The disclosure provides methods of operating a slagging gasifier using a carbon feedstock having a relatively high V.sub.2O.sub.5 to SiO.sub.2 ratio, such as petcoke. The disclosure generates a combined chemical composition in the feed mixture having less than 25 wt. % SiO.sub.2, greater than 20 wt. % V.sub.2O.sub.5, and greater than 20 wt. % CaO. The method takes advantage of a novel recognition that increased levels of SiO.sub.2 tend to decrease dissolution of the V.sub.2O.sub.3 which forms under the reducing conditions of the gasifier, and utilizes the CaO additive to establish a chemical phase equilibria comprised of lower melting compounds. The method further provides for control based on the presence of Al.sub.2O.sub.3 and FeO, and provides for a total combined chemical composition of greater than about 5 wt. % MgO for use with refractory linings comprised of MgO based refractory brick.
The United States Government has rights in this invention pursuant to the employer-employee relationship of the Government to the inventors as U.S. Department of Energy employees and site-support contractors at the National Energy Technology Laboratory.