Open loop liquefaction process with NGL recovery
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Solution Overview
Problem
Traditional methods for removing natural gas liquids (NGLs) and heavy hydrocarbons from natural gas feed streams require additional equipment for feed compression and refrigerant storage, increasing capital costs and operational complexity.
Innovation Solution
An integrated system that combines a front-end natural gas liquids unit with a natural gas liquefaction unit using an open-loop refrigeration cycle, eliminating the need for feed compression equipment and refrigerant storage, while achieving efficient NGL recovery and aromatics extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a stand-alone front-end NGL extraction unit is used to remove natural gas liquids, then NGL recovery is achieved, but additional feed compression equipment is required increasing capital costs and device complexity
Solution Approach 1:
The patent combines the NGL extraction unit and the natural gas liquefaction unit into a single integrated system. The NGL extraction column and liquefaction heat exchangers share common equipment, particularly the refrigeration system. The refrigerant from the liquefaction unit serves dual purposes: cooling the natural gas feed stream for liquefaction and providing refrigeration for the NGL extraction column, thereby eliminating the need for separate feed compression equipment and reducing overall device complexity.
Solution Approach 2:
The refrigeration system in the integrated design performs multiple functions simultaneously. It provides cooling for the natural gas feed stream in the liquefaction process and also supplies refrigeration duty to the NGL extraction column. This multi-functionality eliminates the need for dedicated feed compression equipment and reduces capital costs while maintaining effective NGL recovery.
2Quantity of substance
If traditional NGL extraction at low to medium pressure is used, then NGL separation is achieved, but additional equipment is required to increase feed pressure for efficient liquefaction
Solution Approach 1:
The integrated system merges the NGL extraction pressure increase function with the liquefaction process. The natural gas feed stream is pressurized to a level suitable for both NGL extraction and subsequent liquefaction in a single compression step, eliminating the need for separate pressure increase equipment and reducing capital costs.
Solution Approach 2:
The compression equipment in the integrated design serves dual purposes: it pressurizes the natural gas feed stream for efficient NGL extraction and simultaneously provides the pressure required for the liquefaction process. This multi-functionality reduces the number of compression stages and equipment requirements, thereby lowering capital costs.
3Device complexity
If an open-loop refrigeration cycle is used in the liquefaction unit, then equipment and piping for refrigerant storage and injection is eliminated, but the system requires integration with the NGL unit
Solution Approach 1:
The patent integrates the open-loop refrigeration cycle with the NGL extraction unit, combining two previously separate processes into one unified system. The refrigerant from the liquefaction unit is directly used to provide refrigeration for the NGL extraction column, eliminating the need for separate refrigerant storage and injection equipment while maintaining process effectiveness.
4Device complexity
If feed compression equipment is eliminated through integration, then capital costs are reduced, but the system requires an open-loop refrigeration cycle configuration
Solution Approach 1:
The open-loop refrigeration cycle in the integrated design performs multiple functions: it cools the natural gas feed stream for liquefaction and simultaneously provides refrigeration duty to the NGL extraction column. This multi-functionality eliminates the need for separate feed compression equipment and refrigeration systems, reducing capital costs while maintaining system flexibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces capital costs and operating complexity while maintaining high levels of NGL recovery and aromatics extraction, simplifying the process and improving efficiency.
Implementation Method 1
cooling a natural gas feed stream via indirect heat exchange with a combined natural gas vapor, first expanded refrigerant and second expanded refrigerant stream to form a compressed refrigerant
Implementation Method 2
compressing the resulting warmed streams, and combining said streams to form a compressed refrigerant
Implementation Method 3
expanding the first cold refrigerant stream and separating said stream into vapor and liquid phases to form a first liquefied natural gas stream from the liquid phase and the first expanded refrigerant stream from the vapor phase
Implementation Method 4
introducing said stream into a distillation column having one or more separation sections, the natural gas feed stream being introduced into the distillation column below at least one of said separation sections
Data Source
Figure 1
Figure 1A
Figure 1B
AI summary
Described herein are methods and systems for removing natural gas liquids from a natural gas feed stream and for liquefying the natural gas feed stream so as to produce a liquefied natural gas (LNG) stream and a natural gas liquids (NGL) stream.