It is assumed that the ACI, FGD, and SCR would not be necessary at a single unit because of the high mercury removal efficiencies expected through combination of FGD and SCR.
Mercury is very dangerous, and needs to be removed as fast as possible. 
mnli hypothesis: Mercury is very dangerous, and needs to be removed as fast as possible.  premise: It is assumed that the ACI, FGD, and SCR would not be necessary at a single unit because of the high mercury removal efficiencies expected through combination of FGD and SCR.