Cryogenic Methane Separation Using Nitrogen Injection Against Flammability
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Solution Overview
Problem
Cryogenic distillation for methane-rich stream purification faces flammability risks due to oxygen presence, as existing methods either lack efficiency or introduce additional elements that complicate the process, such as catalytic deoxygenizers which create water and potentially lower reliability.
Innovation Solution
A method involving nitrogen enrichment by injecting a nitrogen-rich stream into the lower part of the distillation column to maintain operation outside the flammability zone, ensuring the feed stream is cooled and partially vaporized to mix with the nitrogen-rich gas, thereby avoiding oxygen accumulation and flammability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cryogenic distillation is used to purify methane-rich streams, then separation efficiency is improved, but flammability risk increases due to oxygen accumulation in the column
Solution Approach 1:
The patent introduces a nitrogen-rich stream into the lower part of the distillation column to create an inert atmosphere that prevents oxygen accumulation and eliminates flammability risks. The nitrogen acts as a diluent and inert gas, ensuring that the composition within the column remains outside the flammability zone while maintaining effective cryogenic separation of methane from oxygen and nitrogen impurities.
2Object-affected harmful factors
If catalytic deoxygenizers are added to remove oxygen, then flammability risk is reduced, but device complexity and maintenance needs increase
Solution Approach 1:
The patent extracts and removes the harmful oxygen component through cryogenic distillation separation, eliminating the need for additional catalytic deoxygenization equipment. By using the natural separation properties of cryogenic distillation and supplementing with nitrogen injection, the system achieves oxygen removal without adding complex catalytic reactors, filters, or auxiliary deoxygenation devices.
3Object-affected harmful factors
If nitrogen-rich stream is injected into the distillation column, then flammability zone is avoided, but energy consumption increases due to additional cooling requirements
Solution Approach 1:
The patent merges the nitrogen injection function with the existing cryogenic distillation process, utilizing the cold box and distillation column infrastructure already in place. The nitrogen-rich stream is introduced at the lower part of the column where it integrates with the ongoing separation process, allowing the system to achieve flammability prevention without requiring separate energy-intensive cooling systems for the nitrogen supplementation.
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 effectively prevents flammability issues by dispersing nitrogen throughout the column, ensuring safe and efficient cryogenic separation of methane-rich streams while maintaining high purity and reducing maintenance needs.
Implementation Method 1
the feed stream is cooled in order to produce a cooled stream
Implementation Method 2
the feed stream is sent to a condenser/reboiler where it partially vaporizes the bottom liquid in order to form a vaporized gas
Implementation Method 3
at least part of the cooled stream is sent to a distillation column... a bottom stream is withdrawn from the distillation column, the bottom stream being enriched with methane compared with the feed stream... a stream enriched with oxygen compared with the feed stream is withdrawn from the distillation column
Implementation Method 4
a nitrogen-rich liquid stream is vaporized by heat exchange with the feed stream in order to produce the nitrogen-rich gaseous stream
Data Source
AI summary
In a process for the cryogenic separation of a methane-rich feed stream containing between 3 and 35% of oxygen and also nitrogen, the feed stream is cooled in order to produce a cooled stream, at least one portion of the cooled stream is sent to a distillation column, a bottom stream is withdrawn from the distillation column, the bottom stream being enriched in methane compared to the feed stream, a stream enriched in oxygen compared to the feed stream is withdrawn from the distillation column, and a nitrogen-rich stream is sent to the column.