Coal, as energy resource, possesses numerous characteristics and properties which all have an influence on its gasification behaviour. The two properties considered critically important when evaluating a coal source for gasification are its mineral content and slagging behaviour. Research has indicated that slag formation can be inhibited or even prevented by the addition of a fluxing agent. It is thus of great importance to understand the mineral interaction during gasification, in order to select a suitable fluxing agent for the prevention of slagging and clinker formation in the gasifier.
The aim of this dissertation is to evaluate the slagging properties of a coal source with the addition of iron as a fluxing agent and to study the transformation of the mineral and added iron during gasification.
A pre-determined amount of elemental iron (between 2 and 20 percentage by mass) was added to three different coal samples obtained from Sasol's operations in South Africa. The transformation of the iron in conjunction with the possible iron-containing minerals present in the coal was studied by means of Mossbauer spectroscopy. Typical characterisation analyses were also carried out on the original coal samples. The ash fusion temperature analyses (AFT) were used to study the slagging behaviour of the iron-spiked coal samples. Even though AFT analyses only provide an average flow property, it gives a good indication of the changes that the iron addition induces in coal properties. FactSage modelling was carried out in conjunction with the Mossbauer and AFT analyses.
The AFT analysis on all of the samples indicated that the iron addition led to a 20% decrease in the AFT of all three the coal samples. The decrease observed, can be attributed to three main reasons: Formation of lower melting iron-containing phases, bridging of oxygen bonds by FeO and Fe203and the lowering of the viscosity by the iron-oxides, mainly hematite.
Mossbauer spectra of the three original coal samples indicated that pyrite was the only iron-bearing mineral present / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/2519 |
| Date | January 2008 |
| Creators | Prinsloo, Christoffel Bernardus |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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