Effects of Oxygen-Containing Functional Groups and Pore Structure on Nonfreezable Water and Bound Water in Coal

Abstract

Contents of three forms of water in coal: free water, bound water, and nonfreezable water were measured with a coal prepared at different humid conditions (23–25°C, 53, 75, 97% relative humidity (RH), as received basis) by using differential scanning calorimetry. The obtained data showed that coal prepared at 97%RH or below contained one or two forms of water: only nonfreezable water or nonfreezable water and bound water. Contents of two forms of water, oxygen-containing functional groups (phenolic hydroxyl and carboxyl groups), specific surface area and pore volume of coals were measured with five coals, and the relationships between the contents of two forms of water and the coal structures were evaluated. It was clarified that the contents of nonfreezable water had good correlations with total contents of the phenolic hydroxyl and carboxyl groups, and the contents of bound water prepared at 97%RH was more correlated with pore volume than specific surface area.