Gas scrubber and use of the gas scrubber in melamine production

In a gas scrubber, a gas stream containing at least one sublimated substance is brought into contact with a liquid or melt stream which contains at least one thermally convertible substance and has a lower temperature than the gas stream. For intensive and intimate mixing of the gas stream with the liquid stream or melt stream, in the upper part of the gas scrubber there is provided a perforated plate having a plurality of holes each surrounded by a throttling rim. The throttling rim has a cone shape or a paraboloid of revolution ridge shape, the holes on the bottom of the perforated plate are surrounded by the edge of the reverse cone or reverse part of paraboloid of revolution mode, and above the perforated plate feeds are provided for the gas stream and the liquid or melt stream.