›› 2014, Vol. 22 ›› Issue (11/12): 1208-1214.doi: 10.1016/j.cjche.2014.09.011


Effect of Gasifying Medium on the Coal Chemical Looping Gasification with CaSO4 as Oxygen Carrier

Yongzhuo Liu1, Weihua Jia1, Qingjie Guo1, Hojung Ryu2   

  1. 1 College of Chemical Engineering, Qingdao University of Science & Technology, Key Laboratory of Clean Chemical Processing Engineering of Shandong Province, Qingdao 266000, China;
    2 Climate Change Technology Research Division, Korea Institute of Energy Research, Daejeon 305-343, Republic of Korea
  • Received:2013-09-02 Revised:2013-12-16 Online:2014-12-28 Published:2014-12-24
  • Supported by:
    Supported by the Research and Development Programof the Korea Institute of Energy Research (KIER) (B4-2431-04), the National Natural Science Foundation of China (21276129, 20876079) and the Natural Science Funds for Distinguished Young Scholar in Shandong Province (JQ200904).

Abstract: The chemical looping gasification uses an oxygen carrier for solid fuel gasification by supplying insufficient lattice oxygen. The effect of gasifyingmedium on the coal chemical looping gasification with CaSO4 as oxygen carrier is investigated in this paper. The thermodynamical analysis indicates that the addition of steam and CO2 into the system can reduce the reaction temperature, at which the concentration of syngas reaches its maximum value. Experimental result in thermogravimetric analyzer and a fixed-bed reactor shows that the mixture sample goes through three stages, drying stage, pyrolysis stage and chemical looping gasification stage, with the temperature for three different gaseousmedia. The peak fitting and isoconversional methods are used to determine the reaction mechanism of the complex reactions in the chemical looping gasification process. It demonstrates that the gasifying medium (steam or CO2) boosts the chemical looping process by reducing the activation energy in the overall reaction and gasification reactions of coal char. However, themechanism using steamas the gasifying medium differs from that using CO2.With steam as the gasifying medium, parallel reactions occur in the beginning stage, followed by a limiting stage shifting from a kinetic to a diffusion regime. It is opposite to the reaction mechanism with CO2 as the gasifying medium.

Key words: Chemical looping gasification, CaSO4 oxygen carrier, Reaction mechanism, Syngas generation