Two-Stage CO2 Absorption System Using Superatmospheric Flash Vessels
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Solution Overview
Problem
Existing CO2 removal processes from synthesis gas in the Haber-Bosch process are inefficient due to the need for costly compressors and loss of latent heat, posing safety risks and economic challenges.
Innovation Solution
A process involving a two-stage absorption and regeneration system where CO2 is removed from fluid streams using an aqueous absorption medium, with partial regeneration in flash vessels and thermal regeneration in a stripper, eliminating the need for compressors and utilizing latent heat for energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a subatmospheric pressure flash vessel is used to increase CO2 absorption capacity, then the absorption medium efficiency is improved, but the plant cost increases due to the need for a costly compressor and safety risks
Solution Approach 1:
Instead of using subatmospheric pressure (vacuum) to enhance CO2 absorption as in prior art, this patent inverts the approach by using superatmospheric pressure (1.05 to 3.0 bar) in the flash vessel. This pressure inversion eliminates the need for compressors and vacuum systems while maintaining effective CO2 absorption capacity through pressure-driven degasification.
Solution Approach 2:
The patent replaces expensive, complex compressor equipment with simple, inexpensive pressure control valves and flash vessels. The system uses readily available atmospheric pressure differential rather than requiring costly mechanical compression devices, significantly reducing capital expenditure and maintenance requirements.
2Quantity of substance
If external driving steam is used to operate the steam ejector, then water balance is maintained, but energy consumption increases and latent heat is lost
Solution Approach 1:
The patent converts the previously wasted latent heat of water vapor in the flash vessel off-gas into a useful resource. By introducing this hot vapor to preheat the incoming absorption medium, the system recovers thermal energy that would otherwise be lost, reducing the steam requirement for heating and improving overall energy efficiency.
Solution Approach 2:
The patent merges the heating function and water balance function into a single integrated process. The steam ejector that previously consumed external driving steam is replaced by a system where process vapor from the flash vessel directly provides both heating and water make-up, combining multiple functions into one efficient operation.
3Loss of substance
If make-up water is introduced in liquid form into the absorber, then amine losses are reduced, but the water balance becomes difficult to maintain
Solution Approach 1:
The patent introduces make-up water in vapor form through the flash vessel off-gas stream rather than as liquid injection. This vapor-phase water addition effectively distributes water throughout the gas-liquid contact zones without creating localized liquid surges, maintaining amine contact efficiency while balancing water requirements.
Solution Approach 2:
The flash vessel off-gas stream acts as an intermediary carrier for make-up water. Instead of directly injecting liquid water into the absorber (which causes amine loss), the water is introduced as vapor in the off-gas stream, which then distributes it evenly through the system without direct liquid-amine contact that would cause losses.
4Productivity
If the flash vessel is operated at subatmospheric pressure, then CO2 absorption capacity increases, but safety risks increase due to hydrogen atmosphere and potential explosive conditions
Solution Approach 1:
The patent inverts the pressure operation from subatmospheric (vacuum) to superatmospheric (1.05 to 3.0 bar). This pressure inversion fundamentally eliminates the safety hazard of hydrogen-rich vacuum systems while maintaining effective CO2 absorption through pressure-driven mass transfer in the flash vessel.
Solution Approach 2:
The patent converts the potential hazard of pressurized hydrogen-containing gas into a beneficial safety feature. By operating at moderate superatmospheric pressure rather than vacuum, the system avoids the critical safety issue of air ingress into vacuum systems, and the pressurized system becomes inherently safer against external atmospheric contamination.
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 process enhances energy efficiency by retaining latent heat and reducing costs, improving safety by eliminating the need for compressors and minimizing amine losses, while maintaining effective CO2 removal from synthesis gas.
Implementation Method 1
the loaded absorption medium is depressurized in a first flash vessel to a pressure of from 1.2 to 3 bar (absolute), giving a sub-partially regenerated absorption medium and a first CO2-comprising gas stream
Implementation Method 2
the water vapor-comprising, second CO2-comprising gas stream is compressed by means of a jet pump and brought into direct heat exchange contact with the loaded absorption medium in the first flash vessel
Implementation Method 3
the jet pump being operated by means of the third CO2-comprising gas stream
Data Source
AI summary
A plant for removing CO2 from a fluid stream via an aqueous absorption medium contains a) a first absorption zone for treating the fluid stream with a partially regenerated absorption medium, b) a second absorption zone for treating the treated fluid stream with a regenerated absorption medium, c) a first flash vessel for depressurizing the loaded absorption medium, d) a second flash vessel for depressurizing the sub-partially regenerated absorption medium, e) a stripper for thermally regenerating the partially regenerated absorption medium, f) a conduit for feeding a substream of the partially regenerated absorption medium into the first absorption zone and a conduit for feeding a further substream of the partially regenerated absorption medium into a stripper, g) a conduit for recirculating the regenerated absorption medium to the second absorption zone, and h) a jet pump for compressing the water vapor-comprising, second CO2-comprising gas stream.