Nitric Acid → Calcium nitrate

Temperature

20 °C

303.9 g of phosphonitrate solution obtained by attacking 100 g of Morocco phosphate rock with 228 g of 58% nitric acid, having a content of CaO of 16.62% and of P2O5 of 11.83%, were introduced into a crystallizing vessel. The solution was cooled at a rate of cooling of 12° C/hour, and when the temperature of the solution reached 20° C, a temperature rise from 20° to 24° C was recorded. The solution was then further cooled at the same rate of 12° C/hour until it again reached 20° C. At this instant, into the solution were introduced under stirring 95 g of mother solution with washing acid, coming from the second step of another sample subjected to crystallization, which had a content of P2O5 of 14.94%, and CaO 4.28%, cooling being continued at a rate of 30° C/hour until reaching the temperature of -5° C. The crystal suspension was filtered and centrifuged, obtaining thus 210 g of calcium nitrate crystals having a content of CaO of 20% and of P2O5 of 0.51%, a largest size of 350 microns, minimum size of 110 microns and an average size of 200 microns. In this case the liquid: solid ratio had been of about 1:1.1. By centrifuging, an amount of 110 g of mother solution was also obtained, having a content of CaO of 2.61% and of P2O5 17.45%, the rest of the solution being included in the filtered crystals.

1. temperatureThe solution was cooled at a rate
2. temperatureof cooling of 12° C/hour, and when the temperature of the solution
3. customreached 20° C
4. customfrom 20° to 24° C
5. additionAt this instant, into the solution were introduced
6. washwith washing acid
7. customsubjected to crystallization, which
8. temperature28%, cooling
9. customthe temperature of -5° C
10. filtrationThe crystal suspension was filtered

ORD record

ord-06d07b69ccd949309e294067226d4ed9

Source dataset

uspto-grants-1977_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04008309