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AssigneeIMC-Agrico Company
InventorsKenneth J. Jardine, Vaughn V. Astley
Estimating the term…
A process for the preparation of granular fertilizer grade DAP (a product composed of ammonium phosphates, principally diammonium phosphate, resulting from the ammoniation of phosphoric acid, as defined in Official Publication No. 52 of the Association of American Plant Food Officials, dated 1999) comprising partially preneutralizing orthophosphoric acid with ammonia, completing the ammoniation of the orthophosphoric acid with ammonia in a rotary ammoniator-granulator to provide granular DAP, sizing the granular DAP to provide the granular DAP product, reducing the particle size of the oversized granular DAP, and recycling the undersized granular DAP and the sized-reduced oversized granular DAP to the ammoniator-granulator. The ammoniacal nitrogen concentration of the granular DAP recycle, hence the granular DAP product, is enhanced by subjecting the finely-divided recycled granular DAP to anhydrous gaseous ammonia which is at a super atmospheric pressure and which is at a temperature sufficient to maintain said anhydrous ammonia in the gaseous state. The increase in the ammoniacal nitrogen concentration is a function of the absolute ammonia pressure, the initial moisture content of the granular DAP recycle, and the contact time of the ammonium with the granular DAP recycle.
A process for enhancing the ammoniacal nitrogen concentration of DAP, comprising subjecting said DAP, which is in finely divided form and which due to the impurities contained in the phosphoric acid used to produce it, contains less than 18.0 percent by weight of ammoniacal nitrogen, but which contains sufficient excess phosphate to compensate for the dilution effect that would be created by the quantity of ammonia necessary to raise the ammoniacal nitrogen concentration to at least 18.0 percent by weight and still contain at least 46.0 percent by weight of phosphate, as P2O5, to anhydrous gaseous ammonia which is at super atmospheric pressure and which is at a temperature sufficient to maintain said ammonia in the gaseous state, such that a quantity of triammonium phosphate (TAP) is incorporated into the DAP that is sufficient to raise the total ammoniacal nitrogen concentration of the DAP to at least 18.0 percent by weight, the quantity of triammonium phosphate formed and the increase in the ammoniacal concentration being a function of the absolute ammonia pressure, the initial moisture content of said DAP and the contact time of the gaseous ammonia with said DAP.
In a process for the preparation of granular fertilizer grade DAP product comprising partially preneutralizing orthophosphoric acid with ammonia, completing the ammoniation of the orthophosphoric acid with ammonia in a rotary ammoniator-granulator to provide granular DAP, sizing the granular DAP to provide the granular DAP product, reducing the particle size of the oversized granular DAP, and recycling the undersized granular DAP and size-reduced oversized granular DAP to the ammoniator-granulator, wherein, due to impurities contained in the orthophosphoric acid, it is not possible to achieve an ammoniacal nitrogen concentration in the final product of at least 18.0 percent by weight, while still maintaining a phosphate concentration, as P2O5, of at least 46.0 percent by weight, the process improvement comprising enhancing the ammoniacal nitrogen content of the granular DAP recycle, hence the granular DAP product, by reacting the finely-divided DAP recycle with anhydrous gaseous ammonia which is at a super atmospheric pressure and which is at a temperature sufficient to maintain said anhydrous ammonia in the gaseous state such that a quantity of triammonium phosphate (TAP) sufficient to raise the total ammoniacal nitrogen concentration of the DAP product to at least 18.0 percent by weight is formed, whereby the quantity of triammonium phosphate formed and, hence, the increase in the ammoniacal nitrogen concentration is a function of the absolute ammonia pressure, the initial moisture content of the granular DAP recycle, and the contact time of the ammonia with the granular DAP recycle.
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