Drying of solids is of great significance in fertilizer industry as the quality of final product should meet the commercial required standards. A rotary dryer which has been investigated in the present study is used in ammonium nitrate (AN) plant located at Shiraz Petrochemical Complex (SPC). This plant is designed to produce 650 metric tons of final products in a day. In this work, mathematical modeling of the concurrent rotary dryer for AN including heat and mass transfer equations between solid and air was developed. New correlations were proposed for AN equilibrium moisture and drying rate which were used in the modeling. The model was checked against the industrial data which showed a good agreement. The model predicts air and product moisture and temperature depending on working conditions of the rotary dryer. Regardless of the slope and speed of the dryer, inlet AN moisture and air temperature have been shown to be the variables that have the greatest effect, on the outlet moisture content of the product. (C) 2013 Elsevier B.V. All rights reserved.