Experience with an ODS high-temperature heat exchanger in a pilot-scale HiPPS plant

Abstract

A very high-temperature heat exchanger (HTHX) composed of MA754 alloy is being tested in a coal-fired slagging furnace system at the University of North Dakota Energy & Environmental Research Center. The HTHX was designed and built by the United Technologies Research Center. It is composed of three 6-foot-long by 2½-inch-od tubes which were originally protected from the products of combustion by ceramic panels. It was used to produce process air at 950°C and 150 psig over 2000 hours of testing with a variety of coals. For a short time, conditions of 1100°C and 100 psig were reached. In later tests the bare alloy tubes were exposed directly to the products of combustion which increased heat exchange coefficients by five times suggesting the HTHX cost would be only 1/10 as much as with the ceramic panels. Laboratory tests of the alloy exposed directly to the coal slag showed recessions of 5–10 mils per year at up to 1150°C. The data suggest that a cost competitive power system could be built employing this technology.