Preparation and Characterization of the Glycerol-Embedded Hybrid Coal

Abstract

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.

Two-in-One Fuel Synthetic Bioethanol-Lignin from Lignocellulose with Sewage Sludge and Its Air Pollutants Reduction Effects

“…These characteristics can be confirmed indirectly from the DTG graph ( Figure 2). The combustion boundary of VM and FC changed broadly, and the complete combustion of FC proceeded [38]. CO and C x H y emissions and unburned carbon (UBC) are closely related.…”

“…These results are in good agreement with those of a previous study. According to Lee [41] and Park [38], biomass-impregnated fuels improve combustion responsiveness and reduce UBC emissions. Therefore, HSF with lignin would be beneficial for application in power plants from an environmental perspective in terms of particulate matter emission reduction.…”

Evidence of the illegitimacy of the additive approach to the determination of the thermophysical properties of coal‐water fuel with glycerol

“…In paper, 23 it is shown that the addition of glycerol directly to low‐grade coal leads to an improvement in combustion kinetics, a reduction in unburned carbon emissions by 35%, and an increase in the calorific value of such a composite fuel by 80%.…”