FW Contamination from Returning Condensate

In most boiler plants, a high percentage of the generated steam is condensed after use and returned to the pre-boiler section, where it is supplemented with sufficient MU to meet the current total FW demand at any particular time. Because this returned condensate or condensate return (CR) generally comprises the greater part of the FW supplied to the boiler, any contamination of the condensate may result in contamination of the FW system that is ultimately transported into the boiler section itself. 

Condensate contamination originates from several sources, including BW carryover into the generated steam, corrosion debris pickup 

In addition, the solids may cause fouling problems such as reduced deaerator venting, sticking check valves, and blocked feed pump. 

The contamination of returned condensate may develop in several ways. Where the steam-condensate system is subject to air infiltration, the result- 

Where problems develop, there is always a cause-and-effect process. In this case, as oxygen infiltrates the CR system, enhanced condensate line corrosion results (i.e., corrosion over and above the level that may be caused by the carbonic acid formed during steam condensation). This enhanced corrosion, in turn, creates the potential for further downstream corrosion debris pickup by the returning condensate and transporting this material back to the FW system. 

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Table 6.2 Summary of FW contamination from returned condensate...

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