Abstract
Post-flame sulfation of gaseous sodium hydroxide (NaOH) and sodium chloride (NaCl) was investigated with optical in situ measurements
at 850 to 1475 °C. A multi-jet burner was used to generate
well-controlled combustion environments. The multi-jet burner also
enabled the separate feeding of the sodium species and SO2
to the combustion environment where the sulfation reactions occurred.
Concentrations of NaOH(g) and NaCl(g) were measured in the product gas
using broadband UV absorption spectroscopy to follow the degree of
sulfation. At 1475 and 1275 °C almost no sulfation occurred with an
initial NaOH(g) concentration of 20 ppm and SO2 concentrations between 0 and 150 ppm. At 985 °C, the NaOH(g) concentration decreased to less than 5 ppm with SO2
concentrations above 50 ppm and at 850 °C almost all NaOH(g) was
sulfated under these conditions. The experimental results for the
gas-phase sulfation of NaOH were compared to previous results for the
sulfation of KOH under the same conditions and the results were shown to
be similar for NaOH and KOH under these conditions. Sulfation of
NaOH(g) generally occurred to a more significant extent than the
sulfation of NaCl(g). At 1115 to 1475 °C, no sulfation of NaCl(g) was
observed. At the lowest investigated temperature, 850 °C, the NaCl(g)
concentration decreased from 20 ppm to 12 ppm after the addition of
150 ppm SO2. Chemical equilibrium calculations and kinetic
modeling using an updated kinetic model for the detailed Na-Cl-S
chemistry were compared to the experimental results. Above 1100 °C, the
system can be described by chemical equilibrium, implying that
equilibrium is reached in less than 100 ms. At temperatures below
1100 °C, the measured concentration indicated kinetic control. Under
these conditions, the kinetic model was in good agreement with the
experimental results for NaOH(g) but over-predicted the sulfation of
NaCl(g). The combined experimental data, chemical equilibrium
calculations and kinetic modeling of the present study support that
sulfation of alkali species can occur in the gas phase through
homogeneous reactions.
Original language | English |
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Article number | 126337 |
Journal | Fuel |
Volume | 332 |
Number of pages | 8 |
ISSN | 0016-2361 |
DOIs | |
Publication status | Published - 2023 |
Keywords
- Sodium sulfation
- Alkali sulfation
- UV absorption spectroscopy
- Chemical kinetic modeling