LNG Pre-Cooling With Liquid Nitrogen Contaminant Removal
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Solution Overview
Problem
Conventional LNG production systems face challenges in efficiently removing greenhouse gas contaminants from liquid nitrogen streams used for liquefying natural gas, particularly when these streams share storage facilities with LNG, leading to environmental concerns and increased costs due to the need for extensive decontamination before venting.
Innovation Solution
A system utilizing liquid nitrogen as a primary refrigerant, which includes a heat exchanger network and a greenhouse gas removal unit with a distillation column and heat pump condenser/reboiler system to efficiently separate and remove contaminants, allowing for the reuse of storage facilities and reducing environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If liquid nitrogen and LNG share storage facilities, then infrastructure costs are reduced and facility utilization is improved, but greenhouse gas contamination of the liquid nitrogen stream occurs
Solution Approach 1:
The patent extracts and removes greenhouse gas contaminants (methane, ethane, propane) from the liquid nitrogen stream through a distillation column system. The separation process isolates the harmful contaminants from the liquid nitrogen, allowing the purified nitrogen to be safely stored and used while the contaminants are removed and disposed of appropriately.
Solution Approach 2:
The patent changes the physical parameters (temperature, pressure) of the liquid nitrogen stream to enable phase separation and distillation. By controlling temperature and pressure conditions in the distillation column, the system exploits differences in volatility between nitrogen and greenhouse gas contaminants to achieve separation, transforming the contaminated stream into purified nitrogen suitable for storage sharing.
2Object-affected harmful factors
If extensive decontamination is performed before venting liquid nitrogen, then environmental emissions are reduced, but operational costs and processing time increase
Solution Approach 1:
The patent performs decontamination as a preliminary action during the storage and handling process, not just before venting. The distillation column continuously or periodically removes contaminants from the liquid nitrogen stream while it is in storage, ensuring that by the time venting is needed, the nitrogen is already purified. This preliminary cleanup action eliminates the need for extensive end-stage decontamination procedures.
Solution Approach 2:
The system uses the natural physical properties of the contaminants (higher boiling points than nitrogen) to enable self-separation through distillation. The process leverages the inherent volatility differences between substances, requiring minimal external energy input compared to active removal methods, thus maintaining operational efficiency while achieving effective decontamination.
3Reliability
If conventional refrigeration compressors are used for LNG production, then liquefaction capability is achieved, but carbon emissions and capital investment requirements increase
Solution Approach 1:
The patent replaces conventional mechanical refrigeration compressors with a cryogenic distillation system using liquid nitrogen. Instead of using mechanical compression and heat exchange systems that consume significant energy and produce carbon emissions, the system uses the cryogenic properties of liquid nitrogen and phase separation through distillation to achieve LNG production, eliminating the need for large carbon-emitting compressor stations.
Solution Approach 2:
The patent exploits phase transitions of natural gas components during cryogenic distillation. By controlling temperature and pressure to induce phase changes, the system separates and liquefies natural gas components without requiring mechanical compression. The phase transition behavior of different hydrocarbons at cryogenic temperatures enables selective condensation and separation, achieving reliable LNG production through thermal rather than mechanical means.
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
The system effectively removes greenhouse gas contaminants from the liquid nitrogen stream, enabling the use of shared storage facilities while minimizing environmental emissions and operational costs, and ensures the natural gas is efficiently liquefied and vented without significant greenhouse gas release.
Implementation Method 1
at least one heat exchanger that exchanges heat between the refrigerant stream and the natural gas stream to at least partially vaporize the refrigerant stream and at least partially condense the natural gas stream
Implementation Method 2
a distillation column and heat pump condenser/reboiler system to efficiently separate and remove contaminants
Implementation Method 3
a distillation column and heat pump condenser/reboiler system to efficiently separate and remove contaminants
Data Source
AI summary
Described herein are systems and processes to produce liquefied natural gas (LNG) using liquefied nitrogen (LIN) as the refrigerant. Greenhouse gas contaminants are removed from the LIN using a greenhouse gas removal unit. The LNG is compressed prior to being cooled by the LIN.