Combined ammonia/oxygen conditioning of water/steam circulation systems in power stations

The following comprises a summary of the main results of about forty individual contributions and discussions from a two-day workshop (supplemented by more recent studies of relevant literature), classified systematically under three main headings: laboratory investigations; operational experience; applicability of results to other types of circulatory systems (natural-circulation boilers, secondary coolant loops of pressurised water reactors, auxiliary and generator cooling water circuits). The laboratory investigations relate to factors (pH, rate of flow, temperature, electrical conductivity, ammonia and oxygen contents) which influence uniform, surface corrosion, pitting corrosion and crack formation with specific types of material (copper-base alloys, unalloyed, low-alloy and high-alloy steels). Operational experience (based on eight power stations with varying unit output, duration of operation and changeover procedures) of dosing techniques in the event of load fluctuations, ammonia corrosion, pressure drops across the boiler, functional efficiency of condensate-polishing plant, hydrodynamic slip-ring seals and stellite-clad valves is described in detail and conclusions are drawn with regard to future design considerations and measures to reduce damage. (orig.)