An SNCR distribution grid for introducing a NOx reducing reactant into a flue gas flow. The grid is made of one or more elements (60) which are formed by fluid-cooled tubes (66) to which membrane pieces (68) are attached, preferably by welding, to form conduits (70) in between the tubes. The fluid-cooled tubes (66) may be cooled by water and/or steam and the distribution grid is disposed in the flue gas flow. To admit the reactant (62) into the flue gas, nozzles (72) are provided in the membrane (68) and the reactant is conveyed from a location external of the furnace or combustor enclosure, into the conduits (70) so formed, and thence out into the flue gas flow via the nozzles (72).