CO 2 -fangst: Separasjonsmetoder,

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1 CO -fangst: Separasjonsmetoder, energiforbruk og teknologier NORGES TEKNISK-NATURVITENSKAPELIGE UNIVERSITET NTNU CO -håndtering - er vi i rute? Kursdagene, 8. januar C+ O CO How and why is CO formed 1 Formation reaction of CO Q + H = H r r Q+ nh = n h h p is enthalpy i i e e p Assuming that both reactants and products are each at a o total pressure of 1 bar and 5 C, and that we assign the value o of zero of all elements at 1 bar and 5 C, Q= Hp = MJ/kmol CO This is the enthalpy of formation (dannelsesentalpi) of CO

2 Enthalpy of formation, dannelsesentalpi l Molecular weight Symbol Name kj/mol k/k kg/kmol MJ/kg C Carbon (graphite) O Oxygen H Hydrogen CH 4 Methane C H 6 Ethane CO Carbon monoxide CH 3 OH Methanol H O (gas) Water (steam) H O (liquid) Water SiO Silicon dioxide CO Carbon dioxide CaO Calcium oxide MgCO 3 Magnesium carbonate CaCO 3 Calcium carbonate Mg SiO 4 Olivine g 4 3 How and why is CO formed Combustion of Methane CH + O CO + H O 4 Q+ nh = n h r i i e e p nh i i= r ne h e= gas= p Q = = kj/kmol CH 4 Q = kj/kmol CH4 = kj/kg CH4 Q is here the Lower Heating Value of CH 4 4

3 How and why is CO formed 3 Combustion of Methane Carbon as comb product CH + O C + H O 4 k/k i i Q = = kj/kmol e e Q+ nh = n h r p r nh i i nh p = = e e gas Q = kj/kmol CH Combustion of CH of formation of CH = 5480 kj/kg CH with formation of solid C ("carbon black") reduces the heat to 51% of the LHV. CH 4 4 CO must be formed in order to release the full heat of combustion for a carbon containing fuel for a given fuel, the amount of formed CO is proportional with the chemical energy being converted to heat 5 Converting CO to other carbon-containing substances (1 bar, 5 C) Chemical reaction Heat of reaction [kj/mol CO ] Heat of reaction [MJ/kg CO ] State of C CO C + O Solid 1 CO CO + O Gas CO + H O( gas) C H4 + O Gas CO + H CH3OH + HO Liquid 1 1 CO + Mg SiO4 MgCO3 + SiO Solid CO + CaO CaCO Solid 3 6

4 Fuel characteristics for CO -emission Fossil fuels consists of the combustible components Carbon (C) and Hydrogen (H) Methane: C H 1 4 The ratio between carbon and hydrogen gives the amount of CO C H m n n + + O m CO + H O m n 4 m m m > n > n n coal oil natural gas ( ) ( ) ( ) 11. > 05. > 05. coal oil natural gas 7 Emission of CO from fossil fuels per kwhe k am CO n of gr Emissio 1300 Methane (H/C=4) 100 Distillate oil (H/C=) 1100 Lignite (brown coal) 1000 Bituminous coal 900 Anthrasit Efficiency [%] 8

5 Why is the partial pressure of CO in exhaust gas so low Reactants Products exhaust flue gas Excess air n CmHn +Φ m + ( O N) 4 n n n mco + HO + ( Φ 1) m + O + Φ m N 4 4 Gas turbine fired with natural gas: Φ=.-3 Exhaust: volume-% CO Coal fired plant: Φ 1. Exhaust: volume-% CO Gases has to be separated CO partial pressure 10 Partial pressu ure CO [bar] Gas turbines Oil fired boilers Coal fired boilers Cement kiln off-gas Blast IGCC furnace gas syngas without ih shift Natural gas processing Ammonia production IGCC syngas with ihshift 10

6 1000 Phase diagram CO Melting/freezing 100 Solid Liquid Transport & Storage condition [bar] Pressure 10 Boiling/condensation Critical point 5.18 bar Vapour C Pre-combustion syngas Triple point 1 Sublimationn Sublimation point Oxy-combustion Post-combustion Gas Technology Centre Temperature NTNU SINTEF [ C] 11 sity [kg/m 3 ] Dens Density CO 0. bar bar 3 bar 10 bar bar bar 100 bar 150 bar Temperature [ C] 1

7 1000 Distillation Melting/freezing 100 Solid Liquid Transport & Storage condition [bar] Pressure bar C Triple point Boiling/condensation Vapour Critical point 1 Sublimationn Sublimation point Flue gas must be compressed and cooled, P /P 1 depends on CO partial pressure /0.015= =345 bar (1.5% CO ) Gas Technology Centre Temperature NTNU SINTEF [ C] Anti-sublimation Melting/freezing 100 Solid Liquid Transport & Storage condition [bar] Pressure bar C Triple point Boiling/condensation Vapour Critical point 1 Sublimationn Sublimation point Flue gas must be cooled, How low T depends on CO partial pressure Gas Technology Centre Temperature NTNU SINTEF [ C] 14

8 Pressure [bar] Gas-phase separation Melting/freezing Solid Liquid Boiling/condensation Transport & Storage condition Cooling Critical point 5.18 bar Vapour C Cooling Triple point 1 Sublimationn Sublimation point Absorption Adsorption Oxy-combustion Membrane Sorbents Gas Technology Centre Temperature NTNU SINTEF [ C] 15 CO quality requirements Canyon Reef Weyburn Esbjerg NETL Component EOR EOR EOR CO > 95% 96% 99,50 % - CO - 01% 0,1 <10ppmv - H O Water vapour No free water. < 0,489 m -3 content in the <0 ppmv equivalent to vapour phase saturation at -5 C 5C 33 K dew point H S < 1500 ppm (weight) 0,9 % - - SO - - < 10 ppmv - Total sulfur < 1450 ppm (weight) % <300 ppmv <048% 0.48 <300 ppmv NO X - - < 50 ppmv - O < 10 ppm (weight) <50 ppmv < 10 ppmv < 40 ppmv Glycol 4x10-5 Litre/m CH % - - C % - - Hydrocarbon < 5% ppmv - Temperature ( C) < 10 F (48.9 C) - - Pressure (MPa)

9 Work requirement for CO capture 17 Minimum work for gas separation atm wall 1 atm 1 atm N CO CO N N CO CO Mixing N CO CO N CO CO CO CO CO Mixing: The gases are mixed; the gases are expanded iso-thermally from 1 atm to their partial pressure in the mixture p = P i y i partial pressure of gas i = total pressure volume fraction gas i 18

10 Minimum work for gas separation - 1 atm wall 1 atm 1 atm N CO CO N CO CO Separation N CO CO N CO CO CO CO CO The exergy lost by mixing, represents the minimum work requirement for separation, wrev W rev i V i = V pdv i [ J] Pamb J wrev = T0Ru yi ln = T0Ru yi ln yi i p i i mol This can also be looked upon as the work of iso-thermal compression of the gas components i from their partial pressure to the ambient pressure 19 Reduction in efficiency when capturing CO Reduction in eff ficiency [%-points] 5.00 % 4.50 % Coal Oil 4.00 % Natural gas 3.50 % 3.00 %.50 %.00 % 1.50 % 1.00 % Minimum reduction in efficiency 1.3% 0.50 % 0.00 % Volume fraction/partial pressure of CO [bar] Example: CO capture from gas turbine flue gas, y CO =3.6% with MEA absorption/stripper system for CO capture Without CO capture 58% CO capture penalty -8.8% MJ/kg CO Δefficiency With CO capture 49.% Fans, pumps, auxiliary % Heat for stripping (3.6MJ heat/kg CO ) % Additional fuel consumption: 58/49.-1=18% Sum for atmospheric CO 6.75% Ratio real/theoretical minimum 5. CO compression %.04 Sum total 8.79 % 0

11 CO capture the methods for power plants Coa al, Oil, Natu ural Gas, B iomass Power plant Gasification Reforming Post-combustion CO/H₂ Shift CO/H₂ N₂/O₂ CO₂ separation CO₂ H₂ CO₂₂ H₂ CO₂ separation Pre-combustion O₂ Power plant separation CO₂ Power plant CO₂ Oxy-combustion N₂ N₂/O₂ CO₂ compression & conditioning 1 Post-combustion Low-medium CO partial pressure Medium-high CO Medium-high CO partial pressure partial pressure

12 Absorption Combined Cycle flue gas 3 SARGAS cycle post-combustion capture at elevated pressure Non-adiabatic combustion, less excess O Benfield/K CO 3 Membranes 4

13 Membranes Feed gas A, B Rt Retentate tt gas A, B p f,b Support Membrane wall, permeant Permeate gas C, B, A t m p p,b B, A Sweep gas C Permeability description of gas flux through the membrane Selectivity which gases are transported q P J = = p p ( p, p, ) 3 m (STP) J i is the flux, m h 3 pi, m(stp) q p,i volumetric flow rate, h i f i p i A Am t m the membrane surface area, m m t m the membrane thickness, m 3 m(stp) P is the permeability, mhbar P 3 m (STP) is the permeance, tm m h bar p f and p p (p f > p p ) are the partial pressures of the permeated gas at the feed and permeate sides, Gas Technology Centre respectively, NTNU SINTEF bar. 5 Pre-combustion CO capture 6

14 Pre-combustion - principle Split the C x H y -molecules into H and CO Transfer heating value from C x H y to H Separate CO from H Coal Oil Natural gas Gasifier Reformer H CO Shift H CO CO capture H to combustion Oxidizer H O CO O 7 IGCC without CO capture Integrated Gasification Combined Cycle Quench water Recovered heat Quench/ heat recovery Particulate removal Sulfur removal H S Raw syngas Coal feed Gasifier O Hydrogen-rich gas Separation Unit Compressed air HRSG Recovered heat Gas turbine ST G 8

15 Solid fuel gasifier Pressurized water inlet Fuel Oxygen, steam Pressurized water outlet Burner Siemens SFG gasifier Cooling screen Quench water Cooling jacket Gas outlet t Granulated slag 9 IGCC with CO capture Integrated Gasification Combined Cycle Quench water Recovered heat Quench/ heat recovery Raw syngas Particulate removal Steam Shift reaction Selexol l Sulfur Rectisol removal Fluor Solvent H S CO capture CO Coal feed O Gasifier Hydrogen-rich gas CO storageg Separation Unit Compressed air HRSG Recovered heat Gas turbine ST G 30

16 IGCC with CO capture Integrated Gasification Combined Cycle Quench water Recovered heat Quench/ heat recovery Particulate removal Shift reaction Sulfur removal H S CO capture CO Raw syngas Steam Coal feed O Separation Unit Gasifier Compressed air Hydrogen-rich gas TIT reduction HRSG Recovered heat CO storageg Gas turbine ST Fuel dilution G 31 Oxy-combustion CO capture 3

17 Oxy-combustion Reactants Products exhaust flue gas excess ratio n CmHn +Φ m + ( O N) 4 n n n mco + HO + ( Φ 1) m + O + Φ m N % CH4 + O CO + H O Combustion without the nitrogen in the air Zero excess oxygen 1 kg methane requires 4 kg oxygen 33 Oxy-combustion the principle i for the power cycle CO and/or H O recycle - liquid or gas hydrocarbon C,H O Separation Unit Conversion system Flue gas CO + H O CO to storage H O extraction 34

18 Oxy-combustion - air separation Separation Technologies Membrane Cryogenic distillation Adsorption o Polymeric Ceramic Pressure Swing Vacuum Swing Vacuum Pressure membrane membrane Adsorption Adsorption Swing Adsorption (PSA) (VSA) (VPSA) Electrically driven membrane Partial pressure driven membrane 35 Dilution of CO Oxy-combustion H O; 14.3 % ; 3. % H O; 16.9 % SO ; 0.3 % ; 13.5 % Ar; 4.8 % O ; 0%.0 Ar; 1.9 % O ; 4.9 % CO ; 75.7 % Oxy-combustion natural gas Oxy-combustion coal CO ; 6.5 % Pressure 1 atm CO partial pressure atm 36

19 Oxy-combustion coal 30 MW thermal Schwarze Pumpe Commissioning Sept 9, 008 Vattenfall Germany 37 Oxy-combustion catalyst Mixed conducting membrane N Oxygen mixed conduction membrane CH 4 e - CO H O - O T= C Source: Sven Gunnar Sundkvist, Oct. 003 Gas turbine process + steam turbine process The GT combustor is replaced with a mixed conductive membrane reactor (MCM) Separation of O from air by the membrane Combustion of fuel Gas without Technology presence Centre of NTNU SINTEF Heat exchange (combustion heat to oxygen depleted air) 38

20 Chemical Looping Combustion C Fuel Metal Metal oxidation T Metal oxide Metal oxide reduction CO +HO T Oxygen depleted air 14% O Cooling CO and H O condensation Compression and storage H O CH Reduction 4( g) + 4MeO(s) CO ( g) + H O(g) + 4Me(s) Oxidation Me(s) + 1/ O( g) MeO( s) MeO=NiO supported on NiAl O 4 Other alternatives: Cu, Fe, Mg 39 Conclusions No clear winner among the technologies (still) The will to build demo plants moves many towards post-combustion methods Retrofit, post-combustion most likely Combined CO and SO capture for retrofit Large addition of engineering knowledge has been added in last 3 years Oxygen ion transport membranes Efficiency potential Very challenging Coal: Pre-,,p post, oxy-combustion? Environmental impact of emissions of chemicals to air needs proper attention 40

21 Takk! TCCS-5 5 th Trondheim Conference on CCS 41