Sensing of sulfur in molten metal using strontium β-alumina

Abstract

A sulfur sensor based upon strontium b-alumina solid electrolyte was developed and tested in molten iron. The strontium b-alumina electrolyte was fabricated using an injection molding process and optimized for thermal shock resistance and toughness by incorporating up to 20 wt pct partially stabilized zirconia. A mixture of molybdenum and molybdenum sulfide was used as the reference electrode, while SrS, allowed to form in situ during the sensing of sulfur, formed the auxiliary electrode. The sensor behavior in terms of response time, lifetime to failure, and possible reaction mechanisms is discussed in this article. The results were in very good agreement with combustion analysis by conventional LECO.

Synthesis and Properties of Strontium β‐Alumina

“…However, a similar calcium‐based magnetoplumbite, known as hibonite, has already been identified by Kumar and Kay 11,12 as a potential electrolyte material and has been applied in galvanic cells 13,14 . A new gas sensor based upon magnetoplumbite for measuring SO 2 has been developed by Wang and Kumar 16 The strontium β‐alumina, reported in this study, has a low ionic conductivity compared with ion‐exchanged samples as described by Dunn and Farrington 1 and polycrystalline samples reported by Yamaguchi et al 6 and Schaffer et al 7 However, the conductivity is more than adequate for developing sulfur sensors in liquid iron operating at elevated temperatures 15 and for galvanic cells 17 . By using thick films of Sr β‐alumina, it has been possible to develop gas sensors that could be operated at a relatively low temperature of 950 K 18…”

An electrochemical sulfur sensor based on ZrO2(MgO) as solid electrolyte and ZrS2+ MgS as auxiliary electrode

“…The sensors took longer to equilibrate than commercial oxygen sensors used in steelmaking, and this was possibly due to the fact that the auxiliary electrode had to come to equilibrium with the sulfur in the melt, a species not present in the electrolyte, while the oxygen sensors come to equilibrium with oxygen that is mobile species in the electrolyte. Furthermore, in steelmaking, the temperatures are above 1850 K, while in liquid iron, the temperatures are lower at 1500-1700 K [13].…”

Corrosion of MgO-PSZ in a HF solution and its effect on synthesis of an auxiliary electrode for high-temperature sulfur sensors

“…This may be because the auxiliary electrode has to come to equilibrium with sulfur in the liquid iron while the oxygen sensors come to equilibrium with oxygen, which is a mobile species in the electrolyte. Furthermore, in steelmaking, the temperatures are above 1850 K, while in liquid iron, the temperatures are lower at 1550 K [15].…”