Sulfur continued fertilization

The Spanish Civil War and World War II finally ruined the Spanish pyrites industry. Shipments had been blocked during these years, and alternatives had been found. After World War II, many new sulfuric acid plants were constructed in Europe to replace those that had been destroyed, and U.S. expansion was bolstered by economic growth, especially by demand for phosphate fertilizers. These new plants all used elemental sulfur (Contact process). While Spanish pyrites production returned to pre-war levels by 1950 (see Figure 2.5 for the early history of production), their market share had seriously eroded as sulfur demand, overall, had more than doubled. Pyrites mining as a source of sulfur continued in Spain until 2002. 

Soil sulfur deficiencies have been found in a number of regions of the world. Whereas most fertilizers used to contain sulfur, its use in commercial fertilizers has declined. With continued use of sulfur-deficient fertilizers, it is possible that sulfur will become a limiting nutrient in more cases. 

Agriculture is the largest industry for sulfur consumption. Historically, the production of phosphate fertilizers has driven the sulfur market. Phosphate fertilizers account for approximately 60% of the sulfur consumed globally. Thus, although sulfur is an important plant nutrient in itself, its greatest use in the fertilizer industry is as sulfuric acid, which is needed to break down the chemical and physical stmcture of phosphate rock to make the phosphate content more available to plant life. Other mineral acids, as well as high temperatures, also have the abiUty to achieve this result. Because of market price and availabiUty, sulfuric acid is the most economic method. About 90% of sulfur used in the fertilizer industry is for the production of phosphate fertilizers. Based on this technology, the phosphate fertilizer industry is expected to continue to depend on sulfur and sulfuric acid as a raw material. 

Historically, consumption of sulfuric acid has been a good measure of a country s degree of iadustrialization and also a good iadicator of general busiaess conditions. This is far less vaUd ia the 1990s, because of the heavy sulfuric acid usage by the phosphate fertilizer iadustry. Of total U.S. sulfuric acid consumption ia 1994 of 42.5 x 10 metric tons, over 70% went iato phosphate fertilizers as compared to 45% ia 1970 and 64% ia 1980 (144). Uses other than fertilizer have grown only slowly or declined. This trend is expected to continue. Production and consumption trends ia the United States are shown ia Tables 9 and 10. 

Because sulfuric acid has its greatest use in fertilizers, trends in that industry have a significant effect on the sulfuric acid business. Owing to a weak U.S. doUar in the early 1990s and high demand for fertilizer abroad, a considerable portion of U.S. phosphate fertilizer production was exported. High fertilizer exports are expected to continue until Thkd World countries can meet thek own demands. 

Den A batch process for making the fertilizer superphosphate. The den is the vat into which the mixture of phosphate rock and sulfuric acid is dumped after mixing. There is also a continuous-den process. Not to be confused with DEN [Deutsch - Englisch - Norwegische Gruppe], a fertilizer cartel operated in the three countries from which the name is derived from 1929 to 1930. See also Davison, Oberphos. 

Between 1970 and 1978, U.S. sulfur demand grew from 9.2 to about 12 million long tons per year, equivalent to an average annual rate of increase of about 3.4 percent. Over the forecast period, we anticipate an average annual increase of about this same rate. Our estimate assumes that the U.S. will continue to maintain world leadership as an exporter of upgraded phosphates, and that growth in domestic phosphate fertilizer consumption will average about 3 percent per year. 

Canadian demand for sulfur has amounted historically to about 10 percent of U.S. demand. We expect this relationship to continue. As in the U.S., over half of Canadian sulfur use goes into the production of fertilizers. Other major uses for sulfur are for the leaching of uranium ores, and for use in the pulp and paper industry. 

Demand for sulfur in Mexico is even more oriented toward the fertilizer sector than it is in the U.S. and Canada. In 1978, fertilizer uses accounted for about 75 percent of the total. We expect that the future use of sulfur in Mexico will continue to be oriented heavily toward the fertilizer industry. By 1990, Mexican sulfur consumption should be almost three times the current level. 

Until the 1960 s, the majority of the world s sulfur supply was the direct result of the voluntary sulfur producers. However, the advent of sour gas production in Alberta, Canada in the 1960 s resulted in the dumping of tremendous quantities of involuntary sulfur into the world marketplace. By 1968, a serious oversupply developed, sulfur prices were weakened, and a retrenchment in the fertilizer sector occured. This led to a general collapse of the sulfur market, which continued through most of 1973. 

A dilute aqueous solution of sulfuric acid at 25°C is used to absorb ammonia in a continuous reactor, thereby producing ammonium sulfate, a fertilizer ... 

Research work on the production and use of coated urea for controlled release of nitrogen is being continued. TVA hopes to reduce the ratio of nozzles to production rate and further decrease the size of the sulfur-coating equipment. A thorough agronomic evaluation of the material coated only with sulfur is being conducted which will fully indicate its potentials as a slow-release fertilizer. TVA plans to initiate demonstration-scale production of sulfur-coated urea in about 1975-76. Production rate for this unit will be about 10 tons/hr. 

Phosphoric acid is used in the production of most phosphate fertilizers. According to TFI s 1994 production cost survey of North American producers, phosphoric acid represented about 60% of the total production costs for DAP, 74% of costs of producing MAP, and 62% of costs of producing TSP. Cost of phosphate rock comprised 47% and sulfur 30% of total costs of producing phosphoric acid. Therefore, the production of phosphoric acid-based phosphate products will continue to be concentrated in the regions with low-cost phosphate rock and sulfur. Acidulation of phosphate rock with nitric acid is a competitive technology, particularly in Europe. 

Spray-Tower Ammoniation - Substantial tonnages of ammonium sulfate have been made for many years in Japan in spray towers from the chamber or contact type of sulfuric acid and anhydrous ammonia. The acid is sprayed into ammonia vapor inside the tower, and the heat of reaction produces a dry, amorphous product primarily less than 300 mesh, which is continuously removed from the base of the tower by a screw conveyer. This form of ammonium sulfate is particularly suitable for use in granular compound fertilizers. 

The estimated consumption of sulfuric acid in 1996 by the industrial sector in the United States is shown in Figure 35.1. In Canada, while fertilizer consumption is not as prominent, consumption of sulfuric acid follows a similar pattern to that in the United States fertilizers—68% mining—5.8% miscellaneous—10.6% inorganics—5.1% others, including petroleum refining and products, synthetic rubber and plastics, pulp mills and other paper products, and industrial organic chemicals—10.5% (CIS, 1997). Sulfuric acid consumption is very stable and should continue to be so. 

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