1. The use of alkaline industrial waste in the capture of carbon dioxide
J. Jaschik, M. Jaschik, K. Warmuzinski
Institute of Chemical Engineering
Polish Academy of Sciences
Gliwice, Poland
7th International Scientific Conference on Energy and Climate Change
Athens, 8-10 October 2014

2. Mineral carbonation One of a number of options for the capture of CO2
The fixation of CO2 in the form of inorganic, insoluble carbonates, based on the exothermic (spontaneous) reaction of CO2 with metal oxide-bearing materials:
MO + CO2 → MCO3 + heat
Source of metal oxides:
naturally occurring silicate rocks (serpentine, olivine, wollastonite, talc)
alkaline industrial residues (fly ash, stainless steel slag, oil shale ash, cement, concrete, MSWI - municipal solid waste incinerator - residue) 2
7th International Scientific Conference on Energy and Climate Change
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3. Advantages: Disadvantages: 1. permanent and safe binding of CO2
2. geologically stable and environmentally neutral carbonates may be stored for long periods of time
3. products of mineral carbonation may be reused
Mineral carbonation (IPCC Special Report on Carbon Dioxide Capture and Storage)
Disadvantages:
1. slow kinetics of carbonation processes
2. large amounts of minerals required
3. cost 3
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4. cement, concrete, residue2 steel slag, concrete waste3
Costs of storage per tonne of CO2 avoided
Geological storage1
0.5 – 8 US$/tCO2
Ocean storage1
5 – 30 US$/tCO2
Mineral carbonation:
natural minerals1
cement, concrete, residue2
steel slag, concrete waste3
50 – 100 US$/tCO2
22 – 35 US$/t CO2
8 US$/t CO2
IPCC Special Report on Carbon Dioxide Capture and Storage, Cambridge University Press, Cambridge, 2005
W.J.J. Huijgen, R.N.J. Comans: Mineral CO2 sequestration by carbonation of industrial residues. Literature overview and selection of residue, Report ECN-C-05-74, December 2005
Stolaroff J.K., Lowry G.V., Keith D.W.: Using CaO- and MgO-rich industrial waste streams for carbon sequestration, Energy Conversion and Management, 46 (2005), 4
7th International Scientific Conference on Energy and Climate Change
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Geological storage1
0.5 – 8 $/t CO2
Ocean storage1
5 – 30 $/t CO2
Mineral carbonation:
natural minerals1
cement, concrete residue2
steel slag, concrete waste3
$/t CO2
22 – 35 $/t CO2
8 $/t CO2
Geological storage1
0.5 – 8 $/t CO2
Ocean storage1
5 – 30 $/t CO2
Mineral carbonation:
natural minerals1
cement, concrete residue2
steel slag, concrete waste3
$/t CO2
22 – 35 $/t CO2
8 $/t CO2

5. Utilization of fly ash (+) Lower cost of carbonation due to:
pulverized form of fly ash, which does not require additional mechanical processing
availability close to CO2 source; fly ash does not have to be mined and transported
no need for thermal processing
(+) Faster kinetics of carbonation; main reactive species are CaO and Ca(OH)2
(+) Environmental and commercial advantages:
stabilization of alkaline waste material (leaching of potientially harmful elements from the residue decreases due to carbonation)
by-product with high commercial value 5
7th International Scientific Conference on Energy and Climate Change
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6. Ash Slag Total coal lignite
4. (-) Limited storage capacity
Production of ashes and slags
from power stations in Poland (Mt/year)
Ash
Slag
Total
coal
lignite
2000
7.718
5.647
1.719
0.145
15.229
2004
7.141
6.317
2.074
0.165
15.697
2008
7.080
6.339
1.337
14.756
2011
8.260
7.416
1.718
17.394
2012
19.052
2.398
21.450 6
7th International Scientific Conference on Energy and Climate Change
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7. Generation of combustion by-products in Europe in 2008
Bottom ash 8.6%
Slag 2.4%
Fluidized ash 1.8%
Ash with
desulphurization
products 0.6%
Gypsum
20%
Fly ash
66.6%
Total: about 100 Mt 7
7th International Scientific Conference on Energy and Climate Change
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8. Process routes for aqueous carbonation
1. Direct carbonation
Off-gas
Liquid phase
Minerals/Waste
Water
Solid product
Flue gas
2. Indirect carbonation
Off-gas
Liquid phase
Minerals/Waste
Water
Solid product
PCC
Solid product
Flue gas 8
7th International Scientific Conference on Energy and Climate Change
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9. Reaction mechanism Extraction/Dissolution CaO (s) + H2O ↔ Ca(OH)2 (s)
Ca(OH)2 (s) ↔ Ca+2 + 2OH- (solid surface) ↔ Ca+2 + 2OH- (bulk solution)
Ca/Mg-silicate (s) + 2H+ ↔ Ca/Mg+2 + SiO2 (s) + H2O
Availability of lime to hydration and carbonation reactions is of key importance
solution composition
specific surface area
Extraction of Ca/Mg ions from mineral matrix is strongly affected by acids 9
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10. Reaction and Precipitation
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- ↔ 2H+ + CO3-2
Ca+2 + HCO3- ↔ H+ + CaCO3 (s)
Mg+2 + HCO3- ↔ H+ + MgCO3 (s)
Ca+2 + CO3-2 ↔ CaCO3 (s)
Mg+2 + CO3-2 ↔ MgCO3 (s)
Ca+2 + SO4-2 ↔ CaSO4 (s)
Sulphate ions, alongside the carbonation ions, produce insoluble layers of CaSO4 and CaCO3 which coat the surface of ash particles, thus preventing further dissolution of calcium oxide
The coating of precipitated solids building on ash particles makes the recycling of unconverted feedstock impossible 10
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11. Characteristics of ash studied
Fly ash from lignite fluidized bed combustion (Turow power station)
t = 760°C
η = 91%
Production and emission in 2013:
Energy – 45,965,390 GJ
Heat – 650,821 GJ
Fly ash – 1,043 Mg
SO2 – 21,416 Mg
NO2 – 9,180 Mg
CO – 727 Mg
CO2 – 9,994,790 Mg 11
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12. Chemical composition wt. % FBC ash PF ash PFD ash SiO2 27.0 50.8 42.8
CaO
29.1
2.97
13.9
MgO
2.02
2.52
2.18
Al2O3
20.2
25.2
21.0
Fe2O3
4.54
6.08
5.15
Na2O
1.27
1.06
0.93
K2O
1.01
3.35
2.64
SO3
8.75
0.32
2.94
P2O5
0.2
0.74
0.53
CaO free
12.0
1.7
0.4 12
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13. Phase composition wt. % FBC ash PF ash PFD ash Lime CaO 12.0 0.4 1.7
Portlandite Ca(OH)2
0.2 -
0.5
Periclase MgO
1.0
0.9
Anhydrite CaSO4
12.4
3.5
Calcite CaCO3
6.4
2.7
Albite NaAlSi3O8
1.5
Mullite 3Al2O3·2SiO2
12.9
8.8
Anorthite CaAl2Si2O8
Quartz SiO2
1.9
6.9
5.3
Amorphous
63.0
76.8
73.1 13
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14. FBC ash (fly ash from lignite fluidized bed combustion)
Morphology
FBC ash (fly ash from lignite fluidized bed combustion)
Irregular shape
Porous and uneven surface
PF ash (fly ash from pulverized coal fired boilers)
Regular spherical shape
Smooth surface 14
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15. Particle size distribution
Dv(0.1) = 5.61 μm
Dv(0.5) = μm
Dv(0.9) = μm
D[3,2] = μm
D[3,4] = μm
Surface and porosity
BET = m2/g
Micropore area = m2/g
Total pore volume = 3.71 mm3/g
Micropore volume = mm3/g
Average pore size = nm 15
7th International Scientific Conference on Energy and Climate Change
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Particle size distribution:
Dv(0.1) = μm
Dv(0.5) = μm
Dv(0.9) = μm
BET = m2/g
Particle size distribution:
Dv(0.1) = μm
Dv(0.5) = μm
Dv(0.9) = μm
BET = m2/g

16. Experimental Parameters of dissolution Temperature 20-80 ºC
Ash/water ratio /4 – 1/100
Stirrer speed min-1
Time of dissolution about 5 hours
Experimental setup 1 – reactor, 2 – heating jacket, 3 – inlet of solution and solid phase, 4 – cooler, 5 – peristaltic pump, 6 – sample withdrawal, 7 – mixer, T – temperature control, N – mixer speed control 16
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17. Principal objectives of the study
Determination of the potential of fly ash from lignite fluidized bed combustion to capture carbon dioxide via mineral carbonation
Determination of the optimum parameters for the process of dissolution of solid alkaline waste, which is a crucial step in the enhanced CO2 carbonation 17
7th International Scientific Conference on Energy and Climate Change
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18. ↕ Effect of stirrer speed t = 20°C, ash/water ratio = 1:50, 1:20 18
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19. ↓ Effect of temperature
Stirrer speed = 600 min-1, ash/water ratio = 1:20 ↓ 19
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20. ↑ Effect of ash to water ratio Stirrer speed = 600 min-1, t = 20°C 20
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21. Proposed scheme of indirect carbonation
Step 1
Reactive species are extracted from the ash
Step 2
Reaction with CO2 and precipitation of carbonates take place 21
7th International Scientific Conference on Energy and Climate Change
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22. Conclusions
The results obtained clearly show that the fly ash studied can be employed in the mineral carbonation of CO2. The high content of calcium oxide and the considerable proportion of the reactive form of CaO compared with the total calcium content lead, over a short period of time, to a solution saturated with calcium ions
The solution, despite the presence of considerable amounts of calcium sulphate in the fly ash, still remains alkaline (pH of about 12.5). Therefore, the next step of carbonation in the presence of carbon dioxide should occur with relatively high yield
The content of sulphate and carbonate ions in the liquid phase has to be closely monitored, as they lead to the formation of insoluble layers on the surface of particles and thereby strongly inhibit the dissolution
The indirect route is proposed for the future study of aqueous carbonation process using ash from lignite fluidized bed combustion 22
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23. THANK YOU FOR YOUR ATTENTION
7th International Scientific Conference on Energy and Climate Change
Athens, 8-10 October 2014