Tennessee Valley Authority

Kenneth E McGill

Horace C Mann, Jr

Eugene B Wright, Jr

Frank P Achorn

Johnny R Gamble

An improved process for the production of granular ammonium polyphosphate fertilizer of a nominal 11-56-0 grade resulting from the pressure ammoniation of phosphoric acid without the use of a preneutralizer and using a specially designed pipe reactor to effect coating and granulation of an anhydrous melt onto cascading granules of ammonium polyphosphate with polyphosphate contents thereof ranging from about 15 percent to 30 percent of the total P.sub.2 O.sub.5. The instant invention defines the operating parameters which allow for the practice of a process wherein there is essentially no degradation in the amount of P.sub.2 O.sub.5 values produced as polyphosphate in the melt as said melt is further processed in the remaining steps therein through the step of product recovery, i.e., we have discovered the parameters for operating a process wherein essentially no hydrolysis of the polyphosphate P.sub.2 O.sub.5 values in the melt occurs. In addition, because of the low moisture content of the melt as produced and provisions for the removal of that remaining in said melt as it is processed in the granulator, the requirement for the dryer that is normally required and used in most conventional processes is eliminated. The product is physically and chemically structured so that it is harder than similar grade granules made in accordance with the dictates and teachings of conventional processes. The product resulting from practice of the instant invention contains more polyphosphate than similar products made by ammoniation of wet-process orthophosphoric acids. The high quality product resulting from the practice of the preferred embodiments of the instant invention is dust-free, not agglomerated, and well suited for direct use in bulk blends or as starting materials for the production of high-quality suspension fertilizers.

Production of granular ammonium polyphosphate from wet-process

The process allows essentially all of the nitrogen and P.sub.2 O.sub.5 values in the treated black ammonium polyphosphate liquid to be recovered in the form of valuable clarified product. In the process, a heel of black liquid fertilizer is first clarified by a prior-art procedure using flocculants. The improvement over the prior art picks up with the byproduct tops which is then diluted with the water of formulation required to dissolve additional amounts of ammonium polyphosphate melt. This diluted liquid is filtered, the filter cake containing upwards of 99 percent of the undesirable black carbonaceous material is discarded, and the clear filtrate, which contains essentially all of the nitrogen and P.sub.2 O.sub.5 originally in the tops, is then used in lieu of the prior-art water of formulation to dissolve additional ammonium polyphosphate melt to produce more black ammonium polyphosphate liquid.

Clarification of black ammonium polyphosphate liquids--recycling of

A process for the production of fluid fertilizers (suspensions and/or solution type) made from merchant-grade phosphoric acid (50-58 percent P.sub.2 O.sub.5), sulfuric acid, liquid anhydrous ammonia, and water, wherein liquid ammonia is heated in heat exchange means juxtaposed hot fertilizer product to form gaseous ammonia, which gaseous ammonia, along with phosphoric acid and sulfuric acid, is fed to a pipe-cross reactor wherein a melt of ammonium polyphosphate sulfate is formed, which melt is subsequently mixed with cooled recycled product to produce a fluid fertilizer with N:P.sub.2 O.sub.5 weight ratios ranging from about 0.3 to 1, which contains from about 10 to 60 percent of its P.sub.2 O.sub.5 values in the form of polyphosphates and 3 to 8 percent by weight sulfur. About 45 percent of the P.sub.2 O.sub.5 as polyphosphate is easily attainable in the product with ambient acid feed temperatures, i.e., about 50.degree. F. to 100.degree. F., versus prior-art teachings of only about 15 percent poly formation with preheat of the feed acids. It is a solution when it is produced, and when diluted with 10 percent by weight water, it can be stored at 40.degree. F. without the formation of troublesome crystals. When gelling clay is added, it stores well as a suspension and remains fluid at temperatures as low as -25.degree. F.

Ammonium polyphosphate sulfate fertilizers from wet-process phosphoric

Clarification of black ammonium polyphosphate liquids recycling of

Particulate carbonaceous matter in ammonium polyphosphate liquid made from impure wet-process phosphoric acid is removed batchwise by intimately mixing the liquid with a combination of selected organic flocculating agents and then allowing the mixture to separate. The particulate carbonaceous matter floats and the clarified liquid is withdrawn from the bottom of the separation vessel. The particulate carbonaceous matter, a minor portion of the input ammonium polyphosphate liquid, and the flocculating agents are intimately remixed with fresh black ammonium polyphosphate liquid to allow reuse of flocculant not combined with the original particulate carbonaceous material. The flocculants may be reused as many as five times. The particulate carbonaceous matter, the inactive flocculant, and a minor portion of the input ammonium polyphosphate liquid are then processed into fluid or solid fertilizers. In some instances, more flocculant is added to the mixing vessel.

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Sheffield, AL, United States of America

Kenneth E McGill