Flame stability of ultra-lean methane and synthesisgas combustion in inert porous burners

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Institute of Thermal Engineering Chair of Gas and Heat

synthesisgas combustion in inert porous burners

Bergakademie Freiberg I Gustav-Zeuner-Str.

1 Institute of Thermal Engineering Chair of Gas and Heat Technology Flame stability of ultra-lean methane and synthesisgas combustion in inert porous burners presented by Stefan Voss Friday, 15 th of June 2012 TU Bergakademie Freiberg I Gustav-Zeuner-Str. 7 I Freiberg Tel / I Fax / I

2 Freiberg s location Saxony Freiberg is located between Dresden and Chemnitz!

3 TU Bergakademie Freiberg founded in 1765 oldest mining school in the world Materials Environment Geo Energy 5000 students; 1200 researchers & technical staff

Motivation Utilization of lean gas mixtures low calorific value gas

fields: Gasification/Reforming Fuel Cell Technology Power to Gas

of premixed sustained flame in porous inert media Gasification Reforming

4 Motivation Utilization of lean gas mixtures low calorific value gas mixtures hydrogen synthetic gas mixtures are applicable in several fields: Gasification/Reforming Fuel Cell Technology Power to Gas Scenarios Pyrolysis Landfill Gases Characterization of global stability of premixed sustained flame in porous inert media Gasification Reforming Fuel Cell Technology Power to Gas Source: Gräbner (2010) Source: Sunfire (2012) Source: OPAL

Technological attractiveness +2 0-2 +2 Question Mark Strategy R&D

Cell 1 2 3 4 0 Answers (Required) R&D Effort Strategy of

Combustion 2) Non-premixed Combustion 3) Catalytic Combustion 4)

5 Technological attractiveness Question Mark Strategy R&D Withdrawal Technology Portfolio Post-Combustion Systems in Fuel Cell Answers (Required) R&D Effort Strategy of Technology Leadership R&D Rationalization -2 1) Premixed Combustion 2) Non-premixed Combustion 3) Catalytic Combustion 4) Direct Combustion (on the stack) Technological Risk very high high average low very low

6 Premixed Combustion Premixed flames their realization as flexible and controllable flames with adjustable flame temperature and with comparable opportunities of reducing high-temperature based pollutants to non-premixed flames. F. Weinberg (1986)

7 Ultra-Lean combustion low reaction rates low flame temperatures leads to low emissions! burning velocity S L influenced by H 2 and inert fractions moderate flame stability hydro-dynamic instabilities thermo-diffusive instabilities, for Le < 1 Le D thermal diffusivity molecular diffusivity T. Poinsot (2005)

Combustion within Porous Inert Media Flow stabilization (change in cross-sectional

heat production (Pe Pe= 20) for H = 2 based fuels λ f heat release Structure of a

zone Silicium infiltrated Silicium Carbide foam/sponge (SiSiC) Global Properties 10

8 Combustion within Porous Inert Media Flow stabilization (change in cross-sectional area) Thermal stabilization (Peclet-criteria) (Pe s 65) for CxHy L dp,eff ρf cpf heat production (Pe Pe= 20) for H = 2 based fuels λ f heat release Structure of a lean premixed flame: δ T = preheating zone δ r = reaction zone δ ε =post combustion zone Silicium infiltrated Silicium Carbide foam/sponge (SiSiC) Global Properties 10 ppi ( 3 mm pore size) macro porosity 0.8 to 0.9 T 1540 C high thermal shock resistance

9 Dimensions of the Model Burner [mm]

1000 ppm (dry, O 2 -free) 60 mg/kwh DIN EN 50465 Blue

10 Regulations/Directives of Emissions for stationary CHP systems NO x CO Regulation 260 mg/kwh 50 mg/kwh 1000 ppm (dry, O 2 -free) 60 mg/kwh DIN EN Blue Angel RAL-ZU ppm (dry, O 2 -free) IEC

11 SOFC System FlameSOFC Combined Heat and Power CHP system FlameSOFC EC. Grant no SES6

Grant no 019875-SES6 Start-up/Load rejection

12 SOFC mode Ultra-lean gas mixtures Fuel Cell FlameSOFC EC. Grant no SES6 Start-up/Load rejection mode (Reformate) CO < 35 mg/kwh NO x < 24 mg/kwh CO < 30 mg/kwh NO x < 20 mg/kwh

13 SOFC mode Ultra-lean gas mixtures Fuel Cell FlameSOFC EC. Grant no SES6 Start-up/Load rejection mode (Reformate)

14 SOFC mode Ultra-lean gas mixtures Fuel Cell FlameSOFC EC. Grant no SES6 Temperature Distribution Temperature Distribution at the outlet plane of the burner 340 kw/m², = 1.4 (ϕ =0.5), T u = 673 K

[1] L. Bobrova et al., Catalysis Today (2009) [2] J. Requies et al., Catalysis Today (2009) [3] Z. Al-Hamamre, S. Voss, D. Trimis, Int. J. Hydrogen Energy (2009) [4] M. Zahedi nezhad et al., Int. J. Hydrogen Energy (2009) [5] Thinh X.

15 [1] L. Bobrova et al., Catalysis Today (2009) [2] J. Requies et al., Catalysis Today (2009) [3] Z. Al-Hamamre, S. Voss, D. Trimis, Int. J. Hydrogen Energy (2009) [4] M. Zahedi nezhad et al., Int. J. Hydrogen Energy (2009) [5] Thinh X. Ho et al., Chemical Eng. Sci. (2009) [6] C. Cremers te al., Fuel Cells (2007) Reforming Scenarios for SOFC systems H 2 CO N 2 CO 2 H 2 /CO Dilution H u vol. % molar % MJ/kg A1 13,3 6, ,954 A2 10,0 5, ,419 A3 8,6 4, ,214 A4 6,7 3, ,916 B1 15,0 5, ,961 B2 11,2 3, ,417 B3 9,7 3, ,210 B4 7,5 2, ,911 C1 16,0 4, ,964 C2 12,0 3, ,415 C3 10,4 2, ,208 C4 8,0 2, ,908 Synthetic gas mixtures (H 2 /CO) for different reforming strategies with a post utilization in a fuel cell (SOFC) system (Methan (CH 4 ) primary fuel) H 2 /CO (molar): 2 11 Dilution (inert fraction in the fuel stream): %

16 Ultra-lean gas mixtures Hydrogen Carbon Monoxide 400 kw/m² = 2.0 (ϕ =0.5) T u = 673 K 1000 kw/m² = 2.0 (ϕ =0.5) T u = 673 K

17 Ultra-lean gas mixtures Hydrogen - Nitrogen

18 Ultra-lean gas mixtures Methane - Carbon Dioxide

19 Ultra-lean gas mixtures Methane T u =298K

Conclusion The flame stabilization within porous inert media offers the possibility to operate over a wide range and to utilize specific gas mixtures and to achieve extremely low emissions.

20 Conclusion The flame stabilization within porous inert media offers the possibility to operate over a wide range and to utilize specific gas mixtures and to achieve extremely low emissions. Source: ITM Power (2012) Further details of the complexity in the flame structure are given in: S. Voss et al., Investigation on the thermal flame thickness for lean premixed combustion of low calorific H 2 /CO mixtures within porous inert media, Proceedings of the Combustion Institute, Vol. 34, paper accepted

21 Thank you for your attention contact details Stefan Voss TU Bergakademie Freiberg Institute of Thermal Engineering Germany BMBF (2012) happy to take questions!

Measurement of key values in combustion: The heat flux burner method to determine laminar burning velocities

Measurement of key values in combustion: The heat flux burner method to determine laminar burning velocities Stefan Voss Institute of Thermal Engineering, TU Bergakademie Freiberg Outline 1. Introduction