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CO2 absorption in power plantsEmphasizing on CO2 absorption
in biphasic solvent
Athina KouneliSupervisor: Mathias CehlinExaminer: Taghi Karimipanah
2016
Faculty Of Engineering And Sustainable Development
Master Programme in Energy Engineering, Energy Online
Thesis Project
Motivation Enviromental
factors (greenhouse effect)
Financial factors (CO2 trading)
EU & CO2 Emissions (1/2)
Kyoto ProtocolCO2 emissions reduction target for EU
compared to 1990 1st commitment period (2008-2012) 8% 2nd commitment period (2013-2020)
20%
Paris AgreementGlobal climate deal, to enter in force in
2020
EU & CO2 Emissions (2/2)
Source: Eurostat
EU 2013
Power plants
Carbon capture & storage Capture (plants) TransportPipelines, ships etc. StorageGeological formation
Aim/ Outline Present & compare CO2 capture technologies Select and analyze CO2 capture with absorption Examine the biphasic solvents as alternative option
to classic amines – Energy saving
MethodLiterature review Scientific papers, patents, educational sites Selection of app. 50 references / app. 100 references
Carbon dioxide capture Post combustion (separated from fuel gas
compounds) Pre combustion (fuel production without carbon) Oxyfuel combustion (combustion rich in O2)
Post combustion (1/4)
CO2 is captured from the exhaust gases of a combustion process. The carbon dioxide is then compressed and transported and stored.
Capture methods Absorption Adsorption Membranes
Post combustion (2/4)Absorption•Physical absorption (high concentration of CO2, at high pressures), physical solvents, less regeneration energy•Chemical absorption, aqueous alkaline solvent (usually amine)
25-30% net power output of a coal power plant is used for the solvent regeneration
Post combustion (3/4)Adsorption
CO2 molecules adhere to solid sorbents with high surface area (e.g. zeolites) intermolecular forces CO2 is separated from the flue gases
1. Flue gas enters a bed of solids adsorb only CO2
2. Regeneration of the bed when fully loaded (reducing pressure/raising the temperature)
& (repeated cycle)
Post combustion (4/4)Membranes“A barrier film that allows selective and
specific premeation under conditions appropriate to its function”
Gas permeation membranesDriven force: differences in physical & chemical
interaction,Differences on CO2 partial pressure Absorption membranesDriven force: absorption liquid selectivity
Pre-combustion (1/3)1.The fuel is converted into a mixture mainly of H2 and CO2 CO2 capture from natural gas
Steam reforming - heat supplied from outside the reformer Partial oxidation (incl. Autothermal reforming) – heat is
generated within the reformer
CO2 capture from coal Integrated Gasification Combined Cycle (IGCC),
2. CO2 is captured (usually physical/chemical absorption) CO2 stream (needs compression & dehydration) and a fuel rich in H2 (boilers, furnaces, gas turbines, fuel cells)
Pre-combustion (2/3)CH4 + H2O CO + 3H2
CO + H2O CO2 + H2
heat
Source: Davy technologies
Pre-combustion (3/3)
Source: BBC
Oxyfuel (1/2)Oxygen instead of air during combustion Flue gas mainly consisting of CO2 and H2OPros After the condensation of water high CO2
concentration (80-98%), easy to compress and dry CO2
Dilution of the flue gases because of N2 is avoided
Cons High cost due to the oxygen production in
cryogenic air separation units High temperatures (the flue gas is recirculated
to control the boiler temperature)
Oxyfuel (2/2)
Comparison of capture technologies
Most promising option to be implemented on large scale in the near future taking into account:
operating & maintenance costs cost and ease of retrofitting a power plant development of each technology Absorption separation technology (Notz et al., Aaron et al.)
Major advantages Well established process Low complexity Load flexibilityMain challenge High energy demand for solvent regeneration and CO2 compression –
3.7 GJ/tonCO2 for monoethanolamine (MEA) regeneration
Biphasic solvents as alternative option???
Biphasic solventsAfter CO2 absorption they form two
different phases, one rich in CO2 and one poor in CO2 only the rich phase is regenerated
less energy used for regeneration (MEA as comparison basis)
Biphasic solvents can exhibit:- two liquid phases- liquid and solid phase
Two liquid phases Phase change mixed amine solventsTETA DEEA (Ye et al.,2015) app. 30% energy reductionDEEA MAPA (iCap project) app. 40% energy reduction Thermomorphic biphasic solventsApp. 35% energy reduction (Zhang et al.) DMX solventsApp. 22% energy reduction 3H self-concentrating process50-80% energy reduction (Hu, 2012)
Liquid - solid phases TETA/Ethanol Solutions Phase change amino acid saltsapp. 33% energy reduction Chilled Ammonia
Conclusions Carbon capture processes were
presented Comparison was made Carbon dioxide
capture with absorption, the most promising capture technology to be used in the near future
Biphasic solvents > 30% energy reduction in comparison to simple amines (MEA comparison basis)
Future work Estimation of captured CO2 cost when
using biphasic solvents Comparison with the captured CO2 cost
when using amines Research on problems of using biphasic
solvents & how/if they could be avoided
