GB1102826A - Process for the production of ethylene - Google Patents

Abstract

Ethylene is produced by a process in which the product of thermally cracking naphtha in the presence of diluent steam is first subjected to a fractionation in which a fraction comprising C4 and lighter hydrocarbons and hydrogen is separated and then this fraction is subjected to a second fractionation at low temperature in which either propylene and ethylene or ammonia and ethylene are used as refrigerants. The first fractionation zone is preferably operated to yield also an intermediate fraction comprising C5 and heavier components having an end point of 204 DEG C., which may subsequently be hydrogenated to gasoline, and a fuel oil residue, which may serve as quench oil or source of heat in the process. The light gaseous fraction is passed through a series of compressors, scrubbed with caustic, dehydrated, and introduced into the second fractionation zone. This zone comprises in series a demethanizer, de-ethanizer, ethylene fractionator and purifier, depropanizer and desirably a debutanizer, the effluent from the depropanizer or, if used, the debutanizer being withdrawn for further treatment as a gasoline product. The ethyleneethane mixture from the de-ethanizer is subjected to selective hydrogenation to remove acetylene and separated in the ethylene splitter into ethylene overhead and ethane bottoms, the overhead then being rectified to remove methane and yield a substantially pure ethylene stream. The hydrogenating gas used to remove acetylene is obtained from the demethanizer overhead and contains 80-90% mols. H2. The refrigerants may comprise ethylene and propylene products from the process.