Chemical cleaning of Slovak brown coal by GACL (Grinding and Aqueous Caustic Leaching)
- Slovak Academy of Sciences, Kosice (Slovakia). Inst. of Geotechnics
- Dept. of Energy, Pittsburgh, PA (United States). Federal Energy Technology Center
- Virolac Industries, Waynesburg, PA (United States)
The desulfuration of coal by chemical methods is accomplished by different reagents of acid or alkaline character. The study of the processes applying hot alkaline solutions to purification of coal is not a recent development. As early as during the second World War this process was used in Germany on purpose to prepare from coal a low-ash product suited to production of electrode carbon. It has been stated in a paper published by U.S. Bureau of Mines that one can reduce the content of ash in coal from original 98% to 0.7% by using 10% NaOH at increased pressure and temperature of 225 C. The application of NaOH solutions at increased temperatures (150--250 C) and pressures (0.6--2.5 MPa) were investigated in several laboratories. Another possibility of using alkaline medium for cleaning of coal involves atmospheric pressure. Molten NaOH (or its mixture with KOH) is used and the effective temperature is about 400 C. The ability of molten NaOH to desulfurate coal has been known for more than three decades. The liberation of the pyritic sulfur starts at temperatures above 150 C while the organic sulfur is released from the coal matrix at temperatures above 200 C. The process known as MCL (Molten Caustic Leaching) was for the first time tested by TRW in cooperation with US Department of Energy in the Seventies. The objective was to remove mineral components, pyritic and organic sulfur by using the reaction of coal with a mixture of molten sodium and potassium hydroxide. For leaching time of 60--180 min and temperatures of 370--400 C the effectiveness of MCL process of removal of individual components was as follows: 90--95% of pyritic sulfur, 70--90% of organic sulfur and 90--99% of ash. The MCL process was also effectively applied for treatment of Slovak brown coal in previous work. Because of the presence of sulfidic admixtures in coal and the fact that organic sulfur is built in the matrix of coal and from the view-point of chemical cleaning also exhibits refractory character, the possibility of verifying the principle of such pretreatment offers itself for coal as well. The aim of this work is to apply the new GACL process (Grinding and Aqueous Caustic Leaching) to brown coal Novaky, and to determine how effectively this process lowers ash, sulfur and arsenic levels.
- OSTI ID:
- 349183
- Report Number(s):
- CONF-980985-; ISBN 1-890977-15-2; TRN: IM9924%%183
- Resource Relation:
- Conference: 15. annual international Pittsburgh coal conference, Pittsburgh, PA (United States), 14-18 Sep 1998; Other Information: PBD: 1998; Related Information: Is Part Of Fifteenth annual international Pittsburgh coal conference: Proceedings; PB: [1500] p.
- Country of Publication:
- United States
- Language:
- English
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