Phosphate fertilizer complexes

Phosphate fertilizer complexes often have sulfuric and phosphoric acid production facilities. Sulfuric acid is produced by burning molten sulfur in air to produce sulfur dioxide, which is then catalytically converted to sulfur trioxide for absorption in oleum. Sulfur dioxide can also be produced by roasting pyrite ore. Phosphoric acid is manufactured by adding sulfuric acid to phosphate rock. The... 

Diammonium Phosphate (DAP). Ammonium phosphates did not come on the fertilizer scene in significant quantities until the early 1960s however, they have rapidly become the leading form of phosphate fertilizer in the world. Almost all new phosphate fertilizer complexes built in recent years, and those planned, are for the production of ammonium phosphate as the major product. In 1960, world production of ammonium phosphates was equivalent to only 0.5 million mt of P205. By 1990 it was up to 15.4 million mt and by 1999 it has reached 16.7 million mt. Ammonium phosphates now provide two-thirds of total world phosphate fertilization. 

Since about 1968, triple superphosphate has been far outdistanced by diammonium phosphate as the principal phosphate fertilizer, both in the United States and worldwide. However, production of triple superphosphate is expected to persist at a moderate level for two reasons (/) at the location of a phosphoric acid—diammonium phosphate complex, production of triple superphosphate is a convenient way of using sludge acid that is too impure for diammonium phosphate production and (2) the absence of nitrogen in triple superphosphate makes it the preferred source of phosphoms for the no-nitrogen bulk-blend fertilizers that frequendy are prescribed for leguminous crops such as soy beans, alfalfa, and clover. 

Modem commercial wet-acid purification processes (see Fig. 4) are based on solvents such as C to Cg alcohols, ethers, ketones, amines, and phosphate esters (10—12). Organic-phase extraction of phosphoric acid is accompHshed in one or more extraction columns or, less frequently, in a series of countercurrent mixer—settlers. Generally, 60—75% of the feed acid P2 s content is extracted into the organic phase as H PO. The residual phosphoric acid phase (raffinate), containing 25—40% of the original P2O5 value, is typically used for fertilizer manufacture such as triple superphosphate. For this reason, wet-acid purification units are almost always located within or next to fertilizer complexes. 

Tricresyl phosphate (a complex mixture containing tri-o, Xn-m-, and tri-para-cresyl phosphate that is used in certain hydraulic fluids) and TOCP are demonstrated testicular toxicants in rodents (Carlton et al. 1987 Somkuti et al. 1987a, 1987b). Tricresyl phosphate also has been shown to impair in vivo fertility in rats and mice (Carlton et al. 1987 Chapin et al. 1988a). In addition, tricresyl phosphate-treated female rats displayed vacuolar cytoplasmic alteration of ovarian interstitial cells (Carlton et al. 1987 NTP 1994). Reproductive effects have also been seen after oral exposure to butylated triphenyl phosphate (Latendresse et al. 1994b). 

Figure 15 Example of an environmentally balanced industrial complex with a phosphate fertilizer plant as the focus industry (from Ref. 24).

Nitric Phosphate. Fertilizers that are referred to as nitric phosphate or nitrophos-phate are produced by acidulation of phosphate rock with nitric acid or with mixtures of nitric and sulfuric or phosphoric acids. The primary advantage of nitric phosphate processes is that no sulfur or less sulfur is required as compared with superphosphates or ammonium phosphates this is particularly important during a shortage of sulfur, or in locations where sulfur must be shipped long distances. A variety of processes and equipment have been used in Europe since the late 1930s.3,12 Also there are a number of plants in Central and South America and in Asia. The production of nitric phosphates is complex. Simple substitution of nitric acid in a superphosphate-type acid-rock reaction is not feasible because (1) decomposition of the nitric acid would occur and cause noxious fumes and loss of nitrogen and (2) the product would be extremely hygroscopic and unstable. 

Martinez-Aguirre et al. (1994) have performed an extensive study of the presence of natural radioactivity around a phosphate fertilizer factory complex situated in an estuarine area of southwest Spain. The study has concluded that the wastes from such industries are the cause of the enhancement of natural radioactivity in the immediate environment. Thus, significantly high levels of U and Th-isotopes and Ra are detected in water and sediment samples collected in this area. These conclusions, based on the enhanced isotopic concentrations, are further supported by the measured U, Th and Ra isotopic activity ratios being quite different from any observed elsewhere in undisturbed estuaries. These isotope activity ratios appear to be very sensitive indicators of waste disposal practices in such environments. 

Compared with bulk soils, solid-phase speciation of Cd differs substantially in phosphate fertilizer-treated rhizosphere soils (Krishnamurti et al., 1996). The amounts of Cd associated with organic complexes in rhizosphere soils at the... 

Nitrophoska . [BASF AG] Complex nitrogen/phosphate fertilizer for agric., horticultural crops. 

It can be anticipated that various other metals will eventually be separated either from sea water or from the waste evaporator brine. Many metals are concentrated from sea water by phosphate precipitation during production of the magnesium ammonium phosphate fertilizer. Future metal recovery processes may utilize the fertilizer as a raw material. Because the evaporator brine contains a high concentration of chloride, a number of metals will be present in it as chloride complex anions (7). Many of these complex anions may be removed from the brines on an anion exchange resin such as Dowex 1 and then recovered from the resin simply by washing the column with fresh water. 

Compared with bulk soils, solid-phase speciation of Cd differs substantially in phosphate fertilizer-treated rhizosphere soils (Krishnamurti et al., 1996). The amounts of carbonate-bound Cd and metal-organic complex-bound Cd species of the rhizosphere soils at 2-week plant growth stage, particularly in the soils treated with Idaho phosphate fertilizer, are appreciably higher than those of the corresponding bulk soils (Fig. 4). In comparison to the corresponding bulk soils, the amount of carbonate-bound Cd species of the rhizosphere soils increased by 15-18% in the control soils and by 79-92% in the soils treated with Idaho phosphate fertilizer, whereas the metal-organic complex-bound Cd species increased by 4-7% in the control soils and by 2-3 times in the soils treated with Idaho phosphate fertilizer. The increase in the carbonate-bound Cd... 

Large amounts of sulfuric acid are consumed in the manufacture of phosphatic fertilizers, ammonium sulfate, etc. for every tonne of P2O5, 3 tonnes of 100% sulfuric acid is required. The process for the manufacture of phosphoric add by acid treatment of rock phosphate is complex and requires careful selection of the technology. The major processes for the manufacture of phosphoric acid are ... 

No new phosphate plants were built, and no major new potash mines were opened in North America or Europe during the period 1980-95. One new nitrogen fertilizer complex (SASFERCO in Canada) was constructed during that time period. 

Many phosphate ores have high iron contents that render them undesirable for chemical processing into fertilizers. Iron minerals are often present as iron oxides coating the surface or interlocking with the phosphate grains. Complex iron-containing silicates (such as am-phiboles, micas, and clays) are another major source of iron in most phosphate ores. Iron may also be present as iron phosphates. 

The problem of using phosphogypsum as a raw material for comlined sulfuric acid and cement production has drawn the attention of various companies. A cement/ sulfuric installation was proposed in 1990/91 for the Pine Level FVoject at Consolidated Minerals, Inc. [17]. It was to be a part of the integrated complex comprising a 1.0 million tpy P2O5 phosphate fertilizer plant, a 2.35 million tpy portland cement plant, a 660-MW coal-fired power station, and a 4.5 million tpy preconcentrate phosphate mine, with 0.9 millim tpy of sulfur equivalent recycled. 

Rosenblom, Jan, and Stig Zettervall. 1978. Anticaking Treatments of Granular Inorganic Salts Such as Phosphate Based Complex Fertilizers and Ammonium Nitrate, IN Proceedings of the Soviet-Swedish Symposium on the Benefi-ciation of Phosphate Rock, pp. 158-179, Tallinn, Estonia. 

Lignosulfonate-metal complexes are weaker complexes than those formed from amine-based complexing agents such as ethylenediaminetetracetic acid (EDTA). They are compatible with most pesticides/herbicides, but their use in phosphate fertilizers is not recommended... 

Copper. Some 15 copper compounds (qv) have been used as micronutrient fertilizers. These include copper sulfates, oxides, chlorides, and cupric ammonium phosphate [15928-74-2] and several copper complexes and chelates. Recommended rates of Cu appHcation range from a low of 0.2 to as much as 14 kg/hm. Both soil and foHar appHcations are used. 

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