STEAM REFORMING OF COAL TAR BY USING CHEMICAL-LOOPING CARRIERS The 1st Australia-Japan Symposium on Carbon Resource Utilisation STEAM REFORMING OF COAL TAR BY USING CHEMICAL-LOOPING CARRIERS Melbourne, Australia. 27-30 November 2016 Department of Environmental Engineering Science, Graduate School of Science and Technology, Gunma University Battsetseg Tsedenbal, Naokatsu Kannari and Takayuki Takarada

COAL Coal will be still keeping as very important energy source. It has rich resources with stable low price, distributed widely all over the world. Fig.1 World power generation by source in 2014 and 2040 The future use of coal faces challenges such as high efficiency, low pollution and reduced CO2 emission. Reference: World Energy Outlook 2015

CARBON CAPTURE TECHNOLOGY Carbon Capture Technologies: Pre-Combustion, Post-combustion, Oxy-combustion. However these CO2 capturing technologies may increase the energy consumption of power plant by 25-40%. Chemical-looping process CO2-enriched flue gas No energy loss for CO2 capture Fuel Reactor (Reduction) Air Reactor (Oxidation) MexOy MexOy-1 Fuels Air CO2/H2O N2/O2 Gaseous Solids H2O(l) CO2 MexOy-1+½O2→MexOy+Heat Fuel+MexOy→MexOy-1+H2O+CO2 Fig.2 Schematic diagram of chemical-looping process 3

Coal reactions in the fuel reactor PYROLYSIS CHAR GASES (CO, H2, CH4, CO2, H2O, etc.) Primary TAR (Heavy hydrocarbons, etc.) REFORMING GASIFICATION CRACKING Products (CO, H2, CH4, CO2, H2O, Light hydrocarbons, etc.) CO, H2, CH4, CO2, H2O, unconverted carbon CL OXYGEN CARRIER Unconverted Gas (CO, CH4) Unconverted carbon Carbon Stripper Oxygen Polishing CO2, H2O Fig.3 Coal reactions in the fuel reactor of chemical looping process

THE OBJECTIVE Tar removal By performing steam reforming experiment of coal tar under chemical-looping conditions, to investigate the reactivity of Fe-based chemical-looping carriers for tar reforming. Natural Fe-based carrier: Ilmenite FeTiO3 Synthetic Fe-based carrier: Fe2O3/Al2O3 Tar removal COAL TAR causes operation failure due to clogging and blockage of pipeline

SAMPLES Adaro coal: Subbituminous (Indonesia) Particle size: 1.0mm Table 1 Proximate and Ultimate analyses of Adaro Coal Proximate analysis (wt%, d.b.) Ultimate analysis (wt%, d.b.) V.M. Ash F.C. C H N S Odiff 42.9 2.9 44 71.0 5.01 0.62 0.11 19.1 Natural oxygen carrier: Ilmenite FeTiO3 (Australia) Particle size: 75-150μm Synthetic oxygen carrier: Fe2O3/Al2O3 provided by JCOAL Table 2 Metal composition of carriers FeTiO3 Fe2O3/Al2O3 Fe (wt%) Ti (wt%) Fe (%) Al (%) 51.5 43.8 57.8 39.5

TAR REFORMING EXPERIMENT Thermocouples Reforming temperature 900℃ Steam generator Micro　Feeder on/off Experimental condition Gas flow: N₂+Steam 120ml/min S/C ratio: 0.5 Upper furnace: 25℃ to 900℃ Heating rate: 10℃/min　　 Lower furnace: 900℃ Coal: 1.0g Furnaces Calculation of gas yield Carrier: 3.5g Water trap Gas bag Heavy tar trap (silica wool) Product gas Water-soluble tar TOC GC-FID GC-TCD Fig.4　Experimental apparatus

COMBUSTION OF SOOT, CHAR AND HEAVY TAR Thermocouples CHAR SOOT HEAVY TAR Gas bag O₂ Combustion gas GC-FID Calculation of carbon yield Experimental condition Gas flow： O₂ 90 ml/min Heater: 25℃ to 750℃ for 30 min Holding time: 30 min Fig.5 Experimental apparatus for combustion

The Carbon balance after steam reforming Results & Discussion: Char Soot Gas Heavy tar Light tar Carbon balance （with Char） Carbon balance （wo Char） Light tar Heavy tar Gas Char Soot Sand FeTiO3 Fe2O3/Al2O3 Sand FeTiO3 Fe2O3/Al2O3 ・ The carbon yield of tar was decreased by using chemical looping carriers. FeTiO3, Fe2O3/Al2O3 promotes tar decomposition.

Tar deposits after steam reforming Results & Discussion: Tar deposits after steam reforming Sand FeTiO3 Fe2O3/Al2O3 Tar deposit 　Sand 　 > 　　　　FeTiO3 　>　 Fe2O3/Al2O3

Ilmenite-Reactivity for tar decomposition Carbon balance （wo Char） Product gas yield Light tar C2, C3 Heavy tar CH4 CO2 CO Gas H2 Soot Sand FeTiO3 Fe2O3/Al2O3 Sand FeTiO3 Fe2O3/Al2O3 As FeTiO3 is used as a carrier Heavy tar↓, Light tar↑, Soot↑　 Heavy tar cracking No big difference of gas component No oxidation by ilmenite CmHn (heavy) → CjHk(Light tar)

Fe2O3/Al2O3-Reactivity for tar decomposition Carbon balance （wo Char） Product gas yield Light tar C2, C3 Heavy tar CH4 CO2 CO Gas H2 Soot Sand FeTiO3 Fe2O3/Al2O3 Sand FeTiO3 Fe2O3/Al2O3 As FeTiO3 is used as a carrier Heavy tar↓, Light tar↓, Gas↑　 H2↓, CH4↓, CO2↑ CmHn + Fe2O3(Al2O3)→ CO2 + H2O + Fe/FeO(Al2O3) C + Fe2O3(Al2O3) → CO2 + Fe/FeO(Al2O3) CO + Fe2O3(Al2O3) → CO2 + Fe/FeO(Al2O3) CH4 + Fe2O3(Al2O3) → CO2 + H2O + Fe/FeO(Al2O3) H2 + Fe2O3(Al2O3) → H2O + Fe/FeO(Al2O3)

XRD profiles of carriers after steam reforming Results & Discussion: XRD profiles of carriers after steam reforming Ilmenite Fe2O3/Al2O3 FeTiO3 Fe2O3 Al2O3 Fe3O4 FeAl2O4 After steam reforming After steam reforming Fe2O3 + Volatiles → FeAl2O4 Fresh FeTiO3 Fresh Fe2O3/Al2O3 ・Ilmenite(FeTiO3): No crystal structural change ・Fe2O3/Al2O3：reduced to FeAl2O3 by volatiles

Carrier Reactivity for TPR & TPO Results & Discussion: Carrier Reactivity for TPR & TPO TG-TPO TG-TPR Fe2O3/Al2O3 FeTiO3 FeTiO3 Fe2O3/Al2O3 Reduction: Oxidation: Fe2O3/Al2O3 + 3H2 → 2Fe/Al2O3 + 3H2O Fe/Al2O3/ + 3/2O2 → Fe2O3/Al2O3 FeTiO3 + H2 → Fe + TiO2 + H2O 2Fe + TiO2 + 3/2O2 → Fe2TiO5 Comparing to FeTiO3, Redox reaction of Fe2O3/Al2O3 is occurred at lower temperature with higher velocity. Fe2O3/Al2O3 was more reactive and showed a higher tar reforming activity.

Conclusions We investigated the reactivity of 2 iron-based chemical looping carriers for tar reforming. Both natural and synthetic iron-based carriers have activity for tar reforming. Fe2O3/Al2O3 has higher tar conversion and considered the following reactions. It indicates that the reactivity of carriers depends on their redox reactivity. CmHn + Fe2O3(Al2O3)→ CO2 + H2O + Fe/FeO(Al2O3) C + Fe2O3(Al2O3) → CO2 + Fe/FeO(Al2O3) CO + Fe2O3(Al2O3) → CO2 + Fe/FeO(Al2O3) CH4 + Fe2O3(Al2O3) → CO2 + H2O + Fe/FeO(Al2O3) H2 + Fe2O3(Al2O3) → H2O + Fe/FeO(Al2O3)

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