Refinery gases may contain low levels of oxides of nitrogen commonly know as NOₓ. The oxides can regroup a wide variety of species. Nitric Oxide and Nitrogen dioxide are predominant nitrogen species entering the cold box unit and it may be produced from the coke combustion process associated with catalytic cracker regeneration.
The chemistry of NOₓ compounds at different pressure and temperature conditions inside the cold box unit can create a potentially explosive environment. The creation of gummy by products as a result of a reaction between conjugated dienes must be monitored. In many cases NOₓ gums may be formed from simple olefins with trace level dienes. NOₓ gums formed at cryogenic temperatures tend to be much more unstable and potentially explosive.
CI Analytics has developed an analyzer capable of measuring total NOx content at ultra low concentration ranges without the typical interferences observed with other technologies, such a s chemiluminescence.