Abstract: An apparatus and process for promoting heterogeneous chemical and physical reactions in a gas stream using a vertical casing which is substantially liquid and gas tight having a gas inlet in the upper portion; means in the upper portion of the casing for introduction of reactant liquids and solids; a nozzle within the casing having an entry at the upper end in communication with the gas inlet and an outlet at the lower end, the entry having an effective cross-sectional area of about 2 to about 64 times the effective cross-sectional area of the outlet and the mean angle of convergence of the nozzle being about 8.degree. to about 18.degree.; means for removing liquid and particulate matter from the lower portion of the casing following desired reaction; and means for separately removing the gas from the lower portion of the casing. The apparatus and process of this invention is especially useful in providing a self-cleaning, non-clogging system for inducing high reaction kinetics.