Completed Research
Development of a Selective Agglomeration Process Using Light Hydrocarbons for Fine Coal Beneficiation
Seong Soo Kim, PhD, 1993
(Abstract: UMI Dissertation Publishing)
Selective agglomeration is a coal beneficiation process which relies on the difference between the wettability of coal and that of undesirable mineral matter including pyrite by an agglomerant. The objective of this study was to develop an advanced selective agglomeration process for fine coal cleaning using a light hydrocarbon as agglomerant which could achieve 85% ash and inorganic sulfur rejections at 85% Btu recovery. In order to achieve the objective, screening experiments were conducted and the results led to the selection of the most important operating variables affecting the process performances. The important variables were agglomerant/coal weight ratio, grinding time (particle size), slurry pH, and agglomeration time. The effects of these variables on the process performances were statistically investigated using ultrafine Upper Freeport, Pittsburgh #8, Illinois #6, and Kentucky #9 coals. As agglomerant, n-heptane was used for Upper Freeport and Pittsburgh #8 coals and a mixture of n-heptane and a small amount of No.6 fuel oil was used for Illinois #6 and Kentucky #9 coals. The experimental conditions were selected according to a central composite design with all coded points at the same distance from the center. The experimental results were modeled using statistical models which consisted of quadratic equations and inverse terms. The analyses of the response surfaces constructed using the regression models showed that the Btu recovery for the four coals reached a maximum value close to 95-99% at agglomerant/coal weight ratio of 0.3. It was also shown that the increase of slurry pH increased the ash and inorganic sulfur rejections for Upper Freeport, Pittsburgh #8, and Illinois #6 coals. However, the ash and inorganic sulfur rejections for Kentucky #9 coal were not significantly affected by the slurry pH. This study demonstrated that for the four coals used, a Btu recovery as high as 95-99% and ash/inorganic sulfur rejections as high as 82% were possible within the experimental conditions used. The results obtained in this study could serve as a basis for further development of advanced selective agglomeration processes.