Aqueous Leaching on High Sulfur Sub-bituminous Coals, in Assam, India
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- 作者：Bimala P. Baruah ; Binoy K. Saikia ; Prabhat Kotoky ; and P. Gangadhar Rao
- 刊名：Energy & Fuels
- 出版年：2006
- 出版时间：July 2006
- 年：2006
- 卷：20
- 期：4
- 页码：1550 - 1555
- 全文大小：60K
- 年卷期：v.20,no.4(July 2006)
- ISSN：1520-5029
文摘
Aqueous leaching of high sulfur sub-bituminous coals from Ledo and Baragolai collieries of Makum coalfields, in Assam, India, has been investigated with respect to time at different temperatures. Leaching at 25 
Cup to 120 h showed that the physicochemical characteristics viz., conductivity, acidity, TDS, and SO4-2 ions,increase with the increase in time of leaching. The generation of highly acidic leachates at 1-1.5 h (pH 2.5)and 2 h (pH 3.1) for Ledo and Baragolai coals was observed, respectively. However, it remains stable up to120 h. The concentration of major, minor, and trace elements and their mobility along with the loss of pyriticsulfur or depyritization were also reported. The release of metals (Fe, Mg, Bi, Al, V, Cu, Cd, Ni, Pb, and Mn)above the regulatory levels during leaching was evidenced. Depyritization was found to be 79.8, 82.9, 84.7,and 89.7% for Ledo and 70.49, 73.77, 75.41, and 77.05% for Baragolai coal at 15, 25, 35, and 45 C, respectively.A pseudo-first-order kinetic relationship with activation energies (E) of 8.1477 and 5.2378 kJ mol-1 withfrequency factors (A) of 8.8405 × 10-4 and 2.6494 × 10-4 dm3 mol-1 s-1 was attributed to aqueous oxidationof pyrites in Ledo and Baragolai coals, respectively. The X-ray diffraction analysis and Fourier transforminfrared spectroscopy patterns indicate the presence of illite, 
-quartz, hematite, chlorite, rutile, calcite, andalbite as mineral phases. This investigation justifies the formation of acid mine drainage by weathering ofpyrites from coal during the mining of high sulfur Makum coal fields, in Assam, India, and demonstrates oneof the possible routes for its formation.
Cup to 120 h showed that the physicochemical characteristics viz., conductivity, acidity, TDS, and SO4-2 ions,increase with the increase in time of leaching. The generation of highly acidic leachates at 1-1.5 h (pH 2.5)and 2 h (pH 3.1) for Ledo and Baragolai coals was observed, respectively. However, it remains stable up to120 h. The concentration of major, minor, and trace elements and their mobility along with the loss of pyriticsulfur or depyritization were also reported. The release of metals (Fe, Mg, Bi, Al, V, Cu, Cd, Ni, Pb, and Mn)above the regulatory levels during leaching was evidenced. Depyritization was found to be 79.8, 82.9, 84.7,and 89.7% for Ledo and 70.49, 73.77, 75.41, and 77.05% for Baragolai coal at 15, 25, 35, and 45 C, respectively.A pseudo-first-order kinetic relationship with activation energies (E) of 8.1477 and 5.2378 kJ mol-1 withfrequency factors (A) of 8.8405 × 10-4 and 2.6494 × 10-4 dm3 mol-1 s-1 was attributed to aqueous oxidationof pyrites in Ledo and Baragolai coals, respectively. The X-ray diffraction analysis and Fourier transforminfrared spectroscopy patterns indicate the presence of illite, -quartz, hematite, chlorite, rutile, calcite, andalbite as mineral phases. This investigation justifies the formation of acid mine drainage by weathering ofpyrites from coal during the mining of high sulfur Makum coal fields, in Assam, India, and demonstrates oneof the possible routes for its formation.