Spray nozzles

A nozzle for discharging first and second fluids in a spray pattern into a vessel, such as oil and steam in a catalytic cracking unit, includes various configurations for preventing erosion of the outlet portion of the nozzle that otherwise might be due, for example, to contact with a catalyst or other predetermined substance. In one such nozzle, the exterior surface of the outlet portion substantially conforms to the internal contour of the vessel. In another such nozzle, the outlet portion defines a plurality of substantially concentric, substantially elliptical-shaped outlet apertures. In another nozzle, the outlet portion is formed of ceramic and is connected to the inlet portion by a metal connector. In another nozzle, the outlet portion defines a plurality of apertures angularly spaced about a peripheral region of the outlet portion for discharging a substantially flat fan spray pattern, and a second outlet portion extending along an upstream portion of the outlet portion for discharging at least part of its spray to prevent any catalyst from contacting the downstream surfaces of the outlet portion.