The fate of chromium has been studied in laminar hydrogen and ethene diffusion flames. Nitrogen was added in order to vary the flame temperature in hydrogen flames. Ethene flames were used in order to investigate the potential for interaction between the soot aerosol that is formed in these flames and the chromium aerosol. Two sources of chromium compounds were introduced: chromium nitrate and chromium hexacarbonyl. Samples of the vapor and particle phases of chromium compounds emitted from the flames were collected by an isokinetic dilution sampling probe. The amounts of Cr(VI) and total Cr were determined by a spectrophotometric method and by X-ray fluorescence spectrometry, respectively. Results of Cr(VI) analysis in the hydrogen flame showed that the emission of Cr(VI) from the undiluted H2 flame was more than 10 times larger than in the 50% H2/50% N2 flame on a mass basis. Approximately 50% of the total chromium emission from the pure H2 flame was in the form of Cr(VI). This fraction dropped to about 1% in the heavily diluted H2 flames. The relative amount of Cr(VI) in the vapor phase decreased by adding N2 to the flame. The results indicated that flame temperature is an important factor with regard to emission of Cr(VI). In the ethene flame, the fraction of Cr(VI), which was found in the condensed phase, decreased slightly with increasing soot levels. It was not possible to detect chromium as a separate particle phase within the soot matrix.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Fluid Flow and Transfer Processes
- Physical and Theoretical Chemistry
- Energy Engineering and Power Technology
- Fuel Technology
- Mechanical Engineering