Estimating NOx emissions of useful two-fuel blends from literature data

Emissions of nitrogen oxides (NOx) arising from the combustion of fuels are a significant source of air pollution. Estimating them for a given fuel blend is difficult, because the emissions are affected in a highly complex manner by several factors such as fuel components, fuel composition, combustor design, temperature, pressure, and fuel-to-air ratio. Besides, experimental emission studies are highly specific and limited, and simply cannot emulate real-life combustion systems and conditions exactly. Therefore, procedures to estimate NOx emissions for any given system/scenario would be highly useful. The present study uses the data from NOx emissions studies in the literature to derive several models for predicting NOx emissions for some useful fuel blends. The study is limited to the blends of ammonia, natural gas, hydrogen, and kerosene, and considers the effects of pressure, temper-ature, fuel to air equivalence ratio (FAR), and extent of premixing (alpha). First, simple linear models are derived for predicting emissions for individual fuels. Then, an artificial neural network (ANN) is calibrated to predict NOx emissions for two-fuel blends. While both models correctly capture the qualitative trends of emissions in the calibrated ranges, the ANN model is quantitatively superior. Hydrogen produces maximum NOx emission (5000 ppm), while, kerosene gives the least NOx (100 ppm). A case study on the NOx emissions from the evolving power sector is also provided. NOx emission exceeds 2000 ppm and 1500 ppm for the combustion of natural gas-hydrogen and natural gas-ammonia blends respectively, when hydrogen and ammonia dominate the blend composition.

Automated summary

Estimating emissions of nitrogen oxides (NOx) from fuel combustion is difficult due to the complex nature of the factors involved. This study uses data from literature to develop models for predicting NOx emissions for various fuel blends. The study found that hydrogen produces the highest NOx emissions, while kerosene produces the least.