Effects of slag compositions on the rate of methane-steam reaction

For the effective heat recovery from molten slag by utilizing a chemical reaction, rates of the methane-steam reaction on the slag surface were studied for thirteen slag samples, in which effects of mass ratio of CaO to SiO₂ (CaO/SiO₂ ratio), and concentrations of wustite (FeO) and sulfur in slag on the reaction rate were systematically examined in the slag temperature range from 1473 to 1823 K. The results showed that the higher CaO/SiO₂ ratio, meaning the weaker network structure of molten slag, gives rise to the higher rate of methane-steam reaction. In contrast, the FeO addition to slag brings about the lower reaction rate than that for the slag without FeO, indicating the inhibitory effect of FeO on the reaction. The higher FeO concentration proportionally provides the stronger inhibitory effect over the slag temperature of 1773 K, while it is independent on both of the slag temperature and the FeO concentration under the temperature of 1673 K. The results also revealed that the sulfur contained in slag has the inhibitory effect on the methane-steam reaction, which is much larger than the equi-mass of FeO over 1673 K. This inhibitory effect of sulfur increases with increasing the sulfur concentration from 0.5 to 1.0 mass%, whereas it is insignificantly enhanced by the further increase in the sulfur concentration.