Chinese Journal of Chemical Engineering ›› 2021, Vol. 32 ›› Issue (4): 393-407.doi: 10.1016/j.cjche.2020.10.011

• Energy, Resources and Environmental Technology • Previous Articles     Next Articles

An advanced ash fusion study on the melting behaviour of coal, oil shale and blends under gasification conditions using picture analysis and graphing method

Yang Meng1, Peng Jiang2, Yuxin Yan1,2, Yuxin Pan1, Xinyun Wu1, Haitao Zhao3, Nusrat Sharmin1, Edward Lester4, Tao Wu1,2,5, Cheng Heng Pang1,2,5   

  1. 1 Department of Chemical and Environmental Engineering, The University of Nottingham Ningbo China, Ningbo 315100, China;
    2 Ningbo New Materials Institute, The University of Nottingham, Ningbo 315042, China;
    3 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge 02139, USA;
    4 Department of Chemical and Environmental Engineering, The University of Nottingham, Nottingham NG7 2RD, UK;
    5 Key Laboratory for Carbonaceous Wastes Processing and Process Intensification Research of Zhejiang Province, The University of Nottingham Ningbo China, Ningbo 315100, China
  • Received:2020-02-16 Revised:2020-09-26 Online:2021-04-28 Published:2021-06-19
  • Contact: Cheng Heng Pang
  • Supported by:
    The authors gratefully express gratitude to all parties which have contributed towards the success of this project, both financially and technically, especially the S&T Innovation 2025 Major Special Programme (grant number 2018B10022) and the Ningbo Natural Science Foundation Programme (grant number 2018A610069) funded by the Ningbo Science and Technology Bureau, China, as well as the Industrial Technology Innovation and Industrialization of Science and Technology Project, China (grant number 2014A35001-2) and the UNNC FoSE Faculty Inspiration Grant, China. The Zhejiang Provincial Department of Science and Technology is also acknowledged for this research under its Provincial Key Laboratory Programme (2020E10018).

Abstract: This study investigates the potential of solid fuel blending as an effective approach to manipulate ash melting behaviour to alleviate ash-related problems during gasification, thus improving design, operability and safety. The ash fusion characteristics of Qinghai bituminous coal together with Fushun, Xinghua and Laoheishan oil shales (and their respective blends) were quantified using a novel picture analysis and graphing method, which incorporates conventional ash fusion study, dilatometry and sintering strength test, in a CO/CO2 atmosphere. This image-based characterisation method was used to monitor and quantify the complete melting behaviour of ash samples from room temperature to 1520℃. The impacts of blending on compositional changes during heating were determined experimentally via X-ray diffraction and validated computationally using FactSage. Results showed that the melting point of Qinghai coal ash to be the lowest at 1116℃, but would increase up to 1208℃, 1161℃ and 1160℃ with the addition of 30%-50% of Laoheishan, Fushun, and Xinghua oil shales, respectively. The formation of high-melting anorthite and mullite structures inhibits the formation of low-melting hercynite. However, the sintering point of Qinghai coal ash was seen to decrease from 1005℃ to 855℃, 834℃, and 819℃ in the same blends due to the formation of low-melting aluminosilicate. Results also showed that blending directly influences the sintering strength during the various stages of melting. The key finding from this study is that it is possible to mitigate against the severe ash slagging and fouling issue arising from high calcium and iron coals by co-gasification with a high silica-alumina oil shale. Moreover, blending coals with oil shales can also modify the ash melting behaviour of fuels to create the optimal ash chemistry that meets the design specification of the gasifier, without adversely affecting thermal performance.

Key words: Oil shale, Coal, Image-based ash fusion test, Co-gasification, Mineral transformation