Cryogenic CO/H₂/CH₄ Separation Without CO Pumps or Reboilers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for cryogenic separation of carbon monoxide, hydrogen, and methane in synthesis gas face inefficiencies, such as the use of carbon monoxide pumps and reboilers in CO/CH4 columns, and produce hydrogen-rich gas at low pressure, leading to suboptimal thermal integration and increased energy costs.
Innovation Solution
A process utilizing a cold box with a nitrogen cycle and/or methane cycle for scrubbing impure CO, where the separation energy is contributed by N2 or CH4 cycles, eliminating the need for CO pumps and reboilers by using a compressor to recycle gas and optimizing pressure conditions for efficient methane recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CO pumps and reboilers are used in CO/CH4 separation columns, then separation efficiency is improved, but device complexity and energy consumption increase
Solution Approach 1:
The invention extracts and eliminates the CO pump from the system by redesigning the feed system. Instead of pumping CO into the scrubbing column, the process uses a flash drum where pressure reduction causes automatic separation and feed delivery to the CO/CH4 column, removing the need for positive displacement pumping of CO.
Solution Approach 2:
The invention extracts and eliminates the reboiler from the CO/CH4 column by implementing a partial condenser at the column top that provides reflux. The condensation of overhead vapors and return of liquid reflux creates the necessary liquid flow down the column without requiring external reboiling at the column bottom.
2Use of energy by moving object
If hydrogen-rich gas is produced at low pressure, then energy consumption is reduced, but productivity and process integration efficiency worsen
Solution Approach 1:
The invention merges the CO/CH4 separation column with a methane compression and recycling system. The methane product from the column bottom is compressed and partially recycled back to the column bottom as reflux, while the remainder is sent to further processing. This integration allows the system to operate efficiently at higher pressures without excessive energy consumption.
Solution Approach 2:
The invention changes the operating pressure parameter of the CO/CH4 separation column from low pressure to higher pressure (typically 30-100 psig). This pressure increase improves productivity by enabling more efficient methane recovery and allows better integration with downstream processes, while the energy penalty is offset by the elimination of the CO pump and optimized reflux system.
3Productivity
If CO pumps are used, then methane recovery efficiency is improved, but device complexity and operational cost increase
Solution Approach 1:
The invention extracts and eliminates the CO pump from the system by redesigning the feed system. Instead of pumping CO into the scrubbing column, the process uses a flash drum where pressure reduction causes automatic separation and feed delivery to the CO/CH4 column, removing the need for positive displacement pumping of CO.
Solution Approach 2:
The invention implements a self-service feed system where the flash drum automatically separates and delivers CO-rich liquid to the CO/CH4 column based on pressure differential and phase equilibrium. The system uses its own pressure and temperature conditions to drive the feed flow without external pumping, achieving self-service operation.
4Manufacturing precision
If reboilers are used in CO/CH4 column, then separation performance is improved, but energy consumption and operational cost increase
Solution Approach 1:
The invention extracts and eliminates the reboiler from the CO/CH4 column by implementing a partial condenser at the column top that provides reflux. The condensation of overhead vapors and return of liquid reflux creates the necessary liquid flow down the column without requiring external reboiling at the column bottom.
Solution Approach 2:
The invention uses phase transition (condensation) at the top of the CO/CH4 column to provide the reflux necessary for separation. By condensing overhead vapors and returning liquid reflux to the column, the system achieves effective separation without requiring the phase change (boiling) that would occur in a reboiler at the column bottom.
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 significant recovery of methane without CO pumps or reboilers, improving thermal integration and producing methane at higher pressures, thus enhancing the efficiency and cost-effectiveness of the separation process.
Implementation Method 1
the mixture cooled to a cryogenic temperature in a heat exchanger
Implementation Method 2
scrubbing with impure CO where the separation energy is contributed by N2 cycle and/or by CH4 cycle
Implementation Method 3
a bottom liquid from the stripping column is sent to a separation column, and a liquid enriched in methane is withdrawn from the bottom of the separation column
Implementation Method 4
the separation column has a top condenser cooled by a closed nitrogen cycle comprising a gaseous nitrogen compressor
Implementation Method 5
the vaporized liquid enriched in methane is compressed in a compressor and a part of the compressed gas is returned at the bottom of the separation column
Data Source
AI summary
In a process of the separation of a mixture of carbon monoxide, hydrogen and methane, the mixture is sent to a scrubbing column, a bottom liquid withdrawn at the bottom of the scrubbing column is depleted in hydrogen with respect to the mixture and is sent to a stripping column, a bottom liquid from the stripping column is sent to a separation column and a liquid enriched in methane withdrawn from the bottom of the separation column is vaporized in order to form a final product.