KANUPP - IAEA Training
Boiler Feedwater / Condensate Chemistry Control
Boiler Feedwater / Condensate Course Objectives
• • State the purpose of secondary side chemistry control. State what chemicals are added to the secondary side, the purpose of each chemical, and where each chemical is added. State the chemical parameters monitored in the secondary side by plant instrumentation, their sampling points, approximate values and what alarms/indications are available in the MCR. Appreciate the need for good communication between the CRO and Chemical Maintainer with respect to alarms received in the MCR, i.e., out of spec parameters, low tank levels, power changes, bypassing of ...view middle of the document...
(All Volatile Chemistry Treatment) Can produce acidic conditions under deposits or in crevices which can result in stress corrosion cracking of boiler tubes. High levels in combination with oxygen can cause pitting of boiler tubes and carbon steel components. Can also result in generalized corrosion of carbon steel support plates which can cause boiler tube “Denting”. Corrosion of materials in the Condensate/Feedwater system Corrosion products are transported to the boilers where they accumulate on the tubesheet and tube support plates - increased boiler deposits. Increased deposits can also result in decreases in heat transfer at the boiler tube surfaces which in severe cases can result in power derating.
Calcium & Magnesium : Increased boiler deposits. Silica: Increased boiler deposits.
Specific Conductivity - conductivity of the solution contributed by all the dissolved ionic species. e.g. cations (Na+, Li+, Cu++, Ca++, Mg++, NH4+, N2H4+, C4H9ON+ , etc) anions (Cl-, F-, NO3-, SO4--,PO4--- etc) Cation Conductivity - conductivity of solution contributed by dissolved ionic impurities/contaminants. e.g. cations (Na+, Cu++, Ca++, Mg++) are exchanged with H+. The anions that remain (Cl-, F-, NO3-, SO4--, PO4--- ) now are in the for of mineral acids and are highly conductive giving a rise in the conductivity of the solution (Sample stream of feedwater passed through a cation resin in the R-H+ form)
Cation Conductivity Measurement
Color indicating resin brown- exhausted Duplicate Resin Cartridges purple - fresh
Condensate - Feedwater - Boiler System Chemistry Control
Condensate Chemistry Control
• Maintain Dissolved Oxygen Levels Low: Location and elimination
of sources of air in-leakage in the sub-atmospheric portions of the turbine/condenser system. Hydrazine addition.
Maintain Alkaline pH Conditions: Addition of Morpholine. Plants
with copper alloys in the condensate system operate at slightly lower than optimum pH conditions (for carbon steel). High amine concentrations can result in stress corrosion cracking and condensate grooving of copper containing components. Hydrazine concentrations also limited to the minimum necessary for oxygen scavenging due to ammonia formation due to hydrazine decomposition. Since Point Lepreau system does not have copper components, high morpholine & hydrazine concentrations can be tolerated ...... morpholine is maintained at @ 15 mg/Kg & hydrazine is maintained between 60 - 80 ug/Kg.
OM 78210, Appendix 1. Actions upon Detection Of a Condenser leak
Sodium or Cation Conductivity in alarm on one or more Condensers. AND Sodium or Cation Conductivity in alarm on the CEP Discharge
CD01 CD02 CD03
WII-6 CI 1873 NA+ AI 2764 Cat Con Al 2766
Wll-6 CI 1873 AI 0551 Al 0564 AND