Physicochemical Enhancement of Low-Rank Coal via Low-Temperature Co-Torrefaction with Coconut Shell Charcoal

Arif Algifari, Fitri Nauli, Syari Rahma Yanti, Heri Prabowo, Jonrinaldi Jonrinaldi

Abstract

This research investigates physicochemical and structural upgrading of Indonesian low-rank coal through low-temperature co-torrefaction with coconut shell charcoal. Coal-char mixtures containing 5, 25, and 45 wt% coconut shell charcoal were co-torrefied at 200 °C and characterized by thermogravimetric proximate analysis, bomb calorimetry, and X-ray diffraction (XRD). Linear regression was analyzed to evaluate relationships between coconut shell charcoal content and proximate properties. Increasing the charcoal fraction reduced the moisture content from 30.06% in raw lignite to 8.46% at 45 wt% charcoal and fixed carbon increased from 27.69% to 59.94%. Fixed carbon showed a strong positive relationship with charcoal content with R² = 0.9249, while volatile matter decreased with increasing charcoal addition with R² = 0.9161. The calorific value increased from 4823.46 to 6786.28 kcal/kg, demonstrating substantial energy upgrading. XRD patterns showed changes in the broad carbon-related diffraction features, indicating limited modification of the short-range structural ordering of the carbonaceous matrix after co-torrefaction. These research results show the potential of solid fuel for combining biomass charcoal as a renewable energy source with low-rank coal through low-temperature co-processing.

Keywords

coal-biomass co-torrefaction; coconut shell charcoal; energy densification; fixed carbon enrichment; low-rank coal.

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References

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DOI: https://doi.org/10.20961/alchemy.22.2.115659.407-415

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