Hot Corrosion Resistance of Aluminosilicate Refractories – Comparative Tests in the Secondary Combustion Chamber of a Hazardous Waste Incinerator
1 BONY SA – Produits Réfractaires, 42001 SaintÉtienne/France
2 SARPIVEOLIA, 78520 Limay/France
3 CEMHTI CNRS UPR 3079, Université d’Orléans, 45071 Orléans/France
4 LGF CNRS UMR 5307, MINES SaintÉtienne, 42023 SaintÉtienne/France
Revision 15.01.2018, 21.01.2018
Volume 10, Issue 2, Pages 57 - 62
Abstract
This paper presents the alkali and sulphur vapour corrosion resistance of aluminosilicate refractories under industrial conditions. Aluminosilicate refractory samples with Al2O3 contents ranging 42 – 90 mass% were exposed for 8 months to the corrosive atmosphere in the secondary combustion chamber (gas temperature approx. 950 °C) of a hazardous waste incineration facility. After the exposure, the samples were analysed in the laboratory regarding porosity and mineralogical changes. The test results show that degradation is caused by hot corrosion, specifcally by condensed thenardite (Na2SO4). Free silica, largely accessible in freclay bricks, is the frst phase that reacts with thenardite. The reaction generates liquid natrosilite (Na2Si2O5). This low melting phase leads to deformation and creep of hotter brick parts. In a next step, natrosilite reacts with mullite forming albite (NaAlSi3O8). Simultaneously, thenardite reacts directly with mullite forming nosean (Na8Al6Si6O28S). In order to better withstand the hot corrosion mechanism, refractories should contain as little silica as possible.
Keywords
alkali attack, sulphur, mullite, hazardous waste incinerator
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