Some studies on a solid-state sulfur probe for coal gasification systems

Measurements on the solid electrolyte cell (Ar + H2 + H2S/CaS + CaF2 + (Pt)//CaF2//(Pt) + CaF2 + CaS/H2S + H2 + Ar) show that the emf of the cell is directly related through the Nernst equationto the difference in sulfur potentials established at the two Ar + H2 + H2S/electrodeinterfaces. The electrodes are designed to convert the sulfur potentialgradient across the calcium fluoride electrolyte into an equivalentfluorine potential gradient with the aid of the reaction, CaF2(s) + ½S2(g) → CaS(s) + F2(g). The response time of the probe varies from approximately 9 hr at 990°K to 2.5 hr at 1225°K. The conversion of calcium sulfideand/or calcium fluoride into calcium oxide should not be a problem inanticipated commercial coal gasification systems. Suggestions are presentedfor improving the cell for such commercial applications