Keywords: Catalyst, Nitric acid, Platinum.

The production of nitric acid for fertilizer production requires platinum group metals for the catalyst to oxidise ammonia. This paper describes the factors which are taken into consideration in the design of the catalyst pack and catchment system to recover platinum.

The ability to manufacture a range of different densities of knitted gauzes and the novel Bispinâ configuration allow the specification of an optimised catalyst pack for each application. This approach is based on the analysis of the mass transfer characteristics of each gauze. The use of Optimised Mass Transfer has been shown to prolong the oxidation of ammonia through a deeper catalyst pack giving a higher conversion for the same weight of precious metal installed.

The benefits of a catchment system for precious metal recovery are discussed. The improvements gained with MTL catchment technology using palladium gauzes and the effects of nickel or copper additions are explained.

Mass transfer considerations are also applied to the MTL catchment pack to improve efficiency.

Finally the recovery of platinum group metals by plant cleaning is described with additional long term benefits.

Stéphane Marret and Louis du Chatelier, Engelhard-Clal - Industrial Platinum Division, France

44 pages, 23 figures, 9 refs.