Estimation of Carbon Monoxide and Carbon Dioxide at Sub-ppm Level Concentrations in Ammonia Synthesis Gas

Estimation of carbon monoxide and carbon dioxide in ppm levels in ammonia synthesis gas is of considerable importance in industry. Since conventional methods of estimation of carbon monoxide are not suitable in the presence of a large excess of hydrogen, attempts were made to obtain quantitative analysis of CO in the ppm range using differential spectrophotometry and reaction gas chromatography without resorting to preconcentration techniques. The I2O5 method of estimating CO as I3− was modified using on-line methanation of CO. In conjunction with differential spectrophotometric measurements, as low as 0.7 ppm CO could be quantitatively estimated with an accuracy of ± 20% In the gas chromatographic method, by adopting dual column techniques, on line reactors, and optimisation of column temperature and carrier flow rate, quantitative analysis of CO and CO2 at levels as low as 0.2 ppm in 2–5 ml samples were found feasible. Results of the experiments to simultaneously estimate CO and CO2 from a single injection of sample are also reported.