ES8500202A1 - Selective recovery of hydrocarbon(s) from oxygen-contg. gas streams - Google Patents

Abstract

Process for recovering a hydrocarbon (I) from a gas stream which besides various hydrocarbons also contains small amounts of oxygen, using a pressure change adsorption process in a number of adsorbers operating cyclically. During an adsorption phase at elevated press., selective adsorption of the hydrocarbon to be recovered occurs; during the adsorption phase and during at least one equilibrating phase subsequent to the adsorption phase, a gas stream is drawn off the outlet end of an adsorber, which is depleted in the hydrocarbon to be recovered; during at least one subsequent counter flow depressurisation from the inlet end of the adsorber, a desorbate stream enriched in the hydrocarbon to be recovered is drawn off; and after the desorption, the adsorber undergoes a pressure building phase during which it is returned to adsorption press. with a gas low in oxygen. - Process allows selective recovery of a hydrocarbon from an O2-contg. gas stream without exceeding the explosive limits of oxygen/hydrocarbon in the system, and is esp. useful for recovering ethylene from a gas stream consisting mainly of methane and ethylene. EPAB- EP--83433 B A process for recovering a hydrocarbon from a gas stream containing oxygen, by pressure-alternating adsorption process carried out in a plurality of cyclically alternating adsorbers, in which process, during an adsorption phase at an increased pressure, a selective adsorption of the hydrocarbon to be recovered is effected, in which during a counter-flow expansion, a desorbate stream enriched inthe hydrocarbon to be recovered, is withdrawn from the inlet end of the adsorber, and in which the adsorber passes through a pressure build-up phase after the desorption, characterised in that, in order to recover a hydrocarbon from a hydrocarbon mixture which contains small amounts of oxygen, during the adsorption phase and during at least one direct-flow expansion phase which follows the adsorption phase, a hydrocarbon-containing gas stream which is impoverished in respect of the hydrocarbon to be recovered, is removed at the outler end of an adsorber, and that, in order to build up the pressure of an adsorber after the desorption, a gas is used the oxygen content of which is smaller than the oxygen content of the gases which escape from an absorber during an adsorption phase or a direct-flow expansion phase. (7pp) USAB- US4498910 A Pressure swing adsorption process conducted in a plurality of cyclically interchangeable adsorbers, for recovering a hydrocarbon (I) from a gaseous feed stream contg. hydrocarbons and a minor amt. of H2, comprises the steps in a cycle of: (a) selectively adsorbing (I) to be recovered during an adsorption phase conducted under elevated press.; (b) during the adsorption phase and during at least one cocurrent expansion phase following the adsorption phase, withdrawing a residual gaseous stream at the outlet end of an adsorber, which stream is depleted in (I) and enriched in O2; (c) during a subsequent countercurrent expansion phase of desorption, withdrawing a stream enriched in desorbed (I) from the inlet end of the adsorber; and (d) after the desorption in step (c), conducting a pressure build-up phase by re-pressurising the adsorber to the adsorption pressure with the gaseous feedstream or a gas free of O2, so as to prevent the occurrence of localised concns. of O2 within the adsorber of above 90% of its explosive limits, and then repeating the cycle.