Patent ID: 7707852

Claim:
A process for recovering lower carbon olefins from a product gas, wherein said product gas is a mixed gas obtainable from the methanol and/or dimethyl ether to olefin conversion, said process comprising deethanizing said product gas to obtain C2 and light components at the top of the column and C3 and heavy components at the bottom of the column, and demethanizing C2 and light components to obtain a tail gas and liquid phase C2 component, condensing said tail gas and recovering the condensed liquid phase back to said demethanizing step, wherein said process further comprises one or more steps of (1) a material stream extracted from the top of a deethanizing column or a mixed C2 component stream extracted from a reflux tank of a demethanizing column is used as a coolant for condensing the tail gas; (2) an ethylene product and ethane obtained by ethylene rectifying the liquid phase C2 component is used as a coolant for condensing the tail gas; and (3) rectifying the tail gas before condensation to recover ethylene in said tail gas.