Processes and apparatuses for preparing liquified natural gas
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Solution Overview
Problem
Sub-quality natural gas reserves with compounds like neopentane, benzene, and toluene pose challenges during liquefaction due to freezing issues, requiring inefficient adsorbent bed volumes and excessive regeneration, especially when trying to remove C5 to C7 hydrocarbons and C8 or greater hydrocarbons from natural gas feeds.
Innovation Solution
A multi-bed adsorption process using different adsorbents for preferential adsorption of C8 or greater hydrocarbons and C5 to C7 hydrocarbons, minimizing bed volume and regeneration needs, with a first adsorbent for C8 or greater hydrocarbons and a second adsorbent with higher selectivity and capacity for C5 to C7 hydrocarbons, followed by a third adsorbent for residual water, to produce a C5 to C8-depleted stream suitable for liquefaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silica gels and aluminosilicate gels are used to adsorb C5 to C7 hydrocarbons including neopentane, cyclohexane, benzene, and heptane to desirable concentrations, then the natural gas can be depleted of these hydrocarbons, but the adsorbent beds require higher volume than would be required for C8 or greater hydrocarbons alone
Solution Approach 1:
The patent divides the adsorption process into two separate stages using different adsorbents: first adsorbing C8 or greater hydrocarbons with silica gel or aluminosilicate gel, then adsorbing C5 to C7 hydrocarbons with a different adsorbent having higher affinity for these lighter hydrocarbons. This segmentation allows each adsorbent to be optimized for its specific target compounds, achieving effective removal of C5 to C7 hydrocarbons without requiring excessive adsorbent bed volume.
Solution Approach 2:
The patent applies different adsorbent materials with specific local properties tailored to different hydrocarbon ranges. The first adsorbent (silica gel or aluminosilicate gel) has properties optimized for C8 or greater hydrocarbons, while the second adsorbent has properties specifically suited for C5 to C7 hydrocarbons including neopentane. This local quality optimization ensures efficient adsorption of each hydrocarbon class with minimal adsorbent volume.
2Quantity of substance
If adsorbent beds are designed to adsorb C5 to C7 hydrocarbons effectively, then the natural gas can be depleted to permissible ranges for liquefaction, but excessive regeneration requirements arise
Solution Approach 1:
The patent segments the adsorption function across two different adsorbent beds, allowing each to operate at optimal capacity for its specific hydrocarbon range. This prevents either adsorbent from becoming saturated too quickly with a broad spectrum of hydrocarbons, thereby reducing the frequency and extent of regeneration required while maintaining effective depletion of C5 to C7 hydrocarbons to permissible ranges.
Solution Approach 2:
The patent changes the parameters of the adsorption system by selecting adsorbents with different physical and chemical properties suited to different hydrocarbon ranges. This parameter optimization allows each adsorbent to operate more efficiently at its designated function, extending operational cycles between regenerations and reducing overall regeneration requirements.
3Object-affected harmful factors
If neopentane is removed from natural gas feed, then freezing during liquefaction is prevented, but neopentane is more difficult to separate due to its lower molecular weight and unique spherical molecular structure
Solution Approach 1:
The patent addresses the unique separation challenge of neopentane by applying a specific adsorbent material with local properties optimized for adsorbing C5 to C7 hydrocarbons including neopentane's spherical molecular structure. This targeted approach overcomes the difficulty posed by neopentane's lower molecular weight and unique structure, effectively removing it to prevent freezing during liquefaction.
Solution Approach 2:
The patent changes the adsorption parameters by selecting an adsorbent with specific pore structure and surface chemistry that is particularly effective for neopentane and other C5 to C7 hydrocarbons. This parameter optimization enables effective separation of neopentane despite its challenging molecular characteristics, preventing freezing issues during subsequent liquefaction.
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 maximizes efficiency in adsorbing C8 or greater and C5 to C7 hydrocarbons, minimizing their concentrations to permissible ranges for liquefaction, reducing adsorbent bed volumes and regeneration requirements, while ensuring effective removal of problematic hydrocarbons like neopentane and cyclohexane.
Implementation Method 1
Adsorption generally involves collection of molecules on a surface of an adsorbent. For example, silica gels, aluminosilicate gels, zeolite molecular sieves, and activated carbon are known adsorbents for adsorbing various compounds from natural gas.
Implementation Method 2
Adsorption generally involves collection of molecules on a surface of an adsorbent. For example, silica gels, aluminosilicate gels, zeolite molecular sieves, and activated carbon are known adsorbents for adsorbing various compounds from natural gas.
Implementation Method 3
Adsorption generally involves collection of molecules on a surface of an adsorbent. For example, silica gels, aluminosilicate gels, zeolite molecular sieves, and activated carbon are known adsorbents for adsorbing various compounds from natural gas.
Data Source
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AI summary
Processes and apparatuses are provided for preparing liquified natural gas from a natural gas feed that comprises C5 to C7 hydrocarbons and C8 or greater hydrocarbons. An exemplary process includes providing for the preferential adsorption of the C8 or greater hydrocarbons from the natural gas feed over adsorption of hydrocarbons having less than 8 carbon atoms to provide a C8-depleted natural gas stream. The process continues with the preferential adsorption of the C5 to C7 hydrocarbons from the C8-depleted natural gas stream over adsorption of hydrocarbons having less than 5 carbon atoms to form a C5 to C8-depleted natural gas stream. The C5 to C7 hydrocarbons are preferentially adsorbed with higher selectivity and capacity than adsorption of the C5 to C7 hydrocarbons during preferentially adsorbing the C8 or greater hydrocarbons. The C5 to C8-depleted natural gas stream is then liquified.