Developing/Modifying Coal Grinding Procedures Predictable Size Distributions During Coal Preparation.

摘要

The beneficiation and utilization of coal requires that the mined coal undergo progressive degrees of size reduction. The size reduction process actually starts with the mining of the coal. The top size of the mined coal is very dependent upon the type of mining system employed. The mined coal undergoes primary breakage where the top size is reduced to the range of 8''to 3''. Either during the processing of the mined coal or usually before the utilization of the coal,the coal undergoes secondary crushing where the top size is reduced to the range of 2''to 1 1/4''. The coal may simultaneously undergo sizing in order to produce special marketable fractions. For final utilization as well as in some of the newer beneficiation techniques,the top size must be further reduced. Then the coal undergoes pulverization which reduces the top size to 1/8''and/or grinding which reduces the top size to 1mm or less. Some of the devices employed to achieve the desired size reduction,such as rotary breakers,roll crushers,hammer mills and impactors can be utilized in several segments of the coal size reduction spectrum. It is the grinding portion of the coal size reduction spectrum that this research contract is investigating. The equations of comminution are coupled with material balance equations,time of grind expressions and classification models to simulate the operation of a closed grinding circuit. When this is done to produce size distributions with the same common control point; e.g.,all curves pass through the 80% passing value at the same size,several circuit responses are observed which are of direct interest to this research effort. (ERA citation 04:025324)