FLEXIBLE INSTALLATION OF A HYDROCARBON LIQUEFACTION UNIT

Abstract

Natural gas liquefaction unit including at least one cryogenic cold box having at least one heat exchanger; a fixed assembly zone on its outer wall; at least one closed loop nitrogen refrigeration cycle; at least one device for equipment required for implementing the liquefaction of a natural gas stream from a hydrocarbon supply stream; at least one interconnection module comprising a pipe holder means and a set of pipes and valves, designed to connect said at least one cold box to at least one equipment device for the cycle for refrigerating and/or separating C6+ type hydrocarbon elements contained in the natural gas, wherein the interconnection module rests on a frame allowing it to be handled and is connected to the cold box and to the other method or equipment sub-assemblies located around said fixed assembly zone.

Claims

1. Natural gas liquefaction unit comprising: at least one cryogenic cold box (2) comprising: at least one heat exchanger; a fixed assembly zone (8) on its outer wall; at least one closed loop nitrogen refrigeration cycle; at least one device (3) for equipment required for implementing the liquefaction of a natural gas stream from a hydrocarbon supply stream; at least one interconnection module (4) comprising a pipe holder means and a set of pipes and valves (5, 6, 7), designed to connect said at least one cold box (2) to at least one equipment device for the cycle for refrigerating and/or separating C6+ type hydrocarbon elements contained in the natural gas, characterized in that the interconnection module (4) rests on a frame allowing it to be handled and is connected to the cold box (2) and to the other method or equipment sub-assemblies (3) located around said fixed assembly zone (8).

2. Unit according to the preceding claim, characterized in that the interconnection module (4) particularly comprises one or more elements selected from among control valves, manual valves, sample connections, pipes, pre-cut panels with valve actuators, instruments, vapour sources, lighting, ladders and platforms, pre-wired junction boxes, platforms for instrument/electric cables, pipe supports, channeling.

3. Unit according to claim 2, characterized in that the interconnection module (4) comprises one or more elements selected from among control valves, manual valves, valve actuators.

4. Unit according to one of the preceding claims, characterized in that said other method or equipment sub-assemblies (3) are required to implement at least one method function selected from among the compression of the nitrogen of the refrigeration cycle, the overpressurization of the nitrogen of the refrigeration cycle, the expansion of the nitrogen of the refrigeration cycle, the cooling of the nitrogen of the refrigeration cycle, the liquefaction of the natural gas stream, the separation of the C6+ type hydrocarbons contained in the natural gas, the interconnection module (4) being devoid of such method or equipment sub-assemblies.

5. Unit according to one of the preceding claims, characterized in that the refrigeration cycle comprises a first means for compressing the nitrogen of the refrigeration cycle, a means for cooling the nitrogen of the refrigeration cycle, a second means for compressing the nitrogen of the refrigeration cycle, said second compression means comprising two booster compressors coupled to two respective expansion means, said booster compressors being configured to compress the nitrogen of the refrigeration cycle at an identical pressure.

6. Unit according to one of the preceding claims, characterized in that said frame has a metal structure.

7. Unit according to one of the preceding claims, characterized in that said at least one heat exchanger is a brazed aluminium heat exchanger.

8. Use of a unit as defined in one of the preceding claims for liquefying a natural gas stream.

9. Method for starting a liquefaction unit as defined in claims 1 to 6, comprising the following steps: on-site installation of a closed loop nitrogen refrigeration cycle and of a cold box (2) comprising: at least one heat exchanger; a fixed assembly zone (8) on its outer wall; on-site installation of an interconnection module (4) comprising a pipe holder means and a set of pipes and valves (5, 6, 7), designed to connect said at least one cold box (2) to at least one equipment device (3) for the cycle for refrigerating and/or separating C6+ type hydrocarbon elements contained in the natural gas; fixing said interconnection module (4) to the cold box (2) and to at least one equipment device (3), allowing the implementation of the liquefaction method using said cold box (2), already available on the site.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0054] 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:

[0055] The FIGURE shows a representation of a schematic diagram of a liquefaction system according to one embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0056] FIG. 1 shows a representation of a schematic diagram of a liquefaction unit according to one embodiment of the invention.

[0057] In FIG. 1, the hydrocarbon fluid liquefaction unit 1 comprises: [0058] at least one cryogenic cold box 2 comprising: [0059] at least one heat exchanger; [0060] a fixed assembly zone 8 on its outer wall; [0061] a device 3 for the various equipment required for implementing the cold fluid required for the liquefaction of a natural gas stream from a hydrocarbon supply stream; [0062] an interconnection module 4 comprising a pipe holder means and a set of pipes, control valves, and electricity connection and instrumentation 5, 6, 7, designed to connect said at least one cold box 2 to the at least one equipment device 3 for the cycle for refrigerating and/or separating C6+ type hydrocarbon elements contained in the natural gas.

[0063] The interconnection module 4 rests on a frame that allows it to be handled and is connected to the cold box in the vicinity of said assembly zone.

[0064] Advantageously, the interconnection module comprises one or more elements selected from among control valves, manual valves, valve actuators. Thus, the important elements for controlling the liquefaction assembly are arranged in the interconnection module, the assembly and the on-site handling of which are simpler and safer, which facilitates the assembly of these elements and facilitates access for maintenance. The safety of the unit is improved. In particular, one or more valves are of the Pressure Safety Valve (PSV) type. According to a particular embodiment, the unit comprises one or more pressure safety valves, all of which are arranged in the interconnection module.

[0065] The feed stream NG can be a stream of natural gas, which can be pre-treated, in which one or several substances, such as sulphur, carbon dioxide, water, are reduced, so as to be compatible with cryogenic temperatures, as is known in the prior art.

[0066] The heat exchangers are known from the prior art and can have various arrangements of their feed flows and refrigerant streams.

[0067] When the flow of liquefied, or at least partially liquefied, hydrocarbons is liquefied natural gas (LNG), the temperature can be approximately −150° C. to −160° C.

[0068] The liquefaction of the feed stream NG is carried out by virtue of a fluid or an expanded cooling nitrogen current in one or more coolant circuits for pre-cooling the feed stream NG.

[0069] A heat exchange module comprises walls for thermally insulating the heat exchanger from the outside and comprises a framework allowing the heat exchange module to be transported so that it can be fixed.

[0070] The framework can be made of stainless steel bars in order to reduce the effects of thermal diffusion. Furthermore, this framework can assume the form of a container, thus forming the edges of a rectangular parallelepiped, also referred to as a right cuboid. Thus, it is simple to transport. The framework of the heat exchange module can also comprise means for facilitating installation.

[0071] An element is understood to be a module, or a compressor, or an expansion device or a circuit of a module, or a cooler, or a separator.

[0072] Connections are understood to be a tube or pipe that may or may not be insulated and that can comprise valves or restrictors.

[0073] A stream is understood to be one or more fluids, that may be in the liquid phase or in the gaseous phase or both, circulating through elements of the system.

[0074] An inlet is understood to be a point at which the fluid enters, therefore giving the stream a direction of circulation. In other words, an inlet of a first element is connected downstream of an outlet of a second element.

[0075] An outlet is understood to mean that the fluid exits an element and therefore provides a direction of circulation for the stream. In other words, an outlet of a first element is connected upstream of an inlet of a second element.

[0076] Connected means connected for transporting a fluid, for example, an inlet connected to an element implies that a fluid can transition from the element to the inlet either directly or via other elements.

[0077] Connected is understood to mean the connection of two elements (the outlet of one element to an inlet of another element) for transporting fluid using connections or connected directly to one another (an outlet directly connected to an inlet of an element (without pipe)). In other words, there are no other elements between the two elements.

[0078] Fixed is understood to mean the physical assembly of one element to another element in order to secure them together.

[0079] An expanded stream is understood to mean the stream downstream of an expansion circuit and upstream of a compressor.

[0080] A compressed stream is understood to mean the stream upstream of an expansion circuit and downstream of a compressor.

[0081] The liquefied natural gas resulting from the method that is the subject matter of the present invention subsequently can be, for example, transferred to a storage or transportation device.

[0082] The method that is the subject matter of the present invention particularly enables the investment expenditure to be optimized. Indeed, having a modular system allows several arrangements of the modules to be proposed and thus allows the installation research costs, as well as the manufacturing cost, to be reduced.

[0083] 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.