Skip to Main Content
 

Global Search Box

 
 
 

ETD Abstract Container

Abstract Header

Mathematical Modeling of Ultra-Superheated Steam Gasification

Abstract Details

, Doctor of Philosophy (PhD), Ohio University, Chemical Engineering (Engineering and Technology).
Pure steam gasification has been of interest in hydrogen production, but with the challenge of supplying heat for endothermic reactions. Traditional solutions included either combusting feedstocks at the price of decreasing carbon conversion ratio, or using costly heating apparatus. Therefore, a distributed gasifier with an Ultra-Superheated-Steam (USS) generator was invented, satisfying the heat requirement and avoiding carbon combustion in steam gasification. This project developed the first version of the Ultra-Superheated-Steam-Fluidization-Model (USSFM V1.0) for the USS gasifier. A stand-alone equilibrium combustion model was firstly developed to calculate the USS mixture, which was the input to the USSFM V1.0. Model development of the USSFM V1.0 included assumptions, governing equations, boundary conditions, supporting equations and iterative schemes of guessed values. There were three nested loops in the dense bed and one loop in the freeboard. The USSFM V1.0 included one main routine and twenty-four subroutines. The USSFM V1.0 was validated with experimental data from the Enercon USS gasifier. The calculated USS mixture had a trace of oxygen, validating the initial expectation of creating an oxygen-free environment in the gasifier. Simulations showed that the USS mixture could satisfy the gasification heat requirement without partial carbon combustion. The USSFM V1.0 had good predictions on the H2% in all tests, and on other variables at a level of the lower oxygen feed. Provided with higher oxygen feed, the USSFM V1.0 simulated hotter temperatures, higher CO% and lower CO2%. Errors were explained by assumptions of equilibrium combustion, adiabatic reactors, reaction kinetics, etc. By investigating specific modeling data, gas-particle convective heat transfers were found to be critical in energy balance equations of both emulsion gas and particles, while bubble size controlled both the mass and energy balance equations of bubble gas. Parametric study suggested a lower level of oxygen feed for higher content of hydrogen. However, too little oxygen would impede fluidization in the bed. The reasonability of iterative schemes and the stability of USSFM V1.0 were tested by the sensitivity analysis of two guessed values. Analytical Hierarchy Process analysis indicated that large-scale gasification is advantageous for hydrogen production but with impediments of high capital cost and CO2 emissions. This study manifested the USS gasifier offering the possibility of generating H2-rich and CO2-lean syngas in a much cheaper distributed way. Currently, the FORTRAN-based USSFM V1.0 had a good correlation with experimental data with a small oxygen feed. On the demand of wider applications, suggestions were proposed at last for the model improvement in future.
David Bayless (Advisor)
Martin Mohlenkamp (Committee Member)
Kevin Crist (Committee Member)
Ariaster Chimeli (Committee Member)
Ben Stuart (Committee Member)

Recommended Citations

Citations

  • Xin, F. (2013). Mathematical Modeling of Ultra-Superheated Steam Gasification [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1364825034

    APA Style (7th edition)

  • Xin, Fen. Mathematical Modeling of Ultra-Superheated Steam Gasification. 2013. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1364825034.

    MLA Style (8th edition)

  • Xin, Fen. "Mathematical Modeling of Ultra-Superheated Steam Gasification." Doctoral dissertation, Ohio University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1364825034

    Chicago Manual of Style (17th edition)