Steam Plate Heat Exchangers Scaled By Calcium Carbonate

Steam plate heat exchangers type models, face scaling problem same as other regular shell and tube heat exchangers. Plate heat exchangers occupy less space and the surface of the plate works as heat transferring medium between hot and cold fluids.

  • Heat transfer from a warmer fluid to a cooler fluid, usually through a solid wall separating the two fluids, is common in engineering practice.
  • During phase change operations such as condensation or vaporization. Latent heat transfer play prominent role and in case of temperature rising or decreasing situation. One should concentrate on the sensible heat transfer in the  fluid where phase change do not take place.

Typical examples steam plate heat exchangers operation:

  1. Reducing the temperature of a fluid by transfer of sensible heat to a cooler fluid so that the temperature of cold fluid is increased.
  2. Condensing steam using cooling water.
  3. Vaporizing water from a solution at a given pressure.

All such above cases require that heat be transferred by conduction and convection.

Calcium carbonate forms as a scale on the surface area of the plate during the formation of steam or while cooling water circulations. Solid particle present in the fluid streams influence the CaCO3 to form as scale.

When the salt deposits on the surface and do not get dissolved into its source solution, then this mechanism referred to “scaling”. Inorganic components present in the water form this hard deposition unlike organic soft depositions.

100% calcium carbonate removal in cooling water and boiler feed water requires continues investment for scale removing chemicals. To solve this problem researchers have to find out the link between scale formation by calcium carbonate and particles present in cooling water or boiler feed water. When the relation is found than by controlling the particle matter scaling rate can be governed to improve performance of plate type heat exchanger.

Vaterite, calcite and aragonite these three forms of polymorphic calcium carbonates involve in scale formations. The reason for scaling of these compounds is due to the loss of carbon dioxide from there structure. Increase in pH make carbon dioxide splitting from calcium carbonate leaving out calcium to form hard materials. In supply line of cooling water or potable water, when temperature is increased it will lead to decrease in solubility of calcium carbonate and precipitate out as white crystals having high adherent quality.
In the list of heat exchangers, plate types HE designs have ability to prevent fouling. Particles of calcium sulphate particles will lead fouling and increase the rate of calcium carbonate scale formation. Suspended matter with 25 mg per liter show the scaling effect. Even soft scaling starts on continuous run of cooling tower water containing iron silicate, iron phosphate, copper oxide, silica, silt and haematite.