Process Water Treatment

Process water covers the wide range of boiler feed water, cooling water for heat exchangers or engine, chemicals dilution, etc...

It should typically have a conductivity ranging from 0,1 to 50 uS/cm, with little to no hardness to avoid scaling in heating systems.

Oxygen and carbon dioxide should be removed to prevent corrosion.

Once demineralised, process water should be conditioned according to manufacturer's specification, usually up to pH 9 by adding caustic soda or ammonia.

Source Quality required Technology applied
500-2000 uS/cm 5-20 uS/cm Reverse Osmosis
  < 5 uS/cm 2-pass Reverse Osmosis
  < 1 uS/cm 2-pass Reverse Osmosis + Mixed bed
< 500 uS/cm < 5 uS/cm Ion exchange
  < 1 uS/cm Ion exchange + Mixed bed

Boiler Feed Water Treatment

Proper treatment of boiler feed water is an important part of operating and maintaining a boiler system. As steam is produced, dissolved solids become concentrated and form deposits inside the boiler. This leads to poor heat transfer and reduces the efficiency of the boiler. Dissolved gasses such as oxygen and carbon dioxide will react with the metals in the boiler system and lead to boiler corrosion. In order to protect the boiler from these contaminants, they should be controlled or removed.

Except for steam trap maintenance, water treatment has the most potential for reducing annual operating costs in a power plant.

 

Cooling Water Treatment

Prevention of corrosion is crucial in cooling systems. Hexavalent chromium-based ("chrome") compounds are used as efficient and cheap corrosion inhibitors. The trouble is, hexavalent chromium is a suspected carcinogen, and is highly toxic. Chrome emissions from cooling towers in New Delhi alone could cause as many as 700 cancer cases over a 70 year exposure period. Reverse osmosis and ion exchange provide a clean, safe way of removing mineral contaminants from cooling water without harmful chemicals.

Below are the desired characteristics of cooling water:

Suspended solids None
Conductivity 50-600 uS/cm
Hardness 8o dH max
pH 7.8
CO2 agressive None
Iron <0.3 mg/L
Manganese <0.05 mg/L
Sulfate <250 mg/L
Chloride < 250 mg/L
COD < 40 mg/L
Bacteria < 1000 CFU/ml