초록 ▼

A closed-loop mixed refrigerant cycle provides efficient low-level refrigeration for recovering ethylene from a mixed gas feed. Compressed mixed refrigerant vapor is condensed at -20°F. to -50°F. and is subcooled to -175°F. to -225°F. by indirect heat exchange with cold H2, methane, and expander str

A closed-loop mixed refrigerant cycle provides efficient low-level refrigeration for recovering ethylene from a mixed gas feed. Compressed mixed refrigerant vapor is condensed at -20°F. to -50°F. and is subcooled to -175°F. to -225°F. by indirect heat exchange with cold H2, methane, and expander streams from elsewhere in the ethylene plant. A portion of the subcooled refrigerant may be flashed to provide additional subcooling of the main mixed refrigerant stream. Subcooled mixed refrigerant is subsequently flashed to provide very low temperature level refrigeration for feed condensation and demethanizer overhead condenser duties. The invention allows advantageous operation of the feed chilling train at pressures between 150 and 400 psia.

대표청구항 ▼

In the recovery of ethylene from a feed gas containing ethylene, hydrogen, and C1 to C3 hydrocarbons, wherein said recovery includes the steps of compressing and cooling said feed gas to condense a portion thereof, fractionating the condensed feed gas liquids in one or more demethanizer columns to r

In the recovery of ethylene from a feed gas containing ethylene, hydrogen, and C1 to C3 hydrocarbons, wherein said recovery includes the steps of compressing and cooling said feed gas to condense a portion thereof, fractionating the condensed feed gas liquids in one or more demethanizer columns to recover a light overhead product comprising chiefly hydrogen and methane, and fractionating the one or more demethanizer column bottoms streams to recover an ethylene product and streams containing C2 and heavier hydrocarbons, refrigeration for said recovery is provided in a cycle which comprises: (a) compressing a mixed refrigerant vapor comprising two or more components selected from the group consisting of methane, ethane, ethylene, propane, and propylene, and cooling the resulting compressed vapor to yield a condensed mixed refrigerant stream; (b) subcooling said condensed mixed refrigerant stream by indirect heat exchange with one or more cold process streams to yield a subcooled mixed refrigerant; (c) flashing a first portion of said subcooled mixed refrigerant and using the resulting refrigerant to provide overhead condenser refrigeration for at least one of said demethanizer columns by indirect heat exchange, which warms and at least partially vaporizes said first portion of subcooled mixed refrigerant; (d) flashing a second portion of said subcooled mixed refrigerant and using the resulting refrigerant to provide at least a portion of the refrigeration required to cool said feed gas by indirect heat exchange and condense a portion thereof, which warms and at least partially vaporizes said second portion of subcooled mixed refrigerant; and (e) combining the resulting warmed vapor streams from said first and second portions of the subcooled mixed refrigerants of steps (c) and (d) to provide at least a portion of said mixed refrigerant vapor, and repeating steps (a) through (e); whereby said feed gas is separated into a vapor stream containing lighter feed components and one or more liquid condensate streams enriched in heavier feed components, wherein the cooling, condensing, and separating of said feed gas is carried out in the pressure range of 150 to 400 psis.