Granular Ammonium Nitrate – A New Route

Keywords: Ammonium nitrate, Granulation, Pipe reactor, Fluidised drum reactor.

Incitec – Kooragang Island, a subsidiary of Incitec, has recently installed and commissioned a new plant producing granular ammonium nitrate. The process route chosen combines the direct production of high strength ammonium nitrate melt using a pipe reactor with the granulation and drying using a fluidised drum granulator.

The major criterion in the process selection was the minimisation of the capital cost. Other requirements included significant limitations on effluent discharges, and a plant capable of operating under minimum operator surveillance.

The processes chosen were the AZF pipe reactor process from La Grande Paroisse, together with the fluidised drum granulator process from Kaltenbach-Thuring S.A. This combined route more closely met our criteria than any single licensor’s process. Each met their respective selection criteria individually, however, it would be possible to integrate the two processes more fully to achieve even better operating efficiencies.

Other plants have used the pipe reactor process for ammonium nitrate. The design melt concentration from the Incitec-K.I.’s plant is 92% with 94% being achievable. The steam from the process is used to preheat the nitric acid feed and to vaporise the ammonia feed. Equipment size, for both the pipe reactor neutraliser and the associated air pollution control equipment, is relatively small, thus reducing the capital cost. The plant is fully instrumented for efficient start-ups and shut-downs and to meet tight safety and environmental standards.

The fluidised drum granulation process has not been used previously for producing granular ammonium nitrate. However, it is in use for urea prill fattening. Extensive pilot plant trials were carried out to define the parameters for granulating ammonium nitrate. The process uses a standard granulation circuit except that both granulation and drying are achieved in the one small drum. The recycle ratio is low. Air pollution abatement equipment is smaller than some other processes.

The product is superior to the prilled fertiliser grade ammonium nitrate previously produced. Although not included in the original specifications, chemically pure ammonium nitrate has also been produced successfully in this plant.

A M J Sato, Incitec, Kooragang Island, Newcastle, New South Wales, Australia.

31 Pges, 11 Figures.