A fluidized-bed reactor for producing hydrogen from methane by steam reforming includes a flow splitter that splits a dense-phase flow of a gas having entrained calcium oxide particles into a plurality of equal flow streams. The reactor also incorporates an orifice plate having at least one high-velocity, rocket-style impinging injector for injecting reactants into the reactor bed. The injector includes a central orifice extending perpendicularly through the plate, and one or more adjacent peripheral orifices that extend through the plate at such an angle that respective streams of reactants injected into the reactor bed through the peripheral orifices impinge on a stream of reactants injected vertically into the reactor bed through the central orifice. The injector cooperates with adjacent base-bleed orifices in the plate to provide a uniform distribution and rapid mixing of the calcium oxide particles with a steam/methane gas mixture across the entire bottom of the reactor bed.