Fertilisers [14]

Australian soils are notably deficient in phosphorus and agriculture was the mainstay of Australian economy -and extensive, hence it could only afford cheap fertiliser. As a result Australia became one of the largest users and producers of superphosphate in the world. Advances made by Australians were perhaps more in methods of application and in processing than in the conventional, basic chemistry.

By the mid 1920s the potential benefit of the combination of superphosphate and subterranean clover for wool production was well understood by both CSIR scientists, who had been conducting detailed experiments in South Australia, and by many graziers. To cope with the vastness of the country, Australian companies and farmers were amongst the first to introduce aerial seeding of clover and top-dressing with superphosphate, intially on the Central Tablelands of NSW. Its use spread to other States and became one of Australia's most important contributions to modern agriculture. When concern was expressed at drift and associated inefficiency of spraying fine superphosphate, manufacturers commenced granulating the powder into granules to improve its physical properties. This was expensive, as it involved wetting the cured superphosphate while rolling it in a drum and then drying the granules. Adelaide Chemical developed a process for producing granular superphosphate directly from the den. The powder was directed into a rotating rubber-lined drum in which the loose rubber panels acted as self-cleaning lifters and assisted in granulation. This process has been adopted, occasionally with modifications, by the rest of the industry.

Another largely Australian development in the late 1950s was the use (particularly for aerial spraying) of sulphur instead of, or in addition to, the sulphur content (from calcium sulphate) in superphosphate in soils where phosphate had been built up or was present naturally. The fire hazard of fine sulphur limited its aerial application as a mere admixture. Improved formulations were therefore developed by adding sulphur during acidulation or by spraying molten sulphur into the superphosphate mixer. By acidifying phosphate rock with phosphoric acid instead of sulphuric, high analysis phosphate fertilisers were developed from imported technology on two Dorr-Oliver plants (later closed down) and three Nissan plants (ICI Australia, later Albright and Wilson at Yarraville, 1963; Greenleaf Fertilisers at Newcastle, 1965; and ACF and Shirley's Fertilisers at Pinkenba, 1966).

Ammonium phosphates have been produced in the plants at Newcastle, Yarraville and Kwinana and the Austral-Pacific Fertilisers Ltd. Gibson Island, Brisbane, plant by reacting ammonia and phosphoric acid in a preneutraliser and then grinding the material. In 1975 Austral-Pacific Fertilisers Ltd. commissioned a pipe reactor feed to the granulator for the production of mono- and diammonium phosphate and in 1977 this was extended to ammonium sulphate. Both these processes proved to be world 'firsts' and the technology was licenced in Brazil, Spain and to associated companies, for the construction of new plants as well as for retrofitting.

Australian Academy of Technological Sciences and Engineering