Abstract
One of the primary objectives in boiler feedwater preparation is the minimization of dissolved oxygen. The presence of even minute amounts of oxygen - in the parts-per-billion range - is corrosive to ferrous metals, manifesting itself quite clearly as localized pitting failures, and leading to the transport of scale-binding impurities in the steam cycle.
While it is the function of a properly operating deaerator to remove over 99% of the incoming oxygen in the feedwater, from roughly 8 ppm to below 10 ppb, the necessity for a chemical scavenger to remove the last traces of oxygen is quite obvious to ensure the reliability of the steam generating system. The ability to monitor the efficiency of such scavengers through the determination of dissolved oxygen levels, the detection of the presence of the scavenger or a reducing environment, and the quantification of iron and copper levels throughout as much of the system as is warranted, is an instrumental part of any water treatment program to maintain the integrity of the operation.
This paper reports the field performance of various compounds in their ability to minimize the potential for oxygen-induced corrosion, by the aforementioned analytical procedures. The study explored the capabilities of hydrazine, methyl ethyl ketoxime, and carbohydrazide to scavenge oxygen and render a more protective environment at an ammonia-producing plant.
