Other Fertilizers Made From Phosphoric Acid

7 Other Fertilizers Made From Phosphoric Acid 

A group of fertilizers known as ammonium phosphate-sulfates has been popular for many years and is still popular in many areas. The best known grade is 16-20-0, which essentially consists of MAP and ammonium sulfate CAS). One reason for its popularity is that it is relatively nonhygroscopic. Hygroscopidty, as measured by the critical relative humidity (CRH) of some phosphate and nitrogen fertilizers and combinations, is discussed in Chapter 18. 

It is evident that MAP is one of the least hygroscopic of the phosphate materials and that AS is the least hygroscopic of the straight nitrogen materials. When a fertilizer with a higher N P205 ratio than that of DAP (0.4 1.0) is needed, the MAP plus AS combination is the least hygroscopic. 

The process developed by S. A. Cros in Spain is somewhat similar [10]. In both processes, part of the add is sprayed on the bed of material in the rotary granulator 

There are several processes that produce fertilizers containing ammonium phosphate and ammonium nitrate, but most of them are used to produce NPK grades and will be described further under Chapter 16 Compound Fertilizers.  

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Acids made from minerals are inorganic acids or mineral acids. Minerals are things found in nature. They are not plants or animals. These acids, often used to make commercial products, are liquids. Sulfuric acid is one of the most often used chemicals in the United States. We use it to make gasoline, plastics, and many other products. Some gardeners use fertilizer made from nitric acid and phosphoric acid. 

As of 1993—1994, over 70% of sulfuric acid production was not sold as such, but used captively to make other materials. At almost all large fertilizer plants, sulfuric acid is made on site, and by-product steam from these sulfur-burning plants is generally used for concentrating phosphoric acid ia evaporators. Most of the fertilizer plants are located ia Florida, Georgia, Idaho, Louisiana, and North Carolina. In the production of phosphate fertilizers, the primary role of sulfuric acid is to convert phosphate rock to phosphoric acid and soHd calcium sulfates, which are removed by filtration. 

The phosphate manufacturing and phosphate fertilizer industry includes the production of elemental phosphorus, various phosphorus-derived chemicals, phosphate fertilizer chemicals, and other nonfertilizer phosphate chemicals [1-30], Chemicals that are derived from phosphorus include phosphoric acid (dry process), phosphorus pentoxide, phosphorus penta-sulfide, phosphoms trichloride, phosphorus oxychloride, sodium tripolyphosphate, and calcium phosphates [8]. The nonfertilizer phosphate production part of the industry includes defluori-nated phosphate rock, defluorinated phosphoric acid, and sodium phosphate salts. The phosphate fertilizer segment of the industry produces the primary phosphorus nutrient source for the agricultural industry and for other applications of chemical fertilization. Many of these fertilizer products are toxic to aquatic life at certain levels of concentration, and many are also hazardous to human life and health when contact is made in a concentrated form. 

Poorly crystalline or amorphous Phosphorite sediments made from the hard remains of marine organisms are the principal commercial source of phosphates, although Apatites are also mined. Treatment of phosphate minerals with sulfuric acid yields superphosphate fertilizer, a mixture of Ca(H2P04)2, H3PO4 and CaS04. Phosphoric acid treatment gives triple superphosphate , rich in Ca(H2P04)2. Other soluble fertilizers such as ammonium phosphates are obtained from these products. 

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