Sulphur Sources, their Processing and Use in Fertiliser Manufacture

Keywords: Brimstone, Elemental sulphur, Elemental sulphur fertilisers, Frasch, Liquid sulphur fertilisers, Pyrites, Sulphate sulphur fertilisers, Sulphur-containing compound fertilisers, Sulphur in other forms, Sulphuric acid.

Since the start of industrial times, sulphur has been a key raw material for the fertiliser and chemical industries. It is the primary source for sulphuric acid, the world’s most widely used chemical, in a host of manufacturing processes. Sulphuric acid is used by the fertiliser industry to manufacture primarily phosphates or phosphoric acid, and also other fertilisers like ammonium sulphate.

The sulphur industry has undergone major changes during the past four decades. From being essentially a mining industry, the sector has evolved to a non-voluntary co-product of the petroleum and non-ferrous metals sectors. Changes in sulphur consumption have also been marked. Although sulphur is an increasingly important plant nutrient in its own right, its greatest use in the fertiliser industry is as an input for phosphate fertiliser manufacture. In the 1950s and 1960s a shift from low to high concentration phosphate materials signified a sharp increase in sulphur demand. More recently, non-fertiliser sulphur use gained importance resulting from increased use in hydrometallurgical applications.

Sulphur fertilisers can be divided into three groups:

1. Fertilisers containing sulphate;

2. Fertilisers containing elemental sulphur; and

3. Liquid sulphur fertilisers.

Sulphate fertilisers provide most of the fertiliser sulphur applied to soils. Elemental sulphur-based fertilisers are the most concentrated sulphur carrier. Modern technologies have improved their properties and increased their use in direct applications or as additives to various fertilisers. Thiosulphates will continue to gain in popularity for fluid fertiliser applications. Sulphur-modified or enriched compound fertilisers using either sulphate or elemental sulphur have several advantages, including improved chemical and physical properties; and providing multi-nutrients with balanced ratios for plant nutrition for direct application purposes.

The sulphur fertiliser industry has made several advancements with products in recent years. The sector has developed materials adapted to particular crop and management situations. Sulphur fertilisers include a wide range of products, offering versatility for a variety of applications.

D. L. Messick, C. de Brey, and M. X. Fan, The Sulphur Institute, 1140 Connecticut Avenue N.W. Suite 612, Washington, D.C. 20036 USA.

24 pages, 5 figures, 1 table, 12 references.