Coal continued processes, sulfur production

When coals are pyrolyzed, this process is continued by the near complete elimination of hydrogen and oxygen. The carbon residue that remains, however, still contains small quantities of nitrogen and sulfur. Typical values for carbon, hydrogen, volatile matter (i.e., low-molecular-weight products of the pyrolysis), and residual (fixed, nonvolatile) carbon of the various classes of coal (Table 6.1) provide the basis of a system for describing coal rank (Chapters 2 and 8). 

---