Fuel composition change

Table 9. Effect of Fuel Composition Change on Exhaust Emissions ...

Table 7.5. Fuel composition change and engine emission. Test data for 1989 models vehicles (Hansen, 1991)...

The agreement is remarkably good, considering that the computer codes take into account the changes in cross sections and reactor parameters that occur as fuel composition changes, and also follow spatial nonuniformities in flux and fuel composition. All these factors have been neglected in this section. 

Ultralow NO c and the latest generation burners may have less turndown capability than conventional burners. High CO levels can occur when firebox temperatures are below 1240 °F. Flame instability and flameout can occur when firebox temperatures are below 1200 °F. Since ultralow NO and the latest generation burners are often designed at the limit of stability, a fuel composition change may cause a stability problem. 

The types of problems a fired heater or furnace system typically encounters include flame impingement on tubes, coke buildup inside the tubes, hot spots inside the furnace, fuel composition changes, burner flameout, control-valve failure, and feed-pump failure. 

During normal operations, checklists and samples are collected as advanced instrumentation monitors the process. The types of problems a fired heater or furnace system typically encounter include flame impingement on tubes, coke buildup inside the tubes, hot spots inside the furnace, fuel composition changes, burner flameout, control valve failure, and feed-pump failure. Other problems may include incorrect temperature indicator readings, failure of oxygen analyzers, oxygen leaks on the furnace, and the unexpected shutdown of downstream equipment. A fired heater system is designed to run almost continuously, 24 hours a day, 7 days a week. The operational team is in place to ensure that the equipment and systems operate safely, effectively, and produce a quality product that meets or exceeds customer expectations. 

Unlike premixed flames, which have a very narrow reaction zone, diffusion flames have a wider region over which the composition changes and chemical reactions can take place. Obviously, these changes are principally due to some interdiffusion of reactants and products. Hottel and Hawthorne [5] were the first to make detailed measurements of species distributions in a concentric laminar H2-air diffusion flame. Fig. 6.5 shows the type of results they obtained for a radial distribution at a height corresponding to a cross-section of the overventilated flame depicted in Fig. 6.2. Smyth et al. [2] made very detailed and accurate measurements of temperature and species variation across a Wolfhard-Parker burner in which methane was the fuel. Their results are shown in Figs. 6.6 and 6.7. 

An analysis by Cairns and Liebhafsky (3) for a H2/air fuel cell shows that a change in the gas composition that produces a 60 mV change in the reversible cell potential near room temperature corresponds to a 300 mV change at 1200°C (2192°F). Thus, gas composition changes are more significant in high temperature fuel cells. 

Data on aerosol formation from irradiated automobile exhaust 5.193.23. 239 confirm the marked sensitivity to hydrocarbon type observed in individual hydrocarbon studies. Aerosol formation increases with the olefinic and aromatic fuel content. However, changes in mode of engine operation (acceleration, idle) and inorganic variables (sulfur dioxide, relative humidity) have a more pronounced effect on aerosol formation than change in fuel composition. ... 

Davies, J. H. Ewart, F. T. "The Chemical Effects of Composition Changes in Irradiated Oxide Fuel Materials, Jour, of Nuclear Materials 1971,41,143-155. 

The catalyst type also affects the quality of liquid fuel. The changes in the composition of liquids with temperature depend on the type of catalyst. The amount of naphtha fraction in the liquid fuel increased with temperature up to 435°C and then decreased (over... 

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