Study of the interrelationships among chemical and petrographic variables of United States coals

Abstract

Multivariate statistical techniques are used in a study of the interrelationships among various coal properties. The properties chosen for study are the components of the ultimate analysis (carbon, hydrogen, organic sulfur, nitrogen and oxygen); moisture; volatile matter; calorific value; maximum reflectance of the vitrinite-group macerals; and the relative proportions of the vitrinite-, liptinite-, and inertinite-group macerals. The coals included in the study are from four coal provinces (Eastern, Interior, Rocky Mountain, and Northern Great Plains) and range in rank from lignite to anthracite. A coal's characteristics, properties, and utilization behavior are determined by the maceral and mineral materials composing the coal. The level of coalification achieved by the maceral materials is of critical importance in fixing the properties. A factor analysis performed on all data together indicates that most variation in the data set is correlated with changes in rank (variables which vary with rank include carbon, oxygen, calorific value, moisture, volatile matter, and reflectance). The maceral groups account for the next greatest amount of variation. Nitrogen and sulfur are each independent of all other variables. A cluster analysis indicates that the data set represents a continuum with no distinct groups; however, the data set may be dissected into fourmore » groups distinguished from each other on the basis of rank, on the relative proportions of the maceral groups, and on the organic sulfur content. Factor analyses of the individual groups provide insights into coalification at various stages of rank.« less