Carbonation of minerals and industrial residues for CO 2 storage: perspectives of application in energy generation systems

Transcription

1 Carbonation of minerals and industrial residues for CO 2 storage: perspectives of application in energy generation systems 1 R. Baciocchi, 1 G. Costa, 2 M. Mazzotti, 3 A. Polettini, 3 R.Pomi, 2 V. Prigiobbe (1) University of Rome Tor Vergata, Italy (2) ETH, Swiss Federal Institute of Technology, Zurich, Switzerland (3) Sapienza, University of Rome, Italy

2 Outline Fundamentals of mineral carbonation Source of alkaline materials Process routes Mineral carbonation - Dissolution - Precipitation Carbonation of steel slags Conclusions and Challenges

3 Mineral carbonation MO + CO 2 MCO 3 + heat M = Calcium, Magnesium, Iron Issues stability of carbonates availability of alkalinity sources reactivity of alkaline materials

4 Mineral carbonation

5 Sources of metal oxide - Minerals Mg silicates are found in Ophiolite belt complexes US Klamath mountains: 3000 Gt A comprehenisve evaluation of available minerals still missing Olivine: Serpentine: Mg 2 SiO 4 + 2CO 2 2MgCO 3 + SiO2 Mg 3 Si 2 O 5 (OH) 4 + 3CO 2 3MgCO 3 + 2SiO 2 + 2H 2 O Wollastonite: CaSiO 3 + CO 2 CaCO 3 + SiO 2

6 Sources of metal oxide - Residues Steel Industry (60-80 MtCO 2 /y) Energy sector Steel slag AOD process slag Steel converter slag Lignite fly ash APC fly ash MSWI ash PF ash 100s MtCO 2 /y Cement industry Waste cement Cement Kiln Dust

7 Mineral carbonation

8 Mineral carbonation Process routes Gas-solid Single-step Multi-step without chemicals Aqueous Single-step salts with chemicals bicarb. acid / base swing Multi-step (ph swing) P/T swing chelant

9 Mineral carbonation: aqueous route Olivine Dissolution enhancers: -Strong acids, but precipitation difficult - weak acids / ligands, but precipitation possible -CO 2 promising compromise Mg 2 SiO 4 CO 2 MgCO 3 SiO Mg 2(am) 2 SiO CO 2 2 MgCO 3 + SiO 2(am)

10 Mineral carbonation: Experimental set-up Operating conditions Temperature: C CO 2 pressure: bar Particles size: µm ph 2-8 adjusted using P CO2, HCl, and LiOH Addition of NaCl and NaNO 3 Addition of Na 2 C 2 O 4 and Vessel: 300 ml Volume solution: 170 ml Flow rate: 2-10 ml min -1 Mass of olivine: mg Off-line analyses: Si and Fe measurements XRD SEM Na 3 C 3 H 5 O(CO 2 ) 3

11 Dissolution experiments - Olivine Activation energy: 25 C - Pokrovsky und Schott (2000) E A = 52.9 kj/mol Hänchen et al., Geochim. Cosmochim. Acta 70(2006)

12 Dissolution: effect effect of P CO2 and ligands at 120 C H2 C 2 O 4 HC 2 O - 4 C 2 O 2-4 pk 1 = 1.78, pk 2 = 4.95 Prigiobbe et al., CES. (2009), in preparation

13 Precipitation experiments MgCO 3 Magnesite MgCO 3 Barringtonite MgCO 3 2H 2 O Nesquehonite MgCO 3 3H 2 O Lansfordite MgCO 3 5H 2 O Artinite MgCO 3 Mg(OH) 2 3H 2 O Hydromagnesite (MgCO 3 ) 4 Mg(OH) 2 4H 2 O Dypingite (MgCO 3 ) 4 Mg(OH) 2 5H 2 O Initial conditions: Na 2 CO 3 + MgCl 2 solution Hydromagnesite Magnesite Hänchen et al., CES, 62 (2007)

14 Precipitation experiments - Olivine Hydromagnesite / Magnesite precipitation Supersaturation ratio no precipitation --- Hydromagnesite Magnesite Magnesite immediate precipitation T=120 C P(CO 2 )=100 bar Hänchen et al., CES,

15 Carbonation of residues Costa et al., Env. Monit. Ass. 135 (2007)

16 Carbonation of residues Industrial residues are often associated with CO 2 point source emissions They also tend to be more unstable than geologically derived materials They require a lower degree of pre-treatment and less energy intensive conditions Carbonation may also be seen as a stabilisation process The leaching behaviour of alkaline residues may be improved by stabilisation OPC: ordinary Portland Cement PFA: pulvurized fly ash (coal fired power station) GGBS: Ground granulated Blast Furnace Slags MSWI-b: Muncipal Solid Waste Incineration (Bottom ash) MSWI-f: Muncipal Solid Waste Incineration (Fly ash) Costa et al., Env. Monit. Ass. 135 (2007)

17 Carbonation of stainless steel slags SSS investigated: mixture of the slag produced by the EAF and AOD units of a stainless steel manufacturing plant Particle size distribution wt.)100 finer particles (% ,01 0, grain size d (mm) (%) 50 A B D C d< <d< <d< <d<2000 grain size (µm) Sandy granular material with a high % of fines Class A was milled to < 425 µm Baciocchi et al. Envergy Procedia 1(2009

18 Characterization of steel slags Elemental composition: Main constituents (% w/w) A B C D 0 Fe Cr Al Mn Ca Mg CaCO3 Baciocchi et al. Envergy Procedia 1(2009

19 Experimental: carbonation experiments Set up 150 ml stainless steel reactor Thermostatic bath for temperature control 100% CO 2 flow humidified in the reactor with a salt solution 3 g of humidified SSS size fractions treated in each experiment Varied operational conditions Slag humidity (L/S): 0, 0.1, 0.15, 0.2, 0.4, 0.5, 0.6 l/kg Temperature: 30, 40, 50 C PCO 2 : 1, 3, 10 bar Experiment duration: 10, 20, 30, 1, 2, 4, 8, 24 h Evaluation of the CO 2 storage capacity of the residues Calcimetry analysis Effects of carbonation on material properties XRD analysis Leaching tests: EN and CEN

20 Results: carbonation tests Effect of L/S Effect of grain size CO2up ptake (%) CO2up ptake (%) unmilled milled L/S (l/kg) Class D, t = 2 h, T = 30 ⁰C and P = 3 bar maximum particle size (µm) t = 2 h, T = 50 ⁰C P = 3 bar and L/S = 0.4 l/kg Baciocchi et al. Envergy Procedia 1(2009

21 Results: carbonation kinetics AOD residues only CO2 (%) P=1 bar P=3 bar P=10 bar t (ore) Increased CO 2 uptake due to the high reactivity of dicalcium silicate (C 2 S).

22 Results: effect on mineralogy MgO MgCr 2 O 4 Ca 12 Al 114 Fe 0.14 O 32 Ca 2 SiO 4 carbonated CaCO 3 CaMg(CO 3 ) θ( ) untreated Disappearance of MgOand MgCr 2 O 4 Significant reduction of Ca 12 Al 114 Fe 0.14 O 3 Decrease of Ca 2 SiO 4 Increase of CaCO 3 classd, carbonatedfor2 h at 50 ⁰C, P = 3 bar and L/S = 0.4 l/kg Baciocchi et al. Envergy Procedia 1(2009

23 Results: effects on metal leaching Landfill leaching compliance test (EN ) 2) in mg/l A B untreated carbonated untreated carbonated untreated carbonated untreated carbonated ph Ca Cr Fe Mg Si Critical parametersfor untreated SSS inert landfill disposal and reuse: ph > 12 and Cr > 0.05 mg/l ph decrease for all fractions, more pronounced for class D Cr no significant effect (some reduction for B and C) C Significant Ca decrease and Si release in the eluate D Baciocchi et al. Envergy Procedia 1(2009

24 Conclusions Pro - CO 2 stored in a safe and definitive manner - CO 2 storage potential basically unlimited - It can be done with existing technologies - Ca-silicates/Residues carbonation at relatively mild conditions - Industrial residues are a start-up option Cons - Energy penalty and associated costs still too high - Mg-silicates carbonation needs energy intensive pre-treatment - Many process issues still unresolved and needing optimization - Lack of demonstration units (pilot-scale)