Ashless coal, also known as HyperCoal (HPC), was produced by thermal extraction of three coals of different ranks (Gregory caking coal, Warkworth steam coal, and Pasir subbituminous coal) with 1-methylnaphthalene (1-MN) at 360, 380, and 400 °C. The effects of blending these HPCs into standard coal blends were investigated. Blending HPCs as 5−10% of a standard blend (Kouryusho:Goonyella:K9) enhanced the thermoplasticity over a wide temperature range. For blends made with the Pasir-HPC, produced from a noncaking coal, increasing the extraction temperature from 360 to 400 °C increased the thermoplasticity significantly. Blends containing Warkworth-HPC, produced from a slightly caking coal, had a higher tensile strength than the standard blend in semicoke strength tests. The addition of 10% Pasir-HPC, extracted at 400 °C, increased the tensile strength of the semicokes to the same degree as those made with Gregory-HPC. Furthermore, all HPC blends had a higher tensile strength and smaller weight loss during carbonization. These results suggest that the HPC became integrated into the coke matrix, interacting strongly with the other raw coals.

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Generating power from HyperCoal is a high-efficiency process in which the organic portion of coal is extracted with industrial solvents at a temperature around 360°C and fed to a gas turbine directly. This study sought to establish a selection index for identifying subbituminous coals that give high extraction yields. Subbituminous coals were extracted at 360°C with flowing industrial solvents, and we investigated the relationship between the extraction yield and the quantity of oxygen-containing functional groups in the coal. The extraction yield with a polar solvent, crude methylnaphthalene oil (CMNO), increased with the quantity of carboxylate groups bridged by metal cations, such as Ca 2+ and Mg 2+ (COOM). The correlation coefficient between the extraction yield and the quantity was 0.82. Acid treatment of coal before extraction released COOM cross-links, increasing the extraction yield. These results suggest that the thermal extraction of lowrank coals strongly depends on the cross-links rather than the hydrogen bonds. Therefore, the thermal extraction yields of low-rank coals can be estimated from the quantity of COOM in the original coals. The intercept of the regression line between the quantity of COOM and the extraction yield with CMNO was 57.8%. This value is the average extraction yield for low-rank coals with free COOM.

The molecular interactions between asphaltenes and solvents are an important parameter that dominates the processing behavior of asphaltenes. This study has developed a method for estimating the interaction energy of asphaltene (or resin) aggregates with aromatic solvent molecules. The thermal properties of three asphaltenes and one resin have been ascertained using differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA), and the heats of solution (∆H solu ) of the two species in quinoline, 1-methyl naphthalene (1-MN), and tetralin have been established using microcalorimetry. By combining the two techniques, the heat of mixing (∆H mix ) of the asphaltene or the resin with the solvents could be estimated. This not only evaluates the nature of interactions between asphaltene (or resin) aggregates and solvent but also provides a quantitative estimate of their magnitude.

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