LIME SOFTENING

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LIME SOFTENING STABILIZATION
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Murder Parties
Ralph Rottingrape
Marilyn Merlot
George W. Taliban
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Pen Ta Gon Advisor to the Emperor
Queen Illicibeth Gridlock, the Merchant of Tennis
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(No Transcript)
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Classifying Water Hardness
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What is lime?

• Limestone, mainly calcium carbonate, CaCO3
• Quicklime, calcium oxide, CaO
• Slaked lime, calcium hydroxide, Ca(OH)2

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Limestone mining, preparation and use
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Limestone Mining, contd
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Limestone Mining, contd
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Limestone Handling and Shipping
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Lime Conversions

• Limestone can be converted to quick lime
  CaCO3 ? CaO CO2 (1800F)
• Quick lime is slaked with water CaO
  H2O ? Ca(OH)2
• Slaked lime slowly reacts with CO2 in air
  
  Ca(OH)2 CO2 ? CaCO3 H2O
• Dissolved lime (hardness) can precipitate Ca(HCO3
  )2 ? CaCO3 H2O CO2

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Lime Kilns
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Calcination of Limestone
CaCO3 ? CaO CO2
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Hydration slaking with water
Water reacts with the quicklime to form hydrated
lime CaO H2O ? Ca(OH)2

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The removal of divalent metal ions Precipitation/s
ettling or IX resins
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Typical lime softening process

Ca(OH)2 Lime
? ?
?

Lime sludge
presented as a complete drinking water
treatment process
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LIME SLAKING
and DOSING
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Precipitation occurs in a settling tank
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LAGOON DEWATERING
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Why are we concerned about corrosion?
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Stability Relationship

• The basic Relationship in Stabilization

Has been simplified by Powell, Bacon and Lill
to pHs p(Ca2) p(Alk) C
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Powell, Bacon and Lill Diagram
Langelier index
mg/L
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Modified Caldwell Lawrence Diagram