Membrane-Cryogenic Methane Liquefaction With CO2 Slurry Separation
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Solution Overview
Problem
Existing systems for liquefying hydrocarbon-containing gases, particularly those with high methane content, face challenges such as infrastructure requirements, high electrical power consumption, and inability to meet tight gas specifications, necessitating a more flexible and efficient processing method.
Innovation Solution
The integration of membrane gas separation and cryogenic 3-phase separation processes, where flash gas from the cryogenic separator is used as a sweep gas in membrane modules, allowing for efficient pre-treatment and liquefaction of gases with high methane content, reducing carbon dioxide and water content, and enabling direct supply to a standard gas liquefier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large industrial scale liquefaction system is used, then the liquefaction capacity is improved, but the infrastructure requirements and device complexity increase
Solution Approach 1:
The system divides the gas treatment process into distinct functional modules: membrane separation units for CO2 removal, cryogenic cooling section for liquefaction, and decanting device for phase separation. This modular segmentation allows the system to achieve industrial-scale productivity while reducing overall device complexity through standardized, interchangeable components.
Solution Approach 2:
The decanting device performs multiple functions: it acts as a pressure reducing device, a separator for removing solid CO2 and water ice, and a storage container for liquefied methane. This multi-functionality reduces the number of separate infrastructure components needed, thereby reducing device complexity while maintaining high liquefaction capacity.
2Manufacturing precision
If traditional gas treatment systems are used, then the gas purification is improved, but the electrical power consumption increases
Solution Approach 1:
The membrane separation process operates passively based on partial pressure gradients, requiring minimal external energy input. The cryogenic cooling section utilizes the Joule-Thomson effect where gas expansion through the pressure reducing device self-cools the methane, reducing the need for external refrigeration power. This self-service approach maintains high gas purification while minimizing electrical power consumption.
Solution Approach 2:
The system exploits phase transitions of CO2 and water at cryogenic temperatures to automatically separate these contaminants as solid particles in the decanting device. This phase-based separation mechanism provides high purification efficiency without requiring additional energy-intensive separation equipment, thereby reducing overall electrical power consumption.
3Productivity
If conventional liquefaction processes are used, then the methane liquefaction is improved, but the ability to meet tight gas specifications deteriorates
Solution Approach 1:
The membrane separation units are positioned upstream of the cryogenic cooling section to remove CO2 and water vapor before liquefaction. This preliminary removal of contaminants prevents freeze-up in the cryogenic section and ensures that the gas entering the liquefier meets tight specifications, thereby maintaining high methane liquefaction productivity while achieving required purity levels.
Solution Approach 2:
The decanting device serves as an intermediary between the pressure reducing device and the final product outlet, providing a controlled environment where solid CO2 and water ice can settle and be removed. This intermediary separation stage ensures that only high-purity liquefied methane exits the system, meeting tight gas specifications while maintaining efficient liquefaction throughput.
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 simplifies implementation, enhances energy efficiency, and produces liquefied gas with high purity, particularly methane, while being scalable and robust for various hydrocarbon sources like biogas, reducing infrastructure needs and operational complexity.
Implementation Method 1
a pre-treatment device comprising a membrane separator for separating CO2 and water from said incoming fluid
Implementation Method 2
a liquefying device comprising a liquefying device inlet in fluid communication with said pre-treatment device outlet, said liquefier comprising a cryogenic cooler for cooling and condensing said fluid
Implementation Method 3
a decanting device comprising a pressure reducing device having a pressure reducing device inlet in fluid communication with said liquefying device outlet and having a pressure reducing device outlet for providing said fluid at a pressure of 2-10 bar
Implementation Method 4
said decanting device further comprising a slurry-residue outlet for providing a slurry flow comprising solid CO2 and water ice
Data Source
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AI summary
The invention provides a system for liquefying an incoming gaseous fluid comprising at least 50% by volume methane, said system provided for providing an outgoing liquefied fluid comprising a methane content of at least 58% by volume. The invention further provides a method for liquefying a gaseous fluid, said method comprising: - providing an incoming gaseous fluid comprising at least 50% by volume methane; - increasing a pressure of said incoming gaseous fluid to between 10 and 50 bar; - pre-treating said gaseous fluid with increased pressure, said pre-treatment comprising filtering said gaseous fluid using membrane filtering to a retentate with a pressure of between 10 and 50 bar, a temperature of between 0°C and 50°C, a carbon dioxide content below 2 % by volume, a water content below 10 ppm and a methane content of at least 85% by volume; - liquefying said pre-treated fluid, said liquefying comprising cryogenic cooling said fluid to a temperature between -100°C and -140°C a pressure of between 10 and 50 bar and a methane content of at least 85% by volume; - flashing said liquefied fluid into a container, retrieving liquid fluid from said container at a first container level at a pressure of between 1 and 10 bar, a temperature of between -120°C and -160°C and a methane concentration of at least 85% by volume into a storage device and retrieving a slurry flow comprising solid C02 and water ice at a second container level below said first container level.