Testing, Identification, and Evaluation of Commercial and Advanced Experimental Materials and Coatings under Design Conditions Simulating Fuel Power Cycle Combinations. Task II. Evaluation of Heat Exchanger Materials for Use in Co

摘要

The Department of Energy established a program at Battelle's Columbus Laboratories to obtain engineering data on the durability of candidate heat-transfer and structural support materials operating in an atmospheric-pressure fluid-bed combustor burning high-sulfur coal in the presence of limestone as a sulfur oxide getter. The research was done in Battelle's 24-in. dia fluid-bed combustor operating at 1620 exp 0 F, 8 ft/sec superficial velocity, 25% excess air, and 0.1 lb/MM Btu SO sub 2 in the flue gas (1.2 lb/MM Btu SO sub 2 is EPA's new source standard for large combustion equipment). Candidate heat-transfer materials investigated were FSX 414, 310, 304, 18-18-2, 347 stainless steels, IN 671, P9, and two coatings featuring Al and Cr; they were tested for 10,500 and 1500 h at 1100 to 1580 exp 0 F. Candidate support structure materials studied were 304, 310, 347 stainless steels, aluminized 304 and 310 stainless steels, and Alloy 825, all tested at 1620 exp 0 F for 1080 h. Results indicated FSX 414 and 310 SS as best for heat-transfer service, with Alloy 825 and 310 SS best for support structures. The severe erosion of several 316 SS bed-cooling tubes demonstrated the vulnerability of metal to erosion at temperatures too low for formation of protective oxide scales. The results of a short supplemental program run with lower metal temperatures (400 to 910 exp 0 F) indicated a maximum in the observed metal loss (thickness) for several alloys, this occurring at 700 to 860 exp 0 F for 316 SS, 840 exp 0 F for E-Brite and 820 exp 0 F for P9. Individual particle velocity measurements in the bed showed 10% had velocities more than twice the superficial velocity with some five times that value. (ERA citation 05:001670)