Yara Hemihydrate (HH) and Hemidihydrate (HDH) Processes for Phosphoric Acid Production

Yara own, operate and license fertiliser plants and technologies throughout the world. Phosphoric acid production is an important part of the Yara licensing portfolio. Formerly known as Hydro Agri and prior to that, Fisons, we have successfully designed and commissioned several world scale hemihydrate and hemidihydrate process phosphoric acid plants over the course of the last forty years. The largest of these plants was the IPL (formerly WMC) HH process phosphoric acid plant in Queensland, Australia. This single line grass roots 1500 tpd P2O5 plant has now been successfully operating for over ten years. The HH and HDH processes are characterised by producing high strength phosphoric acid directly from the hemihydrate filters; either negating or significantly reducing the degree of acid concentration required for downstream processes. The HH process is therefore energy efficient, simple to operate and as most of the aluminium reports to the solid phase, the phosphoric acid is of high quality. The HDH process is a two stage process whereby the hemihydrate produced in the energy efficient first stage is transformed to dihydrate in the second stage and the liberated P2O5 losses present in the hemihydrate produced in the first stage are recovered, resulting in a very high P2O5 recovery efficiency. This paper focuses on the hemihydrate technologies developed by Yara (as Fisons Fertilizers) and looks forward to the next major hemihydrate complex at Ras Az Zawr in the Kingdom of Saudi Arabia where Yara are providing the license for Ma’aden Phosphate Company (MPC) to operate three independent phosphoric acid trains, each with a capacity of 1460 tpd P2O5.