Reactions between ash and ceramic lining in entrained flow gasification of wood : exposure studies and thermodynamic considerations

Gasification of biomass in the entrained flow process requires temperatures above 1000°C and pressures above 20 bar. Together with the ash forming elements, a harsh environment is created inside these reactors and degradation of construction material is likely to occur. This will lead to unplanned stops and increased maintenance work resulting in economic loss. In this work, two refractory materials (63 and 83 weight percent alumina) were exposed to synthetic ash composed of K2CO3, CaCO3 and SiO2 to study chemical attack on and interactions with the refractory materials. The exposure went on for 7 days in 1050°C and CO2­atmosphere in a muffle furnace. It was found that potassium (K) is the most active element in attack of the refractories and is transported fastest in the material. A melt composed of K, Ca and Si was formed that prevented penetration of K but it also dissolved aluminum from the refractory materials. X­ray diffraction showed that the crystalline phases leucite, kalsilite, kaliophilite, K(2­x)Al(2­x) SixO4 and wollastonite had formed. Formations of new phases in refractories will cause stress and eventually failure within refractories.Godkänd; 2013; 20130817 (ohmmar