Determination of Free and Bound Water in Fine Coal Filter Cake

Abstract

The bound water in fine coal filter cake represents the water that cannot be removed using mechanical dewatering techniques. The amount of bound water in a fine coal filter cake, in other words, represents the moisture content achievable by an ideal dewatering technique. In this study the dilatometer technique was used to measure the bound and free water in a fine coal filter cake. Results showed that addition of cationic (0.25 kg=t) and non-ionic (1 kg=t) surfactants reduced the bound water content in the filter cake from 13.73% to 3.72% and 8.28%, respectively. Decrease in bound water content was attributed to the adsorption of surfactants on the coal surface, which increased the coal hydrophobicity. Addition of 10 g=t of cationic and anionic flocculants also reduced the bound water content from 13.73% to 4.58% and 6.63%, respectively, which was attributed to the replacement of surface water molecules with the polymer. Based on the free and bound water data, ideal dewatering curves were developed for both surfactants and flocculants.

Review and Perspectives of Anionic Dispersants for Coal–Water Slurry

“…In particular, the inherent moisture of coal is an essential characteristic that affects the properties of CWS. The moisture of the CWS system can be classified into free water and bound water including the capillary, interparticle, adhesive, and internally adsorbable water. − The free water, filled in the interparticle gaps, can ensure the fluidity and lubricity of the CWS system. However, the bound water on the coal surface and in the coal pore cannot contribute to the fluidity and reduction of viscosity for CWS. − Sufficient free water is necessary to maintain the lower viscosity of the CWS suspension.…”