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LIME SOFTENING LIME SOFTENING & STABILIZATION & STABILIZATION

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Page 1: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

LIME SOFTENING LIME SOFTENING & STABILIZATION& STABILIZATION

Page 2: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Murder Parties

Ralph Rottingrape

Marilyn MerlotGeorge W. Taliban

Page 3: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Queen Illicibeth; Gridlock, the Merchant of Tennis

Pen Ta GonAdvisor to the Emperor

Page 4: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban
Page 5: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Classifying Water Hardness

Description of water Hardness expressed as mg/L of CaCO3

Soft less than 50

Moderately soft 50–75

Slightly hard 75–150

Hard 150–300

Very hard greater than 300

Page 6: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

What is “lime”?What is “lime”?

• Limestone, mainly calcium carbonate,

CaCO3

• Quicklime, calcium oxide, CaO

• Slaked lime, calcium hydroxide,

Ca(OH)2

Page 7: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Limestone mining, Limestone mining, preparation preparation and useand use

Page 8: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Limestone Mining, cont’d

Page 9: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Limestone Mining, cont’d

Page 10: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Limestone Handling and Shipping

Page 11: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

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

Page 12: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Lime Kilns

Page 13: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Calcination of Limestone

CaCO3 CaO + CO2

Page 14: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Hydration: slaking with water

Water reacts with the quicklime to form hydrated lime:

CaO + H2O Ca(OH)2

Page 15: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Water SofteningWater Softening

The removal of divalent metal ions Precipitation/settling or IX resins

Ca(HCO3)2 + Ca(OH)2 2CaCO3¤ + 2H2O

Mg(HCO3)2 + 2Ca(OH)2 Mg(OH)2¤ + 2CaCO3¤

Note that the CaCO3 precipitated is chemically identical to limestone

The removal of divalent metal ionsPrecipitation/settling or IX resins

Page 16: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Typical lime softening process…

Lime sludge

Ca(OH)2

Lime

…presented as a complete drinking water treatment process

Page 17: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

LIMESLAKING

…andDOSING

Page 18: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Precipitation occurs in a settling tank

Page 19: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

LAGOONDEWATERING

Page 20: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Why are we concerned about corrosion?

Page 21: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Stability Relationship

• The basic Relationship in Stabilization

pHs p Ca2 p Alk. pKi CaC03 pKsp CaC03 Has been simplified by Powell, Bacon and Lill to

pHs = p(Ca2+) + p(Alk) + C

Page 22: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Powell, Bacon and Lill Diagram

mg/L

Langelier index

Page 23: LIME SOFTENING & STABILIZATION. Murder Parties Ralph Rottingrape Marilyn Merlot George W. Taliban

Modified Caldwell Lawrence Diagram