Abstract SYMPHOS 2011

phosphate recovery will be determined and the nine processes mentioned will be ranked by their economic
efficiency.
Also, various other factors will be taken into account to determine when one process will be preferred against
another. These factors include:
• Availability, characteristic, and price of raw materials
• Cost of utilities
• Transportation cost
• Product quality
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THE ULITILIZATION OF THE RAFFINATES FROM THE PHOSPHORIC ACIDS IN
THE PRODUCTION OF “ECONOMICALLY VIABLE COMMERCIAL FERTILIZERS.”
John Sinden
JSA LTDA, Santos / BRAZIL
PH-O-09
SUMMARY
In general terms the chemical quality of the phosphate rock concentrates are falling and this has a “knock on” effect
on the chemical quality of the resulting phosphoric acid.
The reductions in chemical quality are not uniform across the commercially available phosphate rock concentrates.
Few if any of the sedimentary phosphates do not suffer from this phenomenon!
When the author first started to work with the phosphate rocks, in the 1960’s, both OCP and “Phosrock” – representing
the North American suppliers, mainly Central Florida were offering the option of the grades “75/77 BPL”
- = 34.3 – 35.2% P 2 O 5 and as the “Standard grade 73/75 BPL = 33.4 – 34.3% P 2 O 5 !
Today, IFA data for 2008 shows that the majority of the Central Florida production was in the range of 66/70 BPL -=
30.2 – 32.0% P 2 O 5 and with a significant percentage below 30.2%! Even the OCP grades have declined, leaving out
the Boucraa data, the majority of the production in 2008 was 70/72 BPL -= 32. 0 – 32.9% P 2 O 5 .
This lower grade of phosphate rock results in a more contaminated – less pure phosphoric acid. At the same time
the market is requesting purer phosphate products mainly for non fertilizer applications. To be able to produce
these purer products there are various processes that concentrate the majority of the impurities into one fraction of
the feed, which is called “Raffinate” while generating a mainstream of purified acid.
There several different types of purified acids and consequently there are different types of raffinates. Such as
produced from the “Super phosphoric acid – SPA” which is mainly composed of Magnesium Pyrophosphate. The
raffinates from the Technical grade and Purified Phosphoric Acids contain high levels of metal ions which are normally
in present in the form of non available phosphates.
In today’s world of Sustainability of natural resources in general and phosphates specifically these raffinates need
to be converted/returned to an available form as a commercially viable fertilizers.
The ways that the raffinates can be and are processed depends what are the levels of impurities. This in turn is
directly related to the ratio of “Purified product: Raffinate”
The presentation will show examples of the viable and economic production of fertilizers from different type of
raffinates.