Oxidative Coal Dissolution a Systematic Study

• Author / Creator

  Cantillo Olave, Cristhian Camilo

• The coal industry in Canada boasts abundant reserves, with significant potential for value addition through innovative processes. Oxidative coal dissolution (OCD) emerges as a promising method to generate high-value products from coal, using air as the oxidant, making it a cost-effective and environmentally favorable approach. This thesis focuses on evaluating the impact of critical operating parameters on OCD, seeking to enhance its efficiency and product selectivity for large-scale applications.
  The research started with a comprehensive overview of coal composition, ranks, and properties, followed by an exploration of the oxidation process itself. The study narrows down the scope to oxygen in air as the oxidant and explores the engineering challenges associated with OCD, including different operating parameters such as oxidant type, oxidant availability, temperature, time, water-to-coal ratio, and pH control.
  An initial set of experiments at atmospheric pressure with temperatures up to 95 °C revealed that OCD at low temperatures has limited carbon yield to liquid products. To overcome this, OCD reactions at elevated pressures of 5 MPa and temperatures ranging from 90 to 180 °C were conducted. These conditions significantly improve carbon yield to liquid products, providing a better understanding of carbon conversion and product distribution. However, overoxidation remains a challenge at higher temperatures and pressures, leading to increased carbon conversion to gaseous products. To address this issue, further experiments at 1 MPa pressure at same temperature range were performed, improving carbon selectivity to liquid products, though at the cost of decreased yield. It was found that the optimal selectivity and yield towards liquid products occur at 150 °C,
  Additionally, an unexpected increase in heating value was observed in the residue product after OCD reactions at 90 °C, contradicting conventional expectations. To explore this phenomenon further, additional reactions were conducted using nitrogen instead of air, revealing that the decrease in the oxygen-to-carbon molar ratio responsible for the heating value increase is not solely attributed to the oxidative coal dissolution process. Instead, a hypothesis suggests that under specific reaction conditions, a portion of initially bonded oxygen within the coal molecule is liberated, possibly promoting the exudation of oxygen-rich organic compounds from the coal porous structure.

• Subjects / Keywords

  • Oxidative coal dissolution
  • Temperature changes
  • Oxidant availability
  • Carbon yield
  • heating value

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-czxs-hk95

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.