method for cleaning kalciumnitrat in solution or melt, isolated from a aufloesen of phosphatgesteinen with salpetersaeure obtained mixture.

摘要

The present invention relates to a method for purifying calcium nitrate melt/solution separated from the mixture obtained by dissolution of rock phosphate with nitric acid. The melt contains fluorine and phosphorus as main contaminants. The mol-ratio phosphorus/fluorine in the crude calcium nitrate melt/solution is adjusted to 3.5P/F0.3, possibly by extra addition of a phosphorus compound, and the mixture is then neutralized by ammonia to pH = 5-6. The precipitate thereby formed is removed while the filtrate, which is a purified nitrate of lime melt, is evaporated and further processed. The purification can be carried out in two stages, with a P/F-ratio in the first stage of 0.3-3 and 1-3.5 in the second stage. Phosphoric acid or a phosphoric acid containing solution is used as phosphorus compound.