Flue gas from coal-fired power plants contains mercury, which is partly captured by state-of-the-art wet flue-gas desulphurization units. The oxidation of the noble heavy metal is mandatory for that and takes place up-stream from the unit, mainly caused by halogens. The gypsum produced in wet desulphurization is industrially re-used, thus preferably no mercury or carbon should be bound into it. Unburnt carbon from the combustion and carbon-based sorbents show highly efficient adsorption capacities regarding mercury. A process for mercury abatement based on that, the addition of activated carbon to the desulphurization plant, is focused upon here. Since mercury is a toxic element in most of its compounds, it has to be captured in the following processes and led to an appropriate sink. For economic reasons, a two-staged waste-water treatment is advantageous here, which requires the knowledge of systematic adsorption and desorption of mercury.
Within the scope of this work, large-scale tests performed at three different power-plant units in Germany and the United States are utilized to research three combined process steps. These steps are the oxidation of mercury by adding dissolved bromide salt to the combustion, the sorption of mercury in the desulphurization plant and the desorption of mercury in slurry. The interactions between the present and the tested novel processes are investigated in lab, pilot-scale and fullscale here for the first time. A treatise of the numerous concurrent relevant chemical and physical mechanisms gives the basis of the work.
The test results are analyzed in context with some further observations that were considered as highly relevant and found for the first time to some extent and finally discussed in context with the tested processes.