Process and plant for separation of a hydrocarbon mixture

Process for separating a component mixture (K) comprising hydrogen, methane, hydrocarbons having two carbon atoms and hydrocarbons having three or more carbon atoms, comprising a deethanization and a demethanization subsequent to the deethanization, wherein

• in the deethanization at least a portion of the component mixture (K) is subjected to a first partial condensation by cooling from a first temperature level to a second temperature level at a first pressure level to obtain a first gas fraction (G1) and a first liquid fraction (C1),
• in the deethanization at least a portion of the first gas fraction (G1) is subjected to a second partial condensation by cooling from the second temperature level to a third temperature level at the first pressure level to obtain a second gas fraction (G4) and a second liquid fraction (C2),
• in the deethanization at least a portion of the first liquid fraction (C1) and at least a portion of the second liquid fraction (C1) is subjected to a rectification to obtain a third gas fraction (G3) and a third liquid fraction (C3+),
• the second partial condensation is performed such that the second gas fraction (G4) contains more than 95% hydrogen, methane and hydrocarbons having two carbon atoms,
• the first liquid fraction (C1) or its part subjected to the rectification and the second liquid fraction (C2) or its part subjected to the rectification are expanded from the first pressure level to a second pressure level before the rectification and the rectification is carried out at the second pressure level, the first pressure level being 25 to 35 bar and the second pressure level being 14 to 17 bar, and
• an overhead gas formed in the rectification is cooled to only−25 to −35° C. and thereby partially condensed, wherein a condensed portion of the overhead gas is used partially or completely as a reflux in the rectification and an uncondensed portion of the overhead gas is provided partially or completely as the third gas fraction (G3).

Plant (100, 200) for separation of a component mixture (K) comprising hydrogen, methane, hydrocarbons having two carbon atoms and hydrocarbons having three or more carbon atoms, wherein the plant (100, 200) comprises means for deethanization and means for demethanization, wherein the demethanization is subsequent to the deethanization, and wherein

• the means for deethanization comprise a first heat exchanger (E1) and a first vessel (D1) which are set up to subject at least a portion of the component mixture (K) to a first partial condensation by cooling from a first temperature level to a second temperature level at a first pressure level to obtain a first gas fraction (G1) and a first liquid fraction (C1),
• the means for deethanization comprise a second heat exchanger (E2) and a second vessel (D2) which are set up to subject at least a portion of the first gas fraction (G1) to a second partial condensation by cooling from the second temperature level to a third temperature level at the first pressure level to obtain a second gas fraction (G4) and a second liquid fraction (C2),
• the means for deethanization comprise a deethanization column (T2) which is set up to subject at least a portion of the first liquid fraction (C1) and at least a portion of the second liquid fraction (C2) to a rectification to obtain a third gas fraction (G3) and a third liquid fraction (C3+),
• the second heat exchanger (E2) and the second vessel (D2) which are provided as means for the second partial condensation are set up to perform the second partial condensation such that the second gas fraction (G4) comprises more than 95% hydrogen, methane and hydrocarbons having two carbon atoms, and
• means are provided in the form of expansion valves which are arranged to expand the first liquid fraction (C1) or its part subjected to the rectification and the second liquid fraction (C2) or its part subjected to the rectification from the first pressure level to a second pressure level before the rectification and to carry out the rectification at the second pressure level, the first pressure level being 25 to 35 bar and the second pressure level being 14 to 17 bar,
• characterized in that
• means are provided in the form of a head condenser (E7) mounted on top of the deethanization column (T2) which are adapted to cool an overhead gas formed during rectification to −25 to −35° C. and thereby partially condense it, and to use a condensed portion of the overhead gas partially or completely as a reflux in the rectification and to provide a non-condensed portion of the overhead gas partially or completely as the third gas fraction (G3).