Mechanism and modeling of nitrogen chemistry in combustion

[1] We present a global tabulation of black carbon (BC) and primary organic carbon (OC) particles emitted from combustion. We include emissions from fossil fuels, biofuels, open biomass burning, and burning of urban waste. Previous ‘‘bottom-up’’ inventories of black and organic carbon have assigned emission factors on the basis of fuel type and economic sector alone. Because emission rates are highly dependent on combustion practice, we consider combinations of fuel, combustion type, and emission controls and their prevalence on a regional basis. Central estimates of global annual emissions are 8.0 Tg for black carbon and 33.9 Tg for organic carbon. These estimates are lower than previously published estimates by 25–35%. The present inventory is based on 1996 fuel-use data, updating previous estimates that have relied on consumption data from 1984. An offset between decreased emission factors and increased energy use since the base year of the previous inventory prevents the difference between this work and previous inventories from being greater. The contributions of fossil fuel, biofuel, and open burning are estimated as 38%, 20%, and 42%, respectively, for BC, and 7%, 19%, and 74%, respectively, for OC. We present a bottom-up estimate of uncertainties in source strength by combining uncertainties in particulate matter emission factors, emission characterization, and fuel use. The total uncertainties are about a factor of 2, with uncertainty ranges of 4.3–22 Tg/yr for BC and 17–77 Tg/yr for OC. Low-technology combustion contributes greatly to both the emissions and the uncertainties. Advances in emission characterization for small residential, industrial, and mobile sources and topdown analysis combining field measurements and transport modeling with iterative inventory development will be required to reduce the uncertainties further. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; KEYWORDS: emission, black carbon, organic carbon, fossil fuel, biofuel, biomass burning

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A technology-based global inventory of black and organic carbon emissions from combustion

Oxy-fuel combustion of solid fuels

Particulate matter (PM) emissions from stationary combustion sources burning coal, fuel oil, biomass, and waste, and PM from internal combustion (IC) engines burning gasoline and diesel, are a significant source of primary particles smaller than 2.5 μm (PM2.5) in urban areas. Combustion-generated particles are generally smaller than geologically produced dust and have unique chemical composition and morphology. The fundamental processes affecting formation of combustion PM and the emission characteristics of important applications are reviewed. Particles containing transition metals, ultrafine particles, and soot are emphasized because these types of particles have been studied extensively, and their emissions are controlled by the fuel composition and the oxidant-tem-perature-mixing history from the flame to the stack. There is a need for better integration of the combustion, air pollution control, atmospheric chemistry, and inhalation health research communities. Epidemiology has demonstrated t...

https://www.tandfonline.com/doi/pdf/10.1080/10473289.2000.10464197

Combustion aerosols: factors governing their size and composition and implications to human health.

Fuel nitrogen conversion in solid fuel fired systems

A mathematical model for the flash calcination of Ca(OH)/sub 2/ and CaCO/sub 3/ is presented. The model describes the decomposition of the parent material at the reactant-product interface, the diffusion of CO/sub 2/ or H/sub 2/O through the growing CaO layer, and the sintering of the CaO layer. The model is qualitative, but it provides useful estimates of peak CO/sub 2/ pressures on the CaO layer, relative rates of surface area development and loss for Ca(OH)/sub 2/ and CaCO/sub 3/, the effect of particle size, and the effects of time and temperature.

A mathematical model for the flash calcination of dispersed calcium carbonate and calcium hydroxide particles

Char nitrogen conversion: implications to emissions from coal-fired utility boilers

A laboratory combustor was used to investigate the factors that influence the conversion of fuel nitrogen in coal during coal combustion. Fuel NO was isolated by experimentation utilizing Argon/Oxygen/Carbon Dioxide mixtures as the oxidant, and care was taken to compare cases with air at matched conditions. For both well mixed and slowly mixed flame types, fuel NO contributed over 75% of the total NO emissions for all conditions examined. Fuel NO was insensitive to temperature changes except when the adiabatic flame temperatures were above 2480°K (4000°F). At the highest adiabatic flame temperature, 2580°K (4200°F), a 10% increase in fuel NO was observed. Four different coals and one coal char were investigated. Fuel NO could not be correlated with fuel nitrogen content alone, even though aerodynamic conditions were kept constant. Fuel nitrogen conversion to NO during pulverized char combustion was 12–16% at a stoichiometric ratio of 1.15 compared to 28% for a pulverized coal of the same nitrogen content. Furthermore, in contrast to the coal results, NO emissions from char combustion were not greatly influenced by changes in injector design. The implication is that although conversion of fuel nitrogen to NO may be relatively low during the char burnout regime of coal combustion, the residual “char NO” may be especially resistant to abatement by modifications of the burner aerodynamics.

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Pulverized coal combustion: The influence of flame temperature and coal composition on thermal and fuel NOx

Relative Contributions of Volatile Nitrogen and Char Nitrogen to NOx Emissions from Pulverized Coal Flames

To simulate the staged availability of transient high surface area CaO observed in high-temperature flow-reactor data, the paper describes the rate of calcination of CaCO{sub 3} or Ca(OH)2, using an empirical modification of the shrinking-core model. The physical model depicts particle decomposition by the shrinking-core mechanism. The subsequent time-dependent decrease in CaO reactivity (surface area and porosity) due to sintering is simulated by reducing the grain-center spacing for the matrix of overlapping CaO grains. Information from SEM micrographs and from other physical property measurements of the porous particles is incorporated. The submodel simulates the time-dependent availability and reactivity of CaO for a comprehensive model used to study sulfation of CaCO{sub 3} and Ca(OH)2 particles at upper-furnace injection conditions.

David W. Pershing

Papers

A mathematical model for the flash calcination of dispersed calcium carbonate and calcium hydroxide particles

Char nitrogen conversion: implications to emissions from coal-fired utility boilers

Pulverized coal combustion: The influence of flame temperature and coal composition on thermal and fuel NOx

Relative Contributions of Volatile Nitrogen and Char Nitrogen to NOx Emissions from Pulverized Coal Flames

Calcination and sintering models for application to high-temperature, short-time sulfation of calcium-based sorbents