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Condensate Purity for High Pressure Boilers

  • 1.  Condensate Purity for High Pressure Boilers

    Posted 21 days ago
    Hi! I'm a process engineer for an ammonia plant, and I'm designing a treatment system for our recovered steam condensate.  My plant operates a 1500 psig boiler.  About 60% of the feed water to the boiler comes from the condensate that is recovered in our surface condensers.  This condensate is pumped directly to the deaerator, where it mixes with the rest of the boiler feed water.  Most of the time, this source of condensate is very clean.  However, without any means of pretreatment, the boiler water quality is vulnerable to upsets that could contaminate the steam condensate (condenser tube leaks, air in-leakage, etc.) I plan to install an amine-form cation resin polisher upstream of the deaerator to remove trace impurities like Na+, Ca2+, and Mg2+.  For the design parameters, I do not know what breakthrough points at which I should consider my resin to be 'exhausted'.  Through researching high pressure boilers, I know the advisable Na+ concentration in the feed water is 2 ppb or less.  Similarly, the supposed cation conductivity target is under 0.25 μmhos.  However, from operational experience without any condensate treatment, I know that continuous Na+ levels of 5 ppb has been tolerable.  What limits are you using on your boiler feed water quality (Na+, cation conductivity)?

    I realize many folks in the power industry operate supercritical boilers.  As a result, they often use mixed bed resin polishers, and abide by even strickter boiler feed water constraints.  If possible, I'd love to hear from folks that operate boilers similar to our 1500 psig system.

    Thank you,

    Nathan Grubb
    Process Engineer
    Hopewell, VA