No abstract

Many coal preparation plants in the United States continue to discard the minus 150 micron size fraction of their run-of-mine coal without any attempt to recover the clean coal content of this size fraction. This undesirable practice is partly caused by a variety of deficiencies with existing fine coal dewatering technologies, such as high moisture content of the product, loss of significant amounts of ultra-fine clean coal, high capital=operating costs, and operational unfriendliness. This study investigated the suitability of a newly developed fine particle dewatering technology, known as Steel Belt Filter (SBF), for dewatering both fine clean coal and fine tailings materials generated at coal preparation plants in the United States. The unique feature of this new technology is the combined use of mechanical pressure and suction force (vacuum), a combination which is known to provide excellent dewatering performance. A SBF prototype unit having a belt width of 0.6 m was tested at the Illinois Coal Development Park. A factorial experimental design using the response surface methodology was conducted to optimize the dewatering performance of the SBF prototype unit. Two different clean coal slurry samples having mean particle sizes of 400 micron and 50 micron and two fine coal tailings samples having mean particle sizes of 20 and 10 micron were dewatered using the SBF technology. A solid recovery of greater than 99% was achieved by using a suitable flocculant type and dosage for each sample. Surface moisture content of dewatered products varied from nearly 18.5% for coarser clean coal to 31% for finer clean coal and 18% for coarser tailings to 26% for finer tailings. A preliminary economic analysis conducted for a near-term commercialization of the SBF technology in the U.S. coal industry estimates the SBF dewatering cost for combined spiral þ flotation product to be $1.09=ton of dry coal.