ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Effect of atmosphere and temperature on syngas production during gasification of Zhundong lignite and water-washed Zhundong lignite in a fixed-bed reactor

Xiuqi Shu, Jianbo Li, Jian Hao, Zhuo Liu, Quanhai Wang, and Xiaofeng Lu

Chongqing University, Chongqing, China

E-mail: jianbo.li@cqu.edu.cn

Abstract: The effect of temperature and atmosphere on the syngas yields of CO and H₂ during gasification of Zhundong lignite (ZD) and water-washed Zhundong lignite (WWZD) in a fixed-bed reactor was investigated. The experiments were run over temperatures from 750 to 950 °C, atmospheres of pure steam or with CO₂ addition ratios of 25–75%. The syngas yield rate, overall yield, carbon conversion rate and the activation energy for gasification of carbon in coal were obtained. Results showed that the yield rates of CO and H₂ during pure steam gasification of ZD at 750 °C increased from 0 to a maximum of 5.4 and 19.4 ml/min and decreased afterwards, when H₂ was found as the main syngas. Moreover, CO was not detected while H₂ was identified at a later stage of gasification, indicating that the char-steam gasification and water–gas shift reaction were dominated at this stage. As the temperature increased to 950 °C, the maximum yield rates of CO and H₂ increased, confirming that the increase in temperature promoted gasification. Likewise, the increase in CO₂ ratio from 25 to 75% resulted in a maximum CO yield rate of 163.87 ml/min at 950 °C, promoting CO yield when CO₂ was the gasifying agent. The maximum yield of H₂ was, however, decreased while the Boudouard reaction was promoted. Water washing was found to significantly influence gasification. The maximum yield rates of CO and H₂ were decreased and the gasification time was prolonged, indicating that the reactivity of char-steam gasification was decreased due to the removal of Na contents by water washing. In addition, the overall yield of CO was increased as temperature and the CO₂ percentage increased, whereas that of H₂ decreased. The activation energy for steam gasification of ZD as determined by the momogeneous model (HM), shrinking core model (SCM) and isoconversional method was in the range of 53.36–56.14 kJ/mol, all of which were applicable for determining the activation energy of ZD gasification under steam.

Keywords: Activation energy ; Carbon conversion ; Gasification ; Water washing ; Zhundong lignite 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-019-00898-4

Chemical Papers 74 (2) 555–569 (2020)