Speciality high value fertilisers based on polyhalite

Since starting to extract polyhalite at scale from its UK Boulby mine in 2011, ICL has brought a totally new range of fertilisers to the global market.

The seam of polyhalite being mined by ICL is a very pure (ca.90%) naturally occurring evaporite mineral containing potassium, magnesium and calcium effectively as sulphates in a single crystal structure; it is not a mixture of its constituent nutrients. It also contains valuable micronutrients such as boron, and has a unique extended solubility pattern; it is certified as an organic product and has a very low carbon footprint.

ICL is processing polyhalite in its facilities in Boulby in various physical stages including mining, crushing, screening and compaction with potash. All these processes have been developed and adapted by ICL to handle this new and unique mineral efficiently to high quality standards, enabling the production of fertilisers with a wide range of nutrient contents.

Polyhalite processing in Boulby provides two streams: a crushed and screened 2-4 mm granular fertiliser which is sold into the global market under their brand name Polysulphate™ and a standard material which is used in a new range of products developed by ICL containing various proportions of all six macronutrients (N, P, K, S, Mg and Ca) and some micronutrients. These include a product co-compacted with MOP (ICLPotashpluS^®) and a wide range of multi-nutrient branded granular fertilisers. In addition, polyhalite has been evaluated in various production processes (steam granulation, chemical granulation, spherodiser granulation, pan granulation, prilling, spray-dryer granulation, compaction etc.) and with different raw materials (including urea, ammonium nitrate, MOP, SOP, solid or liquid MAP/DAP, superphosphate etc.).

The production processes for these outputs demonstrate various opportunities, ranging from operational parameters (process stability, throughput etc.) to high quality fertilisers produced in different facilities within and outside ICL, with these fertilisers showing excellent field performance of increased yields and improved crop quality across over 800 trials globally.

The combination of polyhalite with other fertiliser materials and processing using different technologies requires and dictates different approaches, especially with nitrogen-fertilisers. The operational parameters need to be re-set to allow better performance of the facilities, which may be achieved with or without additives to facilitate the production, depending on the required composition formulae.

ICL has also developed processes to include additives offering further added value for crop producers, such as additional microelements, biostimulants etc.

This presentation describes the development of the production processes that have been required during the introduction of this new and untried mineral, polyhalite, which have enabled ICL to produce a range of novel products to a consistently high quality.