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

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 Athens, 8-10 October 2014

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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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), 687-699 4 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014 Geological storage1 0.5 – 8 $/t CO2 Ocean storage1 5 – 30 $/t CO2 Mineral carbonation: natural minerals1 cement, concrete residue2 steel slag, concrete waste3 50-100 $/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 50-100 $/t CO2 22 – 35 $/t CO2 8 $/t CO2

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 Athens, 8-10 October 2014

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 Athens, 8-10 October 2014

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 Athens, 8-10 October 2014

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 Athens, 8-10 October 2014

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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

Particle size distribution Dv(0.1) = 5.61 μm Dv(0.5) = 32.86 μm Dv(0.9) = 130.71 μm D[3,2] = 11.81 μm D[3,4] = 62.31 μm Surface and porosity BET = 6.664 m2/g Micropore area = 0.588 m2/g Total pore volume = 3.71 mm3/g Micropore volume = 0.026 mm3/g Average pore size = 14.24 nm 15 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014 Particle size distribution: Dv(0.1) = 5.611 μm Dv(0.5) = 32.856 μm Dv(0.9) = 130.714 μm BET = 6.664 m2/g Particle size distribution: Dv(0.1) = 5.611 μm Dv(0.5) = 32.856 μm Dv(0.9) = 130.714 μm BET = 6.664 m2/g

Experimental Parameters of dissolution Temperature 20-80 ºC Ash/water ratio 1/4 – 1/100 Stirrer speed 300-1100 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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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 Athens, 8-10 October 2014

↕ Effect of stirrer speed t = 20°C, ash/water ratio = 1:50, 1:20 18 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

↓ Effect of temperature Stirrer speed = 600 min-1, ash/water ratio = 1:20 ↓ 19 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

↑ Effect of ash to water ratio Stirrer speed = 600 min-1, t = 20°C 20 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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 Athens, 8-10 October 2014

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 7th International Scientific Conference on Energy and Climate Change Athens, 8-10 October 2014

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