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

Chapter 4Cross-media effectsNone believed likely.Operational dataIn general, the process uses gases with an SO 2 content of 10 to 11 % [58, TAK-S, 2003]. Theinlet gas temperature is about 400 ºC. Gases with lower temperatures, e.g. metallurgical gasesafter purification, require reheating from 50 to 400 ºC. This is usually carried out with recoveredheat from the conversion process [57, Austrian UBA, 2001].Applicability• applicable for SO 2 inlet content of 5 – 12 % v/v [58, TAK-S, 2003]• applicable for SO 2 inlet content of >4.5 up to 14 % v/v. Below 4.5 % v/v, double contactprocesses do not work autothermally [59, Outukumpu, 2005].Pressure contact process. One plant is known to operate a double contact process at an elevatedpressure of 5 bar. This increases the conversion rate by shifting the conversion equilibrium andfavouring the formation of SO 3 . The pressure double contact process achieves 99.8 – 99.85 %conversion; here, the tail gas contains 200 – 250 ppm SO 2 . The disadvantages are higherelectricity consumption and, at the same time, less steam production. Higher NO x emissions arecaused by higher sulphur combustion temperatures (1800 ºC). In comparison, savings of 10 – 17% on investment costs are gained. However, the benefits from building a plant for smaller gasvolumes (at higher pressure) are offset by more stringent safety regulations and additional costsfor pressure resistant materials.EconomicsThe double contact/double absorption process is considered as the baseline for inlet gas SO 2concentrations >4.5 % v/v.Driving force for implementationDevelopment of the single contact/single absorption process.References to literature and example plants[57, Austrian UBA, 2001, 58, TAK-S, 2003], Donau Chemie AG, Lenzing AG, Degussa AGLarge Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers 175