Boiler feedwater treatment is the filtration and conditioning of water before it enters the boiler, to ensure that the boiler itself remains clean, efficient and safe. Clean feedwater helps protect the tubes, drum and heat transfer surfaces of the boiler.
Where Boiler Filtration Is Required
- Boiler feed line: The last stage of filtration before water enters the boiler, protecting the drum and tubes.
- Boiler Pre-Treatment Skid: Protects softeners, RO and de-aerators supplying the boiler.
- Condensate return to boiler: Re-cleans recovered steam condensate prior to re-entry to the boiler.
- Boiler makeup water: For low scale formers and solids, reduces the amount of fresh water entering the boiler.
Contaminants that damage boilers
- Suspended solids and dirt – Coat boiler tubes
- Rust and corrosion particles – abrading and plugging boiler internals
- Hardness salts (calcium, magnesium) – cause boiler scale formation
- Silica – forms hard, heat insulating deposits on tubes
- Oil and grease cause foaming and carryover in the boiler
- Iron and manganese – Cause and accelerate boiler corrosion
- Organic matter and sludge foul the water side of the boiler
Process Problems In Filtration of boiler feedwater treatment:
| Issue | Cause | Impact on the Boiler | How Filtration Helps |
|---|---|---|---|
| Boiler Scaling | Hardness, silica in feedwater | Insulates heat-transfer tubes, raises fuel use, and causes tube overheating and failure | Helps remove suspended scale-forming particles before they enter the boiler |
| Internal Corrosion | Iron, oxygen byproducts, acidic contaminants | Thins boiler walls and can cause leaks and drum damage | Removes suspended corrosion particles from feedwater |
| Fouling of Boiler Surfaces | Sludge, oil, organics | Lowers steam output and boiler efficiency | Reduces suspended solids and contaminants entering the boiler circuit |
| Steam Carryover | Foaming caused by oil and dirt in boiler water | Wet, contaminated steam can damage turbines and downstream equipment | Helps control suspended contaminants that can contribute to foaming |
| Tube Plugging | Fine particles and scale | Restricts circulation, strains the feed pump, and increases the risk of dry-out | Uses graded filtration to capture particles and help protect the boiler circuit |
| Condensate Contamination | Oil and corrosion products in the condensate return | Returns damaging solids and contaminants to the boiler system | Filters condensate before it is reused as boiler feedwater |
Benefits of Filtration for Boilers:
- Protects boiler tubes and drum against scale, corrosion and fouling.
- Keeps heat-transfer surfaces clean, thus improving boiler efficiency.
- Prolongs boiler life and reduces unplanned shutdowns.
- Improves boiler performance. Reduces fuel and chemical cost.
- Provides clean steam, from a healthier boiler.