Mercury is a toxic heavy metal that, once emitted or released, persists in the environment and circulates between air, water, sediments, soil and living creatures. Therefore, international governments and other authorities are taking measures to control mercury emissions from various sources. Despite many efforts, mercury remains a problematic pollutant in coal-fired installations in regards to differentiation of existing forms and their behavior in flue gas stream and purification units. Scientists try to understand its behavior in the flue gas and to capture it in one place, employing processes of adsorption, absorption, membranes or different catalysis. At the same time, researchers are also developing efficient and economically feasible technologies for mercury control. One such technology involves the capture of mercury in flue gases via gas-cleaning units through co-benefit application. Examples include, for instance, carbon injection in ESP, catalytic conversion in SCR unit, and absorption in a wet desulfurization scrubber. This paper outlines a mercury capture method developed in American and Polish laboratories and will present the pilot-scale research with emphasize on the mercury behavior in the slurry with and without any added reagents.