Classification Systems

An excellent discussion of the many classification systems, scientific as well as commercial, is provided by van Krevelen [1]. The commercial systems, which will be discussed here, consist of two primary systems— the American Society for Testing Materials (ASTM) system used in the United States/North America and an international Economic Commission for Europe (ECE) codification system developed in Europe. It is interesting that, in all countries, the classification systems used commercially are primarily based on the content of volatile matter [1]. In some countries, a second parameter is also used; in the United States, for example, this parameter is the heating value (see Figure 1-4). For many European countries, this parameter is either the caking or the coking properties. Caking coals are coals that pass through a plastic state upon heating during which they soften, swell, and resolidify into a coherent carbonaceous matrix, while noncaking coals do not become plastic when heated and produce a weakly coherent char residue. Coking coals are strongly caking coals that exhibit characteristics that make them suitable for conversion into metallurgical and other industrial cokes [10].

ASTM Classification System

The ASTM classification system (ASTM D388) distinguishes among four coal classes, each of which is subdivided into several groups (see Table 1-1). As previously mentioned, high-rank coals (i.e., medium volatile bituminous coals or those of higher rank) are classified based on their fixed-carbon and volatile-matter contents (expressed on a dmmf basis), while low-rank coals are classified in terms of their heating value (expressed on a mmmf basis). This classification system was developed for commercial applications but has proved to be satisfactory for certain scientific uses as well [9]. If a given

0 0

Post a comment