Burner Assembly

The burner is mounted on an adjustable stage that allows the entire burner assembly to move horizontally and vertically. Horizontal adjustment is necessary to ensure that the flame is aligned with the instrument s optical path. Vertical adjustments are needed to adjust the height within the flame from which absorbance is... 

One problem with the analysis of salt samples is their tendency to clog the aspirator and burner assembly. What effect would this have on the analysis ... 

Clogging the aspirator and burner assembly decreases the rate of aspiration, decreasing the analyte s concentration in the flame. The result is a decrease in the signal and the introduction of a determinate error. 

Figure 4.1.2 is a photograph of a coimterflow burner assembly. The experimental particle paths in this cold, nonreacting, counterflow stagnation flow can be visualized by the illumination of a laser sheet. The flow is seeded by submicron droplets of a silicone fluid (poly-dimethylsiloxane) with a viscosity of 50 centistokes and density of 970 kg/m, produced by a nebulizer. The well-defined stagnation-point flow is quite evident. A direct photograph of the coimterflow, premixed, twin flames established in this burner system is shown in Figure 4.1.3. It can be observed that despite the edge effects.

A backyard barbeque grill contains a 20-lb tank of propane. The propane leaves the tank through a valve and regulator and is fed through a 1/2-in rubber hose to a dual valve assembly. After the valves the propane flows through a dual set of ejectors where it is mixed with air. The propane-air mixture then arrives at the burner assembly, where it is burned. Describe the possible propane release incidents for this equipment. 

Flame speeds were measured on a nozzle burner. Fuel and air were metered and mixed in the same manner as in the preflame studies. The entire gas supply line and burner assembly were electrically heated to avoid condensation of fuels and additives. The burner was surrounded by a wider tube to prevent ambient air from influencing the flame. The flame speed was determined from the height of the flame cone. 

By having a surge tank attached to the strand burner, only a very slight pressure rise occurred as a result of the burning of the strand. Consequently, burning occurred at essentially constant pressure. This method has also been adopted for use with strands which have been cut from sheet proplnt and even strands sliced from sections of cast grains. Fig 1 shows a typical strand burner assembly... 

Longer-life burners and burner assemblies able to handle a wider variety of feedstock. 

For testing, the Mod 2 burner is housed within a heavily walled pressure vessel which also serves as a plenum chamber for the preheated inlet air supply. See Ref. 16 for a description of the test facility. The burner assembly is shown schematically in Figure 2 and is designed to use 100% of the air flow in the combustion process. Thus, air film cooling and air dilution which are normally used in an engine combustor are omitted. In this way, combustion effects from air injection are avoided for the concept evaluation. The cylindrical combustion chamber is water cooled, as are the sonic exhaust nozzle and gas sample probe. 

Fig. 3 Flame housing of IL 943 flame photometer a) sodium filter, 589 nm b) potassium filter, 776 run c) lithium filter, 670 nm d) cesium filter, 852 nm e) ignition detector f) burner assembly g) rubber gasket h) spark electrode i) ignition coil wire j) chimney. (Courtesy of Instrumentation Laboratory, Inc.)...

To be detected by AAS, the analyte must be presented to the optical beam of the instrument as free atoms. The process of converting analyte ions/molecules, dissolved in a suitable solvent, to gaseous atoms is accomplished by the nebuliser flame assembly. The nebuhser (from the Latin nebula meaning cloud) creates an aerosol (a fine mist) of the hquid sample which is mixed with an oxidant gas and a fuel gas (to support the flame combustion). The mixture is ignited above the burner assembly. The liquid droplets are desolvated, the resulting microcrystals are melted and vaporised and finally the gaseous products are thermally dissociated to produce free atoms. The combustion speed of most flames is such that the conversion from liquid droplet to free atoms must be accomplished within a few milhseconds. 

A burner head, typically with a single slot (10 x 0.2 cm), is aligned along the axis of the optical beam from the radiation source. The nebuliser/burner assembly is mounted on a platform which provides for positional adjustment in both the vertical and horizontal planes. The optimal height of the optical beam above the burner slot varies with each analyte element (and somewhat with the sample composition) is established experimentally for each standard solution. An impressive graphic presentation of the spatial distribution of analyte atoms of sodium, calcium, or molybdenum in an air/C2H2 flame (under identical operating conditions) has been presented by Rann and Hambly Anal. Chem. 37, 880, 1965). 

EN 303-3 Gas boilers with forced draught burners assemblies EN 303-4 Boilers with forced draught burners oil... 

Configuration (boilers, combi-boilers, boiler-burner assemblies, and separate burners)... 

Figure 6-10. Burner assembly showing stagger jets and insulation to protect lines from flame impingement.

The entire burner assembly—except for the flameholders—should be insulated to withstand direct flame impingement. The position of the flameholders and burner lines relative to the bottom of the stack is critical for proper operation. These dimensions are shown in Figure 6-11. 

Flame OES can be performed using most modem atomic absorption spectrometers (discussed in Chapter 6). No external lamp is needed since the flame serves as both the atomization source and the excitation source. A schematic diagram of a flame emission spectrometer based on a single-beam atomic absorption spectrometer is shown in Fig. 7.2. For measurement of the alkali metals in clinical samples such as serum or urine, only a low-resolution filter photometer is needed because of the simplicity of the spectra. The filter photometer is discussed in Section 7.1.1.2. Both instmments require a burner assembly, a flame, a wavelength selection device, and a detector. 

The central component of a flame emission spectrometer is the burner assembly. The assembly has a device to nebulize the sample and then introduces the sample aerosol into the flame. In the flame, free atoms are formed and then excited, which causes them to emit radiant energy. For analytical purposes, it is essential that the emission intensity be steady over reasonable periods of time (1-2 min). The Lundegardh or premix burner is the most commonly used and is depicted in Fig. 6.8(a). 

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