Surface physicochemical properties of semi-anthracitic coal from Painan-Sumatra during air oxidation

Abstract

Painan coals of West Sumatra were selected as semi-anthracitic coal sample for studying the physicochemical properties such as measurement, evaluation and description of the changes of surface characteristic of coal sample and their oxidation in the atmospheric air at a temperature ranging from 105 to 400°C for 30 min. Several methods are adopted to analyze and discuss several phenomena of the oxidized Painan coal surface during oxidation process for the change in the physicochemical properties as determined by Atomic Force Microscope (AFM), contact angle, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric and Differential Thermal Analysis (TG-DTA) analyses as well as other supporting analytical equipment. AFM analyses revealed some changes in adhesion force and surface morphology with more adhesion force available between 0.6 and 8.6 nN on polished coal surfaces due to the increased oxidation temperature. The study revealed that the extent of hydrophobicity of coal surface decreased with the increased of oxidation temperature expressed as contact angles at about 80°and 20°. Another phenomenon occurred during the experiment was hydrophilicity index of coal surface increase at approximately 1.3 and 2.9. Oxidation of coal that occurred with increased temperature also indicated an increase in oxygen content from 3.8% to 22.9 wt%. Increased oxygen functional group also noted that oxidation of coal took place during the treatment. We also found that oxidation treatment also affected the combustion properties of coal: decreasing ignition temperature between 452.9 and 317.6, lowering the reactivity of coal at maximum combustion rate temperature, and reflecting their char characteristics as burnt out, ranging from 652.3 to 648.5°C.

Characterization of bio-coal briquettes blended from low quality coal and biomass waste treated by Garant® bio-activator and its application for fuel combustion

“…The clay is also identified in the OH stretching absorption region, particularly in the band of 3670 cm -1 , distinguishing kaolinite in the raw coal (BB-Bayah and BB-Garut). This peak is somewhat diminished when it comes to the relative intensity at all the coal-biomass ratios; however, it can be observed in the FTIR spectrum of the raw coal, which is in agreement with the minerals identified by the XRD (Mursito et al 2014(Mursito et al , 2015(Mursito et al , 2018.…”

Unveiling the Changes in the Molecular Groups of Tight Sandstones in Response to an Electric Field

“…As to the reason behind the fact that the CH 2 groups and CH 3 groups show a downward trend with the effect of an electric field, a large amount of CH 3 groups and CH 2 groups can be evaporated through the cleavage form side chains of aliphatic hydrocarbons and bridge bonds as a result of the oxidation effect . Meanwhile, more CH 3 groups and CH 2 groups are altered to the oxygen-related molecular groups (CO groups, C–O groups, and COOH groups) under the action of oxygen substitution . Moreover, the hydroxyl groups react with the CH 3 groups and CH 2 groups to further produce the COOH groups (eqs and ), , which also consumes the amounts of aliphatic groups.…”

“…Thus, it is speculated that the aliphatic groups (CH 2 and CH 3 ) first transfer to C−O groups and then convert to CO groups under the oxidized circumstances. In addition, CO groups can be altered to COOH groups with the help of the oxidation effect, 68 which consumes the numbers of CO groups (eq 10). Thus, CO groups are also obtained by the CRPC.…”

“…53 Meanwhile, more CH 3 groups and CH 2 groups are altered to the oxygen-related molecular groups (CO groups, C−O groups, and COOH groups) under the action of oxygen substitution. 68 Moreover, the hydroxyl groups react with the CH 3 groups and CH 2 groups to further produce the COOH groups (eqs 11 and 12), 53,67 which also consumes the amounts of aliphatic groups. Thus, CC groups and aliphatic groups would be reduced under the influence of the electric field.…”

Types and Composition of Biomass in Biocoke Synthesis with the Coal Blending Method

“…The biomass s primary components and chemical structure were analyzed by Shimadzu Fourier-transform infrared spectroscopy (FTIR; IRTracer-100) using the ATR method, and JASCO IR Mentor Pro 6.5 software was used for spectral analysis. Other analytical methods were previously described with detailed operational techniques, and band assignments can be found elsewhere [26][27][28][29].…”