Projects on coal characterization

Danish power stations use coals, imported from various countries around the world. Since the coals may differ considerably in burning properties, the purchasers have a marked interest in characterization of the coals prior to use. In a Danish project existing methods were compared, using ten selected coal samples and equipment and techniques for particulate coal in the USA and Sweden were also used. TGA measurements and chemical and petrographic characterizations were made in Denmark. A multivariate analysis of six selected characterizations, using the Sandia equipment (CA, USA) results as target parameters, was made to create a statistical model which would allow characterization of an “unknown” coal with a minimum of analytical effort and cost. In a separate investigation, involving a flat-flame burner, an entrained-flow reactor (both in USA) and a TGA, oxidative coal pyrolysis was studied. A distributed activation energy concept was applied to produce kinetic parameters for a large-scale combustor model to evaluate the conditions in a flame. A parallel project (named IKI) presents an innovation with pyrolysis by a controlled laser beam of a very thin sample plate in a specific chamber, followed by isothermic gasification. The characterizations obtained with the IKI method on coal samples of the DP agree well with the Sandia results. Compared with the concept of coal ranks, for which two coals of same rank may behave differently, coal characterization methods have taken big steps forward, but we are still far from seeing the new tools employed in practice.