Materials testing at the Hanna IV in situ coal gasification experiment site during FY 1978

Candidate structural alloy specimens were exposed for about 800 hours to the direct product gas stream from the Hanna IV underground coal gasification experiment. When the specimens were removed from the line, they were coated with high-sulfur deposits from the product gas. A chemical analysis and the physical appearance of the coatings suggest that they are mixtures of condensed hydrocarbons, coal char, coal ash, and mineral particles from the overburden. Attack on the specimens was primarily corrosion rather than erosion. Mean penetration rates expressed in millimetres per year (mm/y) and mils per year (mpy) were calculated from weight loss data. Microscopic examination revealed some areas of rather severe local attack on all alloys tested. There was no consistent difference in the amount of material removed from specimens with welds and those without welds. Specimens exposed at 45/sup 0/ to the product gas flow all had surface dents from impacting particles while parallel specimens had none. Energy-dispersive x-ray and Auger electron spectra indicate that the few particles of deposits and/or corrosion products still clinging to the specimen surfaces after cleaning were oxides, rather than sulfides, with significant contents of aluminum and silicon in addition to iron.