Carbon Capture
Amine Based Techniques
Amine solvent-based technology has recently established itself as a viable technology for CO2 capture.. This technology applies to the polluting power industry, especially for high CO2 producing coal-fired plants. Post combustion CO2 capture from flue gas is the dominating technology for this purpose.
Dr. Thomas Adams [1, pg. 239]
Methyl-diethanolamine is quite selective for CO2 over H2 (meaning it will dissolve CO2 in large amounts, but H2 in very small amounts), so it is ideal for CO2 / H2 separations.
Pressure Swing Adsorption Units
Explanation from [2]
Pressure swing adsorption units use beds of solid adsorbent to separate impu- rities from hydrogen streams leading to high-purity high-pressure hydrogen and a low-pressure tail gas stream containing the impurities and some of the hydro- gen. The beds are then regenerated by depressurizing and purging...
The pressure swing adsorption (PSA) technology is based on a physical binding of gas molecules to adsorbent material. The respective force acting between the gas molecules and the adsorbent material depends on the gas com- ponent, type of adsorbent material, partial pressure of the gas component, and operating temperature. The separation effect is based on differences in binding forces to the adsorbent material. Highly volatile components with low polarity, such as hydrogen, are practically nonadsorbable as opposed to molecules such as nitrogen, carbon monoxide, carbon dioxide, hydrocarbon derivatives, and water vapor. Consequently, these impurities can be adsorbed from a hydrogen-containing stream, and high-purity hydrogen is recovered...
The pressure swing adsorption process works at basically constant temper- ature and uses the effect of alternating pressure and partial pressure to perform adsorption and desorption. Since heating or cooling is not required, short cycles within the range of minutes are achieved. The process consequently allows the economical removal of large amounts of impurities. Adsorption is carried out at high pressure (and hence high respective partial pressure) typically in the range of 10–40 bar until the equilibrium loading is reached. At this point in time, no further adsorption capacity is available, and the adsorbent material must be regenerated. This regeneration is accomplished by lowering the pressure to slightly above atmospheric pressure resulting in a respective decrease in equi- librium loading. As a result, the impurities on the adsorbent material are des- orbed, and the adsorbent material is regenerated. The amount of impurities removed from a gas stream within one cycle corresponds to the difference of adsorption to desorption loading. After termination of regeneration, pressure is increased back to adsorption pressure level, and the process starts again from the beginning.
Commentary
Andrew Finkel, Former Chief Scientist of Australia
I learnt from researchers that CCS for hydrogen production is significantly more cost-effective for two crucial reasons. First, since carbon dioxide is left behind as a residual part of the hydrogen production process, there is no additional step, and little added cost, for its extraction. And second, because the gas mixture at the output of the process is at much higher pressure than flue gases, the extraction of the carbon dioxide is more energy efficient and it is easier to store... [T]he United Nations IPCC special report last year .. spoke of the importance of CCS for mitigating emissions
References
[1] Adams, Learn Aspen Plus in 24 Hours, Second Edition
[2] Speight, Heavy Oil Recovery and Upgrading