LNG Production with Liquid Nitrogen Refrigerant Decontamination
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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, requiring effective decontamination methods to avoid atmospheric venting of harmful gases.
Innovation Solution
A liquefied natural gas production system utilizing liquid nitrogen as a primary refrigerant, which includes a heat exchanger for partial vaporization and condensation of the nitrogen stream, followed by a greenhouse gas removal unit using a distillation column and heat pump condenser/reboiler system to separate and remove contaminants, allowing for circulation of the nitrogen stream multiple times and pressure reduction through expanders, ensuring low greenhouse gas levels in the vaporized nitrogen before venting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If liquid nitrogen is used as refrigerant in shared storage facilities with LNG, then storage efficiency is improved, but greenhouse gas contamination occurs in the nitrogen stream
Solution Approach 1:
The patent extracts and removes greenhouse gas contaminants (methane, ethane, propane) from the vaporized liquid nitrogen stream using a distillation column system. The separation process isolates the harmful components from the nitrogen stream, allowing the cleaned nitrogen to be vented safely while removing the contamination issue that would otherwise prevent shared storage facility usage.
Solution Approach 2:
The patent recovers and removes contaminated components from the nitrogen stream through distillation. The greenhouse gas contaminants are separated and removed from the system, while the purified nitrogen is retained for venting. This recovery process transforms the contaminated stream into a usable clean stream, resolving the contradiction between sharing facilities and maintaining purity.
2Manufacturing precision
If distillation column is used to remove greenhouse gases, then purification is improved, but energy consumption increases due to heating and cooling requirements
Solution Approach 1:
The patent merges the condenser and reboiler functions into a single heat exchanger unit. The condenser cools the overhead vapor stream while the reboiler heats the bottom liquid stream, and these two processes are combined in one piece of equipment. This allows heat to be exchanged between the two streams simultaneously, recovering energy that would otherwise be lost and significantly reducing external heating and cooling requirements.
Solution Approach 2:
The patent implements continuous operation of the distillation column with continuous circulation of the liquid nitrogen stream through multiple passes. The heat pump system operates continuously to provide the necessary heating and cooling, maintaining steady-state purification without interruption. This continuous operation optimizes energy utilization and maintains consistent purification efficiency.
3Productivity
If liquid nitrogen stream is circulated multiple times through heat exchanger, then liquefaction efficiency is improved, but system complexity increases
Solution Approach 1:
The patent makes the heat exchanger serve multiple functions: it acts as both the condenser for the distillation column overhead stream and the reboiler for the bottom stream, and simultaneously serves as the heat exchanger for cooling the natural gas feed stream. This multi-functionality allows the nitrogen stream to be circulated through the same equipment multiple times for different purposes, improving liquefaction efficiency without adding proportional complexity.
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 method effectively removes greenhouse gases from the nitrogen stream, enabling the use of shared storage facilities and reducing environmental impact by venting clean gaseous nitrogen, thus enhancing the efficiency and environmental sustainability of LNG production.
Implementation Method 1
at least one heat exchanger that exchanges heat between the liquefied nitrogen stream and the natural gas stream to at least partially vaporize the liquefied nitrogen stream and at least partially condense the natural gas stream
Implementation Method 2
at least partially vaporize the liquefied nitrogen stream
Implementation Method 3
at least partially condense the natural gas stream
Implementation Method 4
a greenhouse gas removal unit configured to remove greenhouse gas from the at least partially vaporized nitrogen stream
Implementation Method 5
a heat pump condenser and reboiler system to increase a pressure and condensing temperature of an overhead stream of the distillation column, wherein the overhead stream of the distillation column is cross-exchanged with a bottoms stream of the distillation column to affect both an overhead condenser duty and a bottom reboiler duty
Implementation Method 6
a pressure reduction device, connected to an output of the heat pump heat exchanger, and configured to reduce a pressure of the distillation column overhead stream after the distillation column overhead stream has passed through the heat pump heat exchanger
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.