Abstract: The invention relates to a vertical cylindrical furnace for the incineration of residual liquids, equipped with a rotary injector, said latter being more particularly constituted by a plurality of elements including an adjustable nozzle-holder. The adjustment of the angle of rotation of the nozzle-holder and the setting of the aperture of the nozzle make is possible, in one manoeuvre, to adjust the jet of liquid to be incinerated so that optimal use is made of the drying surface. Furthermore, the equipment of the furnace with a vault enables the drying surface to be increased with respect to a conventional cupola furnace. The invention finds particular application in furnaces for incinerating black liquor from paper mills.