Heat-resistant silicon carbide refractories for gasification reactors

New high-efficiency gasification reactors with higher temperatures and pressures and with different temperature cycles than used previously require new types of refractory linings. Besides the oxide materials currently in use, SiC ceramics show great promise as refractories in the reducing atmospheres found in gasifiers. For this reason, recrystallised silicon carbide (RSiC) materials as well as RSiC materials infiltrated with either carbon or ZrO2 were prepared and the corrosion resistance in an acidic ash was investigated at 1300 °C for 100 h in a flowing CO/H2-containing Ar atmosphere. SEM, EDS and XRD analysis of the surfaces and cross sections of the corroded materials revealed the high stability of the modified RSiC materials. Two different mechanisms for corrosion protection were ob served. Carbon-infiltrated SiC showed nearly no wettability and very little infiltration of the molten ashes into the RSiC. In contrast, a small amount of slag infiltration was observed for zirconia-infiltrated RSiC materials. At a high degree of pore filling, good protection was obtained through reaction of the ash with zirconia. In all cases no or only minor attack of the SiC skeleton was observed. The results demonstrate the potential of the optimised materials for refractory applications in different environments.