Hi,
We plan to use low cement castable containing SiC (around 30%) for burner tip but worry about disintegration of SiC in presence of oxygen at high temperatures ( it could be more than 1250oC at burner tip). So replacing it by LLC basis corundum or bauxite is ok?
Regards
Of course, in an oxidizing atmosphere, at about 1000, SiC decomposes according to the scheme of 2SIC + 3O2 = 2SiO2 + 2CO, however the quartz SiO2 is fire resistance in itself (approximately1700) and the final fire resistance will depend on the composition of the remaining 70%. If this, for example, magnesian refractory, containing MgO, SiO2, reacted with him, can form a serpentinite MgO SiO2 with fireproof capability of about 1500 oC , or forsterite 2MgO SiO2 with fireproof capability of about 1900 oC . Bauxite is not desirable, because use is not enriched with bauxite may contain significant amounts of Fe2O3 and SIO2 which reduce refractoriness. Better use corundum with high-alumina cement, fire resistance of at least 1700 oC.
Thanks Mr.Silastman
the rest 70% of that castable is alumina (48%) and sillica (18%). So better we choose LCC basis corundum for burner tip and LCC - SiC for the body, right?
Dear phanminh !
Looking double diagram of SiO2-Al2O3. After disintegration of SiC your will have 56% SiO2 & 44% Al2O3. In such sistem liqud phase appears at temperature 1540 oC. Use LCC on base of corundum in burning zone and SiC in second zone with low content of O2 is the best solution.