Single Methane Expander LNG System to Reduce Refrigerant Complexity
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Solution Overview
Problem
Current liquefaction systems for natural gas are complex and costly, often requiring multiple refrigerants and expanders, which increases operational and capital expenses, especially in small-scale LNG facilities.
Innovation Solution
The system 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 expansion ratio and eliminating the need for additional refrigerants, thus simplifying the process and lowering costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple refrigerants and expanders are used in liquefaction systems, then the liquefaction capability is improved, but the device complexity and capital costs increase
Solution Approach 1:
The patent extracts and eliminates the need for multiple refrigerants from the system. By using a single methane expander to provide refrigeration duty, the system removes the complexity associated with multiple refrigerant handling, storage, and circulation systems while maintaining effective liquefaction capability
Solution Approach 2:
The patent combines the refrigeration duty provision function into a single methane expander system. Instead of having separate refrigerant circulation systems, the expansion of methane gas itself provides the refrigeration needed for liquefaction, merging multiple functions into one integrated system
2Productivity
If multiple refrigerants and expanders are used in liquefaction systems, then the liquefaction capability is improved, but the operational costs increase
Solution Approach 1:
The system uses methane gas that is already present in the natural gas feedstock to provide refrigeration duty through expansion. This self-service approach eliminates the need to import or generate separate refrigerants, reducing operational costs associated with refrigerant procurement, handling, and maintenance
3Device complexity
If a single methane expander is used at intermediate pressure, then the device complexity is reduced, but the refrigeration duty may be insufficient
Solution Approach 1:
The patent optimizes the intermediate pressure parameter of the methane expander to achieve the right balance between system simplicity and refrigeration duty. By carefully selecting and controlling the pressure ratio across the expander, sufficient refrigeration is generated from a single expander without requiring complex multi-expander configurations
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 lower costs and eliminating the need for refrigerant handling and storage, while maintaining high methane concentration in the LNG product.
Implementation Method 1
fluid derived from the incoming natural gas to effectuate cooling at the heat exchanger
Implementation Method 2
circulate the 'derived' fluid at an intermediate pressure that is between the pressure of the incoming hydrocarbon stream and the pressure of a stream
Implementation Method 3
provide cooling, typically at a heat exchanger, to closely match the cooling curve for natural gas
Implementation Method 4
form a liquefied natural gas (LNG) product or stream
Data Source
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.