This disclosure relates to a method for the preparation of calcium monohydrogen phosphate comprising an etching in an aqueous medium, during a predetermined time period, a source of phosphate with an acid with formation of a pulp comprising an aqueous phase containing calcium phosphate in solution and a solid phase containing impurities, a first separation between said aqueous phase and said solid phase, during a predetermined time period, a neutralization of said aqueous phase at a sufficient pH to obtain a precipitation of said calcium monohydrogen phosphate, a second separation between said aqueous medium and said calcium monohydrogen phosphate, characterized in that said predetermined time period of said step a) of digestion is greater than that of said step b).

This disclosure relates to a method for the preparation of calcium monohydrogen phosphate comprising an etching in an aqueous medium, during a predetermined time period, a source of phosphate with an acid with formation of a pulp comprising an aqueous phase containing calcium phosphate in solution and a solid phase containing impurities, a first separation between said aqueous phase and said solid phase, during a predetermined time period, a neutralization of said aqueous phase at a sufficient pH to obtain a precipitation of said calcium monohydrogen phosphate, a second separation between said aqueous medium and said calcium monohydrogen phosphate, characterized in that said predetermined time period of said step a) of digestion is greater than that of said step b).

This present invention disclosure relates to a method for the preparation of calcium monohydrogen phosphate comprising an etching in an aqueous medium, during a predetermined time period, of a phosphate source with an acid with formation of a pulp comprising an aqueous phase containing calcium phosphate in solution and a solid phase containing impurities, a first separation between said aqueous phase and said solid phase, during a predetermined time period, a neutralization of said aqueous phase at a sufficient pH to obtain a precipitation of said calcium monohydrogen phosphate, a second separation between said aqueous medium and said calcium monohydrogen phosphate, characterized in that said first separation of said step b) is carried out at a filtration rate of at least 0.1 ton of P.sub.2O.sub.5/P/m.sup.2/day.

A method for reducing formation of scale in phosphoric acid production is provided herein. Phosphate-containing ore is combined with an acid to form an acidic slurry and the acidic slurry is processed to form an acidic stream. The method includes providing a scale inhibitor including an inorganic phosphate. The method further includes combining the scale inhibitor and at least one of the phosphate-containing ore, the acidic slurry, and the acidic stream, to reduce the formation of scale. A system for phosphoric acid production exhibiting a reduced formation of scale is also provided herein. The system includes a substrate having a surface in contact with at least one of the phosphate-containing ore, the acidic slurry formed from the phosphate-containing ore and the acid, and the acidic stream formed from the acidic slurry. The system including the scale inhibitor exhibits a reduced formation of scale on the surface.

Processes for inhibiting scale produced during wet process phosphoric acid production by adding a scale-inhibiting amount of a reagent having a primary amine-containing polymer to at least one stage of a wet process phosphoric acid production process are provided herein, wherein said primary amine-containing polymer includes one or more organic moieties that reduce the polymer's solubility in an aqueous environment as compared to its native form, thereby reducing or preventing scale in the wet process phosphoric acid production process.

Processes for inhibiting scale produced during wet process phosphoric acid production by adding a scale-inhibiting amount of a reagent having a primary amine-containing polymer to at least one stage of a wet process phosphoric acid production process are provided herein, wherein said primary amine-containing polymer includes one or more organic moieties that reduce the polymer's solubility in an aqueous environment as compared to its native form, thereby reducing or preventing scale in the wet process phosphoric acid production process.

The present invention relates to a composition containing an anionic surfactant based on an alkali salt of sulfosuccinic acid dialkylester to promote the obtention of an inverse microemulsion which is used as foam control composition in a phosphoric acid production medium. The present invention also discloses a process to produce said composition by stirring the components of such a composition to obtain a microemulsion. The invention also aims at a method for controlling foam during the production of phosphoric acid by wet process, avoiding its formation or decreasing its amount.

The present invention concerns a method for recovering phosphorus by thermochemical reaction of a phosphorus-containing material such as an alternative fuel, for example, in the presence of calcium-containing particles in a moving bed reactor and subsequent separation of fines enriched with phosphorus from the moving bed reactor. Furthermore, the present invention concerns the use of a recyclable material obtained by the method as a fertilizer or fertilizer additive.

The present invention concerns a method for recovering phosphorus by thermochemical reaction of a phosphorus-containing material such as an alternative fuel, for example, in the presence of calcium-containing particles in a moving bed reactor and subsequent separation of fines enriched with phosphorus from the moving bed reactor. Furthermore, the present invention concerns the use of a recyclable material obtained by the method as a fertilizer or fertilizer additive.

Provided is a method for producing phosphoric acid and at the same time obtaining alpha-hemihydrate gypsum including: adding a phosphate rock powder and a part of dilute sulfuric acid into an extraction tank, carrying out an extraction reaction on same, separating a clear liquid from the obtained mixed slurry, sending the clear liquid, as a finished product phosphoric acid, into an acid storeroom, and transferring a separated solid, together with the rest mixed slurry, into a crystal transformation tank; and adding sulfuric acid and a crystal transformation agent into the crystal transformation tank, carrying out a crystal transformation reaction for 1.5-7.5 h at 60? C.-130? C., and solid-liquid separating the obtained mixed acid slurry, wherein the solid can be dried into a gypsum powder, or may be not subjected to a drying step and made into gypsum products such as gypsum boards, gypsum building blocks and gypsum members by directly adding water.