Staged Compression for Simpler Mixed-Refrigerant LNG Cooling
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Solution Overview
Problem
Conventional thermodynamic processes for producing liquefied natural gas (LNG) are inefficient, costly, and complex, failing to meet demand due to the need for extensive equipment and refrigerants, which hinders the adoption of natural gas as a viable alternative fuel.
Innovation Solution
A simplified liquefaction system using a single mixed refrigerant, which is compressed and cooled in stages, separated, and reused to cool natural gas through a heat exchanger, reducing the number of compressors and equipment needed, thereby enhancing efficiency and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional thermodynamic processes are used to produce LNG, then the production can meet certain demand, but the system complexity and equipment requirements increase significantly
Solution Approach 1:
The refrigeration process is divided into multiple stages with different refrigerants (first refrigerant for initial cooling, second refrigerant for final cooling) operating in separate but coordinated systems. Each stage handles specific temperature ranges, allowing the system to achieve complex cooling objectives through simpler, specialized subsystems rather than one monolithic complex system
Solution Approach 2:
A heat exchanger serves as an intermediary component that couples the first and second refrigeration systems. The heat exchanger transfers thermal energy between the two refrigerant circuits, enabling coordination between stages without direct mechanical coupling, thus reducing overall system complexity while maintaining productivity
2Productivity
If conventional thermodynamic processes are used to produce LNG, then the production can meet certain demand, but the equipment requirements and costs increase
Solution Approach 1:
The system uses segmented refrigeration approaches with different refrigerants for different temperature stages. This segmentation allows each subsystem to be optimized independently for its specific temperature range, reducing the need for expensive, highly specialized equipment across the entire system while maintaining high productivity
Solution Approach 2:
The system changes refrigerant parameters (type, temperature, pressure) across different stages. By selecting appropriate refrigerants for specific temperature ranges and changing parameters optimally at each stage, the system achieves high LNG production efficiency without requiring expensive equipment modifications or operations
3Device complexity
If single mixed refrigerant is used in simplified liquefaction system, then the system complexity and equipment costs are reduced, but the energy consumption and production efficiency need improvement
Solution Approach 1:
The system employs periodic or cyclic refrigeration processes where refrigerants are continuously circulated through compression, condensation, expansion, and evaporation stages. This periodic action optimizes energy transfer efficiency at each stage, ensuring that the simplified system achieves acceptable energy consumption levels despite reduced complexity
Solution Approach 2:
The system utilizes phase transitions (gas to liquid, liquid to gas) of the single mixed refrigerant as the core mechanism for heat transfer and cooling. By carefully controlling phase change points and utilizing latent heat, the system maximizes cooling efficiency per unit of energy consumed, offsetting the trade-off for reduced system complexity
4Device complexity
If single mixed refrigerant is used in simplified liquefaction system, then the system complexity and equipment costs are reduced, but the production efficiency needs improvement
Solution Approach 1:
The cooling process is segmented into stages handled by the single mixed refrigerant at different temperatures and pressures. This segmentation allows the simplified system to achieve efficient stepwise cooling of natural gas, maintaining production efficiency without requiring complex multi-refrigerant systems
Solution Approach 2:
The single mixed refrigerant undergoes parameter changes (temperature, pressure, phase) optimized for each stage of the liquefaction process. By controlling these parameter changes efficiently, the simplified system achieves high production efficiency despite having fewer components and lower complexity
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
The system effectively produces LNG by reducing complexity and costs, improving energy consumption and production efficiency, making it more practical for meeting increased demand and promoting the use of natural gas as a cleaner fuel alternative.
Implementation Method 1
cooling the refrigerant in a heat exchanger with the natural gas to thereby produce the liquefied natural gas
Implementation Method 2
compressing a first portion of a single mixed refrigerant in a first compressor, and compressing a second portion of the single mixed refrigerant in the first compressor
Implementation Method 3
cooling the single mixed refrigerant in a first cooler to produce a first liquid phase and a gaseous phase
Implementation Method 4
separating the first liquid phase from the gaseous phase in a first liquid separator
Data Source
AI summary
A liquefaction system and method for producing liquefied natural gas (LNG) is provided. The liquefaction system may include a heat exchanger to cool natural gas to LNG, a first compressor to compress and combine first and second portions of a single mixed refrigerant from the heat exchanger, a first cooler to cool the single mixed refrigerant from the first compressor to a first liquid phase and a gaseous phase, and a first liquid separator to separate the first liquid phase from the gaseous phase. The liquefaction system may also include a second compressor to compress the gaseous phase, a second cooler to cool the compressed gaseous phase to a second liquid phase and the second portion of the single mixed refrigerant, a second liquid separator to separate the second liquid phase from the second portion of the single mixed refrigerant, and a pump to pressurize the first liquid phase.