Question

why calgon conditioning is better then phosphate conditioning

Answer 1

In calgon Conditioning, the added calgon forms soluble complex compound with CaSo4, thereby it prevents the scale and sludge formation in water.
Na₂[Na₄(PO₃)₆]⇄ 2Na⁺ + [Na4(PO₃]₆²⁻
2CaSO4 + [Na₄(PO3)₆]²⁻ ---> [Ca₂(PO₃)₆²⁻ + 2 Na₂SO4
this soluble complex does not cause any problem in boilers.
on the other hand, in phosphate conditioning, Sodium phosphate is added to the boiler water so that precipitate of calcium phosphate is formed. Although this precipitate is non adherent and soft it has to be removed by frequent blow down operation.
2Na₃PO4 + 3 CaSO4 ---> Ca₃(PO4)₂↓ + 3 Na2 SO4.
Hence calgon conditioning is better than phosphate conditioning.