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ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Greenhouse gases and ozone-depleting substances • Greenhouse gases and ozone-depleting gases • CO2 removal for gas purification • CO2 removal for greenhouse gas emissions reduction • Other greenhouse gases (CH4, N2O, HFC, PFC, SF6) and ozone-depleting substances see: www.hut.fi/~rzevenho /gasbook www.hut.fi/~rzevenho/
HELSINKI UNIVERSITY OF TECHNOLOGY
The enhanced greenhouse effect
ENE-47.153
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
The enhanced greenhouse effect: sources
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Greenhouse gas emissions distribution from US in 1990 & 1998
GHG compound
US 1998
Carbon dioxide, CO22 Nitrous oxide, N2 O Methane, CH4 Hydrofluorocarbons, HFC Perfluorocarbons, PFC Sulphur hexafluoride, SF66
Global warming % of US GHG % of US GHG potential (GWP) emissions (1990) emissions (1998) 1 ~85 ~ 81 310 ~2.5 ~7 21 ~12 ~ 10 140 - 11700 <1 <1 7400 <1 <1 23900 <1 <1
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
US Greenhouse gas emissions 1998 : 3 most important sources per GHG type CO2 CH4 N22O HFCs, PFCs, SF66
Fossil fuel combustion Fossil fuel combustion industry ~32 % transportation ~30 % Landfills Fermentation ~ 33 % ~ 19 % Agriculture and soil Mobile combustion management ~ 70 % sources ~ 14 % Substution of ozone- HCFC-22 production depleting gases ~ 36 % ~ 27 %
HELSINKI UNIVERSITY OF TECHNOLOGY
Fossil fuel combustion residential ~ 20 % Natural gas systems ~19 % Nitric acid production ~5% Electrical transmission and production ~ 17 %
ENE-47.153
CO2 emissions and thermal process efficiency
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Removal of CO2 from gas streams Chemisorption MEA, DEA, ammonia, hot potassium carbonate Physisorption Selexol, Selexol, Rectisol Adsorbents alumina, alumina, zeolites, zeolites, activated carbon Cryogenic methods Membrane systems Problems with flue gases: SO2 and NOx react with chemical solvents, SO2 is very soluble in physical sorbents
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
Options for CO2 emissions control for fossil fuel - fired power plants Process type Gasification and CO/water-shift Conventional combustion Combustion in O2/CO2 Fuel cells “Hydrocarb” etc.
CO22 emission control method Removal from fuel gas before fuel gas combustion Removal from flue gas Removal of water from flue gas, gives CO2 Removal after fuel reforming or from off-gas Removal of carbon from the fuel before combustion
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Capture of CO2 from flue gases Post-combustion capture
Pre-combustion capture
air comb. : CO2 4 ~ 14 %-vol %-vol,, O2/CO2 comb.: CO2 > 90 %-vol %-vol → Amine solution, Selexol
Oxygen/steam gasification of fuel, CO/water shift, CO2 removal, and H2 combustion in gas turbine
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
Effect of CO2 removal on power plant thermal efficiency and emissions Process Natural gas CC Pulverised coal combustion Coal IGCC
CO2 capture After combustion After CO/shift After combustion After CO/shift
Efficiency (% LHV) CO2 emissions (g/kWh) 56 370 47 60 48 60 46 720 33 150 46 210 38 130
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
Storage of CO2 from flue gases Options considered feasible Deep saline reservoirs Depleted oil/gas fields Enhanced oil recovery Unmineable coal beds Deep ocean storage
Other options Underground caverns Solid dry ice Mineral carbonates *
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
CO2 sequestration by mineral carbonation xMgO.ySiO xMgO.ySiO2.zH2O (s) => x MgO (s) + ySiO2 (s) + z H2O MgO(s) MgO(s) + CO2 <=> MgCO3 (s) Problems : Reaction between MgO and CO2 requires T < 300°C (and high pressures) Very slow reaction Very large amounts of minerals (serpentine, olivine, ...) Worldwide resources of magnesium silicate needed minerals are capable of binding all fossil fuel-bound carbon
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Other greenhouse gases: N2O: see “Nitrogen” CH4: see “VOCs ” “VOCs” thermal /catalytic incineration
unit: pptv = 10-6 ppmv
SF6: sorption in solvent or on carbon bed, incinerate to SO2 and HF HFCs, HFCs, PFCs: PFCs: sorption in solvent or on carbon bed, incinerate to CO2, H2O and HF (similar for CFCs) CFCs)
SF6 and SF5CF3 concentrations in the atmosphere
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
Ozone-depleting substances (ODS) Do not have a direct global warming effect but influence the formation/destruction of tropospheric/ tropospheric/ stratospheric ozone CO, NOx, NOx, non-methane VOCs Class I ODS: ODS: Carbon tetrachloride, methyl chloroform, halons 1950s → (phase-out agreement 1990) : CFCs replaced by non-ODS non-ODS compounds : HFCs, HFCs, PFCs and SF6 Class II ODS: ODS: HCFCs - partially hydrogenated chlorofluoro compounds
HELSINKI UNIVERSITY OF TECHNOLOGY
Greenhouse gases and ozone-depleting substances • Greenhouse gases and ozone-depleting gases • CO2 removal for gas purification • CO2 removal for greenhouse gas emissions reduction • Other greenhouse gases (CH4, N2O, HFC, PFC, SF6) and ozone-depleting substances see: www.hut.fi/~rzevenho /gasbook www.hut.fi/~rzevenho/
HELSINKI UNIVERSITY OF TECHNOLOGY
The enhanced greenhouse effect
ENE-47.153
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
The enhanced greenhouse effect: sources
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Greenhouse gas emissions distribution from US in 1990 & 1998
GHG compound
US 1998
Carbon dioxide, CO22 Nitrous oxide, N2 O Methane, CH4 Hydrofluorocarbons, HFC Perfluorocarbons, PFC Sulphur hexafluoride, SF66
Global warming % of US GHG % of US GHG potential (GWP) emissions (1990) emissions (1998) 1 ~85 ~ 81 310 ~2.5 ~7 21 ~12 ~ 10 140 - 11700 <1 <1 7400 <1 <1 23900 <1 <1
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
US Greenhouse gas emissions 1998 : 3 most important sources per GHG type CO2 CH4 N22O HFCs, PFCs, SF66
Fossil fuel combustion Fossil fuel combustion industry ~32 % transportation ~30 % Landfills Fermentation ~ 33 % ~ 19 % Agriculture and soil Mobile combustion management ~ 70 % sources ~ 14 % Substution of ozone- HCFC-22 production depleting gases ~ 36 % ~ 27 %
HELSINKI UNIVERSITY OF TECHNOLOGY
Fossil fuel combustion residential ~ 20 % Natural gas systems ~19 % Nitric acid production ~5% Electrical transmission and production ~ 17 %
ENE-47.153
CO2 emissions and thermal process efficiency
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Removal of CO2 from gas streams Chemisorption MEA, DEA, ammonia, hot potassium carbonate Physisorption Selexol, Selexol, Rectisol Adsorbents alumina, alumina, zeolites, zeolites, activated carbon Cryogenic methods Membrane systems Problems with flue gases: SO2 and NOx react with chemical solvents, SO2 is very soluble in physical sorbents
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
Options for CO2 emissions control for fossil fuel - fired power plants Process type Gasification and CO/water-shift Conventional combustion Combustion in O2/CO2 Fuel cells “Hydrocarb” etc.
CO22 emission control method Removal from fuel gas before fuel gas combustion Removal from flue gas Removal of water from flue gas, gives CO2 Removal after fuel reforming or from off-gas Removal of carbon from the fuel before combustion
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Capture of CO2 from flue gases Post-combustion capture
Pre-combustion capture
air comb. : CO2 4 ~ 14 %-vol %-vol,, O2/CO2 comb.: CO2 > 90 %-vol %-vol → Amine solution, Selexol
Oxygen/steam gasification of fuel, CO/water shift, CO2 removal, and H2 combustion in gas turbine
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
Effect of CO2 removal on power plant thermal efficiency and emissions Process Natural gas CC Pulverised coal combustion Coal IGCC
CO2 capture After combustion After CO/shift After combustion After CO/shift
Efficiency (% LHV) CO2 emissions (g/kWh) 56 370 47 60 48 60 46 720 33 150 46 210 38 130
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
Storage of CO2 from flue gases Options considered feasible Deep saline reservoirs Depleted oil/gas fields Enhanced oil recovery Unmineable coal beds Deep ocean storage
Other options Underground caverns Solid dry ice Mineral carbonates *
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
CO2 sequestration by mineral carbonation xMgO.ySiO xMgO.ySiO2.zH2O (s) => x MgO (s) + ySiO2 (s) + z H2O MgO(s) MgO(s) + CO2 <=> MgCO3 (s) Problems : Reaction between MgO and CO2 requires T < 300°C (and high pressures) Very slow reaction Very large amounts of minerals (serpentine, olivine, ...) Worldwide resources of magnesium silicate needed minerals are capable of binding all fossil fuel-bound carbon
ENE-47.153
HELSINKI UNIVERSITY OF TECHNOLOGY
Other greenhouse gases: N2O: see “Nitrogen” CH4: see “VOCs ” “VOCs” thermal /catalytic incineration
unit: pptv = 10-6 ppmv
SF6: sorption in solvent or on carbon bed, incinerate to SO2 and HF HFCs, HFCs, PFCs: PFCs: sorption in solvent or on carbon bed, incinerate to CO2, H2O and HF (similar for CFCs) CFCs)
SF6 and SF5CF3 concentrations in the atmosphere
HELSINKI UNIVERSITY OF TECHNOLOGY
ENE-47.153
Ozone-depleting substances (ODS) Do not have a direct global warming effect but influence the formation/destruction of tropospheric/ tropospheric/ stratospheric ozone CO, NOx, NOx, non-methane VOCs Class I ODS: ODS: Carbon tetrachloride, methyl chloroform, halons 1950s → (phase-out agreement 1990) : CFCs replaced by non-ODS non-ODS compounds : HFCs, HFCs, PFCs and SF6 Class II ODS: ODS: HCFCs - partially hydrogenated chlorofluoro compounds
