Offshore floating liquefied natural gas production plant and method of construction thereof

Abstract

The present application relates to a kind of offshore floating liquefied natural gas production device and its construction method.The production device is modified from decommissioned natural gas transport ship, it includes modified ship bow section, modified ship stern section, newly-built ship section and function module.Modified ship bow section is modified from the ship bow section of decommissioned natural gas transport ship.Modified ship stern section is modified from the ship stern section of decommissioned natural gas transport ship.Newly-built ship section is connected between modified ship bow section and modified ship stern section.Function module is arranged on newly-built ship section, for carrying out the production of LNG.The LNG after production can be stored to the original LNG storage tank of decommissioned natural gas transport ship.The production device makes full use of the existing structure and equipment of decommissioned natural gas transport ship, reduces the material waste and energy consumption of newly-built device, reduces the investment of fixed cost, and can be completed in relatively short time during modification and construction, so that FLNG device is put into operation faster, shortens the construction period, improves economic benefit.

Description

Technical Field

[0001] This invention relates to the field of marine engineering equipment technology, and in particular to an offshore floating liquefied natural gas production unit and its construction method. Background Technology

[0002] With the increasing global demand for natural gas, the development of offshore natural gas has become increasingly important. Floating liquefied natural gas (FLNG) production facilities are an emerging offshore natural gas development technology that allows for the direct liquefaction and storage of natural gas at sea, avoiding the high costs and complexities of laying long-distance subsea pipelines.

[0003] However, building new FLNG facilities is costly and time-consuming. Decommissioned LNG carriers, on the other hand, possess relatively intact hull structures, power systems, and storage facilities. Therefore, converting decommissioned LNG carriers into FLNG production facilities is a pressing issue that needs to be addressed. Summary of the Invention

[0004] One objective of this invention is to overcome the shortcomings of existing technologies and provide a floating offshore liquefied natural gas (LNG) production facility. To solve the aforementioned technical problems, this invention adopts the following technical solution:

[0005] A floating liquefied natural gas (LNG) production unit, converted from a decommissioned LNG carrier, which has multiple LNG storage tanks; comprising: The converted bow section was made from the bow section of a decommissioned natural gas carrier. The stern section of the ship has been converted from the stern section of a decommissioned natural gas carrier. The newly constructed midship section connects the converted bow section and the converted stern section. The functional module, located in the newly built midship section, is used for LNG production, and the produced LNG can be stored in LNG storage tanks.

[0006] In one embodiment, the functional module includes a pretreatment module, a liquefaction module, and a liquefaction post-processing module. The liquefaction module is arranged downstream of the pretreatment module, and the liquefaction post-processing module is arranged downstream of the liquefaction module. The pretreatment module is used to preprocess the collected natural gas, the liquefaction module is used to liquefy the pretreated natural gas into LNG, and the liquefaction post-processing module is used to depressurize the LNG for storage in an LNG storage tank.

[0007] In one embodiment, the functional module includes a heavy hydrocarbon processing module, which is located downstream of the liquefaction module and is used to process heavy hydrocarbons generated during the natural gas liquefaction process.

[0008] In one embodiment, the offshore floating liquefied natural gas production unit includes several isolation modules, each of which is respectively located on the newly built midship section and between the pretreatment module and the liquefaction module, as well as between the liquefaction module and the liquefaction post-treatment module and the heavy hydrocarbon treatment module.

[0009] In one embodiment, the offshore floating liquefied natural gas production unit includes several midships pipe gallery modules, each of which is located on the midships section of the newly built vessel and is used to arrange pipes and cables connecting the pretreatment module, liquefaction module, liquefaction post-treatment module, and heavy hydrocarbon processing module.

[0010] In one embodiment, the modified bow section is provided with at least one bow platform for generating additional deck area, the modified stern section is provided with at least one stern platform for generating additional deck area, and the hull of the newly built midship section is adapted to the modified bow section and the modified stern section.

[0011] In one embodiment, the stern section of the converted vessel is equipped with at least a living area module, a central operation control module, a hazardous waste liquid storage module, and a stern pipe gallery module for laying pipelines and cables.

[0012] In one embodiment, the bow section of the modified vessel is equipped with at least a modified electrical system, a modified mooring system, an acid gas treatment module, and a bow gallery module for laying pipes and cables.

[0013] Another object of the present invention is to provide a method for constructing an offshore floating liquefied natural gas production unit, comprising the following steps: Provide a decommissioned LNG carrier, cut the decommissioned LNG carrier into bow and stern sections; The bow and stern sections were modified separately to form modified bow and stern sections. Construct a new midship section and build functional modules for LNG production; The newly built midship section will be joined with the modified stern section and modified bow section to complete the construction of the main hull, and the functional modules will be integrated into the main hull.

[0014] In one embodiment, the newly built midship section is joined with the modified stern section and the modified bow section to complete the construction of the main hull. The step of assembling the functional modules into the main hull includes: The newly built midship section and the modified stern section will be joined together to form the midship and stern section; The pretreatment module, liquefaction module, and liquefaction post-treatment module of the functional modules were respectively hoisted and assembled onto the stern and midship section; The modified bow section and the midship section will be joined together to form the main hull; The remaining modules of the assembly function module were hoisted onto the main hull.

[0015] In one embodiment, after the step of joining the newly built midship section with the modified stern section to form the stern-midship section, the method further includes: adding temporary buoys to the side of the stern-midship section. After the pre-processing module, liquefaction module, and post-liquefaction processing module of the functional modules are respectively hoisted and assembled into the midship section, the temporary pontoons are removed.

[0016] In one embodiment, before the step of joining the newly built midship section with the modified stern section to form the midship section, the stern section pipe gallery module and the hazardous waste liquid storage module are hoisted onto the modified stern section. Before joining the bow section and the midship section of the converted vessel, the bow gallery module and acid gas treatment module are hoisted onto the bow section of the converted vessel.

[0017] In one embodiment, the modification of the stern section includes at least: Add a stern platform, living quarters module, and central operations control module; Modify the ship's power system.

[0018] In one embodiment, the modification of the bow section includes at least: Add a bow pontoon; Upgrade the ship's electrical system; upgrade the ship's propulsion system and mooring system.

[0019] In one embodiment, prior to the step of cutting up the decommissioned LNG carrier, the process further includes: conducting a full-ship assessment of the decommissioned LNG carrier and cleaning out any remaining LNG and other hazardous substances inside; After assembling the functional modules into the main hull, the process also includes: completing the connection and testing of pipelines, electrical systems, and control systems between modules and between modules and the main hull, and improving the overall ship safety system.

[0020] As can be seen from the above technical solution, the present invention has at least the following advantages and positive effects: In this invention, the offshore floating liquefied natural gas (LNG) production unit is converted from a decommissioned LNG carrier. It involves adding a new midship section to the original hull, and the functional module for LNG production is added to this new midship section. This module can directly receive natural gas at sea and liquefy it to produce LNG. Thus, this production unit can realize the production, storage, and transportation of LNG. Furthermore, by fully utilizing the existing structure and equipment of the decommissioned LNG carrier, such as steam boilers and LNG storage facilities, it reduces material waste and energy consumption associated with building a new unit, lowering fixed costs. Compared to building a new FLNG carrier, it can be converted and constructed in a relatively short time, allowing the FLNG unit to be put into operation more quickly, shortening the construction cycle, and improving economic efficiency. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a decommissioned natural gas carrier in an embodiment of the present invention.

[0022] Figure 2 This is a side view of the offshore floating liquefied natural gas production unit according to an embodiment of the present invention.

[0023] Figure 3 This is a top view of the offshore floating liquefied natural gas production unit according to an embodiment of the present invention.

[0024] Figure 4 yes Figure 3 The module layout of the device shown is illustrated in the schematic diagram.

[0025] Figure 5 This is a flowchart of a method for constructing an offshore floating liquefied natural gas production unit according to an embodiment of the present invention.

[0026] Figure 6 yes Figure 5 The flowchart shown is for step S40.

[0027] The annotations in the attached figures are explained as follows: 10 - Decommissioned natural gas carrier; 11 - Bow section; 12 - Stern section; 13 - LNG storage tank; 20 - Conversion of bow section; 21 - Bow platform; 22 - Conversion of electrical system; 23 - Conversion of mooring system; 24 - Acid gas treatment module; 25 - Bow utility tunnel module; 30 - Converted stern section; 31 - Stern platform; 32 - Living quarters module; 33 - Central operation control module; 34 - Hazardous materials and waste liquid storage module; 35 - Stern pipe gallery module; 40 - New midship section; 41 - Isolation module; 42 - Midships utility tunnel module; 50 - Functional module; 51 - Pretreatment module; 52 - Liquefaction module; 53 - Liquefaction post-treatment module; 54 - Heavy hydrocarbon treatment module. Detailed Implementation

[0028] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit the present invention.

[0029] In the description of this application, it should be understood that, in the embodiments shown in the accompanying drawings, the indications of direction or positional relationships (such as up, down, left, right, front, and back, etc.) are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the production apparatus or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. These descriptions are appropriate when these elements are in the positions shown in the accompanying drawings. If the description of the positions of these elements changes, these directional indications also change accordingly.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] The present invention relates to an offshore floating liquefied natural gas (LNG) production facility and its construction method, primarily providing a method for converting decommissioned LNG carriers into offshore floating LNG production facilities (FLNG), and the resulting offshore floating LNG production facility. This invention achieves the reuse of decommissioned vessel resources while reducing the cost of constructing an FLNG facility and significantly shortening the construction time.

[0032] The following will describe in detail the offshore floating liquefied natural gas production unit and its construction method of the present invention with reference to the accompanying drawings.

[0033] The offshore floating liquefied natural gas (LNG) production unit (hereinafter referred to as FLNG unit) of this invention is converted from a decommissioned natural gas carrier. For example, see [link to relevant documentation]. Figure 1As shown, the decommissioned LNG carrier 10 generally includes the original hull, which can be divided into a bow section 11 and a stern section 12 along the bow-stern direction. The original hull has multiple LNG storage tanks 13 for storing LNG. For example, there can be four LNG storage tanks 13, with two LNG storage tanks 13 arranged on the bow section 11 and the remaining two LNG storage tanks 13 arranged on the stern section 12.

[0034] See Figure 2 and Figure 3 As shown, the FLNG unit includes a modified bow section 20, a modified stern section 30, a newly built midship section 40, and a functional module 50.

[0035] The modified bow section 20 is converted from the bow section 11 of the decommissioned LNG carrier 10. For example, the modification of the bow section 11 of the decommissioned LNG carrier 10 includes, but is not limited to: removing the original anchor chain and winch mooring system and installing a modified mooring system 23, such as a soft steel arm mooring system; retaining the original ship boiler and adding several gas turbine generator sets and several dual-fuel generators to form a modified power system 22; removing the original pipe racks, pipelines, outfitting, etc. above the deck and installing new pipe racks, pipelines, outfitting, etc. Specific details can be found in the FLNG unit construction method below and determined based on the actual construction situation.

[0036] Optionally, refer to Figure 3 and Figure 4 The bow section 20 of the converted vessel is equipped with at least a converted electrical system 22, a converted mooring system 23, an acid gas treatment module 24, and a bow pipe gallery module 25 for laying pipes and cables.

[0037] The modified power system 22 may include the original ship boiler, several newly added gas turbine generator sets, and several dual-fuel generators, which can meet the power requirements of the FLNG unit. The modified mooring system 23 may be a soft steel arm mooring system or a turret mooring system, which can meet the requirements of the FLNG unit to be permanently / long-term stationed at sea and ensure continuous production operations.

[0038] The sour gas treatment module 24 is one of the functional modules adapted to LNG production. Its main function is to neutralize sour gases, including carbon dioxide and hydrogen sulfide, generated after natural gas desouring. The bow pipe gallery module 25 is one of the structural modules adapted to LNG production and transmission. It can be used to arrange pipelines, cables, etc., adapted to LNG production and transmission. The number of bow pipe gallery modules 25 can be set as needed. Optionally, multiple bow pipe gallery modules 25, such as R05, R06, R07, R08, and R09, can be installed on the bow section 20 of the converted vessel.

[0039] refer to Figure 3 and Figure 4 The modified stern section 30 is converted from the stern section 12 of the decommissioned LNG carrier 10. For example, the modification of the stern section 12 of the decommissioned LNG carrier 10 includes, but is not limited to: demolishing the original living quarters and control center area, and installing a new living quarters module 32 and a central operation control module 33; demolishing the original lifesaving system and helicopter deck, and installing a new lifesaving system and helicopter deck; demolishing the original pipe racks, cranes, pipelines, outfitting, etc. above the deck, and installing new pipe racks, cranes, pipelines, outfitting, etc. For details, please refer to the construction method of the FLNG unit below, and determine according to the actual construction situation.

[0040] Optionally, the stern section 30 of the converted vessel is equipped with at least a living area module 32, a central operation control module 33, a hazardous waste liquid storage module 34, and a stern pipe gallery module 35 for laying pipelines and cables.

[0041] The living area module 32 is where the ship's crew lives and rests. It can include various configurations of living quarters, recreation rooms, a gym, and a restaurant to meet the daily living and leisure needs of the crew. The central operation control module 33 is the control center for the FLNG unit's operation and LNG processing systems. Daily operational monitoring and control of the FLNG unit are performed by staff in this module.

[0042] The hazardous waste storage module 34 is one of the functional modules adapted to LNG production. Its main purpose is to house the storage tanks for hazardous waste. Hazardous waste generated during natural gas processing and liquefaction can be collected via pipeline to designated tanks, and then transported via pipeline to the storage tanks on the hazardous waste storage module 34. The tanks can then be transported to land by service vessels for onshore treatment of the hazardous waste. The stern pipe gallery module 35 is one of the structural modules adapted to LNG production and transmission. It can be used to arrange pipelines, cables, etc., adapted to LNG production and transmission.

[0043] See Figure 2 and Figure 3 The newly built midship section 40 connects between the converted bow section 20 and the converted stern section 30. The newly built midship section 40 is a hull section that is rebuilt independently of the original hull, and it is mainly used to install facilities and equipment for LNG production.

[0044] The hull of the newly built midship section 40 is adapted to the modified bow section 20 and the modified stern section 30. For example, the deck width of the newly built midship section 40 is consistent with that of the modified bow section 20 and the modified stern section 30.

[0045] Optionally, such as Figure 3As shown, the modified bow section 20 is provided with at least one bow platform 21 for generating additional deck area. That is, the modification of the original bow section 11 also includes the addition of bow platforms 21. The bow platforms 21 can be constructed on the port and / or starboard sides of the original bow section 11, at the end where it connects to the newly built midship section 40. The number of bow platforms 21 can be set as needed.

[0046] The modified stern section 30 is provided with at least one stern platform 31 to generate additional deck area. That is, the modification of the original hull stern section 12 also includes the addition of stern platform 31s. The stern platform 31 can be constructed on the port and / or starboard side of the original hull stern section 12, located at the end where it connects to the newly constructed midship section 40. The number of stern platform 31s can be set as needed.

[0047] refer to Figure 3 The hull of the newly built midship section 40 is compatible with the modified bow section 20 and stern section 30. That is, the deck width of the newly built midship section 40 is at least the sum of the original hull deck width and the platform width. This allows the newly built midship section 40 to have a larger deck area, providing more installation space for LNG production process equipment. Furthermore, the increased platform size helps increase hull volume and buoyancy, improving the overall displacement and load-bearing capacity, and enhancing collision safety performance.

[0048] Furthermore, for FLNG units moored at sea, the amplitude of swaying directly affects the operating efficiency of the upper process equipment. By increasing the beam, the pontoon can effectively reduce the ship's roll and pitch movements, providing a more stable platform for the fragile liquefaction process equipment, thereby enhancing stability and improving equipment operating efficiency.

[0049] It is worth noting that the modification of the original bow section 11 and stern section 12 can also include structural reinforcement of the original hull to meet the load-bearing requirements of the LNG production equipment. The construction of the new midship section 40 can include the design and reinforcement of the midship hull structure according to the load-bearing requirements of the LNG production equipment. Specific details can be determined based on actual circumstances.

[0050] See Figure 3 As shown, functional module 50 is installed on the newly built midship section 40 and is used for LNG production. The produced LNG can be stored in LNG storage tank 13.

[0051] For example, see Figure 4Functional module 50 may include a pretreatment module 51, a liquefaction module 52, and a liquefaction post-treatment module 53. The pretreatment module 51 is used to pre-treat the collected natural gas. For example, pretreatment of natural gas may include removing solid impurities and water, removing acid gas, removing mercury, and dehydration. Natural gas collected from the seabed carries liquids such as water, as well as solid impurities. In the pretreatment module 51, these liquids and solid impurities are initially separated. After the initial separation of liquids and solid impurities, the natural gas enters the acid gas removal equipment to separate carbon dioxide and hydrogen sulfide. The generated acid gas can be transported through pipelines to the acid gas treatment module 24 for harmless treatment.

[0052] After being treated to remove acid gas, the natural gas then enters a mercury removal unit to separate any mercury entrained in the natural gas, thus preventing the mercury from corroding subsequent process equipment. The natural gas then passes through a molecular sieve for dehydration, reducing the water molecule content as low as possible to prevent the formation of natural gas hydrates and other solid substances that could clog equipment and pipelines during the liquefaction process. The natural gas, after these processes, then enters liquefaction module 52 for further liquefaction.

[0053] The liquefaction module 52 is located downstream of the pretreatment module 51 and is used to liquefy pretreated natural gas into LNG. There can be two liquefaction modules 52, such as M03 and M04. Each liquefaction module 52 may include the core equipment for natural gas liquefaction: a cold box and a refrigerant compressor (gas turbine). The natural gas pretreated in the pretreatment module 51 is transported via pipeline to the liquefaction module 52 and enters the cold box. After two stages of cooling in the cold box, it becomes liquid natural gas, i.e., liquefied natural gas (LNG). The LNG is then transported via pipeline to the liquefaction post-processing module 53 for depressurization and pressure energy recovery.

[0054] The liquefaction post-processing module 53 is located downstream of the liquefaction module 52. Its main function is to depressurize the LNG for storage in the LNG storage tank 13. For example, the LNG liquefied by the liquefaction module 52 is transported via pipeline to the liquefaction post-processing module 53 for depressurization. For instance, if the LNG pressure is around 50 bar upon arrival at the liquefaction post-processing module 53, it needs to be reduced to around 1 bar before being transported to the LNG storage tank 13 for storage. The liquefaction post-processing module 53 may be equipped with a flash evaporation device. After the LNG is depressurized by the flash evaporation device, some natural gas gas will be separated from the LNG. This portion of natural gas gas (i.e., BOG) is separated by a gas-liquid separator and can then be transported via pipeline to the liquefaction module 52 for use as fuel for a gas turbine. The LNG after gas separation is then transported via pipeline to the LNG storage tank 13 for storage.

[0055] Optionally, the liquefaction post-processing module 53 may also be equipped with a pressure energy recovery device that can convert the pressure energy of LNG into electrical energy.

[0056] Optionally, the liquefaction post-treatment module 53 may also include amine regeneration equipment. For example, after the natural gas undergoes acid removal in the pretreatment module 51, the liquid amine used for acid removal can be piped to the amine regeneration equipment in the liquefaction post-treatment module 53, where the amine is regenerated by heating. The waste gas generated during amine regeneration can be piped to the acid gas treatment module 24 for harmless treatment.

[0057] See Figure 4 The functional module 50 may also include a heavy hydrocarbon processing module 54 located downstream of the liquefaction module 52. The heavy hydrocarbon processing module 54 is used to process the heavy hydrocarbons generated during the natural gas liquefaction process. For example, the heavy hydrocarbon processing module 54 may be equipped with heavy hydrocarbon processing equipment, such as a heavy hydrocarbon removal tower or a scrubbing tower.

[0058] In the liquefaction module 52, natural gas is cooled in the cold box to form heavy hydrocarbons. These heavy hydrocarbons are processed and separated in the heavy hydrocarbon processing module 54, and can be sent to the liquefaction plant or to the modified power system 22 as fuel for the dual-fuel main engine and turbine, depending on demand.

[0059] See Figure 4 The FLNG unit may include several isolation modules 41, such as M21, M22, and M23. Each isolation module 41 is respectively located on the newly constructed midship section 40 and between the pretreatment module 51 and the liquefaction module 52, and between the liquefaction module 52 and the liquefaction post-treatment module 53 and the heavy hydrocarbon processing module 54. In this embodiment, each isolation module 41 is mainly used to isolate the pretreatment module 51, the liquefaction module 52, the liquefaction post-treatment module 53, and the heavy hydrocarbon processing module 54, thereby helping to improve the operational safety of the FLNG unit and avoiding or reducing the impact of a fire or explosion in one module on adjacent modules.

[0060] See Figure 4The FLNG unit may include several midships pipe rack modules 42, such as R01A, R01B, R02, R03, and R04. Each midships pipe rack module 42 is respectively installed on the newly built midships section 40 and is used to arrange pipes and cables connecting the pretreatment module 51, liquefaction module 52, liquefaction post-treatment module 53, and heavy hydrocarbon processing module 54. In this embodiment, each midships pipe rack module 42 is mainly used to arrange pipes and cables connecting the pretreatment module 51, liquefaction module 52, liquefaction post-treatment module 53, and heavy hydrocarbon processing module 54, thereby enabling centralized and modular arrangement of pipes and cables between the various functional modules 50 in the FLNG unit. This improves the centralization of the FLNG unit's pipes and cables and enhances the ease of operation and maintenance.

[0061] See Figure 3 The FLNG unit can be equipped with unloading platforms, lifeboat platforms, helicopter platforms, cranes, etc., and the specific configuration can be determined according to actual needs.

[0062] Please see Figure 5 As shown, the construction method of an offshore floating liquefied natural gas production unit according to an embodiment of the present invention includes the following steps: S10, providing a decommissioned natural gas carrier 10, cutting the decommissioned natural gas carrier 10 to form a bow section 11 and a stern section 12.

[0063] For example, in step S10, based on the base's production capacity and the overall plan of projects under construction, the decommissioned LNG carrier 10, after arriving at the shipyard, will be moored at the dock. A shore crane will be used to dismantle the lifeboats, rescue boats, living quarters, helicopter deck, bow anchor chain and winch, and related pipe racks, cranes, pipelines, outfitting, etc., from the original hull. After removing these items, the original hull will be towed to a deep-water dock, where two barges will jointly lift and tow it to a dry dock for floating. The bow and stern sections of the original hull will then be cut.

[0064] Optionally, prior to cutting up the decommissioned LNG carrier 10, the process may also include: conducting a full-ship assessment of the decommissioned LNG carrier 10 and cleaning up any residual LNG and other hazardous substances inside.

[0065] For example, firstly, a comprehensive structural integrity assessment is conducted on the decommissioned LNG carrier 10: this includes checking the thickness of the hull plates, the quality of welds, and the airtightness of the compartments, and using non-destructive testing techniques such as ultrasonic testing and magnetic particle testing to determine whether there are defects such as cracks or corrosion in the hull. For instance, for an LNG carrier that has been in service for many years, the focus is on the corrosion of its cargo tank areas.

[0066] Thoroughly clean the ship's interior of residual natural gas and other hazardous substances: for example, use professional cleaning equipment and chemical agents to clean the liquid cargo tanks, pipeline systems, etc., to ensure a safe construction environment and avoid accidents such as fires and explosions during subsequent modifications.

[0067] Following assessment and cleanup, the outer plating of the hull can be inspected and repaired, with severely corroded sections replaced. The internal compartments of the hull are then re-divided according to the layout requirements of the FLNG unit, removing unnecessary bulkheads and equipment. Afterwards, the decommissioned LNG carrier 10 can be cut to form the bow section 11 and stern section 12.

[0068] S20, the bow section 11 and stern section 12 are modified respectively to form the modified bow section 20 and the modified stern section 30.

[0069] For example, during the implementation of S20, after the original hull is cut, the bow section 11 is transported by one barge and the stern section 12 is transported by another barge to the dock. The bow section 11 and stern section 12 are then slid ashore. The bow section 11 and stern section 12 are then modified on the shore to form the modified bow section 20 and modified stern section 30, respectively. The modifications to the bow section 11 and stern section 12 include, but are not limited to: adding stilts, such as bow stilt 21 and stern stilt 31; modifying and strengthening the hull structure; installing a modified mooring system 23, such as a soft steel arm mooring system; adding several gas turbine generator sets and several dual-fuel generators to form a modified power system 22; arranging a new living quarters module 32 and a central operation control module 33; and arranging a new lifesaving system, helicopter deck, etc.

[0070] Optionally, the modification of the stern section 12 may include at least: adding a stern platform 31, a living area module 32, and a central operation control module 33; and modifying the ship's power system, such as the propulsion and positioning system. The living area module 32 and the central operation control module 33 may be carried out simultaneously during the modification of the original bow and stern sections, or during the construction of the new midship section 40 or functional module 50, depending on the specific circumstances.

[0071] Optionally, the modifications to the bow section 11 may include at least: adding a bow platform 21; modifying the ship's electrical system, such as adding several gas turbine generator sets and several dual-fuel generators; modifying the ship's propulsion system, such as the propulsion and positioning system; and modifying the mooring system, such as adopting a soft steel arm mooring system.

[0072] After the modification is completed, before the modified stern section 30 is launched, for example, before the step of joining the newly built midship section 40 with the modified stern section 30 (described below), the stern pipe gallery module 35 and the hazardous waste liquid storage module 34 are hoisted onto the modified stern section 30. The construction of the stern pipe gallery module 35 and the hazardous waste liquid storage module 34 can be carried out simultaneously with the modification of the stern section 12, or during the construction of the newly built midship section 40 or the functional module 50, depending on the specific circumstances.

[0073] Before launching the modified bow section 20, and before the steps described below for merging the modified bow section 20 with the midship section, the bow utility tunnel modules 25, such as R05, R06, R07, R08, R09, and the acid gas treatment module 24, are hoisted onto the modified bow section 20. The bow utility tunnel modules 25 and the acid gas treatment module 24 can be installed simultaneously during the modification of the bow section 11, or during the construction of the new midship section 40 or functional module 50, depending on the specific circumstances.

[0074] S30, construct a new midship section 40, and construct a functional module 50 for LNG production.

[0075] For example, the construction of the new midship section 40 may include, but is not limited to, constructing the hull of the new midship section 40 based on the deck width of the converted bow section 20 and stern section 30. Furthermore, the new midship section 40 is an assembly of major equipment, with large equipment and dense piping installed on each deck below the main deck. For instance, after the equipment and pump room above the baseline on the first deck are installed, the second deck section is joined; the space above the second deck can be used to install three dual-fuel main engines, transformers, and other room equipment, after which the third deck section is joined; the space above the third deck is used to install functional modules 50, etc. Before the new midship section 40 is launched, the equipment installation and watertight sealing work on each deck must be completed.

[0076] For example, the construction of functional module 50 may include, but is not limited to: modular design and construction of natural gas processing and liquefaction equipment and related pipelines, electrical and instrumentation systems. The equipment and related systems may be divided according to the natural gas processing and liquefaction process, equipment functions, and safety requirements, and arranged on different structurally independent modules. That is, a pretreatment module 51, a liquefaction module 52, a liquefaction post-processing module 53, and a heavy hydrocarbon processing module 54 may be constructed separately. Additionally, midship pipe gallery modules 42 and isolation modules 41 may be constructed.

[0077] In this embodiment, the modular design of each module significantly shortens the construction cycle and reduces construction costs. Because each module is constructed independently of the hull structure, the construction of the hull and each module can be carried out in parallel. Furthermore, since different modules are structurally relatively independent, the construction of each module can also be carried out concurrently, thereby greatly shortening the construction cycle and reducing construction costs.

[0078] It is worth noting that there is no strict order between steps S20 and S30, and the two steps can be performed simultaneously.

[0079] S40, the newly built midship section 40 is joined with the modified stern section 30 and modified bow section 20 to complete the construction of the main hull, and the functional module 50 is joined to the main hull.

[0080] For example, see Figure 6 As shown, step S40 may include: S41 involves joining the newly built midship section 40 with the modified stern section 30 to form the main midship section. For example, when implementing S41: First, open the dock gate, tow the newly built midship section 40 to the main dock, and position it with mooring lines according to its mooring location within the dock.

[0081] Step 2: The modified stern section 30 is brought into the dry dock, and the dock gate is closed. The ballast on the modified stern section 30 is further fine-tuned according to the required closing precision, adjusted to a position close to the newly built midship section 40. After the newly built midship section 40 and the modified stern section 30 are aligned, welding is performed above the waterline at the closing point.

[0082] Step 3: Drain the dry dock, and place the newly built midship section 40 and the modified stern section 30 on the piers. Complete the welding of the joint below the waterline of the newly built midship section 40 and the modified stern section 30 in the dry dock to obtain the main midship section.

[0083] S42, the pre-processing module 51, liquefaction module 52 and liquefaction post-processing module 53 of functional module 50 are respectively hoisted and assembled onto the stern-midship section.

[0084] Optionally, after the welding of the newly built midship section 40 and the modified stern section 30 is completed, for example, when the stern midship section is mounted on the pier, a temporary pontoon can be added to the side of the stern midship section. This can help increase the waterline area and improve the stability of the subsequent module hoisting process. It is understood that in other embodiments, the temporary pontoon can also be added after the construction of the newly built midship section 40 and before the welding of the newly built midship section 40 and the modified stern section 30. That is, the temporary pontoon can be added only to the side of the newly built midship section 40, and the specific configuration can be determined according to the actual working conditions.

[0085] When implementing step S42, firstly, after completing the welding of the newly built midship section 40 and the modified stern section 30, when the midship section is placed on the pier, the gantry crane can be used to complete the welding of one of the midship section pipe gallery modules R02 on the newly built midship section 40.

[0086] Afterwards, the pretreatment module 51, liquefaction module 52, and liquefaction post-treatment module 53 are respectively docked. After the stern-ambulance section floats, the pretreatment module 51, liquefaction module 52, and liquefaction post-treatment module 53 are hoisted and assembled in the dry dock. For example, the four modules can be assembled with the stern-ambulance section in the following order: liquefaction module M03 → liquefaction module M04 → pretreatment module 51 → liquefaction post-treatment module 53 (the assembly process is carried out according to the load adjustment procedure, with a maximum draft of 7.1 meters). Then, the stern-ambulance section is undocking and docked at the pier to hoist the midship section pipe gallery modules R01A and R01B.

[0087] Optionally, the midships pipe gallery module R03 can be hoisted before the pretreatment module 51 is hoisted or before the bow section 20 of the modified ship is joined, depending on the actual working conditions.

[0088] Optionally, after the pretreatment module 51, liquefaction module 52, and liquefaction post-treatment module 53 of functional module 50 are respectively hoisted and assembled into the midship section, the temporary pontoons are removed. Alternatively, in other embodiments, the removal of the temporary pontoons can also be carried out before the entire ship leaves the dock, depending on the specific circumstances.

[0089] S43, the modified bow section 20 is joined with the midship section to form the main hull. For example, in step S43, the dock piers are pre-arranged according to the pier layout drawings in the dock, and the modified bow section 20 enters the dock and floats. The midship section enters the dock, the dock gate is closed, and it is positioned with the modified bow section 20. The modified bow section 20 and the midship section are then positioned, floated, and joined together, and the welding work above the waterline is completed to obtain the main hull.

[0090] S44, hoist the remaining modules of the assembly function module 50 onto the main hull. For example, step S44 can be implemented as follows: the main hull is placed on a pier, and the isolation modules M21, M22, and M23 are hoisted onto the main hull. Then, the entire ship is undocking and moved to a deep-water dock to assemble the remaining modules, such as the midships pipe gallery module R04 and the heavy hydrocarbon processing module 54.

[0091] For example, at least the following important tasks should be completed before the entire ship leaves the dry dock: (1) The closure seam is fully welded and passes inspection.

[0092] (2) The closure of the opening resulted in the completion of the installation of the outfitting and structure, which were not closed before the water was launched.

[0093] (3) The temporary pontoons installed before the stern and midship sections are launched shall be removed before leaving the dock.

[0094] (4) Complete the tightness test of the closure opening and ensure that the tightness test is qualified after the temporary process hole in the dock is sealed.

[0095] (5) Ensure the integrity of the paint finish on the outer plating of the entire ship before it leaves the dock.

[0096] (6) Complete all markings and water level gauge markings on the outer panel.

[0097] (7) Complete the dismantling of temporary scaffolding before leaving the dock.

[0098] It is understood that in other embodiments, the method of joining the newly built midship section 40 with the modified stern section 30 and the modified bow section 20 can also be to first join the newly built midship section 40 with the modified bow section 20, and then join the modified stern section 30. The specific method can be set according to the actual working conditions.

[0099] It is understood that in other embodiments, the hoisting sequence of each module can also be changed and adjusted as needed to save on the use of large floating cranes and improve hoisting efficiency.

[0100] In one embodiment, after assembling the functional module 50 into the main hull, the process may further include: completing the connection and testing of pipelines, electrical systems, and control systems between the modules and between the modules and the main hull, thereby improving the overall ship safety system.

[0101] For example, after the module is assembled with the main hull, the pipelines, electrical systems and other systems between the modules and the main hull are connected and tested. This includes, but is not limited to, systems that provide support and services for natural gas processing and liquefaction from the main hull to the module, as well as related systems such as liquefied natural gas and steam systems from the module to the main hull.

[0102] For example, installing an automated control system can centrally monitor and control processes such as natural gas liquefaction, ship propulsion systems, and cargo handling systems. By collecting various parameters such as temperature, pressure, and flow rate through sensors, operators can remotely adjust equipment operating status from a control room, achieving automation and intelligentization of the production process.

[0103] For example, gas detection systems can be installed in critical areas of the ship, such as cargo tanks and production areas, to detect combustible and toxic gases. Once a gas leak is detected, the system can immediately issue an alarm and activate emergency measures such as ventilation and fire suppression.

[0104] In addition, a fire suppression system must be installed. Besides traditional water-based fire extinguishing systems, specialized fire suppression systems suitable for extinguishing LNG fires, such as dry powder fire suppression systems and high-pressure water mist systems, are also required. Furthermore, emergency escape routes and rescue equipment must be provided to ensure the safe evacuation of crew members in emergencies.

[0105] The offshore floating liquefied natural gas (LNG) production unit of this invention is converted from a decommissioned natural gas carrier. A new midship section is added to the original hull, and the functional module for LNG production is added to this new midship section. This functional module can directly receive natural gas at sea and liquefy it to produce LNG. Thus, this production unit can realize the production, storage, and transportation of LNG. Furthermore, by fully utilizing the existing structure and equipment of the decommissioned natural gas carrier, such as steam boilers and LNG storage facilities, it reduces material waste and energy consumption associated with building a new unit, and lowers fixed cost investment. Compared to building a new FLNG carrier, it can be converted and constructed in a relatively short time, allowing the FLNG unit to be put into operation more quickly, shortening the construction cycle, and improving economic efficiency.

[0106] The above embodiments are merely illustrative examples of structures. The structures in each embodiment are not fixed combinations. In the absence of structural conflicts, the structures in multiple embodiments can be arbitrarily combined and used.

[0107] Although the invention has been described with reference to several typical embodiments, it should be understood that the terminology used is illustrative and exemplary, and not restrictive. Since the invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A floating liquefied natural gas (LNG) production facility, converted from a decommissioned LNG carrier, the decommissioned LNG carrier having multiple LNG storage tanks; characterized in that, include: The modified bow section is converted from the bow section of the decommissioned natural gas carrier. The modified stern section is converted from the stern section of the decommissioned natural gas carrier. A new midship section is constructed, which connects the modified bow section and the modified stern section. A functional module is installed on the newly built midship section. The functional module is used to produce LNG, and the produced LNG can be stored in the LNG storage tank.

2. The offshore floating liquefied natural gas production unit according to claim 1, characterized in that, The functional modules include a pretreatment module, a liquefaction module, and a liquefaction post-processing module. The liquefaction module is located downstream of the pretreatment module, and the liquefaction post-processing module is located downstream of the liquefaction module. The pretreatment module is used to preprocess the collected natural gas, the liquefaction module is used to liquefy the pretreated natural gas into LNG, and the liquefaction post-processing module is used to depressurize the LNG for storage in the LNG storage tank.

3. The offshore floating liquefied natural gas production unit according to claim 2, characterized in that, The functional module includes a heavy hydrocarbon processing module, which is located downstream of the liquefaction module and is used to process heavy hydrocarbons generated during the natural gas liquefaction process.

4. The offshore floating liquefied natural gas production unit according to claim 3, characterized in that, It includes several isolation modules, each of which is respectively disposed on the newly built midship section and located between the pretreatment module and the liquefaction module, as well as between the liquefaction module and the liquefaction post-treatment module and the heavy hydrocarbon treatment module.

5. The offshore floating liquefied natural gas production unit according to claim 3, characterized in that, It includes several midships pipe gallery modules, each of which is respectively installed on the midships section of the newly built ship and is used to arrange pipes and cables connecting the pretreatment module, the liquefaction module, the liquefaction post-treatment module and the heavy hydrocarbon treatment module.

6. The offshore floating liquefied natural gas production unit according to claim 1, characterized in that, The modified bow section is provided with at least one bow platform for generating additional deck area, the modified stern section is provided with at least one stern platform for generating additional deck area, and the hull of the newly built midship section is adapted to the modified bow section and the modified stern section.

7. The offshore floating liquefied natural gas production unit according to claim 1, characterized in that, The stern section of the modified vessel is equipped with at least a living area module, a central operation control module, a hazardous waste liquid storage module, and a stern pipe gallery module for laying pipelines and cables.

8. The offshore floating liquefied natural gas production unit according to claim 1, characterized in that, The bow section of the modified vessel is equipped with at least a modified power system, a modified mooring system, an acid gas treatment module, and a bow pipe gallery module for laying pipes and cables.

9. A method for constructing an offshore floating liquefied natural gas production unit, characterized in that, Includes the following steps: Provide a decommissioned natural gas carrier, cut the decommissioned natural gas carrier to form a bow section and a stern section; The bow section and the stern section are modified respectively to form a modified bow section and a modified stern section; Construct a new midship section and build functional modules for LNG production; The newly built midship section, the modified stern section, and the modified bow section are joined together to complete the construction of the main hull, and the functional modules are then joined to the main hull.

10. The method for constructing an offshore floating liquefied natural gas production unit according to claim 9, characterized in that, The steps of assembling the newly built midship section, the modified stern section, and the modified bow section to complete the construction of the main hull, and assembling the functional modules into the main hull, include: The newly built midship section and the modified stern section are joined together to form the midship and stern section; The pre-processing module, liquefaction module, and liquefaction post-processing module of the functional modules are respectively hoisted and assembled onto the stern-midship section; The modified bow section is joined to the midship section to form the main hull; The remaining modules of the assembly function module are hoisted onto the main hull.

11. The method for constructing an offshore floating liquefied natural gas production unit according to claim 10, characterized in that, After the step of joining the newly built midship section with the modified stern section to form the stern-midship section, the method further includes: adding temporary buoys to the side of the stern-midship section; After the pre-processing module, liquefaction module, and liquefaction post-processing module of the functional modules are respectively hoisted and assembled into the midship section, the temporary pontoon is removed.

12. The method for constructing an offshore floating liquefied natural gas production unit according to claim 10, characterized in that, Before joining the newly built midship section with the modified stern section to form the midship section, the stern access module and the hazardous waste liquid storage module are hoisted onto the modified stern section. Before joining the modified bow section to the midship section, the bow gallery module and acid gas treatment module are hoisted onto the modified bow section.

13. The method for constructing an offshore floating liquefied natural gas production unit according to claim 9, characterized in that, The modifications to the stern section include at least: Add a stern platform, living quarters module, and central operations control module; Modify the ship's power system.

14. The method for constructing an offshore floating liquefied natural gas production unit according to claim 9, characterized in that, The modifications to the bow section include at least: Add a bow pontoon; Upgrade the ship's electrical system; upgrade the ship's propulsion system and mooring system.

15. The method for constructing an offshore floating liquefied natural gas production unit according to claim 9, characterized in that, Prior to the step of cutting up the decommissioned LNG carrier, the process also includes: conducting a full ship assessment of the decommissioned LNG carrier and cleaning out any residual LNG and other hazardous substances inside; After assembling the functional modules into the main hull, the process also includes: completing the connection and testing of pipelines, electrical systems, and control systems between modules and between modules and the main hull, and improving the overall ship safety system.

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