Low grade bunker fuel brings about evaporative and surface combustions, and produces unburned carbon easily because the fuel itself contains residue.
The present experiment attached importance to this fact and clarified combustion characteristics of the low grade bunker fuel by thermal analyses. Samples for low grade bunker fuel were fuel oil C and compositions separated from the oil by column chromatography; and those for middle distillate fuel were gas oil and marine diesel fuel. The results of the experiment were as follows:
(1) When the samples for low grade bunker fuel were heated, thermogravimetric analysis measured a loss in weight of-evaporation, thermal cracking and combustion of carbon residue, and temperature region of the three. Differential thermal analysis measured combustion point and heat of reaction through the heat of the samples mentioned above.
(2) Saturated hydrocarbon in the fuel oil C was almost evaporated, and the combustion point is lower than that of other compositions. Most of both Aromatic hydrocarbon and Resin changed into carbon residue by thermal cracking. This process was facilitated by oxygen in the air.
(3) The Aromatic hydrocarbon composition of used fuel raised the temperatures of combustion and thermal cracking, and changed into carbon residue easily. The complete combustion of the composition required more than 497°C of ambient air.
(4) Combustion profile seen in blend of low grade bunker fuel and middle distillate fuel showed a shape combining the outlines of the two materials, if a region of boiling point was very different among both.
