Electrostatic ignitions in enriched oxygen atmospheres: A case history

✍ Scribed by Thomas H. Pratt

• Publisher: American Institute of Chemical Engineers
• Year: 1993
• Tongue: English
• Weight: 327 KB
• Volume: 12
• Category: Article
• ISSN: 1066-8527
• DOI: 10.1002/prs.680120404

✦ Synopsis

Abstract

There have been instances where ignitions have occurred in oxygen enriched atmospheres in closed systems. The causes of these ignitions have been difficult if not impossible to explain by ordinary mechanisms, and even though electrostatics has been implicated, there have been no definitive mechanisms proposed which can explain the ignitions. This paper will perhaps be a step toward a satisfactory explanation by bringing another electrostatic mechanism to the attention of the loss prevention community.

In an example incident, ignition occurred when oxygen was bubbling to the surface of a liquid where flammable vapors existed. It is known that bubbles breaking at a liquid surface can create an electic field in the atmosphere above the liquid. Also, in real systems, there are all sorts of surface discontinuities and things floating about so that there are sharp points where it is conceivable that corona discharge may develop, depending on the strength of the electrostatic field. In ordinary atmospheres, corona discharge is only incendive to very sensitive vapors and is considered to be non‐incendive to ordinary vapors, but on the other hand, it is well known that the minimum ignition energy requirements for ordinary vapors in pure oxygen atmospheres are some 100 times less than those in normal atmospheres. Such a reduction in energy requirements could likewise be expected for corona discharge. One can then speculate that such a self induced corona discharge could have been capable of igniting the flammable vapors which were in an oxygen enriched atmosphere. The experimental and theoretical pros and cons of this mechanism are discussed in the paper with no definitive conclusion being reached.