Preparation of coal slurries

Claim 1

IN A PROCESS FOR TREATING COAL PARTICLES WHICH TEND TO FORM SCALE IN A TUBULAR HEATING ZONE IN WHICH A FLOWABLE MIXTURE OF PARTICLES OF COAL IN WATER ARE PASSED INTO AND THROUGH SAID HEATING ZONE AND SAID MIXTURE IS HEATED DURING PASSAGE THROUGH SAID HEATING ZONE TO VAPORIZE WATER THEREFROM AND FORM A FLOWING DISPERSION OF COAL PARTICLES IN STEAM, THE IMPROVEMENT COMPRISING REMOVING ULTRAFINE PARTICLES FROM SAID COAL PARTICLES THEREBY REDUCING THE SCALE FORMING TENDENCIES OF SAID MIXTURE WHICH COMPRISES THE FOLLOWING STEPS: (A) FORMING A SLURRY OF SAID COAL PARTICLES IN WATER COMPRISING NOT MORE THAN 50 PERCENT COAL AND CONTAINING PARTICLES SMALLER THAN 10 MICRONS, (B) ADDING AMMONIUM HYDROXIDE TO SAID SLURRY IN AN AMOUNT EQUIVALENT TO 0.05 TO 0.2 VOLUME PERCENT OF A 30 WEIGHT PERCENT AQUEOUS AMMONIUM HYDROXIDE SOLUTION BASED ON THE VOLUME OF SAID SLURRY EFFECTING DEFLOCCULATION OF FINE PARTICLES OF SOLID MATERIAL, AND (C) WITHDRAWING WATER CONTAINING PRECIPITATED SOLIDS AND COAL PARTICLES SMALLER THAN 10 MICRONS FROM REMAINING COAL PARTICLES.