Research on the Stability of an N20 Metal Powder System

摘要

The Bureau of Mines investigated nitrous oxide (N2O) stability when used as a solvent for organic removal from metal powder surfaces. Both supercritical and subcritical conditions were studied. The investigation was prompted by the occurrence of a violent reaction when supercritical N2O was being used to deoil a metal powder grinding waste sample that contained 20 to 25 wt pct cutting oil. Tests were conducted to determine the cause of the reaction and to define stability limits. Test data showed that the waste's oil fraction reacted violently with N2O acting as an oxidizer; the metal powder acted as a promoter to reduce the ignition temperature. The temperature appeared to reach a minimum at a certain pressure (dependent on vessel and sample size). As the sample size increased, the ignition temperature decreased. Because of the variability of ignition temperature with pressure and sample size, safe operating conditions were not established. Overall, the research showed that extreme caution should be exercised when using N2O in an organic or organic-metal system.