Removal of sulfur and chlorine from Illinois coals by wet-grinding and selective flocculation
A coal-cleaning method for removing sulfur and chlorine from Illinois Basin coals was developed. The method includes four steps: (1) crushing raw coal to {minus}10 mesh, (2) using a concentrating table to remove pyrite and other minerals, (3) wet-grinding coal to an ultrafine particle size to liberate coal from pyrite and other minerals, and (4) conducting selective flocculation to separate coal from mineral particles and chlorine-containing water. A sample of Illinois Basin coal IBC-106 (9.0% ash and 3.77% sulfur) was ground to {minus}10 mesh and separated into five fractions on a concentrating table. The pyritic sulfur content decreased from 1.85% in feed coal to 1.49%, 0.85%, and 0.82% in clean, fine, and overflow fractions, respectively. Wet-grinding and selective flocculation tests were conducted on another sample of Illinois Basin coal IBC-105 (18.6% ash and 4.55% sulfur). The coal was ground in a stirred ball mill to generate a coal slurry with a particle size distribution of 90% <19 micrometer. The slurry was dispersed to make a complete suspension. Sodium metaphosphate was added as a dispersant. Various polymeric flocculants were tested to determine the selective flocculation performance of each. The acidity of the slurry (pH) and the flocculant dosage are critical in selective flocculation tests. When flocculant Calgon WCL-762 was used, the ash content decreased from 18.6% to 8.1% (56% reduction) in a single-stage flocculation process, and to 5.7% (69% reduction) in a two-stage process. Chlorine removal from coal was investigated on a high-chlorine coal sample IBC-109 (8.2% ash, 1.13% sulfur, and 0.42% chlorine). Wet-grinding the coal to 90% <20 micrometer, and subsequently dewatering the slurry by selective flocculation reduced the chlorine content from 0.42% to between 0.11% and 0.15% (64% to 74% reduction). In addition, ash content was reduced from 8.2% to between 4.0% and 5.4% (34% to 51% reduction) and pyritic sulfur content from 0.50% to between 0.21% and 0.26% (42% to 58% reduction) at 88% to 98% Btu recovery. Thus, a wet-grinding and selective flocculation method can effectively remove ash, pyritic sulfur and chlorine from a high-chlorine coal.
- Research Organization:
- Illinois State Geological Survey, Champaign, IL (US)
- OSTI ID:
- 20082364
- Resource Relation:
- Conference: Sixteenth Annual International Pittsburgh Coal Conference, Pittsburgh, PA (US), 10/11/1999--10/15/1999; Other Information: 1 CD-ROM. Operating systems required: Windows 95/98; Windows 3.X, Macintosh; PBD: 1999; Related Information: In: Sixteenth annual international Pittsburgh Coal Conference: Proceedings, [2000] pages.
- Country of Publication:
- United States
- Language:
- English
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