AUTHORS: C. Gómez-Giménez E. García-Díez D. Ballestero R. Juan B. Rubio M.T. Izquierdo INSTITUTIONS:

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1 AUTHORS: C. Gómez-Giménez E. García-Díez D. Ballestero R. Juan B. Rubio M.T. Izquierdo INSTITUTIONS: FUNDING: Ponferrada, September 12 th 2013

2 Total emitted in 2009: 73.4 t Spain: 10.9% 109% Source: European Union emission inventory report under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP) EEA, Copenhagen,

3 Source: Control of Mercury Emissions from Coal-Fired Electric Utility Boilers, Air Pollution Prevention and Control Division, National Risk Management Research Laboratory Office of Research and Development, US EPA, Research Triangle Park, NC, EPA-600/R , December 2001

4 Hg 0 Hg 0 Hg 2+ Hg p Hg 0 Hg 2+ Hg p Hg0 Hg 2+ Hg 2+ Hgp Hg 0 Hg 2+ Source: Electric Power Reseach Institute, EPRI

5 CONVENTIONAL BOILER OXYFUEL BOILER

6 150 ºC 50 ºC Source: Hitachi Gold based sorbent in a fixed-bed Fixed adsorption structures

7 Development of low content-au novel mercury regenerable sorbent based on Au nanoparticles deposited on a honeycomb carbon monolith. Evaluation of sorbents for mercury capture under O 2 /CO 2 atmospheres Influence of temperature Influence of flue gas composition Evaluation of regeneration: capture-regeneration cycles

8 IMPREGNATION & CURE Phenolic resin impregnation into cordierite honeycomb and thermal cure at 150 ºC CARBONIZATION 700 ºC, Ar Monolith with square channel with a density 16 cell/cm 2 GOLD DEPOSITION HAuCl 4 3H 2 O Solution in ethanol/water (1:1 v/v) Take advantage of the reducing capacity of carbon materials and the high oxidizing capacity of Au 3+ (E = V for AuCl 4- ) REDUCING THERMAL TREATMENT (TTR) 300ºC, 4%H 2, 1h Ensure gold presents its elemental form Maintain sorbent properties after use

9 Technique Value Bulk Au, % ICP-OES 0.15 Surface Au, % SEM-EDX 4,4 Particle size, nm FE-SEM 23 Oxidized Au, % XPS Before 300 ºC treatment Reducing Thermal Treatment After 300 ºC treatment Au 0 :792% 79,2 Au 0 :878% 87,8

10 Hg capture tests in two different plants 1. The preliminary testing was carried out in a bench-scale plant that has been designed and built specifically to prove the sorbents. Different temperatures and flue gases have been tested. 2. The second set of experiments were carried out under real working conditions in an oxy-fuel combustion plant (~3kW th ) that burns Spanish lignite.

11 Hg feeding device DYNACAL OHM (Hg 2+ ) CVAAS (Hg 0 )

12 Temperature: ºC Gas velocity: 2.1 cm/s 80 W s /Q: g h l -1 W Au /Q: g h l Hg concentration: 100 g/m 3 Efficiency Hg Hg retained fed % saturation Hg retentio on efficiency, % oxyfuel O 2 /CO 2 conditions air O 2 conditions /N T (ºC) 80% 20% Hg retent tion efficiency y, % oxyfuel O 2 /CO 2 conditions air O 2 conditions /N T (ºC)

13 Hg-TPD of exhausted sorbent Regeneration temperature:220 ºC Mechanisms for Hg capture - Amalgamation (Au) Mechanisms for Hg capture at 220 ºC - Chemisorption (C) - Amalgamation (Au) - Chemisorption (C) Regeneration: Hg evolution at 220 ºC

14 Hg-TPD of exhausted sorbent 220 Cycles O 2 /CO 2 Retention temperature: 120 ºC Regeneration temperature:220 ºC

15 How many cycles Hg capture-regeneration could undergone the sorbent? ) ts-arbitrary scale Lin (Coun XRD for sorbent and exhausted sorbents o o XRD for fresh and exhausted sorbent 1. MC-Au-fresh 2. MC-Au-after Hg capture Au 3 Hg --- Hg/Au o o monolayer Hg/Au* {111}--- Hg/Au AMA Hg/Au Not detected by XRD 1 * defect-free surface Sample MC-Au-fresh MC-Au-after Hg capture MC-Au-after Hg regeneration 2 Binding energy (ev) Au 0 Au + 4f 5/2 4f 7/2 4f 5/2 4f 7/ XPS analysis on sorbent before and after Hg capture experiment and after in situ regeneration. Hg at% 0.13 Au at% 5.25 Hg/Au 0.025

16 In situ-xps studies Au oxidation state C (support) changes O increase S presence 1. Fresh sample-xps analysis 5% O 2 -CO 2. In-situ treatment ppmv SO 2 -CO 120ºC, 2h ppmv SO 2-5% O 2 -CO 2 3. Treated sample-xps analysis O 2 -CO 2 SO 2 -CO 2 No Au displacement (but increase of Au contribution) C unaltered O unaltered SO 2 -O 2 -CO 2 Au displacement (shift 0.1 ev to more oxidized state) C unaltered O little increase S detectable (difficult to quantify) Au displacement (shift 0.1 ev to more oxidized state) C unaltered O little increase S detectable (difficult to quantify) No mercury involved in this study

17 Retention temperature: 120ºC Gas velocity: 2.1 cm/s W s /Q: g h l -1 W Au /Q: g h l -1 Hg concentration: 100 g/m 3 Gas composition: Hg - CO 2 Hg - 5%O 2 -CO 2 Hg ppmv SO 2 -CO 2 Hg - 5%O ppmv SO 2 -CO 2 60% breakthrough Gas composition Hg-CO 2 Hg-5%O 2 -CO 2 Hg-2500ppmv-SO 2 -CO 2 Hg-5%O ppmv-SO 2 -CO 2 g Hg 0 /g sorbent 34,73 33,53 38,68 Hg 5%O ppmv SO 2 CO 2 37,29

18 Temperature: 120ºC Gas velocity: 2.1 cm/s W s /Q: g h l -1 W Au /Q: g h l -1 Hg concentration: 100 g/m 3 Gas composition: Hg - CO 2 Hg - 5%O 2 -CO 2 Hg ppmv SO 2 -CO 2 Hg - 5%O ppmv SO 2 -CO 2 Gas composition Hg-CO 2 Hg-O 2 -CO 2 Hg-SO 2 -CO 2 Hg-O 2 -SO 2 -CO 2 g Hg 0 /g sorbent Exhausted sorbent (AMA) 33,01 32,16 27,83 26,88 g Hg 2+ /g sorbent Impingers (AMA) 0 0 5,58 7,92 g Hg /g sorbent Total 33,01 32,16 33,41 34,80 g Hg/g sorbent breakthrough curve g 2 2 2,,,, 34,73 33,53 38,68 37,29

19 Temperature: 120ºC Gas velocity: 2.1 cm/s Sample process-xps studies W s /Q: g h l -1 Au oxidation state W Au /Q: g h l -1 C (support) changes Hg concentration: 100 g/m 3 Gas composition: Hg-5% O 2 -CO 2 O increase Hg-2500 ppmv SO 2 -CO 2 S presence Hg-5%O ppmv SO 2 -CO 2 Hg Hg-O 2 -CO 2 Au displacement (Hg-Au alloy, no increase of Au contribution) Hg/Au C and O unaltered Hg-SO 2 -O 2 -CO 2 Hg-SO 2 -CO 2 Au displacement and increase of Au contribution Hg/Au C unaltered O little increase S detectable (difficult to quantify) Au displacement and increase of Au contribution Hg/Au 0.03 Cunaltered eed O little increase and shift to higher BE S detectable (at.% 0.5)

20 Stack Analyzer VM300 CVAAS (Hg 0 ) O 2 /CO 2 35/65 AMA (Hg p ) OHM (Hg 2+ )

21 Coal: lignite Mercury in coal: 0,11 mg Hg/Kg coal Oxi-fuel combustion temperature: 925 ºC Gas composition of O 2 /CO 2 : 35/65 Q total : 2,23 m 3 N/h µg/m 3 mg/h Hg , Hg ,

22 Q total : 2,23 m 3 /h Aliquot Q Aliquot : 120 L/h q W s /Q: g h l -1 W Au /Q: g h l -1 8 x 10 % breakthrough EXPERIMENT Breakthrough Time RETENTION 97 min AMA Hg 0 exhausted sorbent 0,511 ppm Break. curve 0,525 ppm Hg 2+ AMA Impinger ppm Retention efficiency 93,3%

23 10 % breakthrough EXPERIMENT RETENTION REGENERATION Initial CHg 6,9 µg/m 3 16,2 µg/m 3 Breakthrough Time 97 min 60 min AMA Hg 0 exhausted sorbent 0,511 ppm 0,902 ppm Break. curve 0,525 ppm 1,164 ppm Hg 2+ AMA Impinger ppm 0,0003 ppm Retention ee efficiency ce cy 93,3% 95,8 %

24 A novel regenerable Au/C sorbent for Hg capture based on the direct reduction of an Au salt on a carbon monolith without the addition of reducing or protective chemicals has been developed. This sorbent exhibits a high Hg retention efficiency under O 2 /CO 2 atmospheres and it is maintained along several cycles. The amount of Hg captured doesn t vary significantly with temperature (50º- 150ºC), allowing the use of sorbents at different positions on the power plants. The presence of SO 2 in the flue gas leads to Hg oxidation in the presence of Au sorbent. So, sorbent can be used upstream FGD, because oxidized Hg will be retained at FGD unit, or downstream FGD, because in absence of SO 2 no oxidation is produced. This sorbent also shows high Hg retention efficiency under real working conditions in a fluidized bed oxy-fuel combustion plant.

25 To improve current deposition methodology to get smaller gold nanoparticles. To deepen knowledge about Au oxidation mechanism in oxycombustion environments, with the aim of preparing sorbents more resistant to oxidation. To add more components to the flue gas such as H 2 O or HCl to study how mercury retention and sorbent regenerability are affected.

26 Carmen Gómez Giménez Ponferrada, September 12 th 2013

27 Regenerable sorbent cost disposal byproducts regeneration cost /kg Hg* / kg Hg** Comparative cost of both technologies for the studied case. Transport and installation costs are excluded (8000h, 90% Hg removal, 6,6 µg/m 3 Hg, m 3 /h) * Source: A.P. Jones, J.W. Hoffmann, D.N. Smith, T.J. Feeley, J.T. Murphy DOE/NETL s Phase II Mercury Control Technology Field Testing Program. Preliminary Economic Analysis of Activated Carbon Injection U.S. Department of Energy ** Hg recovered value not considered

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