Production of Ammonium Phosphates

DAP is a white, crystalline compound that is completely soluble in water and, hence is 100% available to plants. MAP is a white, crystalline material that is completely soluble in water. In contrast to DAP (that makes slight alkaline solutions), MAP gives acid solutions with a pH of about 4.5. As in DAP all of the phosphate is available since it is completely water-soluble. 

A caking inhibitor for both MAP and DAP is described in US Patent 5,578,107. The inhibitor is sodium sulfate, and it is effective at concentrations between 0.5% and 1.0%. 

In 4Q02 ammonium phosphate capacity in the United States was 9,705,000 tons per year of DAP and MAP. Approximately 70% of the product is DAP. Demand is summarized in the following table239  

Note Demand equals production plus imports minus exports 

Total DAP/MAP demand has remained between 4.0 and 4.5 million tons since the early 1990 s. Demand declined by 3% in 2001, but is expected to recover in 2002 due to an increase in com plantings. Demand should remain near this level or increase slightly in the medium term due to the 2002 Farm Bill in the United States. This bill will support crop prices near 2002 levels through favorable loan rates. Ammonium phosphate use declined at a rate of 15% from 1996 through 2001. It is expected to grow at a rate of 3% from 2002 through 2005239. 

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Mixed fertilizers contain two or more of the elements nitrogen, phosphorus, and potassium (NPK), which are essential for good plant growth and high crop yields. This subsection briefly addresses the production of ammonium phosphates... 

Drying and cooling the products of ammonium phosphate production are conventionally achieved in a rotary drum, and a means must be provided to remove the dust particles from the air streams to be exhausted to the atmosphere. At the Minnesota plant, a high-efficiency dry cyclone recovery system followed by a wet scrubber was designed. In this way, material recovered from the dry collector (and recycled to the process) pays for the dry system and minimizes the load and disposal problem in the wet scrubber, because it eliminates the need for a system to recover the wet waste material that is discharged to the gypsum disposal pond for settling. 

There has been a trend toward the production of ammonium phosphates in powder form, Concentrated phosphoric acid is neutralized under pressure, and the heat of neutralization is used to remove the water in a spray tower. The powdered product then is collected at the bottom of the tower. Ammonium nitrate/ammonium phosphate combination products can be obtained either by neutralizing mixed nitric acid and phosphoric acid, or by the addition of ammonium phosphate to an ammonium nitrate melt. 

Diammonium Phosphate (DAP). Ammonium phosphates did not come on the fertilizer scene in significant quantities until the early 1960s however, they have rapidly become the leading form of phosphate fertilizer in the world. Almost all new phosphate fertilizer complexes built in recent years, and those planned, are for the production of ammonium phosphate as the major product. In 1960, world production of ammonium phosphates was equivalent to only 0.5 million mt of P205. By 1990 it was up to 15.4 million mt and by 1999 it has reached 16.7 million mt. Ammonium phosphates now provide two-thirds of total world phosphate fertilization. 

Perphosphates of ammonium may be prepared in good yields by electrolysis, but auto-oxidation and -reduction may occur with the production of ammonium phosphate and ammonium nitrate.1... 

Table 2.1-6. Worldwide Production of Ammonium Phosphate Fertilizer in the Period 1980 to 1994 in 10 t/a P2O5.

The production of ammonium phosphate fertilisers is an example of acidic and alkali media neutralisation under commercial plant conditions [1]. During the production of ammonium phosphate, at the liquid ammonium and phosphoric acid reaction stage, a six-section tubular turbulent reactor of diffuser-confusor design is used. The reactor maintains turbulence along its length, with a reactor diameter of 220 mm and confusor diameter of 105 mm the reactor operates in a normal mode at a... 

The United States continues as the world s largest producer of phosphate fertilizers and expanded ammonium phosphate production capacity by 87% between 1975 and 1995 (Figure 3.14). However, maturity of the domestic market has forced U.S. phosphate producers to become more dependent on exports. In 1995, the United States exported more than 10.5 million tonnes of ammonium phosphate these exports accounted for about 63% of the U.S. production of ammonium phosphate. 

Salladay, D. G., and W. H. Paulson. 1984. Development of TVA Pressure Reactor for Production of Ammonium Phosphate, Proceedings of the 34th Annual Fertilizer Round Table Meeting, Baltimore, MD, U.S.A. 

The routes by which mineral phosphates are processed into finished fertilizers are outlined in Eigure 7. World and U.S. trends in the types of products produced are shown in Eigures 8 and 9, respectively. Most notable in both instances is the large, steady increase in the importance of monoammonium and diammonium phosphates as finished phosphate fertilizers at the expense of ordinary superphosphate, and to some extent at the expense of triple superphosphate. In the United States, about 65% of the total phosphate appHed is now in the form of granular ammonium phosphates, and additional amounts of ammonium phosphates are appHed as integral parts of granulated mixtures and fluid fertilizers. 

Production of nitric phosphates is not expected to expand rapidly ia the near future because the primary phosphate exporters, especially ia North Africa and the United States, have moved to ship upgraded materials, wet-process acid, and ammonium phosphates, ia preference to phosphate rock. The abundant supply of these materials should keep suppHers ia a strong competitive position for at least the short-range future. Moreover, the developiag countries, where nitric phosphates would seem to be appealing for most crops except rice, have already strongly committed to production of urea, a material that blends compatibly with sulfur-based phosphates but not with nitrates. 

Ammonia is consumed in the manufacture of ammonium phosphates and ammonium sulfate by reaction with phosphoric acid and sulfuric acid, respectively. The phosphates may contain ortho- and polyphosphate values. Ammonium sulfate is also a by-product from other ammonia-using industries such as caprolactam (qv) and hydrogen cyanide (see Cyanides). 

Pla.tinum, Platinum plating has found appHcation in the production of platinised titanium, niobium, or tantalum anodes which are used as insoluble anodes in many other plating solutions (see Metalanodes). Plating solutions were often based on platinum "P" salt, which is diamminedinitroplatiniim (IT). A dinitroplatinite sulfate—sulfuric acid bath has been used to plate direcdy onto titanium (129). This bath contains 5 g/L of the platinum salt, pH adjusted to 2.0 with sulfuric acid. The bath is operated at 40°C at 10—100 A/m. Other baths based on chloroplatinic acid have been used in both acid and alkaline formulations the acid bath uses 20 g/L of the platinum salt and 300 g/L hydrochloric acid at 65° C and 10—200 A/m. The alkaline bath uses 10 g/L of the platinum salt, 60 g/L of ammonium phosphate and ammonium hydroxide to give a pH of 2.5—9.0. The alkaline bath can be plated directly onto nickel-base alloys acid baths require a gold strike on most metals. 

The degradation of the poly(phosphazenes) is very well understood, with the production of ethanol, phosphate, ammonium salts, and the pendant groups (Andrianov and Payne 1998). When the pendant group is an amino acid, all of the degradation... 

Of the processes based on modification of the conventional route, only Stamicarbon s hydroxylamine phosphate oxime (HPO) process completely avoid all production of ammonium sulfate before the Beckmann rearrangement. The steps in the HPO process are listed below and shown in Figure 21.146, 264 ... 

Nitric Phosphate. Fertilizers that are referred to as nitric phosphate or nitrophos-phate are produced by acidulation of phosphate rock with nitric acid or with mixtures of nitric and sulfuric or phosphoric acids. The primary advantage of nitric phosphate processes is that no sulfur or less sulfur is required as compared with superphosphates or ammonium phosphates this is particularly important during a shortage of sulfur, or in locations where sulfur must be shipped long distances. A variety of processes and equipment have been used in Europe since the late 1930s.3,12 Also there are a number of plants in Central and South America and in Asia. The production of nitric phosphates is complex. Simple substitution of nitric acid in a superphosphate-type acid-rock reaction is not feasible because (1) decomposition of the nitric acid would occur and cause noxious fumes and loss of nitrogen and (2) the product would be extremely hygroscopic and unstable. 

Defluorinated Phosphate Rock. There is substantial production of defluorinated phosphate rock for fertilizer use in Japan (about 100,000 mt/year). Ground, high-grade rock is mixed with small proportions of sodium carbonate or sulfate and wet-process acid. The mixture is calcined at a temperature of 1350°C in an oil-fired rotary kiln 45.0 m in length and 2.7 m in diameter. The product contains 38-42 percent P205 of which more than 90 percent is soluble in neutral ammonium nitrate solution and is an effective fertilizer on acid soils. During the production of defluorinated phosphate rock, substantially all fluorine is driven off. Sodium bifluoride (NaHF2) is recovered as a byproduct. A similar product is made in the United States, but it is mainly used for animal feed supplement. 

The Romans first treated wood for fire retar-dancy in the first century a.d. They used solutions of alum and vinegar to protect their boats against fire. In 1820, Gay-Lussac advocated the use of ammonium phosphates and borax for treating cellulosic material. Many of the promising inorganic chemicals used today were identified between 1800 and 1870. Since then, the development of fire retardants for wood has accelerated. Commercially treated wood became available after the U.S. Navy (1895) specified its use in ship construction, and New York City (1899) required its use in buildings over 12 stories tall. Production reached over 65 million board feet in 1943, but by 1964 only 32 million board feet was treated annually.35... 

The production of triple superpho.sphate with a P2O5-content greater than 40% and biologically more available phosphorus reached a peak in 1984 and has declined 30% since then. The worldwide capacity for triple superphosphate is considerably underutilized. Part of the spare capacity can be utilized for the manufacture of ammonium phosphate. The world production by region in 1990 is given in Table 2.5-5. 

To achieve these aims the manufacturing steps neutralization of phosphoric acid with ammonia in an exothermic reaction and production of solid materials (e.g. by granulation or prilling) are linked with one another. Several of the many proces.ses for the manufacture of ammonium phosphates will be discussed below. 

In the TVA granulation process, slurries of ammonium phosphates, with a deficit or excess of ammonia with respect to mono-ammonium phosphate, are produced by the reaction of ammonia with phosphoric acid. These slurries are granulated by adding the deficient quantities of acid or ammonia necessary for a stoichiometric product and recycling the fine fraction. The granulate is then dried in, for example, rotary dryers, a process which requires considerable energy. 

The manufacture of ammonium phosphates can be combined with the production of mixed fertilizers e.g. ammonium phosphate with ammonium sulfate (partial substitution of sulfuric acid with phosphoric acid) or ammonium nitrate. The ammonium phosphates can also be converted into mixed fertilizers during granulation by adding potassium salts, urea etc. 

Most of the phosphoric acid production in the U.S., about 85%, is consumed by fertilizer manufacturers, mostly for preparation of ammonium phosphates and triple superphosphate (Chap. 11). This consumption picture may be slightly distorted since the U.S. is also a substantial exporter of phosphoric acid. 

Variables in the production of tributyl phosphate have been discussed. In the presence of relatively large amounts (5—15 molar equivalents) ofcaesium fluoride or quaternary ammonium fluorides, 2,2,2-trichloroethyl phosphate esters readily trans-esterify with alcohols the sequential replacement of trichloroethyl groups becomes slower, so allowing the preparation of mixed (including cyclic) trialkyl phosphate esters, with the exception of those from t-butyl alcohol. ... 

The HPO (hydroxylamine phosphate oxime) process, developed byDSMand licensed by Siamicarbon, totally eliminates the production of ammonium sulfate, both in the production of hydroxylamine itself and in die oxime production stage. It consists of the catalytic hydrogenation of the nitrate ions resulting from the oxidation of ammonia to hydroxylamine ions in a solution buffered by phosphates. The nitrate reduction reaction is as follows ... 

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