A method for the recovery or ultra-purification of orthophosphoric acid rich feed streams in the absence of solvent crystallization and avoiding multiple discontinuous layer melt crystallization steps, said method comprising the steps of: a) addition of water to an orthophosphoric acid rich stream to produce an orthophosphoric acid rich stream with an orthophosphoric acid content between 80% and 90% by weight acid and preferably between 85% and 90% by weight acid and a total impurity content other than orthophosphoric acid and water of < 1%, b) cooling the orthophosphoric acid rich stream below its freezing point to form hemi-hydrate crystals, resulting in a mixed phase slurry of mother liquor and suspended crystals, c) cooling said slurry to create a volume with a crystal content of between 15% and 50% by weight of the hemi-hydrate crystal wherein the available surface for crystal growth is not less than 5,000 m 2 per m 3 of crystallizer volume, d) holding said slurry in a mixing tank to create a crystal residence time preferably between 15 minutes and 4 hours, more preferably between 30 minutes and 2 hours and most preferably between 30 minutes and 1 hour, e) separating said crystals from the mother liquid in a wash column, f) heating a portion of the hemi-hydrate crystals until they are essentially all melted to form a liquid of the purified acid and water, g) washing the hemi-hydrate crystals in the wash column, wherein the crystals are counter-currently washed by contact with the purified melt of said crystals and no wash is lost but is recrystallized on the supercooled crystals, h) discharging the melted hemi-hydrate crystals as purified orthophosphoric acid and water solution, and i) discharging essentially all other impurities in the separated mother liquor. a) addition of water to an orthophosphoric acid rich stream to produce an orthophosphoric acid rich stream with an orthophosphoric acid content between 80% and 90% by weight acid and preferably between 85% and 90% by weight acid and a total impurity content other than orthophosphoric acid and water of < 1%, b) cooling the orthophosphoric acid rich stream below its freezing point to form hemi-hydrate crystals, resulting in a mixed phase slurry of mother liquor and suspended crystals, c) cooling said slurry to create a volume with a crystal content of between 15% and 50% by weight of the hemi-hydrate crystal wherein the available surface for crystal growth is not less than 5,000 m 2 per m 3 of crystallizer volume, d) holding said slurry in a mixing tank to create a crystal residence time preferably between 15 minutes and 4 hours, more preferably between 30 minutes and 2 hours and most preferably between 30 minutes and 1 hour, e) separating said crystals from the mother liquid in a wash column, f) heating a portion of the hemi-hydrate crystals until they are essentially all melted to form a liquid of the purified acid and water, g) washing the hemi-hydrate crystals in the wash column, wherein the crystals are counter-currently washed by contact with the purified melt of said crystals and no wash is lost but is recrystallized on the supercooled crystals, h) discharging the melted hemi-hydrate crystals as purified orthophosphoric acid and water solution, and i) discharging essentially all other impurities in the separated mother liquor.