Dry Process for Removal of Pyrite from Coal.
U S Pat 3 540 662 1970 Nov; :
Pyritic sulfur was removed from pulverized coal by successive separations by particle size and particle mass, respectively. Thus, ground coal was air swept into a felvation (separation of airborne particles passed up through sizing screens) column and the oversize recycled. The undersize fraction (-400 mesh) was mixed with the light fraction. The intermediate fractions were separated by air classifiers (based on mass). Pyrite-depleted light product fractions were mixed with the undersize fraction and used in the conventional way.
U.S. Pat. 3,540,662; Nov. 17, 1970; Chem. Abstr. 74:56,017F