Patent Application
20240310114
This application claims the benefit of priority under 35 U.S.C. § 119 (a) and (b) to French Patent Application No. 2302424, filed Mar. 16, 2023, the entire contents of which are incorporated herein by reference.
The present invention relates to a liquefactor and method for liquefying a gas that is liquefied at a cryogenic temperature, for example nitrogen, hydrogen, and natural gas.
FR2706025 describes an apparatus for separating air by cryogenic distillation comprising a framework containing the heat exchangers, the subcoolers, the valves, the cryogenic pumps, the turbines and the pipes to connect them together. A distillation column is placed outside this framework.
Nitrogen liquefactors are known from U.S. Pat. No. 2022/0404094.
“Marinized Liquefaction and Gas Conditioning for Floating LNG” by Bryan Trocquet, GasTech 2009 discloses a framework having a heat exchanger at one end. One objective of the present invention is to reduce the footprint of a liquefactor and to facilitate the late installation of any equipment, for example a turbine in the framework, even if the latter is delivered late.
Indeed, the turbine is often delivered after arrival of other elements, and it is desirable to find means for installing it with a reduced number of necessary operations, and in particular without having to use a crane, in the workshop, an overhead crane or a simple material lift can be used for on-site installation of equipment.
It is beneficial to use a support means for the heat exchanger of the liquefactor that also acts as framework for the module assembly. As a result, this framework contains other elements of the liquefactor enabling the assembly to be mounted in the workshop by qualified staff, the connections between the exchanger and the other elements of the framework, for example a connection box, pipes, instrumentation and electricity, are also made in the manufacturing workshop.
In addition to reducing the footprint, positioning the exchangers at a height of at least 4 m from the ground makes it possible to produce liquid, thereby creating hydrostatic pressure, which can be used to transport the gas or to reduce the size of a pump used to pressurize the liquid.
According to one aspect of the invention, a liquefactor is provided 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:
According to other optional aspects which can be combined together in any way compatible with science and logic:
According to another aspect of the invention, a method is provided 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:
According to another aspect of the invention, an assembly comprising a framework is provided, 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:
The support may in particular be a flat surface positioned between the two ends of the framework, perpendicular to the length of the framework.
The support may be a partition of the framework.
According to another aspect of the invention, an apparatus is provided for separating air by cryogenic distillation comprising a system of columns, a liquefactor as described above, and means for sending a nitrogen-rich gas to the liquefactor from the column system as gas to be liquefied, and possibly means for sending a gas liquefied in the liquefactor to the system of columns.
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:
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.
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.
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.
The first compartment 1 is thermally insulated using a pulverulent insulator such as perlite.
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.
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.
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.
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.
At least a portion of the gas compressed in the compressor can be expanded in the turbine M, depending on the methods.
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.
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.
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).
The framework does not contain a scrubbing or distillation column, as the liquefactor itself does not contain these elements.
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.
A portion of the feed gas is liquefied either in the exchanger or downstream of the exchanger and forms the product of the method.
The feed gas may be nitrogen, hydrogen, natural gas.
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.
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.
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.
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.
The turbine M is connected to provide cold to the at least one heat exchanger E.
The assembly comprising the framework O in
During manufacture and transport (
During on-site installation (
The framework O can take the form of a standardized container to facilitate transport.
The framework O comprises means for sending a flushing gas to the compartments 1, 4 and 5 (if present for the latter two compartments).
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.
The framework may be lifted in a single operation, being preferably formed as a single piece.
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.
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.
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2302424 | Mar 2023 | FR | national |
