A progress report on the Alpern Coal Classification

Abstract

The Alpern Coal Classification has already been largely utilized and successfully applied, both to Laurasian (North Atlantic) and Gondwana coals. It was accepted on basic principles by the International Committee for Coal Petrology, and, as the official contribution of France, it has been recently also partly adopted by the Economic Commission for Europe of the United Nations in Geneva (1988). This paper deals with the improvement of the previous versions of the classification, mainly by introducing new statistical data in order to establish more accurately proposed rank limits. A ternary division for RANK is maintained with the categories: low-rank coal or lignite (instead of brown coal because high-rank lignites may be black not brown), medium-rank coal or bituminous coal, and high-rank coal or anthracite. The prefixes hypo-, meso- and meta-, are used for rank subdivision, thus avoiding non-coherent previous prefixes such as sub-(bituminous) and semi-(anthracite). The selected rank parameters are: moisture holding capacity (ash free) and calorific value (moist, ash free) for lignites, mean random reflectance for bituminous coals and anthracites. Correlations for bed moisture (ash free) and calorific value (dry, ash free) are given for lignites. Correlations for volatile-matter content, mean maximum vitrinite-reflectance, and hydrogen content are also given for bituminous coals and anthracites. TYPE is determined from maceral data and is divided into: vitric (vitrinite (V) > 60%), fusic [V < 60%; inertinite (I) > liptinite (L), and liptic (V) < 60%; L >. I). The ash content and the washability potential at 10% ash level are used to determine GRADE (or FACIES) and allow the distinction between transportable clean coals and non-washable coals. The run-of-mine ash content (dry basis) permits the division between: coal, middlings, and shale. If the type is liptic, the subdivisions “sapropelic coals” and “oil shales” are used. These are not washable but are solid fuels with a positive energy potential. If the coals to be classified are clean (or washed) the vertical axis becomes free and can be used, for example, for swelling properties in bituminous coals. The system has been recently computerized and allows for data to be displayed effectively for all relevant fields of application. Computer-output examples are presented for coals from a Euramerican and a Gondwana basin.