Single Methane Expander LNG Process to Reduce System Complexity
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Solution Overview
Problem
Current liquefaction systems for natural gas are complex and costly, requiring multiple components and refrigerants, which increases operational complexity and capital costs, especially in small-scale LNG facilities.
Innovation Solution
The process circulates a fluid derived from the incoming natural gas at an intermediate pressure to provide refrigeration, using a single methane expander to liquefy the feedstock, reducing the expansion ratio and eliminating the need for additional refrigerants, thus simplifying the system and lowering costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple refrigerants and components are used in conventional liquefaction systems, then the liquefaction capability is sufficient, but the device complexity and capital costs increase significantly
Solution Approach 1:
The patent extracts and eliminates the need for multiple refrigerants from the conventional liquefaction system. By using only natural gas itself as the refrigerant and removing external refrigerant loops, the system achieves simplification while maintaining liquefaction capability through the expander-driven refrigeration cycle.
Solution Approach 2:
The patent makes the natural gas feedstock serve multiple functions: it is both the material to be liquefied and the refrigerant used to achieve liquefaction. The expander-driven process allows the same gas to provide cooling duty while being processed, eliminating the need for separate refrigerant systems.
2Device complexity
If a single methane expander is used with intermediate pressure circulation, then the device complexity and costs are reduced, but the expansion ratio requirements become more critical
Solution Approach 1:
The patent introduces an intermediate pressure circulation as a mediator between the high-pressure feedstock and low-pressure storage requirements. This intermediate pressure loop allows the single expander to operate at optimal conditions while achieving the necessary overall pressure reduction through the circulation mechanism.
Solution Approach 2:
The system employs dynamic pressure management where the intermediate pressure is adjusted and circulated to optimize the expander's operation. The flexible pressure control allows the single expander to adapt to varying feed conditions and maintain efficient refrigeration duty.
3Ease of operation
If conventional refrigeration processes are used, then the liquefaction temperature is achieved, but the operational complexity and refrigerant handling requirements increase
Solution Approach 1:
The system uses self-service refrigeration where the natural gas feedstock itself provides the refrigeration duty through the expander process. The gas cools itself and other streams without requiring external refrigerants or complex refrigeration plants, simplifying operation while achieving the required liquefaction temperature.
Solution Approach 2:
The patent replaces complex mechanical refrigeration systems with a thermodynamic expander process. Instead of using motors, compressors, and heat exchangers typical of mechanical refrigeration, the system uses the inherent thermodynamic expansion of natural gas to provide cooling, reducing operational 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
This approach reduces capital and operational complexity, achieving efficient liquefaction with a single methane expander, lowering costs and eliminating the need for refrigerants, while maintaining high methane concentration in the LNG product.
Implementation Method 1
The embodiments according to the invention are configured for an 'expander' process that circulates fluid derived from the incoming natural gas to effectuate cooling at the heat exchanger
Implementation Method 2
These processes can be configured to provide cooling, typically at a heat exchanger, to closely match the cooling curve for natural gas
Implementation Method 3
The process according to the invention is configured to circulate the 'derived' fluid at an intermediate pressure that is between the pressure of the incoming hydrocarbon stream and the pressure of a stream
Data Source
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AI summary
A liquefaction system that is configured to use a single methane expander to provide primary refrigeration duty. The liquefaction system can include a first or main heat exchanger and a fluid circuit coupled with the heat exchanger, the fluid circuit configured to circulate a process stream derived from an incoming feedstock of natural gas. The fluid circuit can comprise a compression circuit, methane expander coupled with the compression circuit and the main heat exchanger, a sub-cooling unit coupled with the methane expander, the sub-cooling unit configured to form a liquid natural gas (LNG) product from the process stream, and a first throttling device interposed between the main heat exchanger and the sub-cooling unit. The first throttling device can be configured to expand the process stream to a process pressure that corresponds with the suction pressure internal to the compression circuit.