Carbon capture and storage Flashcards
How do amine scrubbers work?
Absorber – spray tower approx 40 C (gas moves up, amine moves down)
Heat exchanger
Regeneration, by heating in stripper 140 C (steam taken from low power turbine)
Amine recycled
CO2 recovered from mixture of CO2 and water – compressed for transportation and storage
What are the advantages of amine scrubbers
Produces high purity c02
Solvents are easy to move around
Can be applied to large scale industrial applications
What are the disadvantages of amine scrubbers
Solvents are corrosive
Regeneration cost
Amine needs regular replacement
How do solid absorbents work?
They have very large surface areas where gas molecules can adsorb and be desorbed from later.
Each gas will have a different affinity for each solid surface
What are the advantages of solid absorbents?
Regeneration is potentially less energy intensive than amine scrubbers
Avoids problems due to corrosion in liquid amine systems
Potential economic benefits over liquid amine systems
What are the disadvantages of solid absorbents?
Still in a development stage
Cost and lifetime still unknown
Adsorption capacity and selectivity can be low
What is gas separation membrane separation?
Small gas molecules e.g. H2 passes through the membrane while other parts of the flue gas e.g. CO2 are excluded
What is gas absorption membrane separation?
The membrane functions as a contact point between the flue gas and an absorbing liquid
What are the advantages of membrane separation
Can be used in hybrid systems
Provides high surface area for exchange
Operational problems are avoided as gas and liquid are not in direct contact
What are the disadvantages of membrane separation
Only available on a small scale
Issues with membrane stability
What is cryogenic separation?
In a cryogenic separation system, CO2 is physically separated from other gases by condensing it into a liquid form at an extremely low temperature.
The liquid CO2 produced would be immediately ready for transport to the disposal site.
Cryogenic separation of CO2 is handicapped by the cost of cooling such large quantities of gas, which makes the process un-economical on a large scale.
How is captured CO2 transported?
CO2 is compressed to about 150 times atmospheric pressure, for transport via steel pipelines. At this pressure, the gas becomes a supercritical fluid.
Supercritical fluids can be pumped like a liquid, but have very low resistance to flow, like a gas.
Where can captured CO2 be stored?
Depleted oil/gas reservoirs
Un-minable coal seams
Saline aquifers
Shale & basalt formations
The oceanOther than being stored what can the CO2 be used for?
Carbonification of minerals
Catalytic conversion to raw materials for organic synthesis
Biological sequestration
Why are some coal mines unminable?
Coal seams may be un-minable if they are too deep or thin.
All coals have methane adsorbed onto pore surfaces within the coal. Methane can be extracted by drilling wells into the coal seam and de-watering or de-pressurising the formation.
This leaves methane on the adsorbed on the coal surface
CO2 can be to recover more of this methane by preferential adsorption of the CO2 to the coal surface
as few as 3 to as many as 13 molecules of CO2 may be adsorbed for each molecule of methane released
This provides an excellent storage site for CO2 along with the additional benefit of enhanced coalbed methane (ECBM) recovery.
