Uncertainties in the mercury mass balance in a coal-based igcc power plant (Puertollano, Spain)

Mercury (Hg) is a global pollutant that is subject to strict regulations to reduce anthropogenic emissions. The production of energy represents an important activity that leads to Hg emissions into the atmosphere. Of all the systems used, IGCC plants are the most promising for reducing Hg emissions, since it is possible to remove Hg from syngas prior to combustion. The aim of the present work was to evaluate the presence of Hg in the main streams of an experimental IGCC plant (ELCOGAS, Puertollano) in order to quantify Hg emissions and investigate the possibility of reducing them. The main streams of the system were sampled for three consecutive days and both the solids, i.e., raw material (coal and petroleum coke), fine and coarse slags, fly ash, sulphur, and the liquids, i.e., slag system, Venturi scrubber and saturator, were studied. The results show that an average of 12.9% of the Hg that enters the IGCC power plant is eliminated with solid waste and only 0.08% with liquid waste. There is still an average of 87.12% of Hg that is not accounted for in the mass balance and that could remain in the system and/or be eliminated in the streams that were not analysed. Although it is impossible to offer an explanation for the final fate of the Hg lost in the system based on the obtained results, the data suggest that sulphur by-products could be primarily responsible for the elimination of Hg from the syngas, and that a major proportion of Hg should be emitted via the chimney after the syngas combustion process. © 2021, Tech Science Press. All rights reserved.