Abstract: In a process wherein an acrylonitrile polymerization slurry made up of polymer solids, unreacted monomers and water is passed downward through a column containing a plurality of perforated trays for the purpose of removing unreacted monomers from the slurry, the improvement comprising: sequentially applying sprays of water to that portion of the inner wall of the column above each of the trays, with each such wall portion being sprayed by at least two sprays positioned to substantially cover that wall portion and with the sprays being operated intermittently in such a sequence that only one of the sprays is in operation at a given time and all sprays in the column are operated within a period of less than about 15 minutes, preferably less than five minutes. In the sequence, each spray is operated for a time period of at least about five seconds.