Premix burners advantages

The design of the premix burner shown in Figure 10 also presents a number of other advantages and disadvantages as compared with the total consumption type. The flame is not very luminous, and flicker and turbulence are quite low, so that for many elements the flame contributes no apparent noise to the output (Figure 8). Furthermore, there is rather little dependence of absorption upon sample flow rate. This is of benefit in two ways. First, the length of sample capillary, and its depth of immersion in the solution, are not very critical, so that samples can be aspirated from any vessel. For total consumption burners, by contrast, Petri dishes or very small sample containers are often recommended. Second, viscosity interferences caused by variations in sample concentration are minimized, though not eliminated. In the Perkin-Elmer burner, when the sample flow rate is cut by a factor of 2, absorption is reduced by approximately 4%. 

To carry out the analysis in the best manner possible, a study was conducted on the various hollow cathode lamps, burners, and optical systems to assess them as to their advantages and disadvantages in the analysis of water. Particular emphasis was given to the comparison of the total consumption and premix burners (6, 7). The results are presented here in the form of conservative values attainable of sensitivity and precision, and a discussion of the differences noted. 

To summarize the major advantages and disadvantages of the nonpremix and premix burners, the advantages of the turbulent-flow burner are ... 

The most commonly used flame for atomic-absorption measurements is the air-acetylene flame combined with a premix burner. Although its advantages are many, certain limitations affect its use for some elements. Metals such as molybdenum, tin, and some alkaline earths are only partially atomized in this flame. Elements that form refractory compounds, including silicon, aluminum, and vanadium, are not appreciably atomized at all. In general, this can be attributed to the tendency of these elements, when heated in the flame, to form refractory oxides that are not decomposed at the temperatures available. 

Compare the advantages and disadvantages of the total-consumption burner and the premix burner in atomic-absorption spectroscopy. 

Flashback is more likely with an acetylene-oxygen mixture than with any of the other fuel-oxidant combinations in common use. Flame propagation in this system is at 1130cm/sec. This imposes severe limitations on the use of acetylene and oxygen with premixed burners. The relatively low flame propagation rate of nitrous oxide and acetylene (180cm/sec) is a definite advantage for the system. 

In addifion fo fhe fwo above mentioned categories there is their combination (i.e., part of the fuel and oxidizer is premixed prior to entering the combustion space and the rest of fhe fuel and oxidizer are supplied unmixed info fhe combustion chamber by separate inlets). One of fhe biggest advantages of this type of burner is in ifs high flame stability. 

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