Ashing conditions

The data for copper indicates that contamination may have come from the platinum crucibles since similar concentration trends were noted for both covered and uncovered crucibles. Under the chosen ashing conditions, vanadium and molybdenum were apparently consistently volatilized. 

Ashing temperature, heating rate, and furnace ventilation have an important influence on sulfur trioxide retention thus, observance of the prescribed ashing conditions can be critical. Sulfur in ash as determined by these methods cannot be strictly related to the sulfur oxides retained in ash produced under the conditions of combustion in boiler furnaces or other commercial combustion processes. 

Losses from volatilization of the analyte can be minimized by restricting the temperature at which ashing takes place. For determination of lead, copper, zinc, cadmium, and iron in foodstuffs, for example, good recoveries of the analytes were obtained by heating the samples slowly to 450°C and holding this temperature for 1 hour. A collaborative study showed no significant losses of the analytes under these ashing conditions [94],... 

Gasifier Type Oxidant Coal Feed Method Exit Gas Temperature (°C) Operating Pressure (Bar) Ash Condition... 

Low temperature ashing techniques were employed to reduce the oxidation and decomposition of the minerals which would occur under normal ashing conditions. Mineralogical analyses were performed using X-ray powder diffraction, infra-red spectroscopy, optical petrography, and scanning electron microscopy. Elemental determinations were performed using atomic absorption spectroscopy. 

According to the analysis and consideration detailed above for photoinitiated polymerization, it may now be concluded that Rp or [M ] can be varied by varying the frequency of blinking. Under otherwise comparable conditions, the average rate Rp) at different ashing conditions with the same k is related to the steady-state rate Rp)s as... 

An analysis of the diagram shows that the HTW gasifier and the INQ concept are able to follow the elevated cold gas efficiency area due to its operation at dry ash conditions. Furthermore, they can approach the cold gas efficiency maximum. 

Because of its operation at dry ash conditions, the HTW gasifier shows the lowest losses with increasing ash content However, the poor carbon conversion limits its performance significantly. 

Care must be taken over the quantification of inorganic flame retardants, since some of them (e.g., antimony trioxide) can react with the organic flame retardant present, or break down to produce volatile products, under quantitative ashing conditions, and during analysis by thermal techniques such as TGA. A good initial approach is a semi-quantitative elemental analysis by XRF, to see which types are present. Accurate quantifications can then be obtained by precise elemental determinations. 

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