LIQUEFACTOR AND METHOD FOR LIQUEFYING A GAS

Abstract

A liquefactor for a gas includes a framework (O) containing at one end at least one plate-and-fin heat exchanger (E), each plate having a length and a width, and the plates being arranged with their length parallel to the length of the framework and at the other end a turbine (M) to provide cold to the at least one heat exchanger, the framework being orientated such that the turbine is positioned beneath the at least one exchanger.

Claims

1. A liquefactor for a gas that is liquefied at a cryogenic temperature, comprising an assembly comprising a framework, the framework having a substantially elongate parallelepiped shape and having a main axis corresponding to its length and two ends, the framework not containing a distillation column, and inside the framework: i) at one end of the framework at least one plate-and-fin heat exchanger, each plate having a length and a width, and the plates being arranged with their length parallel to the axis of the framework, ii) a line for sending a gas to be liquefied to the at least one heat exchanger, iii) a line for removing a cooled or liquefied gas from the at least one heat exchanger, iv) a support mounted inside the framework, v) at least one turbine, the turbine being fastened to the support and being arranged to drive a compressor arranged outside the framework, the turbine being connected to the at least one exchanger to send a gas cooled or heated in the at least one heat exchanger to be expanded in the turbine and/or to send a gas expanded in the turbine from the turbine to the at least one heat exchanger, vi) at least one cooler connected to cool gas compressed in the compressor, vii) a means for conveying a refrigerant to the cooler, and viii) wherein the turbine is positioned at another end of the framework and the cooler is positioned between the turbine and the at least one heat exchanger, or b) the cooler is positioned at another end of the framework and the turbine is positioned between the cooler and at least one heat exchanger, wherein the framework is positioned with the main axis vertical, the at least one heat exchanger being positioned above the at least one turbine and the at least one cooler, the line for sending a gas to be liquefied to the heat exchanger in the framework and a means connected to the heat exchanger to remove a liquefied gas from the framework.

2. The liquefactor according to claim 1, comprising at least one partition dividing the framework into at least two portions, the partition having the shape of a rectangular plate arranged perpendicular to the axis of the framework, the partition acting as support for the turbine if the cooler is at the other end of the framework or for the cooler if the turbine is at the other end of the framework, the turbine and the cooler being separated from one another by the partition.

3. The liquefactor according to claim 1, further comprising fastening feet connected to the other end of the framework to place the framework on a foundation.

4. The liquefactor according to claim 1, further comprising a means for fluidically connecting the exchanger to the compressor to convey a gas cooled in the exchanger to the compressor.

5. The liquefactor according to claim 1, further comprising a means for fluidically connecting the exchanger to the turbine to convey a gas expanded in the turbine to the exchanger.

6. The liquefactor according to claim 1, wherein the framework is divided into at least three compartments, each compartment having a dimension that is a portion of the length of the framework, the at least one heat exchanger being in one of the at least three compartments, the turbine in another of the at least three compartments and the at least one cooler in another of the at least three compartments, the compartments containing the turbine, and the at least one cooler forming a parallelepiped wider than the parallelepiped formed by the compartment containing the heat exchanger.

7. The liquefactor according to claim 6, further comprising a fourth compartment containing neither a heat exchanger nor a turbine, but containing connection lines between the at least one heat exchanger and another element, which may be the at least one turbine.

8. The liquefactor according to claim 7, wherein the turbine is positioned at another end of the framework and is connected to the fourth compartment via a compartment arranged side by side with the compartment containing the cooler.

9. The liquefactor according to claim 1, wherein the framework is at least 10 m long, the cooler and the turbine occupying a portion of the length of the framework equal to at least 4 m.

10. The liquefactor according to claim 1, wherein the at least one heat exchanger is thermally insulated.

11. A method for liquefying a gas at a cryogenic temperature, using an assembly comprising a framework, the framework having a substantially elongate parallelepiped shape and having a main axis corresponding to its length and two ends, the framework not containing a distillation column, and inside the framework: i) at one end of the framework at least one plate-and-fin heat exchanger, each plate having a length and a width, and the plates being arranged with their length parallel to the axis of the framework, ii) a line for sending a gas to be liquefied to the at least one heat exchanger, a line for removing a cooled or liquefied gas from the at least one heat exchanger, iv) a support mounted inside the framework, v) at least one turbine, the turbine being fastened to the support and being arranged to drive a compressor arranged outside the framework, the turbine being connected to the at least one exchanger to send a gas cooled or heated in the at least one heat exchanger to be expanded in the turbine and/or to send a gas expanded in the turbine from the turbine to the at least one heat exchanger, vi) at least one cooler connected to cool gas compressed in the compressor, vii) a) the turbine is positioned at another end of the framework and the cooler is positioned between the turbine and the at least one heat exchanger, or b) the cooler is positioned at another end of the framework and the turbine is positioned between the cooler and at least one heat exchanger, viii) the framework being positioned with its main axis vertical, the at least one heat exchanger being positioned above the at least one turbine and the at least one cooler, wherein a gas to be liquefied is sent to the heat exchanger in the framework and a liquefied gas is removed from the heat exchanger, a refrigerant is conveyed to the cooler and cold is provided for the liquefaction by expanding a gas in the at least one turbine, the gas having been cooled or heated in the at least one heat exchanger and/or a gas expanded in the turbine being sent to the at least one heat exchanger.

12. An apparatus for separating air by cryogenic distillation comprising a system of columns, a liquefactor according to claim 1, and a means for sending a nitrogen-rich gas to the liquefactor from the column system as gas to be liquefied.

13. The apparatus according to claim 12, further comprising a means for sending a gas liquefied in the liquefactor to the system of columns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0056] FIG. 1 is a longitudinal cross section of a framework according to the invention in the vertical position.

[0057] FIG. 2 is a longitudinal cross section of a variant framework according to the invention during manufacture and transport in the horizontal position.

[0058] FIG. 3 is a longitudinal cross section of the variant framework according to FIG. 2 showing installation on site.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0059] FIG. 1 shows an assembly comprising a nitrogen liquefactor framework 1 installed with its main axis, which is its length, vertical and the equipment contained in the framework. One end of the framework is positioned a few metres from the ground or from a flat surface, while the opposite end is anchored to the ground or the flat surface.

[0060] The framework O has a substantially parallelepipedic shape with a length, a width and a height. The cross section of the framework is rectangular or square.

[0061] As shown here, the substantially parallelepipedic framework in fact comprises two parallelepipeds that may be of different widths and that are joined to one another preferably by welding or bolting, the compartments 1 and 4 forming one parallelepiped and the compartments 2 and 3 forming the other. It is preferable for the wider parallelepiped (in this case the parallelepiped containing the compartments 2 and 3) to be arranged beneath the other for reasons of stability.

[0062] At the top of the framework in a first compartment 1 there is at least one heat exchanger E that is used to cool the gas to be liquefied to a temperature close to the liquefaction temperature or to the liquefaction temperature. The exchangers are oriented with their hot end up and the bottom end down, when the framework is installed vertically. A line C conveys the gas to be liquefied to the hot end of the heat exchanger, this line C potentially being connected to an air separation apparatus producing nitrogen gas.

[0063] The first compartment 1 is thermally insulated using a pulverulent insulator such as perlite.

[0064] Beneath the first compartment 1 there may be an auxiliary compartment 4, also referred to as a connection box, separated from the first compartment by a wall and containing an essentially pulverulent insulator or rock wool. The auxiliary compartment 4 contains neither heat exchangers nor turbines. It contains primarily connection lines that pass through the partition via openings therein. These lines connect the heat exchanger E to a turbine M, which is positioned in a third compartment 3 positioned at the end of the framework O. The turbine M is connected to the at least one exchanger to send a gas cooled or heated in the at least one heat exchanger to be expanded in the turbine M and/or to send a gas expanded in the turbine M from the turbine M to the at least one heat exchanger.

[0065] The heat exchanger E is a plate-and-fin exchanger comprising a stack of plates, each plate being separated from at least one adjacent plate by fins, each plate having a length and a width, and the plates being arranged with their length parallel to the axis of the framework.

[0066] The figure shows that the heat exchanger comprises two bodies, each of which can be considered to be a heat exchanger and each comprising a stack of plates, each plate having a length and a width, and the plates being arranged with their length parallel to the axis of the framework.

[0067] The turbine M drives a compressor of the liquefactor via a shaft, the compressor being positioned outside the framework O. The compressor is used to compress a gas cooled or heated in the at least one heat exchanger.

[0068] At least a portion of the gas compressed in the compressor can be expanded in the turbine M, depending on the methods.

[0069] In a second compartment 2, positioned between the third compartment 3 and the auxiliary compartment 4, there is a cooler R supplied with a refrigerant such as water to cool the gas compressed in the compressor driven by the turbine M of the third compartment 3. There are therefore lines passing through the partition between the second and third compartments 2, 3. This partition may need to be reinforced to withstand the weight of the cooler R. Since the cooler R operates at ambient temperature or temperatures above 20? C., it does not need to be thermally insulated, or it may have a protective element to prevent staff from touching the hot parts. The framework is preferably not clad with metal sheeting about the cooler, which is therefore in the open air.

[0070] To enable direct access for the fluids coming from at least one exchanger E to the turbine M and going from the turbine M towards the at least one exchanger, a compartment 5 extends on one side of the framework between the second and fourth compartments, alongside the second compartment 2. The fluids thus do not have to pass through the second compartment 2, the lines only passing through the compartment 5. Since the lines of the compartment are L-shaped, this provides greater flexibility when the exchangers are heated and cooled, causing expansion and shrinkage.

[0071] This compartment 5 is thermally insulated using particulate insulators or rock wool, and must therefore be closed hermetically, as must compartments 1 and 4 (where present).

[0072] The framework does not contain a scrubbing or distillation column, as the liquefactor itself does not contain these elements.

[0073] A feed gas is sent into the framework O, is cooled in the at least one exchanger E, in one variant at least a portion of the feed gas is compressed in the compressor driven by the turbine M and then cooled in the cooler R, at least a portion of the feed gas is expanded in the turbine M. The gas sent to the turbine M preferably comes from the cooler R.

[0074] A portion of the feed gas is liquefied either in the exchanger or downstream of the exchanger and forms the product of the method.

[0075] The feed gas may be nitrogen, hydrogen, natural gas.

[0076] In this case, this type of liquefactor is commonly associated with an apparatus for separating air by cryogenic distillation comprising a system of columns S, nitrogen gas from the apparatus for separating air comprising the feed gas of the liquefactor and at least a portion of the liquid nitrogen formed possibly being returned to the apparatus for separating air.

[0077] It is noted that the exchangers are arranged at height, with their length extending in the direction of the main axis of the framework, thereby making shrewd use of the space beneath the exchangers. Furthermore, given that the framework is at least 10 m long, the cooler and the turbine occupying a portion of the length of the framework equal to at least 4 m, when the framework is arranged vertically, the cold end of at least one exchanger is at least 6 m from the ground. A liquefied gas coming out of the cold end thus has a non-negligible hydrostatic pressure, making it easier to send elsewhere and enabling the size of a pump to be reduced, if present.

[0078] Since the compartments 1 and 4 (if present) are thermally insulated using perlite, the framework is clad with metal sheeting. For the compartments 2 and 3 where the thermal insulation, if present, is usually rock wool, it is possible for the framework to not be clad with metal sheeting.

[0079] It is advisable to leave an opening in the framework that is large enough to enable the turbine to be inserted, if the turbine arrives late on site. Since the compartment 5 of the turbine M is on ground level, this insertion is particularly easy and does not require the use of a crane.

[0080] The turbine M is connected to provide cold to the at least one heat exchanger E.

[0081] The assembly comprising the framework O in FIG. 2 differs from the assembly in FIG. 1 in that the compartments 2 and 3 are inverted, the cooler R being positioned at the end of the framework in the compartment 2 and the turbine M between the compartment 4 and the compartment 2 of the cooler R. Since the compartment 3 of the turbine M is at a height greater than 2 m, this insertion does not require the use of a crane.

[0082] During manufacture and transport (FIG. 2), the framework is arranged with its main axis horizontal. The lifting lugs L can be seen at the end of the framework where the exchangers E are positioned. Such lugs L can be positioned at both ends of the framework O.

[0083] During on-site installation (FIG. 3), these lugs or attachments L enable a crane G to lift the framework and to install it with its main axis vertical. Feet P enable the framework to be fastened to the ground or to a foundation.

[0084] The framework O can take the form of a standardized container to facilitate transport.

[0085] The framework O comprises means for sending a flushing gas to the compartments 1, 4 and 5 (if present for the latter two compartments).

[0086] The turbine may be transported in the framework or incorporated into the framework on site. In the second case, the dimensions and rigidity values of the framework must be calculated in both cases: where the turbine is present and where the turbine is absent.

[0087] The framework may be lifted in a single operation, being preferably formed as a single piece.

[0088] The at least one turbine and the at least one cooler are supported in the framework, to enable operation if the framework is positioned with its main axis, which is its length, vertical. The at least one heat exchanger is supported in the framework to operate when positioned above at least one turbine and the at least one cooler.

[0089] It is understood that if the framework has to be transported, the equipment contained therein has to be secured horizontally for transportation, even if said equipment must ultimately operate vertically with the framework.

[0090] The gas to be expanded in the at least one turbine may be the gas to be liquefied or another gas, for example a mixed refrigerant.

[0091] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.