1968 Meline TVA Plant-scale production of fertilizers in a Pan Granulator
TVA is now producing granular high-analysis fertilizers in a demonstration-scale plant utilizing a pan-granulation process that was developed on pilot-plant scale. Products currently being made in the plant are 30-4.4-0 (30-10-0) and 25-10.9-0 (25-25-0) grades of ammonium phosphate nitrate and 30-0-0-5S ammonium nitrate sulfate. The plant was designed for a production rate of 480 tons per day; however, rates as high as 560 tons per day have been achieved. In this process, the acids are partially neutralized to pH 1.5 with ammonia, the resulting solution is concentrated by evaporation, and neutralization is completed to pH of about 5.5 in a second-stage neutralizer. Granulation is accomplished by spraying the hot concentrated solution onto a cascading bed of fines in a 14-foot-diameter pan granulator. The material from the pan is dried, screened, cooled, and conditioned prior to bulk storage in controlled humidity. The granular products have good storage and handling characteristics when dried to a moisture content of 0.2 to 0.4% and coated with conventional conditioning agents.