Process and device for catalytic dehydrogenation of a c.sub.2+ paraffinic charge comprising a self-cooling system

A process for catalytic dehydrogenation of a C.sub.2+ paraffinic hydrocarbon charge comprising:

• a) dehydrogenating in a catalytic dehydrogenating zone under dehydrogenation conditions said charge in the gas phase in the presence of hydrogen to provide a dehydrogenation effluent comprising water, hydrogen, at least one olefinic hydrocarbon and at least one unconverted paraffinic hydrocarbon,
• b) one or more steps of cooling the dehydrogenation effluent in an indirect cooling zone with said charge before it is introduced into the dehydrogenation zone,
• c) compressing the thus-cooled effluent,
• d) eliminating water from the compressed effluent,
• e) cooling the compressed effluent in a dual-chamber heat exchanger,
• f) separating the thus-cooled effluent into a hydrogen-rich vapor phase and a hydrocarbon liquid phase comprising at least one olefinic hydrocarbon and unconverted hydrocarbons, and
• g) isentropically expanding the hydrogen-rich vapor phase to separate a hydrocarbon residual condensate, which is mixed with the cooled effluent from the dual-chamber heat exchanger, and hydrogen, at least a part of which is directly recycled to a first chamber of said dual-chamber heat exchanger and, therein, contacting said hydrogen with the charge in the liquid phase in said first chamber,
• wherein, for the cooling in the dual-chamber heat exchanger, the charge in the liquid phase, before being introduced to the dehydrogenation zone, is introduced into a first chamber of said dual-chamber heat exchanger, said first chamber being of sufficient volume to allow vaporization of the charge therein, and the compressed effluent is introduced into a second chamber of said dual-chamber heat exchanger such that the charge is evaporated and recovered from the first chamber and passed to the dehydrogenation zone, and the compressed effluent is cooled by indirect heat exchange.