(104a) Recognizing on-Line Zirconium Oxide Oxygen Analyzers as an Ignition Source in Fired Equipment

Oxygen analysis is required for process control of furnaces and boilers. Analyzers commonly installed are on-line zirconium oxide oxygen analyzers in the stack area to provide fast and reliable measurements of the oxygen content of the flue gas exiting the firebox. This allows for precise control of the excess combustion air in the firebox, resulting in higher energy efficiency for the unit. On-line zirconium oxide oxygen analyzers, whether in situ model or close coupled extractive model, include a probe element designed to operate at 700 C, which is well above the auto-ignition temperature of most flammable hydrocarbons. This paper will discuss typical in situ and close coupled extractive zirconium oxide oxygen analyzer design, how the probe can be a source of ignition, and review an incident in a Dow cracking furnace as a result of an in situ zirconium oxide oxygen analyzer igniting a flammable mixture in a furnace.