Investigation of Boiler Feed Water Oxygen Scavenger Adverse Results

Abstract

Industrial boilers and Heat Recovery Steam Generators (HRSG) play a crucial role in generating superheated steam for various industrial processes. To ensure the efficiency and longevity of these systems, it is essential to maintain water quality. Typically, water used in these systems undergoes filtration to remove suspended and dissolved solids. Subsequently, the water is treated by deaerators, with their primary function being the removal of dissolved gases, particularly oxygen. Oxygen is considered one of the most important contributors to pitting and corrosion in boilers and piping. To fulfill the critical role of eliminating oxygen, plant utilities such as deaerators use chemicals known as oxygen scavengers. One notable chemical in this category is carbohydrazide, known for its volatility and non-solid contributing properties. Carbohydrazide serves as an effective oxygen scavenger, aiding in the prevention of corrosion within the boiler feed water system. All deaerators in utilities plants are operated at temperatures above 275°F. This leads oxygen scavenger to decompose to hydrazine at the operating temperature of deaerators, which in turn leads the residual oxygen scavenger to be unrepresentative of the actual injected amount. In this assessment, the oxygen scavenger performance was reviewed and a better allowable sample result limit was found to capture the effect of the oxygen scavenger decomposition to hydrazine.