Characterization of residue from direct coal liquefaction and determination of its potential applicability as a source of fuel

• Author / Creator

  Iyer, Nitya A

• Direct coal liquefaction is a technology for producing liquid products from coal.
  One of the by-products from this process is coal liquefaction residue, which is remaining coal that was not converted to liquid products during the liquefaction process. The residue is enriched in mineral matter and the organic content is more refractory.The objective of our work was to characterize the residue produced under different DCL operating conditions and to evaluate the performance of the residue as a feed for gasifcation and combustion. The feed to the direct coal liquefaction process was Canadian sub-bituminous Coal Valley (CV) coal. The industrial solvents employed were hydrotreated (under N2 and H2) and non-hydrotreated poly-aromatic hydrocarbons (under N2). Different residues were obtained from the process, conducted at four different temperatures ranging from 300-450 C in an autoclave reactor (0.25 L) at an initial pressure of 20 bar. Coal liquid yields obtained for liquefaction using hydrotreated solvent were found to be much better, under the same operating conditions. Thus, effect of solvent and temperature in coal liquefaction is discussed briefly. The residues were further characterized for their mineral composition, organic content and particle sizes using various standard techniques: Thermogravimetic analyser (TGA), elemental analyser, mastersizer, FTIR spectrometer, X-ray fluorescence, surface area analyser. A great deal of variation in the chemical and physical composition of the residues were observed and found to be closely related to the efficiency of the process. In order to further investigate the potential applicability of liquefaction residues as a feedstock for boilers and gasifiers, the residues from the Coal Valley sub-bituminous coal liquefaction in hydrotreated solvent (N2) were gasified in a TGA. This proved to be a useful platform for comparison of the reactivity of the residues with that of raw coal. The kinetic parameters for the process were also determined under isothermal gasification conditions at temperatures 800 C, 950 C and 1000 C under O2 and at 950 C, 1000 C and 1100 C under CO2. Further, in order to determine the practical applicability of the coal residues as boiler feed, an entrained flow reactor (drop tube furnace) was employed to test the conversion efficiency of the residues. Though higher carbon conversion were found for residues, compared to raw coal, similar concerns due to ash-slagging would be prevalent for both cases.

• Subjects / Keywords

  • Residue gasification
  • Residue characterization
  • Coal liquefaction residue

• Graduation date

  Spring 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R33664

• 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.