Method and apparatus for cooling and liquefying at least one gas with a low boiling point, such as for example natural gas
AssigneeCompagnie Francaise d'Etudes et de Construction "Technip"
InventorsHenri Paradowski, Didier Leroux
Life of this patent
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Abstract
The present invention relates to a method and an apparatus for liquefying a gas with a low boiling point, such as natural gas, by heat exchange with a main refrigerant fluid having several components. The whole of the vapor phase of this main refrigerant fluid, after being condensed and subcooled, is expanded at once to at least one first pressure, and the whole of the liquid phase of the subcooled main refrigerant fluid is expanded at once to at least one second pressure, different from the said first pressure.
Claims21
A method of cooling and liquefying at least one gas having a low boiling point through heat exchange with at least one part of a main refrigerating fluid precooled until its at least partial liquefaction through heat exchange with an auxiliary refrigerating fluid, said refrigerating fluids being part of an incorporated cold-generating cascade of at least these two refrigerating fluids, each refrigerating fluid consisting of a mixture of several component substances, and said main refrigerating fluid evolving according to a closed-loop cooling cycle while successively undergoing therein:
- at least one compression in the gaseous state, at least one preliminary cooling with at least partial condensation, through heat exchange with said auxiliary refrigerating fluid, at least one separation of the liquid and vapor phases thus obtained, at least one refrigeration with total liquefaction and then sub-cooling and thereafter expansion through subsequent heat exchange and resulting attendant vaporization, in countercurrent relationship with itself and with the said gas for liquefying the latter at least partially, its vapor thus reheated being finally recycled and recompressed, wherein the improvement consists in the steps of once expanding said condensed and sub-cooled vapor phase of the main refrigerating liquid down to at least one first pressure, and of once expanding the said sub-cooled liquid phase of the main refrigerating fluid down to at least one second pressure, different from the said first pressure.
An apparatus for cooling and liquefying at least one gas having a low boiling point, including at least the following circuits:
- an open circuit of gas to be liquefied (1);
- a closed circuit of main refrigerating fluid (2) in heat exchanging relationship with said gas circuit (1) by means of at least one cryogenic heat-exchanger (4), and being part of one cold-generating incorporated cascade of at least two refrigerating main and auxiliary fluids, respectively;
- a closed circuit of auxiliary refrigerating fluid (3) in heat exchanging relationship with said circuit of main refrigerating fluid (2) and said circuit of gas to be liquefied (1), by means of at least one cryogenic heat-exchanger (6) for pre-cooling and at least partially liquefying said main refrigerating fluid, the said closed circuit of main refrigerating fluid (2) successively comprising at least the following elements:
- at least one gaseous fluid compressor (18, 19, 22, 23);
- at least one heat exchanger or cooler (20, 24, 26);
- a flow passage-way (27) for the main refrigerating fluid extending through the said cryogenic exchanger (6) of the auxiliary refrigerating fluid circuit (3);
- a separator (29) for separating the vapor and liquid phase of said main refrigerating fluid;
- said cryogenic heat-exchanger (4);
- and expansion means (34, 35, 42, 43, 83, 84) including an expansion member provided on the flow passage-way of each fraction of the main refrigerating fluid and connected to said compressor, the improvement consisting in that the said cryogenic heat-exchanger (4) or the main refrigerating fluid circuit (2) is a plate exchanger provided with multiple passage-ways (15, 31, 36, 37, 39, 44, 45) for each of the fluids present during the heat exchange, namely, the gas to be liquefied, the liquid and vapor phases or fractions of the partially condensed main refrigerating fluid, as well as the fractions derived therefrom, expanded to different pressure levels.
Dependencies are inferred from the claim text.