Ash separators and flue gas desulphurisation. That keeps the stack from having grey/brown or yellow fumes, which would contain the ash as solids to drop out or the sulphur dioxide that contributes to acid rain.
Cooling towers are of course only water vapour, so as long as the visible emission of the central thin stack on a coal power station is white, it’s running clean.
Ash separators and flue gas desulphurisation. That keeps the stack from having grey/brown or yellow fumes, which would contain the ash as solids to drop out or the sulphur dioxide that contributes to acid rain. Cooling towers are of course only water vapour, so as long as the visible emission of the central thin stack on a coal power station is white, it’s running clean.