High Capcity Hydrotalcites

Transcription

1 High Capcity Hydrotalcites for CO 2 capture technologies

2 High Capacity Hydrotalcites P.D. Cobden S. Walspurger W.H. Haije R.W. Van den Brink E.J. Anthony Y. Wu O. Safonova

3 Outline Pre-combustion decarbonisation - SEWGS Sorbents for SEWGS - Promoted Hydrotalcites Scale-up - New Conditions = New Processes Conclusions

4 Outline CO 2 interaction with Potassium-promoted Magnesium-Aluminium Hydrotalcites changes as a function of steam pressure Below 2 bar steam pressure CO 2 adsorption is dominant process Above 4 bar steam pressure, CO 2 interaction dominated by new mechanism: full MgCO 3 formation achieved Surface Process Bulk Process

5 Pre-combustion Syngas Production for Power Production 400 C HTS 30 C Natural gas CH 4, LTS 20 C Reforming Shift H 2 /CO C separation 900 C H 2 CO2 30 bar C (gas turbine)

6 Pre-combustion Syngas Production for Power Production HTS Natural gas CH 4, LTS Reforming Shift H 2 /CO 2 separation H 2 CO2 30 bar C (gas turbine) Can we combine traditionally separate unit operations? Aim: Produce Hot H 2 at pressure, avoiding many temperature transitions Process: Sorption-Enhanced Water-Gas Shift

7 Sorption Enhanced Water Gas Shift (SEWGS) Concept Feed step syngas 57% H 2 16% H 2 O 16% CO 10% CO 2 0.5% CH 4 CO + H 2 O CO 2 + H 2 adsorbent adsorbent and catalyst 90% C removal decarbonised fuel gas 87% H 2 8% H 2 O 0.5% CO 2% CO 2 0.5% CH 4 Water gas shift catalyst + high temperature CO 2 adsorbent Removes CO 2 from hot syngas ( C), drives CO towards extinction Multiple beds undergo cyclic process steps (reaction/adsorption and regeneration)

8 Lab-scale SEWGS 6 5 Point of Break-Through CO 2 Concentration [%] % CO conversion 50% CO conversion CO Time [min]

9 SEWGS

10 Hydrotalcites Al(OH) 6 -octahedron Mg(OH) 6 -octahedron H 2 O CO 3 2- Promoted with K 2 CO 3 K20-Mg70, standard Mg:Al ratio 1:3, 20wt% K 2 CO

11 Hydrotalcites at 400 C 373K 573K 673K Kim N., Kim Y., Tsotsis T.T. and Sahami M., J. Chem. Phys. 2005; 122:

12 Hydrotalcites: K-Mg-Al-O + CO rt x1 100 x1 200 x2 300 x5 400 x5 600 x MgCO 3 1 bar CO 2 Relative counts (au) θ

13 K-Promoted Layered Double Hydroxides Li-Al Flow CO 2 [ml/min] Mg-Mn Mg-Al Mg-Al-Zr Elapsed time [min]

14 Spectroscopic investigations: towards the active species potassium carbonate promoted gamma alumina: e) Al O C O O K d) Kubelka Munk Intensity (a.u.) 1655 c) b) a) Non symmetric carbonate species formed (a) RT (b) 100 o C (c) 200 o C (+ H 2 O) (d) 300 o C (+ H 2 O) (e) 400 o C (+ H 2 O) Wave number (cm -1 ) Walspurger S., Boels L., Cobden P.D., Elzinga G.D., Haije W.G. and van den Brink R.W., ChemSusChem 2008; 1:

15 Breakthrough Tests 6 bar CO 2 6 bar H 2 O Breakthrough test repeated after 5 weeks of commissioning and testing, slight increase in capacity

16 High Capacity & Chemical Stability 1.0 ~1.5 mmol/g % y CO 2,out / y CO 2,in >8 mmol/g 60% 6 bar CO bar Time [min]

17 High Pressure TGA 2.50 Capacity [mmol/g] Wet Capacity kmg70 [mmol/g] Calc Wet Cap kmg70 Dry Capacity kmg70 [mmol/g] Calc Dry Cap kmg70 Wet = 1.5 bar H 2 O pco2 [bar]

18 High Pressure Loading

19 High Pressure Loading - Method Add H 2 O Flush with CO 2 Bring to pressure in CO 2 21 ml 5 mins 12 bar Increase temperature 350 C Hold 2 hours Release pressure Flush with CO 2 Release pressure Cool quickly total pressure ~ 40 bar 15 bar 12 bar ambient down to ambient ~ 5 mins

20 Decomposition Loaded Hydrotalcites 18.0 Mass Loss [mmol/g (equiv. CO 2 )] Temperature [ºC] Mg70 k2mg70 k5mg70 k11mg

21 Decomposition Loaded Hydrotalcite 25 Mass Loss [mmol/g (equiv. CO2)] K0-Mg70 K11-Mg70 MgO K0-Mg70 K11-Mg70 MgO Material

22 Fully Loaded Hydrotalcite Lin (Cps) Theta - Scale File: KII Mg 70 - treated.raw - Type: 2Th/Th locked - Start: End: Step: Step time: 2. s (I) - Magnesite, syn - MgCO3 - Rhombo.H.axes - a b c alpha beta gamma Primitive - R-3c (167)

23 Decomposition Loaded Hydrotalcite Counts (au) decomposed (bis) 500 decomposed x 10 x θ

24 In-situ Loading Hydrotalcite Connection metal-capillary ensured by high temperature epoxy resin (glue) Tracing of the pipes and cell ensure a homogeneous temperature of 200 C Gas inlet Gas outlet Sample in a quartz capillary of 1mm diameter Hot air blower Temperature up to 600 C Length of the capillary about 25 mm

25 In-situ Loading Hydrotalcite Counts Dry CO2 1 to 3.1 bar Dry CO2 3.2 to 4.5 bar Dry CO2 4.8 to 5.8 bar Steam_CO2 6 bar Steam_CO2 7.4 to 8.4 bar Steam_CO2 9.6 to 10 bar Steam_CO2 10 bar (t=10 min) Steam_CO2 10 bar (t=20 min) Steam_CO2 10 bar (t=30 min) θ

26 In-situ Loading Hydrotalcite bar steam CO2 (t=35min) 2000 Counts θ

27 In-situ Loading Hydrotalcite 200_DRYCO2_10Bar 200_steamCO2_10bar 300_steamCO2_10bar 400_steamCO2_10bar 500_steamCO2_10bar 400_cool_steam Counts θ

28 Chemical Stability 0.5 average CO 2 in product gas during feed step [%] cycle number E.R. van Selow, P.D. Cobden, R.W. van den Brink, J.R. Hufton and A. Wright, proceedings GHGT

29 Mechanical Stability Hydrotalcite is a soft clay - Higher calcination temperature degrades performance MgO 89 mmol/cm 3 MgCO 3 35 mmol/cm

30 Conclusions Below 2 bar steam pressure CO 2 adsorption is dominant process, K-Al-CO 3 centres Above 4 bar steam pressure, CO 2 interaction dominated by new mechanism: full MgCO 3 formation achieved (K required) Surface Process Bulk Process Full loading of MgO can also be achieved, even without K

31 High Capacity Hydrotalcites P.D. Cobden S. Walspurger W.H. Haije R.W. Van den Brink E.J. Anthony Y. Wu O. Safonova