Method for separating a mixture containing at least nitrogen and methane
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cryogenic distillation processes for separating nitrogen and methane in natural gas face inefficiencies due to substantial recirculation of liquid in conventional heat exchangers, leading to higher bath temperatures and increased pressure differences between columns, which are not optimized for equivalent purity of methane products.
Innovation Solution
Implementing a film-evaporator technology with a stack of plates and fins in the heat exchanger, allowing counter-current exchange without recirculation, where nitrogen-rich gas condenses in one series of passages and methane-rich liquid evaporates in another, adjacent series, optimizing temperature differences and reducing column heights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional bath evaporator heat exchanger is used, then the exchange can be performed, but substantial recirculation of liquid is required which leads to higher bath temperatures and increased pressure differences between columns
Solution Approach 1:
The invention extracts the recirculation loop from the heat exchanger system by implementing a single-pass counter-current exchange configuration. The liquid flows downward through the evaporator sections while gas flows upward through condenser sections, with each fluid passing through the heat exchanger only once, eliminating the need for recirculation pumps and associated complexity
Solution Approach 2:
The invention inverts the conventional approach by using direct counter-current flow without recirculation. Instead of circulating liquid through the same sections multiple times (conventional approach), the system uses a single pass where liquid flows down and gas flows up in opposite directions, achieving better thermal efficiency without recirculation infrastructure
2Temperature
If recirculation is used in the heat exchanger, then evaporation can be maintained, but the evaporation temperature becomes virtually constant leading to limited temperature range for heat exchange
Solution Approach 1:
The invention inverts the conventional recirculation approach by implementing a single-pass counter-current system. Liquid flows downward through evaporator sections experiencing progressively lower temperatures, while gas flows upward through condenser sections, creating a continuous temperature gradient that maximizes the temperature range utilized for heat exchange
Solution Approach 2:
The system dynamically utilizes the temperature gradient along the flow path, with liquid being progressively cooled as it descends through evaporator sections and gas being progressively cooled as it ascends through condenser sections, optimizing heat transfer at each point along the gradient rather than maintaining a constant temperature
3Stress or pressure
If conventional heat exchanger design is used, then separation can be achieved, but the pressure difference between columns must be increased to compensate for exchange inefficiencies
Solution Approach 1:
The invention inverts the conventional approach by achieving efficient heat and mass transfer through counter-current flow without requiring high pressure differences. The single-pass design with alternating evaporator and condenser sections allows effective separation at lower pressure gradients, improving overall system efficiency and reducing energy consumption
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 enables efficient counter-current heat exchange with reduced temperature differences, improving methane product purity and reducing column heights while maintaining performance, by allowing true counter-current fluid exchange without recirculation, thus addressing the inefficiencies in conventional systems.
Implementation Method 1
the heat exchanger consisting of a stack of plates and fins... allowing counter-current exchange without recirculation
Implementation Method 2
nitrogen-rich gas condenses in one series of passages
Implementation Method 3
methane-rich liquid evaporates in another, adjacent series
Data Source
AI summary
A method for separating a mixture containing at least nitrogen and methane by cryogenic distillation in a first column operating in a first pressure and a second column operating at a second pressure lower than the first pressure, the mixture being separated in the first column to form a gas enriched in nitrogen and a liquid enriched in methane, at least a portion of the gas enriched in nitrogen being at least partially condensed in a heat exchanger and returned to the first column, the gas enriched in nitrogen is sent into the heat exchanger by the bottom, ascends in a first series of passages of the exchanger and condenses therein at least partially, the liquid formed descending in these passages of the first series and exiting by the bottom of the exchanger.