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

Chapter 44.2.3.5 Non-ferrous metal productionExamples are metallurgical processes like roasting, smelting or sintering of ores in order toyield metals, such as Cu, Zn or Pb. For a detailed description of non-ferrous metal production,see [61, European Commission, 2003].Non-ferrous metal smelting accounts for 39 % of H 2 SO 4 production (see also Table 4.3). Manymetal sulphides when roasted during metallurgical processes, produce gases containing SO 2 .The concentration of SO 2 in gases entering an acid plant, determines the amount of gas thatmust be treated per tonne of fixed sulphur. Often, smelters must be overdesigned in flowcapacity for adjusting the high and fluctuating metallurgical gas flow coming from the smelter.Furthermore, there is a minimum concentration of SO 2 that can be treated without increasing thenumber of stages in the plant. Table 4.4 shows some characteristics of metallurgical processesand the effects on the H 2 SO 4 production.Variation of theSO 2 concentrationper hourEffect on theconversion rate in %absoluteFluctuation ofSO 2 and/O 2>4 % v/v -0.4 extremely high2 – 4 % v/v -0.3 very high1 – 2 % v/v -0.2 high10 %Table 4.4: Some characteristics of metallurgical processes and their effect on H 2 SO 4 production[154, TWG on LVIC-AAF, 2006]For copper plants, it is typical to find not only fluctuations in the concentration of SO 2 inconverters, but also fluctuations in the gas flow. The reason is that about 30 % of converteroperating time is used for charging and slag tapping. Pyrometallurgical copper extraction isbased on the decomposition of complex iron-copper sulphite minerals into copper sulphides,followed by selective oxidation, separation of the iron portion as slag, and final oxidation of theremaining copper sulphide. These steps are known as roasting, smelting and converting (thepresent day tendency is to carry out the first two in a single process). The flash smelting processis currently one of the most widely used pyrometallurgical processes.Converters are used extensively to blow air or oxygen-enriched air through the copper matte toproduce blister copper. Virtually all the sulphur from the concentrates ends up as SO 2 . Aconcentrate of CuFeS 2 produces almost one tonne of sulphur (2 tonnes of SO 2 ) per tonnes ofcopper extracted.The development of copper processes has been dominated by two objectives. One is toeconomise on energy, making the maximum use of reaction heat obtained from the process. Theother has been the need to decrease the gas volume, and increase the concentration of SO 2 inmetallurgical gases by the use of oxygen enrichment, to improve environmental controls. Thegas is purified by cooling, scrubbing and electrostatic cleaning in order to remove dust and SO 3 .158 Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers