Influences of Calcium Oxide Content in Marine Fuel Oil on Emission Characteristics of Marine Furnaces Under Varying Humidity and Temperature of the Inlet Air

Abstract

A marine furnace made of stainless steel, combined with an automatic small-size oil-fired burner, was used to experimentally investigate the influences of calcium oxide content in fuel oil on the combustion and emission characteristics under varying temperatures and humidity of the inlet air. Marine fuel oil generally contains various extents of metallic oxides such as CaO, Fe₂O₃, V₂O₅, etc which might affect its burning properties. In this study, an air-conditioner was used to adjust the humidity and temperatures of the inlet air to preset values prior to entering the burner. The adjusted inlet air atomized the marine diesel oil A containing a calcium oxide compound, to form a heterogeneous reactant mixture. The reactant mixture was thereafter ignited by a high-voltage electrode in the burner and burned within the marine furnace. The probes of a gas analyzer, H₂S analyzer and a K-type thermocouple were inserted into the radial positions of the furnace through the eight rectangular slots which were cut in the upper side of the furnace. The experimental results showed that an increase of either humidity or temperature of the inlet air caused the promotion of the reaction rate of the fuel. The existence of calcium oxide compound in the diesel fuel also facilitated the oxidation reaction in the combustion chamber. The addition of CaO in the diesel fuel under the conditions of higher temperature or higher relative humidity of the inlet air produced the following: higher concentrations of CO₂, SO₂, and H₂S emissions, an increased burning efficiency, a lowered O₂ level, production of excess air and NOx emissions as well as a lower thermal loss and a lower burning gas temperature, as compared with the conditions of a lower temperature or a lower humidity of the inlet air. In addition, the burning of diesel fuel with added CaO compound caused a large variation in the burning efficiency, thermal loss, plus CO₂, O₂, and excess air emissions between the conditions of higher temperature/higher humidity and lower temperature/lower humidity inlet air compared with no CaO addition in the fuel. Moreover, the burning efficiency and the concentrations of excess air and O₂ emissions increased, while the thermal loss, burning gas temperature and H₂S, SO₂, NOx, and CO₂ emissions decreased with the increase of the axial distance from the measured location to the burner nozzle.

Keywords:

• Combustion and emission characteristics
• Calcium oxide compound
• Marine furnaces
• Air humidity and air temperature
• Diesel fuel

Acknowledgment

This study received financial support from the National Science Council of Taiwan, ROC, under Project Contract No. NSC 85-2212-E-019-001 is acknowledged.