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

Chapter 33.4 Techniques to consider in the determination of BAT3.4.1 Oxidation catalyst performance and campaign lengthDescriptionCatalyst performance is negatively affected by:• poisoning by air pollution and contamination from the ammonia• poor ammonia-air mixing• poor gas distribution across the catalyst.This may reduce the NO yield by up to 10 %. Additionally, local ammonia excesses in theburner are a plant safety risk (based on LEL) and could also cause the catalyst gauze tooverheat. To minimise these effects, some plants use magnetic filters to remove any rust fromammonia, static mixers to give a high quality mixture and an additional filtration step applied tothe ammonia/air mixture. Burner heads often contain a perforated plate or honeycomb grid toensure good distribution. The gas velocity over the catalyst gauze must be steady.Gauze composition. Platinum is usually alloyed with rhodium to improve its strength and toreduce catalyst loss. In the past, rhodium was more expensive than platinum, increasing thecost. A rhodium content of 5 – 10 % has been shown to be optimal. If a low reactiontemperature, i.e.