The TDS inside a boiler should be maintained at recommended levels else it can lead to scaling of the boiler tubes and eventually failure of the tubes which is a safety hazard.
Maintaining high TDS levels in the boiler can lead to scaling on the tube side. Scale creates a problem because its thermal conductivity is much less than the corresponding the corresponding value of bare steel. Even thin layers of scale serve as an effective insulator and retard heat transfer. The result is overheating of boiler tube metal, tube failures and loss of energy efficiency.
Scale deposits occur when calcium, magnesium, and silica, commonly found in most water supplies, react to from a continuous layer of material on the waterside of the boiler heat exchange tubes.
Independent of the size of the boiler, prevention of scale formation can produce substantial energy savings. Scale formation can be best dealt with in two major ways,
- Reducing the incoming feedwater TDS
- Maintaining the TDS levels in the boiler
Feedwater tds is maintained by chemical pretreatment of water and blowdown maintains the boiler TDS levels. As we all know failure of boiler tubes can even be explosive at times and thus hazardous.
Condensate being pure, its recovery to feedwater tank reduces the requirement for addition of chemicals and maintains / reduces the feedwater TDS level and also the boiler blowdown frequency, thus saving energy.