Sulfation of Condensed Potassium Chloride by SO₂

Abstract

The interaction between alkali chloride and sulfur oxides has important implications for deposition and corrosion in combustion of biomass. In the present study, the sulfation of particulate KCl (90−125 μm) by SO 2 was studied in a fixed bed reactor in the temperature range 673−1023 K and with reactant concentrations of 500−3000 ppm SO 2 , 1−20% O 2 , and 4−15% H 2 O. The degree of sulfation was monitored by measuring the formation of HCl. Analysis of the solid residue confirmed that the reaction proceeds according to a shrinking core model and showed the formation of an eutectic at higher temperatures. On the basis of the experimental results, a rate expression for the sulfation reaction was derived. The model compared well with literature data for sulfation of KCl and NaCl, and the results indicate that it may be applied at even higher SO 2 concentrations and temperatures than those of the present study. Simulations of sulfation of KCl particles with different size indicate that only for very small KCl particles, below 1 μm, a considerable in-flight sulfation is achievable at the short gas residence times typical of combustion systems.

Fundamental study of heterogeneous KCl sulfation under oxy‐fuel combustion conditions

“…The relationship between R s,d and the concentration of H 2 O are shown in Figure . During 120‐minute reaction, if H 2 O is involved in the reaction, the concentration of H 2 O does not affect the R s,d , which is consistent with the results under air combustion atmosphere reported by other researchers . Accordingly, the reaction order of H 2 O is 0.…”

“…Also, the activation energy value of present work is reasonable for a kinetically controlled process and can also exclude the formation of eutectic under the given experimental conditions. However, a change in reaction mechanism observed by other researchers, which is highly possible to result from a phase transition from a solid to a melt, was not detected in our present work in the temperature range 773 K to 923 K.…”

Effect of flue gas composition on deposit induced high temperature corrosion under laboratory conditions mimicking biomass firing. Part II: Exposures in SO2 containing atmospheres

“…Metal chlorides (especially FeCl 2 ) are known , and was also observed in Part 1 of this study to be able to induce low temperature melt formation. In accordance with increased generation of HCl reported in reference , such solid‐liquid transformation enhances the rate of the sulphation reaction because KCl sulphates faster in the molten phase. In addition, a better coverage of the sample is provided by the Cl‐containing melt, hence, permitting greater dissolution of alloying element by chlorination.…”

“…This reaction is responsible for the accumulation of K, S and O‐rich (K 2 SO 4 ) features around KCl particles and is in agreement with results from full‐scale studies . The mechanism behind this is properly discussed in literature .…”

“…A positive effect of SO 2 has been reported when SO 2 sulphates KCl aerosol particles in the vapour phase, before they condense on vulnerable metallic surfaces (i.e., ‘in‐flight’ sulphation) . However, heterogeneous (‘in‐deposit’) sulphation is considered in the following discussion because this corresponds to the experimental conditions in the present study. This reaction is responsible for the accumulation of K, S and O‐rich (K 2 SO 4 ) features around KCl particles and is in agreement with results from full‐scale studies .…”