Due to the effect of heat and evaporation, different chemical and physical processes in the boiler water take place, a series of compounds are decomposed and a series of other compounds are produced ... In many cases this process leads to the formation of insoluble compounds that separate from the saturated solution as deposits and under certain conditions turn into deposits or sludge. Deposits adhered to the heating or cooling surface are capable of disrupting the normal operation of the boiler.
The chemical composition of residue produced in boilers is very different, but they can be divided into four different groups:
1. Alkaline earth metal deposits mainly include compounds of calcium and magnesium: CaCO3, CaSO4, CaSiO3, Ca3 (PO4) 2, MgO, Mg (OH) 2, Mg3 (PO4) 2. Depending on the amount of substances that are abundant in the deposits, people can distinguish CaCO3 carbonate deposits, CaSO4 sulphates, Ca3 (PO4) 2 phosphates, and so on. many compounds.
Iron oxide deposits: In the composition of this sediment there may be iron silicates, iron phosphate Fe2 (PO4), 3, sodium iron phosphate NaFePO4 iron oxide Fe2O3, Fe3O4.
3. Copper deposit: In the composition of the scale but a large amount of copper.
4. Silicate deposits have different components. The most important property of a scale is its low thermal conductivity, which varies depending on the structure and porosity of the deposited matter.
Typical processing technology diagram
To prevent scale build-up in the boiler the main method is to thoroughly soften the boiler feed water and raise the pH to prevent scale formation.
Water softening is mainly based on the ion exchange process, because this process reduces most of valence ions. Raising the pH often uses NaOH soda to alkaline soft water for the boiler, because if using Soda Na2CO3, NaHCO3, they are easy Hydrolyzed in the boiler water produces CO2 gas, contaminating the steam and causing a rusting effect on the condensate glands.
Typical water treatment technology diagram for standard sources of living, tap water and well water contaminated with mild iron.