Superphosphate fertilizer ordinary

Resources of Sulfur. In most of the technologies employed to convert phosphate rock to phosphate fertilizer, sulfur, in the form of sulfuric acid, is vital. Treatment of rock with sulfuric acid is the procedure for producing ordinary superphosphate fertilizer, and treatment of rock using a higher proportion of sulfuric acid is the first step in the production of phosphoric acid, a production intermediate for most other phosphate fertilizers. Over 1.8 tons of sulfur is consumed by the world fertilizer industry for each ton of fertilizer phosphoms produced, ie, 0.8 t of sulfur for each ton of total 13.7 X 10 t of sulfur consumed in the United States for all purposes in 1991, 60% was for the production of phosphate fertilizers (109). Worldwide the percentage was probably even higher. 

Analyses of compound fertilizer rose further as triple superphosphate replaced ordinary superphosphate, and ammonium nitrate or urea replaced ammonium sulfate or sodium nitrate. Later, still higher analyses were attained by the liberal use of phosphoric acid and ammonia in the formulations. Compound fertilizer preparation was no longer a simple mechanical task but a complex chemical engineering operation. As such, its economics depended on large-scale operation. Some small local mixers expanded to large regional manufacturers others became bulk blenders or went out of business. 

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. 

Normal Superphosphate. From its beginning as the first commercial phosphate fertilizer, normal superphosphate (NSP), also called ordinary or single superphosphate, has continued among the top fertilizers of the world (Fig. 8). Use of normal superphosphate decreased steadily on a percentage basis because of growing production of more concentrated materials, but grew on a P2 s basis to a maximum of 6.7 x 10 t... 

Some commonly used primary nutrient fertilizers are incidentally also rich sources of calcium. Ordinary superphosphate contains monocalcium phosphate and gypsum in amounts equivalent to all of the calcium originally present in the phosphate rock. Triple superphosphate contains soluble monocalcium phosphate equivalent to essentially all the P2 5 product. Other fertilizers rich in calcium are calcium nitrate [10124-37-5] calcium ammonium nitrate [39368-85-9] and calcium cyanamide [156-62-7]. The popular ammonium phosphate-based fertilizers are essentially devoid of calcium, but, in view of the natural calcium content of soils, this does not appear to be a problem. 

All phosphorus fertilizers come from wet process phosphoric acid or directly from phosphate rock. Normal superphosphate, triple or concentrated superphosphate, and ammonium phosphate are the three common types used. Normal or ordinary superphosphate (NSP or OSP) is mostly monocalcium phosphate and calcium sulfate. It is made from phosphate rock and sulfuric acid and is equated to a 20% P2O5 content. It led the market until 1964. The production of normal superphosphate is similar to that for the manufacture of wet process phosphoric acid (Chapter 2, Section 3) except that there is only partial neutralization. Normal superphosphate is no longer used to any great extent. The following reaction is one example of an equation that represents this process. 

Utilization of the inclined-pan granulator in the fertilizer industry was first reported in Germany in 195 3 for the granulation of ordinary superphosphate and the first documented application of suspended-solids agglomerators was in the early 1960s using a spouted bed [B.48]. 

Triple superphosphate did not become an important fertilizer until the 1950s. In contrast with ordinary su perphosphate, triple superphosphate has a higher content of phosphate than the phosphate rock from which it is made thus, it should be produced near the source of the rock in large plants, with shipment of the product to local mixing plants or to farmers. 

Major routes of mineral phosphate (phosphate rock) into finished fertilizers are outlined in Fig. 11.5 and are discussed below. It is obvious from the figure that although phosphate rock is used directly in several major fertilizer production processes (ordinary superphosphate, nitric phosphates), most important processes require that the rock phosphate first be converted to phosphoric acid (H3PO4). Phosphoric acid production, then, is a very significant component of the phosphate fertilizer industry. The processes used for the production of fertilizer-grade phosphoric acid are known collectively as wet processes, and involve, initially, dissolution of the rock in sulfuric acid. (The highly specialized technology of wet-process acid production was discussed in Chapter 10.)... 

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