An application of the electrochemical sulfur sensor in steelmaking

A novel electrochemical sulfur sensor using Laβ-Al2O3 as solid electrolyte and La2O2S+La2O3 as auxiliary electrode material has been developed. It can be applied not only in molten iron but in molten steel as well, where the oxygen concentration is in the range from 2.1 to 51.5 ppm, because a more stable auxiliary material of La2O2S was used in the sensor. The EMFs of the sensors when measuring sulfur in liquid metal containing oxygen over the range from 2.1 to 51.5 ppm have shown fairly good reproducibility and sensibility to the sulfur activities in the melt. The influence of the oxygen activity in molten metal on the lower limit of measuring sulfur activity with the sensor is also discussed. The lower limit of measuring sulfur activity is dependent on oxygen activity in the melt, i.e. a[S]=3.84a[O].