This paper deals with the simulation and optimization of composite distillation columns for the waste nitric acid recovery process. The composite distillation columns which consist of a multistage vacuum column and an atmospheric pressure column, half of which, consists of a packed bed, were modeled by using an equilibrium stage method and a nonequilibrium stage method. The required physical properties of a nitric acid solution for simulation were obtained from correlations based on experimental data. Simulation results using the nonequilibrium model showed better agreement with actual plant data than those of the equilibrium model. Based on the simulation results, the optimal operation conditions were studied. In the optimization reflux ratio was employed as the key variable to maximize the operating profit.