Materials Analyses of Ceramics for Glass Furnace Recuperators

摘要

The use of waste heat recuperation systems offers significant promise for meaningful energy conservation in the process heat industries. This report details the analysis of candidate ceramic recuperator materials exposed to simulated industrial glass furnace hot flue gas environments. Several candidate structural ceramic materials including various types of silicon carbide, several grades of alumina, mullite, cordierite, and silicon nitride were exposed to high-temperature flue gas atmospheres from specially constructed day tank furnaces. Furnace charging, operation, and batch composition were selected to closely simulate industrial practice. Material samples were exposed in flues both with and without glass batch in the furnace for times up to 116 d at temperatures from 1150 to 1550 exp 0 C (2100 to 2800 exp 0 F). Exposed materials were examined by optical microscopy, scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction, and x-ray fluorescence to identify material degradation mechanisms. The materials observations were summarized as: Silicon carbide exhibited enhanced corrosion at lower temperatures (1150 exp 0 C) when alkalies were deposited on the carbide from the flue gas and less corrosion at higher temperatures (1550 exp 0 C) when alkalies were not deposited on the carbide; alumina corrosion depended strongly upon purity and density and alumina contents less than 99.8% were unsatisfactory above 1400 exp 0 C; and mullite and cordierite are generally unacceptable for application in soda-lime glass melting environments at temperatures above 1100 exp 0 C. (ERA citation 05:005926)