Entrained Flow Gasification of Oil Sand Coke

• Author / Creator

  Vejahati, Farshid

• The effect of blending woody biomass material with fluid coke and coal on the co-pyrolysis process was investigated in an entrained flow gasifier. The SEM results showed a particle size decrease and shape change from needle to spherical as the temperature was increased. Agglomeration between particles occurred above 1250°C due to the low ash fusion temperature of biomass. The results were verified by particle size distribution analysis. Reactivity of pyrolyzed blended and pure fuels decreased with increasing temperature. No agglomeration was found for blends of coal and coke. Pyrolysis at high temperatures also showed a significant surface area development for coke.
  
  The combined effects of the steam and oxygen concentrations and coal/coke blending ratio were investigated in gasification of fluid coke with sub-bituminous and lignite coals using Response Surface Methodology (RSM). Six response variables were considered: H2, CO and syngas production, H2/CO ratio, gasification efficiency, and carbon conversion. Experiments were conducted over a temperature range of 1000-1400°C, using steam and oxygen to carbon weight ratios of (0.9-4.3) and (0-0.4), respectively. Using RSM, the interactions between different factors were determined. The response variable correlations were employed to determine the experimental conditions under which the H2 production was maximized.
  The intrinsic rates for Char-O2, char-CO2, and char-H2O reactions were developed for coke. The validity of thermogravimetric determination of kinetics was discussed in depth. Four surface area measurement techniques were used to normalize the specific reaction rate: N2-BET, GCMC-NLDFT and DR models, and active surface area measured by CO2 chemisorption. The objective was to find the specific surface area which gives the best reduction in the variability of reaction rate r(X) using the regressor variable S(X). Overall ASA was found to be the best regressor.
  A numerical simulation was developed for entrained flow gasifier using the underlying physics and the intrinsic rates. The intrinsic rates were successfully implemented into the Fluent CFD code via user defined functions. The energy content of particle on a dry basis was conserved by properly calculating the formation enthalpy of volatile matter. The results were compared to the experiment data for carbon conversion, H2, CH4, CO and CO2 concentrations. In general, a fair agreement between simulation and experiment results were found.

• Subjects / Keywords

  • Gasification
  • Entrained flow
  • Oil sand coke

• Graduation date

  Spring 2012

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R35T5K

• 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.