ABSTRACT
During 1975 and 1976 the Tennessee Valley Authority developed a melt granulation process using the pipe-cross reactor for granulating ammonium phosphates and NPK mixtures. A 1980 survey shows that there are 107 granulation plants in the United States operated by 37 companies that produce about nine million tons of homogeneous NPKS granular fertilizer. When using conventional granulation, only about 25 tons per hour of the 6-24-24 grade could be produced. In conventional granulation more dust and fine particles are moving through the processing equipment. Replacement cost of a typical granulation plant is about $10,000,000, and almost $100,000 per year will be spent on equipment in a properly maintained plant. Payback time, normally less than one year, is calculated on the basis of eliminating steam and reducing fossil fuel drying from the granulation process. In a number of cases, pipe-cross reactor installation has significantly upgraded the overall condition of the granulation plant.
