The outline of coal preparation and Economics of Coal CleaningAbstractCoal preparation, simply put, is the conversion of run-of-mine (ROM) coal (or coal as it leaves the mine complete with impurities and prior to any processing) into a marketable product. Originally, coal preparation began as a line of equipment-crushers, feeders, screens, etc.-to control the size of the mined coal. Perhaps the easiest way to understand the evolution of coal cleaning and to understand the evolution of coal cleaning and to understand the variations found within the industry is to become familiar with the levels of coal preparation.Level 0 processing is the mining and shipping of ROM coal.The product of Level 1 processing is commonly termed raw coal.Level 2 processing involves the cleaning of the coarser sizes of raw coal (or coal which is larger than 1/2”).The coal finer than 1/2” would be added to the cleaned coal (the plus 1/2mm coal) or sent elsewhere.Level 3 processing extends the cleaning of the raw coal to the intermediate size raw coal-1/2” by 1/2mm.The minus 1/2mm material is added to the cleaned coal (the plus 1/2mm coal) or sent elsewhere.Level 4 processing extends the cleaning to include the minus 1/2mm raw coal.The feed to the coal preparation plant is then raw coal from Level 1 processing. Coals impurities are numerous, but by far the largest have specific weights greater than coal. The raw coal is thus characterized by partitioning the very heterogeneous coal into relatively homogeneous subpopulations on the basis of size and specific gravity.The separation unit operations normally process water/raw coal slurries, thus the term Coal Washing. Coal preparation is the quality control arm of the coal industry. It is an integral part of the coal business. 2. The Cumulative Float Curve-a plot of the cumulative float weight percent versus the cumulative float ash percent.The outline of coal preparationCoal preparation, simply put, is the conversion of run-of-mine (ROM) coal (or coal as it leaves the mine complete with impurities and prior to any processing) into a marketable product. (A quality-controlled substance whose composition meets the ever-increasing specifications required for its use whether its combustion, liquefaction, gasification or carbonization.)The coal we mine today represents the deposition of phytogenic material 50 to 350 million years ago. The resulting horizontal strata, what we call coal seams, will vary in thickness from several inches to several hundred feet. They are usually separated by varying thicknesses of sedimentary rocks such as shales, clays, sandstones and, sometimes, even limestone, OR-when combined with coal-what are known as impurities in terms of preparation.Originally, coal preparation began as a line of equipment-crushers, feeders, screens, etc.-to control the size of the mined coal. Among the product line was the conveying picking table which was used to visually inspect the ROM coal so that obvious impurities could be removed manually. Thousands of men, women and children performed this unfulfilling work until mechanization replaced it withmore modern coal cleaning equipment.Generally speaking, this coal cleaning equipment was developed for British and European mines because their coal was of much greater value per ton than in the U.S. Its value reflected its cost of mining-which was high because the seams were more difficult to mine compared with American coal seams.However, although U.S. seams are among the easiest in the world to mine, preparation took on a new significance with the unionization of mines during the New Deal. A rapidly rising demand for machines to mine coal both underground and above ground was created; machines which were not and are not selective and which mine whole seams, including partings and some roof and floor mater ials.Mechanical mining meant mechanical cleaning.Perhaps the easiest way to understand the evolution of coal cleaning and to understand the evolution of coal cleaning and to understand the variations found within the industry is to become familiar with the levels of coal preparation.Each level is indicative of the intensity of the work performed on run-of-mine coal and each is an extension of the previous level.Level 0 processing is the mining and shipping of ROM coal.Level 1 processing combines top-size control by crushing, with some removal of undesirable constituents such as tramp iron, timber and perhaps strong rocks. The product of Level 1 processing is commonly termed raw coal.Level 2 processing involves the cleaning of the coarser sizes of raw coal (or coal which is larger than 1/2”).The coal finer than 1/2” would be added to the cleaned coal (the plus 1/2mm coal) or sent elsewhere.Level 3 processing extends the cleaning of the raw coal to the intermediate size raw coal-1/2” by 1/2mm.The minus 1/2mm material is added to the cleaned coal (the plus 1/2mm coal) or sent elsewhere.