Abstract: Device for treatment of a gas flow including at least one body (3), at least one first opening (4, 4?) for entrance of an incoming gas flow to the body (3) and at least one second opening (5, 5?) for the exit of an outgoing gas flow from the body (3). The body (3) is provided with a plurality of gas flow passages (11a, 11b) arranged to permit heat exchange between the gas flows in adjacent passages. The device has at least one distribution section (26, 26?) in communication with the first opening (4, 4?) and with the gas flow passages (11a, 11b) to distribute the incoming gas flow to the gas flow passages (11a, 11b), and at least one gas flow passage section (27, 27?) including the gas flow passages (11a, 11b), which passage section (27, 27?) primarily is adapted to permit heat exchange and to cause a conversion in the composition of the gas.