Method for producing a flow which is rich in methane and a cut which is rich in C2+ hydrocarbons from a flow of feed natural gas and an associated installation
First Claim
1. A method for producing a flow which is rich in methane and a cut which is rich in C2+ hydrocarbons from a flow of dehydrated feed natural gas, which is composed of hydrocarbons, nitrogen and CO2 and which advantageously has a molar content of C2+ hydrocarbons greater than 10%, the method comprising the following steps of:
- cooling the feed natural gas flow advantageously at a pressure greater than 40 bar in a first heat exchanger and introducing the cooled, feed natural gas flow into a first separation flask;
separating the cooled natural gas flow in the first separation flask and recovering a light fraction which is substantially gaseous and a heavy fraction which is substantially liquid;
dividing the light fraction into a flow for supplying to a turbine and a secondary flow;
dynamic expansion of the turbine supply flow in a first expansion turbine and introducing the expanded flow into an intermediate portion of a separation column;
cooling the secondary flow in a second heat exchanger and introducing the cooled secondary flow into an upper portion of the separation column;
expanding the heavy fraction, vaporization in the first heat exchanger and introduction into a second separation flask in order to form a head fraction and a bottom fraction;
introducing the head fraction, after cooling in the second heat exchanger, in the upper portion of the separation column;
introducing the bottom fraction into an intermediate portion of the separation column;
recovering, at the bottom of the separation column, a bottom flow which is rich in C2+ hydrocarbons and which is intended to form the cut rich in C2+ hydrocarbons;
removing, at the head of the separation column, a head flow rich in methane;
reheating the head flow rich in methane in the second heat exchanger and in the first heat exchanger and compressing the head flow rich in methane in at least a first compressor and in a second compressor in order to form a flow rich in methane from the compressed head flow rich in methane;
removing a first recirculation flow from the head flow rich in methane;
passing the first recirculation flow into the first heat exchanger and into the second heat exchanger in order to cool the first recirculation flow, then introducing at least a first portion of the first cooled recirculation flow into the upper portion of the separation column;
wherein the method comprises the following steps of;
forming a dynamic expansion flow from a second recirculation flow from the head flow rich in methane and introducing the dynamic expansion flow into the first expansion turbine in order to produce a cooling thermal power, said cooling thermal power being introduced into the separation column, the method comprising;
removing a removal flow from the head flow rich in methane, before the head flow rich in methane is introduced into the first compressor and the second compressor;
compressing the removal flow in a third compressor;
forming the second recirculation flow from the compressed removal flow from the third compressor, after cooling.
1 Assignment
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Accused Products
Abstract
This method comprises cooling the feed natural gas in a first heat exchanger and introducing the cooled, feed natural gas into a first separation flask.
It comprises the dynamic expansion of a turbine supply flow in a first expansion turbine and introducing the expanded flow into a separation column. This method comprises removing, at the head of the separation column, a head flow rich in methane and removing a first recirculation flow from the compressed head flow rich in methane.
The method comprises forming at least a second recirculation flow obtained from the head flow rich in methane downstream of the separation column and forming a dynamic expansion flow from the second recirculation flow.
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Citations
8 Claims
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1. A method for producing a flow which is rich in methane and a cut which is rich in C2+ hydrocarbons from a flow of dehydrated feed natural gas, which is composed of hydrocarbons, nitrogen and CO2 and which advantageously has a molar content of C2+ hydrocarbons greater than 10%, the method comprising the following steps of:
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cooling the feed natural gas flow advantageously at a pressure greater than 40 bar in a first heat exchanger and introducing the cooled, feed natural gas flow into a first separation flask; separating the cooled natural gas flow in the first separation flask and recovering a light fraction which is substantially gaseous and a heavy fraction which is substantially liquid; dividing the light fraction into a flow for supplying to a turbine and a secondary flow; dynamic expansion of the turbine supply flow in a first expansion turbine and introducing the expanded flow into an intermediate portion of a separation column; cooling the secondary flow in a second heat exchanger and introducing the cooled secondary flow into an upper portion of the separation column; expanding the heavy fraction, vaporization in the first heat exchanger and introduction into a second separation flask in order to form a head fraction and a bottom fraction; introducing the head fraction, after cooling in the second heat exchanger, in the upper portion of the separation column; introducing the bottom fraction into an intermediate portion of the separation column; recovering, at the bottom of the separation column, a bottom flow which is rich in C2+ hydrocarbons and which is intended to form the cut rich in C2+ hydrocarbons; removing, at the head of the separation column, a head flow rich in methane; reheating the head flow rich in methane in the second heat exchanger and in the first heat exchanger and compressing the head flow rich in methane in at least a first compressor and in a second compressor in order to form a flow rich in methane from the compressed head flow rich in methane; removing a first recirculation flow from the head flow rich in methane; passing the first recirculation flow into the first heat exchanger and into the second heat exchanger in order to cool the first recirculation flow, then introducing at least a first portion of the first cooled recirculation flow into the upper portion of the separation column;
wherein the method comprises the following steps of;forming a dynamic expansion flow from a second recirculation flow from the head flow rich in methane and introducing the dynamic expansion flow into the first expansion turbine in order to produce a cooling thermal power, said cooling thermal power being introduced into the separation column, the method comprising; removing a removal flow from the head flow rich in methane, before the head flow rich in methane is introduced into the first compressor and the second compressor; compressing the removal flow in a third compressor; forming the second recirculation flow from the compressed removal flow from the third compressor, after cooling. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An installation for producing a flow rich in methane and a cut rich in C2+ hydrocarbons from a dehydrated feed natural gas flow which is composed of hydrocarbons, nitrogen and CO2 and which advantageously has a molar content of C2+ hydrocarbons greater than 10%, the installation comprising:
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a first heat exchanger for cooling the feed natural gas flow which advantageously flows at a pressure greater than 40 bar; a first separation flask; an apparatus for introducing the cooled feed natural gas flow into the first separation flask, the flow of cooled natural gas being separated in the first separation flask in order to recover a light, substantially gaseous fraction and a heavy, substantially liquid fraction; an apparatus for dividing the light fraction into a flow for supplying a turbine and a secondary flow; a first dynamic expansion turbine for the turbine supply flow; a separation column; an apparatus for introducing the expanded flow into the first dynamic expansion turbine in an intermediate portion of the separation column; a second heat exchanger for cooling the secondary flow and an apparatus for introducing the cooled secondary flow in an upper portion of the separation column; an apparatus for expanding the heavy fraction and an apparatus for passing the heavy fraction through the first heat exchanger; a second separation flask; an apparatus for introducing the heavy fraction from the first heat exchanger into the second separation flask in order to form a head fraction and a bottom fraction; an apparatus for introducing the head fraction, after it has been introduced into the second exchanger to cool the head fraction, into the upper portion of the separation column; an apparatus for introducing the bottom fraction into an intermediate portion of the separation column; an apparatus for recovering, at the bottom of the separation column, a bottom flow which is rich in C2+ hydrocarbons and which is intended to form the cut rich in C2+ hydrocarbons; an apparatus for removing, at the head of the separation column, a head flow rich in methane; an apparatus for introducing the head flow rich in methane into the second heat exchanger and into the first heat exchanger in order to reheat the head flow rich in methane; an apparatus for compressing the head flow rich in methane comprising at least a first compressor and a second compressor in order to form the flow rich in methane from the compressed head flow rich in methane; an apparatus for removing a first recirculation flow from the head flow rich in methane; an apparatus for introducing the first recirculation flow into the first heat exchanger then into the second heat exchanger in order to cool the first recirculation flow; an apparatus for introducing at least a portion of the first cooled recirculation flow into the upper portion of the separation column; wherein the installation comprises; an apparatus for forming a dynamic expansion flow from a second recirculation flow from the head flow rich in methane; an apparatus for passing the dynamic expansion flow through the first dynamic expansion turbine in order to produce a cooling thermal power, said cooling thermal power being introduced into the separation column; a third compressor that receives a removal flow from the head flow rich in methane before the head flow rich in methane is introduced into the first compressor and the second compressor, and forms the second recirculation flow by compressing the removal flow after cooling. - View Dependent Claims (8)
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Specification