Sulfur bituminous coal samples

Table I. Bituminous Coal Samples and Their Pyritic Sulfur Content...

Two high-organic sulfur bituminous coals (IBC-107 and C-2) and one low organic sulfur bituminous coal (IBC-109) were selected as precursors to prepare the activated carbons. The IBC-107 and IBC-109 coals were obtained from Illinois Basin Coal Sample Program [30]. C-2 coal was directly mined from active Illinois coal basins. Samples were initially crushed to about 5 mm size particles and then pulverized (Holmes Model 500) and ground (Quaker City Model 4-E) to decrease the particle size to less than 1 mm. Samples were subsequently sieved with U.S. standard sieves (Tyler Standard Screen) to obtain -16 -i- 65 mesh (1.000-0.210 mm) samples. 

Two bituminous coals of moderate ash content were chosen for this paper to illustrate this method of determining coal-mineral association. The first sample was an Upper Freeport coal with 1.3% moisture, 9.88% ash, and 1.56% total sulfur. The second sample was an Indiana No. 3 coal having 10.5% moisture, 7.35% ash, and 4.26% total sulfur. Both coals had been precleaned at a coarse particle size, ground to minus 325 mesh (44 ym), and then separate samples were cleaned by float-sink and by froth flotation techniques, as described elsewhere [5]. Analyses of the feed coals are included in Table I. 

Many coals contain elemental sulfur. It is clearly a ubiquitous constituent of bituminous coals that have been exposed to the atmosphere. In contrast, three pristine samples obtained from the Premium Sample Program at the Argonne National Laboratory are free of elemental sulfur within the detection limit of four sensitive analytical methods. Exposure of the pristine coals to the atmosphere leads to the production of elemental sulfur. These observations strongly suggest that sulfur is not a natural constituent of coal, but rather is produced after exposure to the atmosphere by chemical or bacteriological action. 

Analytical Procedures. The samples of bituminous coals were analyzed for pyritic sulfur, sulfate sulfur and total sulfur using conventional wet chemical procedures adapted from the American Society of Testing Materials (23, 24). The ASTM D 3177-75, The Eschka method was used for the total sulfur, and ASTM D-2492-79was used for sulfate and pyritic sulfur determinations. The treated samples were filtered through a Whatman 2 filter paper to separate the coal particles from the liquid medium. The filtered sample was washed with 0.1 N HCl followed by distilled water to remove traces of absorbed sulfate and iron. 

Another slurry pipeline desulfurization experiment was conducted using Indiana 3 (Ayrshire) coal as a 25 wt% slurry in deionized water. The other process variables were carefully controlled flow rates 6-6.5 ft/sec, temperature 70-90°F, and pH 2.5 -2 8.The experiment was continued for 14 days, and the slurry samples for pyritic sulfur determination were taken daily. The desulfurization rates with Indiana 3 coal in the pipeline experiment are shown in Table 4 and are in good agreement with the laboratory data and the results with Illinois 6 coal. As observed in the laboratory experiments, the rate of desulfurization of bituminous coals is directly proportional to the pyritic sulfur content and inversely to the particle size of the coal sample. 

Coal is a naturally occurring combustible material consisting primarily of the element carbon. It also contains low percentages of solid, liquid, and gaseous hydrocarbons and/or other materials, such as compounds of nitrogen and sulfur. It is usually classified into subgroups known as anthracite, bituminous coal, subbituminous coal, and lignite. The physical, chemical, and other properties of coal vary considerably from sample to sample. 

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