. Solubility of Oxygen vs Temperature and Pressure

  26. Oxygen Causes Pitting Attack of metaldue to Oxygen Corrosion Increased Iron content in condensate/boiler Increases TDS in boiler Corrosion Cell Dearator

  27. Pitting by Oxygen Corrosion

  28. Spray Deaerator

  29. Tray Deaerator

  30. Venting Requirements for Tray Deaerators

  31. Types of Deaerating Equipment Open feedwater heaters 0.5 to 1 ppm O2 Vacuum degasifiers 0.29 to 0.43 ppm O2 2 to 10 ppm CO2 Deaerators and deaerating heaters 0.04 ppm O2 for heater 0.007 ppm O2 for deaerators 95% of free CO2

  32. Major Problems Corrosion Scale

  33. Boiler Corrosion Types of Corrosion Oxygen corrosion Alkalinity concentration Caustic corrosion Acid corrosion Chelant corrosion Erosion/Corrosion

  34. Effect of pH on Boiler Corrosion

  35. Effect of Scale on Heat Transfer

  36. Effect of Scale on Tube Temperature

  37. Scale Problems Boiler tube failure Caused by reduced heat transfer and tube overheating Under-deposit corrosion Caused by high concentration of corrosive agents (usually NaOH)

  38. Scale Prevention Precipitation of hardness in the boiler Reduce amount of hardness entering boiler Keep the hardness soluble

  39. Treatment With Makeup Softening Requirements for Success Proper Operation and Maintenance of Make-up Equipment Chemical Conditioning for Residual Hardness

  40. Process Objective To produce the required amount of Steam To produce the required pressure Steam To produce the required purity Steam To produce Steam efficiently

  41. How Is the Steam Used Heat only Steam drives such as turbines Is process contamination a concern

  42. The Generation of Steam Is Energy Intensive Need to minimize the amount of energy used Need to maximize efficiency of the boiler An understanding of how a boiler works and proper measurements can reduce energy usage.

  43. Make-up Water SecondaryPretreatment PrimaryPretreatment Condensate Steam Header Deaerator Boiler Feedwater ChemicalFeedSystems Blowdown

  44. Boiler: Produces Steam Variety of Shapes and Sizes Variety of Fuels Wide Range of Operating Pressures

  45. TDS Boilerwater TDS Feedwater t/h Feedwater (BFW) t/h Blowdown Nc Number of Cycles = or Steam (t/h) Nc - 1 BFW (t/h) Nc Blowdown (t/h) = or TDS Feedwater TDS Boilerwater x 100 Blowdown in % BFW = Nc Nc - 1 BFW Boiler Feedwater (t/h) = Steam (t/h) x Boiler Calculations • Calculations

  46. Fire-Tube Boiler

  47. Fire-Tube Boiler - Circulation

  48. Filter or Coagulation Water Steam CO2 Oxygen Ca++ and Mg++ Pretreatment Softening Dearation Condensate tank & line SurgeTank Steam ReturnedCondensate SteamTurbine Process Process Knockout Potor Flash Tank Boiler Water - Steam - Condensate System POTENTIAL PROBLEM

  49. Why is CondensateNaturally Corrosive? Alkalinity in Boiler Breaks Downto CO2 CO2 Leaves with Steam Steam Condenses with CO2 toForm Carbonic Acid

  50. Why is Condensate corrosive? Caustic Alkalinity of BFW breaks down in BoilerBicarbonate 2 NaHCO2 Na2CO3 + CO2 + H2OSoda Na2CO3 + H2O 2 NaOH+ CO2 CO2 leaves with steam and reacts with condensed water droplets to Carbonic AcidCO2 + H2O H2 CO3Carbonic acid Acid attack to metals low pH % Conversion Pressure (bar)

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