SELECTIVE COMMINUTION OF COAL FOR ENHANCED REMOVAL OF MINERAL MATTER

ON-LINE PROCESSING OF COAL PRIOR TO COMBUSTION IN PULVERIZED COAL BOILERS INVOLVES FIRST CRUSHING THE BULK COAL. CRUSHED COAL IS THEN CONVEYED ON WEIGH-BELT FEEDERS TO LARGE HAMMER MILLS WHERE IT IS REDUCED TO ITS FINAL SIZE. BEFORD DELIVERY TO THE BURNERS, THE PULVERIZED COAL IS AERODYNAMICALLY CLASSIFIED IN CYCLONES OR SIMILAR INERTIAL SEPARATORRS TO REMOVE LARGER COAL PARTICLES AND DENSER MINERAL MATTER. THE PULVERIZATION PROCESS IS NON-SELECTIVE, HOWEVER, AND PRODUCES FINE MINERAL MATTER THAN CAN PASS THROUGH THE CLASSIFIERS AND CONTRIBUTE TO ASH FOULING AND EMISSIONS OF TOXIC METALS AND SULFUR OXIDES. IN CONTRAST, THE SELECTIVE COMMINUTION PROCESS CAN SOFTEN AND FRAGMENT THE CARBONACEOUS MATRIX OF CRUSHED COAL PRIOR TO PULVERIZING, WITHOUT AFFECTING THE PYRITIC AND QUARTZ MINERAL COMPONENTS. THIS REDUCES THE AMOUNT OF ENERGY NEEDED FOR PULVERIZATION AND THE FINENESS TO WHICH MINERAL INCLUSIONS ARE GROUND, MAKING THE FINAL AERODYNAMIC CLASSIFICATION PROCESS MORE EFFECTIVE. IN CONTRAST WITH DENSITY-BASED SEPARATION PROCESSES, SUCH AS FLOATATION, SELECTIVE COMMINUTION CAN BE PERFORMED ON-LINE AND DOES NOT REQUIRE POST TREATMENT SUCH AS WASHING AND DRYING. DURING PHASE I THE EFFECTIVENESS OF SELECTIVE COMMINUTION WILL BE EVALUATED FOR DEPENDENCE ON COAL TYPE. THE TOTAL AMOUNT OF ENERGY REQUIRED TO EFFECT SEPARATION OF MINERAL MATTER WILL BE DETERMINED AND COMPARED WITH CONVENTIONAL PRACTICES FOR ACHIEVING SIMILAR LEVELS OF COAL CLEANING.