STABILITY OF COAL - AIR BUBBLE - WATER SYSTEM

Measurements of the detachment force of an air bubble from the surface of various coal ranks were carried out in water. These values were compared with those calculated from the contact angle values measured in coal - air bubble - water system and from the values (from literature) of the dispersion and the nondispersion components of the surface free energy of the studied coals. On the basis of the obtained results we found that there is a good agreement among the measured and calculated values of the detachment force for given coal rank. The coals studied may be divided into three groups according to their ability to form the stable attachment with air bubble. The arithmetic weighted mean of the detachment forces were correlated with the natural flotability of coals and the linear relationship as obtained.