Improved Synthesis of the Nitric Acid Process

This paper introduces a new process concept for the nitric acid process that improves the exergetic efficiency of the process. Further it introduces and illustrates a general synthesis method that allows a fast and efficient evaluation of different process concepts. The conventional as well as the new nitric acid process is optimized using the proposed approach. Comparison is made on basis of the detailed process description given by Gaggioli et al. (1991) and Linnhoff and Alanis (1991) in their competition between Exergy and Pinch analysis. Energy efficiency is meassured in net power surplus for the process. Where optimum performance for a conventional process is approximately 175 kWh/t(HNO3) it is found to be approximately 230 kWh/t(HNO3) with the new process. Another but equally important feature is that no steam cycle is necessary and thus an expensive steam turbine can be saved. If the saturated cycle is combined with a steam cycle it is possible to enhance the efficiency to 261 kWh/t(HNO3).