LNG Ethane Extraction via Fractionation and Methane Recompression
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Solution Overview
Problem
Current methods for processing liquefied natural gas (LNG) are inefficient in separating natural gas liquids (NGL) from methane-rich gas streams, and there is a need for systems that can selectively divert LNG to vaporize both methane and ethane for enhanced processing.
Innovation Solution
The system involves passing LNG through a heat exchanger to vaporize and fractionate it, producing a methane-rich vapor stream and an NGL stream, which is then processed further to separate into liquid and gas phases, with the liquid stream being pressurized and delivered to a pipeline, and the gas stream being compressed for delivery or used as plant site fuel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional separation methods are used to separate methane from NGL, then methane can be recovered, but the separation efficiency is insufficient and ethane cannot be selectively vaporized
Solution Approach 1:
The system divides the LNG processing into distinct segments: a fractionation column separates methane-rich vapor from NGL liquid, while a parallel vaporization system selectively vaporizes ethane-plus components. This segmentation allows independent optimization of separation efficiency and selective vaporization capability.
Solution Approach 2:
The heat exchanger serves multiple functions: it pre-heats the LNG feed, condenses the methane-rich vapor from the fractionation column, and provides heating for the selective vaporization of ethane-plus components. This multi-functionality improves overall process efficiency while addressing both separation and selective vaporization requirements.
2Adaptability or versatility
If LNG is fully vaporized, then all components including ethane are converted to gas, but this prevents selective recovery of NGL and increases energy consumption
Solution Approach 1:
The system incorporates dynamic control capabilities that allow selective diversion of LNG to different processing paths based on market conditions and operational requirements. The fractionation column and vaporization system can be adjusted to optimize between NGL recovery and ethane vaporization modes, enabling adaptive energy management.
Solution Approach 2:
The system changes key operating parameters including temperature, pressure, and flow distribution to achieve selective vaporization. By controlling the temperature in the vaporization system and adjusting the diversion ratio of LNG to different paths, the system can selectively vaporize ethane-plus components while maintaining efficient methane separation, thereby reducing overall energy consumption compared to full vaporization.
3Quantity of substance
If NGL recovery is maximized, then ethane and heavier hydrocarbons are recovered as liquids, but this prevents delivery of high-pressure methane-rich gas to pipeline
Solution Approach 1:
The system introduces an intermediary vaporization system that processes the NGL-rich liquid stream. This intermediary system selectively vaporizes ethane-plus components and delivers the vaporized products to the pipeline at the required high pressure (e.g., 2000 psig), while the fractionation column continues to maximize NGL recovery. The intermediary vaporization system acts as a bridge between liquid NGL recovery and high-pressure gas delivery requirements.
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 increases the efficiency of NGL recovery and methane-rich gas processing, allowing for selective diversion of LNG to vaporize methane and ethane, improving the overall processing efficiency and enabling cost-effective delivery of high-pressure methane-rich gas.
Implementation Method 1
LNG passes through a heat exchanger, thereby heating and vaporizing at least a portion of the LNG
Implementation Method 2
The partially vaporized LNG passes to a fractionation column where a liquid stream enriched with ethane plus and a methane-rich vapor stream are withdrawn
Implementation Method 3
The withdrawn methane-rich vapor stream passes through the heat exchanger to condense the vapor and produce a two phase stream
Implementation Method 4
A pump pressurizes the methane-rich liquid portion prior to vaporization and delivery to a pipeline
Implementation Method 5
The methane-rich gas portion may be compressed and combined with the vaporized methane-rich liquid portion or used as plant site fuel
Data Source
AI summary
Methods and systems for recovery of natural gas liquids (NGL) and a pressurized methane-rich sales gas from liquefied natural gas (LNG) are disclosed. In certain embodiments, LNG passes through a heat exchanger, thereby heating and vaporizing at least a portion of the LNG. The partially vaporized LNG passes to a fractionation column where a liquid stream enriched with ethane plus and a methane-rich vapor stream are withdrawn. The withdrawn methane-rich vapor stream passes through the heat exchanger to condense the vapor and produce a two phase stream, which is separated in a separator into at least a methane-rich liquid portion and a methane-rich gas portion. A pump pressurizes the methane-rich liquid portion prior to vaporization and delivery to a pipeline. The methane-rich gas portion may be compressed and combined with the vaporized methane-rich liquid portion or used as plant site fuel.