Sodium/sulfur chemical behavior in fuel-rich and -lean flames
- Univ. of California, Santa Barbara, CA (United States)
An experimental and analytical program examining sodium/sulfur chemistry has been conducted in a series of fuel-rich and -lean H{sub 2}/O{sub 2}/N{sub 2} flames, with and without added sulfur, and covering a wide range of temperatures and stoichiometries. Fluorescence measurements of OH and Na downstream profiles and sodium line reversal temperatures provided a broad data base for kinetic modeling. Analysis indicated NaSO{sub 2} to be the only significant sodium/sulfur product formed in the lean flames. Even so, its concentrations remain an extremely small fraction of the total sodium. The more important perturbation of the distribution of sodium over its molecular forms results from the catalytic effect of sulfur on the flame radical concentration levels rather than from the formation of additional species. A bond dissociation energy of D{degrees}{sub 0}(Na-SO{sub 2}) = 197 {plus_minus} 20 kJ mol{sup {minus}1} is derived assuming a nonplanar structure of 210 {plus_minus} 20 kJ mol{sup {minus}1} if the molecule is planar. NaOS is dominant in the rich flames, coupled with small contributions from NaSO{sub 2}, NaSH, NaS, and NaS{sub 2}. Together, these can constitute from about 10 to 20% of the total flame sodium and do represent in this case an enhancement of molecular formation. Preliminary data in fuel-rich C{sub 2}H{sub 2}/O{sub 2}/N{sub 2} flames are consistent with this model. This further illustrates the general insensitivity of alkali-metal chemistry to fuel type. When coupled to other available data, the low levels of NaSO{sub 2} estimated for the present fuel-lean flames tend to suggest that Na{sub 2}SO{sub 4} formation in the gas phase appears to be unlikely under most practical conditions. However, this still cannot be rigorously ruled out for all situations and requires further study to resolve the critical dependences that control high-temperature Na{sub 2}SO{sub 4} corrosion. 59 refs., 10 figs., 3 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG21-86MC23135
- OSTI ID:
- 555019
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 2 Vol. 96; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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