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

Chapter 44.4.12 Prevention of catalyst activity lossDescriptionCatalysts suffer from deterioration while in operation. They are exposed to ageing by hightemperatures (loss of active components) and plugging by dirt. Some catalysts are occasionally“abused” by sulphur, fuel oil, water or sulphuric acid. At many metallurgical plants, the catalystis exposed to “poisoning” of the silica carrier by fluorides or volatilisation of the vanadiumthrough chloride attack.Regular screening and replacement is required, particularly at the first bed, where the catalystacts with a “fly-catching” effect to segregate residual dust and dirt from the gas. Proper gascleaning with adequately designed electrostatic mist precipitators will minimise this effect atmetallurgical plants, while sulphur burning plants can extend the screening periods substantiallyby ensuring perfect air filtration (e.g. two stage) and good sulphur filtration, e.g. by usingadditional polishing filters.Achieved environmental benefitsA loss of catalyst activity has a detrimental effect on the SO 2 conversion and the SO 2 emissions.Cross-media effectsNone believed likely.Operational dataNo specific information provided.ApplicabilityGenerally applicable.The driver for catalyst replacement/screening is usually the increased pressure drop or thenecessity of a boiler inspection. Since catalyst replacement/screening requires a plant shutdown,the costs are much higher, in the case of metallurgical plants, because the metallurgical processalso has to be stopped [75, MECS, 2006].Catalyst replacement according to [17, 2nd TWG meeting, 2004]:First bed:Other beds:after 2 – 3 yearsafter about 10 years.Catalyst screening (first bed) is carried out after 1 – 3 years, occasionally after 4 years,according to [68, Outukumpu, 2006].EconomicsNo specific information provided.Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers 191