Coal Chemistry and Morphology of Thar Reserves,Pakistan

Abstract

The surface of Thar coal has been characterized by spectroscopic, microscopic and chemical methods using atomic absorption spectroscopy, fourier transform infrared analysis, X-ray diffraction, scanned electron microscopy and pH titration. The samples contained high moisture, low volatile and low to moderate sulfur content and ranked as lignite (heating value 2541-4289 kcal/kg on moist, mineral-matter-free basis). Scanned electron micrographs show porous matrix with calcium, potassium or sodium minerals. Fourier transform infrared analysis also confirmed the presence of aluminum, silica and hydrate mineral constituents. The spectra showed C=C aromatic groups at 1604-1609 cm-1. Phenolic ester and carboxylic acid are identified by C=O stretching vibration peaks at 1702 cm-1. The peaks of quartz and kaolinite were observed at 900-1100 cm-1. Point of zero charge of Thar coal has been estimated as 6.00 to 6.27 through adsorption of H + and OHions by suspending coal particles in aqueous electrolyte solution. Oxygen containing functional groups, mineral matter, and metal oxides are found to have a remarkable impact on point of zero charge. The surface characterization study will be helpful in the separation of hydrophilic impurities during coal preparation processes considering pzc as the controlling factor.

Influence of surface chemistry on interfacial properties of low to high rank coal seams

“…The salt content for achieving a zero charge as reported here is also of important consideration for processes that involve colloidal dispersion and coagulation [35], e.g. in coal processing [42].…”

“…The band at ~2900 cm -1 observed for low rank coal is due to the presence of aliphatic C-H stretching vibrations [36]; however, its absence in high rank coal is unusual and is perhaps due to C-H stretching where the carbon is in a C=C bond. Moreover, the sharp band observed at 1500-1800 cm -1 for low rank coal is attributed to aromatic ring vibrations, which are enhanced by oxygen groups [35]. The corresponding shoulder peaks at 1600 cm -1 is attributed to C=O stretching vibrations and these represent all C=O functionalities, e.g.…”

“…Physically, the coal surface exhibits negative charges due to the presence of polar functional entities, which partially dissociate, e.g. carboxylic or phenolic groups [35]; the concentration of these functional groups depends on the coal rank ( [36] see also FTIR discussion in Section 3.5). The results found here are consistent with Ibrahim and Nasr-El-Din [37] who reported that both zeta potentials and contact angles on coals increased with salinity.…”

Solid/CO 2 and solid/water interfacial tensions as a function of pressure, temperature, salinity and mineral type: Implications for CO 2 -wettability and CO 2 geo-storage

“…Moreover, the sharp band observed at 1500-1800 cm -1 for low and medium rank coal is attributed to aromatic ring vibrations, which are enhanced by oxygen groups (Sarwar et al, 2012). The corresponding shoulder peaks at 1600 cm -1 for low and medium rank coals is attributed to C=O stretching vibrations and these represent all C=O functionalities, e.g.…”

Conversion of Coal-Biomass into Diesel by Using Aspen Plus

“…This model simulates the production of bituminous and lignite coal. The lignite coal data utilized in the model come from the Thar coal literature [32], whereas the coal feed analysis and operating conditions for bituminous coal are from Wen et al The reactions of devolatilization and pyrolysis were investigated because they can be used to transform coal into gaseous products at high temperatures. Chemisorption reactions were investigated for the removal of CO 2 and H 2 S. Twenty phases were chosen to reach the permitted limitations.…”