Integrated process for NGL (natural gas liquids recovery) and LNG (liquefaction of natural gas)

An apparatus for integration of liquefaction of natural gas and recovery of natural gas liquids, said apparatus comprising:

• one or more heat exchangers for cooling and partially condensing by indirect heat exchange a feed stream containing light hydrocarbons;
• a gas/liquid cold separator and means for introducing a partially condensed feed stream from the one or more heat exchangers into the gas/liquid cold separator, the gas/liquid cold separator having upper outlet means for removing an overhead gaseous stream and lower outlet means for removing a bottoms liquid stream;
• means for introducing the overhead gaseous stream and the bottoms liquid stream from the gas/liquid cold separator into a fractionation system comprising a light ends fractionation column and a heavy ends fractionation column, the means comprising an expansion device for expanding at least a portion of overhead gaseous stream from the gas/liquid cold separator and means for introducing expanded overhead gaseous stream into a lower region of said light ends fractionation column, and means for introducing at least a portion of the bottoms liquid stream from the gas/liquid cold separator into said heavy ends fractionation column at an intermediate point thereof;
• means for removing a first liquid product stream from the bottom of the heavy ends fractionation column;
• means for removing an overhead gaseous stream from the top of the light ends fractionation column, and
• means for removing a bottoms liquid stream from a lower region of the light ends fractionation column, and introducing this bottoms liquid stream from the light ends fractionation column into an upper region of the heavy ends fractionation column;
• said apparatus further comprising:
• (i) a first heat exchanger for subjecting a first portion of the light ends fractionation column overhead gaseous stream to indirect heat exchange with an overhead gaseous stream removed from the top of the heavy ends fractionation column, whereby the overhead gaseous stream from the top of the heavy ends fractionation column is cooled and partially condensed, means for removing the cooled and partially condensed overhead gaseous stream from said first heat exchanger, and means for introducing this cooled and partially condensed overhead gaseous stream from the top of the heavy ends fractionation column into the light ends fractionation column;
• (ii) means for removing a second portion of the overhead gaseous stream from the light ends fractionation column as a side stream, and a further heat exchanger for subjecting the side stream to indirect heat exchange to further cool, and partially liquefy the side stream, wherein said side stream of the overhead gaseous stream from the light ends fractionation column is split off from the overhead gaseous stream from the light ends fractionation column prior to the indirect heat exchange between said first portion of the light ends fractionation column overhead gaseous stream and the overhead gaseous stream removed from the top of said heavy ends fractionation column in said first heat exchanger;
• (iii) means for introducing the partially liquefied side stream into a further separation means, means for recovering a liquid stream from the further separation means and means for introducing the recovered liquid stream into the light ends fractionation column as a liquid reflux stream and/or the heavy ends fractionation column as a liquid reflux stream,
• (iv) means for recovering an overhead vapor stream from the further separation means, a further heat exchanger for subjecting this overhead vapor stream to indirect heat exchange for additional cooling and partial condensation, means for feeding the resultant vapor and condensate to an LNG separator, and means for recovering LNG liquid product from the LNG separator, and
• (v) means for recovering an overhead vapor stream from the further separation means, a compressor for compressing this overhead vapor stream to form a residue gas.

A process for integrated liquefaction of natural gas and recovery of natural gas liquids, said process comprising:

• cooling a feed stream containing light hydrocarbons by indirect heat exchange in a feed heat exchanger;
• introducing the cooled feed stream into a gas/liquid cold separator, removing from said gas/liquid cold separator an overhead gaseous stream and bottoms liquid stream, and introducing said overhead gaseous stream and bottoms liquid stream into a fractionation system, said fractionation system comprising a light ends fractionation column and a heavy ends fractionation column;
• removing a liquid product stream from said fractionation system;
• removing an overhead gaseous stream from said fractionation system;
• generating a residue gas stream from said overhead gaseous stream from said fractionation system;
• introducing said residue gas stream into a further separation means, and recovering from said further separation means a liquid product stream and an overhead vapor stream;
• introducing either said liquid product stream or said overhead vapor stream to an LNG exchanger/separator;
• subjecting either said liquid product stream or said overhead vapor stream to liquefaction in said LNG exchanger/separator;
• and
• removing LNG liquid product from said LNG exchanger/separator,
• wherein an overhead gaseous stream is removed from the top of said light ends fractionation column as said overhead gaseous stream from said fractionation system;
• said overhead gaseous stream from said light ends fractionation column is split into a first portion and a second portion;
• after said overhead gaseous stream from said light ends fractionation column is split into a first portion and a second portion, said first portion is heated by indirect heat exchange with an overhead gaseous stream removed from the top of said heavy ends fractionation column, whereby said overhead gaseous stream from the top of said heavy ends fractionation column is cooled by said indirect heat exchange;
• said second portion of overhead gaseous stream is cooled by indirect heat exchange;
• and
• the cooled second portion of overhead gaseous stream is introduced into said further separation means as said residue gas.