Process and installation for the production of a liquefied cryogenic fluid

Abstract

A process for producing a liquefied cryogenic fluid (7), such as liquefied natural gas, from a gas stream of gas to be cooled (6) containing at least methane and heavy hydrocarbons with 6 or more carbon atoms, comprising the steps: mixing the gas stream of gas to be cooled (6) with a portion (11) of the liquefied cryogenic fluid taken downstream of a liquefier (2), to form a two-phase stream (8); separating the two-phase stream (8) in a vessel (3), such as a phase separator, into a first gaseous fraction (9) and a second liquid fraction (10) comprising the majority of the heavy hydrocarbons with 6 or more carbon atoms from the gas stream of gas to be cooled; introducing the first gaseous fraction (9) into the liquefier (2) to produce the liquefied cryogenic fluid (7). (Shorthand figure: Fig. 2)

Claims

Demands

1. A process for producing a liquefied cryogenic fluid (7) such as liquefied natural gas from a gaseous stream of gas to be cooled (6) containing at least methane and heavy hydrocarbons with 6 or more carbon atoms, in a liquefied cryogenic fluid production plant, the process comprising the steps: - mixing the gaseous stream of gas to be cooled (6) with a portion (11) of the liquefied cryogenic fluid (7) taken downstream of a liquefier (2), to form a two-phase stream (8); - separating, in a vessel (3) such as a phase separator, the two-phase stream (8) into a first gaseous fraction (9) and a second liquid fraction (10), the second liquid fraction (10) comprising the majority of the heavy hydrocarbons with 6 or more carbon atoms, of the gaseous stream of gas to be cooled; - introduce the first gaseous fraction (9) into the liquefier (2) to produce the liquefied cryogenic fluid (7).

2. Method according to claim 1, the step of mixing the gas stream of gas to be cooled (6) with the liquefied part of the cryogenic fluid, being carried out upstream of the balloon (3), before introducing the two-phase flow (8) into the balloon (3), in particular via a fitting in a pipe to fluidly connect the gas stream of gas to be cooled with the downstream of the liquefier (2).

3. Method according to claim 1, the step of mixing the gas stream of gas to be cooled (6) with the liquefied cryogenic fluid portion being carried out by an injection, in particular by spraying, of the portion (11) of the liquefied cryogenic fluid (7) into the balloon (3), for example in its upper part, in particular in combination with an injection of the gas stream of gas to be cooled (6) into the balloon (3), for example in its lower part.

4. A method according to any one of claims 1 to 3, comprising a pre-cooling step of the gas stream to be cooled (6) before it is mixed with the portion (11) of the liquefied cryogenic fluid (7), in particular to ensure that its temperature is between 0 °C and -50 °C.

5. A method according to any one of claims 1 to 4, comprising a step of increasing the pressure of the portion (11) of the liquefied cryogenic fluid (7) before it is mixed with the gaseous stream of gas to be cooled (6), in particular via a hydrostatic head and / or a compression element (4), such as a pump (4).

6. A method according to any one of claims 1 to 5, comprising a step of expanding the gaseous flow of gas to be cooled (6), in particular via an expansion member (5) comprising, for example, at least one valve and / or an ejector, the expansion member (5) being in particular disposed upstream of the balloon (3).

7. Installation (1) for the production of a liquefied cryogenic fluid (7) such as liquefied natural gas from a gaseous stream of gas to be cooled (6) containing at least methane and heavy hydrocarbons with 6 or more carbon atoms, comprising: - a circuit of gas to be cooled having an upstream end intended to be connected to the gaseous stream of gas to be cooled (6) and a downstream end for delivering the liquefied cryogenic fluid (7);- a tank (3), in the circuit of gas to be cooled, the installation (1) being configured so that the tank (3) receives the gaseous stream of gas to be cooled (6) and a part (11) of the liquefied cryogenic fluid (7), to form a two-phase stream (8) and / or the installation being configured so that the tank (3) receives a two-phase stream (8) resulting from the mixture between the gaseous stream of gas to be cooled (6) and the part (11) of the liquefied cryogenic fluid (7), the tank (3) being configured to allow separation of the two-phase stream (8) into a first gaseous fraction (9) and a second liquid fraction (10) comprising the majority of the heavy hydrocarbons with 6 or more carbon atoms, of the gaseous stream of gas to be cooled (6); - a liquefier (2) configured to cool the first gaseous fraction (9) and produce the liquefied cryogenic fluid (7).

8. Installation (1) according to the preceding claim, comprising a compression element (4) such as a pump, the compression element being in particular disposed in a loop of the circuit of gas to be cooled, being configured to allow an increase in the pressure of the portion (11) of the liquefied cryogenic fluid (7) before being mixed with the gas stream of gas to be cooled (6).

9. Installation (1) according to any one of claims 7 to 8, being configured to create a hydrostatic head between a point of withdrawal of the portion (11) of the liquefied cryogenic fluid (7) and a point of mixing of the portion (11) of the liquefied cryogenic fluid (7) withdrawn with the gaseous stream of gas to be cooled (6).

10. Installation (1) according to any one of claims 7 to 9, comprising a pressure-reducing device (5) including, for example, at least one valve and / or ejector, the pressure-reducing device (5) being configured to allow expansion of the gas flow of gas to be cooled (6), in particular by being positioned upstream of the tank (3).

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