indexes CALCIUM CARBONATE

indexes CALCIUM CARBONATE
Calcium carbonate is probably the most common type of scale found in cooling water
systems; it forms an extremely tenacious heat insulating deposit.
Calcium and bicarbonate alkalinity are found in almost all cooling waters. The addition
of heat, or a sharp rise in pH, will cause calcium bicarbonate to decompose and form
carbon dioxide and calcium carbonate.
Ca(HC03)2—-> CaC03+C02
Although the bicarbonate salt is moderately soluble, the carbonate salt has very low
solubility. The figure below shows the relationship of temperature to the solubility of
calcium carbonate.
Note that calcium carbonate is extremely low in solubility at any temperature. It is
logical that the deposition of calcium carbonate is found along heat transfer surfaces
where cooling water is subjected to the highest temperatures.