| Abstract |
The concept of coal beneficiation due to particle segregation in water-fluidized beds, and its improvement via selective solvent-swelling of organic material-rich coal particles, was investigated in this study. Particle size distributions and their behavior were determined using image analysis techniques, and beneficiation effects were explored via measurements of the ash content of segregated particle samples collected from different height locations in a 5 cm diameter liquid-fluidized bed column (LFBC). Both acetone and phenol were found to be effective swelling agents for both Kentucky No.9 and Illinois No.6 coals, considerably increasing mean particle diameters, and shifting particle size distributions to larger sizes. Acetone was a somewhat more effective swelling solvent than phenol. The use of phenol was investigated, however, to demonstrate that low cost, waste solvents can be effective as well. For unswollen coal particles, the trend of increasing particle size from top to bottom in the LFBC was observed in all cases. Since the organic matter in the coal tends to concentrate in the smaller particles, the larger particles are typically denser. Consequently, the LFBC naturally tends to separate coal particles according to mineral matter content, both due to density and size. The data for small (40-100 (micro)m), solvent-swollen particles clearly showed improved beneficiation with respect to segregation in the water-fluidized bed than was achieved with the corresponding unswollen particles. This size range is quite similar to that used in pulverized coal combustion. The original process concept was amply demonstrated in this project. Additional work remains to be done, however, in order to develop this concept into a full-scale process. |
