This section covering phosphate fertilisers comprises these pages:

Introduction
Ammonium phosphates
Single superphosphate
Triple superphosphate
Phosphate fertilisers in combination with ammonium sulphate, ammonium chloride, ammonium nitrate, or urea
Other phosphate fertilisers
Use of phosphoric acid in various fertiliser processes
Environmental considerations

The production of fertilisers derived from phosphoric acid has increased significantly in the last 120 years because, among other things, these are concentrated, high-analysis products, thanks to the removal of calcium as by-product calcium sulphate in phosphoric acid production. Moreover, technical breakthroughs in the field of phosphoric acid and ammonium phosphate manufacture, plus economies of scale, have resulted in high capacity “world size” plants, which produce a limited range of products at very competitive prices.

Considering the situation from an environmental perspective, the tendency toward large plants has favourable aspects for several reasons:

• The sulphur used is increasingly a by-product of oil and natural gas cleaning.
• The calcium sulphate remains near the phosphate mine and in some cases is used to fill it.
• The liquid and gaseous emissions are better controlled and much lower per unit of production than in small local plants.
• More concentrated products are more efficiently transported.
• Precision blending of concentrated materials based on soil testing permits lower, more efficient application rates and decreases non-point-source pollution from farming.

Pollution control has been a major objective in the last 70 years. As a result of innovation and development, process improvements have refined scrubbing operations of MAP/DAP /NPK fertiliser plants so that effluents have decreased vastly [1,2]. This has been achieved by improvements in equipment but primarily by careful management of the scrubbing fluids to the extent that scrubbing has almost become a process by itself.

Nearly two-thirds of the P₂O₅ in fertilisers is derived from phosphoric acid. In fact, this figure is around 80% or more in North and Central America, Europe, North Africa, and West and South Asia, and around 50%-60% in other areas.

With minor exceptions, the commercial fertiliser products are triple superphosphate (TSP), ammonium phosphates (DAP and MAP), single superphosphate (SSP) and other compound fertilisers (some of the minor exceptions are potassium phosphates (MKP) and magnesium ammonium phosphate [MgNH₄PO₄, struvite]).

References

1. Benes, J. A., and H. Franzrahe. 1994. “Modifying Existing DAP /NPK Fertilizer Plants to Comply with new Environmental Regulations,” IFA Technical Conference Proceedings. Amman, Jordan.

2. Houghtaling, J., and V. J. Margiotti, Jr. 1994. “Advanced Ammonia Phosphate Scrubbing With Minimum Water Discharge,” IFA Technical Conference Proceedings, Amman, Jordan.

Links to related IFS Proceedings

2, (1947), Granulation of Phosphatic Fertiliser – Theory and Practice, Sven Nordengren

4, (1948), An Introduction to the Work of the Tennessee Valley Authority, A E Sell

4, (1948), T.V.A. Phosphatic Fertiliser Technology, E P Hudson

70, (1962), Origin of Processing of Phosphate Rock with Particular Reference to Benefication, Vincent Sauchelli

362, (1995), Forty Years with the Phosphate Industry – Nineteenth Francis New Memorial Lecture, A Davister

586, (2006), Phosphorus Fertilisation: Issues and Outlook, P Heffer, M P R Prud’homme, B Muirheid, K F Isherwood

707, (2012), Ma’aden Phosphate Company: a Dream Realised, M Al-Qahtani, A Al-Ajini, S Soundarapandian

803, (2017), Changes, challenges, and opportunities in fertiliser-manufacturing processes: A personal review and outlook, J G Reuvers