Thermodynamic Investigation of Selected Metal Sulfates for Controlling Fouling and Slagging During Combustion

Today, aside from the solar, wind and hydropower, solid biomass, municipal solid wastes and industrial wastes are increasingly becoming important sources of renewable energy. However, fouling, slagging and corrosion that are associated with the combustion processes of these renewable resources threaten long-term operation availability and costs of power plants. Alkali metal elements in the biomass fuel and the ash fusion behavior are the two major origins contributing to slagging during high-temperature biomass combustion. Slags accumulated on superheaters, which decrease thermal efficiency, often constitute complex combination of K-Ca-Mg-sulfates. However, thermodynamic properties of these sulfates and their combined effect with other phases, which will help to solve the fouling, slagging and high-temperature corrosion related problems in biomass combustion processes, are not well known. In this work, thermal stabilities including solubility limits of selected phases and phase mixtures in the MgSO₄-K₂SO₄-CaSO₄ system are both critically reviewed and experimentally studied. The obtained results are presented and discussed.