Carbon Dioxide Capture at Coal Power Stations

8/3/2019 Carbon Dioxide Capture at Coal Power Stations

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CAPTURE OF CO2AT

COAL POWER STATIONS

THIRUSHKA T. GOVENDER


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REDUCING

CO2EMISSIONS

OPERATE POWERPLANTS AT THEBEST EFFICIENCY

INVEST INCLEAN COAL

TECHNOLOGIES THAT

IMPROVE THELEVEL OFEFFICIENCY INCOAL-FIREDPOWERPLANTS SUCH

CARBONCAPTURE ANDSTORAGE(CCS)


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Process based on capturing CO2 and storing insuch a way that it does not enter theatmosphere

3 different carbon-capture strategies are beinginvestigated today :o Post-combustion captureo Pre-combustion Captureo

Oxy-fuel combustion

CARBON CAPTURE ANDSTORAGE


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POST COMBUSTIONCAPTURE


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PRECOMBUSTION CAPTURE


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Combustion of Coal takes place inpure Oxygen

Therefore the flue gas is mainlycomprised of CO2 and watervapour (which may be cooled and

condensed to remove the water )so there is no separation problem

Such plants require oxygen

OXY FUEL COMBUSTION


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Separation & recoverymethods

Features

Absorptionmethod

Chemicalabsorption

Chemical reaction using a CO2

absorbentLarge amount of energy required

Physicalabsorption

Absorbent used to physicallyremove CO2CO2 released by depressurization

Membraneseparation

Polymermembrane

Differences between gas speedsof transmission through

membrane

Liquidmembrane

Membrane holding a carriersubstance that selectivelytransmits CO2

Inorganic Transmission through a porous


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Conventional to use scrubbers to removeCO2 from exhaust gas which energyintensive & expensive

Challenge lies in developing a method thatcan be inexpensively and easily retrofittedinto existing power plants.

Following new technology is beingresearched: Zeolite Crystals Nanotechnology Membranes Bio CCS Algal Synthesis

New Methods of CO2Capture


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Omar Yaghi,a chemist at UCLA combinedorganic molecules and metal atoms to formhighly porous crystals

Structure resembles industrial

materials called zeolites

1 litre of UCLA crystals stores up to 80l ofCO2

They're made of metal atoms bridged by one

CRYSTALS TO CAPTURECO2


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New type of membrane internationallypatented by researchers at the NorwegianUniversity of Science & Technology in

Trondheim

Membrane made of plastic material ,

structured by means of nanotechnology

Catches CO2 while other waste gasesallowed to pass freely

Membranes based on nano-structuredmaterials are eco-friendl and will reduce the

NanotechnologyMembrane


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CO2 and other gases in exhaust gas streamis injected into membranes containing wastewater and select strains of algae

The algae ,together with sunlight/UV-lightconvert that CO2 and use it to reproduce toform an oil rich biomass that doubles inmass every 24hrs

AdvantagesTechnology is entirely retrofittable to existing

plants ,regardless of the composition of the

exhaust gas stream

Bio CCS Algal Synthesis


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If Carbon Capture is to be implemented- suitablemeans of storing the resultant gas must be found

The sequestered CO2 must remain isolatedindefinitely if the capture and storage strategy isto be effective

Therefore all sequestration sites must be

monitored closely for decades or longer

CARBON STORAGE


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FOUR STAGES OF CCS


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Depth > 800m

Impermeable Cap Rock

Porous Rock (not Cavern)

Long term mineralisation

STORAGECHARACTERISTICS


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Technology for CCS not currently practised inSA

South Africa emits over 400 million tonnes ofCO2 annually of which ~60% arecapturable and therefore potentiallyavailable for CCS

South African CCS center (SACCSC)established in 2009 directed by TonySurridge

CCS IN SOUTH AFRICA


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CCS TIME SCALE IN SA


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CO2 EMISSIONS IN SOUTHAFRICA


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ATLAS ON GEOGRAPHICALSTORAGE OF CO2 IN SA


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Potential Storage (excluding Karoo) 150 Gt 98% offshore

Need 4 Gt to Store 40 Mt/yearFurther investigation :

Karoo under further investigation Zululand basin (UK Govt end Mar2011) Onshore Outinequa Basin (europe Aid start Feb

2011)

ATLAS SUMMARY


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Major problem is gas leakages

Cost of sequestration process is quite high at

the moment

Excessive use of this method slows down

search for cleaner sources of energy

DISADVANTAGES OF CCS


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QUESTIONS ????

Carbon Dioxide Capture at Coal Power Stations

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