Mercury removal from oxyfuel combustion flue gas over cobalt oxide loaded magnetospheres catalyst from fly ash

Transcription

1 Mercury removal from oxyfuel combustion flue gas over cobalt oxide loaded magnetospheres catalyst from fly ash Xu Qisheng 1, Liu Yaming 1, Jianping Yang 2, Yongchun Zhao 2,*, Junying Zhang 2, Chuguang Zheng 2 1 Electric Power Research Institute of Guangdong Power Grid Company 2 State key laboratory of coal combustion, Huazhong University of Science & Technology *Contact information: yczhao@hust.edu.cn

2 1 Background 2 Experimenatal section Preparation of Co-MF catalyst Experimental approach 3 Results and discussion Catalyst characterization Hg 0 removal performance 4 Conclusions Contents

3 Background CO 2 emission The increasing emission of CO 2 is the primary contributor to global warming.

4 Background CO 2 emission Hg? What s about mercury? Liquid metal embrittlement and amalgam corrosion: damage the CO 2 compression and purification units Volatility, persistence and bio accumulation: great environmental concern

5 Background Mercury Control Activated carbon injection Calcium sorbents Fly ash Sorbent injection Capture Hg 2+ Hg 0 Hg 0 oxidation Capture Hg p FGD Flue gas SNCR SCR ESP or FF Coal& air SO 2, NO, Hg 2+, Hg 0, Hg p 700 F >2500 F Fly ash

6 Background Mercury Control Magnetic Regenerable Sorbents Sorbent recovery Removal of mercury from the industrial waste Fig. Schematic of regenerable magnetosphere catalyst for mercury emission control from coal-fired power plants Influence of the flue gas components Cost of operation

7 1 Background 2 Experimenatal section Preparation of Co-MF catalyst Experimental approach 3 Results and discussion Catalyst characterization Hg 0 removal performance 4 Conclusions Contents

8 Catalyst preparation fly ash magnetospheres Magnetic seperation Impregnating in cobalt nitrate ( Co(NO 3 ) 2 solutions Dried at 100 for 12h Dried magnetospheres impregnated with ( Co(NO 3 ) 2 Calcined at 400 for 4h Co-MF catalyst

9 Experimental approach Hg 0 permeation device Simulated flue gas feed system Fixed-bed reactor system Mercury analysis system

10 1 Background 2 Experimenatal section Preparation of Co-MF catalyst Experimental approach 3 Results and discussion Catalyst characterization Hg 0 removal performance 4 Conclusions Contents

11 Magnetism Catalyst characterization The Co-MF catalyst is superparamanetism, so the spent catalyst could be easily seperated from fly ash to reuse.

12 Removal of Hg 0 by Co-MF catalysts SEM and EDX ρ=9% ρ=12% ρ=15% Loading value ρ = W nitrate /W MF

13 Catalyst characterization XRD & XPS analysis Cobalt oxide existed amorphous state in isolation. Cobalt oxide on the catalyst is mainly present as Co 3 O 4.

14 Hg 0 removal performance The enriched CO 2 (70%) in oxyfuel combustion assisted the mercury oxidation Why? Hg 0 (g) Hg 0 (ad) CO 2 (g) CO 2 (ad) CO 2 (ad)+ catalyst C O, C=O 2Hg 0 (ad)+ 2C O 2HgO+C=C 2Hg 0 (ad)+ 2C=O 2HgO+C=O Forming function group of C O, C=O from enriched CO 2

15 Hg 0 removal performance SO 2 NO HCl SO 2 -NO-HCl Under both atmospheres, the mercury removal efficiency decreased with the addition of SO 2 and NO. HCl could obviously promote the mercury oxidition. The enriched CO 2 in oxyfuel combustion atmosphere could somewhat weaken the inhibition of SO 2 and NO.

16 Hg 0 removal performance Regeneration performance Regeneration method: the spent catalyst was heated at 400 for 2h in air. adsorption regeneration

17 Regeneration performance Hg 0 removal performance Variation of surface chemistry before and after regeneration The mercury adsorbed on the spent catalyst are totally released. The status of Co and O on the spent catalyst was recovered after regenerated.

18 1 Background 2 Experimenatal section Preparation of Co-MF catalyst Experimental approach 3 Results and discussion Catalyst characterization Hg 0 removal performance 4 Conclusions Contents

19 Conclusions The presence of enriched CO 2 (70%) in oxyfuel combustion atmosphere assisted the mercury oxidation due to the oxidation over function group of C O formed from enriched CO 2. Under both atmospheres, the mercury removal efficiency decreased with the addition of SO 2, NO, and H 2 O. The enriched CO 2 in oxyfuel combustion atmosphere could somewhat weaken the inhibition of SO 2, NO, and H 2 O. The multiple capture regeneration cycles demonstrated that the Co MF catalyst present good regeneration performance in oxyfuel combustion atmosphere.

20 Acknowledgement The National Key Basic Research Program (973) of China (No.2014CB238904) The National Natural Science Foundation of China (NSFC) (No ).

21 Thank you for your attention! Any questions?