Effects of feed composition on boiler corrosion in waste-to-energy plants

Municipal solid wastes (MSW) typically contain plastic materials, leather, textiles, batteries, food waste and alkalis. These materials are sources of chlorine, sulfur, potassium, zinc, lead and other heavy metals that can form corrosive media during combustion of the MSW in waste-to-energy (WTE) facilities. Chlorides and sulfates, along with fly ash particles, condense or deposit on the waterwall surfaces in the combustion chamber and on other heat exchanger surfaces in the convection path of the process gas, such as screens and superheater tubes. The resulting high corrosion spots necessitate shutdowns and tube replacements, which represent major operating costs. The aim of ongoing research at Columbia University is to gain a better understanding of the effects of fuel composition, products of combustion, and chemical reactions that lead to the corrosion of metal surfaces in WTE boilers. The potential chemical reactions and their chance of occurrence were determined by means of thermochemical calculations of the respective equilibrium constants as a function of temperature and gas phase composition.