Natural Gas Liquefaction Using Multiple Tail Gas Pressure Streams
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Solution Overview
Problem
Conventional natural gas liquefaction methods are inefficient and costly, particularly for small-scale operations, as they require large-scale facilities, high investment costs, and pre-purification of 'dirty' natural gas, making them impractical for locations with low pressure drops and limited space, and they lack flexibility in handling varied gas pressures and impurities.
Innovation Solution
A method and plant design that utilizes a combined refrigerant and expansion process with multiple tail gas streams to liquefy natural gas, incorporating a multi-pass heat exchanger and expander valve, allowing for efficient cooling and separation of impurities, and enabling operation at various pressure levels and locations, including those with low pressure drops, without the need for pre-purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional large-scale liquefaction facilities are used, then liquefaction capacity is sufficient, but investment cost and space requirements increase significantly
Solution Approach 1:
The patent divides the liquefaction system into modular components including heat exchangers, expanders, and separation units that can be configured in different arrangements. This segmentation allows the system to be scaled appropriately for small-scale applications while maintaining effective liquefaction capability through optimized module configuration
Solution Approach 2:
The patent employs dynamic process control with multiple operating modes that can adapt to varying feed gas conditions and pressure drops. The system dynamically adjusts refrigerant flow rates, expander settings, and heat exchanger configurations to optimize performance for different scales of operation without requiring fixed large-scale infrastructure
2Object-generated harmful factors
If pre-purification of natural gas is implemented, then impurity handling is improved, but process complexity and cost increase
Solution Approach 1:
The patent converts impurities that would normally require pre-purification into manageable byproducts of the liquefaction process itself. Water and CO2 impurities are handled in-situ through the refrigeration and expansion process, where they condense or freeze and are separated along with the liquefied natural gas, eliminating the need for separate pre-purification trains
Solution Approach 2:
The liquefaction system performs self-purification through its own operational cycles. The refrigeration process naturally condenses and separates water and CO2 impurities from the natural gas feed, and the system includes integrated separation units that automatically remove these impurities without requiring external pre-treatment facilities
3Ease of operation
If single pressure level operation is used, then system simplicity is maintained, but adaptability to different locations and pressure conditions is reduced
Solution Approach 1:
The patent designs the liquefaction system with multi-functional capabilities to operate effectively across a wide range of pressure conditions. The heat exchangers, expanders, and control systems are configured to handle both high and low pressure drops, allowing the same basic system architecture to be deployed in diverse locations including remote areas with limited infrastructure pressure variations
Solution Approach 2:
The system incorporates adjustable operational parameters including variable refrigerant flow rates,可调 expander settings, and flexible heat exchanger configurations that can be optimized for different pressure levels. This allows the system to maintain simplicity while adapting to various pressure conditions through parameter adjustment rather than requiring fundamentally different system designs
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 enhances efficiency and reduces costs by allowing flexible, small-scale liquefaction of natural gas at various locations, utilizing tail gases efficiently, and minimizing operator oversight, while being transportable and suitable for use near populated areas.
Implementation Method 1
cooling the gaseous NG process stream by transferring heat from the gaseous NG process stream to the cooling stream
Implementation Method 2
expanding the cooled gaseous NG process stream to form a liquid NG process stream and a first tail stream comprising a gaseous NG
Data Source
AI summary
A method of natural gas liquefaction may include cooling a gaseous NG process stream to form a liquid NG process stream. The method may further include directing the first tail gas stream out of a plant at a first pressure and directing a second tail gas stream out of the plant at a second pressure. An additional method of natural gas liquefaction may include separating CO2 from a liquid NG process stream and processing the CO2 to provide a CO2 product stream. Another method of natural gas liquefaction may include combining a marginal gaseous NG process stream with a secondary substantially pure NG stream to provide an improved gaseous NG process stream. Additionally, a NG liquefaction plant may include a first tail gas outlet, and at least a second tail gas outlet, the at least a second tail gas outlet separate from the first tail gas outlet.