Interrelationships between coal compositional parameters

Abstract

Analytical data from a set of 66 coal samples, ranging in rank from lignitic to low-volatile bituminous, were used to define relationships between coal properties. Unusual care was taken in selecting, collecting, preparing and analysing this set of premium samples providing a high degree of confidence in the conclusions obtained. It was found that univariate relationships between properties, which might seem to convey useful information, are generally of limited operational value and can lead to erroneous conclusions. However, multivariate correlations can predict a number of properties. Specific energy, volatile matter yield, and density (by helium pycnometry) can be estimated from the elemental composition according to the following expressions: Btu lb −1 = 145.9% C + 569.6% H − 53.89% O + 43.08% S − 6.3% Ash% VM = −0.408% C + 11.25% H + % O + 1.3% S g ml −1 = 0.01556% C − 0.04117% H + 0.02247% O + 0.02049% S + 0.0208% Ash The standard deviations of the residuals (estimated-experimental) for the above three correlations are 86 Btu lb −1, 1.5% VM and 0.013 g ml −1. The free-swelling index was found to correlate strongly with the oxygen content (for coals containing > 2 wt% oxygen, daf) and the petrographic composition according to the following expression: FSI = 5 + 4.68 f( O) − 0.00395 NPC 2 + 0.0897 NPC − 0.06 LIP where f( O) = sin(0.2513 O daf + 0.9505) NPC = ash weight% + inertinite, volume% mineral- free LIP = liptinite, volume%, mineral- free It is concluded that the elemental composition of coal can predict many physical properties and process responses. The petrographic composition must be considered when predicting plastic properties. Though petrographic composition influences other properties and process responses, microscopically obtained maceral percentages did not prove useful for quantitatively predicting properties or responses.