Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

Chapter 33.4.3 Alternative oxidation catalystsDescription• improved platinum catalysts show modifications in composition and the geometry of thecatalysts can lead to a higher ammonia conversion to NO and/or to a reduction in theproduction of N 2 O. Simultaneously, an extension of the campaign length is possible.Examples are the FTC and FTCplus catalysts by Heraeus or oxidation catalyst fromUmicore [87, infoMil, 2001, 105, Müller, 2003, 145, Nitrogen2003, 2003]• alternatively, Co 3 O 4 based catalysts have been available for 30 years. Some sources claimhigher ammonia conversion efficiencies (94 – 95 %), whilst others say this is only 88 –92 % in a high pressure plant. Normally, the NO yield in an existing nitric acid plant willbe approximately between 93 and 97 %. Additionally, the lifetime of the catalyst is longer,reducing the number of plant shut-downs and lower pressure drop is observed. Hightemperatures and reduction of Co 3 O 4 to CoO leads to catalyst deactivation• in the republics of the CIS, two-step catalysts are used extensively. One or several platinumgauzes are used as the first step, and a bed of non-platinum oxide catalyst is used as thesecond step.Achieved environmental benefits• the example plant achieved a reduction of 30 – 50 % N 2 O with an improved platinum-basedHeraeus catalyst [105, Müller, 2003]. An M/M example plant achieves, with this catalyst,N 2 O emission levels of 500 – 1000 ppm in half year campaigns, on average about 800 ppm.The other example plant (M/M) achieves 600 – 700 ppm N 2 O• a reduction of up to 30 % N 2 O may be achieved with an improved platinum-based catalyst[87, infoMil, 2001]• it has been demonstrated that alternative oxidation catalysts produce up to 80 – 90 % lessN 2 O than platinum-based catalysts, however the benefits might be offset by a lower NOyield and hence increase NH 3 consumption• the use of two-step catalysts reduces the amount of platinum used by between 40 – 50 %and platinum losses are reduced by 15 – 30 % under similar conditions.Cross-media effectsNone believed likely.Operational dataSee description.ApplicabilityAs optimised platinum catalysts or alternative catalysts become available on the market, it canbe anticipated that these catalysts will be suitable for all nitric acid plants, both new andexisting, operating at any pressure.Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers 115