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Platinum Metals Rev., 1964, 8, (4), 127

Novel Isotope Technique in Nitric Acid Plants

Tracing Metal Losses from Platinum Alloy Gauzes

  • H.C.

A significant factor in the economics of nitric acid production is the loss of rhodium-platinum from the gauzes employed in the ammonia oxidation converters. These losses are particularly important in high-pressure plants, where they may be more than ten times as high as in low or atmospheric pressure plants.

Karel Akerman and co-workers at the Institute of Nuclear Research, Warsaw, have described a series of experiments carried out in a nitric acid plant at Tarnow, Poland, aimed at tracing the whereabouts of the platinum alloy lost in operation (Przemysl Chemiczny, 1964, 43/6, 306). A platinum gauze containing 2 per cent iridium was neutron activated in a reactor until it contained an activity of approximately 280 mC resulting from the formation of Ir192. This isotope has a half-life of 74.4 days and proved much more suitable for the experiments than the shorter lived isotopes Ir194 and Pt197 that are also formed. The latter were ehminated from the irradiated gauze by storing it for two weeks before use.

The activated gauze was placed with other rhodium-platinum gauzes in the converter, and the plant operated for thirty-eight days. Activated platinum alloy that had been lost from the gauze was traced throughout the plant with a scintillation counter and the various dust deposits located. It was found that the rate of loss was highest shortly after start-up of the plant and that a good estimate of the dust filter efficiency could be obtained.