Ammonium polyphosphate fertilizer

At the U.S. Forest Products Laboratory, many of the research programs involve fire-retardant-treated wood. This has included extensive basic study of pyrolysis and combustion reactions of wood and its components and the effects of chemical additives on these reactions (15,24-26,28,29,66). A cooperative study (9) with the Division of Chemical Development of the Tennessee Valley Authority, showed the effectiveness of liquid ammonium polyphosphate fertilizers as fire retardants for wood. The commercial use of these products, made from electric furnace superphosphoric acid, has been shown to be economically feasible. Work has been completed by Schaffer (33) on the rate of fire penetration in wood treated with different types of chemicals. Some results of this study are reported elsewhere in this paper. 

Sugama and Allan [5] used calcium aluminates (tricalcium aluminate, C -A, monocalcium aluminate, C A, or calcium dialuminate, C A2) as the cation donors and reacted them with an ammonium polyphosphate fertilizer solution and formed quicksetting cements. The purpose of this study was to develop cements that are not affected by the CO2 environment and are useful as downhole cements in geothermal wells (see Chapter 15). The composition of the fertilizer was 11.1 wt% N as ammonia, 37.0 wt% P2O3, 50.79 wt% water, and the rest trace elements. Differential scanning calorimetry (DSC) showed that the reaction rates of the three minerals are in the decreasing order ... 

Some insoluble oxides become soluble when incorporated in ammonium polyphosphate fertilizers, in practice, the ammonium polyphosphate liquid fertilizers are widely used in some countries, and zinc oxide often is added and dissolved in them. However, solid fertilizers containing ammonium polyphosphate also will convert zinc oxide (or carbonate) to a soluble form. 

UREA-AMMONIUM POLYPHOSPHATE. A fertilizer similar fo urea-ammonium othtrophosphate except that about half the phosphorus is in polyphosphate form, which gives improved sequestering action and solubility. It is excellent for use as a liquid fertilizer. 

Ammonium polyphosphate is one of the most often used phosphoric fertilizers (Corbridge, 1980). It was found to be equally effective when compared with single superphosphate and diammonium phosphate for increasing the yields of wheat and maize and for increasing the available phosphorus content in soil during field experiments (Sharma and Singh, 1998). 

The most popular scheme by which solution-type fertilizers are made from low-conversion, wet-process superphosphoric acid is outlined in Fig. 24.20. The first step is ammoniation of the acid to produce ammonium polyphosphate base solution. By carrying out this ammoniation in a pipe reactor, a temperature of over 200°C is developed, which promotes an increase in polyphosphate content to 65-70 percent of total P2Os in the ammoni-ated acid.39,40 The grade of the resultant base is usually 10-34-0 an 11-37-0 grade can be made, but its storage properties are not as... 

Fig. 24.21. Typical pipe-reactor plant for production of ammonium polyphosphate solution. (Source Fertilizer Manual.)...

Liquid ammonium phosphate fertilizers ammonium polyphosphate (APP)... 

Mono- and diammonium phosphate are used as solid fertilizers, whereas ammonium polyphosphate is mainly utilized in solution as a liquid fertilizer, since unlike the orthophosphates, it is very soluble and is more difficult to granulate than the orthophosphates. As a result of its complexing properties, it also keeps impurities (iron, aluminum, magnesium etc.) in solution. 

Liquid ammonium phosphate fertilizers Ammonium polyphosphates can be manufactured from phosphoric acids containing either high or low concentrations of poly-phosphoric acid, or from orthophosphoric acid solutions. 

Fig. 6.6-13 Flow diagram of a TVA pipe reactor-pugmill process producing granular NP fertilizer (urea, ammonium polyphosphate) [6.6.6]...

Fig. 11.24. TVA pipe-reactor process for production of 9-32-0 grade ammonium polyphosphate base suspension from wet-process orthophosphoric acid. ( Fluid Fertilizers TVA Bulletin Y-185, p. 90. Courtesy TVA.)...

Many intumescent flame retardants are based on mixtures of polyols, amines such as melamine, and phosphates such as ammonium polyphosphate. These have not been much used in vinyl because of potentially degradative effects and because of equivalent protection being supplied by phosphate plasticizers. Ammonium polyphosphate (APP), used mostly as fertilizer, is available in polymer grades from Clariant under the trade name Exolit AP. Similarly, there seems to have been little use of red phosphoras, available as Exolit RP. Work in other areas suggests investigation of... 

Magnesium oxide forms precipitates with fluorine in the reactor, which may blind the filter cloth therefore, high MgO content is considered undesirable. When phosphoric acid is used to produce ammonium phosphates or polyphosphates, water-insoluble (but citrate-soluble) magnesium ammonium phosphate compounds may be formed, These compounds form troublesome impurities in liquid fertilizers. 

Ammonium nitrate granules and fertilizers based on these are coated with a layer consisting of sodium phosphates (trimetaphosphate and polyphosphate) and salts of alkylaryl sulfo-acids. These reagents may be added either both together to the ammonium nitrate melt or separately the sodium phosphates to the melt and the sodium salts of the alkylaryl sulfo-acids to the granules. The granules with added polyphosphates are then powdered with diatomite [538]. 

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