Calgon Conditioning in Boiler Water Treatment
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Questions and Answers

What is the purpose of using Calgon (sodium hexametaphosphate) in boiler water treatment?

  • To prevent the formation of calcium carbonate scale
  • To remove calcium sulfate scale by forming a soluble complex ion (correct)
  • To increase the alkalinity of boiler water
  • To neutralize the acidity of boiler water

    • What is the purpose of adding organic substances like kerosene, agar-agar, or tannin in low-pressure boilers?

  • To prevent scale formation
  • To remove dissolved oxygen from boiler water
  • To increase the alkalinity of boiler water
  • To condition the colloidal particles to yield non-sticky and loose deposits (correct)

    • What is the purpose of using sodium aluminate (NaAlO₂) in boiler water treatment?

  • To prevent scale formation
  • To increase the alkalinity of boiler water
  • To remove dissolved oxygen from boiler water
  • To remove calcium and magnesium ions by precipitation (correct)

    • What is the principle behind electrical conditioning of boiler water?

    <p>Electrical discharges from a mercury bulb cause water to boil, preventing scale formation</p> Signup and view all the answers

    What is the purpose of using radioactive salts in boiler water treatment?

    <p>To prevent scale formation</p> Signup and view all the answers

    What is the purpose of using EDTA (ethylenediaminetetraacetic acid) in boiler water treatment?

    <p>To remove scale-forming cations by forming stable, soluble complexes</p> Signup and view all the answers

    What is the term used to describe the degradation or destruction of boiler materials due to the chemical or electrochemical attack of dissolved gases or salts?

    <p>Boiler corrosion</p> Signup and view all the answers

    Which type of corrosion is caused by dissolved oxygen in the boiler?

    <p>Corrosion due to dissolved oxygen (DO)</p> Signup and view all the answers

    How is dissolved oxygen (DO) typically removed from boiler feed water?

    <p>By the addition of sodium sulphite or hydrazine</p> Signup and view all the answers

    Which chemical is commonly used for the removal of dissolved oxygen (DO) in the boiler?

    <p>Hydrazine</p> Signup and view all the answers

    What is the result of the presence of bicarbonate salts of magnesium or calcium in the boiler?

    <p>Release of CO2 causing slow corrosion</p> Signup and view all the answers

    In preventing caustic embrittlement, what role does adding lignin play?

    <p>Preventing infilteration of caustic soda solution</p> Signup and view all the answers

    What is the main cause of foaming in boilers?

    <p>Presence of oil in boiling water</p> Signup and view all the answers

    What is the process called when some particles in water are carried along with the steam?

    <p>Priming</p> Signup and view all the answers

    Which of the following is a disadvantage of priming?

    <p>All of the above</p> Signup and view all the answers

    What is the chemical reaction involved in removing oxygen from boiler feed-water by adding hydrazine hydrate?

    <p>$NH_2-NH_2 + O_2 \rightarrow 2N_2 + 2H_2O$</p> Signup and view all the answers

    Which of the following is a cause of priming in boilers?

    <p>Presence of large amounts of dissolved solids</p> Signup and view all the answers

    What is the purpose of adding alkali and anti-oxidant to boiler water?

    <p>To prevent corrosion</p> Signup and view all the answers

    What is the purpose of passing caustic soda solution (NaOH) through the anion exchanger?

    <p>To regenerate the anion exchanger</p> Signup and view all the answers

    What is the purpose of washing the cation exchanger bed with dilute sulfuric acid (H2SO4) solution?

    <p>To regenerate the cation exchanger</p> Signup and view all the answers

    What is the purpose of mixing the anion and cation exchanger beds using compressed air?

    <p>To create a mixed bed deionizer</p> Signup and view all the answers

    What is the recommended maximum concentration of total dissolved solids in potable water?

    <p>$500 ppm$</p> Signup and view all the answers

    Which of the following is not a requirement for potable water according to the text?

    <p>Free from objectionable minerals</p> Signup and view all the answers

    What is the main purpose of the water treatment process described in the text?

    <p>All of the above</p> Signup and view all the answers

    What are the reactions that take place when lime (Ca(OH)₂) and soda (Na₂CO₃) are added to hard water containing calcium salts?

    <p>Ca²⁺ + Na₂CO₃ → CaCO₃ + 2Na⁺ (calcium carbonate precipitation)</p> Signup and view all the answers

    What is the purpose of adding a coagulant like alum (aluminum sulfate) in the lime soda process?

    <p>To entrap and aid in the removal of fine calcium carbonate and magnesium hydroxide precipitates</p> Signup and view all the answers

    Which reaction takes place when lime (Ca(OH)₂) is added to hard water containing magnesium salts?

    <p>Mg²⁺ + Ca(OH)₂ → Mg(OH)₂ + Ca²⁺ (magnesium hydroxide precipitation)</p> Signup and view all the answers

    What is the reaction that takes place when soda (Na₂CO₃) is added to hard water containing magnesium salts?

    <p>Mg²⁺ + Na₂CO₃ → MgCO₃ + 2Na⁺ (magnesium carbonate precipitation)</p> Signup and view all the answers

    What is the reaction that takes place when lime (Ca(OH)₂) is added to hard water containing calcium bicarbonate (temporary hardness)?

    <p>Ca(HCO₃)₂ + 2Ca(OH)₂ → 2CaCO₃ + 2H₂O (calcium carbonate precipitation)</p> Signup and view all the answers

    What is the reaction that takes place when lime (Ca(OH)₂) is added to hard water containing magnesium bicarbonate (temporary hardness)?

    <p>Mg(HCO₃)₂ + 2Ca(OH)₂ → Mg(OH)₂ + 2CaCO₃ + 2H₂O</p> Signup and view all the answers

    Study Notes

    Boiler Water Treatment

    • Calgon (sodium hexametaphosphate) is used to prevent scales and corrosion in boiler water treatment.
    • Organic substances like kerosene, agar-agar, or tannin are added to low-pressure boilers to prevent foaming and carryover.
    • Sodium aluminate (NaAlO₂) is used to remove silica and other impurities from boiler water.
    • The principle behind electrical conditioning of boiler water is to reduce the formation of scales and corrosion by removing dissolved gases and salts.
    • Radioactive salts are not used in boiler water treatment due to their hazardous nature and lack of effectiveness.
    • EDTA (ethylenediaminetetraacetic acid) is used to remove impurities and prevent scales and corrosion in boiler water treatment.

    Corrosion and Oxygen Removal

    • Corrosion can occur due to the chemical or electrochemical attack of dissolved gases or salts, leading to degradation or destruction of boiler materials.
    • Pitting corrosion is caused by dissolved oxygen in the boiler.
    • Dissolved oxygen (DO) is typically removed from boiler feed water through the use of oxygen scavengers or deaeration.
    • Sodium sulfite is commonly used for the removal of dissolved oxygen (DO) in the boiler.

    Water Properties and Treatment

    • The presence of bicarbonate salts of magnesium or calcium in the boiler can lead to foaming and carryover.
    • Adding lignin helps prevent caustic embrittlement by reducing the alkalinity of the boiler water.
    • Foaming in boilers is mainly caused by the presence of dissolved gases or impurities.
    • Priming is the process of carrying particles in water along with the steam.
    • A disadvantage of priming is the reduction of boiler efficiency and potential damage to turbines.

    Chemical Reactions and Processes

    • Hydrazine hydrate is used to remove oxygen from boiler feed-water through the reaction: N₂H₄ + O₂ → 2H₂O + N₂.
    • Caustic embrittlement can occur due to the presence of caustic soda (NaOH) in the boiler water.
    • Alkali and anti-oxidant are added to boiler water to prevent corrosion and reduce the risk of caustic embrittlement.
    • Passing caustic soda solution (NaOH) through the anion exchanger helps to remove impurities and regenerate the exchanger.
    • Washing the cation exchanger bed with dilute sulfuric acid (H2SO4) solution helps to remove impurities and regenerate the exchanger.
    • Mixing the anion and cation exchanger beds using compressed air helps to regenerate the exchangers and improve their efficiency.

    Potable Water

    • The recommended maximum concentration of total dissolved solids in potable water is 500-600 ppm.
    • pH, temperature, and turbidity are requirements for potable water.
    • The main purpose of the water treatment process described in the text is to remove impurities and make water suitable for drinking or industrial use.

    Lime Soda Process

    • The reactions that take place when lime (Ca(OH)₂) and soda (Na₂CO₃) are added to hard water containing calcium salts are:
      • Ca(OH)₂ + Ca(HCO₃)₂ → CaCO₃ + 2H₂O
      • Na₂CO₃ + Ca(HCO₃)₂ → CaCO₃ + 2NaHCO₃
    • Alum (aluminum sulfate) is added as a coagulant in the lime soda process to remove impurities.
    • The reaction that takes place when lime (Ca(OH)₂) is added to hard water containing magnesium salts is:
      • Ca(OH)₂ + Mg(HCO₃)₂ → MgCO₃ + CaCO₃ + 2H₂O
    • The reaction that takes place when soda (Na₂CO₃) is added to hard water containing magnesium salts is:
      • Na₂CO₃ + Mg(HCO₃)₂ → MgCO₃ + 2NaHCO₃
    • The reaction that takes place when lime (Ca(OH)₂) is added to hard water containing calcium bicarbonate (temporary hardness) is:
      • Ca(OH)₂ + Ca(HCO₃)₂ → 2CaCO₃ + 2H₂O
    • The reaction that takes place when lime (Ca(OH)₂) is added to hard water containing magnesium bicarbonate (temporary hardness) is:
      • Ca(OH)₂ + Mg(HCO₃)₂ → MgCO₃ + CaCO₃ + 2H₂O

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    Description

    This quiz covers the concept of Calgon conditioning in boiler water treatment, including the formation of soluble complex ions of calcium and the use of Calgon tablets. It also includes information about colloid conditioning and treatment with NaAlO2 to prevent scale formation in low-pressure boilers.

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