Features of alkaline corrosion of fireclay bricks used in biomass boilers

Abstract

Aluminosilicate refractories are not resistant to alkali corrosion that occurs when biofuels are burnt. Due to the chemical corrosion of the refractory materials, the durability of internal structures (lining) is significantly reduced, unplanned shutdowns of biofuel plants occur, and additional funds must be allocated for repairs. And these risks increase even more when biofuel ash contains a higher amount of potassium and sodium, which can increase impermissibly (more than 10 times) when preventive measures against biofuel freezing, such as alkaline salts, are used. This practically inevitably leads to corrosion of aluminosilicate materials and rapid disintegration of the lining made of such materials. This paper will examine two different classes of refractory bricks and their resistance to alkaline corrosion. One brick is classified as a low-Al2O3 refractory brick and the other as a higher grade, high-Al2O3 refractory brick. Two different reagents (potassium carbonate and sodium carbonate) and their mixture were used in alkaline resistance tests performed by the crucible method. Furthermore, X-ray studies and thermodynamic calculations were performed using the FactSage programme package.