Emissions of nitrous oxide (N2O) have been analyzed from industrial boilers and from a large experimental combustor burning natural gas, oil, or coal. Production of N2O and production of NOx were observed to be correlated, with an average molar ratio of 0.58:1 (N2O‐N: NO). The content of fuel nitrogen plays an important role in determining emissions of both N2O and NOx. In conventional single‐stage combustors, about 14% of fuel nitrogen is converted to N2O and 24% is converted to NOx. Conversion of fuel nitrogen to N2O was much less efficient (2–4 %) in a two‐stage experimental combustor and in wood fires. A model is presented describing emissions of N2O globally, from the beginning of the industrial revolution to the present. Combustion of fossil fuel is estimated to release 3.2×106 tons N2O (as N) y−1 at present, with 83% of this derived from burning of coal in large industrial boilers. The biospheric source of N2O is calculated as 8.8×106 t y−1. The tropospheric concentration of N2O in 1860 is estimated to have been 280.7 ppb. We expect that concentrations of N2O should rise more than 20% to about 367 ppb by the year 2050, based on conservative projections of world energy consumption.

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Due to the particle to particle variation of coal mineral properties and random coalescence of mineral particles during coal burnout, fly ash particle properties change from particle to particle. The variations of particle properties (e.g. SiO2 content, viscosity) can be mathematically described by random variables. Since bulk analysis of fly ash gives only the mean values of chosen random variables, it is considered insufficient to describe the fly ash behavior either in boiler slagging/fouling or in different concrete structures. SEM-AIA-EDAX technique was used to supply raw data for estimating the distribution functions of particle size and chemical compounds in Texas lignite minerals and fly ash and Eagle Butte fly ash. To determine the volume based size distributions of these samples from their area-based size distributions, Abelian transformation was used. To estimate the distribution functions of CaO and SiO2 contents of the samples, particle area fractions were used. The confidence limits were also calculated for the estimated parameters. By determining the distribution functions of particle viscosity and chemical composition, it was shown that in the case of Texas lignite the coal burnout does not cause significant changes in the mineral matter properties. It was observed that the properties of fly ash depended solely on the mineral matter properties. However, in the Eagle Butte case the coal burnout has a major effect on the fly ash size distribution and its chemical composition.

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