Burning biofuel in conventional power plants
Production of electricity is one of the main culprits in terms of emissions of gaseous and particulate pollutants. It has therefore been the target of a great deal of research. One proposal that has drawn attention is the combustion of biofuel in combination with coal in power plants. Since biofuel is a natural, cleaner, renewable source of energy, pollutant emissions are expected to decrease. The Energy, Environment and Sustainable Development Programme sponsored the TOMERED project, which brought together fifteen organisations, including ENEL, Italy's largest energy producer. During TOMERED, ENEL investigated how emissions of toxic metals, such as mercury, would be affected by introducing biofuel. The scope of their work involved determining how mercury emissions are perturbed by various in-furnace nitrogen oxide (NOx) controls, such as Over Firing Air (OFA) systems. Measurements of mercury concentrations at various stages in the combustion process were analysed by ENEL and have led to an improved understanding of the complex physical and chemical processes involved. The main finding was that toxic metal emissions are dependent on the amount of Unburned Carbon (UBC) present in the fly ash. The more UBC, the greater the potential for mercury removal via oxidation chemistry. Other factors such as residence time and the amount of cooling of the flue gas were also important. ENEL compiled the data, its analysis and their conclusions into a summary report that is available from the TOMERED consortium upon request. It marks an important step toward cleaner power plants.
