The application of Raman spectroscopy and related techniques to coal chars taken from a slagging gasifier

The work described in this thesis falls into two sections. (1) Data derived from Raman spectroscopy have been compared with data obtained from other techniques (X-ray diffraction and optical spectroscopy) in order to establish the nature of the fundamental information available from the Raman spectra available from coals and coal chars. It has thus been established that the Raman spectra of the materials examined are dependent upon the sizes of the aromatic carbon layers of which they are composed, and this in turn is determined by the maximum heat treatment temperature to which the materials have been subjected. This relationship has been investigated in detail, in order that it may be used to measure the maximum heat treatment temperature of a coal char of unknown thermal history. It has been established that preparation conditions other than temperature, such as pressure, atmosphere, heating rate, soak time and tar addition have a negligible effect on this relationship, and thus its general applicability to the study of chars of unknown thermal history has been established. (2) Both Raman spectroscopy and optical microscopy have been applied to coal chars produced in, and subsequently removed from, the British Gas Slagging Gasifier. Optical microscopy was used to assess the homogeneity or heterogeneity of the chars; Raman spectroscopy was then applied to the homogeneous chars, and thermal profiles within the gasifier were established for several gasifier runs.