A device providing for an overheated liquid to be sprayed in very fine droplets at a very high speed, comprised of a nozzle body followed by a mixer head and several injectors opening onto a divergent speed attainment nozzle. Fittings adjust the exit section of the nozzle by adding a profiled core that may slide on the axis of the divergent nozzle and enabling, depending on its position, the exit section of the nozzle to be adjusted to maintain a maximum ejection speed of sprayed droplets. The device is particularly applicable to the chemical and energy industries.