Effect of Fe on NO release during char combustion in air and O₂/CO₂

Abstract

The chemistry of char was probed by studying nitrogen release under the reactions with air and oxy-fuel combustion. The experiments were conducted in a drop tube furnace and a fixed bed flow reactor. NO was observed during those experiments. The results show that the particle size of char generated at 1073 K in CO₂ is larger than that in N₂. However, at 1573 K, it is smaller in CO₂ atmosphere due to particle breaking by gasification of char and CO₂. The Fe addition increases the NO conversion ratio, and the effect of Fe rises steeply with the process going until it becomes stable in the end. The results also indicate that the release of NO increases more significantly with the Fe addition in oxy-fuel environment.

Key words： NO; Fe; char; combustion; CO₂

Acknowledgements

This work was partially supported by the National Natural Science Foundation of China (Grant Nos. 50906028, 51021065).

References

1 Wall T F. Combustion processes for carbon capture. Proceedings of the Combustion Institute, 2007, 31(1): 31–47

2 Wall T F, Liu Y H, Spero C, Elliott L, Khare S, Rathnam R, Zeenathal F, Moghtaderi B, Sheng C D, Gupta R, Yamada T, Makino K, Yu J L. An overview on oxyfuel coal combustion—state of the art research and technology development. Chemical Engineering Research & Design, 2009, 87(8): 1003–1016

3 Buhre B J P, Elliott L K, Sheng C D, Gupta R P, Wall T F. Oxy-fuel combustion technology for coal-fired power generation. Progress in Energy and Combustion Science, 2005, 31(4): 283–307

4 Toftegaard M B, Brix J, Jensen P A, Glarborg P, Jensen A D. Oxy-fuel combustion of solid fuels. Progress in Energy and Combustion Science, 2010, 36(5): 581–625

5 Croiset E, Thambimuthu K, Palmer A. Coal combustion in O₂/CO₂ mixtures compared with air. Canadian Journal of Chemical Engineering, 2000, 78(2): 402–407

6 Zheng L G, Furimsky E. Assessment of coal combustion in O₂+CO₂ by equilibrium calculations. Fuel Processing Technology, 2003, 81(1): 23–34

7 Liu H, Zailani R, Gibbs B M. Comparisons of pulverized coal combustion in air and in mixtures of O₂/CO₂. Fuel, 2005, 84(7): 833–840

8 Tan Y W, Croiset E, Douglas M A, Thambimuthu K V. Combustion characteristics of coal in a mixture of oxygen and recycled flue gas. Fuel, 2006, 85(4): 507–512

9 Kiga T, Takano S, Kimura N, Omata K, Okawa M, Mori T, Kato M. Characteristics of pulverized-coal combustion in the system of oxygen/recycled flue gas combustion. Energy Conversion and Management, 1997, 38(<Suppl/>): 129–134

10 Molina A, Shaddix C R. Ignition and devolatilization of pulverized bituminous coal particles during oxygen/carbon dioxide coal combustion. Proceedings of the Combustion Institute, 2007, 31(2): 1905–1912

11 Andersson K, Johansson R, Hjartstam S, Johnsson F, Leckner B. Radiation intensity of lignite-fired oxy-fuel flames. Experimental Thermal and Fluid Science, 2008, 33(1): 67–76

12 Andersson K, Johnsson F. Process evaluation of an 865 MWe lignite fired O₂/CO₂ power plant. Energy Conversion and Management, 2006, 47(18,19): 3487–3498

13 Andersson K, Johnsson F. Flame and radiation characteristics of gas-fired O₂/CO₂ combustion. Fuel, 2007, 86(5,6): 656–668

14 Hu Y Q, Kobayashi N, Hasatani M. Effects of coal properties on recycled-NO_x reduction in coal combustion with O₂/recycled flue gas. Energy Conversion and Management, 2003, 44(14): 2331–2340

15 Hu Y Q, Kobayashi N, Hasatani M. The reduction of recycled-NO_x in coal combustion with O₂/recycled flue gas under low recycling ratio. Fuel, 2001, 80(13): 1851–1855

16 Glarborg P, Jensen A D, Johnsson J E. Fuel nitrogen conversion in solid fuel fired systems. Progress in Energy and Combustion Science, 2003, 29(2): 89–113

17 Andersson K, Normann F, Johnsson F, Leckner B. NO emission during oxy-fuel combustion of lignite. Industrial & Engineering Chemistry Research, 2008, 47(6): 1835–1845

18 Croiset E, Thambimuthu K V. NO_x and SO₂ emissions from O₂/CO₂ recycle coal combustion. Fuel, 2001, 80(14): 2117–2121

19 Hu Y, Naito S, Kobayashi N, Hasatani M. CO₂, NO_x and SO₂ emissions from the combustion of coal with high oxygen concentration gases. Fuel, 2000, 79(15): 1925–1932

20 Hu Y Q, Kobayashi N, Hasatani M. Effects of coal properties on recycled-NO_x reduction in coal combustion with O₂/recycled flue gas. Energy Conversion and Management, 2003, 44(14): 2331–2340

21 Liu H, Zailani R, Gibbs B A. Pulverized coal combustion in air and in O₂/CO₂ mixtures with NO_x recycle. Fuel, 2005, 84(16): 2109–2115

22 Croiset E, Thambimuthu K V. NO_x and SO₂ emission from O₂/CO₂ recycled coal combustion. Fuel, 2001, 80(14): 2117–2121

23 Normann F, Andersson K, Leckner B, Johnsson F. High-temperature reduction of nitrogen oxides in oxy-fuel combustion. Fuel, 2008, 87(17,18): 3579–3585

24 Mendiara T, Glarborg P. Reburn chemistry in oxy-fuel combustion of methane. Energy & Fuels, 2009, 23(7): 3565–3572

25 Okazaki K, Ando T. NO_x reduction mechanism in coal combustion with recycled CO₂. Energy, 1997, 22(2,3): 207–215

26 Lopez D, Calo J. The NO-Carbon reaction: The influence of potassium and CO on reactivity and populations of oxygen surface complexes. Energy, 2007, 21(4): 1872–1877

27 Park D C, Day S J, Nelson P F. Nitrogen release during reaction of coal char with O₂, CO₂, and H₂O. Proceedings of the Combustion Institute, 2005, 30(2): 2169–2175

28 Zhao Z B, Qiu J S, Li W, Li B Q. Influence of mineral matter in coal on decomposition of NO over coal chars and emission of NO during char combustion. Fuel, 2003, 82(8): 949–957

29 Gong X Z, Guo Z C, Wang Z. Variation of char structure during Anthracite pyrolysis catalyzed by Fe₂O₃ and its influence on char combustion reactivity. Energy & Fuels, 2009, 23(9): 4547–4552

30 Xu X F, Gu Y D, Chen S Y. The effect of Fe catalytic agent on nitrogen release in coal pyrolysis. Journal of Fuel Chemistry, 1998, 26(1): 18–23 (in Chinese)

31 Liu X W, Xu M H, Hong Y, Yu D X. Effect of combustion parameters on the emission and chemical composition of particulate matter during coal Combustion. Energy & Fuels, 2007, 21(1): 157–162