The present invention relates to an apparatus and method for mixing and atomizing a hydrocarbon stream using a diluent/dispersion stream. The apparatus comprises an inner conduit having an inlet for receiving the diluent/dispersion stream; an outer conduit having an inlet for receiving the hydrocarbon stream and an outlet for dispensing a mixture comprising the hydrocarbon and the dispersion/diluent streams; said outer conduit concentric to the inner conduit to define at least a first annular space and a second annular space; the first annular space being located downstream of the inlet of the outer conduit, said first annular space enabling formation of a thin film of the hydrocarbon stream between an outer surface of the inner conduit and an inner surface of the outer conduit; the second annular space being located downstream of the first annular space, said second annular space having a width greater than a width of the first annular space; and the inner conduit located at about the second annular space comprises a first set orifices disposed on a periphery thereof for dispensing a first portion of the dispersion/diluent stream into the thin film of hydrocarbon stream to cross-shear the thin film and form the mixture comprising the hydrocarbon and the dispersion/diluent streams.