Imi Tami Institute for Research and Development Ltd.

Imi Tami Insitute for Research and Development

Eyal Ginzberg

Ron Frim

Eyal Barnea

Gideon Shikolsky

Gideon Friedman

Cornelis Petrus Langeveld

Aharon Weissman

Yelena Gorelik

Michael Bonan

Eyal Yehihel Vultz

Dorit Perle

Akiva Mozes

Basam Masri

Hugo Keselman

Ezrah Hanuka

A process for producing KNO3 from polyhalite to is disclosed. In a preferred embodiment, the process comprises steps of (a) contacting polyhalite with HNO3; (b) adding Ca(OH)2 to the solution, thereby precipitating as CaSO4 at least part of the sulfate present in said solution; (c) precipitating as Mg(OH)2 at least part of the Mg2+ remaining in said solution by further addition of Ca(OH)2 to the remaining solution; (d) concentrating the solution, thereby precipitating as a sulfate compound at least part of the sulfate remaining in solution; (e) separating at least part of the NaCl from the solution remaining; and (f) crystallizing as solid KNO3 at least part of the K+ and NO3-contained in the solution. The process enables direct conversion of polyhalite to KNO3 of purity exceeding 98.5% and that is essentially free of magnesium and sulfate impurities.

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A cement mix for preparation of a magnesium silico-phosphate cement (MSPC) with an altered hardening rate is provided. The cement mix comprises on the order of 1% of an [MF]salt or acid. Upon addition of water, the mix produces a final set cement that has similar physical properties to those of a cement prepared from a mix lacking the additive, but with a significantly altered setting time. In some embodiments of the invention, the additive is provided in the form of a coating for the MgO component of the mix. In preferred embodiments, HTiF, NaTiFand/or KTiFare used as retarders, while KAlFis used as an accelerant. Other embodiments use M'MFcompounds wherein M&#x2032; is an alkali metal, an alkaline earth metal, or H, and M is chosen from inter alia Ti (n=2), Zr (n=2), P (n=1), Al (n=3), and Sb (n=1).

Cement mixes containing additives for altering the hardening rate of chemically bonded silico-phosphate cements and methods therefor

A method for the production of KNOfrom polyhalite is provided. The method comprises steps of decomposing said polyhalite into syngenite, gypsum, and soluble components, treating the solid decomposition products sequentially with HNOand Ca basic compound, precipitating the CaSOthus formed, and crystallizing the KNOfrom the solution remaining. The method recovers up to 75% of the potassium present in the raw polyhalite as KNOand substantially all of the remainder as a potassium magnesium sulfate salt.

Process for production of commercial quality potassium nitrate from polyhalite

A method is provided for advantageously altering the rate of hardening of a magnesium silico-phosphate cement (MSPC). Addition of on the order of 1% of an [MF]salt or acid to an MSPC, obtained by adding the salt or acid either directly to the dry mix or to the water used to effect hydraulic hardening of the cement, significantly alters the hardening rate without adversely affecting the physical properties of the final set cement. In preferred embodiments, NaTiFand/or KTiFare used as retardants, while KAlFis used as an accelerant. Other embodiments use M'-MFcompounds wherein M&#x2032; is an alkali metal, an alkaline earth metal, or H, and M is chosen from inter alia Ti (n=2), Zr (n=2), Si (n=2), P (n=1), Al (n=3), and Sb (n=1).

Additives for altering the hardening rate of chemically bonded silico-phosphate cements and method therefor

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Zikhron-Yaakov, Israel

Eyal Ginzberg