Patent Application
20230392860
The present invention is directed to a system and a method for the production of liquefied natural gas (LNG).
Natural gas (NG) is routinely transported from one location to another location in its liquid state as Liquefied Natural Gas (LNG). Liquefaction of the natural gas makes it more economical to transport as LNG occupies only about 1/600 of the volume that the same amount of natural gas does in its gaseous state. After liquefaction, LNG is typically stored in cryogenic containers, typically either at or slightly above atmospheric pressure. LNG can be regasified before distribution to end users through a pipeline or other distribution network at a temperature and pressure that meets the delivery requirements of the end users.
Wellhead gas is subjected to gas pre-treatment to remove contaminants prior to liquefaction. The hydrogen sulphide and carbon dioxide can be removed using a suitable process such as amine absorption. Removal of water can be achieved using conventional methods, for example, a molecular sieve. Depending on the composition of contaminants present in the inlet gas stream, the inlet gas stream may be subjected to further pre-treatment to remove other contaminants, such as mercury and heavy hydrocarbons prior to liquefaction.
Liquefaction is achieved using processes which typically involve compression, expansion and cooling. Such processes are applied in technologies such as C3/MR process, the AP-X™ process, the Cascade Process, the Mixed Fluid Cascade process or the Double Mixed Refrigerant or Parallel Mixed Refrigerant process.
Refrigerants are cycled in one or more refrigeration loops to reduce the temperature of the treated gas to a temperature of around −160° C. to form LNG. This results in warming of the respective refrigerant which must be compressed for recycle to the liquefaction process and subsequent expansion. Compressors used for this duty may be centrifugal compressors driven by gas turbines or electric motors. The refrigeration loop may comprise coolers to remove heat added due to cooling and liquefying of the natural gas and due to the compression of the respective refrigerants.
Over the last 10 to 15 years, the LNG industry has seen a shift from traditional stick-built LNG facilities to modular built projects. Examples are available in, for instance, Australia, the Russian arctic, and Canada. A main driver to change to modular built LNG trains is to move much of the site construction work to an offsite fabrication yard. At the yard, process units can be built in modular form in a controlled, predictable environment. Remote fabrication of modules may result in increased productivity and lower labor rates, better quality, reduced chance of safety incidents, and improved predictability with respect to cost and schedule.
US-2014/053599-A1 discloses a liquefied natural gas production facility comprising a plurality of spaced-apart modules for installation at a production location to form a production train having a major axis and a minor axis, each module having a module base for mounting a plurality of plant equipment associated with a selected function assigned to said module, the module base having a major axis and a minor axis; and a plurality of heat exchangers arranged to run parallel to the major axis of the production train to form a heat exchanger bank having a major axis and a minor axis
US-2016/0010916-A1 discloses a liquefied natural gas production process for producing a product stream of liquefied natural gas at a production location, said process comprising: a) designing a plurality of modules for installation at the production location to form an installed production train; (b) designing an air-cooled heat exchanger bank including: a first row of air-cooled heat exchanger bays, and, an adjacent parallel second row of air-cooled heat exchanger bays; (c) arranging a first sub-section of the first row of heat exchanger bays at an elevated level vertically offset from and towards a first edge of a first module base to form a covered section of the first module base, the first module base being designed and sized to include an uncovered section for mounting a selected piece of process equipment, wherein the first module includes the first subsection of the first row of heat exchanger bays without including a sub-section of the second row of heat exchanger bays; (d) arranging a first sub-section of the second row of heat exchanger bays at an elevated level vertically offset from and towards a first edge of a second module base to provide a covered section of the second module base, wherein the second module includes the first sub-section of the second row of heat exchanger bays without including a sub-section of the first row of heat exchanger bays; and (e) positioning the first edge of the second module base at the production location towards the first edge of the first module base.
Modularization, which for instance aimed to circumvent high labor costs by constructing modules of facilities at a location having reduced costs of labor and subsequently move the preconstructed modules to the LNG production location, has disappointed in practice. Production costs remained relatively high compared to conventional stick-built facilities. The general view is that, unless local labor costs are particularly high and/or productivity is particularly low, a plant with stick-built LNG production trains result in the lowest costs, albeit with an extended construction schedule, increased exposure to local influences and potential quality issues. The conventional modular approach generally is seen to lead to a better quality of the LNG production train, yet at the expense of higher capital expenditure.
Historically, the choice to use onshore modular built instead of stick-built for LNG production trains is generally taken after the basic (process) layout of the plant is fixed. Conversion of the plant design to a modular setup typically results in relatively large modules requiring a lot of structural steel and relatively few equipment items per module. The large number of modules required to span the still relatively large plant layout results in a relatively large residual in-field hook-up scope as there are many piping connections. As a result, the full system must be leak tested on site. Additionally, most of the cabling has to be installed and tested on site. The latter are both relatively time consuming and costly.
WO2019110769 in the name of applicant provides a modular liquefaction train for LNG production, with reduced capital expenditure and footprint. Footprint herein refers to the area of the liquefaction train. Area herein refers to the surface included within the boundaries of the liquefaction train.
Despite the advantages and cost savings provided by the modular designed liquefaction systems as for instance disclosed in the references above, there remains a need to explore alternative designs to further reduce capital expenditure and footprint.
In one aspect, a facility for the production of liquefied natural is provided. The facility comprises an inside battery limit (ISBL) comprising a liquefaction train. The liquefaction train comprises a plurality of modules with each module being adapted to perform at least one process step associated with liquefied natural gas production. The plurality of modules comprise
The train further comprises a first mixed refrigerant cycle comprising a first mixed refrigerant and a second mixed refrigerant cycle comprising a second mixed refrigerant connected to the liquefaction module for cooling a gas stream to produce the liquefied natural gas. The train further comprises a primary cooling loop to cool at least a process stream from each module and the first mixed refrigerant and the second mixed refrigerant against a first coolant comprising clean water. The primary cooling loop is a closed clean water cooling loop and the cooling is against an ambient temperature. The train further comprises a first plurality of heat exchangers through which the primary cooling loop extends, and the cooling by the primary cooling loop is via heat exchange in at least the first plurality of heat exchangers with respect to the first coolant. More than 50% of the first plurality of heat exchangers are printed circuit heat exchangers which are adapted to provide at least 80% of the cooling against the ambient temperature.
Optionally, the liquefaction train further comprises a second plurality of heat exchangers through which the primary cooling loop extends to cool the first coolant by heat exchange with a second coolant, and the facility further comprises
Optionally, the second coolant comprises water from a cooling tower system, sea water, or air.
Optionally, each of the plurality of modules of the liquefaction train has a predetermined maximum weight threshold, which can be 6000 tonnes.
Optionally, for the liquefaction train, the first module having a first side engaging a first side of the second module, and the second module having a second side opposite the first side engaging a first side of the fourth module. The liquefaction train further comprises a first module series comprising the first module engaging the second module engaging the fourth module, the first module series being aligned with and arranged adjacent to a second module series comprising the third module arranged between the first compressor on one side and the second compressor on the opposite side.
Optionally, the liquefaction train further comprises:
Optionally, the liquefaction train further comprises:
Optionally, the liquefaction train further comprises a pipe-rack for supporting conduits, the pipe-rack extending through at least the first module, the second module and the fourth module.
Optionally, the first mixed refrigerant cycle comprises a single precool heat exchanger. The first mixed refrigerant cycle can further comprise a compressor intercooler adapted to cool first mixed refrigerant compressed by the first compressor without condensing the first mixed refrigerant, an outlet of the compressor intercooler being connected to a subsequent stage of the first compressor.
Optionally, the liquefaction train has a capacity of production of liquefied natural gas in the range of about 2 to 4 MTPA.
According to another aspect, the disclosure provides a method of producing liquefied natural gas using a system as described above.
The system and method described above have been designed with modularization in mind. The result provides a significant cost saving and footprint reduction with respect to convention systems, including modular built systems. Details are provided in the detailed description section below.
The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.
Certain terms used herein are defined as follows:
The term “LNG” refers to liquefied natural gas.
“Natural Gas Liquids” or “NGLs” are hydrocarbon components of natural gas that are separated from the gas state in the form of liquids. NGLs may also be referred to as condensate.
“LPG” relates to Liquid Petroleum Gases. LPG is a subset of NGL. LPG are C3 to C4s with high vapor pressure. LPG typically includes propane and butane. Trace amounts of C5 can be found in LPG due to the fractionation process.
“Heavy Hydrocarbons” or “HHC” are hydrocarbon components comprising five carbon atoms or more (C5+ components), including aromatics.
The term “LNG production train” refers to an assembly comprising process units used for the pre-treatment of a natural gas feed stream to remove contaminants and provided treated gas, and process units used for receiving the treated gas and subjecting the treated gas to cooling to form liquefied natural gas.
The term “plant” may refer to the LNG production plant including one or more LNG production trains.
The term “facility” may refer to an LNG production plant, but may alternatively refer to an assembly in general.
The term “stick-built” refers to an LNG production train which has sections built in subsequent order at the production location. Herein, stick-built is similar to conventional construction. Both refer to construction of a production train or another section of a plant predominantly at a production location. Herein, production location is the location of the plant itself.
In contrast, the term “module” refers to a section of a plant that may be preassembled at a construction or assembly location remote from the production location. Each module is typically designed to be transported from the construction or assembly location to the production location. Modules may be transported by towing or on floating barges, or by land using, for instance, rail or truck. After each module is moved from the construction or assembly location to the production location, the module is positioned in a suitable pre-determined orientation to suit the needs of a given LNG production facility.
As used herein, ISBL has its ordinary meaning known by one of ordinary skill in the art, including being defined as comprising all equipment and associated components (piping, etc.) that act upon the primary feed stream of a process, which is the process for the production of the liquefied natural gas in this instance (including removing contaminants from a natural gas feed stream to provide treated gas and cooling the treated gas to form liquefied natural gas). ISBL is functional-based and refers to equipment and other components that are solely dedicated to a particular process (e.g., process for the production of the liquefied natural gas). Such equipment may be referred to as the ISBL equipment or ISBL units.
Correspondingly, Outside Battery Limits (OSBL) as used herein also has its ordinary meaning known to one of ordinary skill in the art, including being defined as utilities, common facilities, and other equipment and components not included in the ISBL definition. OSBL refers to systems (equipment pieces and associated components) that support several units, including ISBL units. Typical OSBL equipment includes cooling towers, water treatment facilities, tanks farms, LNG loading equipment, etc.
“Metric Tons” or “Tonnes” is a unit of weight equal to 1,000 kilograms.
LNG plant capacity is usually specified in million metric tonnes per year (mt/y or mtpa).
The capital expenditure to fabricate and build an LNG facility comprising modular built LNG trains is typically driven by a few key levers, such as:
Weight of respective modules is relevant to capital expenditure due to transportation costs, and the costs of steel to construct the respective modules. Module weight is an indicator for estimating costs. Module weight is typically linked to the number of fabrication hours in the yard as well as site hours and civil scope to support the modules on site.
Conventional modular liquefaction facilities typically improve on one or two of the levers listed above. As explained herein below, embodiments of the system of the disclosure target and improve on at least a majority of, or even all of, the levers listed above. As a result, capital expenditure to construct the system of the present disclosure is significantly reduced with respect to conventional liquefaction facilities, including existing modular liquefaction facilities. Herein, a system according to the disclosure is compared to conventional plants, wherein the system of the disclosure has at least a similar production capacity and a similar energy efficiency. In addition to efficiency and capacity, the system of the present disclosure also enables to achieve close to best in class green-house gas (GHG) performance. The LNG production system of the disclosure can be built faster and at lower cost. This is done by combining one or more, preferably all, of the features described below. A description of each item respectively follows herein below, with reference to the drawings.
A first step involves a selection of a liquefaction process. Various liquefaction processes are available. A comparison is for instance provided in the article “Analysis of Process Efficiency for Baseload LNG Production” by T. J. Edwards et al. of Air Products and Chemicals Inc. According to the article, the C3MR and DMR have similar thermodynamic efficiencies. Both are more efficient than the cascade liquefaction process. According to the article, C3MR “has distinct advantages over the other process cycles, e.g. by way of simpler control, less costly and more reliable equipment, and ease of startup.” Consequently, the most commonly used liquefaction process for existing plants is the C3MR process. Relatively small LNG plants can use SMR (a process using a single mixed refrigerant cycle) or a nitrogen (N2) cooling cycle as liquefaction technology, but these technologies provide relatively poor liquefaction efficiency and increased specific green-house gas (GHG) emissions.
Despite the general preference in the industry for the C3MR process, Applicant has found that the DMR process provides certain benefits in combination with the modular setup. For instance, the Dual Mixed Refrigerant (DMR) process has a lower equipment count than C3MR and optimized cascade. Also, DMR enables to use lighter equipment.
The pre-cool cycle of the DMR process can be based on single stage (single heat exchanger) or dual stage (two heat exchangers), as explained below.
At a generic level, the liquefaction system 1 comprises two consecutive cooling cycles 4 and 6. The pre-cool cycle 4 may comprise at least one, for instance two heat exchangers 10 and 12 and at least one pre-cool refrigerant compressor 14. The cycle 4 may also include at least one cooler 15. Pre-cool refrigerant conduits 16 guide pre-cool refrigerant from the compressor 14 through the two heat exchangers 10 and 12 and back. Refrigerant conduits 16 may comprise conduits 16a to 16f. Together, conduits 16 constitute a loop to circulate a refrigerant. The refrigerant circulated in loop 4 may be referred to as, for instance, precool refrigerant, precool mixed refrigerant (PMR) or first refrigerant.
The first pre-cool heat exchanger 10 may operate at a first pressure and the second pre-cool heat exchanger 12 may operate at a second pressure. Herein, the first pressure typically exceeds the second pressure. As a result, the first heat exchanger may be referred to as high-pressure (HP) pre-cool heat exchanger. The second heat exchanger 12 may be referred to as low-pressure (LP) pre-cool heat exchanger.
The main cooling cycle 6 comprises at least one main heat exchanger 20 and at least one main refrigerant compressor 22. The cycle 6 may include one of more coolers 23, 25. Main refrigerant conduits 24 extend from the compressor 22 through the two heat exchangers 10 and 12, subsequently through the at least one main heat exchanger 20, and back to the compressor 22. The cycle 6 may comprise a separator 26 to split the mixed refrigerant of the main cycle 6 in a heavy mixed refrigerant 27 and a light mixed refrigerant 28. Refrigerant conduits 24 may comprise conduits 24a to 24f. Together, conduits 24 constitute a loop to circulate a refrigerant. The refrigerant circulated in loop 6 via conduits 24 may be referred to as, for instance, main refrigerant, mixed refrigerant or second refrigerant.
The gaseous feed stream 2 is routed via conduits extending through the two heat pre-cool exchangers 10 and 12, and subsequently through the at least one main heat exchanger 20, to provide at least partially condensed or liquefied gas 30.
Both the pre-cooling cycle 4 and the main cooling cycle 6 may use a mixed or multi-component refrigerant to pre-cool and subsequently condense or liquefy the gaseous feed stream 2. Expanded pre-cool mixed refrigerant 50, 52 provides cooling duty to the pre-cool heat exchangers 10, 12 respectively and to all streams routed through the inside of said heat exchangers. Expanded heavy mixed refrigerant 29 and expanded light mixed refrigerant 31 provide cooling duty to the main cryogenic heat exchanger 20 and to all streams routed through the inside of the MCHE 20.
For further details of the cooling cycles and the operation thereof, reference is made to, for instance, U.S. Pat. No. 6,370,910 or U.S. Pat. No. 6,658,891.
The system 1 typically also includes a system 40 to remove natural gas liquids. The embodiment of system 1 shown in
A conduit 150 may connect an outlet of the first pre-cool heat exchanger 10 with an inlet of the first separator 140. A second conduit 152 connects an upper outlet 154 of the first separator 140 with an inlet 156 of the second pre-cool heat exchanger 12. A third conduit 158 connects an outlet 160 of the second pre-cool heat exchanger 12 with an inlet 162 of the second separator 142. A fourth conduit 164 connects an upper outlet 166 of the second separator 142 with an inlet 168 of the main heat exchanger 20.
An optional bypass conduit 60 may be provided, connecting the inlet of the bundle 80 of the first heat exchanger 10 to an outlet of said bundle 80. The conduit may be provided with a valve 62. The valve 62 may be controllable within a range between a closed position and an open position, allowing to adjust a flow of gas through the bypass conduit 60. The latter allows at least a section or part of the gas 2 to bypass the bundle 80 in the heat exchanger 10.
A fifth conduit 170 is connected to a lower outlet 172 of the first separator. Liquids can be removed from the first separator 140 via the conduit 170. A sixth conduit 176 is connected to a lower outlet 178 of the second separator 142. Liquids can be removed from the second separator 142 via the conduit 176. Optionally, the liquids from the second separator 142 can be recycled back to the first separator via line 173, either by gravity or optionally aided with a pump (not shown). Liquids may be removed, bypassing the first separator 140 via line 179. The conduits 173 and/or 179 may be provided with valves 63 and 65 respectively, allowing to control the flow in each conduit.
The pre-cool cycle 4 may include two or more coolers 15, 17. Thereof, the cooler 15 may be referred to as precool condenser. The cooler 15 may provide an at least partly condensed refrigerant stream 182. The precool cycle 4 may include a knock-out vessel or other gas-liquid separator 180. A lower outlet for liquids 184 of the vessel 180 is connected to the conduit 16d. The outlet 184 provides a condensed (liquid) refrigerant stream 186 to the precool heat exchanger 10.
The embodiment of
The system 111 may comprise a knock-out drum 300 to ensure only vaporous precool refrigerant is provided to the precool compressor 14. the compressor 14 may be provided with a first feedback conduit 302 with valve 304 to loop refrigerant back to the inlet of the compressor, via the knock-out drum 300. The cooler 15 of the liquefaction system 111 may be a de-superheater. The cooler 15 may be succeeded by another cooler 310, referred to as condenser. The cooler 310 may at least partially condense the compressed refrigerant. A second feedback conduit 312, provided with valve 314, may connect the refrigerant flow between the cooler 15 and the condenser 310 with a middle inlet 316 of the compressor 14. An outlet of the condenser 310 may be connected to PMR accumulator 180. A lower outlet 184 of the accumulator may be connected to a lower inlet 320 of tube bundle 322 for precool refrigerant in the heat exchanger 10. An outlet of the tube bundle 322 is connected to an expansion device 324, such as a JT valve. An outlet of the expansion device is connected to inlet 98. The system 111 may comprise a single heat exchanger 10 included in the precool cycle 4.
The gas tube bundle 84 may extend though the entire heat exchanger 10. Exit 84 of the gas tube bundle may be connected to the separator 140. The gas outlet 154 of the separator 140 may be connected to inlet 168 of the main heat exchanger 20.
In use, the single heat exchanger 10 of
In the embodiment of
The embodiments of
In a practical embodiment, the heat exchangers in the precool loop 4 and main liquefaction loop 6 are based on coil wound heat exchangers (CWHE). Alternatively, one or more of the heat exchangers 10, 12, 20 may be replaced with Plate Fin heat exchangers (PFHE).
The refrigerant compressors (PMR compressor 22 and MR compressor(s) 14) can be driven by an efficient aeroderivative gas turbine or alternatively by an electric motor. The driver selection, however, does not change the overall layout of the MML train.
A particularly beneficial layout for a system 200 according to the present disclosure is shown in
An inside battery limit (ISBL) scope 202 of the system 200 comprises a number of modules. The modules include, for instance, four process modules. First module 210 is, for instance, an acid gas removal unit (AGRU). The AGRU typically comprises an absorber for flushing the gas with a liquid solvent. For details, reference is made to, for instance, WO2016150827. The absorber 212 may comprise a column type absorber placed next to and connected to the first module 210. Other process units, such as a unit 214 comprising a solvent drain drum and/or pump, may also be arranged next to and connected to the first module. These latter equipment components can also be placed inside the respective module.
A second module 220 may comprise a dehydration unit 222 and/or a mercury removal unit 224. The dehydration unit typically comprises a number of, for instance three, molecular sieve units (molsieves) 226. Alternatively, the Mercury removal unit (single vessel) may be arranged in the AGRU module 210. For details, see for instance US20180311609 or U.S. Pat. No. 8,521,310.
Third module 230 may comprise a liquefaction unit. Compressors 14 and 22 for the precool cycle and the main cooling cycle respectively may be positioned on opposite sides of the third module. See
The first precool heat exchanger 10 may be positioned on the same side of the third module as the pre-cool compressor unit 14. The optional second precool heat exchanger 12 may be arranged next to the first precool heat exchanger 10. The main heat exchanger 20 may be arranged on the opposite side of the third module, typically on the same side as the main refrigerant compressor 22. Substantially all other equipment relating to the liquefaction system (such as the exemplary systems shown in
As shown in
As shown in
A fourth module 240 may comprise equipment for condensate stabilization, heat transfer fluid (HTF) and at least one closed cooling water unit (explained in more detail below). Condensate stabilization herein refers to equipment for processing NGLs removed from the feed gas. Some of the NGLs may for instance in part be used as refrigerant make-up. In part the NGLs may be prepared for sale as product.
Additional equipment shown in
The modules 210, 220 and 240 may be arranged adjacent to one another, the respective sides of one module engaging the side of the respective adjacent module. The liquefaction module or third module 230 with the respective compressors 14, 22 on opposite sides may be arranged longitudinally aligned with the modules 210, 220, 240. In a preferred embodiment, the conduits and the pipe rack 280 extend through the modules 210, 220, 230 and 240. The integrated pipe rack is included in the module weights (as referenced herein, for instance herein below).
The system 200 may comprise a pipe rack 280. The pipe rack supports and guides pipes or conduits 282, for instance for feeding and removing process streams to and from the respective modules 210 to 240.
In a practical embodiment, the pipe rack guides the pipes 282 to one of the modules, for instance to the fourth module 240, and extends through the inside of said module. The pipe rack 280 and the associated conduits 282 may extend through the inside of the modules, for instance through the modules 240, 220 and 210 respectively. See for instance
The module 230 may be arranged adjacent to the modules 240, 220 and 210. The latter modules together form a first series of interconnected modules. The third module, with the first compressor 14 and the second compressor 22 on opposite sides, may form a second series. The compressors may be modularized. Alternatively, the compressors 14 and 22 may be ‘stick-built’ (i.e. arranged and provided with cabling and piping onsite). Conduits for respective process streams may extend from the first series of modules to the third module 230 of the second series. Also, the heat exchangers 10, 12 and 20, which typically are coil wound heat exchangers, may be included in a dedicated module. Alternatively, these heat exchangers may be stick built.
Traditionally, LNG trains have a dedicated pipe-rack extending on the side and along the length of the LNG train and its equipment. The latter generally holds for both stick-built and modular built LNG trains. All individual process units are typically connected to the pipe rack. The system 200 applies an integrated pipe rack 280 which runs through at least two or the modules, preferably through at least three modules. This will enable the majority of the hookups between process units and piperack to be completed in the fabrication yard (i.e. remotely) and reduces the number of hookups required at the production location which in turn reduces the number of construction hours at the production site.
Similar reductions of required hook ups are achieved for other process streams. The latter may include, for instance, a cycle for so-called heat transfer fluid, for which the number of interconnections on site between the modules and other conduits is limited from about 13 to less than seven. Thus, the layout and composition of the system of the present disclosure reduced hookups and consequently the time required onsite to connect respective prefabricated modules and construct the system 200.
Each module comprises one or more full process units. In other words, all equipment associated with a respective process unit is only comprised in one of the modules, with caveat that selected equipment may be arranged on the side of, i.e. outside, the respective module (see, for instance,
As an alternative to the layout shown in
In a practical embodiment, predetermined equipment is arranged outside the modules. For instance, long lead items will be arranged outside modules. Long-lead herein refers to items which take relatively long to construct and/or to get delivered. For instance, the main liquefaction heat exchangers 10, 12, 20 and the carbon-dioxide (CO2) absorber column 212 are typically the heaviest pieces of process equipment and are arranged outside the respective process modules to maintain the optimum module weight. In addition, the main liquefaction heat exchangers 10, 20 and CO2 absorber column 212 are long lead items that would determine the critical path of the process modules, so installing them separately reduces the module delivery schedule.
In a practical embodiment, the liquefaction capacity per train or system 200 is between 2 to 4 MTPA. Although larger train sizes do have the advantage of a relatively low equipment count for a given capacity, larger trains typically suffer from very large and heavy equipment with associated large diameter pipes. The combination increases the footprint, equipment weight and module weight (per unit of capacity in MTPA). By selecting a smaller train size, the equipment density in the module can be increased significantly. Relatively low capacity liquefaction trains have the benefit of small equipment and associated small diameter pipes. Relatively low capacity liquefaction trains typically have as a disadvantage an increased number of equipment, instrumentation, valves and other bulks for a given capacity, which tend to increase the capital expenditure. It also becomes impractical to operate so many trains for a given capacity. Bulks herein may relate to all kinds of smaller pieces of equipment, such as relief valves, drain systems, etc. required for safe operation of the LNG train. Models have indicated that modular built LNG trains having a capacity in the range of 2 to 4 MTPA have the lowest capital expenditure for the same total capacity of all trains combined.
As an example,
The figure shows the total equipment weight required for a 14 MTPA facility as a function of the liquefaction train size. Two effects are apparent: 1) smaller trains (and hence more trains) do reduce the overall equipment weight, contrary what is normally assumed in industry, and 2) For an equal train size, total equipment weight for a facility according to the disclosure is significantly smaller than the total equipment weight of the reference modular LNG plant.
By applying a mid-scale concept rather than a large-scale concept, the total equipment weight per MTPA will decrease. This weight reduction is for instance driven by pressure vessels (and equipment that can be considered as such) as they represent the highest weight fraction of total installed weight and provide the highest weight reduction when downscaling. Overall, by constructing two trains each having half the capacity of a single larger train, the weight of equipment in all modules combined can be reduced. As an example, the selection of four smaller modules of 3.5 mtpa each provides a reduction of the total equipment weight of about 27% with respect to two trains having a 7 mtpa capacity each. Combining smaller trains with substantially all other measures as disclosed herein provides a further reduction in equipment weight in the order of 73%. A strong impact on the latter weight reduction is due to selection of light weight equipment, such as PCHEs, see for instance
In an embodiment, the system 200 of the disclosure uses water for cooling a process stream rather than air. Cooling process stream herein relates to, for instance, coolers 15, 17, 23, and 25 (see
In a practical embodiment one or more of the coolers 15, 17, 23, 25 (
Based on the above, applicant found a number of interlinking effects which reinforce each other. The embodiments as disclosed herein use these interlinking effects to provide optimal results for a modular setup. For instance, by reducing the weight of individual pieces of equipment (Mmi), the corresponding weight of required piping (Mpi), structural (Msi) and electrical & instrumentation weight (Mei) is also reduced. See
Optionally, the printed circuit heat exchangers included in the system 200 of the disclosure may be provided according to the setup and used according to the method as disclosed in US20200182552. This embodiment provides a further reduction in weight and size of the heat exchangers. Consequently, also the piping density and weight is reduced even more. Said further reduction in size and/or weight may be in the order of 20 to 45% (compared to state-of-the-art printed circuit heat exchangers), depending on specifics. As explained with respect to
The selection of relatively light equipment, in particular the application of Printed Circuit Heat Exchangers (PCHE) for water cooling instead of the conventional shell-and-tube heat exchangers significantly reduces the size and weight of heat transfer equipment in the LNG train, and the volume and weight of associated conduits. In the system 200 of the disclosure, a majority of the heat exchangers for cooling a process stream with respect to a temperature of the environment (also referred to as ambient temperature, or ambient) are based on PCHEs. Said temperature of the environment is typically transferred via a medium such as air or water. The phrase majority herein does allow to include a few aircoolers as well. A few herein indicates that the number of air coolers is significantly less than the number of water coolers, for instance about 10% of the total at most, or preferably about 5% at most (in number and/or in cooling capacity).
The plot of
Herein, Module density (Dmod)=Ds (structural density)+Dp (piping density)+Dm (mechanical density)+De (density of ‘e&i’, i.e. electrical and instrumentation; this relates to electrical cables and equipment such as controllers and transformers).
The required module volume is determined by, for instance, the equipment types, equipment count, equipment size and equipment spacing, amount of piping and number of mini FARs and substations. Maximization of high-density equipment like PCHEs plays a relatively big role. The weight of PCHEs is significantly lower than the weight of shell-and-tube heat exchangers which are used conventionally. The weight may be about a factor 5 lower. Also, the volume of PCHEs is smaller (more than a factor five), resulting in increased equipment density. There is also an impact on piping due to reduction of parallel configurations.
As can be seen in the table above, the structural density and piping density are fairly constant, implying structural weight and piping weight scale proportionally with module volume. This seems reasonable as bigger modules require more steel for support structures, such as beams and columns, to support its own weight. Similarly, bigger modules will have equipment arranged spaced apart more, leading to an increase in piping weight.
The graph of
Preferably, the maximum weight of each module 210, 220, 230, 240 is limited to a predetermined maximum threshold. In a practical embodiment, said threshold, also referred to as the maximum module weight, is about 5000 or 6000 tonnes. Line 456 in
Modules exceeding said threshold will typically increase fabrication time in the yard, with more manhours, which will typically increase the overall project schedule of the project. See
The graph of
The primary cooling loops 512, 514, 516 may cycle a first coolant, for instance comprising clean water. Clean herein refers to the absence of impurities in the water. The clean water herein may refer to softened water or demineralized water. Also included in the clean water may be additives, such as a corrosion inhibitor and anti-freeze. Anti-freeze herein may comprise glycol. The water purity of the clean water may typically be in accordance with an accepted standard, such as EN 12952-12, EN 12953-10, VGB-M 407, or VGB-S-010-T-00. Softened water herein refers to water wherein following a water softening process calcium (Ca), magnesium (Mg), and certain other metal cations have been removed. Said cations may have been replaced, for instance with Na (sodium). In a broader sense, the term demineralized water may be understood to also include reverse osmosis permeate. The demineralized water or permeate may have an electrical conductivity of for example ≤30 μS/cm. Alternatively, the clean water may be de-ionized water with an electrical conductivity of about 0.2 to 20 μS/cm, or so-called ultra-pure water with an electrical conductivity of 0.055 μS/cm at most. The whole purpose of the clean water in the closed loop is that the fouling of the PCHEs and that scaling of calcium or magnesium carbonates in the PCHEs is prevented. The softened water, soft water, or demineralized water reduces or eliminates scale build-up in the PCHEs.
The primary cooling loops 512, 514, 516 may each be regarded as a Clean Closed Cooling water (CCW) loop. As an example, see
The closed water-cooling loops 512, 514, 516 may comprise pumps 520, 522, 526 for pumping water around the respective loop. The respective pumps can pump the water towards the PCHEs 502, 504, 506. Each loop may comprise an expansion vessel 530, 532, 536 for receiving the water output from the heat exchangers 502, 504, 506. Heat exchangers 540, 542, 546 receive the warmed water from the vessels 530, 532, 536 for cooling thereof. In a practical embodiment, the heat exchangers 540, 542, 546 are Plate and Frame Heat Exchangers.
The primary cooling loops 512, 514, 516 can in turn be cooled with respect to a second coolant of a secondary cooling system 550. The second coolant may be cycled in a loop, wherein the system 550 can be regarded as a secondary cooling loop 550. When cycled in a secondary cooling loop, the second coolant may comprise seawater or water from cooling towers. Alternatively, the second coolant may be air. In the latter case, the secondary heat exchangers 540, 542 include air coolers, and the secondary cooling system 550 is formed by said air coolers.
The secondary loop 550 may comprise a first header 552 for providing the second coolant to the respective heat exchangers 540, 542, 546 via associated conduits 554, 556, 558. Warmed second coolant from the heat exchangers 540, 542, 546 may be collected at a second header 560. From the second header 560, warm second coolant may be provided to a cooler, such as at least one cooling tower or spray tower 570. A first pump 572 can circulate the second coolant in the secondary cooling loop 550. A make-up system 580 may typically be provided to provide additional secondary coolant to top up lost coolant or to add fresh water 582 to control the composition of the coolant. The makeup system may comprise a second pump 584 to pump fresh water 582 from a well or other source to the loop 550, for instance to the cooling tower 570.
It is understood that the second coolant can be selected from a group consisting of water from a cooling tower system, sea water, air, or a combination thereof. That is, cooling tower 570 can be replaced or supplemented with sea water or air.
For the sake of simplicity,
It is understood that for the sake of simplicity,
Secondary cooling loop 550 comprises a suitable cooler to cool the second coolant against ambient temperature. For example, the cooler can be cooling tower 570 as depicted and described herein. While not shown, it is understood that cooling against an ambient temperature by the primary cooling loop 512, 514, 516 can be done without secondary cooling loop 550, such as by routing the first coolant through ACHEs that are located in the OSBL 594.
As provided, the embodiment depicted in
By enabling dissipation of thermal energy in OSBL 594 in certain embodiments, the present disclosure to allows for a design of compact ISBL modules that are not limited by the size of the ACHE banks. Also, when heat dissipation occurs in the OSBL, there is flexibility around the mechanism through which that dissipation is achieved, such as through sea water, cooling towers, or air, without impacting the designs or configurations of the ISBL units, thereby allowing for train designs or aspects of train designs to be replicated from facility to facility.
Minimization of installed spares and valves. Traditional practice includes installing spared equipment such as pumps and their associated piping, valves and instrumentation in the respective modules. In other words, conventional modules used to comprise spare second versions of selected pieces of equipment, ready to be connected and used when a first version of said equipment failed. In the concept of the present disclosure, (some or all) equipment spares have been warehoused instead of installing them. These pieces of equipment are designed as ‘Plug and Play’ for easy removal and re-installation during a period of maintenance, also referred to as turnaround. Also, installation of bypass valves has been rationalized to significantly reduce the number of valves in a process unit. This approach enables the compactness of each module in the system 200 and further reduces the module weight for each respective module. For specifics and details, reference is made to, for instance, the disclosure of WO2019110770.
In the system of the disclosure, arrangement of equipment has been optimized. Optimizing the arrangement of equipment in the process modules 210-240 herein implies, for instance, that distance and piping requirement between respective pieces of equipment has been minimized. This in turn reduces the piping weight and module weight for each module 210 to 240. Reference is made to
Optionally, an additional and significant weight reduction for a respective module can be achieved by applying, for instance:
The following examples are provided to facilitate a better understanding of the leap forward provided by the system according to the present disclosure. In no way should these examples be construed to limit, or define, the scope of the invention.
Herein,
In an exemplary embodiment, system 200 compares favorably with respect to state-of-the-art modular facilities. Exemplary parameters are indicated in the table below.
With respect to the information included in the table above: System 200 with electric drivers for the compressors produces somewhat more per year due to higher availability and because electric drives power output is less dependent on the ambient temperature compared to gas turbine drives. The greenhouse gas (GHG) generation excludes GHG production of power generation. Overall, despite the smaller modules, a facility comprising a number of systems 200 according to the disclosure still requires fewer modules overall, with each process unit in one module, and fewer site hook-ups. Due to four smaller modular trains, the facility comprising four systems 200 includes more pieces of equipment in total, but each piece of equipment is smaller and lighter. And lighter modules reduce transportation costs. Also, heavier modules take longer to fabricate. The total number of fabrication yard hours to construct the modules reduces with almost 20%. The remaining expensive construction hours at the production site reduce with about 26%. The reduction in number of hours to construct both in the yard and on site is due to, for instance, the lower weight for each module weights and fewer site hookups, representing a significant cost saving.
As indicated in the table above, the number of pieces of equipment for all liquefaction trains combined increases with respect to a reference system. Also, the costs of certain individual pieces of equipment may be more expensive. For instance, Printed Circuit Heat Exchangers are more expensive than traditional Shell and Tube heat exchangers. However, equipment costs are only about 10% of the total installed costs. Thus, even though the costs to buy heat exchangers increases (for instance due to application of PCHEs), that contribution to the total installed costs is relatively low, substantially negligible. Consequently, the total procurement costs, i.e. the costs to obtain equipment, piping and bulk material (such as valves, etc.) is approximately the same for the system of the present disclosure and several reference projects as referred to herein. The total procurement costs represent approximately 20% of the total installed costs of a modular built LNG project. However, the total installed costs of the liquefaction systems according to the present disclosure is about 15 to 20% lower than the total costs to construct a conventional facility including relatively large modular LNG trains. Installed costs herein refer to capital expenditure to build the facility, including all liquefaction trains.
As graphically shown in
Another graphical representation of the significant reduction in footprint is provided in
As indicated before, see for instance
As exemplified in
The system of the present disclosure provides significant cost savings, as it deals with substantially all aspects linked to capital expenditure of modular built facilities. For off-shore LNG plants and offshore gas production systems, modular built used to be the norm, as offshore used to have a strong focus on available plot space and weight reduction. For instance, water cooling has been used for cooling in offshore LNG production. The system of the present disclosure recognizes that despite abundant plot space and availability of air for cooling, for onshore modular LNG facilities implementing water cooling in combination with relatively light and small equipment, such as printed circuit heat exchangers, provides significant cost savings. The system and method of the current disclosure combine features and layout, and modular construction, to achieve optimal benefit and reduction of capital expenditure above and beyond state-of-the-art modular construction for onshore facilities.
The design of the system 200 of the present disclosure is agnostic for compressors drive. The driver of the precool compressor 14 and main compressor 22 may be for instance a gas turbine or an electric motor. The site layout and arrangement of modules remains substantially the same.
Summarizing the above, over the last 10-15 years, the LNG industry has seen a shift from traditional stick-built LNG export projects towards modular-built projects. The main driver behind this trend is to move construction work offsite to a fabrication yard where the modular process units are built in a more controlled environment benefiting from higher productivity, lower labor rates, better quality, fewer safety incidents and—as a result—more competitive, repeatable and predictable cost and schedule outcomes. If not applied as a design philosophy from the start, modular construction may however be disadvantaged by complex and expensive logistics, less efficient operations and maintenance and underutilization of local content opportunities.
Applicant's Modular LNG concept as disclosed herein combines and integrates various technologies, thus addressing not just one or two, but substantially all levers impacting the capital expenditure to fabricate and build a facility comprising modular built LNG trains. As a result, the facility of the disclosure allows to significantly reduce the costs of a facility including modular built LNG trains for a comparable total capacity. The facility according to the disclosure can have a comparable or better efficiency than conventional facilities, with best in class GHG emissions.
This is achieved by:
Comparison with other Modular LNG built trains indicate a 40 to 50% reduction in equipment weight, module weight and plot requirement (normalized per MTPA of installed capacity) and approximately 20% reduction in site construction hours as well as fabrication yard hours. Combined, this reduces the costs of the modular built LNG trains according to embodiments described herein with 20% or more with respect to conventional liquefaction systems, including modular built systems. The facility of the disclosure enables significant additional future savings at project portfolio level.
The present disclosure is not limited to the embodiments as described above and the appended claims. Many modifications are conceivable within the scope of the appended claims. Features of respective embodiments may be combined.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20203750.3 | Oct 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/078096 | 10/12/2021 | WO |
