a stepped , perforated tray is provided for increasing the available gas - slurry contact area in a flue gas desulfurization chamber . the tray redirects the horizontal flow upwardly through the tray for increased surface area and contact time with slurry for removing so x or other contaminants from a fossil fuel combustion flue gas before releasing the flue gas to the atmosphere . the tray is adaptable for use in vertical tower systems as well .