Hydrogen and sulfur from hydrogen sulfide-IV. Quenching the effluent from a solar furnace

Solar thermochemical production of H₂ and sulfur from H₂S were studied, using a 4.2 m solar furnace as a source of process heat. We used two reactor configurations. The independent variables were temperature, feed rate and pressure. Hydrogen production rate, yield, and the quench fraction (fractional yield) were measured. High yields (of the order 0.5) and quench fractions (of the order 0.7) were obtained over a range of temperatures and feed rates. Yields were a monotonically increasing, almost linear, function of the temperature. The observations are rationalized by a kinetic model that concludes that gas phase reaction rates are too low to account for the observed yields; a good reactor should embody the heating of the feed stream in contact with a surface to facilitate decomposition of H₂S, and the product stream should be quenched in such a way as to minimize surface reactions. The reactors are described. Mullite, Al₂O₃, Fiberfrax and ZrO₂ are suitable materials of construction from a chemical standpoint. Mullite underwent some sintering, deformation and thinning in the hottest parts of the reactor, where it may have been exposed to high temperature excursions and some cracking, apparently due to thermal stress, where it came in contact with a separator.