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

Chapter 55.2.2.1 Raw materials5.2.2.1.1 Phosphate rock[31, EFMA, 2000]Table 5.2 and Table 5.3 give an overview of phosphate rocks from different origins.Phosphate ores are found in two major geological origins: igneous or sedimentary. Thephosphate minerals in both types of ore are of the apatite group, of which the most commonlyencountered variants are fluorapatite Ca 10 (PO 4 ) 6 (F,OH) 2, and francoliteCa 10 (PO 4 ) 6-x (CO 3 ) x (F,OH) 2+x . Fluorapatite predominates in igneous phosphate rocks andfrancolite predominates in sedimentary phosphate rocks.The most easily mined phosphate deposits are found in the great sedimentary basins. Thesesedimentary deposits are generally associated with matter derived from living creatures and thuscontain organic compounds. These phosphates are interposed with sedimentary strata of theother materials interpenetrated by gangue minerals, thus sedimentary phosphate ores can havediffering compositions even within the same source.Most phosphate ores have to be concentrated or beneficiated before they can be used or sold onthe international phosphate market. Different techniques may be used at the beneficiation stage,to treat the same ore for removal of the gangue and associated impurities. This gives rise tofurther variations in the finished ore concentrate product. Phosphoric acid technology has to relyon raw materials of variable consistency and the technology needs to be constantly adapted tomeet raw materials variations.According to IFA the supply of phosphate rock in the EU in 2004 was provided by Morocco(47.5 %), Russia (24.3 %), Jordan (8.1 %), Syria (6.2 %), Tunisia (4.9 %), Israel (4.2 %),Algeria (3.8 %) and others (1.0 %) [2, IFA, 2005].5.2.2.1.2 Sulphuric acid[29, RIZA, 2000]The types of H 2 SO 4 mainly used as raw material in the production of phosphoric acid are acidproduced from elemental sulphur, fatal acid (from non-ferrous metal production) and spent acid.The amounts of impurities introduced into the process by H 2 SO 4 are generally low or negligiblecompared to the amount introduced by the phosphate rock. Only in the case of mercury andpossibly lead, H 2 SO 4 may contribute significantly, especially when fatal acid is the main type ofH 2 SO 4 used. Typical mercury contents are:• for H 2 SO 4 from elemental sulphur