Impurities in boiler water

Impurities includes
DISSOLVED GASSES
CHEMICAL COMPOUNDS
SUSPENDED SOLIDS

Uncontrolled concentration of these impurities can cause corrosion problems.

1. Hardness
presence of calsium & magnesium. Normally presence in a CARBONATE @ BICARBONATE ->referred to as "carbonate hardness".

Hardness may also combined with sulfated, nitrates or chlorides which is reffered to "noncarbonated hardness"

May deposited as scale.

1.1 Calsium carbonates.
Form a tenacious scale.
Form a weak carbonic acid solution -> corroded the metals in the condensate system and contiminate the condensate with dissolved metals.

1.2 Calsium sulfates
Calsium sulfate scale
Ie gypsum

1.3 Magnesium bicarbonate
Decomposes to form Magnesium Hydroxide and CO2
A sticky sludge @ deposit as scale.
+ silica -> magnesium hydroxide and hydrochloric acid which may be removed as sludge.

1.4 Magnesium Chloride
Very soluble.
+ metal -> magnesium hydroxide and hydrochloric acid.
Corrode the boiler above the water line.

2. Silica
Or silicon dioxide SiO2
Form a hard, glassy coating on the boiler surfaces.
Deposited on turbine blades or piping.

Treatment -> phosphate treatment , external treatment or continious blowdown.

3. Iron and other suspended solids
4. Dissolved gases/oxygen and CO2
5. Alkalinity/causticity
6. PH