Potassium nitrate and phosphates - potassium nitrate (KNO3) and mono-potassium phosphate (MKP, KH2PO4) - are both manufactured today as commercial fertilisers, but the idea here is to make two improvements. The present proposal is to upgrade the well-known Nitrophos process - treatment of phosphate rock with nitric acid - so as to produce potassium nitrate and a liquid KP concentrate.
The nitric acid - actually NO gases from oxidation of ammonia, which can be used directly - does a double job; to acidulate phosphate rock, and to produce potassium nitrate. Meanwhile, the KP is produced in the form of a concentrated solution, pH 7 or more, nearer to di-phosphate than to mono-phosphate. Liquid concentrates which can be obtained are, for example:
1) K2HPO4 57%, KH2PO4 8%, urea 5.5% at 25ºC; pH 8.9
2) 2.57 - 27.4 - 33.6 = 63.6% NPK
3) Or...