Coal-water mixtures from low rank coal and process of preparation thereof

摘要

A process for preparing a coal-water fuel from a low rank coal. The first step of the process provides for an aqueous slurry containing particles of the low rank coal. A quantity of an agglomerating agent in the range of about 10% to 30% weight to dry ash - free low rank coal weight is added to the slurry to produce a mixture. The mixture is then agitated to form agglomerates. Following separation of the agglomerates, the agglomerates are contacted with steam or an inert gas having a temperature in the range of about 250 DEG C. to 420 DEG C. at substantially atmospheric pressure to produce partially deoiled agglomerates containing less than about 7% by weight of residual bridging liquid and having a moisture capacity reduced by a factor of at least about 2.5 at a relative humidity of 96% compared to the moisture capacity of the low rank coal. A first amount of the partially deoiled agglomerates is then first wet milled in the presence of water and at least one anionic dispersant, wherein the concentration of the first amount of the partially deoiled agglomerates in water is about 35% to 55% by weight, to produce a micronized fraction of the first amount of the partially deoiled agglomerates having a maximum size of about 15 to 25 micrometers and an average diameter of about 4 to 10 micrometers. Finally, a combination of the micronized fraction of the first amount of the partially deoiled agglomerates and a second amount of the partially deoiled agglomerates is final wet milled in the presence of water, wherein the combination is comprised of about 20% to 50% by weight of the micronized fraction, to produce the coal-water fuel which contains solid particles having a maximum size of about 250 to 300 micrometers and an average diameter of about 15 to 30 micrometers. In a further embodiment, the process utilizes a paste in place of the agglomerates, the paste being formed by mixing particles of the low rank coal with a quantity of a bridging liquid.