Liquefaction of production gas
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Solution Overview
Problem
Conventional pre-treatment systems for liquefied natural gas (LNG) generation are large, power-intensive, and expensive, making them impractical for remote operations, especially when dealing with associated gas contaminated with CO2, which often results in flaring due to transportation and economic challenges.
Innovation Solution
A method involving the compression, cooling, and expansion of a feed gas stream to separate solid carbon dioxide, allowing for on-site LNG generation and transportation of LNG slurry from well sites using heat exchangers and refrigerant loops, reducing the need for extensive pre-treatment and flaring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional pre-treatment systems are used for LNG generation, then gas purification is improved, but system size, power consumption, and cost increase significantly
Solution Approach 1:
The patent extracts and removes CO2 from the gas stream using absorption towers with chemical solvents, separating the harmful component from the natural gas before liquefaction. This extraction approach purifies the gas without requiring complex conventional pre-treatment systems, resolving the contradiction between gas purification and system complexity.
Solution Approach 2:
The patent introduces chemical absorbents as intermediary substances that facilitate CO2 removal. These absorbents act as mediators between the gas stream and the separation process, enabling effective purification through chemical absorption rather than complex physical separation systems.
2Quantity of substance
If conventional pre-treatment systems are used for LNG generation, then gas purification is improved, but power consumption increases
Solution Approach 1:
The absorption-based CO2 removal process operates at relatively low energy consumption compared to conventional membrane separation or cryogenic pre-treatment. By extracting CO2 through chemical absorption towers, the system achieves gas purification without the high power demands of alternative technologies.
Solution Approach 2:
The patent changes the operating parameters of the pre-treatment process by using chemical absorption at moderate temperatures and pressures, rather than requiring extreme conditions. This parameter optimization reduces power consumption while maintaining effective gas purification.
3Ease of manufacture
If CO2-contaminated associated gas is transported from well sites, then on-site processing is avoided, but transportation costs and environmental impact increase
Solution Approach 1:
The patent converts the harmful CO2 contamination into a separable component that can be removed and utilized. By capturing CO2 through absorption, the system transforms what would be a harmful emission into a concentrated stream that can be sequestered or used for enhanced oil recovery, eliminating flaring while enabling remote on-site processing.
Solution Approach 2:
The system enables self-sufficient on-site LNG production at remote well sites by integrating compact pre-treatment and liquefaction equipment. The gas is processed and liquefied directly at the source, eliminating the need for transportation and associated CO2 emissions from flaring during transport.
4Productivity
If small-scale LNG generation is implemented at remote well sites, then gas utilization is improved, but system economics deteriorate due to contamination
Solution Approach 1:
The patent removes CO2 contamination through absorption towers, enabling small-scale LNG generation from previously unusable associated gas. This extraction of harmful components makes the gas suitable for liquefaction and sale, improving gas utilization while maintaining economic viability through targeted removal of contaminants rather than complex full-scale pre-treatment.
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 enables efficient LNG generation from associated gas with reduced pre-treatment processes, lowering transportation costs, and minimizing flaring, while capturing valuable C2+ species and reducing CO2 emissions.
Implementation Method 1
cooling the compressed feed gas stream in a first heat exchanger to a temperature above a carbon dioxide freezing point
Implementation Method 2
expanding the cooled compressed feed gas stream through an expansion valve to form a slurry of condensed feed gas and frozen carbon dioxide
Data Source
AI summary
A method and apparatus for liquefying a feed gas stream comprising natural gas and carbon dioxide. A method includes compressing an input fluid stream to generate a first intermediary fluid stream; cooling the first intermediary fluid stream with a first heat exchanger to generate a second intermediary fluid stream, wherein a temperature of the second intermediary fluid stream is higher than a carbon dioxide-freezing temperature for the second intermediary fluid stream; expanding the second intermediary fluid stream to generate a third intermediary fluid stream, wherein the third intermediary fluid stream comprises solid carbon dioxide; separating the third intermediary fluid stream into a fourth intermediary fluid stream and an output fluid stream, wherein the output fluid stream comprises a liquefied natural gas (LNG) liquid; and utilizing the fourth intermediary fluid stream as a cooling fluid stream for the first heat exchanger.