Fractionation of N-15 in countercurrent HNO3-NO system at low temperature

This article describes the method for fractionation of N-15 isotope based o n the exchange of nitrogen isotopes in the system consisting of liquid mixt ures of nitric acid and nitrogen oxides and the gaseous nitrogen oxide in t he temperature range between 233 and 263 K under atmospheric pressure devel oped by the authors. The chemical interactions occurring between liquid nit ric acid and gaseous nitrogen oxide at low temperatures and the equilibrium of the nitrogen isotopes exchange has been studied by means of the analysi s of each co-existing phase in a packed column with counter-current movemen t of liquid and gas phases. The results obtained by theoretical modeling an d experimental testing of the experimental plant have allowed one to conclu de that the low temperature NITROX method is promising for the large-scale N-15 production. This method improves upon the main technological parameter s of the process as compared to traditional room temperature NITROX system. It allows for increasing the productivity of the same column and the degre e of N-15 extraction from the feed nitric acid up to two times, and for dec reasing almost twice the consumption of sulphur dioxide (which is used to c onvert HNO3 to NO).