Process and apparatus for the separation by cryogenic distillation of a mixture of methane, carbon monoxide and hydrogen
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Solution Overview
Problem
The existing cryogenic distillation processes for separating methane, carbon monoxide, and hydrogen are limited in their ability to quickly adjust to changes in feed flow rates, leading to instability and safety hazards due to the reliance on liquid carbon monoxide storage, which is slow to build up and poses security risks.
Innovation Solution
Storing liquid methane downstream of the CO/CH4 column and upstream of the methane wash column, with a methane storage tank that regulates the liquid level and purge flow to accommodate varying demand, allowing for faster adjustments in feed flow rates without destabilizing the heat exchange line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid carbon monoxide storage tank is used to improve feed flow variation speed, then carbon monoxide supply response improves, but hydrogen supply response does not improve and security hazards increase
Solution Approach 1:
The patent introduces liquid methane as an intermediary substance to mediate between the feed flow variations and the product output. Instead of directly storing and vaporizing carbon monoxide, the system stores liquid methane which then vaporizes to provide refrigeration and allow for faster flow rate adjustments. This intermediary approach avoids the security hazards of large-scale carbon monoxide storage while still enabling rapid response to demand changes.
Solution Approach 2:
The patent changes the physical state and composition parameters of the stored substance from liquid carbon monoxide to liquid methane. This parameter change allows the system to achieve the same refrigeration effect and flow rate adjustment capability while eliminating the security risks associated with storing large amounts of carbon monoxide. The methane serves as a safer alternative that can be stored and vaporized on-demand.
2Adaptability or versatility
If liquid methane amount is increased to accommodate feed flow changes, then feed flow adjustment capability improves, but liquid level control stability deteriorates
Solution Approach 1:
The patent implements dynamic control of the methane purge flow rate based on the liquid level in the column. The control system continuously adjusts the purge flow to maintain stable liquid levels while accommodating feed flow variations. This dynamic adjustment allows the system to adapt to changing conditions without compromising stability, as the purge rate is modulated in real-time according to liquid level measurements.
Solution Approach 2:
The patent employs feedback control where the liquid level in the column is continuously monitored and used to adjust the methane purge flow rate. When the liquid level deviates from the setpoint, the control system modifies the purge rate to bring the level back to the desired range. This feedback mechanism ensures that the system can handle feed flow changes while maintaining stable liquid levels and preventing column flooding or dry-out conditions.
3Stability of the object's composition
If methane purge flowrate is increased to maintain liquid level, then liquid level stability improves, but heat exchange line thermal equilibrium is disturbed
Solution Approach 1:
The patent applies preliminary action by controlling the methane purge flow rate in advance to prevent thermal equilibrium disturbances. The control system anticipates the thermal impact of increased purge rates and adjusts other parameters accordingly before the disturbance occurs. This proactive approach allows the system to maintain liquid level stability while minimizing the impact on the heat exchange line's thermal equilibrium by pre-compensating for the additional cooling effect.
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 faster and more stable adjustments in carbon monoxide and hydrogen flow rates, reducing the need for liquid carbon monoxide storage and minimizing safety hazards while maintaining thermal equilibrium in the heat exchange line.
Implementation Method 1
provision of refrigeration by vaporization of the liquid methane purge in the heat exchange line
Implementation Method 2
separation by cryogenic distillation of a mixture of methane, carbon monoxide and hydrogen
Data Source
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AI summary
In a process for the cryogenic separation of a feed mixture of at least carbon monoxide, hydrogen and methane, the feed mixture is separated in a methane wash column (1) fed by a liquid methane stream (11) at the top of the methane wash column to produce a gas (12) enriched in hydrogen, a liquid stream (13) from the bottom of the methane wash column is treated to produce a mixture of carbon monoxide and methane (15), the mixture of carbon monoxide and methane is separated in a separation column (3) to produce a gas enriched in carbon monoxide (16) and a liquid methane flow (4) at least part of which forms a purge stream (20), the purge stream being varied to take account of load variations.