| 主权项 |
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 being of the type 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 that flow 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. |
