Pyrolysis, combustion, and gasification properties of pulverized coal and char in CO2-rich gas flow were investigated by using gravimetric-differential thermal analysis (TG-DTA) with changing O2%, heating temperature gradient, and flow rate of CO2-rich gases provided. Together with TG-DTA, flue gas generated from the heated coal, such as CO, CO2, and hydrocarbons (HCs), was analyzed simultaneously on the heating process. The optimum O2% in CO2-rich gas for combustion and gasification of coal or char was discussed by analyzing flue gas with changing O2 from 0 to 5%. The experimental results indicate that O2% has an especially large effect on carbon oxidation at temperature less than 1100°C, and lower O2 concentration promotes gasification reaction by producing CO gas over 1100°C in temperature. The TG-DTA results with gas analyses have presented basic reference data that show the effects of O2 concentration and heating rate on coal physical and chemical behaviors for the expected technologies on coal gasification in CO2-rich gas and oxygen combustion and underground coal gasification. 1. Introduction As the increased fossil fuels consumption such as coal, oil, and gas leads to rapid deterioration of global environment, nowadays low-carbon economy is getting more and more attention. Low-carbon economy mostly linked greenhouse gases emissions and energy usage together [1, 2]. The economic growth of energy consumption countries impels intensive use of energy and other natural resources; thus, more residues and wastes discharged in the nature lead to environmental aggravation. China has been the second largest energy consumption country in the world, where the total energy consumption increased from 302 million tons of standard coal equivalent in 1960 to 2850 million tons in 2008 [3]. Coal as an energy source plays an important and indispensable role on future energy mix due to its proven stability in supply and its low cost. Coal has improved its long-term position as the world’s most widely available fossil energy source with a very large resource base and economically recoverable reserves that are much greater than those of oil and gas. Coal is the most abundant fossil fuel in China. Present recoverable reserves occupied about 11.67% of global coal reserves based on Key World Energy Statistics 2010 [4], ranked third in the world, with potential total reserves far in excess of this amount. Chinese coal consumption by the year 2020 will be nearly 4.8 billion tons per year with the bulk being consumed through the combustion processes. Therefore, present
References
[1]
W. Zhang and Z. Wu, “A study on establishing low-carbon auditing system in china,” Low Carbon Economy, vol. 3, no. 2, pp. 35–38, 2012.
[2]
S. Zeng and S. Zhang, “Literature review of carbon finance and low carbon economy for constructing low carbon society in China,” Low Carbon Economy, vol. 2, no. 1, pp. 15–19, 2011.
[3]
R. Lei, Y. Zhang, and S. Wei, “International technology spillover, energy consumption and CO2 emissions in China,” Low Carbon Economy, vol. 3, no. 3, pp. 49–53, 2012.
[4]
Key World Energy Statistics, International Energy Agency (IEA), “Clearly-presented data on the supply, transformation and consumption of all major energy sources,” Stedi Media, 2010.
[5]
A. Williams, M. Pourkashanian, J. M. Jones, and N. Skorupska, Combustion and Gasification of Coal, Applied Energy Technology Series, Taylor & Francis, New York, NY, USA, 1999.
[6]
S. Hossain, “An econometric analysis for CO2 emissions, energy consumption, economic growth, foreign trade and urbanization of Japan,” Low Carbon Economy, vol. 3, no. 3, pp. 92–105, 2012.
[7]
C. Ramírez and J. González, “Contribution of finance to the low carbon economy,” Low Carbon Economy, vol. 2, no. 2, pp. 62–70, 2011.
[8]
IPCC Working Group II, “Climate change 2007: impacts, adaptation and vulnerability,” Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, 2007.
[9]
Key World Energy Statistics, International Energy Agency (IEA), “Evolution from 1971 to 2010 of World CO2 emissions by region,” Stedi Media, 2011.
[10]
IEA, “CO2 emissions from fuel combustion,” 2011, http://www.iea.org/CO2highlights.
[11]
H. Herzog and D. Golomb, “Carbon capture and storage from fossil fuel use,” Encyclopaedia of Energy, vol. 1, pp. 277–287, 2004.
[12]
K. Jordal, M. Anheden, J. Y. Yan, and L. Str？mberg, “Oxyfuel combustion for coal-fired power generation with CO2 capture-opportunities and challenges,” Greenhouse Gas Control Technologies 7, vol. 1, pp. 201–209, 2005.
[13]
Office of Fossil Energy, “Carbon capture & separation,” U.S. Department of Energy, 2004, http://fossil.energy.gov/programs/sequestration.
[14]
J. C. Chen, Z. S. Liu, and J. S. Huang, “Emission characteristics of coal combustion in different O2/N2, O2/CO2 and O2/RFG atmosphere,” Journal of Hazardous Materials, vol. 142, no. 1-2, pp. 266–271, 2007.
[15]
D. Singh, E. Croiset, P. L. Douglas, and M. A. Douglas, “Techno-economic study of CO2 capture from an existing coal-fired power plant: MEA scrubbing versus O2/CO2 recycle combustion,” Energy Conversion and Management, vol. 44, no. 19, pp. 3073–3091, 2003.
[16]
E. S. Hecht, C. R. Shaddix, M. Geier, A. Molina, and B. S. Haynes, “Effect of CO2 and steam gasification reactions on the oxy-combustion of pulverized coal char,” Combustion and Flame, vol. 159, pp. 3437–3447, 2012.
[17]
B. J. P. Buhre, L. K. Elliott, C. D. Sheng, R. P. Gupta, and T. F. Wall, “Oxy-fuel combustion technology for coal-fired power generation,” Progress in Energy and Combustion Science, vol. 31, no. 4, pp. 283–307, 2005.
[18]
Q. Li, C. Zhao, X. Chen, W. Wu, and Y. Li, “Comparison of pulverized coal combustion in air and in O2/CO2 mixtures by thermo-gravimetric analysis,” Journal of Analytical and Applied Pyrolysis, vol. 85, no. 1-2, pp. 521–528, 2009.
[19]
H. Liu, “Combustion of coal chars in O2/CO2 and O2/N2 mixtures: a comparative study with non-isothermal thermogravimetric analyzer (TGA) tests,” Energy and Fuels, vol. 23, no. 9, pp. 4278–4285, 2009.
[20]
Z. H. Li, X. M. Zhang, Y. Sugai, J. R. Wang, and K. Sasaki, “Properties and developments of combustion and gasification of coal and char in a CO2-rich and recycled flue gases atmosphere by rapid heating,” Journal of Combustion, vol. 2012, Article ID 241587, 11 pages, 2012.
[21]
P. Lu, G. X. Liao, J. H. Sun, and P. D. Li, “Experimental research on index gas of the coal spontaneous at low-temperature stage,” Journal of Loss Prevention in the Process Industries, vol. 17, no. 3, pp. 243–247, 2004.
[22]
J. Xie, W. M. Cheng, and F. Q. Liu, “Technology and effect of open nitrogen injection at fully mechanized face,” Journal of Safety in Coal Mines, vol. 3, pp. 33–35, 2007.
[23]
H. Y. Qi, Y. H. Li, C. F. You, J. Yuan, and X. C. Xu, “Emission on NOx in high temperature combustion with low oxygen concentration,” Journal of Combustion Science and Technology, vol. 8, no. 1, pp. 17–22, 2002.
[24]
C. X. Luo and W. H. Zhou, “Coal gasification technology & its application,” Sino-Global Energy, vol. 1, pp. 28–35, 2009.
[25]
J. J. Huang, Y. T. Fang, and Y. Wang, “Development and progress of modern coal gasification technology,” Journal of Fuel Chemistry and Technology, vol. 30, no. 5, pp. 385–391, 2002.
[26]
Y. F. Liu and X. K. Xue, “Thermal calculation methods for oxy-fuel combustion boilers,” East China Electric Power, vol. 36, pp. 355–357, 2008.
[27]
J. R. Wang, C. B. Deng, Y. F. Shan, L. Hong, and W. D. Lu, “New classifying method of the spontaneous combustion tendency,” Journal of the China Coal Society, vol. 33, no. 1, pp. 47–50, 2008.
