Coal-water slurry and method for its preparation

Claim 1

A coal-water slurry comprised of from about 65 to about 85 weight percent of solids by weight of slurry, from about 15 to about 35 weight percent of carrier water by weight of slurry, and from about 0.01 to about 4.0 weight percent of polyelectrolyte dispersing agent by weight of dry coal in said slurry, wherein: (a) said coal-water slurry has a Brookfield viscosity of less than 4,000 centipoise when tested at a solids content of 75 weight percent, ambient temperature, and 60 revolutions per minute; (b) said coal-water slurry has a yield stress of from about 0.1 to about 10 Pascals; (c) from about 5 to about 36 weight percent of the particles of coal in said slurry are of colloidal size, and being smaller than about 3 microns, and said colloidal sized particles of coal have a net zeta potential in said coal-water slurry of from about 15 to about 85 millivolts; (d) at least about 85 weight percent of the particles of coal in said coal-water slurry have a particle size less than 300 microns; and (e) said coal-water slurry comprises a compact of finely-divided particles of coal dispersed in said carrier water; and (f) said compact of finely divided particles of coal has a particle size distribution substantially in accordance with the following formula: ##EQU6## CPFT is the cumulative weight percent, dry basis, of particles finer than a particle of stated size, D, D is the diameter of any particle in the compact, D L is the diameter of the largest particle in the compact, sieve size or its equivalent, being from about 38 to about 400 microns, D S is the diameter of the smallest particle in the compact, being from about 0.01 to about 0.4 microns, and n is numerical exponent, with n being from about 0.2 to about 0.5 and with all diameters sized in microns.