LNG Plant Hydrogen Separation for Fuel System Compatibility
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Solution Overview
Problem
The integration of hydrogen into natural gas pipelines poses challenges for liquefied natural gas (LNG) production plants due to hydrogen's different thermophysical properties, leading to operational impacts on fuel flow, fuel compressor performance, burner flame characteristics, and NOx emissions, and requiring significant modifications to gas turbine drivers and fuel systems.
Innovation Solution
A method involving the separation of a hydrogen-containing natural gas feed stream into a gaseous hydrogen-enriched and a gaseous hydrogen-depleted stream, utilizing processes such as membrane stages, adsorption, and distillation to produce a purified hydrogen stream suitable for export or further processing, while recycling the depleted stream to maintain hydrogen concentration within predetermined ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hydrogen is blended into natural gas pipelines, then renewable energy storage and transport capability is improved, but LNG plant operational stability and fuel system compatibility deteriorate
Solution Approach 1:
The patent extracts hydrogen from the natural gas feed stream using membrane separation technology before it enters the LNG liquefaction process. The membrane unit selectively permeates hydrogen molecules through the membrane material, separating them from methane and other natural gas components. This extracted hydrogen can then be handled separately, allowing the LNG plant to maintain operational stability while still accepting hydrogen-blended natural gas feeds.
Solution Approach 2:
The patent segments the natural gas processing flow into distinct sections: a hydrogen separation section using membrane units, a main LNG liquefaction section, and a hydrogen-rich stream handling section. This segmentation allows each section to be optimized for its specific function, with the membrane separation section dealing with hydrogen removal and the LNG section maintaining its original design parameters.
2Use of energy by moving object
If hydrogen concentration in fuel stream is increased, then renewable energy utilization is improved, but gas turbine operational performance and emissions control deteriorate
Solution Approach 1:
The patent converts the potentially harmful effect of hydrogen in the fuel stream into a benefit by separating hydrogen before combustion. The membrane separation process transforms the problem of hydrogen-induced NOx emissions into an opportunity to produce a concentrated hydrogen stream that can be used as a clean fuel product or injected into pipelines, while the LNG fuel stream has reduced hydrogen content and thus reduced NOx emission potential.
3Manufacturing precision
If hydrogen rejection is implemented, then LNG product purity is improved, but hydrogen resource utilization deteriorates
Solution Approach 1:
Instead of discarding the hydrogen separated from the natural gas feed, the patent recovers it as a valuable product stream. The hydrogen-rich stream exiting the membrane unit can be purified further and used as a marketable hydrogen product, injected back into natural gas pipelines, or utilized as a clean fuel source, thereby converting what would be a waste stream into an economic asset.
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
Enables efficient operation of LNG plants by managing hydrogen concentration, reducing the need for extensive modifications, and maintaining production levels even with high hydrogen content in the feed, while producing a saleable hydrogen product.
Implementation Method 1
utilizing processes such as membrane stages
Implementation Method 2
utilizing processes such as membrane stages, adsorption, and distillation
Implementation Method 3
utilizing processes such as membrane stages, adsorption, and distillation
Data Source
AI summary
Liquefaction systems and methods are disclosed that are adapted to process a natural gas stream having a substantial concentration of hydrogen and where the concentration of hydrogen may vary in the natural gas stream. In some implementations, an expanded liquefied natural gas stream may be separated into a hydrogen enriched endflash stream and a hydrogen depleted LNG stream, and a second gaseous hydrogen depleted stream may be produced from the hydrogen enriched endflash stream and/the hydrogen depleted LNG stream. In other implementations, the pressure of the endflash compressor may be controlled for the purpose of maintaining a hydrogen concentration in a fuel stream (often the endflash stream) within a desired range. Some implementations may include pre- or post-liquefaction purification using, for example, membranes, adsorption, partial condensation, distillation, stripping, and electrochemical membranes.