Among phosphate and calgon methods, which one would be the best option for
internal conditioning. Explain your answers with supporting equations
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The best method used for Internal conditioning of hard water is the Calgon method.
Formation of scales of carbonates and bicarbonates are the primary problem encountered in softening of water as they spoil the boilers.
Although using the phosphate conditioning method also prevents the formation of scales, this method can be used only when the pH is above 9.5 because Calcium does not get deposited at lesser pH values. So, it requires a lot of boiler feeder water according to the pH range. Also, using too much Sodium carbonate (Na₂CO₃) can lead to caustic embrittlement.
In Calgon method, Sodium Hexa Meta Phosphate or Calgon is used in the form of tablets. Calgon reacts with the calcium ions to form a complex which is highly soluble complex. Therefore, it helps in preventing the precipitation of carbonate and bicarbonate salts that form scales. These precipitates can be easily removed.
Na₂[Na₄(PO₃)₆ + 2CaSO₄ + [Na₄P₆O₁₈]²⁻ → [Ca₂P₆O₁₈]²⁻ + 2Na₂SO₄
The CaSO₄ is from the boiler water and the formed [Ca₂P₆O₁₈]²⁻ can be removed easily.
Formation of scales of carbonates and bicarbonates are the primary problem encountered in softening of water as they spoil the boilers.
Although using the phosphate conditioning method also prevents the formation of scales, this method can be used only when the pH is above 9.5 because Calcium does not get deposited at lesser pH values. So, it requires a lot of boiler feeder water according to the pH range. Also, using too much Sodium carbonate (Na₂CO₃) can lead to caustic embrittlement.
In Calgon method, Sodium Hexa Meta Phosphate or Calgon is used in the form of tablets. Calgon reacts with the calcium ions to form a complex which is highly soluble complex. Therefore, it helps in preventing the precipitation of carbonate and bicarbonate salts that form scales. These precipitates can be easily removed.
Na₂[Na₄(PO₃)₆ + 2CaSO₄ + [Na₄P₆O₁₈]²⁻ → [Ca₂P₆O₁₈]²⁻ + 2Na₂SO₄
The CaSO₄ is from the boiler water and the formed [Ca₂P₆O₁₈]²⁻ can be removed easily.
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