Interaction of High Al2O3 Refractories with Alkaline Salts Containing Potassium and Sodium in Biomass and Waste Combustion

Abstract

Utilization of challenging fuels, such as biomass residues and waste-derived fuels, may lead to problems with refractory corrosion. Alkalis and chlorine in such fuels can lead to the formation of low melting deposits and slags on the refractory lining of boilers during combustion. This may cause excessive wear, possibly limiting the service lifetime of the refractories. In this work, the attack of alkali salts to high alumina refractories was studied. The refractory was exposed to four pure salts (K2CO3, K2SO4, Na2CO3, and Na2SO4) and one synthetic ash (K2CO3–KCl). The refractory was exposed to the salts at 700, 800, and 900 °C for 168 h. The penetration of potassium into the refractory was determined from horizontal line scan analyses of the sample cross section using scanning electron microscopy with energy-dispersive X-ray analysis. Detailed information on alkali infiltration was obtained by using the Xphase spectral imaging software. Additionally, X-ray diffraction analyses were made on cross sections...