Preparation and Characterization of the Glycerol-Embedded Hybrid Coal

Ju Hyoung Park, Dong Wook Lee, Young Joo Lee, Gyu Seob Song, Min Ho Jin, Se Joon Park, Hueon Namkung, Jong Soo Bae, Joeng Geun Kim, Kwang Ho Song, Jong Won Choi, Young Chan Choi

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


The molasses embedded hybrid coal (Hybrid Coal by Korea Institute of Energy Research; HCK) was previously proposed as an attractive alternative to low-rank coals that tend to show low calorific values and high CO2 emissions. HCK was synthesized by mixing molasses with a low-rank coal to enhance its heating value. Nevertheless, food ethics regarding molasses additives still have impeded its commercial acceptance. In this study, we propose a glycerol (nonfood)-based coal upgrading process to improve the combustion kinetics and heating value of hybrid coal in comparison to the previous HCK. The process involves drying at 105 °C followed by torrefaction process at 250 °C. During torrefaction, the glycerol additive starts to evaporate at about 180 °C and then is almost vaporized out to the coal surface. To avoid glycerol loss, we employ sulfuric acid as a torrefaction catalyst to suppress glycerol evaporation. In comparison to the molasses yield of 65% after torrefaction in the previous HCK synthesis process, glycerol-embedded torrefaction with sulfuric acid showed a 55% yield in mass. The glycerol-embedded hybrid coal shows a homogeneous combustion peak regardless of the mixing ratios, leading to a 35% reduction of unburned carbon emissions, which is one of the particular matter sources of combustion flue gas. Furthermore, the proposed synthesis process increases the net caloric value to 80% and lowers the water uptake to 84%, even without a higher SO2 emission, in comparison with raw coal.

Original languageEnglish
Pages (from-to)4637-4646
Number of pages10
JournalACS Sustainable Chemistry and Engineering
Issue number5
Publication statusPublished - 2019 Mar 4


  • Coal upgrade
  • Glycerol
  • Hybrid coal
  • Sulfuric acid
  • Torrefaction
  • Unburned carbon

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry
  • Chemical Engineering(all)
  • Renewable Energy, Sustainability and the Environment


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