Modeling and simulation of a nitric acid recovery process

A nitric acid recovery process using composite distillation columns was modeled and simulated. The composite distillation columns consist of a multistage vacuum tower and an atmospheric pressure tower half of which consists of packed bed. The vacuum tower and the atmospheric pressure tower were modeled by using equilibrium stage method and non-equilibrium stage method respectively. The required thermodynamic properties for nitric acid solution were obtained from correlations based on experimental data. Results of simulations showed good agreement with actual plant data. From the results of simulations it was found that the upper half of the atmospheric pressure column and the vacuum column, consisting of plate column, can be modeled using equilibrium model, but the lower half of the atmospheric pressure column, which are packed parts, can be modeled effectively using non-equilibrium model. The non-equilibrium model developed in the present study showed good agreement with actual operaton data.