A scrubber for removing pollutant compounds from a gas stream. At least one gas channel introduces the gas stream to a lower portion of the scrubber. An inlet chamber directs the gas stream upwards to form a vertical gas stream. A constriction section has a vertical axis of symmetry and includes a centrally arranged venturi nozzle, and is above and in flow connection with an upper end of the inlet chamber for accelerating the vertical gas stream. A reaction chamber is arranged above and in flow connection with the constriction section. A reagent in the reaction chamber converts pollutant compounds in the gas stream to reaction products. A discharge channel in flow connection with the reaction chamber discharges gas and particles including the reaction products from the reaction chamber. A particle separator separates particles from the gas. A return channel recycles a portion of the particles to the reaction chamber.