Single-Refrigerant LNG Cycle With Multi-Expander Pressure Staging
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Solution Overview
Problem
Current LNG production technologies face high energy demand, complexity, and safety concerns due to combustible refrigerants, particularly in offshore installations, which limits their efficiency and profitability.
Innovation Solution
A method and apparatus utilizing a single component refrigeration cycle with multiple expanders, controlled for mass flows, temperatures, and pressure levels, employing an inert gas like nitrogen to minimize heat exchanger losses and optimize efficiency across different stages of LNG production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multi component refrigerant technology is used in cascades arrangements, then energy efficiency is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the complex multi-component refrigerant system, replacing it with a single-component refrigerant (nitrogen or other inert gas). This extraction removes the need for complex cascade arrangements, gas make-up assemblies, and multiple refrigerant circulation systems while maintaining the essential refrigeration function through a simplified single-component approach.
Solution Approach 2:
The patent changes the fundamental parameter of refrigerant composition from multi-component to single-component. This parameter change fundamentally simplifies the system architecture, control mechanisms, and operational procedures while achieving comparable or improved energy efficiency through optimized single-component thermodynamic cycles.
2Power
If multi component refrigerant technology is used, then refrigeration capacity is improved, but control speed decreases and robustness is reduced
Solution Approach 1:
The patent removes the complex control systems required for multi-component refrigerant management, including gas make-up assemblies, composition monitoring systems, and cascade control mechanisms. The single-component system inherently provides more robust and faster control with simpler valve and flow management.
3Use of energy by moving object
If combustible refrigerants are used, then refrigeration efficiency is improved, but safety concerns increase especially in offshore installations
Solution Approach 1:
The patent explicitly adopts inert gases (nitrogen, argon, or other inert gases) as the refrigerant medium. This creates an inherently safe inert atmosphere throughout the system, eliminating combustion risks while maintaining refrigeration efficiency through the thermodynamic properties of the inert gas in optimized cycle arrangements.
4Device complexity
If all refrigerant flows are expanded down to the lowest pressure, then system simplicity is improved, but energy consumption increases
Solution Approach 1:
The patent segments the refrigeration process into multiple pressure levels with dedicated expanders for each level. Instead of a single expansion stage to the lowest pressure, the system uses high-pressure expanders that expand refrigerant to intermediate pressures, and low-pressure expanders that further expand to the lowest pressure, optimizing the work output at each stage and reducing total energy consumption.
Solution Approach 2:
The patent implements dynamic pressure level management where expanders operate at different pressure levels rather than a fixed single-pressure expansion. This dynamic approach allows the system to adapt expansion ratios and pressure levels to match the specific refrigeration load requirements, improving overall energy efficiency.
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 specific energy consumption, simplifies control, and enhances safety by using non-flammable refrigerants, resulting in a more compact, cost-effective, and environmentally friendly LNG production process adaptable to varying gas sources and compositions.
Implementation Method 1
the refrigerant is divided into at least two separate flows which are cooled and expanded in at least two separate expanders
Implementation Method 2
heat absorption includes phase change of refrigerant
Data Source
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AI summary
A method and system for producing liquefied and sub-cooled natural gas by means of a refrigeration assembly using a single phase gaseous refrigerant comprising: at least two expanders (1-3); a compressor assembly (5-7); a heat exchanger assembly (8) for heat absorption from natural gas; and a heat rejection assembly (10-12). The novel features according to the present invention are arranging the expanders (1-3) in expander loops; using only one and the same refrigerant in all loops; passing an expanded refrigerant flow from the respective expander into the heat exchanger assembly (8), each being at a mass flow and temperature level adapted to de-superheating, condensation or cooling of dense phase and/or sub-cooling of natural gas; and serving the refrigerant to the respective expander in a compressed flow by means of the compressor assembly having compressors or compressor stages enabling adapted inlet and outlet pressures for the respective expander.