Modeling, simulation and optimization: mono pressure nitric acid process

Abstract

The present work focuses on a strategy for optimizing mono pressure weak nitric acid plants. The optimization strategy addresses important processes which include oxidation of ammonia to nitric oxide, heat recovery from product stream of ammonia oxidation reactor and absorption accompanied by complex chemical reactions of multi-component nitrogen oxide gases into water. In design and optimization of nitric acid process, it is essential to understand the rate controlling step for ammonia oxidation process, strategy to be adopted for heat exchanger network design, rates of mass transfer and chemical reaction for nitrogen oxide absorption and the combined effects of several equilibria. The work addresses these issues taking through the complexities in the above mentioned processes. The parametric sensitivity of few parameters such as ammonia to air ratio, excess oxygen/air, selectivity, power recovery based on the performance efficiency of compressor and expander, inlet and outlet nitrogen oxide composition in condenser and absorption column have been a part of our investigation either explicitly or implicitly. Further, for the absorption column, the effects of geometrical parameters, excess air, extent of absorption, product acid concentration, temperature and pressure have been analyzed for the purpose of optimization of nitric acid plant. All parameters having major influence on annualized cost of product acid have been analyzed and presented.