Burners separated flame

This justifies all the work undertaken to arrive at fuel denitrification which, as is well known, is difficult and costly. Moreover, technological improvements can bring considerable progress to this field. That is the case with low NO burners developed at IFF. These consist of producing separated flame jets that enable lower combustion temperatures, local oxygen concentrations to be less high and a lowered fuel s nitrogen contribution to NOj. formation. In a well defined industrial installation, the burner said to be of the low NO type can attain a level of 350 mg/Nm, instead of the 600 mg/Nm with a conventional burner. 

If air is admitted into the heart of the flame in sufficient quantity, the luminosity5 suddenly disappears almost entirely, and a flame resembling that of. pure hydrogen results. Owing to the rapid combustion of the hydrocarbons, no luminous particles are separated, and the flame, being intensely hot, is a convenient one to employ for heating purposes, since it yields no soot when made to impinge upon a cold object. This is the principle of the Bunsen burner, the flame of which consists of two parts only, both of which are non-lummous. The inner... 

Both turbulent burners and premix burners have been used for atomic fluorescence. The premix burner is usually round in shape (a modification of the Meker-type burner), since this provides better geometry for fluorescence than does a slot burner. For an optimum detection limit, the premix burner is also shielded that is, an inert gas such as argon or nitrogen is directed in a sheath around the flame. This elongates the interconal zone and lifts the secondary reaction zone above the burner, separating it from the lower part of the interconal zone where the excitation beam passes. The result is less background emission and less noise, particularly in hydrocarbon flames like air-acetylene or nitrous oxide-acetylene. The premix burner, especially when shielded, appears to offer increased sensitivity over the turbulent burner. 

In separated burners, the flame is separated on both sides from atmospheric air with an inert gas flow (nitrogen or argon). These burners are employed for determination of refractory oxide elements and when atmospheric air causes interference to the measurement. 

Other burners separate the nebulization process and the flame by producing small liquid droplets in a nebulizing chamber before the sample enters the flame. Figure 10-12 shows this process in the Perkin-Elmer unit. 

High-temperature hydrocarbon combustion is a complicated chemical process. Nevertheless, it is possible to discern some features common to all fuels. To discuss them, it is convenient to separate the treatment of radical-poor and radical-rich situations. The former are characteristic of ignition processes, studied in the laboratory mainly by shock-wave initiation, while the latter are found in fully developed flames, studied in the laboratory in burner-stabilized flames. The elementary reactions important in these two situations are in part the same, but in part different. 

Flame treatment is predominantly used with articles of relatively thick section, such as blow moulded bottles, although it has been applied to polyolefin films as well. The most important variables in the process are the air-gas ratio and their rate of flow, the nature of the gas, the separation between burner and surface, and the exposure time. 

The total consumption type of burner consists of three concentric tubes as shown in Fig. 21.5. The sample solution is carried by a fine capillary tube A directly into the flame. The fuel gas and the oxidant gas are carried along separate tubes so that they only mix at the tip of the burner. Since all the liquid sample which is aspirated by the capillary tube reaches the flame, it would appear that this type of burner should be more efficient that the pre-mix type of burner. However, the total consumption burner gives a flame of relatively short path length, and hence such burners are predominantly used for flame emission studies. This type of burner has the advantages that (1) it is simple to manufacture, (2) it allows a totally representative sample to reach the flame, and (3) it is free from explosion hazards arising from unbumt gas mixtures. Its disadvantages are that (1) the aspiration rate varies with different solvents, and (2) there is a tendency for incrustations to form at the tip of the burner which can lead to variations in the signal recorded. 

The experimental data and the calculations involved in the determination of a reaction enthalpy by isoperibol flame combustion calorimetry are in many aspects similar to those described for bomb combustion calorimetry (see section 7.1) It is necessary to obtain the adiabatic temperature rise, A Tad, from a temperaturetime curve such as that in figure 7.2, to determine the energy equivalent of the calorimeter in an separate experiment and to compute the enthalpy of the isothermal calorimetric process, AI/icp, by an analogous scheme to that used in the case of equations 7.17-7.19 and A /ibp. The corrections to the standard state are, however, much less important because the pressure inside the burner vessel is very close to 0.1 MPa. 

Lastly, his experiments gave a view of the intensity of the light produced by the same quantity of gas in different burners, -when separately compared at the most advantageous height of the flame -.—... 

---