Soot formation combustion system

The control system was also demonstrated in open and enclosed systems with highly sooting fuels including benzene. When the proper phase angle of fuel injection was used, soot formation could be prevented, and an entirely blue flame realized, even when gaseous benzene constituted 66% of the combustible content. The combustion efficiency of the benzene was beyond 99.999% even at an overall equivalence ratio of 1.0. 

Before we examine the oxidation pathways available to aromatic systems, it is first instructive to review the most notorious role of these compounds in combustion chemistry their propensity to lead to soot formation. Soot is a byproduct of fuel-rich combustion, and soot particles can affect respiration and general health in humans." Soot production is a result of polycyclic aromatic hydrocarbon (PAH) formation in flames as reactive hydrocarbon radical intermediates combine to grow... 

The formation of soot in a combustion system has been shown to correlate well, at least to first order, as a function of the H/C ratio of the particular fuel. However, for a specific fuel the actual amount of soot formed is a function of the combustion... 

Farmer, R. C. Edelman, R. B. Wong, E. "Modeling Soot Emissions in Combustion Systems" Particulate Carbon Formation During Combustion, 1980, GM Research Symposium. 

Synthetic liquid fuels derived from coal and shale will differ in some characteristics from conventional fuels derived from petroleum. For example, liquid synfuels are expected to contain significantly higher levels of aromatic hydrocarbons, especially for coal-derived fuels, and higher levels of bound nitrogen. These differences can affect the combustion system accepting such fuels in important ways. In continuous combustors, i.e. gas turbines, the increased aromatics content of coal-derived fuels is expected to promote the formation of soot which, in turn, will increase radiation to the combustor liner, raise liner temperature, and possibly result in shortened service life. Deposit formation and the emission of smoke are other potential effects which are cause for concern. Higher nitrogen levels in synfuels are expected to show up as increased emissions of N0X (NO+NO2) An earlier paper presented results of an experimental study on the effect of aromatics and combustor... 

Effect of Manganese. This metal is relatively effective in reducing smoke from gas turbine combustion systems (8) and furnaces (9). However, under the same experimental conditions as above, no significant effort was ever found with this metal or with iron and nickel. Furthermore, when oxygen was injected into the primary zone of carbon formation with a microprobe, the soot decrease profile did not change when manganese was added to the initial mixture. Hence this metal does not appear to stimulate the oxidation of small soot particles. 

Estimates of fuel sooting tendency have been made using various types of flames and chemical systems. In the context to be used here, the term sooting tendency generally refers to a qualitative or quantitative measure of the incipient soot particle formation rate. In many cases, this tendency varies strongly with the type of flame or combustion process under investigation. This variation is important because the incipient soot particle formation rate determines the soot volume fraction formed in a combustion system. 

Fuel combustion can lead to pyrolysis of hydrocarbon fuels and soot formation, important in diesel engines and contributing to particulate emissions. A proportion of this soot finds its way into the lubricating oil and increasing use of EGR systems to reduce particulate and gaseous emissions has led to higher levels of soot loading in lubricants. 

The kinetic aspect common to all the topics discussed in this chapter is the pyrolysis reactions. The same kinetic approach and similar lumping techniques are conveniently applied moving from the simpler system of ethane dehydrogenation to produce ethylene, up to the coke formation in delayed coking processes or to soot formation in combustion environments. The principles of reliable kinetic models are then presented to simulate pyrolysis of hydrocarbon mixtures in gas and condensed phase. The thermal degradation of plastics is a further example of these kinetic schemes. Furthermore, mechanistic models are also available for the formation and progressive evolution of both carbon deposits in pyrolysis units and soot particles in diffusion flames. 

H. "Numerical Modeling of Soot Formation in Glass Melting Furnaces." In Heat Transfer in Radiating and Combusting Systems 2, Eurotherm Seminar, no. 37, 167-80, 1994. 

Bockhom, H., Fetting, F., and Wenz, H. W. (1983) Chemistry of intermediate species in rich combustion of benzene, in Soot Formation in Combustion Systems and Its Toxic Properties, J. Lahaye, ed., Plenum Press, New York, pp. 57-94. 

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