Effects of gasification temperature and atmosphere on char structural evolution and AAEM retention during the gasification of Loy Yang brown coal

Abstract This study aims to investigate the influence of gasification temperature on the evolution of char structure and the retention of alkali and alkaline earth metallic (AAEM) species for a Victorian brown coal. The experiments were carried out at 800, 850 and 900 °C in pure CO 2 , 15% H 2 O balanced with Ar and 15% H 2 O balanced with CO 2 in a one-stage fluidised-bed/fixed-bed reactor. FT-Raman spectroscopy was used to characterise the structural features of the chars obtained at varying conversion levels during gasification. The concentrations of AAEM species in the chars left after gasification were quantified with inductively coupled plasma – optical emission spectroscopy. The specific char-O 2 reactivity of the gasified char was measured in a thermogravimetric analyser. The results show that the CO 2 and H 2 O partly compete for the active sites on the char. The increasing total Raman area caused by the formation of O-containing structures in char does not appear to be the only factor determining the char gasification rate in H 2 O-containing atmospheres. With increasing temperature, CO 2 plays an increasingly more important role in the char evolution and subsequently influences the AAEM retention in char from the gas mixture. The gasification temperature does not change the individual reaction pathway for char-CO 2 or char-H 2 O reaction within temperature range investigated.

[1]  Chun-Zhu Li,et al.  Changes in nascent char structure during the gasification of low-rank coals in CO2 , 2015 .

[2]  Y. Ohtsuka,et al.  Gasification and Combustion of Brown Coal , 2004 .

[3]  Chun-Zhu Li,et al.  Inhibiting and other effects of hydrogen during gasification: Further insights from FT-Raman spectroscopy , 2014 .

[4]  Chun-Zhu Li,et al.  FT-Raman spectroscopic study of the evolution of char structure during the pyrolysis of a Victorian brown coal , 2006 .

[5]  Takayuki Takarada,et al.  Reactivities of 34 coals under steam gasification , 1985 .

[6]  Hongwei Wu,et al.  Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part I. Volatilisation of Na and Cl from a set of NaCl-loaded samples , 2002 .

[7]  C. Sheng,et al.  Influences of carbon structure on the reactivities of lignite char reacting with CO2 and NO , 2010 .

[8]  K. Norinaga,et al.  Low-temperature gasification of biomass and lignite: Consideration of key thermochemical phenomena, rearrangement of reactions, and reactor configuration , 2014 .

[9]  S. Bhattacharya,et al.  Kinetics of CO2 and steam gasification of Victorian brown coal chars , 2016 .

[10]  Chun-Zhu Li,et al.  Fates and roles of alkali and alkaline earth metals during the pyrolysis of a Victorian brown coal , 2000 .

[11]  Chun-Zhu Li.  Special Issue—Gasification: a Route to Clean Energy , 2006 .

[12]  Shuai Wang,et al.  A preliminary Raman spectroscopic perspective for the roles of catalysts during char gasification , 2014 .

[13]  F. Wang,et al.  Effects of oxygen on the structure and reactivity of char during steam gasification of Shengli brown coal , 2015 .

[14]  Chun-Zhu Li,et al.  Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part VIII. Catalysis and changes in char structure during gasification in steam , 2006 .

[15]  Chun-Zhu Li.  Some recent advances in the understanding of the pyrolysis and gasification behaviour of Victorian brown coal , 2007 .

[16]  Chun-Zhu Li,et al.  Changes in char reactivity and structure during the gasification of a Victorian brown coal: Comparison between gasification in O2 and CO2 , 2010 .

[17]  Chun-Zhu Li,et al.  Volatilisation of alkali and alkaline earth metallic species during the gasification of a Victorian brown coal in CO2 , 2005 .

[18]  Philip L. Walker,et al.  Gas Reactions of Carbon , 1975 .

[19]  Chun-Zhu Li,et al.  Effects of gasifying agent on the evolution of char structure during the gasification of Victorian brown coal , 2013 .

[20]  Yonggang Wang,et al.  Effect of steam concentration on char reactivity and structure in the presence/absence of oxygen using Shengli brown coal , 2015 .

[21]  Hongwei Wu,et al.  Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part IV. Catalytic effects of NaCl and ion-exchangeable Na in coal on char reactivity☆ , 2003 .

[22]  Chun-Zhu Li,et al.  Structural transformation of nascent char during the fast pyrolysis of mallee wood and low-rank coals , 2015 .