A wet scrubber for absorbing oxides of sulphur from contaminated gas comprises an upright housing having an inlet for contaminated gas adjacent at the lower end and an outlet for clean gas adjacent the upper end, a plurality of vertically stacked, successive intense wet scrubbing zones in said housing between said inlet and outlet, each of said zones comprising a horizontal array of elongated, parallel, spaced apart rod like elements which substantially reduce the total flow cross section available to the gas moving therebetween to a value less that of the cross section above and below the array, upper spray means adjacent an upper of said scrubbing zones for distributing into said gas finely divided droplets of scrubbing liquor, which liquor comprises a limestone slurry, said liquor flowing in a downward direction and cascading countercurrent to the upward gas flow through each successively lower scrubbing zones, a high velocity particulate collector stage in said housing between said inlet and a lower of said wet scrubbing zones comprises baffle means across said housing having a flow restricting opening therein and lower spray means for directing scrubbing liquid into the high velocity gas flowing through said opening in a concurrent direction therewith.

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