Patent Application
20230235954
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The disclosure generally relates to hydrocarbon production facilities. More specifically, the disclosure relates to modular and compact production facilities of hydrocarbons such as liquefied natural gas.
A large portion of natural gas traded internationally is in the form of Liquefied Natural Gas (“LNG”). Liquefaction plants/terminals constitute a key link in natural gas value chain, producing LNG from natural gas via a cryogenic process, store the product in large storage tanks, and then load the LNG into LNG carriers bound for export destinations.
Liquefaction plants are traditionally arranged in trains. A train is a collection of process systems necessary to perform complete function of processing gaseous feed gas and converting it into liquid LNG product. A liquefaction train can vary in size from small-scale to mid-scale to large-scale with distinct selections of technologies and equipment. The capacity of a mid-scale train is generally in the range of 1 to 3.5 million tons per annum (“MTPA”) LNG production. An onshore base load liquefaction plant often consists of multiple identical trains, sometime constructed at different times. The trains are served by other common facilities located outside battery limits (OSBL), including utilities, LNG storage, LNG loading, marine systems, and so forth.
In the past, onshore LNG plants are mostly “stick built”, which is built on site with individual components as a traditional method of construction. The construction process takes thousands of onsite construction workers at a time and could last years to finish. Stick built LNG plants usually occupy massive real estate.
During recent years, modular construction has been increasingly applied in LNG project execution, which in many cases shortens project schedule and reduces risks, at the same time saving cost. However, the extent of modularization and its specific implementation varies a great deal from project to project. The following observations are made in literature of modular LNG train design.
First, modularization remains a construction method rather than a design philosophy. Consequently, a train has the same or similar configuration and layout as a conventional stick built one, only to be sliced up into smaller sections when it comes to construction execution. One consequence is a very large train footprint due to most process equipment being located on the base level, even though the equipment may have been included in different modules.
Second, only parts of the train are modularized, leaving the remaining sections still to be stick built. This is prevalent in most of the current “modular” trains. Non-modular sections of the train often involve components that are challenging to be modularized, for example tall and heavy columns, liquefier, large rotating equipment, pipe rack, electrical/instrumental equipment, and others. The U.S. Pat. No. 10,539,361, for instance, has much equipment located in unframed sections or even outside modules. As a result, the train footprint remains significant and a substantial amount of field work is still required.
Third, a large number of modules is often required to construct a complete LNG train, which increases exponentially with train size. The number and size of modules rely on many practical constraints in module fabrication, marine shipping, road transportation, and other factors. A train, especially a large-scale one, is sometimes divided into dozens of modules, which leads to a large number of interfaces/golden welds to be connected in the field. It also adds complexity and uncertainties to construction execution, as all these modules could be built and shipped from different yards around the globe, that need to be managed and coordinated. From this perspective, less number of modules are desirable for which mid-scale trains offer better prospects.
Given these shortcomings in prior art, alternate and better designs are much needed to realize full benefits from LNG train modularization.
The present disclosure provides a system and method of efficiently designing a compact and modularized midscale liquefied natural gas (“LNG”) production train. The train includes Natural Gas Pretreatment and Natural Gas Liquefaction sections designed in a unique way that reduces footprint, capital and operating cost, and overall project schedule. The modularized train can contain substantially complete process systems required for natural gas pretreatment (including inlet gas reception, mercury removal, acid gas removal, dehydration, heavies removal) and liquefaction (including pre-cooling, condensing, subcooling, and refrigerant circuits). Necessary hardware including mechanical and electrical equipment, piping and instrumentation are all included. The train is configured into a framed compact multi-level structure with air coolers on the top level and process equipment underneath, which results in significant reduction in footprint compared to conventional stick-built design and significant reduction in footprint compared to conventional modularized design. In at least one illustrative comparison, the inventive modularized midscale liquefied natural gas production train results in about 30% reduction in footprint compared to conventional stick-built design and about 10% reduction in footprint compared to conventional modularized design.
The inefficiencies of prior art are removed in the new method described in this invention. The efficiency of compactness is further improved by arranging process equipment/ systems in a strategic and unique way in at least one or more of the following:
This strategic placement of the equipment also leads to low hydrocarbon inventory of LNG and other cryogenic fluids which leads further to compactness without compromising the process safety. Furthermore, the strategic design of module(s) provides flexibility to add options with no impact to overall module design and equipment layout.
The disclosure provides a modularized liquefied natural gas production train, comprising: a framed multi-level structure comprising natural gas liquefaction process systems required for natural gas pretreatment, liquefaction, and refrigerant compression and related hardware including mechanical and electrical equipment, piping and instrumentation; wherein air coolers are installed on a top level of the structure with other process equipment located on multiple levels underneath the air coolers; wherein the structure has a central pipe rack the runs a longitudinal length of the structure with equipment located on both sides of the central pipe rack; and wherein one more refrigerant compressors and related power drivers are located at an end of the structure.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
The Figures described above and the written description of specific structures and functions below are not presented to limit the scope of what Applicant has invented or the scope of the appended claims. Rather, the Figures and written description are provided to teach any person skilled in the art how to make and use the inventions for which patent protection is sought. Those skilled in the art will appreciate that not all features of a commercial embodiment of the inventions are described or shown for the sake of clarity and understanding. Persons of skill in this art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present disclosure will require numerous implementation-specific decisions to achieve the developer's ultimate goal for the commercial embodiment. Such implementation-specific decisions may include, and likely are not limited to, compliance with system-related, business-related, government-related, and other constraints, which may vary by specific implementation, location, or with time. While a developer's efforts might be complex and time-consuming in an absolute sense, such efforts would be, nevertheless, a routine undertaking for those of ordinary skill in this art having benefit of this disclosure. It must be understood that the inventions disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. The use of a singular term, such as, but not limited to, “a,” is not intended as limiting of the number of items. Further, the various methods and embodiments of the system can be included in combination with each other to produce variations of the disclosed methods and embodiments. Discussion of singular elements can include plural elements and vice-versa. References to at least one item may include one or more items. Also, various aspects of the embodiments could be used in conjunction with each other to accomplish the understood goals of the disclosure. Unless the context requires otherwise, the term “comprise” or variations such as “comprises” or “comprising,” should be understood to imply the inclusion of at least the stated element or step or group of elements or steps or equivalents thereof, and not the exclusion of a greater numerical quantity or any other element or step or group of elements or steps or equivalents thereof. The terms “top”, “up”, “upward”, “bottom”, “down”, “downwardly”, and like directional terms are used to indicate the direction relative to the figures and their illustrated orientation and are not absolute relative to a fixed datum such as the earth in commercial use. The term “inner,” “inward,” “internal” or like terms refers to a direction facing toward a center portion of an assembly, component or system, such as longitudinal centerline of the assembly, component or system, and the term “outer,” “outward,” “external” or like terms refers to a direction facing away from the center portion of an assembly, component, or system. The term “coupled,” “coupling,” “coupler,” and like terms are used broadly herein and may include any method or device for securing, binding, bonding, fastening, attaching, joining, inserting therein, forming thereon or therein, communicating, or otherwise associating, for example, mechanically, magnetically, electrically, chemically, operably, directly or indirectly with intermediate elements, one or more pieces of members together and may further include without limitation integrally forming one functional member with another in a unitary fashion. The coupling may occur in any direction, including rotationally. The order of steps can occur in a variety of sequences unless otherwise specifically limited. The various steps described herein can be combined with other steps, interlineated with the stated steps, and/or split into multiple steps. Similarly, elements have been described functionally and can be embodied as separate components or can be combined into components having multiple functions. Some elements are nominated by a device name for simplicity and would be understood to include a system of related components that are known to those with ordinary skill in the art and may not be specifically described. Various examples are provided in the description and figures that perform various functions and are non-limiting in shape, size, description, but serve as illustrative structures that can be varied as would be known to one with ordinary skill in the art given the teachings contained herein. As such, the use of the term “exemplary” is the adjective form of the noun “example” and likewise refers to an illustrative structure, and not necessarily a preferred embodiment. Element numbers with suffix letters, such as “A”, “B”, and so forth, are to designate different elements within a group of like elements having a similar structure or function, and corresponding element numbers without the suffix letters are to generally refer to one or more of the like elements. Any element numbers in the claims that correspond to elements disclosed in the application are illustrative and not exclusive, as several embodiments may be disclosed that use various element numbers for like elements.
The present disclosure provides a system and method of efficiently designing a compact and modularized midscale liquefied natural gas production train. The train includes Natural Gas Pretreatment and Natural Gas Liquefaction sections designed in a unique way that reduces footprint, capital and operating cost, and overall project schedule. The train is configured into a framed compact multi-level structure with air coolers on the top level and process equipment underneath, which results in significant reduction in footprint compared to conventional stick-built design and significant reduction in footprint compared to conventional modularized design.
Contrasting to prior art, the present invention can configure an entire LNG train 10 into a fully framed multi-level structure. Such a structure not only provides space to contain all components within the train, but also is supported adequately for marine and road transportation either as one or multiple modules. The first level 12 (also referred to as a bottom deck herein) is a structural base and is elevated from the ground or other supporting surface to allow roll-on roll-off transportation on ship and shore with self-propelled module transporters (“SPMT”) 14. Air coolers 16 are installed on a top level 18 of the structure and other process equipment are located in levels underneath the top level with the air coolers. Tubes coupled with the air coolers can include at least portions of high flux tubes. The air coolers can be installed so that air coolers that collectively form a majority heat load of the train and air flow are installed on one portion of the top level to reduce hot air recirculation and reduce a size of at least a portion of the air coolers. Further, an air cooler located in proximity to a gas turbine can include a high air flow fan to reduce hot air recirculation to an intake of the gas turbine.
Compression equipment, such as a booster compressor 76, can be located on one side of the central corridor 26 in a pre-treatment section (such as pretreatment module 66) and process towers 68 can be located on an opposite side of the pipe rack 24 of the central corridor 26. At least some of the compression equipment can be located at an edge, such as a corner, of the train for easy replacement and maintenance access. Also, large compressors requiring large motor drivers and variable frequency drives are generally located on the edges of the modules. This location allows high tension cables to be outside the train and not in close proximity of other ISBL equipment, which enhances the safety of the plant.
Multiple levels 20 allow vertical offset among equipment and enables more compact layout. As a result, the train footprint is significantly smaller compared with other designs with the same capacity as described in
The train 10 structure has a built-in central pipe rack 24, shown particularly in
A pre-cooling heat exchanger 82 can be located on one side of the central corridor 26 in a liquefaction section (such as liquefaction module 54) and a liquefier 50 can be located on an opposite side of the central corridor. In this way, superior weight distribution and shape symmetry of the module is achieved.
Local electrical rooms and/or substations 84 can be located at outside edges 86 of the train and distal from liquefied natural gas rundown lines and a cryogenic area, described above, to have clean air intake access. Also, instrument junction boxes 88 can be located along the central corridor 26, distal from liquefied natural gas rundown lines and a cryogenic area.
With a fully framed train 10 structure of the present invention, a large open top level 18 is formed and is made available for air cooler 16 installation. There is a lot more space in width (i.e. latitudinal) direction compared to only the pipe rack as in prior art. With the geometry of air coolers carefully selected, at least two air cooler banks 38A and 38B are arranged side-by-side fully occupying the top level width. The air coolers can be installed on the top level independent of any cantilever extensions extending laterally from the train. As a result, no additional footprint structure is required for air coolers.
In the present invention, refrigerant compressor(s) 40 and refrigerant compressor power driver(s) 42 are strategically located at an end 44 of the elongated train 10 structure, such as the end of a compression module 46, allowing easy access for maintenance. In addition, the compressor(s) and driver(s) can be aligned such that their shafts are in parallel with the longitudinal length of the train, including parallel with the length of the pipe rack 24, described above. With being located at the end 44 of the train 10, the power driver 42 is interchangeable between gas turbine driver and electric motor driver. Such a location also provides flexibility to accommodate compressor design variability (such as barrel vs. horizontal split casing, single vs. multiple bodies, and so forth), causing little if any impact on overall train structure design and equipment layout.
One or two Liquefiers for LNG precooling, condensing, and subcooling may be required depending on liquefaction processes. The present invention differs in that the liquefier(s) 50 can be installed at a reserved location within the train 10 and supported by the train structure. This enclosed liquefier design shortens the inter-connecting piping between the liquefier 50 and connecting equipment, and hence reduces contained hydrocarbon liquid inventory such as LNG or refrigerant. It allows the train 10 structure to provide support for the liquefier and avoid a dedicated support structure often required to support this tall exchanger and its associated piping and valves. In the case of multi-train layout, the spacing between the two adjacent trains in parallel can be reduced without the liquefier(s) sticking out.
The liquefier 50 located at an end 52 of a liquefaction section 54, the LNG rundown line 56 can be routed outside of the structure boundary from the same end and away from the train resulting in minimum length of LNG rundown line 56 within the train 10 leading to minimum inventory of LNG within the train and thus enhanced safety. Due to short length of LNG run down line 56, vacuum insulated pipes 58 can be used. By using vacuum insulated pipes 58, LNG troughs are not needed for spill containment. The design helps achieve superior safety and cost effective pre-fabricated design.
While the modularized liquefied natural gas production train has been described above with some specificity, the train is not limited to such a configuration. For example, the number of levels and modules, height of the bottom deck above grade, location of various sections in modules, and other features can vary. In some cases when module transportation becomes a constraint, the train could be stick built with the same layout concept to achieve compactness and cost reduction. Other and further embodiments utilizing one or more aspects of the inventions described above can be devised without departing from the disclosed invention as defined in the claims. For example, some of the components could be arranged in different locations, and other variations that are limited only by the scope of the claims.
The invention has been described in the context of preferred and other embodiments, and not every embodiment of the invention has been described. Obvious modifications and alterations to the described embodiments are available to those of ordinary skill in the art. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the invention conceived of by the Applicant, but rather, in conformity with the patent laws, Applicant intends to protect fully all such modifications and improvements that come within the scope of the following claims.
