30 Questions
What is the purpose of using Calgon (sodium hexametaphosphate) in boiler water treatment?
To remove calcium sulfate scale by forming a soluble complex ion
What is the purpose of adding organic substances like kerosene, agar-agar, or tannin in low-pressure boilers?
To condition the colloidal particles to yield non-sticky and loose deposits
What is the purpose of using sodium aluminate (NaAlO₂) in boiler water treatment?
To remove calcium and magnesium ions by precipitation
What is the principle behind electrical conditioning of boiler water?
Electrical discharges from a mercury bulb cause water to boil, preventing scale formation
What is the purpose of using radioactive salts in boiler water treatment?
To prevent scale formation
What is the purpose of using EDTA (ethylenediaminetetraacetic acid) in boiler water treatment?
To remove scale-forming cations by forming stable, soluble complexes
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?
Boiler corrosion
Which type of corrosion is caused by dissolved oxygen in the boiler?
Corrosion due to dissolved oxygen (DO)
How is dissolved oxygen (DO) typically removed from boiler feed water?
By the addition of sodium sulphite or hydrazine
Which chemical is commonly used for the removal of dissolved oxygen (DO) in the boiler?
Hydrazine
What is the result of the presence of bicarbonate salts of magnesium or calcium in the boiler?
Release of CO2 causing slow corrosion
In preventing caustic embrittlement, what role does adding lignin play?
Preventing infilteration of caustic soda solution
What is the main cause of foaming in boilers?
Presence of oil in boiling water
What is the process called when some particles in water are carried along with the steam?
Priming
Which of the following is a disadvantage of priming?
All of the above
What is the chemical reaction involved in removing oxygen from boiler feed-water by adding hydrazine hydrate?
$NH_2-NH_2 + O_2 \rightarrow 2N_2 + 2H_2O$
Which of the following is a cause of priming in boilers?
Presence of large amounts of dissolved solids
What is the purpose of adding alkali and anti-oxidant to boiler water?
To prevent corrosion
What is the purpose of passing caustic soda solution (NaOH) through the anion exchanger?
To regenerate the anion exchanger
What is the purpose of washing the cation exchanger bed with dilute sulfuric acid (H2SO4) solution?
To regenerate the cation exchanger
What is the purpose of mixing the anion and cation exchanger beds using compressed air?
To create a mixed bed deionizer
What is the recommended maximum concentration of total dissolved solids in potable water?
$500 ppm$
Which of the following is not a requirement for potable water according to the text?
Free from objectionable minerals
What is the main purpose of the water treatment process described in the text?
All of the above
What are the reactions that take place when lime (Ca(OH)₂) and soda (Na₂CO₃) are added to hard water containing calcium salts?
Ca²⁺ + Na₂CO₃ → CaCO₃ + 2Na⁺ (calcium carbonate precipitation)
What is the purpose of adding a coagulant like alum (aluminum sulfate) in the lime soda process?
To entrap and aid in the removal of fine calcium carbonate and magnesium hydroxide precipitates
Which reaction takes place when lime (Ca(OH)₂) is added to hard water containing magnesium salts?
Mg²⁺ + Ca(OH)₂ → Mg(OH)₂ + Ca²⁺ (magnesium hydroxide precipitation)
What is the reaction that takes place when soda (Na₂CO₃) is added to hard water containing magnesium salts?
Mg²⁺ + Na₂CO₃ → MgCO₃ + 2Na⁺ (magnesium carbonate precipitation)
What is the reaction that takes place when lime (Ca(OH)₂) is added to hard water containing calcium bicarbonate (temporary hardness)?
Ca(HCO₃)₂ + 2Ca(OH)₂ → 2CaCO₃ + 2H₂O (calcium carbonate precipitation)
What is the reaction that takes place when lime (Ca(OH)₂) is added to hard water containing magnesium bicarbonate (temporary hardness)?
Mg(HCO₃)₂ + 2Ca(OH)₂ → Mg(OH)₂ + 2CaCO₃ + 2H₂O
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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