THE INFLUENCE OF N-ALKANES ON WETTABILITY DF LOW COAL RANKS

Contact angle measurements were carried out in coal / n-alkanes film - air bubble - water systems. Then theoretical an analysis of the equilibrium state of that system was carried out on the basis of the components of the surface free energy of coal of various ranks. The contact angles were measured for four ranks of Polish coal which surfaces were covered with n-alkanes film in the homological series from n-hexane to n-hexadecane. On the basis of the studies and calculations carried out we have concluded that the values of the contact angle depend on the rank of coal, a thickness of n-alkane film and its structure and the presence of water film under the air bubble. It was also found that the changes of the- values of the contact angles measured in the mentioned sytems as a function of the number of contacted air bubbles were similar to those calculated on the basis of the solution of Young equation in function of the surface free energy of coals precovered with n-alkane film.     

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.     

THE INFLUENCE OF N-ALKANES ON WETTABILITY DF LOW COAL RANKS

Abstract

Contact angle measurements were carried out in coal / n-alkanes film - air bubble - water systems. Then theoretical an analysis of the equilibrium state of that system was carried out on the basis of the components of the surface free energy of coal of various ranks. The contact angles were measured for four ranks of Polish coal which surfaces were covered with n-alkanes film in the homological series from n-hexane to n-hexadecane. On the basis of the studies and calculations carried out we have concluded that the values of the contact angle depend on the rank of coal, a thickness of n-alkane film and its structure and the presence of water film under the air bubble. It was also found that the changes of the- values of the contact angles measured in the mentioned sytems as a function of the number of contacted air bubbles were similar to those calculated on the basis of the solution of Young equation in function of the surface free energy of coals precovered with n-alkane film.     

STABILITY OF COAL - AIR BUBBLE - WATER SYSTEM

Abstract

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.