Depletion of conventional fossil fuel resources, as well as concerns regarding their environmental impact is a driving factor in the search for cleaner alternative fuels. Through the gasification of solid fuels, the produced syngas can be reacted to produce a cleaner, alternative liquid fuel. This thesis presents the development and use of a combination of fundamental and process models to evaluate alternative fuel production through a pressurised entrained flow gasification process. These include an equilibrium model, a one dimensional model and a process model. An equilibrium model using the non-stoichiometric approach based on the minimisation of Gibbs free energy and the Lagrange multipliers was established. A series of evaluations were performed to study the impact of the process conditions related to the entrained flow gasification, at the same time validating the model through comparisons with commercial software. It was shown that the model was not only quick to be developed, the results were also in excellent agreement with the commercial software it was compared to. A detailed one dimensional model of an entrained flow gasifier was developed from first principles. It is more complex than the equilibrium model, as it allows for evaluation of the variables along the length of the gasifier. Review of the available one-dimensional models of entrained flow gasifiers in the literature revealed inconsistent implementation of heat transfer mechanisms. The study showed that the solid-wall radiation along with the heterogeneous heat of reactions were the dominant heat transfer mechanisms in the entrained flow gasifier. In addition, although this model was developed specifically for a coal gasification process, assessment of biomass addition was also studied. ]t was shown that the best biomass mixtures were between 25% - 50%. A process model was developed in AspenHYSYS, which has enabled the entrained flow gasifier to be integrated with related auxiliary process equipment to model desired operating conditions. Implementation of the coal and biomass gasification for a polygeneration process is promising. Technoeconomic studies reveal that although biomass introduction may increase the costs of fuel, they are more environmentally-friendly as negative carbon emission can be achieved.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:595675 |
| Date | January 2013 |
| Creators | Rasid, Ruwaida Abdul |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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