The Fate of Ammonia and Hydrogen Cyanide During Flameless Combustion of Low Calorific Value Gases

In this paper, a review of the experimental investigations on the fuel-NOx formation during flameless combustion is presented. The first series of experiments described in the paper were conducted using ammonia doped synthetic gases with different compositions. During these experiments, the influence of gas composition on the conversion of ammonia (NH3) to NOx is investigated. The second series of experiments were conducted using product gas generated in a fluidized bed gasifier. These results show the dependencies between the gasifier operating parameters, product gas composition and final NOx emissions. Moreover, the concentrations of the ammonia and hydrogen cyanide (HCN) in the product gas were measured in order to calculate the conversion ratios of these compounds to NOx. The results show the significant influence of the gas composition and the gasifier process parameters on the final NOx emissions. In particular, the hydrocarbon content influences the ammonia to NOx conversion. The lowest NOx emissions and therefore the lowest conversion ratios were measured while burning gases with a low hydrocarbon content. An increase of the hydrocarbon concentration in the gas corresponded to a rapid increase in the conversion ratios.