Phosphate Fertilizers: Production, Characteristics, and Technologies

Abstract

As in Chapter 1 (Stewart et al., 2005, this publication), this chapter has been written to serve both the scientific community (SI units) and fertilizer industry (non-SI units). In particular, fertilizer grades are expressed in an X-Y-Z format where X = available nitrogen (N), Y = available phosphorus (P) expressed as a weight percentage of P 2 O 5 equivalent, and Z = available potassium (K) expressed as a weight percentage of K 2 O equivalent. There is no equivalent system of fertilizer grades in the SI system other than expressing the composition as g kg Ϫ1 of N, P, and K. To convert %N to g N kg Ϫ1 multiply by 10, to convert P 2 O 5 to g P kg Ϫ1 multiply by 4.37, and to convert %K 2 O to g K kg Ϫ1 multiply by 8.33. For example, a 16-16-16 fertilizer in the N-P 2 O 5-K 2 O system would be 160-70-133 in a N-P-K system. In this chapter, the industry units of fertilizer and ore grades will be used and the reader can convert to SI units with the guidelines given above if needed. A related issue is the use of the term phosphate to describe P by the fertilizer industry. In a strict sense, the use of phosphate should be restricted to describe P in the form of orthophosphate (PO 4 Ϫ3) or condensed phosphates (e.g., P 2 O 7 Ϫ4). One cannot ensure that all P in ores or fertilizer products is present as phosphate. However, it is generally accepted that nearly all is in the form of phosphate in these materials and the term phosphate will be used in this chapter.

Increasing Soluble Phosphate Species by Treatment of Phosphate Rocks with Acidic Waste

“…Treatment of Araxá, Patos, and Bayóvar PRs with AMW increased the fertilizer value of the material as indicated by the increasing extractable amounts of P (P water , P NAC , and P CA ). The AMW-induced changes were somewhat consistent with those induced by reaction of PRs with pure acids such as sulfuric acid in the production of single superphosphate (SSP) fertilizer (Leikam and Achorn, 2005), for example: Results of XRD and XANES showed a loss of apatite with increasing AMW concentration between 12.5 and 75% (v/v), and XRD showed formation of gypsum and anhydrite ( Fig. 2 and 3; Table 3).…”

Safety Assessment of Phosphoric Acid and Its Salts as Used in Cosmetics

“…In the manufacture of Diammonium Phosphate, each stoichiometric equivalent of Phosphoric Acid is neutralized by approximately 2 equivalents of ammonia. 5…”

The fate of fertiliser P in soil under pasture and uptake by subterraneum clover – a field study using 33P-labelled single superphosphate

“…Managed grazing systems occupy approximately 25 % of the world's land surface, but pasture growth is often limited by phosphorus (P) (Asner et al 2004). Single superphosphate (SSP) is one of the main sources of P used across the world to overcome soil P deficiency and improve pasture (and crop) production (Leikam and Achorn 2005). In Australia, considerable improvements in pasture production have occurred since the introduction of subterranean clover and widespread use of SSP, which is typically applied to the soil surface of a pasture at 9 -12 kg P ha -1 year -1 (Donald and Williams 1954;Russell 1960;Weaver and Wong 2011).…”

“…single superphosphate), which was then denned and made into granules using a granulating drum. However, some of the issues with this procedure are: 1) it is complex and time consuming (Hedley et al 1988;Nunn and Dee 1954); 2) incomplete acidulation of the rock phosphate can occur (Bolan et al 1987;Nunn and Dee 1954); 3) as a by-product of the acidulation process a cocktail of fluorosilicic and hydrofluoric acid vapour is emitted (Leikam and Achorn 2005); 4) the source of phosphate rock can affect the chemical composition and solubility of the SSP (Braithwaite et al 1992;Hedley et al 1988); and 5) there can be a large variation in granule size and weight within each batch of fertiliser made (Braithwaite et al 1992;Fogel 1960). The relatively large amount of rock phosphate required for this procedure, and the low recovery of granules with a consistent size and weight needed for experimentation purposes, can cause a considerable dilution of radioactivity in the 'ideal' granules.…”