The invention relates to a method for the industrial preparation of phosphoric acid from an aqueous suspension comprising water and particles of at least one phosphate material dispersed in the presence of at least one additive of the anionic polymer type. Phosphoric acid is obtained by treating this suspension with at least one strong acid. The polymer is obtained by polymerization reaction of at least one acid selected from acrylic acid, methacrylic acid and salts thereof.

The invention relates to the use of this anionic polymer as well as the method for improving the rheology of the suspension and the hydrodynamics of the reaction medium in which the reactions for the manufacture of phosphoric acid take place.

The invention relates to a process for the production of phosphoric acid, phosphoric acid obtainable by the process, the production of ammonium phosphate salts, and to the use of ammonium salts. A process for the production of phosphoric acid, comprising: i) reacting a phosphorus-containing material with an acid, without organic solvent, thereby forming a reaction mixture comprising phosphoric acid, wherein said acid has a pKa of 3.5 or lower, and ii) extracting phosphoric acid from the reaction mixture by adding organic solvent to the reaction mixture, thereby forming a phosphoric acid solution, wherein 20 wt. % or less of free water is added to the reaction mixture, based on the total weight of the reaction mixture, and the phosphorus-containing material comprises secondary raw material comprising phosphate.

The invention relates to a process for the production of phosphoric acid, phosphoric acid obtainable by the process, the production of ammonium phosphate salts, and to the use of ammonium salts. A process for the production of phosphoric acid, comprising: i) reacting a phosphorus-containing material with an acid, without organic solvent, thereby forming a reaction mixture comprising phosphoric acid, wherein said acid has a pKa of 3.5 or lower, and ii) extracting phosphoric acid from the reaction mixture by adding organic solvent to the reaction mixture, thereby forming a phosphoric acid solution, wherein 20 wt. % or less of free water is added to the reaction mixture, based on the total weight of the reaction mixture, and the phosphorus-containing material comprises secondary raw material comprising phosphate.

Processes for inhibiting scale produced during wet process phosphoric acid production by adding a scale inhibiting amount of a reagent having at least one amine portion including at least one primary amine, and at least one hydrocarbyl portion having an insolubilizing group attached thereto to at least one stage of a wet process phosphoric acid production process are provided herein.

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.

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.

Process of acid attack with sulphuric acid of a phosphate source comprising calcium or not comprising calcium for a predetermined time period ranging from 20 to 180 minutes in the conditions wherein the molar ratio of sulphate from the sulphuric acid and possibly from the phosphate source to the calcium present in the phosphate source ranges from 0.6 to 0.8, and the content in P.sub.2O.sub.5 in the attack tank is of less than 6%.

Embodiments described herein provide systems and methods for a phosphate processing system with integrated sub-systems, such as a phosphoric acid plant, precipitation system, crystallizer system, rinsing system, granulation system, pond water system, organics removal system, and/or exhaust treatment system. Such sub-systems can be integrated with each other by using one or more output streams from one or more sub-systems as one or more input streams for one or more sub-systems. In some embodiments, the phosphate processing system can produce phosphoric acid, struvite containing fertilizer, fertilizer using recycled struvite, magnesium or fluoride containing compositions using recycled magnesium or fluoride, and other components using phosphoric acid collected from a phosphoric acid and gypsum composition or using sludge collected from a waste stream, for example.

A method for chemical processing of sewage sludge ash comprises dissolving a start material, emanating from sewage sludge ash, in an acid comprising hydrochloric acid. The start material comprising at least silicon and iron compounds. Undissolved residues are separated, whereby a leachate remains. The amount of colloidal silica in the dissolved sewage sludge ash is controlled. At least one of iron and phosphorus is extracted from the leachate by liquid-liquid extraction with an organic solvent. At least a part of a raffinate at least partly depleted in at least one of iron and phosphorus originating from the step of extracting at least one of iron and phosphorus is recirculated for dissolving the start material, emanating from sewage sludge ash. The recirculated part of the raffinate at least partly depleted in at least one of iron and phosphorus comprises chloride ions.

A source of phosphate for agriculture and food industry comprises a phosphate salt in solid form of formula M.sub.n(HPO4)y.zH2O in which M is Na, K, NH4, n=2, and y=1; or M is Ca, n=1, y=1; or M is Al or Fe, n=2, y=3; and in which z is 0, 1 or 2, wherein said phosphate salt has a phosphate content expressed as a P2O5 content of between 30 and 50% by weight of the phosphate salt, and it has a cadmium content lower than 0.40 ppm.