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

Abstract

In this paper, a review of the experimental investigations on the fuel-NO x 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 (NH 3 ) to NO x 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 NO x 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 NO x . The results show the significant influence of the gas composition and the gasifier process parameters on the final NO x emissions. In particular, the hydrocarbon content influences the ammonia to NO x conversion. The lowest NO x 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.

Experimental and Numerical Study of the Fuel-NOx Formation at High CO2 Concentrations in a Jet-Stirred Reactor

“…Woo et al found that the fuel-NO x formation increases monotonically with increasing initial NH 3 concentration when pure oxygen is used as an oxidizer. Zieba et al , adopted a chemical reaction network to investigate the effects of CH 4 on fuel-NO x formation during flameless combustion with NH 3 as the nitrogen source. They found that the existence of CH 4 slows the oxidation of NH 3 , whereas NO x emissions increase.…”

MILD Combustion and Biofuels: A Minireview

“…The effect of a few ppm of ammonia on NO x formation during oxidation of biogas, natural gas, and syngas was explored by Zieba and coworkers , and Slefarski in a flameless burner. Results by these authors are summarized in Figure , where NO x concentration measured in the flues gases of a flameless burner have been reported.…”

“…In a very recent work by Sorrentino et al, the same trend has been obtained studying MILD combustion in methane/ammonia in a cyclonic burner in a wider range of NH 3 (from 0% to 100%). A kinetic analysis carried out on available models highlighted that the main backbone of the C and N oxidation mechanism proceed independently from each other and only compete for radicals. , …”

“…NO x emission in MILD combustion of biogas in the presence of ammonia as impurities in dependence of ammonia concentration (black symbols) and in dependence of CH 4 concentration. , …”

“…A kinetic analysis carried out on available models highlighted that the main backbone of the C and N oxidation mechanism proceed independently from each other and only compete for radicals. 100,103 As is well known, the presence of H 2 S in biogas represents a serious problem due to its toxicity and its oxidation to SO 2 and SO 3 during the combustion process in standard conditions, which are highly corrosive for appliances and have a high environmental impact. H 2 S is also present in natural gas in small quantities and is one of the main component of sour gases, where the concentration reaches levels as high as 30%.…”