High-magnesium ammonium polyphosphate solutions
AssigneeAllied Chemical Corporation
InventorsWilliam Percy Moore, James Earl Sansing
Life of this patent
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Abstract
A stable ammonium polyphosphate fertilizer solution having a relatively high amount of magnesium is prepared by mixing aqueous ammonia with wet-process superphosphoric acid in a reaction zone to give a P.sub.2 O.sub.5 /N weight ratio within the range 3.6-4.0. The temperature of the reaction mixture is preferably maintained at about 50.degree.-70.degree.C. but the product solution should be cooled to about 25.degree.-35.degree.C. prior to storage. The product solution shows relatively low corrosion toward carbon steel storage tanks; however, to further reduce corrosion, the solution is preferably stored under a layer of liquid paraffin hydrocarbons.
Claims2
A process for producing and storing stable ammonium polyphosphate solutions containing at least 0.35% by weight MgO, comprising:
- a. mixing 24-40% by weight aqueous ammonia with superphosphoric acid containing 66-76% by weight P.sub.2 O.sub.5 and 0.7-2.0% by weight MgO to give a reaction solution having a P.sub.2 O.sub.5 /N weight ratio of 3.6-4.0 and a pH in the range 5.0-5.7;
- b. maintaining the temperature of the reaction at 50.degree.-100.degree.C.;
- c. cooling said reaction solution after mixing to a temperature of 25.degree.-35.degree.C.;
- and
- d. storing said solution at 25.degree.-35.degree.C. in a carbon steel tank, under a layer of liquid paraffin hydrocarbon having a boiling point of 150.degree.-300.degree.C., and at pH 5.0-5.7, whereby the solution remains stable and does not precipitate solids for at least 250 days, and shows a corrosion rate in said carbon steel tank of less than 1.4 mils per year, said corrosion rate being measured below the air-liquid interface of the solution.
Dependencies are inferred from the claim text.